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!