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Old 09-09-2017, 06:26 PM   #1
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Default Discharging and Storage

I have some batteries that i charged and never got around to running. If i put my charger to put them at storage will it discharge them to where they need to be, or do i need to do that with the discharge setting. And what is a safe discharge rate or does that not matter?
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Old 09-09-2017, 07:02 PM   #2
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I discharge mine anywhere from 20-30 amps on storage mode, which is set up for 3.8v/cell on my charger.
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Old 09-10-2017, 02:47 AM   #3
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On a good charger, using storage mode will measure the actual voltage and then either start to charge or discharge to get to the set storage voltage.

And discharge rate doesn't matter - most chargers are limited to 5-10A while some go up to 40A (with external resistor banks and such). Remember, that the rating of most modified class ESCs is usually 120-160A continuous, and you'll see, that even those 40A discharge is nothing to worry about, compared to what our cars can pull.
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Old 09-10-2017, 07:25 PM   #4
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And just because a charger specs a certain amperage for discharging, you will have to factor in the wattage. A fully charged LiPo pack and 5~10 watts of discharging power...you're in for a long wait to bring a pack down to storage voltage.
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Old 09-12-2017, 09:22 AM   #5
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be sure to use storage mode and not discharge mode depending on your charger brand. discharge mode will drain the battery completely for disposal and will damage the pack. storage mode will bring them to storage voltage and stop there.
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Old 09-12-2017, 11:00 AM   #6
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Originally Posted by Optima85 View Post
be sure to use storage mode and not discharge mode depending on your charger brand. discharge mode will drain the battery completely for disposal and will damage the pack. storage mode will bring them to storage voltage and stop there.
Errr... nope. Not quite. Usually it only discharges the pack to some set value (either factory set 3.0V / cell or a bit above, or fully user adjustable), which will not destroy the pack. Most of the time, this function is not really needed however, unless you want to cycle your pack, e.g for those 40A discharge/charge cycles some stock class racers do right before the race, to heat up the pack and minimize IR).
If any charger had that function work in the way you said, I would put that charger into the trash can immediately.
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Old 09-12-2017, 11:36 AM   #7
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Quote:
Originally Posted by DirkW View Post
On a good charger, using storage mode will measure the actual voltage and then either start to charge or discharge to get to the set storage voltage.

And discharge rate doesn't matter - most chargers are limited to 5-10A while some go up to 40A (with external resistor banks and such). Remember, that the rating of most modified class ESCs is usually 120-160A continuous, and you'll see, that even those 40A discharge is nothing to worry about, compared to what our cars can pull.
You're certainly right that a 40amp charge or discharge rate on a charger isn't an issue. BUT there's no way our ESC's, motors, connectors, wires, can pull 120-160 CONTINUOUS amps. I don't care what they rate esc's at, if you put a 140 amp continuous load on your system you will have hot wires and melted solder joints. Along with a puffed lipo, actually you won't have a puffed lipo, The internal solder joints will melt first.
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Old 09-12-2017, 01:15 PM   #8
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Quote:
Originally Posted by racer1812 View Post
You're certainly right that a 40amp charge or discharge rate on a charger isn't an issue. BUT there's no way our ESC's, motors, connectors, wires, can pull 120-160 CONTINUOUS amps. I don't care what they rate esc's at, if you put a 140 amp continuous load on your system you will have hot wires and melted solder joints. Along with a puffed lipo, actually you won't have a puffed lipo, The internal solder joints will melt first.
I never wanted to give the impression that these 120A or 160A numbers are entirely realistic, but even only 50% of these, is so much more than most chargers can discharge with (certainly if only internally), just so the OP just shouldn't need to worry about that at all.
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Old 09-12-2017, 03:48 PM   #9
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Quote:
Originally Posted by DirkW View Post
Errr... nope. Not quite. Usually it only discharges the pack to some set value (either factory set 3.0V / cell or a bit above, or fully user adjustable), which will not destroy the pack. Most of the time, this function is not really needed however, unless you want to cycle your pack, e.g for those 40A discharge/charge cycles some stock class racers do right before the race, to heat up the pack and minimize IR).
If any charger had that function work in the way you said, I would put that charger into the trash can immediately.
most skyrc, hitec, and any of the clones have the discharge function. they are all pretty popular. if 3.0 is the default, it is close the danger zone. and if the user unknowingly customizes the value the results could be worse. so for all you new guys out there stick with "lipo storage mode" and you'll be fine. read up on discharge mode later.
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Old 09-13-2017, 11:41 AM   #10
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Yes, 3.0V is a little too close to the limit to my liking as well, but that's what's considered the "empty" point of a lipo cell. Of course people should adjust this value only to a higher, never to a lower setting on their chargers. But honestly, people who don't know the basics should not play around with custom settings at all, should they?

And is the discharge-only mode (i.e. not being used internally as a part of the storage mode) function really useful? IMHO not really - unless for whatever reason you want to deep(ish) cycle your battery - for which there is rarely a reason, other than maybe trying to squeeze the last bit of punch out of the packs in stock racing (which I still doubt is useful enough for the risk taken for >90% of drivers out there).

So, discharging does not per se damage or destroy lipo cells, unless done below a certain voltage, 3.0V being the absolute minimum. For a longer battery life, one may want to not go below... let's say ~3.3V (lots of different opinions around where exactly to stop).
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Old 09-14-2017, 12:16 PM   #11
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Quote:
Originally Posted by Dessel View Post
I have some batteries that i charged and never got around to running. If i put my charger to put them at storage will it discharge them to where they need to be, or do i need to do that with the discharge setting. And what is a safe discharge rate or does that not matter?
What charger are you using? Maybe if you told us that we could tell you explicitly
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Old 11-08-2017, 06:15 PM   #12
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I always put my batteries on and select storage mode. If there isn't enough it will charge if there is to much it will discharge. Just don't leave your battery attached to the charger. This can drain your battery and ruin it.
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I have some batteries that i charged and never got around to running. If i put my charger to put them at storage will it discharge them to where they need to be, or do i need to do that with the discharge setting. And what is a safe discharge rate or does that not matter?
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Old 11-14-2017, 10:50 AM   #13
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Most chargers with a storge mode will automatically charge or discharge depending on the voltage the pack is at. And either charge or discharge to the appropriate voltage and end.
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Old 11-16-2017, 05:49 AM   #14
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Didn't know there were these many regulations before... just plug and charged...
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Old 11-16-2017, 08:55 AM   #15
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In the flying world, we typically charge and discharge (including storage mode) at 1C. Looking at the test report for the batteries I just purchased for my Losi 3XL-E, Venom only did a 2C discharge on their packs for 0.1hr. My extrapolation is that they don't recommend anything beyond 2C for discharge rate, but I didn't find any literature from them that confirms that.

A good charger will have a discharge function that will not allow for discharge below 3.0V, and many have the ability for you to set the value (e.g. 3.3V). Honestly though, you should just use the Storage mode which has the ability to both charge and discharge to achieve the recommended 3.8V/cell.

My thoughts on this are that you should never force discharge (e.g. on a charger) a battery at more than a 1C rating, and I personally never charge a battery at more than 1C. Some battery manufacturers specify higher charge rates, but I ignore them - It's not worth the risk.

Most people charge their batteries in their home, which is a huge risk, though the likelihood of a problem if all steps are followed correctly is low. Flite Test recently did a video on LiPo explosions related to a battery box they were given to test..it's pretty eye opening.
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