PINNED - Lithium battery conversion/info

[steves1977uk]

I'm still on the look out for alt charger.
You have a PL8 base in the US. We have to send them back to Singapore. Which is not cheap.

I been watching reviews of the latest BMS with Bluetooth and android app.
I may go that way to save money. I can always test each cell every week.

I'd stay well clear of any BMS attached to a powerchair all the time, unless you want your chair to catch fire when a MOSFET fails.

You can ignore us if you choose to and do it your way, but don't say you weren't warned.

Steve

[expresso]

my Bounder has a BMS - so far so good - not saying i would want to make a pack with a BMS myself - -

[Burgerman]

You only think its good. You have no way to know.

[expresso]

thats true - i dont know for sure - i know it works - the chair runs and charges and no indication something is wrong - chair never cut off - etc, but i know what your saying - i wont know - no way for me to know - having my extra 80ah connected - makes sure it dosnt stop if BMS cuts off anyway - i wounldnt know if it did

i am pretty sure the BMS cut off on the 68 mile run - glad i added the 80ah to it

[Burgerman]

But...
Did it cut off (you would have stopped dead in the street without the addon pack) because of one cell low. One cell high impedance so volt dropped under load, or because whole pack reached low voltage limit, or because it was out of balance due to BMS and only the lowest group reached the low point? Or because of overcurrent?

And how do you know that being stored in winter hasnt allowed 1 cell group to be 50Ah lower than the highest? Because then even a full charge will not give time to balance that. So you might stop dead at half distance! Or earlier. And wont see it coming...

My olde cordless drill suddenly ran for about 3 mins after charging. Instead of around an hour. Why? Because one cell was low. Its BMS wasnt doing a good enough job, and so it said charged and gave me a green light around 2 days before it could ever balance the discharged cell. Thats because of uneven self discharge, tiny balance current and a years lack of use. And a dumb charger that cuts off after 30 mins.

But with your addon you are still safe.

[expresso]

I do charge it each month witht the pl8. To keep it balanced best. I can. It let it get low. I had. Flashing 1 2 which would hBe stopped the chair for sure. I am sure there bms is better than most. But still I get it. It gets in the way but will ways have a bms unless u makenit yourself without one

[terry2]

Opps

[shirley_hkg]

Ridiculous ! ! !
Open the last box of the EVE-LF105 lot I bought in April 2019.

Damn. I found two cells at 2.957V & 1.3738V respectively.

I'm afraid that they were going to the bin, as stored at such low volts and prolong period.

I wouldn't throw them away without testing , would I ?

Charge them full, and did a discharge .

Very surprised to find that they are not damaged , but also the strongest 2 ( cell 7&8 ) among the them.
Besides , no significant increase in IR & self-discharge are noticed.

EVE-LF105 cells are good and robust.

Ridiculous !

[shirley_hkg]

[Burgerman]

Damn. I found two cells at 2.957V & 1.3738V respectively.

2.95 I would expect to be OK.
1.37 i would expect has a high self discharge already as it was lower. But also now ruined. I am rather surprized/skeptical! I never got a cell to recover from seriously discharged...

[shirley_hkg]

Down to 3V , and voltages bounce up a bit after 20 minites.

[Burgerman]

Do a 2.9V discharge, but set CV discharge, and set termination to 400mA. And get a truer idea of capacity.

[shirley_hkg]

Using CV mode down to 3V to record capacities of each cell.



Kind of strange !
Cell 7: 102852 mA , previously @ 2.957V
Cell 8: 103024 mA , previously @1.3738V

[Burgerman]

Because of resistance.

[terry2]

Just for fun I contacted revolectrix again about getting my dead one fixed.
They now want to see my revolectrix sales order.

Since I bought it off ebay, I can't do that. So lets see what they do.


Now I know why they don't open a store here.

[stevelawiw]

Sounds like I might need to dust off my "PL8-a-like" design. There's nothing magic about a PL8 if you understand the technology, I've had mine to pieces several times and have reverse engineered large bits of it to understand how it works (so I can fix if it goes wrong). Indeed the design is showing its age with essentially discrete parts for key functions, as there are now chip sets out there for the EV market that can do 400v (96S) and >5 amp balancing per cell, and still only consume <50uA when active (so can be left permanently connected). Obviously expensive but dropping in price all the time as volumes increase, and a plethora of lower end devices that can do 16S and you don't need to use the BMS functions only the monitoring & balance features. The clever bit about the PL8 is the ability to buck/boost on demand (a standard capability of some SMPS chips now - PL8 does its own) and the charge rate throttling when its balancing (still not rocket science).

Yes please! That's what I want

[stevelawiw]

Also, as I'm talking to Revolectrix at the mo with my PL8 in for repair I asked them about it possibly being discontinued, they said not and it should be back in stock early April

[teppic]

I have finally ordered the batteries. As I understand it, in order to maximise the charge capability of my EOS 720i Dual Port Charger, I need to split the 2P8S battery into 2x 2P4S with one on each port in sync mode. Does anyone have any ideas on how I can implement this.

[Burgerman]

Do yourself a favour. Sell that charger. It has numerous issues related to its settings and what you can adjust on large packs, and reliability issues relating to protection circuitry. And it cant natively charge 8S without splitting and isolarting the packs which gets ver complicated and tiring fast.

Buy a PL8 and use some of my own presets that are configured to work properly. Its also got 3x the balance power capability, and can charge at up to 40A which you need with a large pack.

[expresso]

105ah pack - going on 5 years this summer - been sitting all winter - recharged twice all winter


first day out - cant beat headways !!! too bad - just not enough though

[ex-Gooserider]

yes it's the 36in from revolectrix I'm wanting but they always seem to only have one when I want them - which makes them expensive. Scooterman had some advertised but he seems to have disappeared for a while, so I'll make some up but I'm just not sure which plug I need as some people say they are JST-xh some JST-PA and some FMA

Definitely JST, and pretty sure they are the JST-PA series NOT JST-XH (The old Hyperion and most all the small LiPo / LiFe model packs from Hobby Kinky use JST-XH...)

The pins are small and a bit of a PITA to crimp, best affordable tool I've found for ALL the assorted small pins on different brands is a Japanese "Engineer" brand plier - it has different die sets available for it and a 40 page 'application list' of pins it can crimp... Its a bit fiddly to use, but the crimps it makes look like factory...

ex-Gooserider

[Irving]

yes it's the 36in from revolectrix I'm wanting but they always seem to only have one when I want them - which makes them expensive. Scooterman had some advertised but he seems to have disappeared for a while, so I'll make some up but I'm just not sure which plug I need as some people say they are JST-xh some JST-PA and some FMA

Definitely JST, and pretty sure they are the JST-PA series NOT JST-XH (The old Hyperion and most all the small LiPo / LiFe model packs from Hobby Kinky use JST-XH...)

The pins are small and a bit of a PITA to crimp, best affordable tool I've found for ALL the assorted small pins on different brands is a Japanese "Engineer" brand plier - it has different die sets available for it and a 40 page 'application list' of pins it can crimp... Its a bit fiddly to use, but the crimps it makes look like factory...

ex-Gooserider

Definitely JST-PA as per my previous post in this thread.

Part # for cable end:
Housing for female connector: PAP-09V-S
Sockets: SPHD-001T-P0.5 for 26 - 22AWG (1.0-1.5mm OD insulation) or SPHD-002T-P0.5 for 28 - 24AWG (0.9-1.2mm OD insulation)

RS Components
9 way housings 476-6833 £3.80 for 10

jst-PA.pdf

JST-PA Datasheet

(323.48 KiB) Downloaded 231 times

[rickystyx]

Thanks for the info, I did figure it out in the end and got the bits from RS
Sadly they send the crimps as individual items instead of o a strip which is usual which makes them incredibly fiddly to use so I may order some from elsewhere. I managed one lead from midland helicopters so got things up and running they really are silly little connections and I will upgrade to something much more substantial once everything is out of guarantee (or not if everything continues to work nicely)
Never thought I'd go back to doing anything electrical once I had retired - how wrong could I be?

[ICEUK]

Hi all what awg wire size do i need for the balance wires on lilhium pack? Also is 8awg ok for the wiring from the dsub connector?

Thx

[Irving]

Hi all what awg wire size do i need for the balance wires on lilhium pack? Also is 8awg ok for the wiring from the dsub connector?

Thx

20AWG ideally, but not less than 24AWG. You may find 20 hard to get into JST-PA connector. Use 20AWG cable & connect to short ready-made JST-PA 24AWG stub.


8AWG is fine for main charge cable @40A but you may find it hard to get into connector, 10AWG may be easier, 12AWG minimum

[Rye]

Anyone tried a Permobil C350 conversion with a 120 PM? I was looking at trying to fit as many 40152s as I can. How much size do the cell holders add to the overall size?

Rear Battery Box Front battery box
10.5”x8”x9.5” 10.5”x8”x7”

I think I might could free up more box depth and if I remove the tilt mechanism I could add more height. Is there a reasonable limit to how many cells one should use? Charger limits? I assume weight limits?

[Irving]

Anyone tried a Permobil C350 conversion with a 120 PM? I was looking at trying to fit as many 40152s as I can. How much size do the cell holders add to the overall size?

Rear Battery Box Front battery box
10.5”x8”x9.5” 10.5”x8”x7”

I think I might could free up more box depth and if I remove the tilt mechanism I could add more height. Is there a reasonable limit to how many cells one should use? Charger limits? I assume weight limits?

A standard Gp24 73Ah Gel is approx 260mmW x 173mmL x 205mmH (10.5"L x 6.85"W x 8.1"H).

Forget Headway 40152, there are better options now. But for completeness a fully kitted 40152 is 43 x 43 x 183mm plus any protective covering. My 75Ah pack is 40 cells (8S5P), mounted vertical, and inc 3mm protective sheath, is 221W x 350L x 189H (8.7"W x 13.8"L x 7.5"H). Split in 2 that would be 2 off 8.7"W x 7.0"L x 7.5"H. That gives 75Ah. You could just squeeze in 8S6P giving 90Ah at 264mmW (10.4"W).

The newer rectangular 105Ah cells are 130mmW x 37.2mmL x 210mmH, deploying 16 (8S2P) gives 210Ah in a space, with 0.5mm between cells and 2mm protection outside, 265mmW x 306mm x 210mm (10.4" x 12.0" x 8.3")

The only practical limits are space and, assuming standard controllers, voltage. As long as you deploy cells as 8 in series for a nominal 25.6 volts you can put as many as you like in parallel to increase Ah. 8S also mandates a PL8 charger as the only good working option, nothing else comes close.

[foghornleghorn]

I assume weight limits?

You are dealing with the opposite of a weight limit.

Lithium cells are going to weigh less than the lead batteries you are removing. Your centre of gravity will go up and the chair will become more unstable unless you add back some extra ballast weight to the bottom of the battery box.

[ICEUK]

Dont we need a bit of plastic for the batteries to sit on as the battery box is metal

[Irving]

Dont we need a bit of plastic for the batteries to sit on as the battery box is metal

The cells do have an insulating wrap but it's thin. General view is to add 1 - 2mm insulator on 4 sides and bottom of pack. Polycarbonate sheet or similar, or just a few layers of heavy duty vinyl wrap.