thunder
Guys,can I put a 4s 3500 10c lithium iron battery in parallel with a 4s 25c lipo ? thanks
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Grantman
Yes you can as long as you don't exceed the discharge rate of the weaker battery, otherwise puff-puff.
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Argonath
Ideally if you intend to put LIPO's in Parallel they should be the same rating. This will extend battery time for flight.

As Grantman has already stated though, you can only run up to the lower C rated battery otherwise the added draw will cause the lower C rated better to puff out or even potentially catch fire in use.
D.I.L.L.I.G.A.F.
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thunder
The reason I ask about this is because when I put the 10c lithium iron battery on my tricopter the lipo alarm goes crazy as soon as the tricopter lifts off,but if I put a multistar 10c lipo on the tricopter the alarm is quiet until the multistar lipo starts going flat,,both batteries are the same c rating,,and I thought that parallel connected batteries was the solution.
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Wildthing
Possibly the one might have 1 weak cell or even a bad connection on the parallel plug
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thunder
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Possibly the one might have 1 weak cell or even a bad connection on the parallel plug

I have not tried a parallel connection yet and both batteries work great individually,the lithium iron battery 3500 4s 10c gives me about 9 or 10 mins flight time on my trex 450 and the lipo alarm stays quiet until the battery starts to die. Could it be that the lithium iron battery has not been cycled enough times ?
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Wildthing
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I have not tried a parallel connection yet and both batteries work great individually,the lithium iron battery 3500 4s 10c gives me about 9 or 10 mins flight time on my trex 450 and the lipo alarm stays quiet until the battery starts to die. Could it be that the lithium iron battery has not been cycled enough times ?

Do you have a watt meter so you can watch the voltage on each cell when powering up the Trex? Or maybe the alarm just doesn't like the lithium battery
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thunder
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Do you have a watt meter so you can watch the voltage on each cell when powering up the Trex? Or maybe the alarm just doesn't like the lithium battery

No I don't have a watt meter but your suggestion that the alarm does not like the lithium battery has got me thinking,i have several alarms but I have been using one particular alarm for quite a while,i gona try the other alarms,,thanks for that
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KK
I agree with Jeff here that the lipo may appear fine on alarm when it doesnt have any load on it. However, when you apply load (i.e. run your motors with prop on) the cell cant keep up triggering the alarm...

Most alarms will tell you which cell has low voltage suggesting how many bad cells you have in a lipo...
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Wildthing
I do have one battery where the cell shows perfect and soon as you power up the motor it's voltage drops way quicker then the rest, give it 30 seconds rest and the voltage climbs right back up to normal. But, I don't get decent flight times with it so it is in the recycle pile so that is why I am thinking it might be the alarm itself.
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Argonath
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Possibly the one might have 1 weak cell or even a bad connection on the parallel plug


My thought exactly.
D.I.L.L.I.G.A.F.
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Argonath
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The reason I ask about this is because when I put the 10c lithium iron battery on my tricopter the lipo alarm goes crazy as soon as the tricopter lifts off,but if I put a multistar 10c lipo on the tricopter the alarm is quiet until the multistar lipo starts going flat,,both batteries are the same c rating,,and I thought that parallel connected batteries was the solution.


Does your charger have a balance charge where it shows you the charge state of each of the cells when it charges? This could be one cell that's defective or they could simply need to go through a balancing to stop the alarms.

However, my instinct tells me it's more likely a defective cell in the battery.
D.I.L.L.I.G.A.F.
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TomMonton
Simplest solution:

... buy two batteries.

If there's "any" chance of failure under load or otherwise, I would not want them in my fleet.
Fly like your mad at it.
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Grantman
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However, my instinct tells me it's more likely a defective cell in the battery.


This. I've had a few batteries with one cell that takes a "surface charge" and appear fine, right up untill they're under load and that one cell would sag brutally.
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Skydiver
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Simplest solution:

... buy two batteries.

If there's "any" chance of failure under load or otherwise, I would not want them in my fleet.

Just be sure that both batteries are exactly the same, and not two different manufacturers, or types.. Even slight differences can be trouble. Lithium Polymer is not the same as other rechargeable batteries either..Crash and burn is not a pleasant sight...
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