"Over-charge capacity limit"... ???

[high plains drifter]

I'm using a SKYRC iMAX B6 AC v2 charger for my lipos and I recently ran into an issue that I need help with. For what it's worth, the charger has been great... no issues whatsoever.

But I recently bought a Turnigy nano-tech 4.0 4000mAh 2S lipo ( 25-50c discharge). I've only charged it twice but both times at the end of the charge cycle, there was an error-message that read "OVER CHARGE CAPACITY LIMIT". In the iMAX owner's manual it simply states that the message means: "The battery capacity is more than the maximum capacity which the user sets".

When I've charged this battery, I've done so by setting: BALANCE CHARGE/ 2S/ 4000MAH/ START and I'm obviously plugging in the balancing lead, so...

Anybody know what I'm doing wrong? Thanks much for the help.

 

[TheLetterJ]

There's a good chance that your packs can hold more than 4000mah, so you can either start the charge over to "top off", or change the capacity value on the charger. I have a few 5000, 5200, 7200, and 8000mah packs, so I changed the capacity shut off to 8000mah so I didn't have to reset for a full charge. If the individual cell voltage doesn't exceed 4.2, it really shouldn't matter if your capacity shut off is programmed higher than a pack's rating.

 

[gonper]

Battery manufacturers usually gives you the medium average battery capacity sometimes is a bit more sometimes a bit less, but usually it is a bit more because they do not want claims...
So a 4000mAh pack can be easily 4200mAh when new.

The "Over-charge capacity limit" is a safety feature of some chargers.
They keep tracking how much charge you put in the pack and if it goes over what was defined on the charge settings for that pack then they stop the charge, avoiding any issue.
Note that this safety feature only works when the battery is charged from an empty or almost empty state, but is good to have as manny safety features as possible.

So if you have programmed your charger for a 4000mAh battery and it is 4200mAh when the charger have charged 4000mAh it will stop charging and give you that message "Over-charge capacity limit" (so yes your charger is working properly)
I suggest that you program your charger with a little bit higher setting like 4400mAh (a 10% more) in order to avoid that issue and still use the safety feature.

A recommendation on the way you are using your packs:
I notice due your charging issues that you are fully depleting the batteries when you use them. That is not recommendable on Lithium batteries because they suffer more stress by the end of the discharge, so if you want your packs to last longer and keep good power try to stop using them before they are fully empty.
There is a couple of easy ways to do so:
One, is to program higher your low voltage cut-off on your speed controller.
Another one, is to set a time alarm on your transmitter, if you usually can run for lets say 15min. program it at 13min. or so and stop running when it beeps.

 

[2mtech]

I had a couple of Onyx 2S packs that would trip that error every time I charged them on my Hitec charger. Restarting them led to perfectly balanced charges without the error. Never had a problem with those same packs using my Onyx 235 charger.

 

[high plains drifter]

I have only used this pack twice... both times on the same vehicle with "low-voltage detection" enabled on the ESC. I didn't realize that I was running it all the way down but regardless, I'll try setting the mAh a little higher the next time that I charge this pack and I'll plan to keep an eye on my run times and stop running the vehicle before the LVD starts flashing.

I really appreciate these replies. I learn something new from this community every day!

 

[Hydrocarbon92]

The problem is most ESC's "LVC" is too low, especially for low-load apps like many brushed high-turn crawlers. 3.5v is considered 0%, but many ESC's are set even lower like 3.2v. Even at 3.5v you're still putting more wear on the cells than if you stopped at 3.8v. A full cycle (4.2->3.5v) on a lipo vs 2 half cycles (4.2->3.8v) cuts the lifespan in half despite both discharging the same overall wattage.

Best analogy I can offer is a full discharge is like hitting your crawler with a baseball bat & half discharge is like 100 times with a fly swatter.

 

[gonper]

The problem is most ESC's "LVC" is too low, especially for low-load apps like many brushed high-turn crawlers. 3.5v is considered 0%, but many ESC's are set even lower like 3.2v. Even at 3.5v you're still putting more wear on the cells than if you stopped at 3.8v. A full cycle (4.2->3.5v) on a lipo vs 2 half cycles (4.2->3.8v) cuts the lifespan in half despite both discharging the same overall wattage.

You are completely right that values of LVC (3.0 to 3.4V per cell) comes from manny years ago that Lipoly batteries where not so powerful as that ones we use now.
Now the ESCs should have programable values that could go up to 3.8V per cell or so.
My recommendation now is to set it around 3.6-3.8V per cell for fun use in order to have healthy batteries.
On planes/helicopters flying quite aggressively we set up two alarms, one for voltage usually 3.7-3.8V per cell and another one on time if any of them beeps its time to land.

NOTES:
This values do not apply to competition or very high demanding applications.
This values do not apply on very very low demanding applications.

 

[high plains drifter]

Unfortunately this is the Traxxas XL5 ESC so I doubt that I can change the low-voltage detection. At least I don't remember seeing that as an option in the owner's manual. I will however keep an eye on the run-time and maybe set an alarm on my phone to alert me. Fwiw on NiMH the run-time was about 30mins or less. Both times that I've run the new lipo, I got about 40-45 mins of run time.

 

[high plains drifter]

Frustrating update- Went ahead and bumped the charger setting up from 4000 to 4200 mAh. It still read "over-charge cap limit" when it was done charging. Going to up it to 4500 next charge. The frustrating part was when I ran the truck this morning... Less than 20 mins before it was done! So battery seems to have less and less run time with each charge... ugh.

 

[Hydrocarbon92]

Just set it to 5000 (or higher if possible) and be done with it. That charger should never go above 4.2v/cell anyways, unless you re-calibrated it to think 4.3v is actually 4.2v. You should also be able to disconnect & reconnect for a top-off charge if it doesn't get to 4.2v - lipos suffer no ill effects from re-starting a charge or charging halfway thru a discharge cycle.

 

[gonper]

The frustrating part was when I ran the truck this morning... Less than 20 mins before it was done! So battery seems to have less and less run time with each charge... ugh.

Maybe you are running it harder as you learn :lmao:
Unless the battery is very very low quality or damaged it is not noticeable a capacity loose from one charge to next one.

 

[high plains drifter]

IIRC the first run yielded about 40-45 mins of run time. Now ( after only 3 charges on this pack) it's down to about 18-20 mins. I'll keep an eye on what the charger is telling me next time that I charge this pack... And I'll go ahead and set it for 5000mAh. Thank you, guys.