Batteries in parallel?

[nigel]

G’Day, got a new guy question here. I have just set up a 25” mono using two 11.1volt, 2200 milliamp, 3 cell LiPo’s in parallel. I a using a Y lead (with Deans connectors) between the batteries and the speedy. The question is how do I stop one battery draing more than the other?
Is it possible, any help is appreciated?

Cheers Nigel.

[Fluid]

With correct parallel wiring, both packs must discharge the same - if they are the same type/capacity cells. From your description it sounds like one of these:

* Wiring harness is poorly assembled with high resistance to one pack
* One pack is not being fully charged
* One pack is not of the labeled capacity
* One pack is damaged internally
* The packs are very poorly matched/cheaply made

Send both packs in for repair.


.

[Steven Vaccaro]

Fluid is right on.

In a setup like this I would make sure not to drain the cells to the lowest point.

Also during your testing phase, run for a couple of laps. When you come in to test for component heat, top off the cells by changing the,. See whats left inside both of them and take note. They should both be equally drained.

[NorthernBoater]

What is the setup in the boat? What is the "C" rateing on the batteries?

[nigel]

Thanks guys,
Both batteries are the same type and capacity/rating (25-50C) bought at the same time. The boat has only had the one test run so far and both batteries were charged before the run. As I had no idea what the draw on the batteries would be I ran the boat at full throttle for 45 seconds then checked. Both batteries were at 29 degrees C. Set up is a Hacker Navy 77 and Feigao 7L, prop X436/2. Like I said first electric so all help appreciated.
Nigel.

[Fluid]

New LiPos should be broken in by running at low amp draw (3C-5C) the first few times. If you over-discharge a pack the first use, it will be permanently damaged and will never run right.

Did you charge the two pack separately, or in series? It is not a good idea to charge new LiPos in series the first few times. The two packs should be run in series together a few times first. Even then it is better to charge separately.

.

[nigel]

Batteries charged seperatly and run in parrallel. First run and only used 460 miliamps .

[Jeepers]

New LiPos should be broken in by running at low amp draw (3C-5C) the first few times.

.

How do you do your breaking in Jay?

First time I used my 2s packs i put them in my wifes RC10B4, with a very mild 20 turn motor. I was a little nervous about sticking them in my boats as I was not sure of the power potential!

[whiplash]

How far out where the two packs, you said first run 460mAh used,
what about the other pack if its the same than you dont have a problem.

[whiplash]

and do you balance charge them? through the tabs? there are multiple ways to charge.... if you charge through the deans, put a balancer to each pack seperatly first, after balanced, than charge one at a time through deans. or , put a balancer on the tabs while charging through deans, if you balance after you charge, your cells will be balanced, but you would lose some mAh due to the fullest cell sharing with other cells. meaning you may have started out with both packs having different mAh values

[nigel]

Second battery only used 60mAh. I charge and balance each battery on their own. I will re do the solder on one battery deans (not quite as good a job as the other) and give it another test maby Tuesday. I will give it 90sec full throttle this time (just changed the timing on the Hacker for max RPM) and see what happens.

Just like to add that I appreciate all the help here, good place for someone like me to learn.
Cheers Nigel.

[nigel]

Thanks for the help guys.
Found the problem to be in the Deans connection of one of the batteries to the ‘Y’ harness. Have fixed this up so will go and test tomorrow. Must say that I do like the way this little boat runs for a bit of fun.
Cheers Nigel.