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Old Sep 30, 2012, 11:20 AM
DudeInMyrtleBch is offline
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Question

Just got a new Gens Ace 6s 5300mah 60c pack... High internal resistance?


I just received a new 6s 5300mah 60c pack from hobbypartz.com. I put it on my icharger to read the internal resistance, and got the following readings per cell (in mohms)

5 3 9
5 4 2

This is before the initial charge. It's sitting at storage voltage as of right now - and all the cells are exactly 3.84 volts.

According to everything I've read, these IR numbers are quite high. The application that I'm using this battery for is going to really, really stress it.
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Old Sep 30, 2012, 11:28 AM
mrforsyth is offline
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At what temperature was the pack when you measured it? What specific model iCharger do you have?

Has the pack been lightly cycled a few times? Internal resistance improves after a few cycles.

If the pack was over 70F and it has been cycled a few times, then yes, it's likely a suspect pack, especially if you have used your iCharger to test other packs and they measured much lower.

BTW, what specific brand and model is the lipoly? This would be helpful to others who are in the market. That kind of poor performance and variability puts it on the 'avoid' list. (edit: Nevermind on this question. I see that it's in the thread title)

Mark
RCG Plus Member
Last edited by mrforsyth; Sep 30, 2012 at 11:41 AM. Reason: Need coffee...
Old Sep 30, 2012, 11:29 AM
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I have four of the Gens Ace 5300 30C 5s. As read on a PL8 at 68F the cell IR reads about 2 mohm. They may have been a little higher when new.

I'd try one charge/discharge cycle, if you don't get substantial improvement I'd return them
Old Sep 30, 2012, 11:32 AM
papabatman is offline
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Shut up and fly
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question so does his reading make it a 11 true c rated pack
Old Sep 30, 2012, 03:15 PM
DudeInMyrtleBch is offline
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I literally pulled it out of the box, installed an EC5, and plugged it into my icharger - a 206b.

I did notice that I get mostly different readings - within 1mohm - every time I test it. For example, the cell with the ir of 9 will read 8 occasionally, etc...


And, I didn't charge it at all, I just tested the IR.

I'll hook up some of my other packs when I get home, and let you know what they say. I expected to see a pack IR of 8-12. Not 28-30, lol.

I keep my house at 71, so the pack was somewhere close to that.

EDIT: I'm also going to check the firmware version on my icharger... might be old... stranger things have happened..
Last edited by DudeInMyrtleBch; Sep 30, 2012 at 04:00 PM.
Old Sep 30, 2012, 05:40 PM
785boats is offline
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I've always thought that the most accurate reading of IR is when the pack is fully charged.
Those numbers will drop when the measurements are taken when it is charged.
And as stated by mrforsyth the numbers should drop after a few cycles.
Old Sep 30, 2012, 06:38 PM
DudeInMyrtleBch is offline
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I just got home. I've plugged the GA lipo in and am doing an initial charge at 1c. I took another measurement, and got different results - again.

The battery temp was 73 degrees.

The IR from the balance plug read
5 3 7
5 4 2

So, a total pack IR of 26 mohms
If I unplug the balance plug, and do a pack IR measurement with just the EC5 plugged in, I get between 35-38 mohms.

FWIW, the icharger is running the latest firmware.
Old Sep 30, 2012, 07:01 PM
Wayne Giles is offline
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Quote:
Originally Posted by DudeInMyrtleBch View Post
I just got home. I've plugged the GA lipo in and am doing an initial charge at 1c. I took another measurement, and got different results - again.

The battery temp was 73 degrees.

The IR from the balance plug read
5 3 7
5 4 2

So, a total pack IR of 26 mohms
If I unplug the balance plug, and do a pack IR measurement with just the EC5 plugged in, I get between 35-38 mohms.


FWIW, the icharger is running the latest firmware.
The difference between the 26 and 35 milliohms is the addition of the connector and leads. It is surprising how much these will add as they Palso include the intercell connections in the pack.

The i charger only has a resolution of 1 milliohm which limits its value in measuring large cells, ie cells with low IR values of which 1 is a significant %.

Assuming the instrument is perfectly accurate, then a reading of 3 milliohms only tells you that it is between 2.5 and 3.5 at best. Include a small reading error and this expands to between 2 and 4 milliohms.

Wayne
Old Sep 30, 2012, 07:56 PM
DudeInMyrtleBch is offline
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Ok, So the charge is complete. It now reads:

2 1 4
3 1 0

It gets the same readings fairly consistently.

I measured several other batteries I had handy:

2x Turnigy 4s hard case 5000mah 20c:

Battery 1 - 10 cycles on it: 2 0 1 0
Battery 2 - 12 cycles on it : 1 1 0 1

Turnigy 5s 5000mah 30c - Countless cycles on it - several dozen at least:

2.2 1 0 3


The only question that I have now is -- is this new battery going to get better after several cycles? Anyone have an opinion?

This just wasn't the performance I was expecting out of a >$100 pack. Maybe I should have snagged a 6s 40c Turnigy...
Old Sep 30, 2012, 09:10 PM
TheWoodCrafter is offline
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It should get better after several cycles.
And you have seen what one cycle did.

You changed the plug so you are stuck with the battery now.

A good way to handle new packs is to measure the voltage, cycle several times with an adapter instead of cutting the original plug, measure the IR and run a load test.

All this before you modify the pack so if things look bad you can return it.
Old Sep 30, 2012, 10:22 PM
DudeInMyrtleBch is offline
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I didn't change the plug -- it didn't come with one.


Quote:
Originally Posted by TheWoodCrafter View Post
It should get better after several cycles.
And you have seen what one cycle did.

You changed the plug so you are stuck with the battery now.

A good way to handle new packs is to measure the voltage, cycle several times with an adapter instead of cutting the original plug, measure the IR and run a load test.

All this before you modify the pack so if things look bad you can return it.
Old Oct 01, 2012, 09:41 AM
ror1 is offline
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"This just wasn't the performance I was expecting out of a >$100 pack. Maybe I should have snagged a 6s 40c Turnigy... "
no LiPo is worth that...buy from HK only..
The most expensive 3S2200 ($44) I bought is the worst battery I have because it has blown up like a ballon after 1 year. It was bought state side...never again...total ripoff...and they will not replace without returning it...returning will cost the price of several HK battery..
I have had several things refunded at HK and all I had to do was send them pictures..
Old Oct 01, 2012, 09:54 AM
hoppy is offline
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Quote:
Originally Posted by DudeInMyrtleBch View Post
Ok, So the charge is complete. It now reads:

2 1 4
3 1 0

It gets the same readings fairly consistently.

I measured several other batteries I had handy:

2x Turnigy 4s hard case 5000mah 20c:

Battery 1 - 10 cycles on it: 2 0 1 0
Battery 2 - 12 cycles on it : 1 1 0 1

Turnigy 5s 5000mah 30c - Countless cycles on it - several dozen at least:

2.2 1 0 3


The only question that I have now is -- is this new battery going to get better after several cycles? Anyone have an opinion?

This just wasn't the performance I was expecting out of a >$100 pack. Maybe I should have snagged a 6s 40c Turnigy...
My suggestion:
email the vendor explaining the problem. Request permission to try the pack in the application you are going to use it in and see how it works with the understanding that if it doesn't perform he will replace it.
Old Oct 01, 2012, 01:53 PM
Remote_Pilot is online now
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Thats why I dont buy Gens anymore or rarely from Hobby Partz etc.
Old Oct 01, 2012, 03:20 PM
Harry D is offline
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I have a Gens Ace 3S 5500 which I bought in the summer of 2011. Not sure if that has the same cells as yours, but the info below may help.

At the time, I did some fairly careful testing to see (just out of interest) the effects on IR of things like initial cycling, state of charge, etc.

My pack showed cell IRs around 1.8 milliohms at 19C (Wayne's meter), giving a FOM of about 1.2.

I'm only using this pack as a source battery for a portable micro lipo charger, so I don't really care about the actual C value (and which is why it has such a small connector!). But if I did need a higher C, I would rate that pack as pretty good.

If anybody's interested, I've attached the results sheet I made up at the time and would be interested to hear any comments on what I found.

Basically, I didn't find that IR dropped after a couple of initial cycles, contrary to conventional wisdom (maybe it's pack-specific).

Also, I did find a fairly consistent (but not huge - about 25%) variation of measured IR with state of charge. Lower indicated IR at full charge than when discharged (not unexpected, really). Again, opposite to what I've read elsewhere.

I believe my methodology and equipment was reasonably good, but feel free to pick it apart.

(If I've gone too far off topic, please say so and I'll edit accordingly).


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