I got sick of charging LiPo batteries up for boats and planes then the weather packs up just as you have finished. You then have to storage charge your batteries unless you are using them fairly soon, which can take forever doing it with your charger (especially with bigger batteries). I decided that rather than have to drag out a plane to run the batteries down quickly, I would make a simple discharger with multiple discharge rates. I'd had some car bulbs lying around for years so decided to use those, plus a marine riding light I had spare for the loads. I now have 10w, 5w. 22w and 52w loads to suit different sized batteries,- larger loads for larger batteries, smaller loads for smaller, (depends on your battery's output capability also, i.e 20c, 40c etc). You could make a switched array of bulbs if you want to be fancy so you can adjust the Amps/load for each battery.

I put the power analyser /balancer in between the battery and load and set it to battery check/balance mode (plug battery balance lead in for this method) so you can watch the individual cell voltage (you have to be there for this), or plug a voltage alarm into the battery balance lead (as in photo) and set it to 3.6v which reminds you to check it early.

As it is with 12v bulbs, it will work for 2-3s batteries, for larger batteries you could try 24v truck bulbs or make resistance wire loads etc. There are dischargers available, but this is an easy method, and bulbs are cheap. You can just solder wires to the terminals (power) and body (earth). Brake / tail lights are handy as you have 2 wattages to choose from, ( I used the XT60 plugs (both positives to bulb terminals, i.e 1 to each) and linked the 2 negative plug terminals and soldered that negative wire to the bulb body. The large load Halogen bulb is using the low wattage (55w) filament terminal, and the earth terminal (just an old bulb with a blown high beam).


DC watts to amps calculation
The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V):

I(A) = P(W) / V(V) ie 10W / 8.2v (2s) =1.2A
-----------------------------------------------------
Hi, this is not how LiPol batteries are treated.
I recommend using a cheap digital charger, which has a built-in balancer and the ability to discharge batteries. At the same time, it has a storage program in its menu, which will take care of charging the cells to about 60% after discharging.(charger from TURNIGY) This way, the articles can be saved for up to half a year. And they will not be damaged. I myself have 4000 mA twin cells, which are 5 years old and are still not inflated and have full capacity. Under no circumstances should LiPol batteries be stored in a discharged state - they will be damaged.
Zdenek Czech Republic - Central Europe👎👍

Don't know where my post has gone,?? but there is nothing wrong with discharging a LiPo like this. It is exactly the same as running a motor to discharge a battery you have charged but are not using, and want to discharge back to storage level. You will note that there is a cell monitor as well as a voltage alarm to show when the battery is nearing storage level. Then you discharge the battery using the discharge/balance/amp meter (you will need to buy one of these to do this) the rest of the way,- or you can put it on the balance charger to storage level I have been doing this for more than 10 years, have 15 planes and 6 boats,- all LiPo powered. I also use the same LiPos in camping lanterns. Never had a problem.

JB

Hello, yes, this is one of the options, but it is unnecessarily lengthy and requires constant control to avoid damaging the cells. What I wrote is just an easier way to treat the battery. By no means did I want to deny your procedure.
Zdeněk wishes much success in modeling.

Hi, Zdenek , This is actually a quicker way of safely discharging a full battery than using a the balance discharger in your charger. It is just doing what your motor is doing without having to have your TX on and adding wear and tear to your motor. Most common chargers have a low discharge rate (maybe only 500Ma) due to them being a compact size, and not having fans big enough to dissipate the heat. Some expensive ones may discharge at 2 or more Amps for larger high capacity batteries, ( 10s etc). Common chargers will take hours to discharge a full battery (I use 5s 40c batteries in my planes and my good Sky RC charger will take all day to discharge a full one to storage level (and that's not even the minimum voltage. )

My method is just to simulate a motor running a battery down normally, and before I made this up I would run the motor in the plane (or boat) to bring the battery down to near the storage level, then finish it on my Watt meter, which can also cell check, and balance/discharge. Handy tool to have for electrics but hard to find now. HK used to sell them years ago and I bought 2 (one for home and one for the flying field/pond) I just discharged my 3s boat battery with my lamp discharger and the battery monitor sounded at 3.85v and the cells were even (3.85-3.84-.3.84 (that battery is from May 2011) Only took around an hour.

There are a number of ways to reduce voltage in batteries, but as long as you balance them afterwards they should be fine. You obviously prefer to use your charger, and maybe you are using only 2s or 3s batteries which don't take too long to balance, but with larger batteries it takes far too long, and as you should never leave them unattended it can mean not going anywhere for a whole day☹️
Here is a link to similar versions of my bulb discharger (there are many similar discharger types)

https://oscarliang.com/discharge-lipo-batteries/

Regards, JB

https://www.bighobby.cz/Nabijec-Turnigy-Accucel-6-LiHV-80W-10A-d1801.htm#