AGM Charging profile

[wes4dbt]

I just got a set of NF 22 AGM's. My charger is the Victron Smart IP65.

This is the first set of AGM's I've got since I got the charger, all the others have been gel. So I was wondering if I chose "Normal" preset choice would that be correct for AGM's.

The "Normal" preset setting are,

Absorption 28.8V
Float 27.6V
Storage 26.4V

Temperature Compensation is -32mV/C

Thanks

[martin007]

Temperature Compensation is 0.005V / ºC

[wes4dbt]

Temperature Compensation is 0.005V / ºC

Thanks,

I think that's per/cell so it should be 60mV total. I think, lol

[martin007]

> https://www.wheelchairdriver.com/AGM-GEL.htm



I think it is valid to compensate the charge of AGM batteries at 0.005 v

"To compensate for battery temperature not at 20°C, subtract 0.005 V/cell for each 1°C above 20°C; add
0.005 V/cell for each 1°C under 20°C."

> https://www.wheelchairdriver.com/pdf-fi ... arging.pdf

[Burgerman]

In cyclic use (what we do) you should choose 14.5V or 14.6V cv stage for AGM and make it ends when it reaches around 500thC to 1000thC (where C is capacity). So a 50Ah battery would end at approx 100 to 50mA or 8 hours at CV which ever occurs first. Then float at 13.6V for around 6 hours or so, and then drop to 13.2 to 13.3V indefinitely. Double those figures for 2 in series of course. At room temperature.

Turn off all the auto nonsense, make a fully custom profile.

[martin007]

I charge my AMG batteries to 28.8 v

[Burgerman]

Anywhere from 14.4 to 14.7V is OK for AGM. At 20C. If its warmer as spain is its best to err on the lower side. So if the battery is hot in summer charge at a bit less. Maybe if its 30C drop it to 14.2V or the current will never drop to a low figure. With your charger you should set it to go to float at say 300mA. (0.3A) and then float.

[martin007]

I always have a thermometer handy.

[wes4dbt]

Anywhere from 14.4 to 14.7V is OK for AGM. At 20C. If its warmer as spain is its best to err on the lower side. So if the battery is hot in summer charge at a bit less. Maybe if its 30C drop it to 14.2V or the current will never drop to a low figure. With your charger you should set it to go to float at say 300mA. (0.3A) and then float.

I should try adjusting my profile this summer. This chair is usually kept in the garage where it gets very hot (110+) from June thru August. Right now it's being kept in the house because my normal house chair is broke down. Hopefully it will be fixed in a couple of days.

[Burgerman]

Another thing to consider is that battery ageing is in direct proportion to temperature too. And its very severe! A few degrees cooler = double the calender life. So find somewhere cool to store it.

[martin007]

Another thing to consider is that battery ageing is in direct proportion to temperature too. And its very severe! A few degrees cooler = double the calender life. So find somewhere cool to store it.

What is the ideal storage temperature for GEL, AGM and Lifepo batteries?

[Burgerman]

Around the same temperature as your fridge in longevity in storage is all important. Say 3 or 4 degrees C? Not very practical though.

[martin007]

Unfortunately I don't have such a big fridge...

[Burgerman]

Batteries age because of many things.
Deep discharges damage the active material so dont discharge deeply. Lead and lithium.
Not keeping them topped up 100% and charging to 101% after discharge also kills them faster. (Lead).
Not chargng straight away after use too... (lead)

Lithium prefers to never be full, never be empty, never be heavily discharged at high rates, and doesent like being warm... Avoid those things and they live almost forever. Dont and they will soon fail.

But storing batteries is like storing food. Unwanted chemical reactions happen over time. This is called calender life. And just like food it lasts longer when kept cool. As this slows all reactions. Including those that age the battery. And those that make it actually work...

[martin007]

Not keeping them topped up 100% and charging to 101% after discharge also kills them faster. (Lead).
Not chargng straight away after use too... (lead)

Can you develop this?

[Burgerman]

Develop t?
Yes.

Batteries die from many things.
Wheelchair batteries generally die from bad use and bad charging practices.

A battery at a basic level is all lead plates. These are lead grids, a lead "frame" into which is pasted finely ground up lead paste.
Each place is submerged in a water and sulfuric acid bath.
When it is DISCHARGED the acid in the electrolyte is split into lead sulfate (which coats every one of the lead particles deep inside the plates) and lead dioxide on the opposite plate. And the deeper it is discharged the heavier this sulfate coating is. It can and does cause the plates to expand and can push out and damage the pasted lead particles too. If discharged deeply. Now, as you recharge this is all reversed. The lead sulfate is the important bit, this is returned back to the electrolyte from where it came. The problem here is many fold!

Dont wait! Warmth, and time, causes this lead sulfate to form large crystals over time. Once it has, it is inside the pasted material deep inside the plates displacing the lead particles. Worse these larger crystals no longer conduct electricity. So can NEVER then be reversed. So its important to do several things.

1. Recharge as soon as it is possible to do so. So that 99.999% can be returned to the electrolyte.
2. Dont store a battery in any state other than 101% charged. If its 99% charged and you leave it this way then you just lost 1% of its capacity for good.
3. Make sure that you COMPLETE a full 101 % charge at least every 7 days. That doesent mean charge with a mobility charger till it goes green. Thats NOT 100% or even close to it. It takes a full 10 or so hours to charge a lead battery with a correctly configured charger. And at LEAST 16 to 20 with a typical mobility charger. Regardless of its green light coming on! It needs a long time AFTER this at float. Because the mobility charger stops the CV stage far, far too soon.
4. You need the right voltage. A few tenths of a volt too high will reduce a gel battery cycle life by 60%. A few tenths too low will likewise half the life of a good AGM like odyssey. So be sure you know. And set correctly. Mobility chargers do all sorts of incorrect things here! I dont use them.

[martin007]

Develop t?
Yes.

Batteries die from many things.
Wheelchair batteries generally die from bad use and bad charging practices.

A battery at a basic level is all lead plates. These are lead grids, a lead "frame" into which is pasted finely ground up lead paste.
Each place is submerged in a water and sulfuric acid bath.
When it is DISCHARGED the acid in the electrolyte is split into lead sulfate (which coats every one of the lead particles deep inside the plates) and lead dioxide on the opposite plate. And the deeper it is discharged the heavier this sulfate coating is. It can and does cause the plates to expand and can push out and damage the pasted lead particles too. If discharged deeply. Now, as you recharge this is all reversed. The lead sulfate is the important bit, this is returned back to the electrolyte from where it came. The problem here is many fold!

Dont wait! Warmth, and time, causes this lead sulfate to form large crystals over time. Once it has, it is inside the pasted material deep inside the plates displacing the lead particles. Worse these larger crystals no longer conduct electricity. So can NEVER then be reversed. So its important to do several things.

1. Recharge as soon as it is possible to do so. So that 99.999% can be returned to the electrolyte.
2. Dont store a battery in any state other than 101% charged. If its 99% charged and you leave it this way then you just lost 1% of its capacity for good.
3. Make sure that you COMPLETE a full 101 % charge at least every 7 days. That doesent mean charge with a mobility charger till it goes green. Thats NOT 100% or even close to it. It takes a full 10 or so hours to charge a lead battery with a correctly configured charger. And at LEAST 16 to 20 with a typical mobility charger. Regardless of its green light coming on! It needs a long time AFTER this at float. Because the mobility charger stops the CV stage far, far too soon.
4. You need the right voltage. A few tenths of a volt too high will reduce a gel battery cycle life by 60%. A few tenths too low will likewise half the life of a good AGM like odyssey. So be sure you know. And set correctly. Mobility chargers do all sorts of incorrect things here! I dont use them.

I've been doing all that for years.

[Burgerman]

Me too.

[wes4dbt]

Regardless of its green light coming on! It needs a long time AFTER this at float.

That's one thing I've noticed about these Victron chargers, they don't stay in float very long. Seems to go into storage within a couple of hours. I set my storage voltage a little higher than spec because of that.

Also, there's something strange about this Quantum chair, even in storage it draws .2A . Maybe it's the clock or some other electronics that are always on. My Air 2 chair doesn't do that.

[biscuit]

Are you able to set a "bulk" voltage on the IP 65, wes4dbt, or is it preset by Victron? My blue smart ip22 will not allow changes to the bulk stage voltage. Actually I'm not best pleased with my Victron for a bunch of reasons. Perhaps it was the smartphone app gave me hassles. But I don't think a PC would have done better.

PS I think all chairs draw a bit of current even when switched off. Certainly all mine do.

[Burgerman]

I never saw ANY victron that wouldnt allow a complete custom setup (a user setup profile) but they make it hard to find and do. And this is on a proper PC. NONE of their standard presets with outo everything will properly charge a battery. They will charge it in a fashion but not properly unless you take over all (WELL HIDDEN) settings. They go out of their way to make it hard to do. Forget phones.

NO chair should be taking 0.2A when off. Thats a full Ah every 5 hours. Or if you prefer 4.8Ah per day! Thats 67Ah (and dead flat) after 2 weeks.
My own chairs, various systems over the years only needed less than a single Ah adding (still takes 8 hours) after a few weeks doing nothing. But it is important to actually do this regardless.

Typical is approx 10 to 15mA when off. Or practically nothing. Just eNough to cause battery degradation if you dont do a proper charge every 2 weeks. (will cause sulfation otherwise).

What are you measuring this with?

[Burgerman]

That's one thing I've noticed about these Victron chargers, they don't stay in float very long.

You say it goes into storage in a couple of hours. Thats also float!

It should do this if correctly configured.
Charge at its 12A setting (XLR plug?) or 13A stil OK. Or more via Anderson connector. Or a little less depending on charger options. More is better. Thats CC or bulk stage. There IS no voltage at this point as that depends on the battery and it will climb as the battery voltage slowly increases and the charge is accepted by the battery.

When it reaches the CV (absorption) stage which should be around 14.5V (29.0V) then the current will quite naturally fall away quickly at first. And slowly as time goes on. The victron tries to be clever and guess how long here. Turn that nonsense off! In cyclic use you want it to end charge at around 500thC (so 50mA for a 50Ah battery) and go to what you call float. This is for a limited time. In this case it should be around 13.8V as theres no way to set a longer float 1 stage on that charger. Then it goes to the LONG TERM (much slower to top off a battery) lower float mode. This should be set to a safe permanant float level so that the chair can be left unattended and connected indefinitely. It should NEVER go back to the charge stage. So turn that off too. If it wont let you then set it to the ongest possible interval that it allows. A week or more.

[Burgerman]

Here is an example of quite how long it takes to PROPERLY and completely charge a lead battery.

This was at 30A charge rate. It took many many hours before all the sulfates were returned to the acid. As the current gradually falls away at ever slower and slower speed.

If you stop the CV stage with an 8 hour limit, the lower float voltage continues to charge the battery and it eventually gets topped off anyway but even slower! But we only have overnight to do this. So a longer CV stage is a much better way to achieve a full charge overnight. Ends up with longer service life.

If this battery was charged at less than 30A initially then it would have added several hours to the charge time. Most hobby chargers give a green light after about 4 hours and tell you its done! This Odyssey battery was being held solidly at 14.7V during this charge.

[wes4dbt]

Typical is approx 10 to 15mA when off. Or practically nothing. Just eNough to cause battery degradation if you dont do a proper charge every 2 weeks. (will cause sulfation otherwise).

What are you measuring this with?

The .2A is displayed by the app. I don't measure it. As I said, my Air 2 shows 0 usually.

Is this constant .2A in storage harmful? Not that I can do anything about it, except maybe unplug the chair.

[Burgerman]

You are talking about the chargers current and not the chairs off current draw from the battery those are 2 different things. Or at least I think you are. The only way to know the chairs draw is to remove the charger and use a mA DC clamp meter over a battery cable.

-When you charge a battery PROPERLY it will be 101 percent charged. To then hold it at the CV voltage means its current draw SHOULD be less than 1 500th to 1000thC. ***
-When the float 1 voltage is still happening (2 hours on a victron??) this current should be very very low like a few mA. Maybe 30 or 40? ***
-When it drops to store float voltage this should then be about 3mA plus whatever the chair draws. Usually around 10 to 20mA maximum. ***

*** What actually happens is that the battery is NOT fully charged. And so is still drawing much too much current on float. This is likely the current you are seeing. The other thing that causes this is if the battery is new (takes a bunch of charges to actually form the plates fully) or that it has already become partly sulfated. Due to not being fully 101% charged. You must put back more than you take out every charge!

So likely the victron is stopping the CV stage too soon. Because you havent yet took charge...

[wes4dbt]

So likely the victron is stopping the CV stage too soon. Because you havent yet took charge...

I have set the absorption time to 8hrs as suggested.

[Burgerman]

But unless you disable thie auto part it decides sooner that its charged regardless. Cant remember what they call it.

[thetascott]

I have been using the Victron IP65 for several months. Quickly learned the defaults are horrible. Charger is awesome though once customized.

Currently saving up for an IP22 rev 2 (not rev 1). 12A instead of the IP65's 8A and allows setting a tail current (rev 2 only). Can then set it to float when CV reaches 0.3 or 0.2 which is not an option with the IP65.

I do have one question. I am a light user on days I stay home. I have MK Gel batteries. Currently do 2 hours of CV at 28.2 which gives approx. 2.5Ah and then it does 8 hours at 27.6 to get the final 0.5Ah so 3Ah in total. I use much more when I venture outside and increase the CV duration. Is it possible to overdo the CV on my light 3Ah days? Could I set the CV to 8 hours and lower the float without issue if I wanted? Considering lowering the float to 27.2 and increase the CV to 4 hours on the light days for just increase work comes calling.

[Burgerman]

I do have one question. I am a light user on days I stay home. I have MK Gel batteries. Currently do 2 hours of CV at 28.2 which gives approx. 2.5Ah and then it does 8 hours at 27.6 to get the final 0.5Ah so 3Ah in total.

Does it drop to almost zero current? It should or that 2 hours isnt long enough. Say 70 to 100mA?

I use much more when I venture outside and increase the CV duration. Is it possible to overdo the CV on my light 3Ah days? Could I set the CV to 8 hours and lower the float without issue if I wanted? Considering lowering the float to 27.2 and increase the CV to 4 hours on the light days for just increase work comes calling.

It would result in a faster charge completion. 4 to 6 hours CV. Thats what I would be doing. I mean zero CV and continual 27.6 will charge them fine. Even from dead. But it would take 2 full days to get them fully saturated 101% full. The reason we do an elevated CV stage is so that we can put that Ah back in considerably faster. And its a balance. Too high voltage and you damage the gel (voids and bubbles) and so watching the temperature matters. And too low voltage and its impossible to get a complete charge overnight.

This is why I charge at a high rate. 12A minimum. 50A maximum if anderson connectors. Because it rapidly completes the CC stage leaving longer for the slower CV stage. It helps to get a more complete charge at the correct voltage.

If you do this NO float is needed.
AGM 14.6V (Odyssey 14.7) and any current, higher is best. Continue until 1000thC or 8 hours CV whichever is sooner. No float then required, fastest complete charge possible.
GEL same but 14.1V and 10 or 12h @CV (gel is slower partly because of voltage) and 500th to 750thC. Doesent usually reach this low current. No float needed.

After this, you can use a LOW float (or store as your victron calls it) indefinitely. Typically 13.2 to 13.3V.

Here is the MK charge data sheet for gel.
It basically tells you the same thing.
www.wheelchairdriver.com/MK1.pdf

[thetascott]

Does it drop to almost zero current? It should or that 2 hours isnt long enough. Say 70 to 100mA?

Yes, the app shows a steady 0.0 when I get up. My concern is the occasional day when I need to get up early due to work as it's not at 0.0 those days. Mainly wondering if staying at CV longer than needed does any damage.