Draining LOTS of batteries completely - Using large joule thief for useful enegy?

Thread Starter


Joined Oct 10, 2014
So I'm trying to figure out a way to handle a very large number of lithium or NiCd, NiMH daily (500-5000+ daily) where they need to be completely drained of energy so they don't pose a fire risk.

I'd like to be able to just connect to the battery pack that is 6v up to 60v but some of these packs read zero v due to a broken connection or a bad cell, so many cells are still fully (or nearly) fully charged but the pack can't be drained due to internal issues. So the only thing I can think of is for breaking the packs up and handling the batteries individually. It is possible to separate them by their type/size/voltage (3.6v Li-ion, 3.3v Li-ion, 1.2v NiCd or NiMH, 6 -12v Lead acid's, etc)

I was trying to think of the best way to manage the power from these cells and IDK if it would be worth it to try to capture it into a system which makes it usable or just dump it through a resistive load like a water heater, but IDK how to manage the the wide swing of V that would happen and potential of a massive amount of amperage available when new cells are placed in the "device"/drainer.

I'm thinking that I could make use of large amounts of hot water or even hot air (like a clothes dryer, heat guns - with the only limitation being not to exceed upper limit temps) - hot water is needed for washing some things and then hot air (and fans) for drying the materials.

I was thinking of using something like a 120v/240v resistance coil/heater and then running batteries in series (say 100 1.2v for 120v). The coil would reach full heat (as long as amperage is met, IDK what happens if it can't produce enough, maybe just limit resistor to utilize 1-2A) and then drop in heat as the cells loose charge but if one drops to zero, will it break the circuit or increase resistance creating a fire hazard?

IDK if this is the best method for draining the batteries, if anyone has any better ideas I'm open to it and would like to hear if my ideas of using resistive load to drain is adequate.

I originally thought the Joule thief might be interesting if I wanted to use the batteries to do something that needs a more constant V, but looking at the big picture, finding the most cost effective solution is probably the most important issue and like I said, I would need hot water & a method of drying materials, so maybe the resistive load is best.


Joined Jul 1, 2017
All batteries self-discharge over time. Many of the older technologies don't last more than a week without being topped off. Additionally, some battery technologies do not tolerate being fully discharged (LiPo). You will damage them if you do so. (Granted most Lithium technology batteries have a PCM that prevents this) I digress, without regular maintenance and a minimum level of charge your batteries will be useless after a short time. Hope that makes sense.

As for your ideas for discharging the batteries, yes, a resistive load could be one way to do it. Alternatively, you could also configure a constant current source to sink the current at a constant rate (instead of proportionally like a resistive load)

Thread Starter


Joined Oct 10, 2014
All of the batteries that are in bad condition are the ones that are going to be drained completely as that is what the recyclers require now or they need to be individually "capped" or sealed on both + and - ends, which is a bigger PITA I would think.

If I find cells that are still in good shape like 3.6v Li-ion's that are at the lowest 3v, I'll probably put check them out and see if they are still in useable condition. I'll probably do this with the NiCd and the NiMH as well (don't know what the lowest V is for these before they are too low to be recovered, or too damaged to be salvaged).

The bad batteries are going to be separated by type and delivered to a recycler and the good batteries I'll verify with a charging circuit and see how well they do. I think they make devices that test the health of batteries, but IDK much about them. The good batteries would be sold in bulk on Ebay for a good price as there is no reason to recycle them if they are still in good health.

As for the Lead Acids, IDK what to do with them, I may just scrap them all unless some are still at full voltage and then I would have in-house use for them. The rest would be shipped off for recycling.

When I stated 500-5,000 per day, that is a week's accumulation that has to be processed over a weekend, so we aren't getting that many every day at least in the beginning.

I'd ideally like to do the processing of the NiMH and Lithium batteries and extract the good metals as I have a good background in chemistry. I need to look into this process but it seems that the industrial route is basically putting them in a furnace (in something like a large cast iron cauldron) and melting out the different metals, oxides, etc and them some others grind them all up and then seperate them in a number of other fashions.