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Discussion Starter #1
Hello Everyone!!

I have a REVAi and it got almost 5 year old lead acid battery. It's a 6v 200ah battery 8 numbers making total of 48V 200ah. At present, I'm getting around 30-35km mileage but it's no use for me. So I'm planning to build a lithium ion battery pack for it from the old 18650 cells that I have. My question is:

1. Can I just replace the lead acid battery with lithium ion battery pack ??
2. I'm not getting 300 amp discharge bms for my battery pack so can I go with 200 amp discharge bms for my battery pack ?
3. Will it work if I do this ??
4. Apart from battery change, Any other changes required ?
5. Some people said Canbus thing, What is it ? How it will effect if I only replace the battery keeping the power same ?? ( I'm making 48V 200ah battery pack with 200A discharge rate )


Please... I need your help and guidance.

Thanks
bharath
 

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It is possible, and Reva did actually offer a Li-ion G-wiz briefly, at the end of the model's life in the UK. However it's not simply a case of swapping out the cells, and it's definitely not something to do if you aren't 100% confident. Also you do need to ask if it's worth it. For the cost of you cells you could get a used EV that would be waaaay more capable than the G-wiz. Used Imiev / Ion / C-zeros would be a better bang for your buck, and are not *that* much bigger, but far more practical.
 

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It is possible, and Reva did actually offer a Li-ion G-wiz briefly, at the end of the model's life in the UK. However it's not simply a case of swapping out the cells, and it's definitely not something to do if you aren't 100% confident. Also you do need to ask if it's worth it. For the cost of you cells you could get a used EV that would be waaaay more capable than the G-wiz. Used Imiev / Ion / C-zeros would be a better bang for your buck, and are not *that* much bigger, but far more practical.
Thanks for your quick suggestion. Actually I'm using used cells and I can build around 20kW pack with that. It's a 18650 lithium ion cells. I'm going to use bms for the battery pack. I will definitely swap the battery but I have few questions....

1. Min. current required to run revai ?
2. Will inbuilt charger will work with my new lithium ion pack ?
3. What is Canbus, is it necessary to know this for battery replacement ?

I would like to know what and all changes I have to make if I just replace the lead acid battery with lithium ion.
 

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Hi,
I am about to face the same challange as you

I got a used Reva, dead batteries, and want to use it as a city commuter.
I already have 48V 180aH LiFePo4 cells from another project.

Did you proceed with your project ?
Maybe we can help each other, I got the service manual, CD and software, but of course thats for lead acid.
 

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I think the main problem with Li packs is charging (not over charging) and not discharging too low,they are fragile without proper BMS and charging systems,i would of thought maybe that older NiMh chemistry would be more robust/reliable and manageable,but i am guessing.

Very good luck with what you decide to do,please do keep us informed of your projects and progress.

BR,

S.
 

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Hi Guys. I'm interested in doing this to my 2005 model. In my recent separation from my ex, I got custody of our G-Wiz and she got the Leaf.

I love the G-Wiz but it is obviously limited in terms of range.

I can't really afford a higher range EV at the moment, so I've spent the last couple of days theorising changing it over to Lithium.

My T105 batteries which I replaced when we bought it 4 years ago are fine still, giving a 25 mile range in sub 10 degree weather, and about 32 miles in the summer. Although the batteries are ok at the moment, given that I'm limited as to how far I can go now I'd certainly be interested in doing this.

So I did a few calculations to see how feasible it is cost wise - It looks like you'd need the following...

Existing lead acid G-Wiz batteries = T105 @240Ah (8 batteries in series gives same Ah rating of 240Ah),

Given that with lead acid, you're only using ever using 50% of the actual capacity Ah rating, thus 120Ah.
So theoretically a lithium conversion would almost double your range as the lithium depth of discharge is much lower without damaging the battery (unlike lead acid).

Samsung INR18650-25R 2500 mAh 3.6 V Rechargeable Battery (Pack of 4) | eBay

4 batteries = £24 = £6 each
2.5Ah @ 3.6v
Which means you'd need 14 batteries in series to achive a similar voltage to a DC G-Wiz like mine = 50.4 volts

To achieve the original capacity of 240Ah like the original Trojan T-125 batteries, then you'd need

240Ah = 96 x 14 batteries = 1,344 batteries

I haven't done any size calculations on whether 1,344 batteries would actually fit in the car though!

Cost: approx £8,064
plus copper bars and a charger / BMS of course.

Ouch. Can't see it being sensible at that price!!!

Of course if you were happy with the original range, you could reduce the cost and halve the pack - bringing the cost down to £4,032 plus charger the car would probably be lighter too, so some additional range would be gained from this, and of course you'd be able to rapid charge.
So obviously the more money you throw at the project the higher the potential range capacity.

The big question is though could the car's original charger be reprogrammed?

I do have all the software but I've never fiddled around with it for obvious reasons - anyone know if its possible?

From what I've seen with our old Leaf, the Lithium charge curve is "flatter", e.g. consistent higher current throughout most of the charging cycle and it only reduces down when it reaches 80%, whereas the lead acid charge curve is more curved gradually, reducing from an initial high of 2.2kw quicker over a shorter time-span in a gradual reducing curve.

What did you work out from your calculations? Did you find any charging solutions?
 

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Hi everybody,

I assume no rocket science tech in the G wiz, so you could buy 1 used eltek or any other telekom charger ~1,5-3kWh (<100 £) . It was designed to charge lithium in the first place.

As for the batteries, I would recommend starting with: 2 Tesla modules (around 2,2k £ both) in series for a Total max voltage = 50v and 10kWh energy. I have used 8 of these modules in my Fiat Panda Elettra. It gives me a max range of 300miles.

Do not forget about BMS, in this particular case I would recommend Orion BMS jr which was designed for up to 16 cells in series. Around 500£. However in my setup I have designed a custom controller which acts as BMS master communicating directly to tesla bms slave boards, ECU, Charge Controller, maintains statistics etc.
 

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Toomba - Sounds brilliant! On that subject have you seen this? Looks like a 24V pack with 15kwh and its own charger for golf carts for £200... Not sure if a BMS is required with this rig, as obviously the charger will sort that out.

Just wondering if 2 of these batteries in series for 48V would give a perfectly adequate 15kwh, which is more useable range than the actual 6kw in the 2005 Wiz once you factor in the 50% state of discharge limit on Lead acid....
£400 seems far too cheap to me though. Surely something here isn't right - what do you think? Am I missing something?

Motocaddy LitePower Lithium 15ah Battery & Charger from american golf
 

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Toomba - Sounds brilliant! On that subject have you seen this? Looks like a 24V pack with 15kwh and its own charger for golf carts for £200... Not sure if a BMS is required with this rig, as obviously the charger will sort that out.

Just wondering if 2 of these batteries in series for 48V would give a perfectly adequate 15kwh, which is more useable range than the actual 6kw in the 2005 Wiz once you factor in the 50% state of discharge limit on Lead acid....
£400 seems far too cheap to me though. Surely something here isn't right - what do you think? Am I missing something?

Motocaddy LitePower Lithium 15ah Battery & Charger from american golf
 

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Toomba - Sounds brilliant! On that subject have you seen this? Looks like a 24V pack with 15kwh and its own charger for golf carts for £200... Not sure if a BMS is required with this rig, as obviously the charger will sort that out.

Just wondering if 2 of these batteries in series for 48V would give a perfectly adequate 15kwh, which is more useable range than the actual 6kw in the 2005 Wiz once you factor in the 50% state of discharge limit on Lead acid....
£400 seems far too cheap to me though. Surely something here isn't right - what do you think? Am I missing something?

Motocaddy LitePower Lithium 15ah Battery & Charger from american golf
That’s 15Ah not 15kwh. 15Ah at 24v is 0.36kwh, so you’d need ten to match the Gwiz lead acid usable capacity.
 

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Hmm.... thats a great link thanks Edd!

I'll have to do a measure up - So being in series to increase the voltage, capacity would remain 4.5kwh for $2000, so potentially less range than the approximate existing 6kw usable capacity.

However given the vast decrease in weight of the Tesla modules:
2 = 50kg

vs the original lead-acid batteries:

8 x Trojan T105 at 28kg = 224kg

Should more than make up for that. Given that its a quarter of the original battery pack weight! Thats almost the loss of the weight of 2 large adult males in the car, so its going to affect range quite a bit I'd say as a guess!

I wonder if the BMS system can be reprogrammed with a different charging "curve"?
 

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Hmm.... thats a great link thanks Edd!

I'll have to do a measure up - So being in series to increase the voltage, capacity would remain 4.5kwh for $2000, so potentially less range than the approximate existing 6kw usable capacity.

However given the vast decrease in weight of the Tesla modules:
2 = 50kg

vs the original lead-acid batteries:

8 x Trojan T105 at 28kg = 224kg

Should more than make up for that. Given that its a quarter of the original battery pack weight! Thats almost the loss of the weight of 2 large adult males in the car, so its going to affect range quite a bit I'd say as a guess!

I wonder if the BMS system can be reprogrammed with a different charging "curve"?
No the Ah rating would remain the same at double the voltage, so you’d get 9kwh.

You’d need a new charger and BMS, lead acid and lithium have very different needs.
 

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Re the BMS. From what I've seen from the charging profile from the G-Wiz (Lead-Acid) vs the Nissan LEAF (Lithium) the difference could easily be programmed. The G-Wiz peaks initially at 2.2kw with a gradual downward slope throughout a normal charge on Lead-Acid. Whereas Lithium is full power until 80% capacity is reached, then it reduces gradually in terms of current until 100%
 

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Nope - the Ah rating remains the same if you wire batteries in series and instead increase the voltage. An improvement in Ah and capacity would only happen if you connected it in parallel and kept it at 24V. Connecting Batteries in Series or Parallel or Both.
Kwh capacity is calculated as voltage * Ah. So a 100Ah 24V battery is 2.4kwh. Wire two of those in series and it’s still 100Ah but 48V, so 4.8kwh.

The problem you’ll have with the BMS is it’ll be a fairly dumb unit monitoring 4*12V strings. For the Tesla packs you need something looking for high and low voltage and temperature on 12*3.6 Volt strings, which is smart enough to tell the vehicle to stop if any string goes too low, and stop the charger if any string goes too high.
 

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Keep the lead acid and have 4 x lithium packs which tops up the lead via 4 x dc-dc boost converters at 12v each? Not the most efficient but would be simpler to implement.
 
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