Powering pi using lipo sand boost converter - Page 1
Forum section: electronics / beginners

author: amateur_25
author_rank: Regular Contributor
timestamp: June 04, 2014, 12:45:13 am
content: Hi guys,I'm planning on using this beefy pack to power my pi via a buck converter. These are supposedly protected cells as the datasheet shows what on the protection pcb.Anyway my question is will I be able to charge this battery using the Turnigy Accucel-6 50W? If not how do I charge it?http://uk.farnell.com/gp-batteries/nta2710/battery-li-ion-3-7v-4400mah-1s1p/dp/1848660They look different from the ones from hobby king. Those have a balance lead on them but these dont seem to have them. Does that mean these batteries are dangerous?

author: jamesglanville
author_rank: Contributor
timestamp: June 04, 2014, 01:24:27 am
content: You don't really need a balance lead on a single cell like that. You are missing out on kelvin voltage sensing without (if the charger does this), but it's not like there is a middle voltage to sense like there would be on a 2+ series pack of cells. You should be able to use that charger to charge them, though you may need to split the wires to both the charging and sensing ports of the charger. In my opinion this is fine, you are unlikely to get significant errors from cable voltage drop if you have short cables, but someone may correct me on this.

author: Rick Law
author_rank: Super Contributor
timestamp: June 04, 2014, 01:44:40 am
content: Quote from: amateur_25 on June 04, 2014, 12:45:13 amAccording to the item page and the PDF (from the link you provided),the specification said "1S1P configuration" so technically it is not a pack but is a single cell. So there really is nothing to balance.However, I am suspicious- the dimension given is the size of a "1S2P". I think it really is a pair of 18650's.I am not the definitive expert, as I understand it, the need for balance is much reduced in parallel. They will both be at the same voltage at all times and there is no risk of reversal. That said, the better one of the pair can take on more charge when alone but wont be able to take on more charge when paired. In fact it will likely waste energy helping the lesser partner keep up. So eventually, the lesser partner will accelerate the demise of the better partner within the pair.Re: charging, looks like a straight forward CC/CV charger will do nicely charging to 4.2V at 3A (max) according to the specs. So just hunt for aCC/CV charger @4.2V CV up to 3A(lower current generally is not a problem).Rick

author: amateur_25
author_rank: Regular Contributor
timestamp: June 04, 2014, 10:38:53 pm
content: So basically as long as I keep the number of cells in series less than 2 then I will be fine and I won't blow up anything

author: Rick Law
author_rank: Super Contributor
timestamp: June 04, 2014, 11:23:51 pm
content: Quote from: amateur_25 on June 04, 2014, 10:38:53 pm"less than 2"means you have a single cell. With just a single cell, you can't really put"them"in series or parallel.By the way, just to be precise, the spec sheet said 3.1A, I just rounded it to 3A. So any CC/CV 4.2V charger at up-to 3.1A will do nicely. If you are concern about "blowing anything up", charge it slower. I actually prefer to charge it at lower rates at <1/2C (so CV phase is shorter) and safer for those batteries that I don't have the specs on.