What battery for a ~8KW 160V car battery? recommendation.

[Offroader]

If you were going to build a large battery for a car in the 8-10KW size, what would you use? Assuming you wanted to make this not so costly. Also size is of a concern as there is not much room to put the battery in.

Specs for the battery would be around 160volts, with at least 100 amp charge for regenerative braking, this is for a hybrid car battery conversion.

I've heard Leaf cells recommended, but wondering what you would consider using. Maybe one of the 18650 cells?

Thanks.

 

[Solarpower]

I have a 13 kW 72V car I am changing the batteries in. I've landed on that Leaf modules would be the cheapest alternative for me. Of course 18650s would be a good too, but I guess a lot more work if you are going to connect them all together.
Most likely I will be using 30 modules (which is in 2s2p config), giving me 15 kWh (original) capacity, and 50 kW power capability. A little more energy than the lead acid is rated at, and half the weight

 

[redilast]

I'd probably use a low mileage wrecked chevy volt pack because 18KWhrs can be had for $1500-2000. Buy a pack, and sell the rest of the cells you dont need/want.

18650's are great but for a pack that big it would be a real pain as you'd need around 800 of them. Would be quite a chore to build up a 18650 pack that big. The 18650's though do have great energy density and with that many cells you can definitely make the pack into the perfect size and shape for your application.

 

[Offroader]

I'd probably use a low mileage wrecked chevy volt pack because 18KWhrs can be had for $1500-2000. Buy a pack, and sell the rest of the cells you dont need/want.

18650's are great but for a pack that big it would be a real pain as you'd need around 800 of them. Would be quite a chore to build up a 18650 pack that big. The 18650's though do have great energy density and with that many cells you can definitely make the pack into the perfect size and shape for your application.

What I am looking at is the Tesla cells if you can get a deal on them. Right now on ebay they sell for about 444 cells for $1399 dollars. That is 5KW of cells. You wold have to remove them from the housing they are in.

http://www.ebay.com/itm/Tesla-Model-S-battery-module-24V-250Ah-5-3kWh-444-Panasonic-18650-3400mAh-/262333679871?hash=item3d144e48ff:g:OSkAAOSwh-1W5acD&vxp=mtr

Hopefully you can get them cheaper with finding a deal.

When looking at the leaf cells, you really do get killed with the size and weight of those cells. I could build a much smaller and lighter pack using 18650 cells.The other issue is like you say, I would have to fit these cells into a 2 door honda insight battery box, room is limited so 18650 would maximize the pack size in that small battery box.

 

[redilast]

I'd probably use a low mileage wrecked chevy volt pack because 18KWhrs can be had for $1500-2000. Buy a pack, and sell the rest of the cells you dont need/want.

18650's are great but for a pack that big it would be a real pain as you'd need around 800 of them. Would be quite a chore to build up a 18650 pack that big. The 18650's though do have great energy density and with that many cells you can definitely make the pack into the perfect size and shape for your application.

What I am looking at is the Tesla cells if you can get a deal on them. Right now on ebay they sell for about 444 cells for $1399 dollars. That is 5KW of cells. You wold have to remove them from the housing they are in.

http://www.ebay.com/itm/Tesla-Model-S-battery-module-24V-250Ah-5-3kWh-444-Panasonic-18650-3400mAh-/262333679871?hash=item3d144e48ff:g:OSkAAOSwh-1W5acD&vxp=mtr

Hopefully you can get them cheaper with finding a deal.

When looking at the leaf cells, you really do get killed with the size and weight of those cells. I could build a much smaller and lighter pack using 18650 cells.The other issue is like you say, I would have to fit these cells into a 2 door honda insight battery box, room is limited so 18650 would maximize the pack size in that small battery box.

At that price its not worth buying used cells at $3+ per cell IMO. You can get new ones for that.

 

[Offroader]

Problem with Tesla cells is that I learned they are really difficult to take them out of the housing they are in. They may even be epoxied into the cell holder. This is why you are stuck buying the whole housing which I wouldn't want and probably adds to the expense.

I would have to buy new cells at $3-$4 dollars each but hard to justify considering I would need over 1,000 of them.

The other issue i found with 18650 cells is that the charge rate really sucks and you need a high charge rate for regenerative braking on a car. If I built a ~200 volt pack of 3400MAH Sanyo 18650GA cells, in a 48s30p configuration, 17,280 watt hours of capacity!, it would only have a standard charge rate of 50 amps.

I would need regenerative braking at 100 amps. Remember that is building a huge pack and I don't know if I really would want a 17,280 watt hour pack.

Really I would only want a 48s15p pack, but that would give me a standard charge rate of 25 amps. In this case would it be OK to charge that pack at 100 amps for regen purposes? that would be 4x over the standard charge rate.

 

[Ohbse]

30q's/25R's/HE4/HG2 are all rated at 4 amp charging, in reality they will take bursts of higher than that without dramas. In your hypothetical pack that would give you a rated charge rate of 120amps...

Volt cells are at the more power dense end of the spectrum, leaf cells are superior from a packaging/ease of assembly perspective but less power potential.

Personally I would still assemble it from 18650's, 800 cells is not too bad if you can modularise the pack and produce it over a period of time. Definitely no comparison between that and the leaf modules though if you're tight on time!

 

[redilast]

And then there are cells like the Sony VTC5A rated at 6A continuous charge current, but short bursts of higher than that shouldn't be an issue.