Battery’s

[raymondhutton88]

Could someone tell me the best battery’s to use on my power chair please.

[ICEUK]

Come on, give us all a clue. What colour is the wheelchair? Mwd, dad, fwd

[Burgerman]

Best battery for what?
Lithium DIY for 5x the range, 10 years life, less weight, much faster charging.
MK gel, best balance of everything if you cant do lithium. Mut be charged correctly.
Whatever the manufacturer fitted as stock.

The biggest agm you can fit, such as the cheap cheerfil leoch ones. https://www.ebay.co.uk/itm/124356355753 ... SwpUVci7Ym they will give less performance de to higher internal resistance, and age faster but half the cost. Suits backup chairs or those that dont have high performance/sport/etc in mind.
Odyssey for best everything but £££.

In the largest capacity ALWAYS that fits your chair possible in every case.

[Frank]

My MK GEL batteries MK73 M24-SLD G for wheelchair is only a few months old, they charge fully but only after a day of not using the chair the wheelchair’s gauge goes down from 10 to 2 or 1. So the batteries are not holding their charge and I suspect that there may be a faulty cell. I tried to charge the batteries with another charger but the problem was still the same. How can one check these batteries for faults? Thank you.

[Burgerman]

My MK GEL batteries MK73 M24-SLD G for wheelchair is only a few months old, they charge fully but only after a day of not using the chair the wheelchair’s gauge goes down from 10 to 2 or 1. So the batteries are not holding their charge and I suspect that there may be a faulty cell. I tried to charge the batteries with another charger but the problem was still the same. How can one check these batteries for faults? Thank you.

Frank

Several things.
You may be correct. Bad cell. But from years retailing batteries I can tel you that almost never happens. With hundreds returned with a suspected bad cell only one actually ever was***. Battery manufacturers cut open batteries on a bandsaw after testing electrically to find out.

"**unless they were incorrectly used or abused. Physical damage on the inside that may be invisible externally. Or repeatedly undercharged (did you give regular 20 hour charges? at least weekly) Or charge above the recommended 13.8 to 14.1 max volts? Or fit them without checking both were at the same full state of charge? Because that overcharges one and undercharges the other. And are you SURE they reeally were new? There plenty of stories about dealers fitting used ones they just removed from a different chair. Massive profit if theyt get away with it 5 or 6 times a week...

So how to test.
Remove them
Charge each INDIVIDUALLY at the correct 14.1V for 12 hours or until it sees current fall to 1000th of its capacity in amps. Then drop voltage to 13.5V for another 8 hours.
This is what your mobility charger SHOULD do. But they dont... And cause massive battery issues. And now for the first time since they were made they are actually correctly charged. If the previous treatment has not done too much damage.

Now you connect them to a known load. And measure capacity. I use the PL8 for this as it allows me to set the correct discharge rate to fully discharge them down to 10.5V over a 20 hour period. And this gives me an EXACT controlled discharge. So I can compare to the origibnal capacity. And thats thE ONLY way to test properly. Anything else is basically a guess.

You end up with a graph, and a mah figure.

Like this. This is DISCHARGE GRAPH of a pair of new batteries I had delivered that were AGM 75Ah at the 20 hour rate on the label. As you can see they actually held 74Ah. So as good as new! (almost).

[Burgerman]

Quick and dirty test will tell you if a battery is bad if its really bad. Charge for 20 hours. Ignore the green light. Then disconnect.

Then measure the voltage of EACH battery individually straight after charging.
Then measure the voltage after 24 hours.
Both batteries should be the same. If one is obviously lower then its defective. By maybe more than 1 to 2/10ths of a volt.

If the difference is huge, then obviously you have a bad battery. Why you have a bad battery is another question altogether.
This doese not really test the battery properly, but will show a bad cell.

You can also try monitoring the voltage of each battery as you drive up a steep hill or slope simultaniously. Two voltmeters. This tests to see if each battey voltage drops by the same amount. They should drop by the same amount within .3 to .4 of a volt. If its more you have a defective battery. OR two defetive batteries...

But the post above is the only accurate way to know exactly whats going on.

[Frank]

BM, thank you so much for your valuable information. I will do my best to find the problem.

[Frank]

Can somebody please tell me in your opinion which is the better battery between MK Battery MK73 / M24-SLD G FT 73 and 12V / 80Ah (C20) gel battery, Eternity Technologies, G06 12 066?

[Burgerman]

Both are OK as lead goes, both gel, both similar. Because I dont know the internal resistance of the eternity one I would buy MK.

[Seajays]

What about Odyssey no good any more ?

[Burgerman]

They are better. Lower impedance, faster charging, better performance. And more expensive. BUT they are longer than GRP24 at the top and so dont fit every chair, and they are slightly smaller grp 34/78 sixe (an inch less height).

Those are what is in my van, BM1 chair and have used them extensively in the past. They wont actually go in the Salsa or the Q chairs though.

[Seajays]

I bought at Q500H as aback up chair 1 year ago, Hardly ever use . Now stripping my BM2 chair to put new motors and the MK batteries are no good they show full charge and crash fast, MK are junk

[Seajays]

I bought at Q500H as aback up chair 1 year ago, Hardly ever use . No stripping my BM2 chair to put new motors and the MK batteries are no good they show full charge and crash fast, MK are junk

[hotwheels_75]

Were you unhappy with the Q500H or just never ended up needing the backup?

[Burgerman]

MK are junk

They are if not charged CORRECTLY.
If you do they are as good as lead gets. Unless you can fit odyssey.

[hotwheels_75]

What are people using to build lithium packs out of now? I assume there must be some newer better options than 5 years ago when I built my last pack?

[Seajays]

They were charged correctly with the supplied 10 amp charger. I can't wait to get my BM2 chair back together with new motors and powder coating and put new odysseys in the Q500H. My MK are junk.

[expresso]

how do you like that chair 500H ?

just curious - why put more lead in the chair - why not do lithium - the cost is the same to do - and cheaper in the long run

[ex-Gooserider]

They were charged correctly with the supplied 10 amp charger. I can't wait to get my BM2 chair back together with new motors and powder coating and put new odysseys in the Q500H. My MK are junk.

Supplied by who??? Did you check the actual charger voltages at each stage to make sure they were correct for MK Gels???

There has been much discussion in the past about how most wheelchair manufacturer supplied chargers actually OVERVOLT MK Gels when looking at the actual specs in their technical reference manual, and that this can shorten their life by up to 1/3.... The manufacturers wanted to supply chargers that would sort of work for both gel and AGM type batteries (which have different charging voltage requirements) so make them to 'split the difference' and undervolt AGMs and overvolt MK's... Because MK wants to sell lots of batteries to the wheelchair market, they re-wrote their advertising 'sell sheet' to say that it is 'OK' to charge at the higher voltage, which it is if you don't mind shortening the life of the batteries....

BM can supply all the gory details, but the above is a summary as I understand it....

ex-Gooserider

[F3Head]

My MK GEL batteries MK73 M24-SLD G for wheelchair is only a few months old, they charge fully but only after a day of not using the chair the wheelchair’s gauge goes down from 10 to 2 or 1. So the batteries are not holding their charge and I suspect that there may be a faulty cell. I tried to charge the batteries with another charger but the problem was still the same. How can one check these batteries for faults? Thank you.

You're not the only one having MK problems. My MK batteries were crap from the time I got them. This just happened after I replaced the originals which seem to have just as much juice as my new MK's batteries.

F3HEAD

[Burgerman]

The way to find out is to MEASURE them. I do this with all my batteries. All this seat of pants testimonial stuff tell you literally nothing useful.

If you measure a PROPERLY charged MK Gel, and it is supposed to be 74Ah at the 20 hour rate, and it actually is, then the battery is not the problem. I measured many.

If you CORRECTLY charge them, they continue to have this 74Ah after the first months use. Maybe a little more, like 77Ah. Then the deterioration starts, until the capacity is 74Ah minus 20% at which point they are end of life. This is all easy to measure. With a simple hobby charger, set to the correct settings.

Also you MUST be sure that they are actually NEW and not someone elses nice clean used ones... We already saw that rip off on this forum a couple of years back. Its very tempting to make a huge profit from batts that are used.

How do you do that?
You MEASURE capacity after around 10 cycles. It should exceed 74Ah.
Also you can check dates.
Also you can check VOLTAGE upon delivery, and reject any that are around 12.6V or less. And if they read 13V or more be suspitious of a recent "freshening" charge.. Ask why.

And modern universal one size fits all mobility chargers will over volt (and shorten lifespan) and undercharge (sulfate and reduce capacity) by undercharging. Does your charger take 12 to 16 hours to charge? If not its junk.

[Burgerman]

THIS is how to find out the REAL CAPACITY

This was a set of cheap AGMs, 75Ah.
Test ended a few secs after this screenshot. This way I cant bitch about "junk batteries" if range seems low. Because they are as good as new. Note the mAh removed, to the specified voltage oat the 20 hour rate. MEASURE because everything else is nonsense.

[shirley_hkg]

Why you set 20HR @7.75A for a 75AH battery ?

[Burgerman]

Because
a) the previous battery was a single 80Ah and the highest discharge rate it will do is a fraction less than 8A ( because 100w limit) So this matched those batteries pretty well.
b) I didnt bother to change it to 3.75A when discharging a series 24v set. Why? Becaue it will discharge at a max of 100w anyway, so with two batts in series that means the max discharge will end up as almost 20 hours regardless... At just under 4A average. So no need to set a lower Amp setting.

The actual discharge time is not very critical. Within a couple of hours at the 20 hour rate is close enough. (this ended after almost 19 hours at a 100w max discharge rate). If you didnt know this, then you could also just set a max of (75Ah, div by 20) 3.75A. But at a nominal 12V then 100W limit gives you this as an average over the 20 hours regardless. Even if you set 10A as a discharge rate.

Actually the 100w discharge limit means it starts at 26V full, and 3.5A, and as the battery voltage drops this increases to 4.4A. The AVERAGE rate over the full discharge is around 3.8A. Close enough to the 3.75A (20 hour rate) for me!

Does that clarify any?

[shirley_hkg]

I mistakenly thought that it were a regenerative discharge .

[Burgerman]

You can do a 70 to 80Ah 12V battery at the 10 hour rate, singularly with just the 100 watt internal discharge capability.
Although a slightly more accurate result is possible over the 20 hour rate. Or two in parallel in 20 hours.

You can do a 24V discharge in series at the 20 hour rate via a chairs XLR port and still at 100w discharge too. Making it simple to properly test an MK battery setup like above without even removing them.

Remember that while the INDUSTRY may refer to the battery pass/fail point being 80 percent of original rated capacity remaining, that may be very noticible to a user. I can detect a 10% reduction in capacity easily. Some users cant tell even if its 50% reduced and completely "buggered"... So its a tool. A very accurate one. To measure how close to the rated capacity (73.6Ah over 20 hours, to 10.8V in MK's case) is to reality.

Now MKs specs say that if charged CORRECTLY and you do not exceed 80% discharge level, then you will get 500 cycles minimum before the capacity falls to 80% of the original rated 73.6Ah.

Charge badly, as all mobility chargers do, or discharge deeper than 80% and all bets are off.

[Seajays]

My Q500 H is 8 months old as a backup chair so I am going to try to get warrantee or I will buy Odyssey.

[Burgerman]

I think you may find odyssey PC1500 wont actually fit. The tops are around 12 or 15mm too wide each side.

[expresso]

they didnt fit my chair 646 when i first tired them years ago - and for the cost - isnt worth it today

we have many options now -

drop in lithium - size is right 100ah is OK enough for many users - bottom line its cheaper than lead today if not a DIY - drop is a not a bad choice -

https://www.ltc-energy.com/Lithtech-TE1 ... 56765.html

[Burgerman]

They will work. But not much of a range increase for considerable cost.