looking for Li-ion cells

A good place to start is to look at our EV Collaborative Handbooks under EV Batteries. There is a large amount of data on VisforVoltage which has been compiled and placed in the Handbooks to help answer questions that have been asked over and over.

hope this helps,
Grandpa Chas S.

There is a seller on ebay know as ping. Many of us have purchased packs from ping with very good results. His packs do not use the 18650 cells. His prices are very reasonable too.

Grandpa Chas S.

I can help you with your interest in Lith Ion battery's at a resonable price. Info is available at cruisin [at] live.com.

Can anyone recommend some good li-ion cells (in the 5-10Ahr range) and also where I can buy them?

I am not looking for iron phosphate or lipo cells.

Thanks,
Peyton
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Peyton - what chemistry do you want to use? Lithium ion is a generic name for a range of cell chemistry. You've ruled out two of them - lithium iron phosphate (LiFePO4) and lithium cobalt (LiPo).

Are you looking specifically for lithium manganese? (edit: I see you mentioned Saft - they make a full range of cells so that doesn't narrow it down... /edit)

What's your goal for the pack?

Andy

Thanks Peyton - that helps me understand. I still don't understand ruling out LiPo or LiFePO4. ;)

If I wanted to replace lead in a fixed application - like an electric gate or your radio installation, I'd use LiFePo4 hands down. They have the easiest management, lowest 'hazard' potential, and longest cycle life of other lithium commonly available. If longest life/best value is the primary factor, LiFePO4 wins. If absolute smallest package and lightest weight is far and away the main factor, than LiPo wins.

Here's a pretty decent LiPo pro/con thread that might help: http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9170

I still think LiFePO4 would be a better choice. Charging can be done inexpensively, and can be done by a lead-acid charger/charge controller commonly used with solar. You can get smaller cells, sure, but can also get 10Ah 40138 cells, and a range of packs from Ping and Cammy_cc on ebay in 10 and 20Ah. Any LiFePO4 solution is going to weigh 1/2 of lead. If you keep fairly shallow discharges (40-50%) you can expect more than 2000 charge cycles. 40138 cells tested by a US lab provided more than 8000 cycles in the hybrid car routine - where the cell is never charged above 80% or discharged below 40%. Even at regular 100% discharges, you can expect at least 1500 cycles before capacity drops to 80% of new. This is compared to lead's 300-500, and LiMn's 500 cycles.

How many days of bad weather do you need to pack to provide? What's the current draw of the radio?

Keep us updated with your project!

Andy

Andy,

Sorry, I do not have much knowledge on the chemistry, I still have a lot to learn.

My goal is to make a smaller and lighter weight battery to replace a SLA battery back-up for a solar panel. My main focus is on the BMS i'm developing, but the application is for a solar backup to power a 30W Wi-Fi radio which takes a DC input from 40-72V, so it's not a high power application. However, I do need high capacity.

Saft appears to have blown me off, but I hear they are quite expenisve anyway. It seems the lightest, cheapest and smallest form-factor option is to go with 18650 cells and just put about 15-20 of them in parallel. I'm not sure how much of a headache that is going to be, but I was hoping to avoid it. I ordered a Tynergy LiPo cell as well, and will see how reliable it is. I may go that route as well.

Thanks,
Peyton