Lipo fully charged?

[dimpirate]

Hey guys, when balancing lipo pack with battery medics I've read and seen on hyenas you tube video that pack should be fully charged before commencing. What's the reason? Also how crucial is this? The reason I'm asking is cause it takes so damn long to discharge to 4.10V on my 18S 4P when fully charged about 18 hours.... :-(

Thanks for any replies
Fred

 

[Ykick]

BM's are slow especially if you use paralleled 4P balance wiring. I like RC Lipo about 4.15V too and the BM's don't help there either. So, I've found myself charging individual cell groups through the balance plugs. In other words, bring low cells up in a couple minutes, rather than waiting hours to discharge higher cell groups through BM.

 

[dimpirate]

BM's are slow especially if you use paralleled 4P balance wiring. I like RC Lipo about 4.15V too and the BM's don't help there either. So, I've found myself charging individual cell groups through the balance plugs. In other words, bring low cells up in a couple minutes, rather than waiting hours to discharge higher cell groups through BM.

Sounds good ykick, BM's don't help with that or my BMS bulk charger what do you use to charge the individual cell??

But I still don't understand why pack "should be" fully charged to balance, using your method if pack is terribly unbalanced and fully charged you wouldnt want to charge individual cells any higher right?? Do you do this when pack is not fully charged?

I'm hoping someone can give me an answer to why pack should be charged fully, or else I can charge pack to just above 4.10 and discharge might take just an hour. I'm sure it's a simple reason or else everyone would be doing it....

Fred

 

[Ykick]

...what do you use to charge the individual cell??

RC charger setup for 1S and desired termination voltage. This requires a simple wiring adapter and understanding how the balance plug is wired to access individual cell groups.

But I still don't understand why pack "should be" fully charged to balance, using your method if pack is terribly unbalanced and fully charged you wouldnt want to charge individual cells any higher right?? Do you do this when pack is not fully charged?

Sorry, not really following you here? Fully charged RC Lipo to me is between 4.1-4.15V/cell. I can see nothing wrong with going a little above 4.1V and let the BM pull 'em back from there. Once they're all balanced that way, bulk charge it up to 4.15V if that's what you want?

I'm hoping someone can give me an answer to why pack should be charged fully, or else I can charge pack to just above 4.10 and discharge might take just an hour. I'm sure it's a simple reason or else everyone would be doing it....

Do you mean "charged fully" as in 4.20V/cell? 'guess I should take a look at the video you're referring?

 

[dimpirate]

quote]Do you mean "charged fully" as in 4.20V/cell? 'guess I should take a look at the video you're referring?[/quote]

Yea that's what I'm charging to, I do have methods HVC breaker so I don't risk going over 4.29
I don't believe hyenas video on BM's specifies what fully charged V should be 4.2, 4.15.
Maybe what hyena, Matthew(made pack for me) and what I've read elsewhere, there not neccecarily meaning 4.2+ which is what my pack usually reads at "full charge". And 4.15 is full enough like your saying...

 

[dimpirate]

Ok so I just saw you tube video again. Answered my own question 4.15 is definattely fully charged, I'll try that next time I balance should reduce discharge time in half.... Thanks ykick

Fred

 

[Hyena]

By "fully charged" I meant the voltage off the charger - which I set in bulk charging to ~4.15v/cell for a safety margin and for the best compromise between range and longevity of the pack.
Technically most manufacturers state the full charge voltage at 4.2v

Either way my comment to balance when "full" is because that's where you you set out using the pack from. Sure if you're got a badly out of balance pack you could discharge all the cells down to the same level then charge up again, but you'd then still check the balance at the top. Well used packs can get quite out of shape towards the end of their capacity (ie at the "cliff") but will still bulk charge back up to be almost perfectly balanced.

Your pack is only as strong as the weakest cell so you want them all to be around the same voltage to start with if you're going to get the most capacity from the pack. If you charge every cell to 4.2v and one is sitting at 4.05v then (assuming you're using some sort of monitoring) you're going to hit the LVC when that one cell bottoms out, leaving the others with juice still in them.

If you're charging and discharging your packs conservatively and build it big enough that you're not running it right down then it becomes a bit of a non event and you could largely get away without balancing anyway (though I wouldn't recommend it, especially for noobs)

 

[dimpirate]

Thanks for the clarification hyena. Simplifies everything I was complicating in my head..
Fred