6S8P Li-Ion high-C LiPo field charging solution in a case (fly all day on two LiPos)

[Duncan Disorderly]

7 minutes ago, Philip Lewis 3 said:

No sorry I disagree, do not use a BMS

 

I thought the BMS had its own way of managing the supply charge? You're correct, you can't run one through your normal charger, it's a self contained system and I can't even get my head around how using both could even happpen!

 

I need to read up more about them.

 

In the meantime, headroom is your friend.

 

[Philip Lewis 3]

No a BMS just watches the voltage and effectively disconnects that cell or cells once that voltage is reached, you only need a BMS when using a "dumb" charger i.e. a simple two pole DC charger such as a wall wart, your balance charger pumps out the total pack voltage through the charge leads and then wastes away or dumps into a resistance the excess for a fully charged cell through the balance wire which is why a balance charge can take a long time at the end, it can only charge at the rate it can dissipate any excess.

[Philip Lewis 3]

To sort of conclude my thoughts on this (for whatever they are worth) this is exactly how I would wire it up if/when I build one, a single cell going open circuit won't show up you would just have a much reduced capacity from those cells in parallel, the same as you would when parallel charging multiple batteries and a cell with a high resistance simply won't accept a charge but the other cells won't be able to be overcharged either as once the set voltage has been reached the charge will cut off.

 

Yes you can get much more complex, for instace a formula 1 car battery has every cell monitored (I've seen it) but we don't have their millions.

 

Just a suggestion Duncan, but I would only charge this to 4.1 volt a cell not 4.15, 4.1V is the natural chemistry Lion voltage which they pushed to 4.2V, chargers which have a Lion charge setting should be set to 4.1 V per cell, only reason is again for longevity I'm not saying you are doing any harm but you really aren't losing much capacity using 4.1V rather than 4.15 or 4.2V.  

 

I really can't see a better way of wiring this set up.

[Andy J]

This site was quite informative about charging and interconnecting lifep04 batteries.

[Neil R]

@Duncan Disorderly- many thanks for providing the inspiration, here's one I've put together over the last couple of weeks. It was finished earlier today, and so far the charging is keeping all the voltages nice and even, which gives me confidence I didn't kill anything when soldering. (I bought an ISDT Air 8 also). 

This is going to absolutely transform my flying, perhaps especially in terms of grabbing those last minute opportunities when nothing else has been charged.

Thanks again!

[Duncan Disorderly]

18 hours ago, Neil R said:

@Duncan Disorderly- many thanks for providing the inspiration, here's one I've put together over the last couple of weeks. It was finished earlier today, and so far the charging is keeping all the voltages nice and even, which gives me confidence I didn't kill anything when soldering. (I bought an ISDT Air 8 also). 

This is going to absolutely transform my flying, perhaps especially in terms of grabbing those last minute opportunities when nothing else has been charged.

Thanks again!

 

Wow that's really good! Better than mine, anyway. I hope it brings you the freedom to fly that mine's brought me. Going forwards, it's nice to only ever have to buy one or two new LiPos. Those ISDT Air 8 chargers are brilliant - I really lucked in there because I didn't do an awful lot of research other than a quick check to see it'd do what I needed.

[Duncan Disorderly]

I'll check in on this topic now and again to update the total number of 4C/12A charges those two 6S 3300s have suffered and whether there's actually been any suffering involved. Worth doing, I think, because there was consternation earlier in the thread about >1C charging. They're now on 143 cycles at 12A and are still showing no sign of anything degrading.