Help! How Much IR Is TOO MUCH?

[Liam B]

I have a 6600mah 4S 35c ReadyMadeRC LiPo that is approaching the ripe old age of 8 years old (I bought it at FliteFest 2016!). I understand that the safe IR for a 1500mah LiPo is under 20ohms per cell. So my question is... how does this scale up? I can't find a calculator or manual equation to satisfy my question. This old guy is nearing 13ohms per cell and I really like this pack! It's been through a lot with me! Can I keep it? And how can I calculate this better in the future?

 

[Mr NCT]

I have a 6600mah 4S 35c ReadyMadeRC LiPo that is approaching the ripe old age of 8 years old

That is impressive. What's your secret to such a long life?

 

[LitterBug]

I'd say if the cells have equal resistance, and the battery doesn't sag, keep using it. I have a handful of batteries of similar age. I have also had a bunch of batteries where one cell has gone bad and they became useless sag monsters.

 

[Piotrsko]

In my full size car pack in the ranger: similar internal resistance in a 16 million mah cell, but slightly different chemistry. Pack is at 13 years old. Eventually the resistance gets so high that you will not be putting out the amps to drive the motor. So when the power on times gets too severely short for your uses and the run time in now down to only a couple of minutes, it's time to retire it.

 

[Liam B]

That is impressive. What's your secret to such a long life?

I've mistreated the crap out of this battery. I've left it at full charge before and below 3.2v per cell, so I am no poster child for battery treatment (Actually, not a child at all anymore. Still getting used to that!).

What I think has kept it's life so long is that I've only used it in low-current applications, such as powering my goggles, soldering iron or Ethix LiPo bag heater. Otherwise, this thing would have been dead long ago, I think. And come to think of it, I bought two of them and I only have one. Not sure what happened to the other but I did end up disposing of it.

 

[Liam B]

In my full size car pack in the ranger: similar internal resistance in a 16 million mah cell, but slightly different chemistry. Pack is at 13 years old. Eventually the resistance gets so high that you will not be putting out the amps to drive the motor. So when the power on times gets too severely short for your uses and the run time in now down to only a couple of minutes, it's time to retire it.

Interesting. Never thought about measuring my lead acid car battery before. My alternator just went out too so I was driving on solely the battery for 50 miles or so. I should take a look.

I've actually used this pack to jump a car before too. Though most car systems are 12v, they usually sit around 13.8 and I figured the voltage would drop from a 4S given the crazy amp draw. So far so good lol.

 

[Mr NCT]

I've actually used this pack to jump a car before too

So that's the secret!!

(Actually, not a child at all anymore. Still getting used to that!

Yeah, that never ends. A friend once told me "I always hoped I'd live this long but never thought I'd look like this."

 

[Piotrsko]

Umm the ranger pack is 98s6p and lifepo4 and weighs 440 lbs but its not FLA.