Group 24 cells

[swalker]

Burgerman, I agree in principle that bulged or otherwise damaged cells should not be used.

However, the circumstances were:
1. The cells came from China
2. In the US, it is legal (but expensive) to ship damaged cells within the US borders. However, it is illegal to ship them out of the US, including returning them to China
3. The wheelchair the cells were destined for has a large battery box and could accommodate the bulged cells.
4. I tested the cells with the PL8 and each cell had the capacity claimed by the Chinese vendor
5. I would have had to pay a substantial hazardous waste handling feel to dispose of the damaged cells.

So, I installed the bulged cells in the wheelchair and have been using them over over 5 years now. I do not expect them to perform as well or last as long as true grade A new cells.

For the next set of cells, I am only considering vendors that have a US warehouse and will pay the shipping to return damaged or otherwise unacceptable cells to that US warehouse (or other US location). This has drastically limited the selection of cells I am willing to consider.

I continue to look and am hopeful I will find a set of cells from an acceptable vendor that will fit in my Permobil F5.

Steve

[jefferso]

I just had to bite the bullet and order another pair of MK Gels for my Permobil F5 because it will be at least 40 to 60 days until LiFePO4 cells arrive after being ordered and an unknown amount of time before they're all checked and assembled. My new hybrid Permobil batteries were nearly 2 years old and were slowly getting worse. I use the chair mostly around the house, and go out sporadically, but I run them down significantly every day because they run my ventilator. I often charge them a bit in the middle of the day and every night.

I got the pair of MK Gels for £360 (the new Permobil hybrid pair would have been £460). Kind of crazy that 8 160Ah cells, shipped, are $540 (~£435).
The MK Gels are dated 10/23 and both showed 12.91v on a multimeter.

Replacing the Permobil batteries with MK Gel wasn't terrible, but there were a few odd things. The fabric lifting straps from the Permobil batteries did not fit around the MK Gels, the Permobil batteries are definitely a bit smaller. Had to use plastic shipping straps for that, then just tuck in the ends once the MK Gels were in place. They seem to barely fit. The Permobil batteries have slightly recessed terminals. MK Gel doesn't so the top cover scrapes along the rubber cover of the terminals when sliding on. There's almost no room above the batteries in the middle, maybe 1mm if that.
There are 4 hex key bolts to undo to slide out the battery tray in the back. The two in the middle at the top are one size, the bottom ones further out are a smaller size. Why would Permobil do that? Two different sized allen keys required to change batteries?
There was an extra cable to unplug from the back which wasn't on some videos I saw, so when sliding out, keep checking nothing is pulling as it comes out.

The Permobil battery and the MK Gels use a different size bolt for the terminals. Fortunately the right size bolts were included with the MK Gels.

[jefferso]

I asked for details about the 160Ah cells.

"Just to confirm, these are A grade EV cells, correct? And is the capacity and performance guaranteed?"

Docan Power replied:

"The EVE 160Ah is solar grade A cells, not EV grade A. The capacity tested out over 160Ah for sure:"

and this graph was included. Does solar grade mean 1C vs something higher?

[shirley_hkg]

I don't see any incompetence with 1C rated cells in wheelchair, when you have 160Ah in capacity.

They are 3C intermittent, so can handle well with your turn on a dime.

[jefferso]

Docan also writes:

"Do you have BMS already? If not, I will recommend JK B2A8S20P 24V 200A smart Bluetooth BMS for you, unit price is 80USD/each"

[Burgerman]

Well you should ignore that! Those things are OK for the ignorant masses but we can do much better and safer too.

Most of what it does isnt needed or wanted in a wheelchair system. The charging part is better done with a cell balancing charger. But as BMS go it looks like decent quality. In a solar system I would have to use a BMS and then this would be one to consider. With very differently set values to their defaults!

[jefferso]

Docan Power has shipped the cells. Now for a lot of waiting.

"We have shipped the order by sea, Sea shipment, which takes around 40-45days, After Unload and clearance customs, which takes around 10-15days, then the tracking number is going to be online and update the delivery time"

[Scollard]

I need to replace the batteries in my Permobil F5. I would like to go as simple as possible. I have a few questions for the experts.

1. Will a group 24 battery fit in the compartment.
2. Is there any funny business going on between the charge port and the batteries. ie. if I drop in 2 group 24 12V 100aH batteries, can I charge them through the charge port with my Hyperion and an appropriate RCA cable. (Yes, Burgerman, I'll let the crappy battery BMS do its pathetic job)

Strangely, there is a switch on the Permibil charger that you throw if you are putting a non-Permobil AGM battery.

Correct me if I'm wrong. A SLA charge profile will only take a Lithium Battery to 80%. So I can't use the Permobil Charger. But if my Hyperion is set to a LiFePO4 battery without BMS it will fully charge the battery.

For those of you wondering what Battery I'm looking at it's from Alberta Lithium here in Canada.

[daveonwheels]

dont use a premade lithium battery as you will be disapointed in the results. and 100 aH is barely enough

[expresso]

https://www.apexiummall.com/index.php?r ... uct_id=431

[Scollard]

https://www.apexiummall.com/index.php?route=product/product&path=229_234&product_id=431

Hey Expresso. Long time, no talk.

I really don't want to build another pack. And the Permobil is really tightly packed. I don't need the distance of a 230 aH pack. I could go almost 50 miles with my 105 aH pack and my pride scooter. Weight is about the same between my Wheelchair and Scooter. Plus I pretty much drive to where I need to be if it's more than a couple of miles.

I just want to make a RCA cable for my Hyperion to plug into the charge port on the Permobil and pop in 2 group 24 Li batteries.

[expresso]

hi how are you doing Scollard - i was just showing how the costs have come way down since the early days

they have 105ah cells 100ah cells for alot less - its affordable to just about everyone now even if you cant fit 230ah in a chair - 105ah is cheap enough to use abuse them and still lasts years over lead


just another place to look for - i am with you - no need for more cells - how good these are - who knows - but for the cost - worth it - as long as they are brand new and give full Cap. at least - then if they are tightly matched that would be the cherry on top

given the cost - not so sure how good they will be - but they may surprise someone with a nice set for pennies -- if i needed some now - i take the chance -

[shirley_hkg]

Correct me if I'm wrong. A SLA charge profile will only take a Lithium Battery to 80%. So I can't use the Permobil Charger. But if my Hyperion is set to a LiFePO4 battery without BMS it will fully charge the battery.

It's feasible but the balance process , via BMS , involves switching ON / OFF dozen times. Not sure HYPERION will rerestart automatically , so an adjustable power supply is more preferable .

[shirley_hkg]

Also you need to know the specification of the BMS , so to cope with it.

[Scollard]

Also you need to know the specification of the BMS , so to cope with it.

Well, no problem. I can just buy the 12/24V charger they sell that just hooks up to the battery terminals. It was obviously designed to work with those batteries. I'll just need to make a cable for it that terminates in an RCA plug.

[Burgerman]

This:

https://www.ablithium.ca/product/12-v-1 ... e-lifepo4/

100A max discharge, then the BMS chops off power...
Your controller is 120A. per side. So its possible in peak conditions to draw 240A from the battery. Most people dont. Only because they have chairs programed in hovercaft mode, and drive like my gran. So if thats you it MIGHT not cut off power unexpectedly now and again.

If you have a properly programmed chair that responds instantly, and drive it like you stole it, then it will chop off power withing 10 seconds of driving it! For e.g wheelies, or acceleratng up a steep ramp hard are both out of the question. I tested that. And so did poor Nandol in portugal. Who was stranded until rescued many times when using a 100A BMS equiped lead brick replacement. In his Meyra chair. The company eb=nded up disconnecting the BMS inside the battery so it then tortured the cells with too high C rate instead.

So will it work? Well that "depends". It certainly will not work for me, even indoors. Or for say powerchair sport. Will it work for you?

[Scollard]

So will it work? Well that "depends". It certainly will not work for me, even indoors. Or for say powerchair sport. Will it work for you?

I would say it will work. I am more than happy with the stock programming on my chair. Most of the time my wife is walking with me. The only time we go zooming around is if we go for a bike ride. If I really feel the need for speed I'll jump in my Porsche.

So the take away is; Nobody has fit a Group 24 LiFePO4 battery to a Permobil F5. I'll just need to test fit it myself.

Has anyone got the measurements on the Group 24 Permobil battery.

Now does any know if the Charge Port has any funny business between it and the battery. Can I just plug in the appropriate charger for the batteries.

[daveonwheels]

no

[Burgerman]

If I really feel the need for speed I'll jump in my Porsche.

Speed doesent cause high loads. Turning. Curb climbing. And high acceleration at approximately 1/3rd max speed (or accelerating up a slope) is what will put the lights out. If your chair is programmed in a way that it doesent allow you to drive it like you stole it it may never trip out.

I know that the very second I take off at 100% acceleation, the first 10 feet of movement, it would trip. And stop dead. Because I tried it. But most people may only come across this happening as nandol did, while trying to climb a ramp off the road to safety. As he accelerated up, instant stop. It needed to have the battery disconnected and so reset befor he could continue. This happened numerous times while out and about. I also managed to blow the 125A fuse while driving up a steep ramp. And that meant I needed recovery... It takes at least 150 to 200A to blow a 125A fuse. They are rated for up to that for a second or so.

So your mileage may vary. It may work for you. Or the BMS may just decide one day 5 miles in, that a cell wasnt properly balanced and that you must stop. So who knows. The unpredictability of using a BMS for charging and super slow balancing, as well as the max current rating, on top of the limited capacity (you cant use 100Ah as you never know whaen it will cut out so you have to leave 20% in reserve, means its not mch better for range than lead. And it will be less reliable.

But it may be better is you dont run into problems in your specific case.

[Burgerman]

If I really feel the need for speed I'll jump in my Porsche.

Speed doesent cause high loads. Turning. Curb climbing. And high acceleration at approximately 1/3rd max speed (or accelerating up a slope) is what will put the lights out. If your chair is programmed in a way that it doesent allow you to drive it like you stole it it may never trip out.

I know that the very second I take off at 100% acceleation, the first 10 feet of movement, it would trip. And stop dead. Because I tried it. But most people may only come across this happening as nandol did, while trying to climb a ramp off the road to safety. As he accelerated up, instant stop. It needed to have the battery disconnected and so reset befor he could continue. This happened numerous times while out and about. I also managed to blow the 125A fuse while driving up a steep ramp. And that meant I needed recovery... It takes at least 150 to 200A to blow a 125A fuse. They are rated for up to that for a second or so.

So your mileage may vary. It may work for you. Or the BMS may just decide one day 5 miles in, that a cell wasnt properly balanced and that you must stop. So who knows. The unpredictability of using a BMS for charging and super slow balancing, as well as the max current rating, on top of the limited capacity (you cant use 100Ah as you never know whaen it will cut out) so you have to leave 20% in reserve, means its not much better for range than lead. And it will be less reliable. And cost more.

But it may be better is you dont run into problems in your specific case.

[Scollard]

I was reading the Discharge Specifications and the Max Continuous is 100A, but the Peak Discharge is 260A and the Cut-off Current is 300A.

I get it. You just have to monitor them as you go. The charger is pretty small and easy to carry and I can always plug in when I'm back in my wheelchair van. At least with the Bluetooth connection you can monitor your batteries more easily than any home build pack.

[Burgerman]

Peak and cut off mean pulse or something like a short. If that takes as long as it takes to pop the front wheels up in order to climb a curb. Or to accelerate off a road up a street ramp it is called continious. Anything longer than approx half a second. The greater the current the faster it cuts out.

But theres more to it than this. When you have a low current 1C cell, it has a higher internal resistance. Thats why they ARE low C rate. Now the low impedance (resistance) means that the bigger the load (current) the greater the voltage drop is. So as the battery becomes more discharged, the voltage drops lower and lower. But UNDER LOAD it drops significantly and instantly and then the low global voltage BMS safety thing trips in. Or worse the individual cell low voltage trips in. Especially if the cells are not well balanced. Because then the lowest cell drops further, as you try to accelerate or draw a bigger than average load. So now its not the over 100A current that trips you up, but the low voltage limits on a cell level under load as you do something that needs amps! Obviously the becomes more and more likely as the cells discharge.

This is why a larger pack works better. And why NO protection system is wanted in a powerchair as your control system already has all this built in and controls things proportionally. No sudden trip and you stop. It simply reduces pulswidth and throttles back to not exceed the voltage and current limits. Those limits are higher than the BMS in that battery though.

You will likely find all this out in practice! Again, used gently, no BMS problems, and quality battery construction, good BMS programming, and an understanding of what I just said and it MAY work for you used gently. Rolling at high speed is no problem, this is the time that the chair takes the LOWEST amount of current. So it wont stop it rolling at max speed. Its the turning, ramps, and particularly acceleration at low to mid speed (100% pulsewidth) that give heavy battery loads. But while you may think that YOU dont do this, the MOTOR COMPENSATION will be doing exactly this in the background as you use the chair.

I get it. You just have to monitor them as you go.

What will your mnitor tell you? Battery voltage? That wont tell you anything useful.

The charger is pretty small and easy to carry and I can always plug in when I'm back in my wheelchair van.

Its not about range...

At least with the Bluetooth connection you can monitor your batteries more easily than any home build pack.

With a properly charged large pack, the whole point is that it is capable of any amount of current your chair can draw (Amps) and that theres zero need to monitor anything at all for the first 80 miles or so. And the BMS and all its inherrent problems cant trip you up and isnt required.
When charging you can see whats happening on the PC screen. If interested. And its pretty important if you want to study cell health, connections, balance, self discharge, measure capacity in and out accurately etc.

Can you do this with a 100Ah pack and a BMS? Well it will work. In your case. Probably... But you will have lost out on the reasons that we go lithium in the first place. That being incredible battery lifespan, reliability, endless range, fast charge. Charge weekly if you dont do that many miles, (remember cycles are finite so charging weekly means already lasts 7x longer!) And will give you much much more range without going anywhere near the deeply discharged stage. Hence longer lifespan again... And lower average depth of discharge, and lower current draw per Ah, - way below the battery limits also mean longer lifespan. And of course the price... You are paying way more per Ah. For small gains and potential issues and losing out on the benefits. Which is why I always say its a bad idea. But if thats what you wish to do, go for it. If no issues with BMS crop up, you will get about double the range if you ran it dead. But you must keep 20% reserve or it wont last and you wont get home... So maybe you get an additional 80% over lead.

Building a big pack and a 40 or 70A hobby charger isnt for everyone. Thats the best and most reliable bang for the buck though. To do the job right. 5x the range with reserve and many more cycles. And about the same price. Annd they are reliable!

[shirley_hkg]

These 2 figures, one too high the other too low, worried me most.

[Burgerman]

35mA balance?? It will spend forever trying to balance. 1ah out? That means balancing for 29 hours... Actually that 35mA is when its a lot out of balance. It drops off when it gets closer. So who knows how long that would really take. Takes 1 hour on a PL8 hobby charger at 1000mA continuous without exceeding the 3.550v I choose. By proportionally reducing charger power output to maintain correct voltage without repeatedly cutting on/off the charger.

And that high charge cut off voltage means it will repeatedly do that over voltage over and over while its charging. And its charging untill it ends up balanced. So it will be bouncing off that limit for who knows how long...

Will it work? Yes eventually after its cooked the battery every charge. These are just a few more reasons to avoid BMS equiped drop in replacements.

Reconnect voltage also too high. The charger will instantly push it above that 3.75v again. And again.

The reason so many of these BMS systems do this at a too high voltage is because the microscopic balance current isnt adequate. And they rely on overcharge to drag up low cells like a lead battery. Which does a lithium battery no good at all. But otherwise they would likely never get properly balanced at all. Now this is OK for a while when cells are all well matched and new. But at this rate thats not for long. So they soon become harder to balance. And then the excrement hits to rotating air mover.

[ex-Gooserider]

A bit of a trip down memory lane question... Back before Covid I bought a batch of the 15AH cylindrical cells that used to be our best choice... I charged them all but never got a pack built, and they've been sitting since... My ancient lead Odessy knockoffs are finally starting to show their age, and I was wondering about trying to build up these cells into a pack since I have them...

A few questions -
1. What is the minimum voltage I should see if the cells are still good?

2. Granted not ideal, but can I get away with just building the pack w/o doing all the cell balancing stuff that is recommended? I'm not all that worried about time to balance..

ex-Gooserider

[shirley_hkg]

I always assemble them first , balance later.

Set charge volt low (3.48v), for the initial charge.

[jefferso]

Docan Power has shipped the cells. Now for a lot of waiting.

"We have shipped the order by sea, Sea shipment, which takes around 40-45days, After Unload and clearance customs, which takes around 10-15days, then the tracking number is going to be online and update the delivery time"

The 160Ah cells have arrived. I have yet to open the boxes. Is it worth testing each individually? or try to connect everything and do a full charge if all the voltages match?

[Burgerman]

Well at least you coud measure the actual voltages to be sure that none are out of wack or anything. But personally, I woud connect all in parallel, and then either leave them that way for at least 24h, or charge them that way to 3.55V and keep going for at least 1 hour after the voltage reaches this point. Remember that in parallel you are charging a 8x 160Ah battery. So its well over 1000Ah. So if at say 50% full then its going to take a while! Whatever you use.

[jefferso]

The cell came in two boxes. Securely packed with large foam inserts. Opened and checked the cells. They all read 3.299v.
I had an older multimeter and checked with it and they all read 3.288v on the old meter.

So now I can use the bus bars they supplied to connect all the negative terminals together and all the positive terminals together, and leave it for 24 hours to ensure they're all exactly equal, correct?

[Raro]

You already have it, Jefferso I encourage you to illustrate us with photos of the entire process, good luck with it.