DonDakin
Posts: 376
Joined: Wed Aug 15, 2012 7:10 pm

Future battery replacement

Fri Mar 28, 2014 3:15 pm

Hey all,

I've been thinking about the i's range and I got to looking at the lev50 battery spec. With its dimensions it could be replaced with a set or 18650 cells in parallel. Doing some conservative volume calculations I could see 30 of the new Panasonic 3.1 ah cells making a great replacement battery cell. They would need to be built in modules with little fuses a la tesla and could be drop in replacements for the lev 50.

If you look at weight and power 30x 18650 cells would give a 93 ah battery weighing 1.2 kg about 30 % lighter and almost double the range. It would be 2640 cells total. I could see them being $3 a cell in the future maybe even less. That would be $8000 in cells for a really nice battery of 30kwh and a car with an easy 200 km of range.

Maybe I should start soldering cells together in 5-6 years as I plan for my battery death.

What do you think ?

Don.....

Malm
Posts: 447
Joined: Mon Jul 22, 2013 12:16 pm
Location: Tábua - Portugal

Re: Future battery replacement

Fri Mar 28, 2014 3:52 pm

Yes. 16 kWh I-MiEV will be a joke in some years, no doubt about that.
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.

PV1
Site Moderator
Posts: 2846
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA
Contact: Website

Re: Future battery replacement

Sat Mar 29, 2014 5:37 am

Neat idea. Do you know what the charge and discharge rates are on the Panasonic's?

If Ben Nelson still has the flooded i-MiEV, this information could help him (and other's with dead packs) get the car under its own power, or help some of us make a killer BRE (battery range-extender).
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

Barbagris
Posts: 225
Joined: Wed Feb 20, 2013 8:34 am
Location: Bilbao, Spain

Re: Future battery replacement

Sat Mar 29, 2014 10:34 am

Sometimes I play with that idea.
Often to replace a damaged cell, but it could be for the whole pack.
$ 3 / cell? I think we should go to recognized quality manufacturers (Panasonic, as Tesla?), we can not think of thousands of cells and 1-2% fail.
...learning...

JoeS
Site Moderator
Posts: 3178
Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: Future battery replacement

Sat Mar 29, 2014 11:40 am

Having just completed a Lithium (NMC) installation into my second Sparrow - that's the easy part - just a packaging and wiring exercise.

The more significant issue I see with doing anything with the i-MiEV is to figure out how to either integrate with its existing BMU or else fool the BMU into thinking everything is ok and have a completely separate Battery Management System.

As an aside, my own homebrew Lithium Sparrow QuickCharge consists of nothing more than simply adding a whole bunch of benchtop chargers and power supplies (both 120vac and 240vac) in parallel when needed to recharge quickly, with both timers and HV shutdown should I get distracted.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
Site Moderator
Posts: 2433
Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

Re: Future battery replacement

Sat Mar 29, 2014 1:03 pm

JoeS wrote:The more significant issue I see with doing anything with the i-MiEV is to figure out how to either integrate with its existing BMU or else fool the BMU into thinking everything is ok and have a completely separate Battery Management System.
I agree. I wouldn't be interested in spending $8K on a battery pack unless it came with a pretty foolproof BMU. If it didn't, I'd rather spend my $$$ on another OEM set from Mitsu

While the extended range would be nice, the most important thing would be protecting my investment

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1994 Miata 60K miles - Soon to be sold
1979 Honda CBX six into six

DonDakin
Posts: 376
Joined: Wed Aug 15, 2012 7:10 pm

Re: Future battery replacement

Sun Mar 30, 2014 7:16 am

Hi all,

The idea was to use the existing Bms in the imiev. I thought you would be able to build a lev50 replacement out of 18650 cells. If you can package it in the same form factor then it's drop in replacement.

I don't know what the maximum C rating is on these cells. I read that you could get 6 amps out of the cell no problem. With 30 cells that would be 180 amps which should be plenty.

This might be a good idea for single cell replacement also. That might be a good proof of concept for doing a complete battery.

Don.....

PV1
Site Moderator
Posts: 2846
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA
Contact: Website

Re: Future battery replacement

Sun Mar 30, 2014 8:38 am

As far as the BMS handling the new cells, as long as the voltage range covers the car's voltage range, they should work. The i-MiEV charges the cells to 4.1 volts per cell, though I'm not sure where it bottoms out before shutting down. The new cells should have a very similar charge/discharge curve, and the voltage range for most lithium batteries is quite similar, so the car shouldn't see much of a difference between LEV50 cells and bricks of 18650's, except that the new cells can take on more energy. I would be interested to see how the car would handle having much more storage available and trying to access it.

As for replacing one or two LEV50's with 18650's, you may run into problems doing that. I would expect to see the same symptoms as having bad cells in an OEM pack. A total replacement, however, should work out OK, unless there's a secret kWh counter built-in.

I've read that continuous C ratings on prismatic LiFePO4 batteries is 3C, with a burst rating of 10C. 6 amps on the 18650's would be 2C, 30 cells in parallel is 180 amps as Don stated. So for the whole pack, 180 amps at 360 volts is 64.8 kW, more than plenty for the i-MiEV. Even at 330 volts, that's 59.4 kW, still more than the i-MiEV requires. The LEV50 cells hit 3C at full acceleration.

The battery pack would be increased from 50 Ah (16 kWh) to 93 Ah (29.8 kWh), for a range increase from 62 miles to 115 miles per charge.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

DonDakin
Posts: 376
Joined: Wed Aug 15, 2012 7:10 pm

Re: Future battery replacement

Sun Mar 30, 2014 6:37 pm

Hey PV1

That's how I see it.

As for replacing one cell, the bms would see one large capacity cell on charging I would see the bms bringing this cell up to 4.1 volts.

On discharge this cell would have a higher voltage then the other one and would stand out n the readings. The bms would count amps as it discharges and make its usual decisions until it thinks the pack is at 10% then you turtle down to 5% then you stop. In reality only of the batteries would be about 50 % then you charge and repeat.

I could see problems if the bms sees a rogue battery with higher voltage but I suspect this will happen to all our cells as they age. Malm has a few low capacity cells and his bms deals with it bringing the capacity down to the weakest cell.

I could also see a problem if you did a complete replacement and the pack had a much higher capacity. The battery gauge might go to turtle and then stop even if there was 40% left on the cells. It would not be good if you could not use the whole cell.

I don't know if it would continue in turtle until one cell hit 2.75 volts. If so that would be a long turtle ride.....

It would be nice if the bms learned the capacity of the pack and rescaled the gauge.

I guess for this type of thing to work a little bms tweaking would be required to tell the bms the new amout of ah to count and scale the dash gauge to.

Don......

MLucas
Posts: 833
Joined: Thu Jun 07, 2012 8:52 am
Location: Niagara on the Lake, Ontario, Canada

Re: Future battery replacement

Mon Mar 31, 2014 7:26 am

Would we be able to see anything with MUTIII? Be able to reprogram any of the modules?

Like Dylan...I went electric.

  • Purchased: June 29th, 2012
  • Mileage on June 29th, 2013 - 25,431 km / 15,802 miles
  • Mileage on June 29th, 2014 - 51,286 km / 32,616 miles

List of Oil Spills: http://en.wikipedia.org/wiki/List_of_oil_spills

Return to “Batteries and Battery Management”