Need help selecting lifp04 battery

[Glennsgarage]

Here is what I think I need for multiple robot / Segway projects I have with various voltage and amp hour needs.

Four 12v lifepo4 packs between 5 and 10ah.

I want to use the packs in series or parallel to get higher voltage or ah depending on my project.

A good charger ( or 4 chargers) to charge up all 4 at the same time

I also produce up to 20 amps of regen braking for short bursts so I would like a configuration that can withstand the load.

I am open to the good cells from the western world, or cheap ones from the east. I plan on using them as long as they live and want reliability, but they are not on a mission critical app.

I have been trying to make a purchase for a week now and I'm no closer to a descision now, than when I started my search.

Thanks!!

Glenn

 

[dnmun]

if you find a 12V lifepo4 pack, let us know.

 

[Glennsgarage]

14.4v should be close enough to 12v for my apps...

 

[dogman dan]

Hmm, 12v lifepo4 batteries, that consist of 4 cells in series have been around for quite some time. Often packaged in a plastic box, and sold as a motorcycle starter battery for example. But yes, a 12v single cell lifepo4 does not exist.

This sort of battery would work fine for lower amperage requirements, such as 20 amps. The ones I have in mind are 20 ah size, using cells that can take at most 2c. Edit, I couldn't find the ones I had in mind, but these are similar. Not recomending them specificly, just showing the type I was jabbering about.
http://www.ebay.com/itm/Phantom-APP18A1-BS12-Motorcycle-Battery-LiFePO4-12V-18Ah-270CCA-/261019297209?pt=US_Rechargeable_Batteries&hash=item3cc5f665b9

But you might want to look into RC lipo cells, our favorite source being Hobby King. Great c rates at great prices. Some precautions needed for safe use but nothing to hard to live with. This type of cell charges to 4.2v per cell, so 3s is "12v" or your stuff may work ok at a 4v higher, 4s voltage.

Or get some A123 lifepo4's someplace. One of our favorite lifepo4 vendors should be able to help you, at Emissions Free. Pingbattery, another of our recomended vendors may be helpfull too. both of them don't normaly carry a 12v product though.

 

[Glennsgarage]

Okay, think I'll try the a123 from zero emissions. I would not usually order stuff from china that only accepts paypal, but since they are endorsed by endless sphere I'll do it.

Thanks for the help...

Glenn

 

[dogman dan]

Cellman is on our trusted vendors list.

 

[dnmun]

paul is not gonna be able to make a 12V pack for you though.

the chinese do perfectly good work and your racial bias is gonna cost you money. they make all the battery packs. even paul uses chinese parts since they are cheap where he is in china.

you can buy a 48V20Ah lifepo4 pack for $500 delivered. from sun-thing on ebay.

most people use the commercially available BMSs and they start at (8S for mr li ping) and go 12S, 16S, 24S for 36V, 48V, 72V lifepo4 packs.

you really should think about how you will use the packs, plugging them into a series of packs may not be useful either. you need a BMS for lifepo4.