Knackered battery? How to test?

[Euclid]

One of my 800mah lipos doesn't produce enough umph to keep a 200 SRX into the air after about 2:30 of flying time when its charge is shown to be about 65% using one of those £10 charge/balance checkers. I'm guessing the battery's internal resistance has increased (if I remember my battery theory from decades ago) but how do I check to confirm? I am using an iMax 6 charger and/or the wall-wart charger that came with the 200. The iMax charger is due for an upgrade sometime this year or next but my charging requirements are not particularly demanding. If the next charger can give more information on the internal health of each battery so much the better. So is there any way of checking a battery's health?

[waveydavey]

Either a charger that gives the IR reading (normally on the good news side) or a Wayne Giles Meter which will give you a very accurate IR reading. But seeing as the batteries you're using are cheap then the best way is to chuck them if they're not doing what they used to

[Mike656]

I normally put the Heli into a big loop using full collective. If it runs out of steam at the top, usually a good indication to get a new battery.
You can get gizmos to test internal resistance, and some chargers can work out the IR while charging, but then, what do the figures really mean?

[Euclid]

Cheers guys, Wayne Giles, there's a new phrase for my vocabulary, some reading to do this week I think. I've three new batteries on the way so I guess a side by side comparison will take place next weekend then quite possibly into the bin for the troublesome one.

[10x]

I have a Wayne Giles meter but last year at the Hobbyking show at Elmsett airfield i bought one of their IR meters to see what it is like and its readings are very close to the WG meter.....You have to make up adapters as it has a xt60 socket, but you do also if you have more than one battery plug with the WG....

Turnigy LiPoly Battery IR Meter (UK Warehouse)

But this meter will put a 10amp load so may be too much for your batteries, in that case WG does a small battery meter...

ESR (Equivalent Series Resistance) Single Cell Meter For Testing Small 30-1000mah Packs Designed and built by Wayne Giles « ElectriFlyer

[Grumpy]

The simple way is put another battery in the heli. If it flies ok with the new battery then obviously the old one is knackered. Given the price of small LiPos it really isnt worth buying fancy IR checkers as they cost far more than a replacement battery.

[kenny d]

I have a Wayne Giles meter but last year at the Hobbyking show at Elmsett airfield i bought one of their IR meters to see what it is like and its readings are very close to the WG meter.....You have to make up adapters as it has a xt60 socket, but you do also if you have more than one battery plug with the WG....

Turnigy LiPoly Battery IR Meter (UK Warehouse)

But this meter will put a 10amp load so may be too much for your batteries, in that case WG does a small battery meter...

ESR (Equivalent Series Resistance) Single Cell Meter For Testing Small 30-1000mah Packs Designed and built by Wayne Giles « ElectriFlyer

Ive got the turnigy ir meter , IMO it's well worth £20 , does voltage & IR , shows up bad cells often confirming what you already suspect lol

[Euclid]

Thanks for the answers, it seems the obvious answer is just to ditch the battery especially as I've three in the post to me as I type. That said the Turnigy IR checker seems an interesting little gadget for not a lot of money that fits nicely into the 'want not need' category.

[Peteski]

If you are going to upgrade your charger, then it will almost certainly have a built-in IR checker, so you may find the Turnigy gadget a waste of money. For example I have a small iCharger 106B+ that can measure IR of individual cells. But to make any sense of the measurements you have to measure IR when the packs are brand new as a reference. But once you can tell that a pack is under performing in flight, then it's time for the bin whatever the numbers might say.

[cycled]

It's not trivial interpreting the IR numbers however, because they will vary a lot depending on the temperature of the battery and size (larger cells can handle more current, thus must have lower IR). Maybe you could assume the voltage drop across the battery would be the same across all sizes and use V=I*R (where R=resistance, "IR" above), but probably the "C-rating" would be different too.

Easiest just to compare with a new battery (where also larger may have more power but will also make the heli heavier).

[kenny d]

I have a pl6 & pl8 which read IR but I find the turnigy IR tester much better & easier to use , I find when a battery starts to go off it's usually one cell that goes first
so you can clearly see it with the IR tester

[Euclid]

Thanks Pete, cycled and kenny. As ever there's a plethora of answers all equally valid. Perhaps I should just concentrate on improving my flying (difficult when you are hardly ever at home) rather than worrying on the minutiae of what's going on under the bonnet. That said it is always nice to know whey something isn't behaving as expected so as a starting point I think the 'pocket' tester could well be added to my tool kit. In the meantime I've three new batteries waiting for me at home, it'll be interesting to compare old with new.