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Aug 16, 2019, 09:03 PM
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Thread OP

Repurposing high IR LiPoís?

Hi all,

Iíve been out of RC for a year or so, and all my LiPoís have just been sitting at storage charge in a cupboard. Iím doing a bit of Astrophotography and need some 5v & 12v portable power supplies for equipment.

Iíve just been going through my LiPoís (1S, 2S and 3S up to 2200mah) see what sort of condition they are in, and while they still have their charge, the individual cell IR on most of them is a bit high. Theyíre ranging from 7 at best, to about 42 at worst, most around 15-20, but that is at their stored voltages around 3.8v per cell. Iím not sure. If charging to full charge will give a different IR, but Iíve got the worst one on now to see. Itís a 3S 2200 that Iíve had for years, although it isnít showing any sign of puffing, but the IR values are 32,34,42, so is pretty bad.

So I know the recommendation is over 20 is dead, but everything Iíve read talks about that in RC usage. Some of my telescope gear requires for example, 12V but only 0.5A, and would only be driven occassionally when the telescope moves between objects for example. So, do you think I could repurpose these ďRC DeadĒ batteries as power supplies for the various components I have? Iím not sure how the high IR values will affect run time for low current, low usage equipment.

Thanks. Russell.
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Aug 16, 2019, 09:38 PM
Space Coast USA
hoppy's Avatar
Shouldn't be a problem.
Charge the packs and do a 1C discharge to 3.3V/cell and see how much capacity you get.
Aug 16, 2019, 10:43 PM
Registered User
Thread OP
Cool thanks.

So the IR of that pack when fully charged and rested for a while now reads 19, 19, 24. Big difference to the previous reading. The last cell obviously has issues. It was always 0.2v-0.4v behind the others while charging.

I’m now running a discharge. There must be a limit on the discharge current though. It’s set to 2.2A, but the readout only shows 1.2A. Maybe the charger can’t handle a higher discharge rate? It’s a standard icharger 106b+.


Meh, I had a safety cutoff in place so it stopped discharging at 3.7v and I lost the discharge reading. Oh well, I’ll give it a real try when I can and see how it goes.
Last edited by BoomerangRuss; Aug 16, 2019 at 11:53 PM.
Aug 17, 2019, 07:51 AM
Registered User
I have done this. I have several older Lipos that have higher IR than they did when new. They still charge and discharge fine as long as I keep the discharge currents reasonable. I fly them in my planes that don't tax the C rating. I also use them to power projects that I have.
Aug 17, 2019, 03:02 PM
Registered User
Thread OP
Great, thanks.
Aug 18, 2019, 04:04 AM


You can use your old batteries to charge your phone, tablet, action cam or 1S-batteries with this little power converter.
Aug 18, 2019, 09:56 AM
Registered User
I use old batteries for my fuel pump and as external packs for my transmitter. Anything with a low current demand is fair game.

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Aug 20, 2019, 12:28 PM
Redbilly Band Member
Ron H's Avatar
I have a few old ones that can only do about two amps now. I use them to power an LED dc shop light. It's handy when the power is out too, but it gets used mostly because it's so easy to use. No cords, and you can take it anywhere.

Even fishing. The last time I went night fishing we had it in the boat and the trolling motor battery went dead, so I connected the light battery to the trolling motor after disconnecting the Pb one of course.

The light + the motor (on low speed) drew 1.8 amps, no problem for the old packs. We stayed close to shore and fished around docks just in case, but the 3s3000 pack was still doing fine when we decided to call it quits.

The boat owner was astounded that a battery that can fit in your pocket could even propel the boat, and I'll have to admit that I was surprised at how long it lasted even after doing the math in my head.

BTW, this is a fishing story so it's not over yet.

We get back to the ramp and load the boat on the trailer and find that the trailer lights aren't working. So I snipped the wires on the trailer and connected them to the same pack to get the running lights on. No brake lights or signals, but we made it home.

Then we unloaded the boat, put the Crappie in the fridge and went to bed.

Next morning, I notice that the lights are still on so I run out to unhook the LIPO. 3.6 volts resting after all that.
Aug 20, 2019, 04:20 PM
Frankenstein recycled packs
rampman's Avatar
Whoa!!! Now THAT's a fish story.
Good read. Why fill the landfills if a lipo can still be used. I LOVE IT

Aug 20, 2019, 04:41 PM
Registered User
If you use a lipo like this you should hook on of those low voltage alarm beepers to it to warn you if it gets too low. It's easy to miss that when you use it in a low current application. (Been there, done that)
Aug 21, 2019, 11:52 AM
Registered User
Mine end up becoming test batteries or using them for goggles or transmitter. I have one that is powering leds and a racegate.
Aug 21, 2019, 01:19 PM
Registered User
If they are the right number of cells they make good goggle batteries since the discharge rate on goggles is pretty low.
Aug 22, 2019, 11:39 AM
Registered User
KMatch's Avatar
I was wondering regarding the original post above: The reference to the batts being bad due to IR being over 20. Am I right to understand that was a misunderstanding and the 20 IR was being mistaken for the life of a lipo being used up with a 20% loss in capacity instead?
Aug 22, 2019, 11:55 AM
Registered User
Originally Posted by KMatch
I was wondering regarding the original post above: The reference to the batts being bad due to IR being over 20. Am I right to understand that was a misunderstanding and the 20 IR was being mistaken for the life of a lipo being used up with a 20% loss in capacity instead?
My experience is that properly cared for Lipos increase in IR more than drop in capacity. The max IR that you can tolerate depends greatly on the capacity of the Lipo and it's C rating. Smaller batteries have much higher IR to start with. Lower C rated Lipos have higher IR to start with. I have some that have doubled in IR since they were new. I still use them in planes that don't tax the current rating but they will overheat and fail in a higher current demand plane.
Aug 22, 2019, 12:00 PM
pull up -- PULL UP!!!
I use large, non-flight-worthy batteries to field-power my ISDT charger. The large batteries seem to retain decent capacity and the draw requirements to charge small park flyer batteries is minimal. A good match. Some of those batteries are off-scale/high on my ESR meter and still work fine.

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