48v mild hybrid systems?

[aaron_mason]

Hey all -

I'm considering an electric motorcycle conversion, and after building the last battery for my electric Vespa I'm looking to buy something off the shelf. I've been reading into a few of the new 48v mild hybrid systems, and they appear compact, rugged, BMS built in, passively cooled and able to deliver 10-15kW (200-300A). Awesome. The most interesting things I've found are these:

• A123 http://www.a123systems.com/automotive/products/systems/48v-battery/

• Bosch https://www.bosch-mobility-solution...owertrain-systems/electric-drive/48v-battery/

• LG Chem http://www.lgchem.com/global/vehicle-battery/car-batteries/product-detail-PDEB0001

I've read that GM and their eAssist system is also 48v, and other manufactures like VW and Volvo are following suit.

Anyway, does anyone have any experience with these 48v systems? Are there ways to buy the batteries, or do we have to wait for the cars to start crashing and getting parted out?

 

[john61ct]

Personally prefer to work with bare cells, or at least a BMS that can at least be bypassed. If open hardware with adjustable setpoints and non-proprietary protocols, maybe.

A123 is an LFP variant, would be my choice.

Bosch's chemistry seems to still be a mystery two years after release? And at 8Ah, under 400kWh, would need a stack of them, and why 12kg each? Bizarre.

LG Chem uses NMC

 

[aaron_mason]

My hope would be that by integrating the BMS and designing for outdoor automotive use, the packs would be solid on most fronts, including the setpoints, and kind of "fire and forget". I mean, anything with this much engineering behind it is going to be leaps ahead in durability compared to what I'm able to make in my garage...

I agree about the A123 batteries, especially with their Porsche connection. Any ideas on how normal humans would get ahold of them?

 

[amberwolf]

A123 sells bare cells thru their Stortronics site, but then you have to deal with connecting them, setting the pouches up with the right clamping pressures, etc. There's a number of threads on methods for these things.


If you can find them, there are easier cells to work with, like the EIG pouches with their OEM framework/holders that let you just bolt cells together (you might have to make interconnects for your particular use situation). I think it was the 2011 Zero that used them, and there have been a few poeple that bought large quantities directly from EIG, but they are a little hard to find. There's a sales thread in the used section if he has any left.

I don't push the ones I' have very hard, but Iv'e had them for a while and they work fine for my uses. Only killed one cell so far, discharging it below 0V by accident. Puffed up, but no fire, etc.

If, like your OP discusses, you can find whole modules that do what you want, of whatever cell type, you're probably better off going that way, if you want something easy to use that you don't have to use up a lot of time (and possibly resources) trying to build.

 

[Dauntless]

Are we missing the big print here? Mild hybrid means the battery doesn't drive the vehicle fulltime. Or even much of the time. People have much to say about using the 12v lead acid car batteries other than as intended, what might the issues with the mid hybrid batteries be? A123 was touting the ability to ignore potential thermal problems. Might these batteries be vulnerable?