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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 02-18-2014, 09:55 PM   #1
Stilter
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Question Paraboard... Am I doing this right?

This is my first venture in parallel charging.
I have a parallel board, an ElectriFly CellMatch meter/balancer, and an Onyx 230 lipo charger. The Onyx 230 does not have a balance port, hence the EF CellMatch. Also note that the Onyx 230 has a max charge rate of 7.0 amps, so for multiple packs this will usually be less than 1C. (I know I need a bigger charger.)
I have read that I must only plug in batteries of the same cell count (I got it) and the cells should be at nearly the same voltage across all packs.
The setup I am planning is to plug my battery packs into the paraboard, the balance lead from the board goes into the EF CellMatch, and the charge lead from the paraboard goes into the Onyx 230 charger and charge.
Based on that setup, am I safe?
One problem..
When I check my battery packs using the ElectriFly CellMatch, I noted that some packs have cells that are off by a few tenths of a volt when compared to other packs.
Can I plug all the batteries I intend to charge into the paraboard and the paraboard into the EF CellMatch and get all the cells to balance without plugging in the charger?
Will this work as a good procedure to prep the multiple packs for a parallel charge?

Thanx...
Stilter
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Old 02-18-2014, 10:42 PM   #2
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What you describe sounds right for what you have. You'll definitely want to go to a charger with built in balancing and the separate power vs balance leads to connect for higher charge rates. Balance leads really aren't meant to handle 7 amps.

You can be off by 0.5 v/cell (highest pack to lowest pack) and shouldn't have a problem paralleling. Resistance of the wire and battery internal resistance will keep the current down as the packs equalize.
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Old 02-19-2014, 01:39 AM   #3
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I don't know if you just forgot to mention it, but I understand your batteries must be the same capacity as well.
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Old 02-19-2014, 02:23 AM   #4
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Actually they do not need to be the same capacity.

Series needs to be the same capacity but parallel can mix.
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Old 02-19-2014, 06:17 AM   #5
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Interesting. I thought I read that somewhere. But say you're charging a 3s 1300 and a 3s 3300. Would you charge at 4.6 amps? Would that be split in half to each battery, thus charging the 1300 at 2.3A? Would the 1300 charge slower, or 'fill up' with electrons faster? Ugh! This can give a guy a headache! Can you (or anyone) please shed more light on this?
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Old 02-19-2014, 08:23 AM   #6
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if parallel charging different capacities the internal resistances and the batteries seeking to equalize voltage will work out to charge them split proportionately to their capacities.

Works fine.
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Old 02-19-2014, 08:47 AM   #7
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But then if you have batteries rated for 1C charge rate, or you just like to take it easy on your batteries, how do you know how many apps it's getting?
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Old 02-19-2014, 11:06 AM   #8
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Just chance upon a great post over at RCG about parallel charging. It explains some of my questions and taught me quite a bit. Thanks for opening my eyes to this, fh. Funny thing is, I just wrote an article on the basics of parallel charging (the BASICS!) for our club newsletter. I'll have to revise it a little now.

Here's the link to that RCG post: http://www.rcgroups.com/forums/showthread.php?t=932319
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Old 02-19-2014, 11:16 AM   #9
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Always do the math and charge based on the rate for the lowest C multiple pack.

If all packs are rated for 5C charge then you can add the capacities, multiply by 5 and you have the rate.

If JUST ONE is rated for only 1C charge you need to charge at a max of the total capacity = rate.

If there is no listed C rating for charge on the pack label then assume its 1C max.
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Old 02-19-2014, 03:16 PM   #10
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fhhuber, thanks for the confidence.
I plugged my batteries into the paraboard and the paraboard into the EF CellMatch balancer. I did not plug the paraboard into my charger. After a few hours (while doing other modeling) I rechecked the individual batteries and their cells and (Bob's Your Uncle) all the cell voltages were within .02 volts of each other. They had been off by nearly .5 volts. Now I feel a safer about charging the group of batteries without over-charging any one cell.
The way I understand it, the balancer connects all the cells and the electricity flows to even out across all the cells.
This parallel board seems to be the answer to treating batteries right.
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Old 02-19-2014, 09:50 PM   #11
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Parallel charging is really good for packs that get used in series.
It always seems that one pack goes lower than the rest. Parallel charging evens them back out quickly.
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