Batteries Running LIPO's in Parallel

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claytonbakerjr

Member
Tony?
Long story short (reason for asking this that is)
I know I can run LIPO's in Parallel to gain more MAH but I am reading that
each pack must be (CLOSE) in VOLTAGE and C rating and size (EX: 2200mah)
Now when they say "close in voltage" are they talking 12.4 volts or
each individual cell (3.7volts)
Now the long story
I built a HEX to play around with.
In my blind rush I ordered motors that were 3S rated max.... :(
Not a big deal but I have a guy who wants to give me (free) 2- 4S 5000's
and 2-4S 4000 batteries that have been used very little. Over 150 bucks in free batteries. :)
Since I cannot use them on these motors short term I want to Parallel
my 3S 1800's so I can have a few minutes more flight time to better
get acquainted to the Hex.
Later down the road I will invest in motors that are capable of 4S
The motors I have were only 8 bucks each so I am not out a big amount
and can always turn them around to someone else.
 
RandyDSok

RandyDSok

Well-Known Member
You don't want them just close too... you want them the same voltage and capacity and preferred to be the same age so they provide the same output. Think of them in terms of balance like when you recharge a single pack...

The ideal condition is to use a set together always and never apart... married and matched together if you will from when you first get them. This way they should age the same, so the capacity draw will be the same on each as you use them and one set won't be drained quicker than the other set.

Batteries from different companies and even different batches from the same company will have different outputs when used... so different batteries will drain at different rates resulting in an unbalanced set towards the end of a charge.
 
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claytonbakerjr

Member
RDSOK
I have 4 batteries, 2-35C and 2-45C that were bought together when purchased.
They (set) are the same age, they show 12.4/12.5 when fully charged. 90% of the time
all of my 1800's show 12.4 when charged.
However the (each cell charge) varies from 4.2 to 4.19 to 4.18
Also I have read they should be charged as a set and I have also read the opposite.
 
RandyDSok

RandyDSok

Well-Known Member
They are of a different battery chemistry hence the 35C and 45C .... so despite them being the same age... they will output different amps


The other side of this is just airframe specific... using 2 batteries doubles ( or more than doubles ) the weight your airframe will be carrying which will make a considerable difference in how it flies.... If you each battery is already 1/2 of the recommended size, it shouldn't be a problem but if they are the recommended size you're throwing off your power to weight ratio and hence the airframe's performance
 
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claytonbakerjr

Member
RD
I'm sorry I may have misrepresented my post.
I plan on using both 35C's together as a set and both 45C's together as another set.
Not mixing either of the C ratings.
This is for a Hex build.
The combined weight of the 2 1800's are still less than the original 4000mah batteries
I want to purchase. Using (if possible) these 1800's until I can financially swing
the purchase of 4000 or 5000mah batteries will at least give me more air time
so that I can tweak some things I need to work on.
Currently I get about 3 or 4 minutes on a single 1800 if I can hit 7 minutes on 2
then I would be happy until I get larger MAH batteries which I am hoping will
also give me up to 10 or more minutes once all is said and done.
 
RandyDSok

RandyDSok

Well-Known Member
Then at least you are getting the idea... if used in sets you want them to be identical and the same age so they charge/drain the same... and also take into consideration the airframe so you aren't asking more of it than it can provide.

On charging... doing them together with something like a paraboard is probably best... but separately should work ok as long as you are charging them at the same rate and to the same point.
 
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claytonbakerjr

Member
Yea the Airframe should be fine.
Yesterday as I was testing she didn't seem too heavy and in fact had plenty of punch.
With what I have read and the research on this frame fully loaded with FPV gear
and Gimbal/GoPro the suggested battery is a 6500. That would almost be like a brick riding on the back LOL
Short of a larger pack I was loaded as much as she will ever get yesterday.
The 3S parallel setup will only be short lived maybe 2 weeks 3 tops and that would
be 5 or 6 flights depending on weather and time.
I need to get her up for at least 15 to 30 minutes to tweak little things like the gimbal
and some basic PID's.
Once I settle into the permanent battery solution I will finalize the tweaks.
Thanks RD
 
Stambo

Stambo

Well-Known Member
Don't forget that PIDs can change with weight, although you will probably find a good compromise between the 35c and 45c pair.
The switch to 4s will also require a retune. :)
 
murankar

murankar

Staff member
I think rdosk covered you your question. One thing to note, (which I may have missed if it was discussed) when they say close in voltage it also extends to charge left in the packs. If your 2 selected packs at a different state of charge you could have issues. For instance if 1 pack is at 12v and one at 12.3 volts you may run the risk of damaging a pack. To get them to match you would plug the charge lead (not balance) into a para board first. Let them sit for about 2 or 3 minutes to let them equalize. Then plug in your balance leads. If your withing a 10th of a volt you should be good.
 
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tommyjw6206

Member
Help me wrap my head around something... I know you add the mAh when running in parallel so 2 5000mAh batteries performs like a 10000mAh battery. But if both are 20C, does that make it a 40C equivalent?
 
holtneil

holtneil

Active Member
Hi Tony it does if you run in series then the mah and C stay the same but volts go up and in parallel the mah and C goes up volts stay the same I never thought of that till now just worked on volts and mah , God you know so much :notworthy:
 
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