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Old 04-08-2020
brown4s brown4s is offline
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Default New lipo charging

Hi,

Just wanted to check that I am not doing something wrong here.

Got a new 2s 110c 5500mah 7.6hv shorty lipo that I am charging on an lrp touch comp charger with the following settings:

Charge rate - 5 amps
Cell rate set to 4.2v per cell

Balance charging the lipo takes approx 35 mins, my query is I am getting just 2800mah into the battery when the charger finishes - is this right given the battery capacity is 5500mah ?

Is it because the lipo is new ? Charged it twice so far, both times balance charging and 2800mah seems to be the finishes with.
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Old 04-08-2020
MiCk B.'s Avatar
MiCk B. MiCk B. is offline
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Hi,


Is it exactly 2800mah each time or close to it?
(If it's exactly 2800mah each time, then the timeout safety could be getting triggered.)



Does the pack reach 8.4v on the charger, then the charge rate drop down (0.5amps or similar.) Then the charging stops?



The 5500mah capacity is the total for the pack.


To keep the lipo good you really don't want to take it down to zero capacity.
(Approx 3.3v per cell.)


What are you doing with the pack between charges.
If you are using it for a very similar time / use. Then you will take approximately the same from it.


IE same pack for 3 x 5min qualifying runs (similar runs each time) it should take close to the same each time to fully charge.


MiCk B. :-)
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Old 04-08-2020
brown4s brown4s is offline
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Hi Mick,

Think the last charge was 2880mah when it finished.

The pack does reach 8.4 v and then the charge rate drops from 5 amps right down and then completes shortly after.

I thought with a capacity of 5500mah I would get more into the lipo than I am currently.

In terms of using the lipo I am only practicing in the garden at the moment before I return to racing. After using the lipo tonight just checked the voltage on the lipo afterwards and the voltage was 7.8v.

Last time I raced we were using 3300 scrc’s and sce’s etc so just assumed I would get way more into the lipo than 2880 mah.

Am I assuming wrongly that the lipo pack won’t take more than it currently is ? Or are the electrics that efficient these days that it doesn’t use much ?
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Old 04-08-2020
thrasher321 thrasher321 is offline
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sounds right to me
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Old 05-08-2020
andrewc andrewc is offline
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All sounds good to me. Electrics are amazing these days; you could get 10 mins plus with a 5.5 in a 4WD now...temperature is more the issue than run time.

BUT...you don’t ever want to completely empty a lipo, it actually damages the pack. So limit yourself to 7 mins or similar and check temps, check capacity, depends what you’re running.

The readout on the charger is as you’ve guessed just what you’ve put into it, so basically what you used on the last run. It’s hitting it’s cut off voltage of 8.4 (meaning the pack is full to 5500) so nothing to worry about for me.
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Old 05-08-2020
MiCk B.'s Avatar
MiCk B. MiCk B. is offline
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Hi,


Yes. There is nothing to worry about.


In the days of SCE / SCRC, we needed everything the pack could give.
So you were just happy to last the 5 minute race.


These days brushless and lipo batteries are much more efficient.


So you only put back in what you take out. Regardless of the pack capacity.


So if you take 1000mah from the pack to full charge you need to put back in 1000mah, regardless of the pack capacity.


Enjoy the new world of RC racing. Minimal battery management, being able to race months / years on the same pack. No brushes to replace or comms to true.



MiCk B. :-)
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