Hi Steve.
I would be interested to hear what HETER's offerings are. Their packs look like the typical large format prismatic LiFePO4 cells in a box with or without BMS. It should be interesting to evaluate what the total cost will be (including import fees and shipping) compared to putting something together yourself.
As far as wiring, if you look at my batteries (in this photo)
http://groups.yahoo.com/group/electricboats/photos/album/1967401930/pic/235874096/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc
you can see that I have kept each 4 cells strapped together, creating a 12V battery. Within each 12V unit, the 3V cells are linked in series with flat braided connectors (they have red shrink tubing in the photo). You can also see the passive BMS module on each cell (the red and gold "strap" between the terminals). These modules shunt off up to 0.6A during charging when the cell voltage exceeds 3.65V. The feature that I'm not using right now is a single daisy chained wire connecting the BMS modules on the entire pack that would shut off the charger if any single cell hit 4.2V (the overcharging limit for my cells). To date, none of my cells have fallen enough out of balance to hit 4.2V while the entire battery pack voltage is within the charger's profile. However, I do plan on wiring that up someday for peace of mind. I went with simple BMS modules rather than a complete system due to cost. There are very sophisticated BMS systems, but their entry price is kind of steep, especially because I only have 16 cells. My modules cost about $15 a piece, so my whole BMS cost was only $240. Your system would have close to 50 cells, so a more complex system might be justified. And then there is an ongoing debate with the EV guys about whether BMS are needed or even desirable, but the BMS concept makes sense to me
Each 12V unit is linked in series just like regular batteries with 2/0 cable with lugs and covers. Using 160Ah cells, the assembled units weigh 50 lbs each, so they're fairly easy to handle. In this picure, the batteries are not strapped down yet and they don't have the clear safety cover over the tops of the 12V assemblies that I made to prevent accidental contact/shorts.
My charger sees the entire pack as 50V (give or take) and manages it as a whole. So right now, my batteries are wired just like your L/A batteries. Prismatic LiFePO4 cells are readily available in a variety of sizes, so unless you need more than 200Ah (at 150V, that's 30kWh!) you won't need to do any parallel connections. I believe that the LiFePO4 manufacturers make cells up to 400Ah, they're just not as common.
I bought some of my gear (charger, instruments, etc.) from EVolve Electrics in Colorado.
http://www.evolveelectrics.com/
They have lots of stuff for this type of project, including LiFePO4 cells and BMS, and as a customer, they were great to deal with. I would also recommend checking with Current EV Tech in Washington.
http://currentevtech.com/cart.html
I have a lot of respect for Dave, the owner, even though I've never met him in person. He also seems to have good prices on the same sort of gear.
Feel free to contact me directly if you have more specific questions about your project.
Fair winds,
Eric
Marina del Rey, CA
PS. as long as I'm recommending suppliers, check out http://genuinedealz.com/
for your cabling needs. With free shipping, I haven't found anyone that comes close to their prices.
--- In electricboats@yahoogroups.com, Steve Dolan <sdolan@...> wrote:
>
> Eric,
> I'm just getting started at looking ahead to switching my 144v AGM's to LiPo batteries. I've searched most of the EV sites as well as the Net for info on wiring the pack to no avail. The Cruisers and Sailors site had a nice guy who gave the wiring diagrams for a House bank but didn't know anything about a Propulsion bank. Is it possible that you could draw up the best way to wire the pack up? I'm assuming it involves a Parallel and Series setup. I'm going to ask the same at the EV site as well.
> I'm also going to get in touch with a company in Thailand (HETER) that is producing packs. I may just get involved with a distributorship if I can get them at a resalable price in quantities. I like their drop in packs. I'll get a few to send out to individuals to test then go from there. I've got a few more questions on batteries in general I'll put in a separate post. http://www.heterbattery.com/
>
> Thanks,
>
> Steve in Solomons MD
> Lagoon 410 SE
>
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