Problem with MK Powered 74 Ah 12V GEL Batteries

[Burgerman]

Another reason you cannot go by battery meters. The amount you have left (range) depends on the SPEED you discharge them... Its not a fuel tank. So your battery gauge is useless.

If you go full speed for just 2 hours, 16km? And even if you go into the orange you only have THIRTY PERCENT of battery... Which is why impedance and peukert are important. Dont buy cheap AGM batteries.

[Burgerman]

And this is why we prefer lithium. Lead is useless.

[quadcopter]

You bought the wrong batteries. 5.5mOhm no use!

Sorry, what does is mean "5.5mOhm"?

[Burgerman]

Impedance. Its an AC current used to measure internal resistance.

So your batteries are 5.5mOhms. Thats almost twice as bad as MK which are 3.5mOhm, and the Odyssey batteries which are 2.5mOhm.

What difference does it make? DOUBLE the voltage drop under load, and double the amount of peukert since these are directly related. So your cheap battery shrinks much more under load...

Basically, theres 2 batteries worth buying. MK gel, and Oddysey AGM. The rest are all worse. Often a lot worse. But dont expect miracles, all lead is crap! As you are only now figuring out.

Theres a very good reason your phone, drill, lawnmower, laptop, electric car/bike, and torch, toothbrush, hedge trimmer and everything else in 2018 uses lithium.

[quadcopter]

I'm mixed up.
The manual says the batteries are perfect for wheelchairs and have 600 cycles of 100% discharge.
I ran 1-2 times a week only in spring/summer. Thus I went 30-40 trips and only a couple of them were 15-17 km long.
And got fail...

[woodygb]

The manual says the batteries are perfect for wheelchairs and have 600 cycles of 100% discharge.

They lied.

You should avoid EVER deep discharging any lead battery or it's capacity deteriorates very quickly....80% discharge MAXIMUM.

The main problem is that it is impossible to accurately determine the D.O.D ( Depth Of Discharge) state of you batteries....thus you never really know how well or badly you are treating the batteries.

[steves1977uk]

Best place for that manual is in the bathroom! You might get 600 cycles if you hardly move about and watch TV all day, otherwise no chance.

Lead batteries are ancient technology and it's beginning to show. As BM says, MK Gels or Odyssey AGM's are the only ones worth fitting to any chair, the rest are pure crap!

Steve

[steves1977uk]

http://adyasolar.com/wp-content/uploads ... ST1207.pdf

Says those batteries are 6.5mOhms which is even worst! Throw them in the garbage bin!

Steve

[Burgerman]

I'm mixed up.
The manual says the batteries are perfect for wheelchairs and have 600 cycles of 100% discharge.

There are NO lead batteries that get even close to that even in a lab. Theres something wrong with those figures. As you found out. They dont so much lie, as fail to explain the data. After say 100 cycles capacity may be down to 80% and they then continue until its down to 50 or less. Pure traction batteries, can be cycled about 500 to 600 times to 80% depth of discharge. But even these will be down to 150 to 200 cycles at 90% discharge. And these are around 10 to 12% lower in capacity that a similar physical sized battery. Every time you see a battery with 80Ah or more in a group 24 case, then impedance or cycle life has to be worse. Its all a balance.

The best mOhm, capacity, and cycle life combination is the 74Ah MK gel or Sonnenschein dryfit 500 gel, for normal users. For sport, fast chairs, hills, off road, overweight users, reprogrammed, will get better range and performance and faster charge with the smaller 68Ah Odyssey and much less voltage drop under the heavier load. Lighter users are better with the MK.

Even then, lead just sucks.

[shirley_hkg]

Could it be a storage issue ?

You don't seem to use it in winter , do you ?

[quadcopter]

Could it be a storage issue ?
You don't seem to use it in winter , do you ?

Yes, I rarely go out in winter on my power wheelchair. The wheelchair stays in my room where temperature is about +25 C.

[quadcopter]

You might get 600 cycles if you hardly move about and watch TV all day, otherwise no chance.

I understood that I cannot get 600 cycles but I expected at least 300-400, not 30-40.

[Burgerman]

If you USE lead batteries hard, and I mean good ones, you dont get a year.
Remember that they age in MANY ways inc:

Time. Calender life. Thats 10 approx years in telecom style use. Where they are kept on float at a low float voltage, temperature compensated at 100% fully charged indefinitely in a cool room. And never discharged at all. Calender life in a partially discharged state, in cyclic use, in warm conditions is only a few months. And during those months performance drops to much less than new. (80% is the usual figure, but manufacturers that claim more than 500 cycles usually mean 50 or 70% remaing battery capacity but dont say so...)

Cycle life. You get thousands at low discharge levels. But just tens at high discharge levels.

Internal resistance increases with age, cycle life. Which further reduces range and increases the peukert level (shrinkage at high currents we need). So while Ah reduces by say 10% range reduces by 30%.

All of the above affect each other. As the battery deteriorates, then the same trip, discharges the battery further since it now behaves like a smaller battery, causing more damage faster. Its an ever accelerating process.

Some people say they have a battery thats good for 10 years, and they only charge it once a week. These people dont USE their chairs, they sit watching TV or drinking tea... Those that USE a chair get less than a year from a lead battery. They are inadequate for an EV.

What makes it LOOK even worse is battery gauges. As your battery resistance increases the voltage depression gets worse. So drive 2 km and the battery voltage drops more than it used to do. (NOT ITS DISCHARGE LEVEL). So now your battery guage reads low. And the battery is not. This voltage depression is due do peukert. It takes 24 hours to fully recover. Only then will the battery gauge make any sense. So when I say HOW DO YOU KNOW? This is what I mean. And another reason not to buy high mOhm batteries.

Yes, I rarely go out in winter on my power wheelchair. The wheelchair stays in my room where temperature is about +25 C.

Thats warm. Batteries age faster in warmer conditions. And they should be kept on a LOW FLOAT during storage, such as 13.3v at 25C. OR charged fully, and then DISCONNECTED from the chair (remove a terminal). As a turned OFF chair still drains the battery at 5 to 15mA continuously. Causing sulfation in storage. Even if topped up weekly (which helps). And a battery ages at double the speed at 25C compared to 15C. On top of the added sulfation.

[shirley_hkg]

Hi to All.
I've got problem with batteries again.

They worked perfectly. I easy run 15-17 km. I go out 1-2 times a week.
3 June 2018 (year after purchase) I had trip about 17 km. At the end there was half of charge. Wonderful.

In two weeks I have short trip and noticed the charge drop more than usual.
In other two weeks (29 June 2018) I could run only 6 km.
So just in one month (or even less) the range dropped drastically.
Now I can run only 5 km.



I don't understand what's going on. New batteries and proper charger but such a fail.
Could my wheelchair damage the batteries?
?

Did it happen after only ONE 17km drive since last winter ?
You'd measure the voltage of each battery again. If both batteries read indifferent , they are damaged during storage .

Battery seems easier to go dead in storage than it was being cycled .

[quadcopter]

Did it happen after only ONE 17km drive since last winter ?

No, I had 2 trips about 12-15 km before (as I remember in May).

[Burgerman]

They may improve a little with some shallow 1 or 2 km drives, and 24 hour charge cycles, maybe 4 or 5 times to see an improvement. Because they have likely become a little sulfated due to the way you store them and dont use the chair. LEAVE THEM ON CHARGE long after the green ready ligh comes on. For 48 hours each time you return. They are then on float. Float will remove any sulfation that they have that IS removable. Not all of it will be because it turns into larger non conductive crystals over time if it is allowed to do so.

If you do this 5 or 6 times or so, and they dont improve then you have likely found out how crappy cheap lead batteries are.

[Burgerman]

Also do you realise that turning left/right in the house takes up to a hundred Amps per motor, every time you do it? Whilst traveling in a straight line at speed takes only 10? Its easy then to waste say 10km of "range" just getting a wash and tidying up the house before you leave. Very easy!

So you cant really determine range subjectively. A slight camber on a road edge may require 3x the battery power than a flat surface. And a slight hill may take 4x the Amps, than the flat surface does. And coming back DOWN that same hill will still not give you back the extra required going up it. Due to both peukert and inefficient regeneration. So the exact route, and exact joystick movements can make a massive difference to range. Such a thing as where you cross a road with steep crown. Esp if you are using the battery gauge to judge how much your battery is actually discharged. Because it cant possibly tell you that. Those exist to give a user confidence. They are not much use for telling you how much range is ACTUALLY left!

[quadcopter]

They may improve a little with some shallow 1 or 2 km drives, and 24 hour charge cycles, maybe 4 or 5 times to see an improvement. Because they have likely become a little sulfated due to the way you store them and dont use the chair. LEAVE THEM ON CHARGE long after the green ready ligh comes on. For 48 hours each time you return. They are then on float. Float will remove any sulfation that they have that IS removable. Not all of it will be because it turns into larger non conductive crystals over time if it is allowed to do so.

If you do this 5 or 6 times or so, and they dont improve then you have likely found out how crappy cheap lead batteries are.

I always keep the charger plugged in as the manual says:

With your ProSport plugged in properly, it will automatically/ fully charge your batteries
while it conditions and extends the life of your batteries. Always leave your charger plugged
in to reduce sulfate build-up allowing your batteries to be fully charged and maintained
for your next fishing trip.

Anyway thanks for the tips and explain.

[Burgerman]

About why a battery impedance or resistance matters. Referring to the mOhm measurement. This is important because it determines the battery performance and I an going to show you a demonstration of HOW MUCH it really matters.

Once a car is running its alternator powers everything. So a car battery exists just to start the car. And to run a radio or hazard lights. But primarily its a STARTING BATTERY. A typical car takes a couple of hundred Amps to START IT UP. Just as you chair does in a turn. But typically it takes just 1 to 3 seconds. It actually takes less than 1Ah to do so. So in theory, you could just fit a 4Ah lead battery to be very sure you could crank the car for a minute solid and have plenty left in reserve right? Well you cant. Why not? Because of its internal resistance. It simply wont crank.

That mOhm figure realy matters. If you try to crank a car with a 20Ah lead battery, it simply wont crank and will just go click, and the lights go out. The voltage collapses. So we end up having to fit a 70 or 100Ah battery that weighs a ton where a tiny 4Ah battery is all that is really required. This is because lead is crap, and impedance (resistance) is ALL IMPORTANT!

So what if you could get a tiny 4Ah battery that really was ultra low impedance, one with only 4Ah and the same size as a pack of cigarettes. Well those EXIST! I use them in my QUADCOPTER. (I note your name so presume you too have these!) Your lipo battery is an almost zero impedance battery. It can crank a car, for longer than a huge 100Ah lead brick can! And its low impedance is the reason.

When you buy a battery dont worry too much about Ah, that is useless as a parameter used alone. Look at impedance.
Heres the proof.
Tiny FOUR AMP HOUR (4Ah) lipo performs as well or better than the 100Ah lead brick, because of its low impedance.
Its why an Odyssey with 2.5mOhm is 3x better than your new batteries with 6.5mOhm.


youtu.be/WkKRqaNPIBE

[quadcopter]

I use them in my QUADCOPTER. (I note your name so presume you too have these!)

I don't. I thought about quadroplegic when invented the nickname :-)

[Burgerman]

Can you see the difference though?

The tiny low impedance 4Ah battery beats the massive 100Ah high impedance lead in performance under load. That makes it 25x better at high currents! And 80x lighter. And 45 times smaller! And 25x less capacity required. Because of impedance alone.

[Burgerman]

These are common among hobby heli flyers. https://hobbyking.com/en_us/turnigy-bol ... xt-60.html

This is a 3 cell, or 3S battery.
Its almost 12V. It is 5.4Ah
Its not 1C or 3C like our lifepo4 wheechair lithium batteries. Its a huge 65C cont, or 130C pulse! (And even 90C packs are available!)

This is why they start cars easily. This one is 5.4 Amp hour x 65C = 350A continuous or short term pulse 700Amps! From a battery you can put in your top pocket.

[Scooterman]

Dont know what those do.


Correct charge voltage is 13.8 to 14.1V CV stage. (best 13.95v) Less if warmer than 68f.


http://www.wheelchairdriver.com/MK1.pdf

How do recommend measuring the charge voltage of a basic 3 stage charger.

Is it:

a) at the battery terminals while the charger is connected?

b) the open circuit output voltage of the charger?

[Burgerman]

You need to MONITOR the voltage at the battery terminals, ideally. As it charges. If the cables are thick enough you can also monitor the voltage at the charger end. Thats how the charger does it. Remember that the thinner the cables the higher the resistance. So if no or almost no Amps are flowing, thin cables give an accurate voltage. But if the charger is charging at a high current, with the typical thin wires used (especially using a XLR charge plug and the chairs wiring loom) then the charger voltage may be correct at say 28.2V but the battery volts will be less. As the battery becomes charged, current falls and the voltage will eventually match the chargers voltage. But this generally will be within say 0.3V ish.

So to measure properly, connect the voltmeter to the battery. And monitor the voltage as it begins to rise, over time. There SHOULD be a point where it stops rising and then stays solid at the highest CV voltage for a few hours (2 to 6 hours) as the current gradually falls away to a very low level. It will then STOP the high CV volt charge, and should then drop to say 27V typically for float. It should sit there at 27V indefinitely.

So theres no way to measure it without watching it over time. The PL8 does this accurately, and draws you a nice graph. It actually measures volts accurately even down long wires. Because it charges using a square wave that is a mix of higher voltage and OFF at high frequency. So it can read the battery voltage in the off periods. When no current is flowing. Trying to read a voltage from any charger that is not connected to a battery will not work usually.

[Scooterman]

Thank you for that I do appreciate it . I will try with my salsa and the larger scooter. Both have generic 8 amp sunrise chargers but of a different design. The salsa's charger is a much bigger grey metal box, and the scooter a small black rectangular box.

The 60Ah sonnenschein dryfit batteries on the salsa are pretty much sh*gged. After only about 3 miles I lose all three green leds. Yesterday I measured the SoC at the XLR plug after disconnecting it from the charger for +4hrs, and it was (according to my meter) 26.28v.

[Burgerman]

Yesterday I measured the SoC at the XLR plug after disconnecting it from the charger for +4hrs, and it was (according to my meter) 26.28v.

You cannot determine state of charge on a lead battery unless it is:

A) disconnected from the chair or scooter.
B) after waiting 24 hours, or longer.

Your charger was charging at 28.something volts. Your reading of 26.28v was the battery dropping from this charge voltage, slowly, to the true battery voltage, which takes at least a full day. It may have dropped a tiny fraction more, or it may have dropped another 2 volts in time.

And even then its a guide, not accurate and varies with temp, and battery manufacturer and exact chemistry. Which is why your battery meter is basically not worth looking at. At best it can give an approx guess to withing about 35 to 45% of reality... As long as you give the scooter or chair a rest and are not moving for 20 mins at least. And even then, how can you know what its last orange light really means? It may be programmed to come on at any voltage depending on programmer whim. And at 10% remaining, or 40% remaining. And the chair may actually stop moving at 50% if the battery is high impedance on a hill. State of charge, even if you could know it, doesn't determine when the scooter or chair stops moving. So even if the meter was "accurate" and it cannot be, its no real help.

For e.g. A cheap Chinese AGM is high impedance. It gets higher still as it ages. Its entirely possible that you can use the PL8 to measure its NEW capacity at 80Ah and get 15 miles range. After a year its impedance has increased, and range has fallen to say just 4 miles. But when you test its capacity with the PL8 its maybe still 78Ah. The thing that stops the chair at 4 miles is the voltage drop under load due to the increased impedance (resistance) combined with the increased peukert level this also causes. When the actual Ah is still at about 80% full... If you wait 24 hours, you can then get another 4 miles...

This is why a 68Ah Odyssey gives better range on a heavily loaded chair, than an 80Ah generic AGM, or a 73Ah MK gel. And as they age, the Odyssey gets further ahead. Its not Ah that matters its the speed that you can get that Ah out.

Odyssey 68Ah, 2.5mOhm TWICE as good as
MK gel, 73Ah, 4.5mOhm...
Generic cheap AGM, 6.5 to 8mOhm, battery feels dead, and chair doesn't respond properly when new. And range is about 2/3rds what you would expect, and gets worse fast.

Hence the higher the impedance the more the battery shrinks under higher loads. See this... download/file.php?id=8663&mode=view

[quadcopter]

Hi to All again.
I sent my EverExceed batteries and ProSport charger to vendor to apply warranty.
They measured charge/discharge current and said my charger is bad and it killed the batteries.
They said the charger doesn't fully charge the batteries.
They sent me a chart:

EverExceed chart

As I see charging time is about 18 hours. 14 hours with current 4-6A
and 4 hours with current 1.6-4A. Also there is voltage raise to more than 29V and then drop down.

Here ProSport charging chart (from the manual):

ProMariner ProSport charging chart

EverExceed manual says you have to charge battery with 14.1-14.4V to full charge
(fully charged - when charging current drops to 2-3 mA/Ah.) plus about 2 hours
"overcharge" it. Total charging time for C10 charger is 14 hours.

So I have a question - is my charger really bad and killed the batteries?

[quadcopter]

Total charging time for C10 charger is 14 hours.

Sorry, 10% from C10. In my case 7A (batteries are 70Ah).

[Burgerman]

If that chart is actually what is happening, then yes.

It should remain CONSTANT (meaning it should sit at EXACTLY) the correct voltage, until amps fall to a very low level. Almost no current. Then end. That isnt what it shows.

Why? Can be that you set it wrong? Long cables? Faulty charger, or firmware errors? Would need it here to know.

Its why I use the PL8. I can set the charger to do EXACTLY as the battery manufacturer specifies. To a few mV at CV.

My hobby chargers do an EXACT 2 stage charge, to 1000thC and or 8 hours CV at the correct voltage whichever is sooner.

The graphs look EXACTLY like this:

[martin007]

ZXD2400 PSU modification is a good lead batteries charger.

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