How to Charge and Balance 2 3s1p Packs as a Single 6s1p
Anyone who owns a T-Rex 450 or 500 knows that one of the big downers is the short flights and long charge times. I have a Thunder Power 610c charger which is capable of charging a 6 cell pack, however I only have 3 cell packs for my T-Rex 450. I read a forum post somewhere where someone built a parallel balancer lead which let him charge 2 3s1p packs at the same time. He had the right idea but the problem with charging them parallel like that is that the balancer can't see the true voltage of any one cell. It can only see the combined average voltage of the 2 that are paralleled. The only way to safely charge and balance 2 3s1p packs is to build a serial balance lead that combines the two packs into a proper 6s1p. The charger can then see each individual cell and will charge up to 25.2v, balancing the cells to 4.2v each.
I started by cutting the extensions in half and probably could have cut off much more because I had way too much wire to work.
Toss the male sides of the 3s leads and use only the female sides. Strip off about 3/4 of an inch from all 8 wires and then the 7 wires on the 6s male lead.
Here is what you'll be working with before you start splicing the wires together:
Toss the male sides of the 3s leads and use only the female sides. Strip off about 3/4 of an inch from all 8 wires and then the 7 wires on the 6s male lead.
Here is what you'll be working with before you start splicing the wires together:
Lay out the wires so that the order on the 3s side from top to bottom is: red, blue, yellow, black, red, blue, yellow black. On the 6s side from top to bottom it should be red, all whites in (not crossed over each other), then the black on the bottom. Start tying the wires together from the reds down.
I twisted and taped my wires, but I recommend soldering and using heat-shrink tubing. If you are going to twist and tape, I recommend putting the wires into a "Y" shape and evenly twisting them around each other for maximum strength.
I like to lay fold the twisted part in-line and tape very tightly to secure it in place.
The center red and black wires of the 3s leads must tie to the single center wire of the 6s lead.
Continue wiring together the leads all the way through the bottom black wires. Here's how the full charging rig looks with two packs connected:
VERY IMPORTANT: The "Red" side of the power "Y" harness must be connected to the "Red" side of the balance lead, and the "Black" sides together to match, as shown here. The red side is the pack that is directly connected to the red lead of the 6s balancer and the red lead of the power wire. The black side is the pack that is directly connected to the black lead of the 6s balancer and the black lead of the power wire. If this is not followed every time you charge, you risk ruining your charger, packs, wiring or a vicious fire. I recommend labeling the deans and balance leads "1" and "2" to avoid any confusion.
Here is a closer shot of the wiring.
VERY IMPORTANT: The "Red" side of the power "Y" harness must be connected to the "Red" side of the balance lead, and the "Black" sides together to match, as shown here. The red side is the pack that is directly connected to the red lead of the 6s balancer and the red lead of the power wire. The black side is the pack that is directly connected to the black lead of the 6s balancer and the black lead of the power wire. If this is not followed every time you charge, you risk ruining your charger, packs, wiring or a vicious fire. I recommend labeling the deans and balance leads "1" and "2" to avoid any confusion.
Here is a closer shot of the wiring.
Once connected to the charger/balancer, it will show as a 6s1p pack. Fully charged it should be 25.2v. I checked my cells out on the balancer and it was able to give me good readings for all 6 cells.
Here's the finished lead after taping it up a little better. Again - this was made with spare parts in a hotel room so it doesn't look as pretty as I'd normally like but it does the job! I kept the red and black top and bottom wires out in the open on my harness so I wouldn't accidentally connect to the wrong packs. Again, I recommend labeling the balancer and matching deans leads "1" and "2" or "A" and "B" to avoid confusion. I did Align-style balance leads but this should work exactly the same on Thunder Power-style leads. Enjoy half the charge time for 2 packs!
Disclaimer: I am not responsible for any injury as a result of or misuse of this information. Anyone attempting to build anything based on the information on this page must assume their own risk and responsibility. This is for educational purposes only and not an official guide from any manufacturer. I have no affiliation with any of the brands listed in this article.
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