Missinformation

[Burgerman]

https://www.youtube.com/watch?v=_533Uht8_1g

Theres so much wrong here that I dont know where to begin. This is why utube is a daft place to get information. Its all about money not facts.

Just to begin, almost all control systems inc PGDT stuff going back decades allows perfectly safe charging at 12A RMS. So no need to further reduce it to 8... I have been charging all my lead chairs at 12A and the correct voltages via the XLR ports going back 25 years!

2nd all batteries we use are capable of taking a 12A or greater charge rate than 12A never mind 10A. Even the small 22nf ones. Many quality ones have no current limit at all and actually recommend a high current charge with benefits in longevity and being able to get a more complete charge in the limited overnight periods we have available. Most AGM or Gel batteries state that 1/5th to 1/4 the rated capacity for charge rate in cyclic use is desirable. So on an 80Ah battery thats 20A. On a 40Ah 22nf that still 10A. And these are not detrimental - quite the opposite. I charge at anything from 50A downwards via the ANDERSON connectors. Regardless of battery type. Perfectly fine at the safe voltages.

As for charge "voltages" he is asking about then thats easy. All AGMs inc odyssey and every cheap brand too are great at 14.4 to 14.7V at room temperature. So choose 14.5V for best compatibility.
All pure gel batteries like MK and Sonnenschien etc last longest (best service life) at 14.1V per battery at the same room 20C room temperature. "Permobils" rebranded battery is an unknown and I dont have the specs but its probably going to be around 14.4V CV.

But THAT isnt the most important factor. It IS important. But so is the TIME it spends at CV. So the sooner a battery reaches its CV voltage and stays there the sooner the clock starts. So the initial CC stage (bulk) as its known matters only in that the CV stage is reaches sooner. More time to watch it gradually decrease naturally as it ABSORBES the charge. So more Amps always equals better. So in cyclic use you want it to remain at this elevated CV voltage until current naturally falls to around 1/500th to 1/1000th of its rated 20h capacity. This takes typically 7 to 9 hours on a GOOD battery in cyclic use. 5 hours as a top up of a stored battery. On an older one it may never get to this low current. So you must limit this to 7 to 9 hours at CV voltage maximum whichever occurs first.
At this point its 100% saturated and as much of the sulfates have been returned back to the electrolyte as is possible with a little damage as is possible. he result is a huge cycle life.

Charging at a few tenths higher results in plate corrosion, electrolyte loss over time. Less cycles. And on a gel battery higher impedance over time.
Charging a few tenths lower results in a much longer charge time which cannot be achieved in the 8 hours we have available overnight. So less capacity over time.
Charging for too long (beyond approx X hours at Constant Current + 8 hours at CV) causes positive grid corrosion. Electrolyte losses over time. Which reduces cycles and increases impedance.
Charging for too little time at CV or stopping charging while the current is still above around 750th of 20h capacity, or say 4 hours at CV results in the natural result of discharging (lead sulphate deposits) not being fully returned to the electrolyte and over time this results in irreversible larger crystals of lead sulfate coating the plates. So it critical that this is all correct. Because this is one of the main reasons batteries die sooner rather than later.

At least if you dont want limited range and new batteries every few months.

[slomobile]

Have you ever used these specific new Permobil Volt Pro batteries, or this specific new Permobil Volt Pro charger, or one of the PJSM with the melted port?

They have not a damn thing to do with PGDT from decades ago, or any other brand of battery you are familiar with. They are not the same things, even though they come in a somewhat similar shape to what you are used to. All 3 items the video references are made to Permobil specs. I do not know what they specified to the manufacturer and I suspect you don't either. If they want more watt hours stored, one potential way to do that is store it at a higher voltage. It is completely plausible that 12A at a slightly higher voltage all night long through contact resistance is enough energy to begin melting the trusty old XLR ports, causing more resistance, more heat, etc. It is also completely plausible that the manufacturer of PJSM tried to pull a fast one and substituted cheaper XLR ports on the joysticks they were making for Permobil while retaining the quality XLR ports for their own branded joysticks. Thus the recall. I cannot say these are facts, just speculation. If I stated my speculation as fact, as you have done, that would be "Missinformation".

The Volt Pro charger in question ships configured for 12A charging of Volt Pro batteries only. It is not intended to charge any other brand or type of battery in that configuration. The 8A mode is simply a compatibility alternative that is more appropriate than the Volt Pro setting for most other batteries. I don't think anyone was claiming it was optimum, or even adjustable. What you discovered with Odyssey batteries and some other charger is interesting, but immaterial to the video.

[Burgerman]

I see you know about as much as he does.

And the charger doesent do 12A charging it does 10...
And permobils branded joystick is made by PG and has the same recognisable 12A (not 10) capable yellow high quality socket with a screw in it as the CJSM2. The CHARGER was being shipped with a bad quality low current plug. So that caused heat. Thers also nothing special about permobils branded battery. Its just another lead brick much like the ones we have been updating with almost no gains left for hundred years and more. Its just a gel battery with a AGM seperator instead. A cross between the two. It is lead. And lead dioxide and lead sulfate powered. Just like every lead brick. Those chemicals and the rate of recombination are what determines the open circuit voltage and the alloweable charge voltage. Not the charger...


And all powerchairs have a 12A RMS rating as specified in the specs for all the newest and all the oldest systems from all the main manufacturers with only the cheap folding powerchair electronics like the all in one VSI. All the rest from about 1997 onwards are 12A RMS charge ready.
Many manufacrturers already do supply 10A chargers inc sunrise. I have 2. That too is nothing new. Its perfectly fine vto charge a small 22nf battery, at 10A and in fact beneficial. Do you know why?
Do you care?
You seem to believe their marketing nonsense.

[slomobile]

10A, not 12A. My bad, I watched the video when it came out and didn't rewatch before posting.
I know PJSM was manufactured by PG(or subcontractors) for Permobil. I knew they were replacing PJSM under warranty for the melted port, but not that the source of the heat was the charger side connector. Do you have a quotable primary source for that?

General improvements in lead bricks.
https://www.sciencedirect.com/science/a ... 7000000088

Speculation follows regarding possible motivation behind Volt Pro.
Current profiles of powerchairs are very well characterized given standardization on 120A Rnet. A small number of models using only 2 pole motors can be coerced into fairly uniform current profiles by OEM restricted programming. The peak current is strictly limited, as is the duration before foldback. Up to 10s Rnet, limited to 5s by Permobil programming. The amount of vibration in chairs from a single manufacturer using the same suspension parts between models can be well characterized. Expected battery lifetimes for power chairs can have a strict cutoff due to insurance replacements. Charge time is always overnight at a fairly consistent temperature. Rider weight is in a predictable range with specified maximum. The only big variable is daily depth of discharge, and that can be greatly influenced by the battery gauge. Lose a few bars, we slow down or find a place to park, effectively limiting DOD by range anxiety. Given all those well characterized knowns, there were battery optimizations possible with a branded battery and optimized charger.

Make the plates barely thick enough to just barely survive warranty period. Peak current output just barely enough to turn on carpet in a M5 with 330lb rider. Even if that isn't enough to turn 4 pole hammer motors on a bariatric chair. Optimize plate capacitance with high surface area carbon or calcium for denser surface charge and physical reinforcement on thinner plates closer together using AGM seperator to prevent shorting.
A little extra capacitance compared to battery Ah is a fart in a hurricane. But it puts a slightly denser charge(higher voltage) at the surface of the plate than the core. This is the effect we know as surface charge. Lead plates generally need to be at least thick enough to deliver instantaneous current. If you know exactly your max instantaneous current requirement, and exactly how much you have available in surface charge, you can thin the plates by a calculated amount and still barely meet spec. Remove less efficient core volume and make it more surface area in the same group size.
I'm guessing whatever plate surface treatment they used acts something like a doublelayer capacitor with ESR that needs to be overcome while charging. Thus the higher charge voltage.

[Burgerman]

Make the plates barely thick enough to just barely survive warranty period. Peak current output just barely enough to turn on carpet in a M5 with 330lb rider. Even if that isn't enough to turn 4 pole hammer motors on a bariatric chair. Optimize plate capacitance with high surface area carbon or calcium for denser surface charge and physical reinforcement on thinner plates closer together using AGM seperator to prevent shorting.
A little extra capacitance compared to battery Ah is a fart in a hurricane. But it puts a slightly denser charge(higher voltage) at the surface of the plate than the core. This is the effect we know as surface charge. Lead plates generally need to be at least thick enough to deliver instantaneous current. If you know exactly your max instantaneous current requirement, and exactly how much you have available in surface charge, you can thin the plates by a calculated amount and still barely meet spec. Remove less efficient core volume and make it more surface area in the same group size.
I'm guessing whatever plate surface treatment they used acts something like a doublelayer capacitor with ESR that needs to be overcome while charging. Thus the higher charge voltage.

None of this makes any sense to me. And I have been working with, selling, testing, and using them complete with plenty of hard won knowledge since the 80s.
Batteries are already highly optimised and none of the parameters you mention make sense. Because lower impedance is ALWAYS better regardless of current. That of course requires large surface area and so thin plates and a strong acid / water electrolyte. Those things are the exat opposit to whats required for large Ah capacity.

When it comes down to it lead batteries are a triangle, a formulae with (main) 3 parameter.

You need
LOW IMPEDANCE
HIGH CAPACITY
HIGH CYCLE LIFE
Its possible to increase any one (or even 2) of these things. At the expense of the other one (or two).
Battery manufacturers have been optimising these things, with different proportions of the above 3 things for a FIXED CASE VOLUME for a century.

Theres nothing new under the sun.
Its possible to buy say group 24 sized case batteries that excell at cycle life, with up to 700 or more 80% deep cycles. But they are gutless, High impedance means that voltages drop too low over time say climbing a hill. And my chair hasnt got the guts to wheelie. Not even once. There is no "just capable" parameter.
Its also possible to buy batteries that can do big currents (and so low impedance) like the Odyssey for e.g. But unlike a typical 500 to 550 cycle MK gel, the odyssey can only do 400 80% cycles. And it loses out a few Ah too.

So again you can have more of ione thing at the expense of the other two sides of the triangle. As for increased capacitance or surface charge, then that disapates under load instantly, its why we must measure battery resistance as a high frequency AC resistance. So thats a waste of time. You want LESS surface charge.
Do you actually know WHY lead batteries show this peukert or surface charge effect?

And...

Remove less efficient core volume and make it more surface area in the same group size

That results in LESS capacity, and low impedance. Thats EXACTLY why the ultimate battery has super thin plates, and pure lead with little to no pasted lead in the grids. This is why the best 2 lead batteries on the planet already exiSt for 50 years. Odyssey (TPPL = Thin Plate Pure Lead) and the less space optimised pure lead thin sheet optima batteries. BOTH do this. And they have strong acid, and because no impurities there is no "extra" reactions taking plkace destroying the plates.

For this reason Odyssey will start a truck in siberia, not sag after 35 wheelies in a chair, charge much faster, and is capable of 400 cycles at the same time. You can have low impedance and this costs you in cycle life and capacity. I would use these for sport, or personal use.A normal user will not be able to tell the difference.
The yellow optimas can do 500 cycles with the same thin plate pure lead but coiled up like an AA cell. But they lose in Ah (55 compared to the Odyssey 68. They are tightly wound with almost no electrolyte in their cores and have very low peukert. The MK is 74Ah, 500 cycles, but its got DOUBLE the impedance of the Odyssey. So at the loads that a powerchair needs actually perform around the same for range. Or better. But It FEELS like a flat battery even when fully charged to me.

Same 3 sided triangle...

[Burgerman]

Heres what we DO know about the "permobil" battery.
Its made to a good standard and the process is tracable to iso 9001.
At the 20 hour rate they are 85Ah. But this is at 25C rather than 20C so they are cheating a bit here and winning 3 to 4% and that is only if you discharge them down to 1.8V per cell. Thats 10.8V which is standard for the 20 hour rate. But your powerchair will not be able to do this. Why?

Well they claim to be 70Ah also at 25C at the 5 hour rate. So they display a pretty average peukert level. Worst than some, about the same as most good Gel batteries. But nothing special either. So far they have the same specs as the Eternity 80Ah and the 80Ah (at 20C) Haze gel grp 24. So again if you plotted these curves on a graph you would see practically nothing between them.

But thats not the full story as we do not discharge at a constant rate of 20 or 5 hours. We do so in huge spikes and chunks. During a heavy load such as a hill or a wheelie or when turning in place we take power at typically 1C or greater. At the 1 hour rate, the voltage of all of these may drop well below the voltage that the powerchair needs for control and it may even cut out of you do this for a few seconds or so.

A kinder way to examine this is to look at the typical range. Say a real world 15 to 20 miles. The chair is 7.5 miles per hour. So if you get up, and go out in a straight line at constant speed then you will cover your max range distance if 15 miles in 2 hours. Or 22.5 miles in 3 hours. But the chair will stop maybe long before this when it sees a hill/voltage drops...

So the 2 or 3 hour rate is more representitive. And doesent include spikes of 100A or so as you turn/curb climb etc. So a battery with less internal resistance such as a SMALLER Ah Odyssey may well allow you to have more range. Because Peukert and internal resistance (measured as AC impedance) are closely related.

What else do we know?
We know that the permobil batteries say 14.4 to 15 Volts on them. For cyclic charging. It doesent say at what point you stop either.
It also says that you should use a float value of 13.5 to 13.8V.
Now it says the same on the MK sell sheet and mobility dealer leafelets. Even though its WRONG!
And also on the Eternity and Haze gel batteries. Because that works. And its the industry standard charger figures. They want to sell batteries right? Thats also wrong. The gel battery tech sheets across the industry show a much greater cycle life when you stick to the max 14.1V at room temperature 20C.
What it DOESENT say is that carging above this costs you a lot of cycle life!
Although MK admt this very clearly in their TECHNICAL DATA SHEET that charging above 14.1V actually voids the warranty! It goes on to show many different graphs ov charge voltage and temperature and shows that ajust few tenths of a volt above the ideal 13.95V at room temperature costs you SIXTY PERCENT of cycle life...

And it does.

So as I say, "permobil" batteries have just the same charging profile needed as every other battery. And the same voltages printed on the battery.

[Burgerman]

THERE ARE 4 WAYS TO CHARGE A SEALED VALVE REGULATED RECOMBINANT BATTERY SUCH AS ALL THE ONES WE USE. THIS LIST REFERS TO GEL.
And Any battery using gelled electrolyte such as the permobil ones.
We dont know the max voltage allowed for those but it *may* be marginally higher than normal gels are as the AGM seperator material may help prevent bubbles causing voids. Or it may not. But either way this list will be safe for those too as the difference a different seperator material makes is going to be slight at best. Its biggest advantage is marketing. It helps sell "matched" chargers and batteries at great profit!


++++++++++++++++++++++++++++
3 STAGE GEL - FASTEST METHOD: I occasionally do this with the PL8.
IUI
Charging I = min. 12% C₅ max. 18% C₅
U = 2.35 V per cell @20 Centigrade.
I2 = 1.5 % C₅ for max. 4 hours
Recommended for fastest possible charge with some loss of cycle life. Intended for where there is limited time to recharge. This is not the kindest way. Because its impossible to know if there is under or overcharge and the elevated voltage at the last cc stage - even at low current can damage gel and cause grid corrosion. Used in thing like airport floor cleaner robots. Possibly our wheelchairs if in a hurry.

+++++++++++++++++++++++++++++
2 STAGE GEL - MEDIUM FAST and ACCURATE: if done carefully results in a more accurate complete charge without damage.
I USUALLY do this with the PL8. Can be done with the Shirley ZXD too.
IU
Charging I = min. 12% C₅ max. 18% C₅
U = 2.35 per cell at 20 Cent. Reduce if warmer like in summer.
This is the best way for overnight wheelchair charging. As far as I know there are no mobility chargers that do this.
KEEP GOING until either 8 HOURS max on the 2nd stage is reached or the battery current stops falling (by 100mA per hour) on a group 24 / 75Ah sized battery. Or reaches 1/750th of its 20h capacity. Takes around 9 or 10 hours.

++++++++++++++++++++++++++++++
3 STAGE SLOWEST CHARGE and what almost all current mobility chargers do. Worse they do it VERY inaccurately and at the wrong voltages.
IUU Charging I1 = min. 12% C₅ max. 18% C₅
U = 2.35 V per cell @20 Centigrade.
U = 2.25 V per cell @20 Centigrade indefinitely. Approx aditional 8 to 12 hours required to completely charge cell.
This method if done accurately, with correct voltages and a LOT OF TIME is the kindest way to charge a gel battery. But it takes 16 hours minumum to complete and often longer. Depending on how soon the 2nd stage ends. Most mobility charger end at around 1A which is too soon. But it reliably ends as some old sulfated batteries never get lower... And 2nd stage must be limited to 8 hours max. Total charge time around 16 to 20 hours. This is what mobility chargers generally do. At the wrong voltages for gel.

+++++++++++++++++++++++++++++++
I "STAGE" FLOAT CHARGE / STANDBY CHARGE (Any current level up to 1/4 battery capacity. Best limited to 1 to 2A for long term storage in case of thermal runaway)
13.80V Charge and short term storage up to 48 hours. Will take 48 hours to fully charge a battery. Too high for long term storage.
13.35V ideal for long term storage over a week to indefinitely. It keeps the battery healthy. Too low voltage to properly charge a discharged battery in under a month to 100%. But perfect for little to no deterioration in storage.

***you can also DSCONNECT battery cable. After charging overnight. And repeat every 30 to 60 days to store a powerchair battery.
Or charge overnight weekly to every ten days with battery connected.



ALL of the above are for 20C room temperature charging or storage.
If its warmer then voltages must be lower.
If its colder then voltages must be higher.
The exact amount needs to be taken from the battery specs. But most are pretty similar for gel.
See charts in next posts.

Now we dont know what the permobil charger is doing. If I get my hands on one I will test. Its probably better than the usual mobility charger? Or not. We cant tell yet. But whatever it does you can do without it if you have a decent charger.

[Burgerman]

3 stage charge graph (if the 2nd stage is 8 hours long or current no longer dropping the 3rd stage isnt needed for a complete charge.)

Temperature correction.

Damage to cycle life caused by being .7V above the ideal 13.95 volts at room temperature. Most mobility charger are all "universal/automatic" gel/AGM chargers. They are all 14.6V give or take, and do that even when its 30C and the battery is 40C... And you wonder why your gel batteries last a few months.

All these are from the MK Gel technical manual.

And yes these batteries are sold as 13.8v to 14.6V charge capable! But they omit to tell you what this does to them. Thats because they want to sell more batteries. And is TRUE you can charge them at 14.6V. If you dont care about how long they will last.

What IS important is that the voltage is not above the MAX allowed. Less is still OK. And MORE important is that they get fully 101% recharged. Because this returns the sulfates pack to the acid before it turns to permanant large never removable crystals. So this just takes time... Time is the issue.

[Burgerman]

Now you know why I worked for several advanced charger manufacturers as an advisor. And why I dispair when looking at videos like the one this thread and hundreds of others.

This only goes into a tiny fraction of what I do know about charging. And almost non of what I know about batteries. Esp lead.

The problem we have with all mobility charger is that they are almost universally crap. Not in that they are MADE badly. But in what they do and assume. Because wheelhair manufacturers know little to noting about batteries. Charger manufacturers and I know a good few are electronics and programming experts but clueless about batteries.

What we end up with is a load of chargers on the market that are all much the same that sort of clone each others ideas. Most claim to do as many "stages" as possible because thats great for marketing! Its a nonsense of curse, we only need 3. And really only need or want 2 for cyclic charging. The rest are pountless or actually harmful.

Then theres that word "auto". The charger will never be able to know battery size (capacity) or its chemistry or type. So auto really means you press go and it charges at the wrong voltages and stops or goes to the wrong float voltage (usually 13.8 which cooks batteries long term but aids in charging because the CV stage stopped way too soon.)
Most seem to aim (badly) at AGM batteries and because gels say "13.8 to 14.6" they seem to think that this is also gel compatible. Its really not!
And they are not accurate, stop too soon, and many are not temperature compensated so over volt even more in summer.

So the claim that the Permobil battery/charger does UP TO 20% more range may just mean that their battery has a higher Ah capacity. What batteries did they fit before? MK at 74Ah? And the claim that they last up to 60% longer is easy if the charger is doing this job better than most mobility junk chargers. But thats not because of innovation. Its because the rest of the chargers are really bad! I know this as I have measured a few.

Dont believe me?
This one was MEASURED voltage only. Measured by the PL8 set to "monitor". I didnt do this. A member here did.
This was actually charged using the good old invacare charger. The upright ones. Just for a laugh.

[Burgerman]

And no. Nobody can tell what its actually meant to be doing. But its voltage was all over. Thers 1 point at 2.2 hours where it got it right...
All the rest its voltage was too high, or too low. And it went doen to float level at 4.4 hours. This was wher it gave a green light! It will take a further 24 hours before this chair is actually charged AFTER the green... And it thought the battery was done! After 5 hours and a long days use. Its a joke.

Heres what it was TRYING to do.
This is a 2 stage CORRECT charge curve for a AGM Odyssey battery by my PL8. It graphs this as I charge the chair next to my bed:

[Burgerman]

And the Amps graph that matches the above.
Note that it naturally falls over time A LONG time! Took 10 hours total.
A 3rd stage isnt required if the accurate charge voltage (for odyssey in this case 14.7V) is maintained until current falls to 1000thC or 8 hours CV whichever is first.

Why did it take so long, remembering that this is a FORTY AMP charge via anderson conector? Peukert! 40A charge means bulk happens fast only. After this it drops away. More time then for the absorption/peukert to soak in. This is why its called absorption. The oddysey is the fastest charging lead battery available. Theres no way to speed this up. Other batteries take longer... This would have taken slightly longer at a lower initial current. Look at the graphs carefully. This is a PAIR of odyssey 68Ah batteries in parallel via anderson connectors. So they charge at 20A each. This is why I fit anderson charge connectors. I can but the bulk of a charge back fast and then go out at night safely while reducing the average daily depth of discharge. Makes the battery last way longer. Years more use.

This shows a 138Ah returned. Thats 2x 68Ah batteries in parallel. They were fully discharged. And fully 100% recharged in 9.5 hours. This is only possible with Odyssey low impedance batteries and a 40A accurate charger.

[jefferso]

I got a Permobil F5 which came with the "new" batteries and branded charger. I have a PL8 with a profile for MK gel, which is what is in my Permobil C500. Is that profile likely to work with the new Permobil batteries, or is 28.2v a bit low? Or maybe nobody really knows for sure since the internal specs remain something of a mystery?

[Burgerman]

Mystery?
No.
We KNOW that they state on the website that they are AGM/GEL hybrids. Like a few other brands. What that actually means is that they used a glass matt seperator between the plates so they dont short out instead of a multitude of of other possible materials. Is there any real advantage to this? Well it means that just like the typical AGM battery which does exactly the same thing, the glass mat (thin like bog roll, and made of glass fibres) absorbs the electrolyte.

Why? So that the acid water mix in a normal AGM cant spill. Or move about. Its strong so plates can be close together. Its a good seperator material. Is it any different electrically to any other battery? No as it takes no part in the reactions.

A gel battery is EXACTLY the same as a lead acid battery. Its just that the acid is immobilised by mixing it with silica gel crystals. So you can pour it on a tale and it stays around like vaseline or margerine. So no spill!

What you use as the seperator material doesent make any difference to the battery. Its electrically and chemically inert and its job is to keep the plates from touching.

Why do we charge a gel battery at a lower 14.1V at room temp? Because thats the borderline edge of where the electrolyte (water/acid mix) starts to gas and make bubbles. Gel doesent much like that. It doesent escape from the plates easily and forms voids if things go too far. And UNLIKE wet acid (or AGM batteries which use wet acid soaked into the glass mats) the acid cannot move around easily. Bubbles dont heal.

So you can safey charge an AGM battery at around 14.4 to 14.7V because the bubbles can move and the plate stays in contact with wet mobile acid. This also helps the oxgen and hydrogen recombine faster and at a higher rate.

You can BOIL a wet battery so its all bubbling away like crazy at 15V or more. The gas escapes, you add more water to replace the water lost.
An AGM battery cant be charged at 15V plus, but it can cope with a higher voltage than a gel battery.

All these batteries have lead plates. SOME have extra metals added for the purposes of making the plates stiffer. Mostly. In TINY quantities. And some just use non pure cheap lead. And that too stiffens the plates. But those different metals cause unwanted extra reactions that limit cycle life.

So if I were charging a permobil battery and had no specs to read up on, I would treat them as gel. Since they are. And that means that theres a bunch of ways to charge them and all of them need a lot of care and understanding! It says on them to charge at AGM type voltages. But thats also what MKs sell sheets say... But while this WILL charge them, its not good for them if you care.

[jeffery]

so my dealer swapped out my batteries while chair was in for service (without telling me) and they installed some MK's
since i didnt know, i continued to use my volt pro charger as per usual. within about 2 weeks, my batteries started loosing power by the evening, and within a few more days wouldn't even last 3 hours after unplugging form charger in the morning
back to the dealer! this is when i found out they had swapped my permobil batteries for mk's ive always used mks and they work well
regardless i bitched and had them put the permobil batteries back into my chair

i ran across the above video on the topic, and discovered the lack of info about the permobil agm batteries
grabbed my bluetooth multimemer and decided to track the voltages overnight with the volt pro charger. that sucker took the batteries all the way to up 31.9 volts!!
so almost 16 volts per battery! then after a while, it COMPLETELY cut off, no storage or trickle charging at all for the remaining 5 hours overnight

agm is agm and gel is gel, but there apparently is something slightly different going on here with these permobil agm batteries!

i popped the volt pro charger into 8 amp mode (per the video) and the next night it topped out at 29.4 volts.
and continued to trickle at 1.2a - 700ma till i unplugged it in the morning

i'd venture to say this charger is not simply more amps - but a super odd charging curve/voltage range
now i REALLY want to get my hands on some documentation for these batteries!
also explains why the mk batteries they stuck into my chair freaked out and died! over 15 volts is a baad idea

[Burgerman]

What the charger is doing is this.

Its a profile normally used where you have an AGM battery but can also be used on a gel battery (at a lower voltage) and has an accelerated end.

Works like this.
Theres 3 ways to charge cyclic deep cycle lead battery. Voltages are for 1 battery.

Method 1.
CC stage preferably at around 1/4 the battery Ah. Continue to the point where it reches the specified best cycle life voltage. Thats 14.1 for gel and around 14.7V for AGM maximum. Why maximum? Because lower takes too long. You can continue this and should continue this stage called CV (absorption) until battery reaches a low current typically 1000th C or 80mA on a 80Ah battery. Or 8 hours whichever occurs first. This is what I do with a normal bench power supply. I set it to say, 25A and 14.1V (28.2V) (gel) or 14.6V AGM. About 8 hours to 10 hours after it reaches this CV voltage I turn it off. At this point its drawing just 80mA. And is fully charged. This is the 2nd fastest way to achieve a full charge with some safety and accuracy in a short period.

Method 2.
This is what most cheap mobility chargers do because they try to charge safely albeit the wrong voltage for gel, but it takes 16 hours to 20 hours.
Set same voltages as above, Thats 14.1 for gel and around 14.7V for AGM maximum. Usually at 8A or 10A on most powerchairs. Better at 25A. But this needs anderson connectors. This then ENDS charge long befor the current during the CV stage has fallen to a low 1000thC (80mA) and long before the 8 hours of CV has occured. So this then drops to a lower CV voltage stage that SHOULD be 13.35V for long term storage, 13.6V for a charge completion where time isnt critical. But at least 16 hours. Or 13.8V where charge can be completed in a shorter 12 to 14 hours. But should not be left on charge more than a day.

Method 3.
What I think the permobil charger is doing. Charges at the normal AGM voltage as above. But ends very early when the current is still 1 to 2 Amps. Then charges at a CONSTANT CURRENT of 1 to 2 Amps for 1 hour or 2 hours. Without measuring I cant tell. But this method forces the last couple of Ah in at a low current faster than the natural slow float stage. The current is low enough that gassing is still not an issue and the battery can recombine it. This is normally used where the recharge time is too short for a normal charge. Like airport floor cleaners etc. So the voltage rises to around 32V at the end. It works. I do this sometimes with the PL8 too. As specified by MK. And Odyysey.

[Burgerman]

Reading matter...

MK charge specs. Note accelerated finishing...
www.wheelchairdriver.com/MK1.pdf

And also accelerated finishing for Odyssey
www.wheelchairdriver.com/odyssey.pdf

[jeffery]

im doing to do some more testing and will actually log the current as well
extrapolating from the amount of power the charger was pulling from the wall it lines up with blasting 10 amps all the way up to the same time as the multimeter log showed 31.9v on the first stage of charging
then it dropped off and continued on with its charging journey
there was one other point that it appeared to be pulling max power from the wall again later on for about 8-10min

but i want to verify all of that on the dc charger output side of things
looking at what was pulled form the mains was super odd compared to what im used to seeing from a typical agm charger

just seemed odd to me that any charger would regularly go over 15v per battery!

...also the fact that it broiled a brand new set of MK batteries within 2 weeks

[Burgerman]

Well it would. Gel is fragile.
Gassing causes voids and lead based batteries gas once the charge level is about 90% complete. And only do so at around 14.1V and above. They begin to gas a little at this point. The amount they gas depends on state of charge. They do it a little at first, and this increases as they become fuller. The amount they gas is also highly dependent on the CV voltage.

At float levels of voltage such as 13.4V theres literally none. And once FULL to 100% almost zero current flows. Maybe 2mA. Thats why its safe for long term / INDEFINITE storage. Keeps the battery healthy. At 13.6V float theres little to no gassing, but long term charging still causes grid corrosion at the positive plate because some small current is flowing even when 100% full. Its a good compromise to complete the charge in a sensible time frame. And up to a week on charge.

At the typical mobility float level of 13.8V some charging after the 2nd stage CV (that dummies call absorption) ends (far too early typically) is good to complete the charge in a relatively fast time but not healthy for longer than say a day or 2.

My guess is that the AGM grid which is like a thin glass fibre tissue used with the gel permobil batterynprevents the gel from getting pushed into voids and helps recombination work faster so they are charging them like a typical AGM.

So 10A up till around 14.7V.
Then a CV stage at this 14.7V for a fixed time/or wait till current falls naturally to around 2A.
Then again at a 2A constant current. (They cannot charge at 10A as the voltage would reach the point above your 31.x and that the battery would be severely damaged and would gas like a kettle!)

That is the typical accelerated finishing method.
As described many posts above somewhere.

If you did this to a MK gel, at 14.7V CV you would cause huge voids and the battery impedance would increase. So little current capability and big voltage drops under load. So while capacity may not be decreased very much if measured slowly it would be like you put a resistor in line with he battery leads. My impedance tester would show that the impedance was no longer a healthy 4mOhms.

Its important to understand that all the sealed battery are recombinant. And this is essential as they are sealed and should not gas. They do gas via a valve if the rcombination capacity is exceeded. Once almost full they electrically begin to split the water in the electrolyte to hydrogen and oxygen above a certain voltage.
Gel batteris have very immobile electrolyte and so are very limited at the rate this recombination can happen. So the CV voltage must be lower than AGM. Or voids and shrinkage though water loss occurs. AGMs have more mobile electrolyte. And so can still recombine these gasses back to water at higher voltages fast enough that no increase in pressure and no electrolyte loss happens. This also allows any bubbles that do happen to recover quickly as the wet acid just soaks back into the areas where bubbles formed via the glass mat seperator. So AGMs generally charge faster and better at higher CV voltages safely.

The rapid finish part allows the voltage to go higher. Up to 15.6V typically during a LIMITED CURRENT constant current 3rd stage. This puts the last 1 to 3% back fast! Instead of taking many hours. Its safe because it is done at a limited fixed constant current choosen to not exceed the battery recombination limits. And its for a short period. It allows a faster ending charge. Where you dont need to wait 6 hours to see the current tail off to almost zero on a float stage at a constant voltage as per normal. Max voltage cutoff is normally 15.2 or even 15.6V while doing this.

You CAN still add a normal float stage too after this point. And maybe they do.

[jeffery]

regardless it appears as tho the new permobil charger will damage mk batteries if the switch setting isnt changed
ill be able to do some current data logs this weekend when help is around

[Burgerman]

It will damage them if the switch IS changed too.

Because that just puts the charger into a generic one size fits all sealed battery gel/AGM mode. Probably. Like practically every mobility charger out there.

Of course it depends on your definition of damage.
Theres no way NOT to "damage" any lead based battery if you discharge it. That alone caused some deterioration. And charging using any lead battery method "works". So its all about degrees of damage. How to make a battery last as long as possible.

When charged under laboratory conditions, with the correct temperature compensated voltages and timings, while never discharging at a high rate, and never deeper than 80% depth of discharge, you can expect 500 cycles from your MK. At this point only 80% of the battery original capacity remains. You might well notice that its no longer capable for your day when 10% of its capacity has been lost. So at 450 cycles approx. Thats a year and a bit.

But we dont charge or discharge under idealised controlled conditions and we use mobility chargers that do not charge at the correct voltage and do not charge them for long enough resulting in 2 additional lifespan shortening issues. Maybe get just half of that idealised lifespan. So 250 cycles before we see a 20% decline. Or just 125 cycles before we see a 10% range reduction. Thats 4 to 9 months use...





How to make them last many years instead of months? If you understand batteries its easy.

_Use CORRECT charger algo for gel! Not a generic mobility charger.
_Charge at 20 to 25A via an anderson connector.
_Do half hour or longer top ups during the daytime whenever you get a chance as you eat or surf...
_FULLY charge for 24 to 48 hours each battery individually at float (or in parallel) at 13.6V BEFORE instalation.
_Dont discharge deeply. A few very heavy discharges does the same damage as maybe 100 shallow discharges.
_Dont use heavy rehab chairs! (these are typically 100KG extra or double the mass of a non rehab chair)
_Dont order the "high speed package". Batteries suffer horribly!
_Dont get any chair that cannot use full sized GRP24 or 75Ah (approx) batteries.

Do all of this and they will last you many years. Instead of months. 10x LONGER!
If you dont do these things then all the diffrent problems compound on each other. And the battery death acceleration is exponential.

[jeffery]

hmm.. there doesnt seem to be a reason to share anything further here

[Burgerman]

The only more things that could be useful are these:

1. The ACTUAL charge algo with and without being switched on that permobil charger. By which I mean CC level, CV stage (absorption voltage) and the legth of time and/or current hat it switches. And once its switched what exactly it does. Probably a CC stage at a fixed current for a fixed time. Or float. Or both. And the float evel if it does. So we know what good it is for both battery types in the future.

2. And the actual battery specs of the perobil rebrand battery. And technical best service life charge details. Such as are given for many other batteries as below. Well worth reading incidentally.

________________________
These are a good start for AGM and odyssey in this case but most AGMs are similar:
https://www.wheelchairdriver.com/odyssey.pdf

And Gels are all about the same as the MK specs:
https://www.wheelchairdriver.com/MK0.pdf Gel
https://www.wheelchairdriver.com/MK1.pdf Charge specs for long service life in cyclic or float use
https://www.wheelchairdriver.com/MK2.pdf MKs gel v AGM

https://www.wheelchairdriver.com/MK3.pdf IMPORTANT CHARGING INSTRUCTIONS: WARRANTY VOID IF OPENED OR IMPROPERLY CHARGED. Constant under or overcharging will damage any battery
and shorten its life! Use a good constant potential, voltage-regulated charger. For 12-volt batteries, charge to at least 13.8 volts but no more than 14.1 volts, at 68ºF (20ºC).
https://www.wheelchairdriver.com/MK4.pdf sell sheet? Cant remember!

[Burgerman]

From a good 3rd party website.

5 Battery Types Explained - Sealed, AGM, Gel
With all the different kinds of batteries on the market, it can be difficult to choose the right type for your application. We recommend that you take a few moments to find out more about the 5 most common types of batteries.

1. Flooded Batteries
This is the traditional engine start, tractor and deep cycle-style battery. The liquid electrolyte is free to move in the cell compartment. The user has access to the individual cells and can add distilled water as the battery dries out. Popular uses are engine starting and deep cycle designs.

For this type of battery the typical absorption voltage range 14.4 to 14.9 volts; typical float voltage range 13.1 to 13.4 volts.

Flooded batteries are common and found in many applications, such as automotive starting batteries, motorcycle batteries, ATV batteries, golf carts batteries, and flooded batteries for solar and emergency backup systems.


2. Sealed Batteries
This term can refer to a number of different constructions, including only a slight modification to the flooded style. In that case, even though the user does not have access to the cell compartments, the internal structure is still basically the same as a flooded battery. The only difference is that the manufacturer has ensured that a sufficient amount of acid is in the battery to sustain the chemical reaction under normal use throughout the battery warranty period. Other types of lead acid batteries are also sealed, as explained below. Very popular uses are engine starting and limited starting/deep cycle applications.
For this type of battery the typical absorption voltage range 14.2 to 14.7 volts; typical float voltage range 13.1 to 13.4 volts.


3. VRLA Batteries
This stands for Valve Regulated Lead Acid battery. This is also a sealed battery. The valve regulating mechanism allows for a safe escape of hydrogen and oxygen gasses during charging.
For this type of battery the typical absorption voltage range 14.2 to 14.5 volts; typical float voltage range 13.2 to 13.5 volts.
VRLA batteries are common and found in many applications, such as medical mobility scooters batteries and toy and alarm batteries.


4. AGM Batteries
The Absorbed Glass Mat construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both the discharge and recharge efficiency. Actually, the AGM batteries are a variant of Sealed VRLA batteries, just a more advanced design. Popular usage includes high performance engine starting, power sports, deep cycle, solar and storage batteries.
For this type of battery the typical absorption voltage range 14.4 to 15.0 volts; typical float voltage range 13.2 to 13.8 volts.
AGM batteries are common and found in many applications such as RV batteries, boat batteries, motorcycle batteries, ATV batteries, and UPS & Telecom batteries for generators.


5. GEL Batteries
The Gel Cell Battery is similar to the AGM battery style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a gel cell battery has a silica additive that causes it to set up or stiffen. The recharge voltages on this type of cell are lower than the other styles of lead acid battery. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications. If the incorrect battery charger is used on a Gel Cell battery, poor performance and premature failure is certain. Battery chargers with gel profile will have information either on the unit, or in the manual, about gel compatibility.
For this type of battery the typical absorption voltage range 14.0 to 14.2 volts; typical float voltage range 13.1 to 13.3 volts.

https://www.batterystuff.com/kb/article ... m-gel.html