kudos
10 kW
I've been trying to find out at what internal resistance a LiPo cell is considered to be past it and should be binned?
Can anyone help ?
Cheers,
Kudos
Can anyone help ?
Cheers,
Kudos
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LiPo Internal Resistance - When to Ditch?
- Thread starter kudos
- Start date
izeman
1 GW
i guess you're talking about rc-lipo which is lico? it's very hard to determine the real ir of a cell w/o high end equipment. but you can get a good guess of the pack's ir if you have a ca-v3 which shows the whole power train's ir. this includes all connectors and wires as well of course. and then you have to devide that by the number of cells.
some of my heavily abused rc-lipos have over 10mohm and i still use them. they sag a lot and can get very hot so i use them with cautions. so tell us how you measure ir and we tell you what values we think are acceptable.
some of my heavily abused rc-lipos have over 10mohm and i still use them. they sag a lot and can get very hot so i use them with cautions. so tell us how you measure ir and we tell you what values we think are acceptable.
as long as they deliver 80% capacity and are not puffed... i keep on rocking...
Heck... i got a 24 cell pack i pricked, squeezed the gas out to de-puff , taped, recompressed and are still going 2 years later. :lol: ... but i treat those like grenades with pins removed.
Heck... i got a 24 cell pack i pricked, squeezed the gas out to de-puff , taped, recompressed and are still going 2 years later. :lol: ... but i treat those like grenades with pins removed.
Ykick
1 GW
Here's is the thread which opened up the potential of IR testing for me:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=48739&hilit=+ir+testing
Although my iCharger does IR I've found it's much easier and often more accurate to setup 1S collection of cells with about 1-2C load for 10-20 seconds and snap a before/after picture of CellLog connected to balance leads, record the Amps and do the math as outlined in video on a cell by cell basis.
In regard to your OP question - 20mOhm is about the point I give up on single RC Lipo cells for eBike service although I continue to find less critical uses for them (lighting, mowers, tools, etc) until they read about 30-50mOhm. Which is usually several years old and time to discharge to 0, solder the leads to dead short and toss them out in the trash/recycle bin.
OT - are we still debating between RC Lipo and lico? I remember Luke suggesting to use RC Lipo and since he's the pro battery engineer that's what I've always gone with.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=48739&hilit=+ir+testing
Although my iCharger does IR I've found it's much easier and often more accurate to setup 1S collection of cells with about 1-2C load for 10-20 seconds and snap a before/after picture of CellLog connected to balance leads, record the Amps and do the math as outlined in video on a cell by cell basis.
In regard to your OP question - 20mOhm is about the point I give up on single RC Lipo cells for eBike service although I continue to find less critical uses for them (lighting, mowers, tools, etc) until they read about 30-50mOhm. Which is usually several years old and time to discharge to 0, solder the leads to dead short and toss them out in the trash/recycle bin.
OT - are we still debating between RC Lipo and lico? I remember Luke suggesting to use RC Lipo and since he's the pro battery engineer that's what I've always gone with.
kudos
10 kW
Ykick said:
Thanks, this was the info I was looking for.
I only have my iChargers to measure internal resistance so that's what I was going to use for a value.
Cheers,
Kudos
docnjoj
1 GW
My Thunder 1220 reads IR at every charge. Seems repeatable and it showed 40 several times with 1 cell. I changed out that cell and the !R dropped to about 5mohms and continues that way. These are A123 but the charger seems accurate and repeatable for IR, so it should be similar for LiPo too. Easy to do since it is automatic.
otherDoc
otherDoc
dogman dan
1 PW
If they aren't puffed, or stinking, they can still be used way past when they suck. I have some almost 5 year old Turnigy and Zippy packs that deliver at best 60% capacity. They will only do this if discharged at about .5c. Internal resistance is crazy high on them. They are slightly swelled, but not what I'd call puffy.
But when I need 80 miles of range, I break em out of storage, charge them up, and suck 12 ah out of a 20 ah pack of them. On a ride like that, I'm trying to run at 300w or less, so I still get something out of them.
Hold my breath charging them every time. Takes forever to fully charge them.
But till I can budget another 500wh or so of new battery, it still works.
But as for when they are no good anymore for a 2-5 c discharge, you don't need a lot of fancy equipment to know when it's time. They will start getting a lot warmer at the end of the ride, and sagging like hell under load. A simple voltmeter will tell you when sag has doubled. Mine went over that line at about 2.2 years. Seemed like overnight, bam, they sucked. Capacity had been about 85%, then suddenly it was more like 60%.
But when I need 80 miles of range, I break em out of storage, charge them up, and suck 12 ah out of a 20 ah pack of them. On a ride like that, I'm trying to run at 300w or less, so I still get something out of them.
Hold my breath charging them every time. Takes forever to fully charge them.
But till I can budget another 500wh or so of new battery, it still works.But as for when they are no good anymore for a 2-5 c discharge, you don't need a lot of fancy equipment to know when it's time. They will start getting a lot warmer at the end of the ride, and sagging like hell under load. A simple voltmeter will tell you when sag has doubled. Mine went over that line at about 2.2 years. Seemed like overnight, bam, they sucked. Capacity had been about 85%, then suddenly it was more like 60%.
izeman
1 GW
the problem with old batteries, even if not puffed, i see is that if they have a high ir they will get very hot when no babied. and you never know when you need that extra power and forget about it maybe. i tend to ditch old cells earlier than maybe needed.
Hillhater
100 TW
Just to be clear, those numbers discussed and suggested are not applicable to other cell types.
18650 LiCo, LMC etc etc generally have much higher IR readings right from day 1.
50 -100 mohm is normal on 18650's.
As the "guide" video suggested, the best thing to do is to test your cells when new to get a "reference" IR figure, then retest at intervals and monitor any changes.
At some stage in the cell life, a significant change will be see to happen. That is the time to bail out !
Also note that there can be big differences in IR measurements depending on...
1) the state of charge
2) discharge test or charge test ( AC test ?)
3) cell temperature
So try to be consistent in your testing method.
18650 LiCo, LMC etc etc generally have much higher IR readings right from day 1.
50 -100 mohm is normal on 18650's.
As the "guide" video suggested, the best thing to do is to test your cells when new to get a "reference" IR figure, then retest at intervals and monitor any changes.
At some stage in the cell life, a significant change will be see to happen. That is the time to bail out !
Also note that there can be big differences in IR measurements depending on...
1) the state of charge
2) discharge test or charge test ( AC test ?)
3) cell temperature
So try to be consistent in your testing method.
dogman dan
1 PW
It's nice to have the budget to bail out when cells just begin to underperform. Certainly you cannot continue to use those cells like normal, if normal was a 3-5c rate.
Nor can you keep using puffy cells, leaky cells, cells with dings or crushed corners all over them.
But I've been amazed, that despite storing another year, I could drag out those tired cells and wring 12 ah from that 20 ah pack. But again, the packs were sorted. I did toss out about 20 ah of them, leaking, puffed, got dropped etc. Only the best remain, and though crazy high resistance, they still dish out 60% if I run them at .5c. Still useful when I need to ride 80 miles. Out here, you can easily have 70 miles to the next town with a plug.
Nor can you keep using puffy cells, leaky cells, cells with dings or crushed corners all over them.
But I've been amazed, that despite storing another year, I could drag out those tired cells and wring 12 ah from that 20 ah pack. But again, the packs were sorted. I did toss out about 20 ah of them, leaking, puffed, got dropped etc. Only the best remain, and though crazy high resistance, they still dish out 60% if I run them at .5c. Still useful when I need to ride 80 miles. Out here, you can easily have 70 miles to the next town with a plug.
cal3thousand
10 MW
My LiPos already have devices lined up for when they are no longer ebike worthy. I've put 150 cycles on my wife's 12S 10Ah pack and the capacity is nearly the same as I have been doing shallow charges for longevity. But when they do go, or when I get my conversions to 18650s completed, some of the HK LiPos will go into my kid's Power Wheels. I will probably make one giant 6s pack with all my old LiPos and let her smash up some longer rides.
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