PINNED - Lithium battery conversion/info

[stevelawiw]

We haven't sorted out the supply method yet as far as I know. I was saying put me down for 16 if we got together and ordered a pallet from Shirleys supplier, but who would they be delivered to? I'm on th e Isle of Wight, Dan is in Ireland, it's not like we're living next door to each other
Shirley has said he can get 16 105ah batteries for around £500 but postage so far is prohibitive.

[Burgerman]

Shipping is expensive. But...
210Ah of Lithium, with 4000 cycle life, for the cost of a set of MK gels with just 40Ah and about 300 to 500 cycles or a years hard use, with double the weight, much slower charge time, and just a fifth of the range, means that its much more than worthwhile!

[stevelawiw]

What are you in favour of Burgerman, us all doing it as individuals or are you considering the pallet idea?

[foghornleghorn]

Personally I think group purchase on a pallet is a bad idea for a few reasons and there may be more
• Bad feeling amongst everyone if the whole lot disappears into a parcel black hole never to arrive.
• None of us are fit enough to split and repackage the pallet contents to send onwards.
• Got a forklift and somewhere to store it out of the rain? Most pallet delivery is to the kerb.

[Burgerman]

Individuals...

[Irving]

Here is a mock up of a 16 cell 210Ah pack using the Shirley cells. Wired 8S2P

Worst case dimensions, allowing for tolerances & using 0.5mm polycarbonate sheet insulation, are 302.1 L x 262.5 W x 208 H (inc M4 allen bolt heads and 2 x ring terminal). Compare that with 2 x MK 74Ah gel with spacers as per LH Puma diagram below is 352 L x 270 W x 210 H (inc M6 allen bolt head and ring terminal)

[stevelawiw]

I really, really want one of those....

[Irving]

Wiring:

[foghornleghorn]

A real costs comparison rather than the usual claim of being similar to 2x MK Gels @ £500 delivered.

I'm not trying to put anyone off. If you can afford it, do it. The conversion has given me a lot more freedom to go out and not worry about the chair expiring before I do. Just giving an idea of how much money you will need to scrape together before you are set up and driving.


16x of the 90Ah cells was £890 to my door including all fees.
PL8 and some leads £250 by the time HMRC had their slice too.
Around another £180 on bits and bobs.
We already had soldering and crimping equipment covered but you may need an iron, etc.
Had to have a new battery box welded up. Cost to me £0 as my dad did it from stuff he already had, but factor that in if your measurements turn out to be too tight.
Insulation material. Also came from the stuff my dad already had but whatever you order won't be free.
£50 worth of lead to go at bottom of chair and restore centre of gravity as cells lighter than batteries.
Power supply - no idea it was also from the stuff my dad already had.

[Burgerman]

16x of the 90Ah cells was £890 to my door including all fees.
PL8 and some leads £250 by the time HMRC had their slice too.
Around another £180 on bits and bobs.

Remember that the low power crappy mobility chargers are around that price or higher when you buy the chair though. But yes you do need a charger.

We already had soldering and crimping equipment covered but you may need an iron, etc.
Had to have a new battery box welded up. Cost to me £0 as my dad did it from stuff he already had, but factor that in if your measurements turn out to be too tight.

That wont apply to others though?

Insulation material. Also came from the stuff my dad already had but whatever you order won't be free.
£50 worth of lead to go at bottom of chair and restore centre of gravity as cells lighter than batteries.
Power supply - no idea it was also from the stuff my dad already had.

No lead on any of my chairs, but WILL use lead on the salsa because of heavy seating.
Power supply, best bet one of shirleys, cheap, 50A capable. Although theres other options. But yes there are a few other minor expenses, and stuff to add. But still its massively cheaper long term, even if you ignore the fact that you are buying 10 gallons of fuel instead of 2 galls.

[steves1977uk]

PL8 and some leads £250 by the time HMRC had their slice too.
Around another £180 on bits and bobs.
We already had soldering and crimping equipment covered but you may need an iron, etc.
Had to have a new battery box welded up. Cost to me £0 as my dad did it from stuff he already had, but factor that in if your measurements turn out to be too tight.
Insulation material. Also came from the stuff my dad already had but whatever you order won't be free.
£50 worth of lead to go at bottom of chair and restore centre of gravity as cells lighter than batteries.
Power supply - no idea it was also from the stuff my dad already had.

Already have most of this stuff anyway, so I'd only need the cells. I've got so much stuff, it'd take me ages to list it all!

Steve

[Gnomatic]

£50 worth of lead to go at bottom of chair and restore centre of gravity as cells lighter than batteries.

I did the same thing in my chair converted to lithium - tossed a couple metal plates, combined 1" thick, below my lithium pack with a good amount of insulation in between. The plates + pack weigh a bit more than a pair of MK G24's. So the center of gravity is even lower than stock.

[Dan]

I asked them about any import duty and busbars.

Yes, including all import duties
Alibaba Translation
包含busbars和螺丝

Including busbars and screws
Alibaba Translation
UPS运输，通常12-18天运输完成
UPS transportation, usually completed in 12-18 days

2019 NEW 16PCS 3.2V 100Ah lifepo4 battery CELL 12V 24V36V 48V 105Ah for EV RV battery pack.
https://www.aliexpress.com/item/33054219276.html

[shirley_hkg]

It is a good price you've found.

Won't need those bus bars & bolts.

Use what I posted here before.

And here is the real things, in page 163 of this thread.

[Dan]

It is a good price you've found.

Won't need those bus bars & bolts.

Use what I posted here before.

And here is the real things, in page 163 of this thread.

I'm not so sure the price is that great BUT than again the pound is quite weak at the minute.

OK no busbars but rather;
Crimped cables
M4 stainless steel studs bar with Loctite 2700
Stainless steel nyloc nuts
1MM A4 perspex sheet acrylic panels

[Irving]

It is a good price you've found.

Won't need those bus bars & bolts.

Use what I posted here before.

And here is the real things, in page 163 of this thread.

I'm not so sure the price is that great BUT than again the pound is quite weak at the minute.

OK no busbars but rather;
Crimped cables
M4 stainless steel studs bar with Loctite 2700
Stainless steel nyloc nuts

It's a PITA that the pounds taken a bit of a beating at the moment, but considering a new set of mk 74Ah is around £465 delivered at the moment and for me they'd have a service life of 18mo max, so over 3y Inc inflation @ 2.5% I'm looking at 3 sets of batteries @ an outlay of nearly £1500, so £1200 now with a 10y life span still looks a good deal

[stevelawiw]

Plus having approx 4 times the range.....

[Dan]

£1200 now with a 10y life span still looks a good deal

And the greater range they would give to the chair plus they would probably outlive me!
Thanks a lot for the wiring diagram it helped a lot. And Shirley's picture.

[Burgerman]

I'm not so sure the price is that great BUT than again the pound is quite weak at the minute.

No, but consider this

You are comparing different things. You would need 5 SETS of MK batteries, so 10 of them, to have an equivelent aount of range/fuel. How much is 5 sets of MKs going to cost? Thats 10x GRP24 73Ah gels. To compare the COST fairly you would price up the same usable capacity. Or you are comparing 2 gallons to 10 gallons of fuel.

Set of MKs, gives 35 to 40Ah max before you stop due to voltage depression/peukert etc. How much? Maybe 500 delivered.
So the correct comparison, would be 8x 40Ah LiFePO4, which will give the same range ignoring all the other benefits.
Maybe 20 dollars at most plus delivery. Quick look on alibaba shows 9 to 18 dollars depending on quantity of the first ones I clicked on...
Lets double that price for giggles. Now its 320 delivered. Already cheaper by far than MK lead.

[Irving]

An alternative, and arguably neater, wiring scheme.

[foghornleghorn]

Where do your standard battery wires from the wheelchairs brain arrive at the batteries?

Will you be wanting to connect them in the same position, or are you making up new battery to brain wires in addition to the cell connecting wires?

[Irving]

Mine arrive/leave in the middle, but they are so long they could go anywhere. it's not hard to come up with other arrangements... there's only a few ways 2 x 12v batts can be wired together!

[Irving]

Here's one that replicates standard Puma wiring layout

edit: forgot to show the cell + poles but its not hard to work out.

[Dan]

An alternative, and arguably neater, wiring scheme.

Basically you are putting two cells in parallel to make one 3V cell than put 4 of those in series to give you a 12V battery. Do the same with the other cells and you than have two identical 12V batteries which you then put in series. Giving you your 24V.

[Scooterman]

Internal Resistance is a good indicator of how good the connections are.

Do you bother checking it?

I rarely charge with the laptop connected as it ties up the laptop for a few hours.

I just use shirley's PSU and the PL8.

When charging I do check the IR on the PL8.

For those of you who've had lithium installed for a while is there an IR reading that the cells should stayed below?

For example 5 milli-ohm?

The larger cell specs usually state a cell value of say 0.5 milli-ohm.

Just curious...

[Irving]

Internal Resistance is a good indicator of how good the connections are.

Do you bother checking it?

I rarely charge with the laptop connected as it ties up the laptop for a few hours.

I just use shirley's PSU and the PL8.

When charging I do check the IR on the PL8.

For those of you who've had lithium installed for a while is there an IR reading that the cells should stayed below?

For example 5 milli-ohm?

The larger cell specs usually state a cell value of say 0.5 milli-ohm.

Just curious...

IR will vary with SOC and cell age/cycles. It's highest when SOC low, drops to its lowest between 30 and 90% SOC and rises slightly at 100%. As cells age the curve remains the same shape but the IR rises overall. So as long as you track across the whole charging cycle a step change in IR might indicate a connection issue.

[Scooterman]

Got it!

Thank you for that, a good explanation

[saker98]

Hi everybody,

I got this quote; questions, are these ok and is the “c” rate ok.

3.2V 105Ah
Size : 201x131x37.2mm
Weight : 2.05kgs
Cell rate : 3C
4PCS/Carton=10KGS
Total : 45KGS

Cell cost : USD62.00/PC for 18PCS 3.2V 105Ah (battery cost : USD1116.00)
Shipping cost : USD350.00
So total : USD1466.00


Price include shipping cost and customs fees,you don't need to pay any fees again .
Shipping : UPS take around 7-14 days from CN to your door in UK.

Certifications for cells : CE RoHS MSDS UN38.3 .

Irving: nice diagrams.

Regards
James

[Dan]

3.2V 105Ah
Size : 201x131x37.2mm
Weight : 2.05kgs
Cell rate : 3C

Is that 3C a Maximum Pulse Discharging Current? The ones I was looking have a Max Continuous Discharge Current:105A(1C) Internal impedance:0.1~0.3mΩ. I'm not sure if that is good enough?

[Irving]

James,

Are they these ones?
https://m.aliexpress.com/item/33054219276.html

In a 8s2p configuration that's 210A continuous, 600A pulse. Which should be fine.

Today's Ali express price delivered is £1128 for 16 cells so if that's for 18 that's a good price (£1178 @ MasterCard fx rate) but check your conversion rate us$ to gbp. Better to get vendor to quote in gbp.