Ohm's Law at Work: Cheap 2s-6s LIPO Discharger / Killer

[@corbymodelboatclub]

That is a very neat way of cooling the resistors and Ohms law is well explained. It might be an idea to mechanically fix the wire to the resistor leads by winding once round and then soldering. I have found in the past that if you generate enough heat/wattage in the resistor the solder can melt and the wire falls off. Most of those resistors have a hole in the lead for this purpose. In the good old days when we made GPO (before BT) panels the inspector would fail the kit if the resistors were not mechanically fixed.

[@RCVideoReviews]

I took some temperature measurements with the Admiral and at 17amps, I was seeing about 250F and that wasn't enough to melt the solder on the lugs. Heat sink was immaterial as it didn't influence the temps on the lugs. That said, half the fun of doing projects like this is to experiment and learn, so definitely make mods and play with it.

[@corbymodelboatclub]

@@RCVideoReviews Cheers for the comment. I think you are doing a great job. I have only used a system like your Admiral when testing a 500 Watt MOSFET amp at max RMS output for a couple of hours. That was a long time ago.

[@TheCabledawg1]

You can do everything you just did without the step down converter. Put just the fans in series. They will run slower with a 2S and faster with a 6S. It is how I have done mine. I use lightbulbs instead of resistors. Also, mine is encased in a dollar store tupperware clear shoebox size container. I have the fans on both sides of the container...1 is pushing air in and the other is pushing air out. I have had it this way for 12 years. I use computer case fans rated for 12V and they do fine with a 6S battery because they only see half the voltage.

[@jdduncan]

Thanks for this! I just built 2 of these to retire my older batteries. I mounted the discharger on a metal ammo box so I can have the battery safe in the box during discharge.

[@RCVideoReviews]

Nice job! They work great.

[@jdduncan]

@@RCVideoReviews I wanted to try using one of the dischargers to discharge down to 3.8v per cell for storage using an Apex RC lipo battery voltage checker and alarm. I set the alarm at 3.8v per cell but when I hook it up it to a 6C battery that shows a 95% charge it starts dropping super fast and the alarm will go off within 45 seconds. With the load connected all the cells are around 3.8v. When I remove the load the cells jump back up to 3.9v. How do you make this setup work to discharge for storage?

[@Weiun]

👏👏👏 I will be building one, thank you.

[@RCVideoReviews]

Have fun!

[@ebandcamp]

Thanks gonna build one !

[@fd2237]

Very handy device John, thank you for sharing! Fotios

[@RCVideoReviews]

Sure thing. Thanks for watching.

[@deanedeane4318]

Simple is good!!! Nice project 😉🤗😎

[@RCVideoReviews]

Yeah, this was fun to do.

[@vmddew]

Nice Killer! Thx.

[@RCVideoReviews]

You’re welcome.

[@heydonray]

Very nice. Thanks.

[@JustKeepLivingFPV]

Awesome, ive been needing to beuild myself a discharging unit so i dont have to over work my charger. Im gonna try and find a lightbulb free at home stuff type of one.

[@RCVideoReviews]

Good point. No reason to beat on a charger when it's so easy to make one of these.

[@ricktaylor51]

The lipo checker emits a high pitch sound, which I am unable to hear. However, to completely discharge a lipo, definitely a plus. Caution, don't leave unattended. Thank you for all your great videos.

[@RCVideoReviews]

You're welcome. FYI these meters usually have a flashing LED when the threshold voltage is reached if that helps.

[@jlarson42]

Excellent tutorial for a useful tool. For discharging to storage voltage, I use the ISDT BG-8S tester to charge my usb devices. Phones, tablets, ear buds.... But I don't have a good lipo killer, thanks for sharing. 👍😎

[@RCVideoReviews]

You're welcome. Have fun with it.

[@leebates7574]

Just a thought, if you wired a small relay to the output of that beeper on the lipo alarm then put it's N/C contact in series on the + or - of the main leads(providing is rated at the correct current!) You'd have an Auto discharger, as soon as it beeps it would break the circuit and stop itself, providing it latches of course

[@RCVideoReviews]

That's how my in-box field discharger works. I have a relay. When the alarm trips, the circuit is opened. Pretty trick.

[@trevorc6793]

Great video, I'd like to build one. what are the benefits of connecting the resistors in Parallel series and not in Series? Thank you

[@RCVideoReviews]

Download the calculator and tinker with it. Changing how resistors are connected changes the resistance in the circuit.

[@FASTFREDDIE-R.C.]

Fun little project 👍🏻

[@RCVideoReviews]

Yup--Easy and functional.

[@HoratioRadkliff]

Can this be used for 1- li-ion 18650 battery?

[@cscientific6077]

Thank you, I liked the video a lot. My biggest take away is that a zero volt lipo battery is inert and safe to discard in the trash. I've had a couple on my desk that I had taped up for a while and didn't know what to do with (other than find a drop off place and bring them there). The calculations and demonstrations with the power supply were pretty cool. I imagine it's not a concern, but if using the device as a battery killer, to drain lipos to zero volts, at some point the 12 volt fan will not have sufficient voltage to run anymore. The cooling fins alone, apart from the fan, would be enough at that point I presume. But I think I'd make mine to run with a separate 12 volt supply for the fans (of course you mentioned that possibility). One last note, descriptions on Amazon are often misleading. I was interested to look into the copper cooling fans in particular. Copper would of course be optimal for cooling (only second to silver). Sadly the fans you linked to are actually aluminum, which is third in line as far as cooling goes. Pure copper would've been cool though. Thanks again

[@dadog92]

Great video!! i was thinking (and maybe is not a great idea) but if would be possible to use a stack of peltier modules instead of the resistors.

[@RCVideoReviews]

I've been thinking about that too. I'm going to order some and give it a go. I thought about using them for this build, but I wasn't sure about fixing them mechanically to the setup (tape/glue) etc. I do want to try them though.

[@shotbyarian]

incredible useful video, thanks! also thanks for sharing the excel file! why wouldn't i want to use a 1 ohm 100w resistor and get 100w across all lipos from 3s to 6s? thanks in advance!

[@RCVideoReviews]

Use the law and work out what you need. Lots of options to get things working the way you want them to work if you can do the basic math.

[@HeadBassVTEC]

have the same tweezers, did not know they are that much temperature resistant, I bought them for their electrical non-condutivity and anti-staticness nice clean setup....I ordered a 300W 10R one, should work without a fan on 6s and I only need a lipo killer for disposal so don't need it super fast, just something usable, not like that lipo killer device sold on ebay which only does 2.5W at 6s and will take a month (bought that one and it's useless)

[@Gavs_rc_hobbies]

Awesome video. I think I might build one of these as all of my battery chargers (except for my LRP Pulsar touch) only ever discharge my batteries at a max of .2-.3 amps (even if you set it at say 3-4 amps) which is very annoying. Plus it will come in very handy for killing a battery that I need to dispose of.

[@RCVideoReviews]

Right on. And you can customize to suit your needs too. I've been using a janky single resistor with an XT60 pigtail wire strapped to the resistor leads for a few years. Figured it was time to make a discharger I wouldn't be embarrassed to be caught using. :)

[@glenncain]

Are you gonna sell the Admiral on your etsy?

[@RCVideoReviews]

I've thought about selling a kit on Etsy. The only reason I haven't done it is because I would be adding limited value (like putting all the parts in one kit) and then flipping it for a small profit. I don't know what the take rate would be. It's also a somewhat limited use case as it requires an iCharger with Extra Discharge mode to be fully functional.

[@technicalsupport6983]

I use a 12volt 4ams ductile fan tfor discharge ......

[@RCVideoReviews]

I built a stand with a motor/esc/servo controller. That's fun too.

[@mcvinda]

Can the lips be recycled ?

[@RCVideoReviews]

When they are fully discharged, they're inert. Basically cardboard, plastic, brass, aluminum, and silicon.

[@Gwanpo_Friend]

내가 원하는 방전기 입니다. 영상 잘보고 갑니다. 👍

[@RCVideoReviews]

Thank you.

[@afcl1984]

Does this work with the Hota F6?

[@RCVideoReviews]

This is a standalone device.

[@afcl1984]

@@RCVideoReviews I know, but the Hota f6 has external discharge and can control the discharge. Using this it can discharge a lot faster.

[@nuddin99]

⁠@@afcl1984I do it with my HOTA D6 with ext discharge function.

[@Vedak2011]

Is there a max wattage that you would recommend staying under? This project really has me curious. I currently use an ISDT FD-200 and it works awesome, but takes about 30mins or so to discharge a 6s 8000mah Lipo to storage voltage. Recently picked up an Icharger 4512 Duo that's rated for 2000w per channel (according to specs) in both Regen and External discharge.

[@RCVideoReviews]

It's just math. You can use whatever wattage (current draw) you want as long as your resistors support it and you can dissipate the heat. You should meet 'the admiral' here: kzbin.info3Szq9KolwVY

[@marianoaldogaston]

I use a electronic load about $20. and do a lot more like telling you how much energy battery have

[@RCVideoReviews]

I need to get one of those.

[@saltyfpv3221]

I would like to make this exact set up to use on my 8000 mah 6s2p liion packs. On my charger they take all day to discharge. Will this be safe on my liions? The have a 45a continuois and 55a peak discharge rating

[@RCVideoReviews]

Yes.

[@ricktaylor51]

This discharger can discharge faster than using a lightbulb, I presume.

[@RCVideoReviews]

You have to do the math. Figure out the resistance of the bulb, and you can make comparisons based on the resistance (4ohms) of the configuration I used. At 25.2v, these resistors have 159 watts input @ 6.3a.