Hi all :)

[Potty]

Hello

Monty from the UK here.

I'm 37 and have used a powerchair for 15 or so years, I can walk a bit with a stick, but range is very limited.

I have an assistance dog in training(though she is almost "there" training wise now) and thanks to her have been able to get out more. (which is mainly why i am here! )

My old Kymco k-activ wheelchair broke (the frame that holds the casters broke) and the replacement part was going to cost almost as much as changing chair, so that is the path I went with. I'm now using a Karma Blazer and it's good, but am finding the range limited, plus seem's to have a bit less torque on inclines. So I'll soon be asking advice on how to change the programming and what I need to learn in order to change to lifepo4 batteries, as that seems like it would maybe solve my range and torque issues, if done right?

I'm fairly good with repairs and computers, so that side of things should be ok, it just feels like a minefield with all the reading so far!

Hope you are all as well as possible

Monty.

[Burgerman]

All that is possible.

A question.
If you need a powerchair to run your life then the NHS can provide this free. Have you tried dealing with them? I know that they need a little bullying to get any kind of action. But its worth a go.

[Potty]

All that is possible.

A question.
If you need a powerchair to run your life then the NHS can provide this free. Have you tried dealing with them? I know that they need a little bullying to get any kind of action. But its worth a go.

Hi Burgerman

I was given a manual wheelchair by the OT years ago, which I assume comes under the NHS, but to be honest in general I try and avoid the NHS/doc's where possible. I find it useful for trips out with a carer, but I can only manage with it on fairly flat ground and shorter distances. I have a telecare system installed by the OT too, it took me almost 6 months of nagging them to get a broken pendant replaced...(typically needed it one time while it was out of action...) so I have not had the bext experiances when it comes to OT/NHS/Council stuff.

I have quite a tight budget, but hopefully can get the batteries sorted. I was looking at the pre-made lifepo4 50ah batteries, but after reading some of your posts, it seems that may not be a great option?

Thanks

[Burgerman]

so I have not had the bext experiances when it comes to OT/NHS/Council stuff.

Thats the socialist NHS.
You have to be on it. Dont let them escape.

Premade battery? Swapping a 50Ah batt for a 50Ah battery? Most wont work, or will keep cutting out or give the same range as lead completely (or almost completely) losing any of the huge advantages that lithium can/should allow. Kind of missing the point completely at greater cost. So not really a good plan even if they worked.

[Potty]

Premade battery? Swapping a 50Ah batt for a 50Ah battery? Most wont work, or will keep cutting out or give the same range as lead completely (or almost completely) losing any of the huge advantages that lithium can/should allow. Kind of missing the point completely at greater cost. So not really a good plan even if they worked.

With my current lead batteries I'm getting about 5-6 miles (50ah Yuasa batteries) before the indicator lights make me return home asap.

I've read a bit about the "group 24" diy batteries, but those would not fit in my chair.

The only other option I have seen that sounds viable, but cannot really find where to start making one, would be a battery "addon" as I understand it, to take with me on the back of the chair.

ideally I'd like the chair to be doing 10+ miles on pretty bumpy ground. (Herefordshire)

I weight around 100kg, so i am not that light!

What would be your suggestion for batteries please? (i'm happy enough to try diy if i can find out what i need to do, as long as it's fairly safe)

Thank you

[Burgerman]

If you were to swap that chair for one with 4 pole motors (draws more Amps at a lower MOTOR voltage and so makes better torque at the same amount of watts, and so lower battery drain, And so much more efficient. And swap it for a chair that can house a 75 to 80Ah lead battery (the so called BCI Group 24 case size, then you can fit 230Ah cells. 8 of them. That will easily give you 100 miles range. Or a 500% gain over 80Ah lead.

But that means a different chair. Possibly by wheelchair services? They are currently providing me a 4 pole, 120A R-Net chair with grp 4 lead bricks. And all fancy electric seating. You weigh about the same as me.

The problem your chair has is:
a) 2 pole motors. This will give much less range on the same Ah. They are uch less efficient.
b) battery space isnt large enough to fit the best size of lithium cells. So it imits you to cells of HALF the capacity that is possible on a grp24 chair.

Now its hard to do a lot about either of these and a change of chair makes more sense.
But you can fit around 120Ah lithium in that smaller battery space. Theres a thread somewhere with shirleyHKG having just done this.

That will give you around 3x what you get now. Why?
Because your current battery only provides 30Ah before the red lights and or it stops. Not 50... Thats because of a frenchman called peukert. An evil little man. Lithium doesent suffer from this problem. So 120Ah would give you 3x the range, you have now, and allow a little in reserve as you really dont want to go too low with lithium... And it runs out with little warning. That will be nowhere near the 100 miles that is possible. Because motors etc. And because small battery space. But its still better than now!

[martin007]

Welcome!

[Potty]

Welcome!

Sorry for the delay, thanks

[Potty]

If you were to swap that chair for one with 4 pole motors (draws more Amps at a lower MOTOR voltage and so makes better torque at the same amount of watts, and so lower battery drain, And so much more efficient. And swap it for a chair that can house a 75 to 80Ah lead battery (the so called BCI Group 24 case size, then you can fit 230Ah cells. 8 of them. That will easily give you 100 miles range. Or a 500% gain over 80Ah lead.

But that means a different chair. Possibly by wheelchair services? They are currently providing me a 4 pole, 120A R-Net chair with grp 4 lead bricks. And all fancy electric seating. You weigh about the same as me.

The problem your chair has is:
a) 2 pole motors. This will give much less range on the same Ah. They are uch less efficient.
b) battery space isnt large enough to fit the best size of lithium cells. So it imits you to cells of HALF the capacity that is possible on a grp24 chair.

Now its hard to do a lot about either of these and a change of chair makes more sense.
But you can fit around 120Ah lithium in that smaller battery space. Theres a thread somewhere with shirleyHKG having just done this.

That will give you around 3x what you get now. Why?
Because your current battery only provides 30Ah before the red lights and or it stops. Not 50... Thats because of a frenchman called peukert. An evil little man. Lithium doesent suffer from this problem. So 120Ah would give you 3x the range, you have now, and allow a little in reserve as you really dont want to go too low with lithium... And it runs out with little warning. That will be nowhere near the 100 miles that is possible. Because motors etc. And because small battery space. But its still better than now!

Thanks and sorry for the long delay!

Eventually trying to go down the lifepo4 120ah diy seems best for me, I've spent a fair bit of time reading up on the diy version, but it's still going to be months before i am able to learn enough about it. (200+ page "how to" threads are hard going on my focus! )

Add on also seemed like a good idea, but would take just as long to learn and I dont like fire much!

My current batteries are worse than I realised and I will need to replace them within a week, as such the only options I see are these:

https://www.ebay.co.uk/itm/175717464845 (50ah lifepo4, so would need new charger too I believe)

https://www.zingbatteries.co.uk/golf-tr ... -ev12-44ex (56ah apparently)

https://www.tayna.co.uk/mobility-batter ... -12-sld-m/ (mk's best option, seems I cant get gel in this size?)

Any thoughts on which to go for please? (or if there is anything else "easy" i could get within about a week)

Thank you very much

[Burgerman]

The lithium one is junk, but cheap. It MIGHT work, but if you value reliability and making it home I wouldnt bother. Main problem is 50Ah and 1C so 50A max current. Your chair can take a fair bit more than double that.
The MK AGM is also junk. MK make great GEL batteries.
The HAZE AGM is much the same. They also make a great GEL version too, that I am using in one of my backup chairs. Albeit in 80Ah grp 24 size.

So if it was up to me, I would run a mile from all 3 of those options. The two lead ones will work ok for a few months. The lithium might give 50% more range, and might suddenly stop (BMS cuts power off suddenly) when you try to climb a slope or something. So I would only try that if I can walk home.

Unless its just as a tempory use for a backup chair. And then I would get the MK probably. But those are about half as good as the gel versions. And the haze and MK gels are both good. If available in that smaller size. I dont know.

Found these HAZE GEL in this size?
https://www.ebay.co.uk/itm/181327273607

Remember that while your mobility charger can charge them. They are gel. So ideally need a lower charge voltage or you lose half of the service life...

[Potty]

The lithium one is junk, but cheap. It MIGHT work, but if you value reliability and making it home I wouldnt bother. Main problem is 50Ah and 1C so 50A max current. Your chair can take a fair bit more than double that.
The MK AGM is also junk. MK make great GEL batteries.
The HAZE AGM is much the same. They also make a great GEL version too, that I am using in one of my backup chairs. Albeit in 80Ah grp 24 size.

So if it was up to me, I would run a mile from all 3 of those options. The two lead ones will work ok for a few months. The lithium might give 50% more range, and might suddenly stop (BMS cuts power off suddenly) when you try to climb a slope or something. So I would only try that if I can walk home.

Unless its just as a tempory use for a backup chair. And then I would get the MK probably. But those are about half as good as the gel versions. And the haze and MK gels are both good. If available in that smaller size. I dont know.

Found these HAZE GEL in this size?
https://www.ebay.co.uk/itm/181327273607

Remember that while your mobility charger can charge them. They are gel. So ideally need a lower charge voltage or you lose half of the service life...

Thanks very much for having a look for me.

As range and reliability are the main things I need, can I ask why the 45ah gel would be better than the 56ah non gel by the same maker?

[Potty]

I have 5 chargers and none of them seem to say the exact voltage they charge at, unless I am missing something?

[Burgerman]

That "24V" that they all show is not the charge voltage. Its a way to describe that it charges a set of 12V lead batteries.

A dead lead battery when your chair shows you a fashing light is around 12.2V each or 24.2V for both when you actually measure it.

The correct CHARGE voltage on an AGM battery is around 14.4 to 14.6V (actually double this for 2 batteries in series so 28.80V to 29.2V) and thats what mosst mobility chargers do. But they are pretty bad at this and they actually wander around, and dont stay at this voltage properly. Then before the battery is properly charged, they stop charging at 14.4 to 14.6V per battery and drop to a lower float voltage that can be 13.3 to 13.8V (it should ideally be 13.6V x2 so 27.2V) indefinitely. At ths point the green ready light is on. But they ARE still charging.

So a gel battery needs a lower voltage, if you are to get the full service ife. That is a MAX of 14.10V per battery. 28.20V and 27.2V float. And almost no mobility charger even get close. So the battery doesent last. They dont anyway if they are too small for the job and yours are. So theres 2 things torturing your batteries.

[Burgerman]

As range and reliability are the main things I need, can I ask why the 45ah gel would be better than the 56ah non gel by the same maker?

Because an AGM battery is great for capacity, (but more Ah does NOT always mean more range as internal resistance is if anything more important) but they offer around half to 2/3rds the cycle life. So you get 350 cycles, from AGM and around 500+ from gel. So in a battery that is very heavily discharged, the gel is the only one that makes any sense.

The deeper you discharge a battery the less cycles it gives. And gels are much better than AGM when it comes to deep cycle discharges.

So if you want it to last, get GEL and charge it CORRECTLY!!!

[Potty]

As range and reliability are the main things I need, can I ask why the 45ah gel would be better than the 56ah non gel by the same maker?

Because an AGM battery is great for capacity, (but more Ah does NOT always mean more range as internal resistance is if anything more important) but they offer around half to 2/3rds the cycle life. So you get 350 cycles, from AGM and around 500+ from gel. So in a battery that is very heavily discharged, the gel is the only one that makes any sense.

The deeper you discharge a battery the less cycles it gives. And gels are much better than AGM when it comes to deep cycle discharges.

So if you want it to last, get GEL and charge it CORRECTLY!!!

Thanks, I basically need them to last until I can get some diy lifepo4 batteries sorted, so I guess 6 months given how slow I am

[Potty]

That "24V" that they all show is not the charge voltage. Its a way to describe that it charges a set of 12V lead batteries.

A dead lead battery when your chair shows you a fashing light is around 12.2V each or 24.2V for both when you actually measure it.

The correct CHARGE voltage on an AGM battery is around 14.4 to 14.6V (actually double this for 2 batteries in series so 28.80V to 29.2V) and thats what mosst mobility chargers do. But they are pretty bad at this and they actually wander around, and dont stay at this voltage properly. Then before the battery is properly charged, they stop charging at 14.4 to 14.6V per battery and drop to a lower float voltage that can be 13.3 to 13.8V (it should ideally be 13.6V x2 so 27.2V) indefinitely. At ths point the green ready light is on. But they ARE still charging.

So a gel battery needs a lower voltage, if you are to get the full service ife. That is a MAX of 14.10V per battery. 28.20V and 27.2V float. And almost no mobility charger even get close. So the battery doesent last. They dont anyway if they are too small for the job and yours are. So theres 2 things torturing your batteries.

I see, so my chargers I assume are all for AGM or we dont know? Seems daft that the chargers don't give more detail on what they are actually designed to do.

[Burgerman]

And range from a lead battery is more to do with the voltage available at the SPEED that we discharge them. An evil frenchman called Peukert discovered that the faster the lead battery is discharged the less Ah it has available. So you actually get a flashing red light or stop moving completely when you have only used about half the rated capacity.

So a 50Ah battery will only provide 25 to 30Ah before you stop.
This is called peukerts law.
Now the actual point that you stop depends the battery voltage which drops like a rock if discharged fast on a battery with a high internal resistance.
Now heres another thing to get your head around.

The perfect battery would have:
high Ah.
Low internal resistance.
High Cycle life.

But every time you increase one of the three, you reduce the other two. So a higher capacity battery in the same sized case, mens that you get reduced cycle life (but gel helps here) and higher impedance.

And the gel traction battery is a better balance if you want decent range as well as a long(er) lifespan (more cycles).

I see, so my chargers I assume are all for AGM or we dont know? Seems daft that the chargers don't give more detail on what they are actually designed to do.

No shit.
This is why all of my own chargers are USER PROGRAMMABLE for lithium, AGM, GEL, and all my hobby stuff. And much bigger than yourchair allows. Batteries that size have no sensible place in a powerchair. Not even an indoor one! I could knacker a set of those in a few hours just in my house. And the deep discharged totals them fast.

[Potty]

And range from a lead battery is more to do with the voltage available at the SPEED that we discharge them. An evil frenchman called Peukert discovered that the faster the lead battery is discharged the less Ah it has available. So you actually get a flashing red light or stop moving completely when you have only used about half the rated capacity.

So a 50Ah battery will only provide 25 to 30Ah before you stop.
This is called peukerts law.
Now the actual point that you stop depends the battery voltage which drops like a rock if discharged fast on a battery with a high internal resistance.
Now heres another thing to get your head around.

The perfect battery would have:
high Ah.
Low internal resistance.
High Cycle life.

But every time you increase one of the three, you reduce the other two. So a higher capacity battery in the same sized case, mens that you get reduced cycle life (but gel helps here) and higher impedance.

And the gel traction battery is a better balance if you want decent range as well as a long(er) lifespan (more cycles).

I see, so my chargers I assume are all for AGM or we dont know? Seems daft that the chargers don't give more detail on what they are actually designed to do.

No shit.
This is why all of my own chargers are USER PROGRAMMABLE for lithium, AGM, GEL, and all my hobby stuff. And much bigger than yourchair allows. Batteries that size have no sensible place in a powerchair. Not even an indoor one! I could knacker a set of those in a few hours just in my house. And the deep discharged totals them fast.

Cheers, makes my little brain hurt trying to understand all this stuff

All the chargers that I look at say they suit AGM and Gel, having trouble finding anything that is gel only

[Burgerman]

Thats the problem.

They dont care. They sell every charger thats cheap and simple with a ad or label that says AGM/GEL but it isnt actually possible. Both are different and have different requirements.

You CAN charge all batteries with the wrong settings, wronge float voltages, wrong CV charge voltage, and undercharge by stopping charge too soon etc and it sort of works.

But it doesent give anything close to the battery service life that you should be able to get.

Let me show you one small graphic from MK who specify 13.8 to a max of 14.1V for their gel battery.

So the perfect voltage (at room temperature) would be 13.85V.
And most charger are for AGM and can be anything up to 14.7V...

[Burgerman]

And UNDERCHARGING which most mobility chargers do, by stopping the charge far too soon causes even more damage! They rapidly become sulfated which likely costs at least as much loss of service life as charging at the wrong voltages.

Then people complain that the bateries lasted 9 months or less in some cases.

The MK can do 500 deep cycles. Or charges. Or it can do 200 quite easily if you dont treat it well. Or less.

But this is life. Knowledge is power. And most people just dont want to know and dont care and then they complain when it all goes bad. Not just batteries, everything!

[Potty]

Thanks again, did not expect even the charger to be a minefield.

Seems like to keep things simple, I should probably just get the mk agm 50ah for now, they are apparently what is supplied with these chairs when they are new anyway. (Mine was used when I got it and had some half dead no name 45ah agm's, swapped them out for my yuasa 50ah, but those are over 11 months old now and i am getting much reduced range)

[martin007]

It's best to buy a quality charger.

[Burgerman]

Non of it is a minefield. But all of it (everything) is complex. Everything in life is really. But nobody wants to learn or know. So in your case your battery lasts 11 months...

Like everything in life, the more you know the better the outcome FOR YOU while you watch all the death and destruction and complaing goingon all around you.

With many things theres a dumbed down answer. Or theres the right answer. They are seldom the same thing.

[Potty]

Non of it is a minefield. But all of it (everything) is complex. Everything in life is really. But nobody wants to learn or know. So in your case your battery lasts 11 months...

Like everything in life, the more you know the better the outcome FOR YOU while you watch all the death and destruction and complaing goingon all around you.

With many things theres a dumbed down answer. Or theres the right answer. They are seldom the same thing.

To be fair, 11+ months seems ok given the price and usage they have had.

As far as I can tell the right answer is the 120ah packs and a pl8 charger, but due to slow learning and logistics(cant seem to find lifepo4 cells or pl8 chargers in the uk O.o ), so I need to make do with dumbed down till I get there.

Oh, one other question please, for charging it seems gel requires fairly stable tempratures, are AGM's more forgiving?

[Burgerman]

AGMs better suit mobiliy chargers. But they have a lower cycle life generally. But with AGMs its imperative that you replace ALL of whats been taken out, and a little extra or they also have a short lifespan.

Look at it like this.

I used to get 9 months befor the stock gel battery in my chairs died. I am a heavy user. Heavy on programing and power, heavy in weight, heavy in that I walked my dog miles daily, and go out ito the town to the pub in an evening. I do more distance than a chair really can with lead. But I didnt care as the NHS replaced them. I fell out with the NHS as they are incompetent and did my own thing.

So I bought BETTER batteries - AGMs that are a LOWER capacity, and super low internal resistance. And I got MORE range. But only a little. Then I killed them even faster. So I decided to fix that.
So I dumped the chairs useless mobility charger. And started using a adjustable power supply, instead. And a heavy cable with anderson connector. Then I charged them at 29.4v (correct for these particular batteries) and I charged them at this voltage until current fell to almost zero (a few mA) overnight. I set this to 40A (to get the bulk of the charge over fast, leaving longer for the slow CV stage to 29.4V @ 20C room temperature to prperly complete. And then I also gave them another charge halfway through the day as I eat/check mail etc. Again at a solid 40A. For say 30 mins or longer. Now, because they had a much lower average depth of discharge due to the mid day boost. And because they were charged properly they were still healthy and almost full capacity 4 years later. I still have them, used in a solar backup battery. I only replaced them because of lithium, and more range.

Knowledge is power. Its not about a specific charger or battery. Its about understanding why you do what you do.

[Potty]

Cheers