How to charge (2x) 4S on BC8?

[aaron07]

1.) Does the FP board for the BC8 charge to (2x ) 4S 2100's in series?
2.) Does anyone have experience with the BC8 charging 2x batteries at once?

[Big Fil]

I know both theglennster and RC Accessory have both done multiple battery charging on Bantam units. Try PM'ng them for more info or go to the lipo/charging forum and dig through it for the threads which talk about it.

[theglennster]

Hi Aaron

I've been doing it recently on a BC-6 charging both my T-Rex450 3 cell lipos in serial no problem. You can basically half your charging time for 2 packs the only down side is you both packs to be reasonably discharged to the same degree or the last charging stage takes forever and defeats the whole point of doing it.

Here's how I did it :-

1. Make up a serial (Y shaped ?) charging lead I use Deans on my batteries so it ended up looking like this. Note the polarity in the picture.

http://www.helifreak.com/attachment.php?attachmentid=26204&d=1189624990

2. Buy a Thunderpower Balance adapter TP6P4PE (not essential but a nicer way to do it) You can cheat by plugging one of the lipos balance taps into the 6 pin socket but offset it next to the 4pin (this is important or you will get an error)

http://www.helifreak.com/attachment.php?attachmentid=26206&d=1189625058 (http://www.helifreak.com/attachment.php?attachmentid=24810&stc=1&d=1187727659)

3. Connect the batteries up as the photo taking note of the polarity. ENSURE the positive charge feed is on the positive balance feed. I can not stress this highly enough or you WILL short your batteries or damage the charger.

http://www.helifreak.com/attachment.php?attachmentid=26207&d=1189625089

4. Set the Bantam to charge 6 cell (or 4 cell for 2 cell packs) at whatever rate appropriate for your Lipo's for my Flightpower Evo 2170 I charge em at 2.1amp. Now feel smug that you have two packs charged in the time it normally takes to do one.

Please Please Note you are doing this at your own risk if you don't pay attention to the polarity you can cause damage as you are basically shorting out your Lipos. (Dont ask me how I know this :oops:)

YOU HAVE BEEN WARNED
Using this method for charging two equally discharged packs is definitely the way to go :thumbup: the only problem I can see is the larger the difference in balance between the two packs the greater the knock on effect in balancing time.

2 fully discharged Lipos (down to 11v) will take 90 mins to charge using the normal balance method but you can really reduce this using the FAST charge setting. You can really see towards the end of the charge the batteries are full but it juggles around balancing at 0.1a with the last 0.1v between the cells for a good 20 mins you can pull the plug before this point or use fast charging to miss out this bit.

For an experiment I did a bit of playing around to try and see if you put a fully charged pack with a flat one how long would it take to charge ? and I got to 12 hrs and gave up :rolling. This is obviously the downside to this method of charging you wont do any harm but it will probably take a day to charge the 1 flat lipo.

Anybody with a Bantam BC-6 or BC-8 I would say go for it this is an easy way of getting your lipos twice as fast just be careful of the polarity when plugging em in. Buy the Thunderpower adapter if you want to do it cleanly or put the 4 pin plug into the 6pin socket it all works.

Edit My Apologies Aaron I've just realized your problem with charging 2x 4cell packs the Adaptor board will not give you the option if you want to balance charge them as their is a dead pin in the lipo balance tap connector. You could make up an adapter lead that would do it no problem they sell an open ended harness you could canibalise or charge without balancing to 90 full then top them off individually. Heres how the taps are wired :-

http://www.helifreak.com/attachment.php?attachmentid=26210&stc=1&d=1189626690

Cheers
Glenn

PS. BTW If you want to see what happens to a Bantam if you turn your brain off click HERE! (http://www.helifreak.com/attachment.php?attachmentid=26209&stc=1&d=1189625650)
Luckily my Brother is a dab hand with surface mount stuff :thumbup:

[aaron07]

Thanks guys. I had the same set-up with my BC6, but it was limited to charging 6S max in series, so I assumed I could do the same with the BC8. I'll post my results when complete.