The postman just delivered my PL6 parallel charging board from Progressive.  Are there any cautions for parallel charging?  For example, if batteries having tiny internal resistances start at different voltages, will something explode when you connect them in parallel?  Can the charger tell you if you have a duff cell on one of the batteries? I guess I could measure the board to see if it has resistors inside, but it's busy now.  

Howard,

I applaud your caution, but parallel charging is good (and safe) practice if all your batteries are in good condition and you start with them at a similar state of charge. When you first hook them up, before you start the charger, any small differences in the battery packs (voltage) self equalizes (higher charge discharge into lower charge state cells/packs). I tend to use the cell balance connectors even if I am not using the balance function of the charger for a similar reason.

Regarding your concern about differences in internal resistance (IR) among cells and packs, you will have some even though all your packs/cells are from the same manufacturer with the same rating (even when new). As they age (ie.# of charge cycles) their IR will rise slowly. Big differences between packs/cells will introduce some difficulty as the weaker (higher resistance) cells will draw less current during the charge cycle than lower resistance ones. Therefore, the lower resistance ones are gobbling up more of those electrons than the higher resistance ones but the apparent voltage is (because of their greater IR) rising faster in the higher resistance ones than the lower resistance ones. Just like you were charging them separately. Net result is that (though the charge voltage may be similar) at the end of the charge cycle, the IR cells will have less stored umph than the lower IR ones.

OH! If you have packs/cells that have high enough IR that they are warming when charged.......don't.

Honestly, as long as you are charging identical packs that are similar in age....don't worry....be happy.  I have been balance charging for a year now and have lived to tell the tale. Rumor is that some have done longer.   (Don't you just love new toys!)

Finally, as far as you know, I made all this stuff up and am just trying to make it easier for those other guys (the ones without a sense of humor) to win.


Bob

Which board did you get? I generally charge only similarly discharged or discharge similarly charged packs together.as far as caution goes make sure the balance plugs are always put in properly they can be forced backwards

http://www.progressiverc.com/parallel-charge-board-for-thunderpower-t-plug.html .  I worried about the backwards-balance-plug problem.  That's a situation that I don't think the charger's checks would catch.  Thank you.

Howard.
I have purchased three para boards over a stretch of time.  (Progressive R.C.,and EP Buddy).I eventually damaged two of them by plugging in the balance leads with reverse polarity. THe guy at Progressive ,confessed that he has even done that careless BooBoo himself. In one case my carelessnes even damaged (shorted out) the balance leads on a good Thunderpower battery.
    I no longer use the Paraboard method. Now Alan , Chris, and myself all use the Parallel charging harness instead.In an ads , it just doesn't look as cool as the board , but it's "oh so much easier," to use. With the board , you need to position the batteries to suit the hook up and that leads to more strain on the balance leads attached to the batteriers. You don't want to damage one of those and end up with a patched up battery pack. On the other hand, the harness is so flexible that it conforms and goes where it is needed and there is way less strain on the fine wires that come out of the battery pack.I believe that Chris and Alan recognized that in the very beginning and mentioned it to me. I don't even believe they own paraboards. Keith

Everything Keith said and more.  With the lone exception of my very first I-Charger 4 years ago I have never used a para board.  I now have separate cable harnesses to charge and balance 2, 3, 4, 5 and 6s batteries.  I will be hiring a 'Cable Administrator' as soon as I can come up with a palatable job description.

BTW you haven't lived until you start making your own micro connector wire assemblies and don't get me started on sub-micro stuff! 

Be careful with this electric stuff.  It takes you places you never thought you'd go!

The postman just delivered my PL6 parallel charging board from Progressive.  Are there any cautions for parallel charging?  For example, if batteries having tiny internal resistances start at different voltages, will something explode when you connect them in parallel?  Can the charger tell you if you have a duff cell on one of the batteries? I guess I could measure the board to see if it has resistors inside, but it's busy now.  

Hi Howard,
The difference in voltage between, say, a 50% discharged battery at rest, under charge, and under discharge is wider than you would think.
I need to go find real data, for show, but not this moment.
Meaningful equalization happens even during the constant current phase but colpetes in the constant voltage phase as you suspected.
Still, I would not connect a nearly charged pack in parallel with a beeply discharged one, but I am a coward.
If you are building a pack with cells in parallel (common practice) then prudence dictates pre-charging each and every cell to storage voltage first, and doing a few slow charge and discharge cycles.

Regards,
    Dean

Motorman    
You'll see lots of pictures of parallel harnesses on progressiverc.com under the heading "cables".  Keith