[maestro7879]

I have a Miles ZX40s.
Currently there are 6 AGM batteries for a total of 72v.

What are my battery options ? I was looking at Chevy Volt batteries on ebay that look to be compatible. I'm not certain what else I would need to do the conversion to lithium.

I imagine a new charger.

Thanks

 

[brian_]

Typical EV and plug-in hybrid batteries (that you could get as salvage, such as those from a Volt) run about 3.7 volts per cell (nominal) and are combined in 96-cells-in-series packs for 360 V (nominal), usually in several modules. So you can use a few modules of almost any of these battery packs, although you may need to put some in parallel for sufficient capacity.

For any lithium battery:

• A new or re-programmed charger.
• A battery monitoring system of some sort (this will likely start a spirited debate).
• Mounting brackets, housing boxes, interconnection cabling.

Many EV and plug-in hybrid batteries (including the Volt, but not the Nissan Leaf) have active thermal management systems using circulating liquid coolant. To use those modules at their rated power level will require arranging and plumbing that system.

 

[maestro7879]

Thanks for the information.
Looks like 9-10 Leaf modules would work for me.

The BMS is essentially balancing the cells correct ?
I come from the RC plane world where I balance my packs on every charge.

Looks like I would go from 100ah to 66ah but I'm thinking the decreased weight might make that a non-issue.

What would be an appropriate charger for this system ?

 

[brian_]

The BMS is essentially balancing the cells correct ?
I come from the RC plane world where I balance my packs on every charge.

At a minimum a BMS should monitor at the cell level, so charging and discharging can be stopped when any cell hits a limit, instead of just using a pack limit and assuming they're all in balance.

How a BMW should automatically balance, or whether it should balance at all, is the subject of many debates. I'll stay out of that.

Looks like I would go from 100ah to 66ah but I'm thinking the decreased weight might make that a non-issue.

Since the 100 Ah rating of the lead-acid batteries is probably at a 20-hour discharge rate, in actual use you will get much less capacity. You are probably also not discharging the lead-acids very deeply (since that shortens life), so the usable capacity of lead-acids with a 100 Ah rating might not be very different from lithium-ion with a 66 Ah rating. Lower pack weight and thus lower vehicle weight is a bonus.

What would be an appropriate charger for this system ?

I'll let others handle that one...