60ah ADD ON build with Pictures

[greybeard]

Spent some time searching Ali Express. & now confused by the range of prices for what look to be similar cells. I think I need 8 x 45, 50 or maybe even 60AH cells depending on best price, for a 2 cell deep pack I intend to mount on the back of my Puma 40, probably in a bag or other suitable container. I also have an Invacare TDX. I will connect to the chair via Andersons I have already. Ideally I'd like to be able to swap the pack on to the TDX from time to time as needed but the Puma will get the most outdoor use. Pics of the chairs below.

All the prices I have found so far are 3 times that quoted by Shirley earlier in this thread (CALB 60Ah cell @£12.50).

Obviously I would prefer to order via a dealer recommended by a forum member, but price is a priority for me. I don't care if the cells have been used previously as long as they have a decent amount of life left in them (how do you tell?).

As I said in the 30AH pack thread, Shirley has kindly offered to supply all the other kit including the BMS I know will have to be incorporated to accommodate my only charging solution, a dumb 8Amp. I will need some help about what needs connecting to what. I am aware this is not the best way to build a pack, but it is all I can afford and may well see me out before it fails

All advice and suggestions welcomed.

[Burgerman]

Obviously I would prefer to order via a dealer recommended by a forum member, but price is a priority for me. I don't care if the cells have been used previously as long as they have a decent amount of life left in them (how do you tell?).

Lithium isnt lead. They last almost forever if used correctly.
They can be ruined totally, or left in a state of high resistance, or have most ofthe service llife removed if alllowed to go toolow, too high voltage ONCE.
They can have much faster deterioration if stored FULL for long periods. Or stored too hot. Or if they have been used where a pack isnt adequately sized so current too high.

As such, knowing most have been used with a typical BMS then I wouldnt touch used cells even if they were 1/4 the price. You might get lucky. But ask yourself why they are for sale.

[greybeard]

I think I meant new old stock. Brain scrambled this afternoon!

[greybeard]

To avoid any confusion, below is my original post from the Expresso's 30ah addon thread. Please post any advice etc in this (60ah) thread. Thanks.

I need some help guys.
My wife just had a spell in hospital and this has made me realise that many of the day to day things I should have been able to manage for myself have become impossible because the chair has lacked the range needed. I need to make an add on pack.

Problems:
I only have dumb 8amp chargers. The charging method needs to be via XLR socket.
I lack the funds for a power supply.
I lack the funds for a PL8.
I am 76 years old and have difficulty understanding and retaining the build information in the lithium build threads even though I read them religiously.
My hands shake too much for reliable soldering, not helped by lacking acute vision in one eye (no parallax for judging distances)

I would be grateful if you could all give me the benefit of your expertise and advise me the best way forward, eg what batteries would be best to give me a usable extra 30 or 40AH over my grp 34 batteries? (grp 24 will not fit in either of my chairs). What is the best place to order them from?

I understand that I will have to incorporate a BMS because of the only charging method open to me. At my age the shorter battery life is not a significant problem.

Shirley has kindly offered to source all the other parts required.

Thanks in advance.

[flagman1776]

To avoid any confusion, below is my original post from the Expresso's 30ah addon thread. Please post any advice etc in this (60ah) thread. Thanks.

I need some help guys.
My wife just had a spell in hospital and this has made me realise that many of the day to day things I should have been able to manage for myself have become impossible because the chair has lacked the range needed. I need to make an add on pack.

Problems:
I only have dumb 8amp chargers. The charging method needs to be via XLR socket.
I lack the funds for a power supply.
I lack the funds for a PL8.
I am 76 years old and have difficulty understanding and retaining the build information in the lithium build threads even though I read them religiously.
My hands shake too much for reliable soldering, not helped by lacking acute vision in one eye (no parallax for judging distances)

I would be grateful if you could all give me the benefit of your expertise and advise me the best way forward, eg what batteries would be best to give me a usable extra 30 or 40AH over my grp 34 batteries? (grp 24 will not fit in either of my chairs). What is the best place to order them from?

I understand that I will have to incorporate a BMS because of the only charging method open to me. At my age the shorter battery life is not a significant problem.

Shirley has kindly offered to source all the other parts required.

Thanks in advance.

Here's the problem... one 8ah charger working through the XLR socket isn't enough to charge an add-on AND your in-chair lead batteries during an overnight charging if left connected. It's just not enough output. You could separate the add-on from the chair electrically... unplug one Anderson SB50 plug... and use a second charger to charge the add-on. Do you have enough hand strength to do this? Maybe someone can think of another way to disconnect the 2 batteries.

[greybeard]

Here's the problem... one 8ah charger working through the XLR socket isn't enough to charge an add-on AND your in-chair lead batteries during an overnight charging if left connected. It's just not enough output. You could separate the add-on from the chair electrically... unplug one Anderson SB50 plug... and use a second charger to charge the add-on. Do you have enough hand strength to do this? Maybe someone can think of another way to disconnect the 2 batteries.

I understood that an 8 amp charger was able to do this from Shirley's post - here: viewtopic.php?f=2&t=8492. I know the battery chemistry is different and not recommended by everyone, but I'm not too bothered by that. As Shirley points out, we are surrounded and in close proximity to more dangerous cells than Lifepo4a every day without incident. I'll not be sitting on the pack and in an emergency could dive off the chair. It wouldn't be pretty but do-able. Obviously I would prefer the safer option of Lifepo4s but if it's the only way to succeed, I'll use whatever chemistry works.

Yes, I could disconnect the pack from the chair and use two chargers. But wouldn't that risk the packs being out of sync - or would that not matter? And yes, I do have the hand strength necessary to manage Anderson SB50s OK.
Thanks for your input.

[flagman1776]

The battery chemistry does not matter. Expresso has succesfully added LiFePO4 packs to primarily lead powered chairs. What matters is the voltages are matched correctly. But if your range is the issue, adding more power will take you further each day. BUT a single low powered charger won't be able to recharge overnight. Switching chairs, alternating days, would give you more charge time, but the chargers are just too small. The only real answer is a faster charger.

[greybeard]

The only real answer is a faster charger.

What minimum AH output would you suggest I need for a dumb charger capable of charging addon and chair together?

[Burgerman]

If you are planning on using a BMS it gets a bit complicated. And it depends on a bunch of complex things that nobody can know. For e.g what exactly does the BMS do? Every one if a bit different. What exactly does the mobility charger do? Again, I never saw 2 that came close to doing what you would expect them to do. And how these two randome things work together.

Its not so much about charger Amp power. Its about what each thing does when actually charging. So what you are planning on doing may or may not work at all, may cut off before cells are fully balanced, or before the lead is charged properly, or work OK. Nobody knows...

Some simple relevant questions.
What is the CV voltage of the charger? And does it do this in a stable fashion. Many dumb chargers certainly do not!
What is the method of termination? Is it time? Or some arbitrary current point reached? Because ideally it needs to be 500th of the leads Ah, and around 300th of the lithiums Ah. Added together. Or a time limited 4Hours at CV or both, whichever occurs sooner.
At what voltage will the BMS begin balancing? Does it continue after charge? If so it will require a longer CV or the lead battery will be pulled down lower after charge ends. And it may not balance at all if balance current is too low or starts too soon. Does the BMS end charge when the balance ends, or when current is low and at what point?
What decides on the BMS when the pack is balanced? And does it then continue at CV or cut off the charger?

And heres a graph from a typical mobility charger (from a member here) MONITORED by the PL8 we use.
Ignore the red, thats all wrong. This should show rock steady CV volts!!! The balance or BMS wouldnt work properly or at all if your charger does this!

ALL WRONG!!!

This is what a GOOD charger (the PL8 itself for e.g.) and the one above SHOULD do. This is a PL8 charging correctly at the right stable voltage, and at the CORRECT voltage as set.

PL8 charge.
THIS would allow the BMS to "work" and correctly end and terminate the charge for lead at least.

So will a BMS work??
It might. Or it might not. They are awful things, doing the wrong thing in the wrong place.
So will a dumb charger work?
It might. Or it might just not allow the (crappy) BMS to do its thing.
So will they work together?
They might. In a fashion. If you are lucky. Frankly I think its a great way to get problems and ruin the lead and the lithium fast!
But you MAY be lucky.

How many Amps?
The BMS may limit this, read the specs. Otherwise 12 would work safely, as long as you have adequate time. And connect via the XLR. Or 25 would be a better figure via an Anderson connector.

I really wish you luck. I wouldnt do it, but if the charger is doing the right thing, and the BMS gets along with it, you might get away with it. Its all guesswork unless you measure and monitor things.

[shirley_hkg]

greybeard made himself clear that he is soon going 80 with shaking hands. He has tight budget .However , he thinks and speaks laud and clear . He wants to extend the chair's range for A DAY . He is not going like a stupid haund chasing fallen leaves sweeping by gust of wind 40 miles A day.

He is not bothering the pack would last 15 years or not .

He wanted to clone my Ultimate add-on for dummy .
I explained to him that a 60A LiFePO4 add-on suits him most . He can use his dumb charger too.

My battery guy can send him a assembled 60A pack , but the £7/kg shipping quote will be a burden .

May be you can help him to source 8 cells economically , so he can get what he wants.

[Burgerman]

I cant buy cells any cheaper than by ordering from you. Which is why I will be doing this for my own salsa chair.

And then we have the BMS thing/wiring issues that I am not sure he can do himself. The best way to do this would be for your battery guy to ship him a ready built/bms pack. Or risk the chinese auction site lottery with a ready built BMS pack. Such as these. https://www.alibaba.com/showroom/24v-40 ... -pack.html but then we have no way of knowing if they are going to be any good.

I have little experience with ready made packs, other than bad experiences with lifepo4/bms setups. As soon as you get involved with a BMS it complicates wiring, and charging. I do not want to send a link to something that I dont think or know will work properly, or be reliable. I have seen too many BMS issues.

So am at a loss as to what to recommend because I dont know what will work. I also think that 60Ah is too big for hanging on the back of a chair. And that less would likely be better. And that it makes more sense to swap out the lead instead for many reasons including simplicity. So I think the best option IS for your battery guy to build an addon pack we know should work. And it will still be cheaper than anything I could get anyway.

So I think your battery guys 60Ah (or a 40Ah? so its lighter, he is almost 80) IS the best known quantity solution that will be the most likely to end well.

[shirley_hkg]

Actually , I'm calling ALL you guys' help .

He doesn't need to solder . I'll send him all the wires and lugs ready . He then follows Expresso's steps to connect everything together, and done .

I'll send him a small 3.65V power module , powered from chair's lead bricks , to do individual cell balance safely .

May be a few Schottky diodes in the power lines to suit his charger .

Doesn't sound complicated , does it ?

[Burgerman]

Yep! Not to me. Not to you. But to him!

I'll send him a small 3.65V power module , powered from chair's lead bricks , to do individual cell balance safely .

Not to mention that THIS wont work. Because you need all cells at 3.5V or higher to balance lifepo4 cells. Trying to use the packs own power to balance itself will end up with a battery under 3.5v per cell, and so will likely UNBALANCE the pack for many hours.

[LROBBINS]

Shirley said that the balancer will be powered from the lead batts, not from the LiFePO4.

[Burgerman]

It cant be. They are connected in parallel. And the lead resting voltage OFF charge is lower than the LiFePO4 once charge ends. It is this that allows a 4 hour CV we set in the PL8 to properly charge the lead post termination. Because the lithium voltage "float" charges the lead after lithium charge/balance completes at 3.5V to 3.6V per cell charge depending on AGM or gel lead battery. All this is dead easy to achieve, with the PL8. But god only knows what will happen with a typical mobility charger, and then relying on a decreasing voltage to run a lithium balancer.

If you set balance to stop at 3.5 to 3.55V then balance ends in seconds after the charger stops.
If you set to lower than 3.45V then NO balancing, and in fact potential UNbalancing will occur for hours.
If you set it to stop balancing at 3.45V then balance will be a) incorrect and take 6 to 12 hours.

[shirley_hkg]

Lenny is right .

They are disconnected . By using the same plug as that of the LiFe pack , he will be limited to do it my way.

[Burgerman]

What voltage will each cell end up when balanced?
When will charge end? And why?
And what happens to balance when voltage of pack falls?

You are doing this So volts must fall and once below 3.5 volts you are making it worse not better. Which will be almost straight after the charger stops:

[greybeard]

If it helps settle this difference of opinion, I am perfectly willing and capable of disconnecting the pack from the chair and charging each using two separate chargers. Does that help?

[shirley_hkg]

May be my poor English can't tell it right.

The 3.65V module is for primitive balance only, because cells' SOC vary much on arrival.

When you charge it for the first time via BMS installed , you may only see ONE led lights up.

Then you use the module to charge the others till they light up one by one . Now all cells are full ,and you only do this once .

Let the BMS do the job during routine use .

[greybeard]

Yep. Got that Shirley. I was questioning whether Flagman's idea about splitting the addon and chair for charging might be a compromise.

Shirley, What is your response to his statement that an 8amp charger does not have high enough output to charge the pack and chair when connected together? I thought your pack for dummies idea was to achieve exactly that.

Ps Your "poor" English is better tham most native Brits!!!

[Dan]

@greybeard What is your budget?

[shirley_hkg]

Sorry to quote your words in pm.

A 60A add-on plus your grp34 lead bricks will deliver a little less than 100Ah at most.
If charged overnight , an 8A charger will get your chair 90% full the next morning. You will finish the rest in the following night . And you have nights after nights , right ? Nevertheless , LiFePO4 doesn't need fully recharged every time, and wouldn't give the lead brick a damn.

Honestly , I doubt you can drain 100Ah in a day. May be you haven't get any clue what 100Ah @24V meant to a wheelchair.
I only put back 80Ah, after a 60km ride with my wife on the piggy trolley behind me all day long .

Reality is , most users here are doing it with their original chargers for a decade.

[greybeard]

Thanks for that reassurance, Shirley. The chair with the addon will be used every day but most days will not exceed 3 or 4 miles. I anticipate the maximum daily mileage is unlikely to be greater than 10 to 12 miles except on very rare occasions. It will be charged every night for around 12 hours and often for longer.

With that in mind would a lower capacity than a 60AH pack be more suitable for me? Say 45 or so? My aim is to make my existing lead bricks last me out and give me the extra range option as described above.

[shirley_hkg]

Yes. 45 is ok, provided you could find good stuff .

[flagman1776]

IF shirley will build it correctly and test it, I'd be happy. Shirley knows what he's doing.

[greybeard]

Yes, Flagman. I will be very happy. You guys all know what you're doing with this stuff. Unlike me.

I suppose that despite reading the lithium threads, because I had made up my mind it was all out of my reach, I didn't properly take much of it in. But I'll get by with a little direction and good suggestions from my clever friends on here. Thanks to everyone who's helping.

[greybeard]

Yes. 45 is ok, provided you could find good stuff .

That's my problem. I need recommendations on a reliable supplier. Anybody ???

[Burgerman]

Its all a matter of luck. In reliability, seller, quality, shipping, packing, import duties, etc. Unless you buy from shirley who can see what you are getting, test a cell etc. I may take a risk, or try something. As do others. You dont want that. I may buy for e.g. from https://www.rj-lithium.com/ or places like it. I have bought from evassemble, for e.g. but they dont have what you want. Most of us have only ever built 2 or 3 packs, so no real idea of sellers reliability.

[greybeard]

@greybeard What is your budget?

Frankly, as little as possible but I could comfortably manage £200 - with an absolute max of say £350 but that would sting a bit.

[greybeard]

Its all a matter of luck. In reliability, seller, quality, etc. Unless you buy from shirley who can see whay you are getting, test a cell etc.

Yes. I would be very happy to buy from Shirley but he's suggested getting them delivered would be cheaper by going to Ali Express. Those Chinese sites confuse the hell out of me! So much choice and so many different prices for what seems identical stock.