LiPo battery charge level for storage

J

jim4b

Member
So at the end of each summer drone flying season what is the best suggested battery charge level for safe storage. I saw some where that you should only charge your lithium polymer drone batteries to about the 50% level to avoid any possible expanding damage. Is that correct. I had fully charged my Eachine EX4 2 batteries at the end of last year's season, and they both expanded a lot and pushed off the case cover. So much swelling then made those batteries dangerous and not usable. So I had to dispose of them safely at a recycle place. Okay thanks.
 
Yup I've seen 3.7-3.85 as the range of good for storage long term. So long as not at 4.2V they will do better but if can get them close to 50% even safer, you don't want the charge per cell to ever dip below 3.0V and on the shelf not connected to anything they typically won't drain really aside from chemical wear but when stored charged all the lithium has a high potential for chemical reactions. I believe the puffing is a result of gas build up in the electrolyte gel that allows ion flow but blocks the electrons so they have to take the long way around to balance things out (at least my layman understanding of it)... The exact chemicals that breakdown and what they become is above my pay grade :).
 
Okay I see, and is there a good LiPo battery tester to be able to check the voltage? Or can I use a standard digital multimeter? My MJX Bugs 4 drone has batteries with 8 connector contacts, and in the charger bottom there are only 4 contacts. So which ones do I use to test them? The charger does have 4 charge level indicator lights.
 
Yup a regular multimeter is typically gonna be better calibrated and give more accurate readings than cheap lipo testers but those do exist. You can just use some wire attached to your probes to stick into the balance lead or test the average from the main battery leads and get a pretty good approximation just dividing by number of cells.

Say 4S battery at 16V is 16/4 4V per cell, again assuming the cells are all pretty even in terms of charge which they should be if using a balance or hobby lipo charger.


Things like the product above have a loud beeper too so can keep them on the balance lead for bigger stuff and get an early warning if your cells are getting low while using and rc thing (the led display will sip some power so not good to leave on there on the shelf but fine for fast testing)
 
You really need to invest in a decent charger, like the SkyRC B6. There are other good ones (although watch out for counterfeit clones). They have a "Storage" setting and it will charge your batteries to the correct voltage.
 
The type of connection on those batteries is a row of 8 pins built in so that it is not easy to connect to a tester. It is only designed to snap into either the drone or charger mating connector. So I saw a you tube video which said touch the digital multi meter plus and minus probe leads to the first and last pins on the battery for the full total voltage check. I did that with a standard analog battery tester and it does work with correct polarity.
 
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The batteries that I’m most concerned about are four 7.4V, and of the module type. No wires or plugs as you know. Will there be a way to manage these with a charger/discharger like the one mentioned in a previous post?
 
If you can share a link to specific battery type or images that helps a lot. In general you can just fully charge the batteries do a flight and time it, fully charge again, fly half the recorded time and stop and you should be pretty close to storage voltage level. You can in general just replace the connectors on quads (or any device) so long as you know the voltage that was originally going in and use at least as good or better connectors (like xt-60, basically bullet connectors in nylon casing, rated for 60A current, or xt-30 for small/low power things). I usually go with one of the xt type connectors because it's easy to find batteries off the shelf in all sorts of voltage and capacity (mah) with those connector types.

So long as working on parts that aren't plugged into a power source (battery) you can safely remove or work on things. Place to take more caution and watch some vids is regarding replacing connectors on batteries themselves (wouldn't recommend to anyone not already very adept at soldering and with decent understanding of electricity).
 
Since you mentioned 7.4V pretty safe to assume they are 2S lipo batteries with bare minimum voltage of 6V and max charged voltage of 8.4V (avg is 7.4, each cell goes from 3.0V to 4.2V discharged to charged). 3V per cell here is absolutely a bare minimum you really only want to ever discharge down to around 3.6V per cell since being under 3.0V can cause severe damage to the cells. Generally cells packaged as a module like that will at least include low voltage cutoff circuitry to protect the cells but make it more difficult to use with non proprietary chargers
 
wafflejock said:
Since you mentioned 7.4V pretty safe to assume they are 2S lipo batteries with bare minimum voltage of 6V and max charged voltage of 8.4V (avg is 7.4, each cell goes from 3.0V to 4.2V discharged to charged). 3V per cell here is absolutely a bare minimum you really only want to ever discharge down to around 3.6V per cell since being under 3.0V can cause severe damage to the cells. Generally cells packaged as a module like that will at least include low voltage cutoff circuitry to protect the cells but make it more difficult to use with non proprietary chargers
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I realized just after posting my question how little information I’d given. Theses batteries are for a Holy Stone 120D quad. Maybe I should’ve started a new post? Don’t want to hi-jack this discussion. I can solder, but would I find 7.4V batteries of the type you spoke of that weigh the same or less than these module type? And fit nicely? Thanks for the good info.
 
I think just keeping in the shade/in a bag is good enough really the batteries get pretty hot when delivering power. The problem with a fridge or freezer is if the cells are below the dew point temperature then condensation of water occurs when you take them out and the condensation on the connectors causes them to oxidize/rust and I imagine can't be good for the chemistry in the cell either. Really they deliver peak power around room temperature anyhow so you don't want them excessively cold (the lithium ions need to flow through the electrolyte, cold slows things down in this case).
 
mrlewp87 said:
I realized just after posting my question how little information I’d given. Theses batteries are for a Holy Stone 120D quad. Maybe I should’ve started a new post? Don’t want to hi-jack this discussion. I can solder, but would I find 7.4V batteries of the type you spoke of that weigh the same or less than these module type? And fit nicely? Thanks for the good info.
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No prob glad that made sense :). And yup the issue is usually trying to find cells that are the right dimensions to match what you've got already but there are all sorts of capacities and sizes available ( I typically fly a 5" prop quad with 4S 1300mAh or 1550mAh batteries, get between 5-10min flight time). If the battery is labeled with mAh (capacity) then can usually search for ones with same capacity and check dimensions to find one that matches or will fit. Typically the modules are just a nice plastic housing around the bare cells (maybe with extra circuitry to protect cells as mentioned already), so they will usually be bigger for the same capacity compared with "raw cells".
 
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