Internal resistance.

[ched]

Just bought a 4 new battery charger .
It does internal resistance which my old charger did not.
So I thought I would have a play.
All my batteries are in storage charge so I plugged them in one by one and wrote down the cell resistance. While I know different chargers do give different values, ones from the same charger should be comparable.

The results are that while my 'good' batteries are within quite a range (5-32 milliOhms) my naff ones are significantly higher (84-100 milliOhms).

I had 4 new Turnigy Panther Graphenes arrive yesterday and had put them at storage V. So they have had zero flights just a bit of charge to storage. They didn't seem great on the balance (about 0.03v variation). Their internal resistances range from 5 milliOhms to 48 milliOhms which seems too big a deviation. Maybe I should just try again after first flights?

So anyone monitor their lipos internal resistances? Have you found anything interesting or is is almost a waste of time testing them?

Cheers

[Bad Raven]

Do I monitor? Well, no, not as a hard and fast routine, too many packs, too many sizes, too much use and too little time.

I have though had the facility for quite a few years, and have found that certain makes are/were prone to getting HR and so output current limited at the drop of a hat.


ALL my Gens-Ace failed with excessive HR, showing expected voltage, but unable to provide power beyond half a minute on load. Three differing sizes.  All my colleagues Gens-Ace did likewise (two people). Bought differing places, etc.

EFlite batteries likewise.

Zippy not much better.

Just gained from personal experience and from those around me. Not exhaustive, not scientific, just expensive to be wrong!

[ched]

I doubt I would check them very often, maybe once every couple of months. I think I will check the new ones after a few cycles just to make sure they are OK.
As you say batteries are not cheap and, well I certainly, buy a few at a time due to p&p. So I do want to be getting the best value I can.

Looking at all my lipos, I have some Infinity Graphene lipos that are almost 2 years old and one of them has the equal lowest ir of any of my batteries!

I will also test the same batteries on the other 3 channels of the new charger. As it might show differences in readings. It looks like on most of my lipos cell 4 has higher ir than the rest. So I suspect the charger on port 1 at least may be reading incorrectly?

[Bad Raven]

It looks like on most of my lipos cell 4 has higher ir than the rest. So I suspect the charger on port 1 at least may be reading incorrectly?

This is quite likely. Might be HR on the balance port connection, or might be (if consistent) a HR in the internal wiring of the balance connector set. Have had the latter and it was a beast to prove before taking it apart but a relatively easy re-solder where some friday night little chinese person was in a hurry for a curry (or to remove one from their person). 

Had another where it was the balance port connector again, but this one was tracked on PCB and the PCB was thin and had overheated.

[ched]

Very good point. I will test on other ports to see if readings match.

[atomiclama]

I check mine from time to time, it's a good indicator to the state of your packs. If you notice one cell starts to increase in IR then it on it's way out. I just mark up the pack and keep a bit more of an eye on it.

I would expect in a new pack all cells would have similar IR, if not then a duff pack or as stated something wrong with your charger.