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Old 05-26-2015, 09:25 PM   #1 (permalink)
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Default What causes high IR on last cell?

I read in another thread that some conditions, namely using third party adaptors, will cause a high IR on the first or last cell in a pack. I am curious what causes this phenomenon. My PL8 is reporting about an IR approximately 4 to 6 higher on the last cell. I suspect it is the JST-XH adaptor board (FMA/Revo original that has been shorted and has a golden-colored trace.) However, the common sense in me, without an EE background, wants to think that if the trace is still intact that it would not increase the resistance much. I just want to understand why it only impacts the last cell.

I am also curious about the new adaptors with polyfuses - do these work well to prevent male balance plug shorts?
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Old 05-27-2015, 12:03 AM   #2 (permalink)
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Hi,

The fused boards work great for preventing damage. Here are my notes on the Powerlab8 IR issues.


Last cell has high IR - This is caused by using older firmware or the wrong wiring mode. Verify the Powerlab8 is using at least 3.31 (latest as of today) and the wiring mode is correct for the balance adapter in use.

First Cell has high IR - This is caused by minor differences in resistance (less than an ohm) between the two main leads (not the balance leads). This is commonly seen when there is a fuse on lead but not the other. Additionally, a small about corrosion or carbon build up can give this same result. Many hobby connectors cannot be properly cleaned. Use if a product like Deoxit can help. If you are using an early version of the FMA charge cables that have fuse on only one lead, this could cause cell 1 to read roughly twice the other cells in the pack.

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Old 05-27-2015, 12:27 AM   #3 (permalink)
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As above, most likely the wrong parallel board type is selected.
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Old 05-27-2015, 06:03 AM   #4 (permalink)
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I use the Revo XH balance boards and I get the same problem with cell #1 every single battery, every single charge.

I figured it can't be the battery if it's consistent with every battery I charge.

I don't get why it is though, even given Gregs explanation.
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Old 05-27-2015, 08:23 AM   #5 (permalink)
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Quote:
Originally Posted by PHANTMXR6 View Post
I use the Revo XH balance boards and I get the same problem with cell #1 every single battery, every single charge.

I figured it can't be the battery if it's consistent with every battery I charge.

I don't get why it is though, even given Gregs explanation.
Check the "wiring mode", FMA or XH/EH. It will work on both modes just not give you the correct IR reading if it is in FMA and should be in XH/EH mode.
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Old 05-27-2015, 09:36 AM   #6 (permalink)
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I tried switching it to the other wiring config and it gave me a bad cell count error. Here is a pic of the trace. I'm surprised it works at all.
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Old 05-27-2015, 12:02 PM   #7 (permalink)
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For that board you must use FMA wiring mode.
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Old 05-27-2015, 01:46 PM   #8 (permalink)
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Quote:
Originally Posted by lucidchaos View Post
I tried switching it to the other wiring config and it gave me a bad cell count error. Here is a pic of the trace. I'm surprised it works at all.
If it gives a bad cell count error using FMA wiring mode then the board needs to be replaced or repaired. If it works in FMA wiring mode but you still have high on one cell then the next step is to take a look at your main leads. Both leads should be fused and of equal length. The connectors should be cleaned. I use a Q-tip and Deoxit on the female 4mm connector on the charger.
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Old 05-27-2015, 06:20 PM   #9 (permalink)
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Quote:
Originally Posted by Howard Matos View Post
Check the "wiring mode", FMA or XH/EH. It will work on both modes just not give you the correct IR reading if it is in FMA and should be in XH/EH mode.
Yep, it's always in XH/EH mode as that's all I have.

Greg, you mention fuses on both main leads. Surely this would not be applicabel for a Revo balance board as the whole outputs of the board are fused?
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Old 05-27-2015, 08:20 PM   #10 (permalink)
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Quote:
Originally Posted by PHANTMXR6 View Post
Greg, you mention fuses on both main leads. Surely this would not be applicabel for a Revo balance board as the whole outputs of the board are fused?
I was referring to the main leads not the balance leads. Lucidchaos' board is not fused otherwise there would not be damage. Also his board does not include the main leads like the MPA or a parallel charging board. So in his case, we don't know what he using between the charger's main outputs and the pack.
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Old 05-27-2015, 10:12 PM   #11 (permalink)
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I am not using fused main leads. My mains are in a charging squid configuration. However, I don't believe that is the problem due to these facts:

-My EC5, EC3, and JST charging squids all report high IR on the last cell, regardless of which pack or cell count.
-I used these leads with a powerlab charger in the past with no IR issue.

I am also on the latest firmware.

Here is an example of my main connector. I have similar for EC3 and JST.
http://www.buddyrc.com/parallel-char...le-ec5-x6.html

I also have 2s, 3s, and 6s parallel balance squids, although I have eliminated them for the purpose of diagnosing IR issues.

Edit: I just used contact cleaner on all contacts (bullets male and female, all balance pins) and it did not seem to make a difference. Here is an example of what my IR over time graph looks like. Odd that cell 6 is rising while the others are falling...
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Old 05-28-2015, 10:15 AM   #12 (permalink)
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I'd try a different balance board. For the charger's 4mm female connectors, if you didn't use a Q-tip it might still need some work.
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Old 05-30-2015, 04:35 AM   #13 (permalink)
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When I purchased my PL8 a month or two ago I noticed the 6 cell would always give high resistance I contacted John Grzan and here is what he said see below email

Hi John,

I received the new PL8 you sent me the other week Thanks!!
All is working well except on cell 6 my PL8 is giving me high ohms readings
On all other cells 1-5 I get around 1.5ohms but on cell 6 the reading I get is always 4 – 5ohms
No matter what battery I charge I always get that high reading on cell 6, but on my other PL6 cell 6 reads similar to the other cells around 1.5ohms
The lipos I use are all Revo HV & diamond series some of them are only 2 weeks old
Does my PL8 need to be recalibrated? Do you have any suggestions what I could do?
Cheers
Lee


Lee

PL8 has node only charge function and due to some extra resistors in the charger that gives that function it shows up in the IR of the last cell almost every time as you see

With that added function we can’t get rid of the IR value being high

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Old 06-01-2015, 01:48 AM   #14 (permalink)
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Lee, thanks for the info. My PL8 is still version v2 and it also shows higher IR value on the last cell. It shows the same with all 8 lipos regardless if they are newer or older.

I don't know what "node only charge function" means but if they have a known wrong reading because of the hardware characteristics of the charger, I wonder why they don't fix it through the firmware.

This is an expensive charger and we shouldn't have those kind of problems.
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Old 06-01-2015, 05:08 AM   #15 (permalink)
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I agree Mateyhv
I don't know what "node only charge function" is either my PL8 is only 2-3 month old and you would expect this issue would be resolved if they know about this issue
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Old 06-01-2015, 06:37 AM   #16 (permalink)
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Node only charging means you can charge a pack using only the balance lead, you do not need to connect the main leads. This feature is only available when using FMA wiring mode. Max charge current is limited when using node only charging.
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Old 06-01-2015, 08:11 AM   #17 (permalink)
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Quote:
Originally Posted by Ace Dude View Post
Node only charging means you can charge a pack using only the balance lead, you do not need to connect the main leads. This feature is only available when using FMA wiring mode...
Thanks Ace! However, in order to have IR readings the battery must be connected to both main and ballance connector. At least in my PL8, otherwise there are no IR readings.
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Old 06-01-2015, 08:56 AM   #18 (permalink)
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Quote:
Originally Posted by Mateyhv View Post
Thanks Ace! However, in order to have IR readings the battery must be connected to both main and ballance connector. At least in my PL8, otherwise there are no IR readings.
Quote:
Originally Posted by Mateyhv View Post
I don't know what "node only charge function" means

That's correct. I was just answering the question explaining what node only charging is.
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Old 06-01-2015, 12:13 PM   #19 (permalink)
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Quote:
Originally Posted by Lee2782 View Post
I agree Mateyhv
I don't know what "node only charge function" is either my PL8 is only 2-3 month old and you would expect this issue would be resolved if they know about this issue
It was fixed in firmware version 3.31.

***VERSION 3.31 2-24-12*** Fixed MPA internal resistance reading.

If you are still having issues, its typically one of the following:

1) Incorrect wiring type for the balance connector being used.

2) Damaged, worn, corroded, or generally dirty contacts on the balance connector or the main leads.

3) An imbalance of resistance on either the main leads, or the balance connector. A lot of 3rd party boards and cables may have a fuse or LED on either the positive or negative leads, but not both. This causes issues with the IR readings.

EDIT: Example of PL8 showing the correct IR. The user in that thread did found that it was a due to a BuddyRc parallel board. http://www.rcgroups.com/forums/showp...0&postcount=17
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Last edited by Gregor99; 06-01-2015 at 01:13 PM..
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Old 06-01-2015, 03:43 PM   #20 (permalink)
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What firmware are you guys running? I'm on 3.32.
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