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Discussion Starter #1
During the summer I bought a used Toro Workman MDE electric utility vehicle. Overall it has proved remarkably useful around the field, but a week or two back it cut out at the top of the hill while my wife was using it. It was a cold evening and I thought that might have affected the performance of the battery, which had seemed better than feared/expected during the summer, when it was warmer. I was able to restart it after it had sat for a bit and get it moving down the hill - it regenned down the hill, and was then able to power itself a further ~50 metres or so to get close to the field gate before cutting out again. We then towed it round, back to the driveway with the (diesel) Panda. The following morning a friend helped me to push it into the garage, where the charger lives. Unfortunately it doesn't seem to want to recharge. I expect the (old, lead acid) batteries are in poor condition and so I'm looking at options to replace them with a Lithium Ion battery of some sort. I've also had some occasional issues with the controller, usually when the battery was fully charged, giving a "MOSFET short circuit" error. This usually resolved itself on later attempts, usually after running the lights for a while (a few hours).

Anyway, I'm thinking of replacing the lead acid batteries with some form of Li-Ion battery.
Does anyone (@Grumpy-b ?) have any words of wisdom/warnings/suggestions?
The controller on the Workman MDE is apparently a 500A Sevcon, but a report from an Australian with the same system, upgraded to Li-Ion suggests about 300A is actually closer to the likely peak draw: Toro Workman MDE conversion - Endless Sphere

I'm wondering about buying a pre-assembled battery or whether I should try and build one from individual prismatic cells.
e.g. https://www.dhgate.com/product/gtk-waterproof-lithium-48v-150ah-li-ion-battery/512103013.html
or US $1031.1 30% OFF|GRADE A NEW 16PCS 3.2V 105Ah lifepo4 battery CELL 12V 24V 36V 48V 105Ah 100AH for EV RV battery pack diy solar EU US TAX FREE|Rechargeable Batteries| - AliExpress

Anyone have a good source of ex-Leaf cells, and suggestions for suitable BMS/charger?

All practical advice would be greatly appreciated.
 

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Can you use a 12v car replacement battery which has wĺ the bms included?
 

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Discussion Starter #3
Can you use a 12v car replacement battery which has wĺ the bms included?
I guess I probably could, but you'll note the 80Ah comes in at £575 so you're looking at £2300, and I'd have concerns about balancing since you need four of them in series. So a bit of a non-starter, I think.
 

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Discussion Starter #5
Interesting, but I would be concerned whether they would cope with peak draw of about 300A - That's almost 10C. And total of only 33Ah might be a bit on the low side - the standard lead acid battery set is about 200Ah, I believe - so was looking at something around 100Ah for a Li-Ion replacement. And if I were looking at a 4S2P setup of those, you are again getting awfully close to £2k.

Thanks for the suggestions though.

I think I still only have two really viable options: a pre-built 48V "suitcase battery" with built-in BMS, or assembling a battery from LiFePO4 cells of about 100Ah each. Looking into the DIY option, it seems sensible to stick to about 100Ah if building a pack from prismatic cells due to the mechanical environment, as the cells necessarily tend to be less (internally) robust as Ah goes up.
 

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UPDATE: ON MY OWN PROJECT FOR CONVERTING A REVA G-WIZ TO LITHIUM-ION

YOUTUBE here for video updates: Richard Mawby

I have experienced great success in this whole project and it is not difficult for it to work. It has been a near plug and play job apart from the fact that I did not have the in built charger so had to find ways around the in built DC to DC converter. I blew a 25 amp buck converter as I did not realise the regen pumped back into the charge leads that I used to power the converter. For now I have a 12v battery to power the dash whilst I wait to order another one and connect to a separate 48v battery that I can plug in when I need to charge it along with the rest of the packs. Other than that I have been driving it with out problems.

BATTERIES:

I have calculated and found the perfect size batteries to build that will ensure they fit flush into the battery tray and give the max capacity possible in lithium-ion cells. This results in 13s13p packs which measure approx. 26x26x7 cm. You can fit 10 of these in the centre tray and another 8 split between the two side trays.

Maximum capacity: 18 packs of 13s13p.
Maximum ah using 3500 mah cells: 819 ah!

Currently I have 8 fitted (the others are in the process of being made). 8 is the minimum needed to run the car without pulling too many amps out of each pack. I have had these built with fully tested, mostly Sanyo 2200 mah used cells which were around 0.65p per cell! My friend, who builds batteries does harsh tests on them to make sure that they are safe to use with the discharge needed in the G-wiz.

Each pack is built with 169 cells, 8mm 0.15 pure nickel strip, 8 awg wire, 35 amp common port BMS, 1mm G10 fire resistant protection (trying to punch through with a screw driver is difficult with this so plenty of protection for the battery trays), and of course shrink wrap. There are also XT90 connectors so that each battery can be unplugged easily or added to. They also have their own volt meter so that they can be easily monitored. I might protect further with some 1200 celcius fire proof fabric just to be safe.

These were wired up with distribution blocks that take it up to 0 awg for connecting to the controller. See video here:

RANGE TESTING:

Long story short - 35 miles per 100 ah approx.

A potential of 60 mile range based on an 80% discharge with the current 8 packs and a total 218 ah.

A potential of 140 mile range based on an 80% discharge with the complete 18 packs and a total of 500 ah.

CHARGING:

I have bought two custom lithium chargers each programmed to 54 amps at 54.6v max voltage. I will wire these up in parallel to fast charge the complete pack at 108 amps with a conversion to type 2 that can use any 7kw station around the UK (I might try to get a modification so I can use every type 2 service station including tethered).

This will enable me an extra 38 miles per hour of charge whilst out and about with a potential comfortable extra charge of up to 110 miles depending on the day and progress of the journey. This could result in a total daily range of 250 miles with my current set up!

I can also split these chargers so that at home I am charging from one 13 amp socket at 54 amps and at a slower 9 hour charge (based on the full pack of 500 ah).

COSTINGS (these are what I paid and it might vary for others):

G-wiz with a full MOT, service and a custom towbar: £675
18x 13s13p battery packs: £4365
0 awg cable and distribution blocks: £100
2x 54 amp chargers: £740
Type two cable and conversion: £200
TOTAL: £6080

Now although it sounds a lot, the money is mostly in the battery packs that have been built to 27 ah approx. packs which have a great resell-able value for use in e-bikes. Therefore they are not exclusive to the g-wiz and should I move on from this project I can recoup some of the costs. This is also much cheaper than most EV's on the market sacrificing only style and top speed to achieve a similar 140 - 150 mile range. I do not use busy roads so it works for me, but might not work for others.

I have attached an image of various costing approximations based on what combination you might want to go for. It can cost as little as £2700 to convert a G-wiz to lithium ion with a 60 mile range especially if you build the batteries yourself which I would have done if I had the time. Based on using good tested recycled cells, the cost per 100 ah works out the same as buying brand new lead acid batteries at around £1000 per 100 ah.

SUMMARY:

So far the project is a success and I hope to be travelling with the car in the summer months to really test what can be done with the capacity I will have installed. Eventually I aim to build a portable flexi-solar panel array that can give me a modest charge of 20 amps minimum per hour of peak sun so that I am also completely off grid and can travel anywhere. Watch this space for further updates.
Have you looked at the G Wiz thread as it is a similar change from 48v to lithium?
 

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Discussion Starter #9
Well, after a lot of agonising I have spent my money...

I went for a second hand battery module from a 94Ah BMW i3 which should be delivered in the next few days, it's a 12S Li-Ion setup, with peak voltage of 49.2V, notional 44.4V along with a "Chargery" BMS and charger. The module design will hopefully ensure no problems with cell connections (they're all welded) and is pre-wired for a BMS.

Wish me luck!
 

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Discussion Starter #11
The reason I decided to chose the Chargery BMS was because it has an "intelligent" charger (and uses a solid state relay rather than the BMS itself to carry the current, so a 300A (or even 600A) option is quite possible). You tell the BMS what the voltage limits are for your battery cells and let it worry about controlling the charger so it doesn't over-charge. I figured that was likely to be a safer bet than most of the alternatives.
 

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Discussion Starter #13
The charger is separate from the BMS (and is an "off-board" charger), but has a data connection to the BMS so that its output can be controlled appropriately (there's a serial connection between charger and BMS).
 
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