Unsure how to charge multiple batteries at once.

[James75]

Hello,

thanks in advance for any advice, just after a bit of guidance on charging. I am pretty new to the hobby, can't do much more than some ropes tail in figure 8's !

I now have 4 batteries and charging them individually is starting to become a bit of a bind, I know they can be charged together, but I have an inexpensive Turnigy Accucell 6 charger which is only 50w, is it possible to buy leads so that I can charge at least some of them together, admittedly it would be on quite a low amperage due to the low power of the charger but at least I could them done in 1 go.

Thanks James.

[waveydavey]

Hi James, what packs, what power supply, what connectors etc

[Gecko501]

Unsure how to charge multiple batteries at once.

Think you will need to give more info here. What lipos are you talking about here for starters?

[RcRotaryMadness]

Heres a video I stumbled on the other day:

[waveydavey]

A great site for all things leccy

Electric RC info, how-tos and such - TJinTech

[James75]

Sorry, they are 3s 11.1v 2200mah lipos, cheers.

[James75]

The power supply is just a 12v one that came with the charger but the charger is limited to 50w, the connectors are deans plus the balance plug, obviously. I didn't know if I needed a more powerful charger?

[DaveJones]

Unsure how to charge multiple batteries at once.

You don't give much info to go one, whether your 50w charger is up to the job or not will largely depend on how big your batteries are. Assuming you are flying a 450 size heli with 3 cell batteries you could probably charge two batteries in parallel at the same time you charge one today.

50w/12v = 4amps, assuming 1500mAh batteries parallel charging would need only 3amps for two batteries.

You would probably see a reduction in the total charge even if you charged all four batteries at around 3.5a due to the way the final stages of the charging cycle work. I wouldn't recommend running your charger flat out at 4amps, it will get very hot and you will shorten its life, same goes for your power supply.

Do a search on this forum or on google for parallel charging and you should find a ton of information on how it works and what you need to buy.

Perhaps an easier option is to consider charging at a higher rate, I regularly charge at 2C, you should see a big drop in charge time.

When you get comfortable you could then look at a bigger charger, I charge 6 batteries at 2c and can have all six charged in about 30mins.

[James75]

You don't give much info to go one, whether your 50w charger is up to the job or not will largely depend on how big your batteries are. Assuming you are flying a 450 size heli with 3 cell batteries you could probably charge two batteries in parallel at the same time you charge one today.

50w/12v = 4amps, assuming 1500mAh batteries parallel charging would need only 3amps for two batteries.

You would probably see a reduction in the total charge even if you charged all four batteries at around 3.5a due to the way the final stages of the charging cycle work. I wouldn't recommend running your charger flat out at 4amps, it will get very hot and you will shorten its life, same goes for your power supply. .

sorry I think we were posting at the time, batteries are 3s 2200mah, I don't mind if they charge quite slowly but just want to be able to do the all in 1 go. Just watching the vid that Young Gun posted and the person there is saying that all the batteries will be balanced correctly ? Do not agree ? What charging set up are you currently using ? Thanks for your reply by the way, lots of info.


Cheers James.

[DaveJones]

Unsure how to charge multiple batteries at once.

Never had any balancing problems just make you only charge similar type batteries together ie same cell counts.

I bought a parallel charging board from HK for a few quid, you simple plug it into the charger and connect the batteries to the board and add up the capacity of the batteries you have plugged in to get your charging current. Something like this

http://electriflyer.co.uk/deans-parallel-balance-board/

[James75]

, you simple plug it into the charger and connect the batteries to the board and add up the capacity of the batteries you have plugged in to get your charging current. Something like this

Deans – Parallel Board « ElectriFlyer

Thanks Dave. If my maximum charging current of the charger is less than the total when I add up the capacity of the batteries, will that be ok ? I appreciate that it will charge at an rate which is effectively less than 1c so it might take a while but they will be done in one go. Long term I am going to need a better charger but I would like to try and get away with what I have whilst I only have a 450 heli, I will need a better set up when I progress to bigger helps though.

Cheers James

[cjcj1949]

You can also charge in series. It is better for the batteries and safer as it is the normal way we charge a single battery. The volts don't need to be checked and if a cell goes down the charge will stop rather than cause a fire. You do have to plug the balance lead into the right connector. The icharger comes with a series adapter and it is very good for 2s cells that can be charged through the balance leads. Parallel charging isn't a recommended way of charging, the closest recommendation is from Cellpro/FMA who sell a safe adapter with fuses in case things go wrong. All lipos go wrong eventually and older lipos should be charged on their own.

[450man]

Correct me if I am wrong but when batteries are connected together in series don't you add together the voltage and when in parallel you add the current?

In that case, the main benefit of parallel charging is that the voltage is kept within the range of your charger. If I series charged 6 x 3S batteries won't my charger need to be able to charge at up to 75V? Not many chargers can do that. With parallel charging you can charge as many packs of the same cell count together using the same charger... they just take longer.

For example... If I connect 2 x 3S 2200mah batteries together in series I get a single 6S 2200mah battery. I therefore will need a charger able to charge a 6S battery. If I do the same with 3 x 3S 2200mah batteries I create a single 9S 2200mah battery and most chargers can't charge a 9S battery so the maximum 3S batteries you could charge together using series charging is generally 2.

Compare that with parallel charging... conencting 3 x 3S 2200mah batteries in parallel you create a single 3S 6600mah battery and so any charger that can charge a 3S battery can charge any number of 3S batteries in parallel.

Series charging is generally not possible for more than 2 x 3S as most chargers on the market today can only charge up to 6S.

I wouldn't argue about the relative safety... you clearly know more about that than me... however, in spite of the disadvantages, most people parallel charge so they can use their existing chargers.

[cjcj1949]

Parallel charging is more convenient. As you say most people have only 6S and so 2 X 3S or 3X 2S is the most that can be done. Considering the cost of the high current chargers, the quad chargers are reasonable. Parallel charging is perfectly safe if nothing goes wrong. Single battery charging can catch some faults, that's why each cell is monitored. If you put cells in parallel then when one cell has a breakdown voltage below 4.20V, ie a cell appears to stop charging at a certain voltage, a charger will catch that. But if lots of other cells are in parallel, much higher currents will be drawn into that cell. This sort of breakdown usually gets worse and the breakdown voltage goes down. There is then no limit to the current flowing through that cell. So a minor problem that would have been noticed as a failure to balance, becomes a fire. Not just one cell either but all the batteries stacked next to each other. Still if the charging was being watched through all the few hours of the more convenient process, it would be picked up. Chargers go wrong as well. It's not really the safety, it's more the assumption that because it works, it's ok. People have taken a process that was so hairy that all chargers carry a warning about constant monitoring, and made it less fault tolerant, and then fail to warn new people of what they are getting into. Nothing wrong with lipo charging except that they cause fires from time to time and don't need any encouragement. The best piece of advice I've seen from someone who uses parallel charging is to check the lipos on their own on a regular basis and only to use good lipos. After the lipos are connected together, the current doesn't divide equally, it does it in the ratio of the internal resistances. So the best battery gets most of the current.

Parallel charging can be made as safe or safer as normal charging. It is not difficult. You just need to be able to isolate batteries that are failing and not cross couple faults by linking balance connectors. I'm playing with Atmega things at the moment in order to monitor ordinary chargers.

[James75]

Thank you all, plenty of info to digest here, if I do parallel charging I'll follow the advice. I check the voltage of all cells after every flight and all my batteries are pretty new so I should be ok if I monitor things closely. Thanks again everyone.