Parallel LiPo Charging – The Faster & Safer Way To Charge?
At the end of the page I have included several links to the actual parts I used when building my parallel charging harnesses if you decide this is a charging method that is right for you and need an inexpensive parts source. If you would rather just purchase "ready built" parallel charging harnesses, EP Buddy has a great selection and very good pricing - click here to check them out. Parallel LiPo charging allows you to charge more than one battery at the same time with your computerized RC battery charger. The big advantage of parallel LiPo charging is it saves time since you can charge your entire heard of LiPo batts on one charge cycle and is considered by most to be safer than serial charging (one pack at a time). Parallel charging will only work on same cell count batteries, but they can have different capacities (within reason). They can also be at different states of discharge - again within reason. You wouldn't want to try and parallel charge a pack that was 5% discharged with one that was 50% discharged for example. No more taking one pack off when it is finished and then hooking the next one up and starting the charge cycle all over again. The important thing to remember is the battery packs all have to be the same cell count. You can’t parallel charge a 6S pack with a 4S pack for example - all packs in the parallel charge circuit must be of the same voltage rating. Words Of Caution! This is an advanced method of charging and requires a certain level of electrical understanding. If you are not comfortable with charging calculations, wire sizing, your ability to build safe parallel charging and balancing boards/harnesses, or keep your wits about you when hooking up the batteries, please don’t attempt it. As was discussed on the LiPo battery page , lithium battery chemistry is a volatile mixture. One battery starting on fire because of unsafe/improper charging is bad enough, never mind several batteries all hooked up in close proximity to each other! If you choose to charge this way, just like charging any lithium based battery, you do so at your own risk and never unattended. How does it work? First you will need to build or purchase a parallel charge plug or board that the charge leads from each battery will be plugged into. The positive from each plug is hooked to positive and the negative of each plug is hooked to negative (parallel circuit). To keep things in reason, most will only build a plug or board that will support up to 5 or 6 batts maximum.
How To Build A Simple Parallel LiPo Charging Board or Plug 
The picture above is showing a parallel charge board I built that supports all my LiPo packs that have Deans connectors. As you can see on the back side of the board, all the plugs are wired and soldered in parallel.
The reason I built a board over a multi plug is so the male ends of the Deans plugs can’t short against each other (one thing I really don't like with Deans connectors). 
After you build your board, make sure you insulate the back side of it. I for example just used several layers of fabric hockey tape. 
Here is the
EC3 connector
parallel charge plug I built and since EC3 connectors are insulated (better safer plug in my opinion), I didn’t bother using a board and just wired them all up in parallel.One thing I should point out is the size of the wiring, especially the main wire from the banana plugs (red/black) to the connection point of the 5 EC3 plugs. I could theoretically be pushing 20 amps through this wire so it has to be a fairly good size gauge. I am using 14AWG and this seems very adequate. It only gets a little warm at a full 20 amp current load and the voltage drop over the very short length of wire is insignificant. 14AWG is also the size of the wiring used to power my charger, so that is a pretty good way to "gauge" it :) 
Hear is another example of a parallel charging harness I built that supports all my smaller LiPo packs that use JST connectors. How To Build A Simple Parallel Balance Board 
Next you will need to build yourself a parallel balancing board or harness. I am first going to show the board I built and then a harness. Again, just as with the charge plugs, you generally need no more than 5 or 6 balance plugs to keep things in reason. As the name suggests, this board is also wired in parallel as you can see in the above photo.
The board I built here uses 6S JST-XH balance plugs since most of my LiPo packs use JST-XH balance taps and JST-XH plugs have a nice advantage... you can (with a little persuasion) fit different plug counts into the plugs.For example, a 3 pin balancing plug will still plug into a 7 pin plug. This is nice so you don’t have to build several balancing boards with different plug pin counts. I also have a few FlightPower and ThunderPower packs that use Thunder Power Taps, so needed to get a few TP to JST converter plugs. The parallel balance board you built will now plug into the Chargers balance board. 
Here I have my parallel balance board plugged into the 6S plug on the balance board that came with the charger enabling me to parallel balance everything from a 2S pack to 6S pack. If I ever get into 7S, 8S or higher, I will have to build a new parallel balance board, but for now, I am very content with nothing larger than 6S packs.How To Build A Simple Parallel Balance Harness 
Here is another parallel LiPo charging balance method that will work and I find easier to both build and hook up. With a balance harness like this over a board, it is easier to hook up all your balance taps, especially if your batteries have short balance leads.The first step is to get a number of female balance plugs with wiring on them if possible. Having the wiring in place saves considerable time. The
6S JST-XH
ones I am using here came with Kokam male ends (they are actually a balance adapter) but they come in packs of 5 for less than I could get single ends for anywhere. 
Once I have all the wiring sorted and soldered it is time to solder on the single male balance plug end that will plug into my chargers parallel charge board. As it turned out, all those Kokam male ends came in useful for this.
I just shaved the orientation tabs on the sides off the Kokam plug and swap the black and red wires so the polarity was correct. Now I have a 6S JST-XH parallel balance harness that plugs directly into my 208B charger's balance port making the hookup a little neater.Basically when you have everything hooked up in parallel like this, your individual packs now have become one big capacity pack. For instance, if you hooked three 2200 mAh 3S packs all up in parallel as I have done here, they essentially become one big 6600 mAh 3S3P pack.
Of course you don’t have to charge at a 1C or 2C rate, lower charge rates are always safest so a 0.5C rate of 3.3 amps (41 watts) will work just as good, it will just take twice to 4 times as long to charge. Hopefully that gives you a little background and understanding on parallel LiPo charging and one method of how to do it. As I said in the opening paragraph, the main reason I built this page was to show you why a higher power charger, even with smaller battery packs, may be a good long term investment. Here is a good video I found of a LiPo parallel charging procedure... Links To Several Parallel LiPo Charging Build Parts:
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Just like the parallel charge board, ensure you insulate the back side of the parallel balance board so it won’t short out on anything.
I just cut the Kokam ends off and went to work soldering all the leads off the 6S JST-XH female plugs in parallel. Mounting them all lined up in the correct +/- orientation in a small vise as I have done here while working on each branch of wiring keeps things neat and mistake free. Also note I have heat shrink already in place for insulating the solder connections when I put the male balance plug on.
