I’ve received much mail asking about parallel charging and whether or not it’s safe. Other questions focused on not being able to parallel charge at the rate the charger is supposed to support. Both of these topics boil down to a little education, and I hope to do just that.
What is Parallel Charging?
Parallel charging is simply connecting multiple packs to a single charger and charging them all at the same time. This is done through the use of a custom charging cord or a special parallel board.
I prefer boards because they include balancing plugs, whereas some of the charging cords only allow for the charge wire and not balance. I always advocate balance charging, especially with parallel charges.
Is Parallel Charging Safe?
It is safe, but as with everything else, you must do it properly. That is one reason I advocate using a charging board that includes balance plugs. It is as safe as any other charging method if you set it up and do it properly … just like all LiPo charging requires.
Parallel charge boards come in various configurations regarding plugs and some protect each output with a fuse. Your choice depends on the equipment you have or how much you want to spend.
Understanding How It Works
When multiple packs are connected in parallel to a charger, the charger sees it as one big pack having the capacity of all the packs added together, but with the voltage of a single pack. All packs must be the same cell count! You cannot mix 3S packs with 4S packs, etc.
The packs do not need to be the same capacity. You can put a 2,200 mAh pack in parallel with a 1,800 mAh or a 1,000 mAh pack, etc. I generally group mine together according to similar capacities, but it’s not a big deal.
I typically connect all the battery wires to the parallel board before connecting the balance plugs, but I have one charger that recommends connecting the balance plugs first when using its board. Be sure to read the instructions for your charger and board before trying it.
The logic behind connecting the larger battery wires first is to allow the cells to equalize through that wire if there are some packs significantly lower in voltage than the others. You should try to parallel packs that are close in voltage. Don’t charge one that is almost fully charged in parallel with packs that are completely discharged.
After you’ve connected all of your packs, set your charger for the proper charge voltage and current. Remember, regardless of how many packs you’re charging, the voltage is the same. If you’re doing six 3S packs, then the voltage is set for a 3S pack or 11.1 volts.
If all of the packs are 2,200 mAh, then multiply that by the number of packs to get the total capacity. If you’re doing six 3S 2,200 mAh packs, the charger would be set for 3S (11.1 volts) and 13.2 amps (6 x 2,200 mAh=13.2 amps). Likewise, if you’re doing six 6S 5,000 mAh packs, the charger would be set for 6S (22.2 volts) and 30 amps (6 x 5,000 mAh=30 amps).
I always charge at 1C even if my packs are rated for higher charge rates. It’s easier on the pack, but charging at full rate is your decision. The same rules apply, so if you’re doing those six 6S 5,000 mAh cell packs at a charge rate of 2C, you’ll need to have a setup capable of providing 60 amps. (6 x 5,000 mAh x 2C=60 amps).
Why Bother?
Time and convenience! My chargers can charge, discharge, and provide a storage-level charge. I always leave my packs at storage levels (around 3.8-volts per cell). If I want to fly, I can put six packs on to charge while I’m getting everything else loaded and they’ll be ready in no time.
Because I have multiple chargers, I can do a lot of packs in a short period of time. When I return from the field, I can set them all to return to storage level. Storing packs fully discharged or fully charged considerably shortens their lifespan. Treating them with loving kindness saves money in the long run. Because I’m bringing them up to full charge from storage level, it doesn’t take a full hour either, so it’s a quick process on flying days.
It's Not Just for Big Packs
Many of us have several micro-size airplanes and helicopters that use one-cell packs. These packs generally don’t last long and leaving them fully charged really decreases their lifespan. Using a parallel setup and keeping them at storage level until ready to charge and fly greatly helps. Now you can pop six of them on a charge setup and be ready for multiple flights.
Possible Problems
The most common problem is not having a setup that provides the voltage and current required for parallel charging large packs. Everything looks good until you try to charge and don’t understand why the charger is set for 30 amps, but it’s only putting out 10 amps or another lower setting.
Looking at the big setup referenced earlier, the six 6S packs require a total of 30 amps from the charger, so it provides 5 amps for each of the six packs. Remembering Ohm’s Law, we know that 30 amps x 22.2 volts=666 watts. If you’re trying to power your charger with a power supply that is rated for 150 watts, you don’t have enough power.
At 22.2 volts, that 150-watt charger can only provide 6.7 amps or 1.13 per pack. For my large charging requirements, I use a 24-volt power supply and my charger is an iCharger 3010b. Doubling the available voltage helps and the Mean Well Power Supply is rated for 1,000 watts.
If you decide to use one of the larger power supplies, be sure your charger is capable of 24-volt input or you’ll quickly destroy it. I labeled the output on my charge box to be sure nobody plugs a 12-volt charger into my 24-volt box.
Wrapping It Up
I love parallel charging and it’s safe and efficient. I no longer have charged packs left lying around because I had charged them “just in case.” I can quickly get everything back into storage mode after I return from the field. The cells are happy and so am I.
For more information about parallel charging and an extensive selection of boards and gear, give the people at ProgressiveRC a call. The company’s tech support is excellent and it carries everything you need to get set up—from a beginner charging station all the way up to the maximum, mega setup. Be sure to check out the video section; it’s very thorough.
