Micro Motor Community

Couple battery charging questions


#1

I’ve read a bunch of posts and everyone has conflicting opinions. Some of the more crazy being that you can leave your lipos charged for a couple days and they will be fine (spoken by some guy who was flying RC helicopters for 4+ years!). Obviously, I’m not going to do that, so here are my questions. (Sorry the second question is similar to a question I posted before, but I just wanted to explain my question clearer because I read a post on RCGroups that this could seriously mess up my batteries)

If I am parallel charging 3S lipos (all start within ±0.02 V) and during the charge the cell voltages are sometimes off by almost 0.1 V, but at the ending of the charge all cells are within ± 0.02 V (4.18 V to 4.21 V), will my lipos be okay, or will this drift harm them over time? These are brand new Tattu 3S lipos with less than 10 charge cycles on each.

When I get home from the field, my lipos are at 3.73 V/cell. If I am flying the next day or week, should I put them back up to storage charge (3.8 V/cell) and will this shorten/extend/no effect the lifetime of my lipos? I assume these XT30 connectors take many many cycles to wear out compared to JST PH.

I live about 5 min from the park where I fly, and I fly in the evenings. Is it okay to storage charge my lipos the second I get home? My lipos are slightly warm to the touch (warmer than if I left them overnight), but not hot at all. If I get two successive flights on the weekend, is it okay to charge up right away (5 min cooldown on the drive home)?

Also, is it okay to fly 5 min after I finish charging? The batteries are not even warm (charged at 1C so 2.2A for 5 3S in parallel)

Thanks.


#2

Not at all a battery expert, and i have minimal experience with battery chemistry, but I try not to worry about the specifics too much anymore…

I will charge up no earlier than 15 minutes after the battery has been spent, but I only do that at most once per day, don’t really want to push these batteries too far…

For me personally, life is too short for me to charge back up to 3.8v after bringing it down to 3.7v after a flight… if it lands at 3.7v it stays at 3.7v until the next week hahah hell, if it lands at 3.5v it may even stay at 3.5v until the next week. I used to care, but then i stopped caring once i realize how fast batteries can puff, especially with powerful/monster set ups…

Batteries are stupid expensive in this hobby, and we have to buy a bunch of them which sucks. BUT, at the same time I feel like they don’t truly hold the ratings they say they do half of the time, even name brand batteries so if the companies aren’t taking it seriously, why should I?

What I will absolutely suggest though, is regardless to how crappy/good you treat your batteries, to always monitor the charging process!!! This can prevent a tragedy, or a house fire! You don’t have to watch it like a hawk, but just stay in the same room, and try to be nearby at all times during the charging process in case something happens you can quickly react!


#3

From some experience with a lot of batteries… Leaving lipos charged for some period of time can damage them - this did happen for me with some 1S lipos roughly 2 years ago.
Nevertheless I sometimes leave packs “not exactly at storage charge” (aka below 3.8 or full) and they are still fine. Sometimes you just don’t have enough equipment (I have one charger and a lot of batteries to handle) to do things “by the book”.

Please keep in mind: The major issue with storing lipos fully charged is not only the possible damage to your lipo but safety. A fully charged lipo is waaay more dangerous than a lipo at storage charge.

I totally agree with @quadlifepro on the importance of NEVER charging lipos unattended - be prepared, bad things happened. Additionally it might be wise to store your lipos safely - we have some more interesting threads:



Let me point out another danger which is not mentioned often - damaged wires on lipos:
I’ve been flying FPV quads now for some time and I had at least 3 lipos with slightly damaged wiring (not visible without opening the “shielding” on the lipo) due to some minor incidents. Damages like these might cause shorts => fire hazard.


#4

Yup. Never leave the room, charging and storage in a ammo case, and have a chemical fire extinguisher nearby just in case.


#5

It is worth noting that standard ABC fire extinguishers won’t put out a lipo. Best bet is a bucket of dry sand.


#6

@Bobnova is right. You want AVD (aqueous vermiculite dispersion) type retardant for lithium and magnesium fires, I think that is whats in the extinguishers for lithium bats flammable metals. I don’t think they are cheap.

Bucket of sand is lots cheaper haha. So is charging safe outside on concrete so if a battery vents (or as the manufacturers like to call it the cell undergoes rapid disassembly haha) you cant just let it finish and be safe to dispose of.