Lithium Polymer cells wanted, any sources? - Page 1
Forum section: electronics / general

author: Lightages
author_rank: Unknown
timestamp: February 06, 2018, 10:21:34 pm
content: I have a device that had two lithium polymer cells wired in series with no built in protection. They are rated at 1200mah, and measure around 70mm x 40mm.Anybody have a good online source for bare cells like these? The company, Black Magic Designs, wants $80USD for the replacement part, plus $100 for shipping to Chile. I see cells on various sites for something like $5 each with protection but I haven't found anything the right size yet.Thank you for any information.

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 07, 2018, 12:11:38 am
content: Try doing a search on ebay for "lipo 704050". That numeric code refers to the size - 70mm long, 40mm wide, 50 tenths of a mm thick (so 5mm; I was guessing, since you didn't specify). Vary the sizes a bit, and you should find something that fits.

author: Lightages
author_rank: Unknown
timestamp: February 07, 2018, 03:33:14 am
content: Thank you for the advice. I have no experience with LiPo cells. The marking on the cell is LP434073, but nothing I search for comes close.

author: Peabody
author_rank: Super Contributor
timestamp: February 07, 2018, 06:23:16 am
content: I think Maxlor may have the order of the dimensions wrong. A 704050 would be 50mm long by 40mm wide by 7.0mm thick. Your 434073 is 73 long by 40 wide by 4.3 thick. This site has useful information on lipos:http://www.lipolbattery.com/lithium%20polymer%20battery.htmlGoogle points me here:http://www.minmaxenergy.com/productsShow.asp?id=274Looks like they are the manufacturer. But maybe they would sell to you direct.

author: Lightages
author_rank: Unknown
timestamp: February 07, 2018, 03:58:33 pm
content: Thanks, that is exactly the battery I am looking for but I am sure they will not just sell me one or two. I will ask but I think I will end up having to build something from different specs.

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 08, 2018, 02:15:06 am
content: Quote from: Peabody on February 07, 2018, 06:23:16 amAh, could be. My point was, these 6 digit codes aren't part numbers, and for general purpose applications you don't need an exact match, just something that fits into your enclosure. So if you have trouble finding the right side, just go with something slightly smaller but more popular instead. As long as you get the same chemistry (and not, say, lifepo4 instead of lipo) it'll work the same, albeit with slightly less capacity.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2018, 04:14:17 am
content: I've bought most of my LiPo batteries from Hobby King. They have a wide range of sizes and capacities.

author: janekm
author_rank: Unknown
timestamp: February 08, 2018, 04:50:29 am
content: Lithium batteries require a lot of documentation to ship, so a place like HobbyKing is indeed your most likely bet (though you may find some sellers on Ebay too). You can remove the protection PCB from the protected cells, though it's not advisable for safety reasons. The two separate cells may not start out at the same state of charge, and charging the pair to the cutoff voltage of a 2-cell pack could raise either battery's voltage above the safe limit. You would be better off leaving the battery protection PCB in place (and even better add a balancing board).

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 08, 2018, 10:40:16 am
content: Quote from: james_s on February 08, 2018, 04:14:17 amThey almost only have batteries intended for RC purposes though, i.e. they're made for high discharge currents. That comes with compromises such as lower energy density and higher self-discharge rate. And from various stories I hear, they seem to be somewhat more volatile too (although maybe that's a result of making use of that high discharge rate, and not inherent in the battery?)

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2018, 06:24:02 pm
content: They have low current LiPos meant for powering transmitters and such too, but yes mostly high discharge rate stuff. Given the OP asked for unprotected LiPos I assumed that's what they wanted.