To stay in the air for as long as possible, you’ll need to have as many batteries as you can afford(or can carry!)
Now lipo batteries take quite a while to charge, since the safest current to charge the battery at is 1C – or the amount of amp-hours the battery’s capacity is.
For a 1500 mAh(1.5 Ah) battery, that’s at 1.5 amps.
Usually, when I charge my lipos at 1C from about 3.7 volts, it takes about 30-35 minutes to reach full charge at 4.2 volts.
Now you could charge at 2C and charge faster, and some batteries are even rated for 3+ C charging, but I am not too keen on that unless it’s an emergency and you need to quickly get into the air.
However, when you want to charge multiple lipos at once, you can do something called parallel charging.
How parallel charging works
In parallel charging, you hook up multiple batteries together to get a large parallel circuit. Essentially, you combine a number of batteries to make one large battery.
All the positive terminals get hooked up together, all the negative terminals get hooked up together, and the balance leads get hooked up together, too.
That’s why you can only charge same-cell batteries in parallel.
YOU ABSOLUTELY CANNOT AND MUST NOT MIX CELL COUNTS. THE RESULT IF YOU DO SO WILL BE VERY BAD INDEED.
Most parallel charging boards take up to 6 lipos. So when you plug 6 4S 1500 mah lipos into the board(and balance plugs too), you end up with effectively one 9000 mah battery.
Since all the balance leads are also connected, each individual cell is connected into one large cell.
You’re left with one 9000 mah battery with 4 cells.
When you charge now, you can charge all the batteries together at 9 amps instead of the 1.5 you would have been limited to earlier, so you’ll charge 6 lipos in the time it would have taken you to charge just one.
How to parallel charge safely
When parallel charging, you need to keep some safety guidelines in mind:
- Never parallel charge lipos with different cell counts
- Don’t parallel charge lipos with large capacity differences(some guys say charging a 1300 and 1500 together is fine, but I would not charge a 2200 and 1300 together)
- Always check the voltages of each battery before charging them together. Generally speaking, you can charge packs if they are within 0.1 V of one another. Some people tolerate 0.2V too, but I feel it’s safer to stick to a lower difference.
- It’s also a good idea to make sure each individual battery is healthy, too, and the individual cell voltages are not too far apart from one another. If you happen to find a questionable battery, charge it separately.
- Before you plug the lipos into the parallel charging board, remember to make sure all the balance pins on the board are straight and not shorting out anywhere.
To start charging, measure your lipos individually with a cell checker and see which can be charged together. Plug them all into the parallel charging board, along with their balance connectors.
The parallel board will likely have sets of connectors for 2 cells up to 4 or 6 cells – so you can charge whatever cell capacity you have.
Now plug the main lead coming out of your parallel board into your charger, and the balance lead as well – the balance lead from the board may have more pins than the battery you are charging, but that’s OK – the charger will only pick up the number of cells the battery actually has.
Add up the total capacity of the batteries, and set that as your charge current.
Select the correct cell count(whatever each individual battery is). If you’re charging 4S packs, then you’ll select 4 cells.
REMEMBER, in parallel charging, ONLY THE CAPACITY IS ADDED TOGETHER. THE CELL COUNT REMAINS THE SAME!
An extra precaution
A neat bonus of connecting batteries in parallel is that the batteries will automatically equalize themselves. If you leave a few batteries plugged into a parallel charge board, you will see that after 10-15 minutes, all the batteries will have the same voltage(as will their cells).
If my batteries are not the exact same voltage, I tend to leave them plugged in to the parallel board for a short time before charging to let the voltage equalize, then I start the charge.
However, if your cell voltages are too far apart(greater than 0.2V), do not use this method. The electrical pressure from the higher voltage battery will be much greater than the one in the lower voltage battery and things can go awry.
How many batteries can I parallel charge?
Even though most parallel boards have 6-7 connectors, you can actually charge as many lipos as you want in parallel – you are not limited to 6.
One board can be used to charge anywhere from 1-6 lipos, and if you need to charge more together, you can simply plug a second parallel board into the first one as if it was a battery.
You can then plug a third into the second, and so on.
Really, the only limitation to how many batteries you can parallel charge at once is the output capacity of your charger.
Your charger can only output a maximum number of amps. Ideally you’ll want to charge at 1C, so if you want to charge 10 1300 mah batteries together, you need a charger than can charge at 13 amps.
Note: You can charge more packs together at less than 1C too, but it will just take longer.
Before you buy a charger, you’ll be able to see the maximum output capacity it has. If your charger uses an external power supply, then you’re also limited by the amount of power the supply can provide!
Best parallel charging boards
Parallel charging boards are pretty straightforward. You just want to keep inspecting it to make sure that no pins have bent and started touching.
And if you want the big kahuna of parallel boards, then the Joshua Bardwell board is a fused board specially adapted for race quad size batteries.