Discharging through a high power resistor.

[NHENRY]

I have limited knowledge on this and I have been looking around many forums, my mind is still not clear! Any links to additional information would be great as I am always willing to learn!

I have the ICHARGER 4010 capable for 1600 watt external discharge. I have 3S and 6S Lipos that I would like to discharge.

Would the resistor below be efficient and safe to use when switching between discharging 3S and 6S or would I need a resistor of unknown value for my 3S and another resistor of unknown value for my 6S Lipos.

http://www.digikey.com/product-detai...574-ND/2367679

I understand that 1 ohm is the most efficient for the ICHARGER 4010, as this charger is 40 amps discharge at 40V

Could anyone recommend a resistor that would safely enable me to get the max 1600watt discharge from the ICHARGER 4010.

People are using converted hairdryers as a resistive load, but this is too noisy for me!

Kindest regards

NHENRY

[Smoggie]

That would work fine. i'm using a hairdryer but in effect it's just a 1 Ohm resistor. If you are using the discharge method where you plug your load resistor into one of the channel outputs in the front, and discharge the batteries from the other channel, then 1000W is all you can do. I find 1000W is plenty even when discharging several 6s 5000mAh batteries.

You can only hit 1600W if discharging from both channels into a load connected to the input side of the charger.


The resistor going to get very VERY hot, the data sheet indicates around 400 Deg C, so you need to make sure it cant be touched and is away from anything that is flammable or anything that could be damaged by heat. I prefer the hairdryer for that reason, it can just sit on the workbench and doesn't get hot at all, much safer.

[Toocool4]

I have the 4010 Duo too but I have never tried this kind of discharging.
What I usually do when I get back from the field and have not used all my batteries, I just use regenerative mode and use the unused batteries to put the used ones back into storage. This way all the batteries go back into storage mode and very little energy is wasted.

[Sirolf]

I am in the process of building a lipo heater case with a built-in auto discharger. In the begining i also looked at the high power resistors but i didn't like diversity in getting the required discharging amps.
I chosed to use LM317 voltage regulators and in particular the HV version ones which can handle 60V easily. Now i can set the desired discharge amps by switching several regulators on or off by means of a simple toggle switch.

https://www.helifreak.com/showthread... 6S discharger

[NHENRY]

Thanks for the feedback guys! Sirolf, I like your regulator design. What are the diversity problems! So it is not a case of just plugging the resistor on the other channel and letting the icharger controlling the discharging process?

[Smoggie]

Originally Posted by NHENRY

What are the diversity problems! So it is not a case of just plugging the resistor on the other channel and letting the icharger controlling the discharging process?

If using the iCharger then there are no problems, you just plug the batteries in and discharge. the iCharger takes care of differences in battery voltage and also cuts off the discharge when you get to target voltage... It makes it all very simple.

[TheBum]

I bought nine 1-ohm, 100W resistors on eBay that I plan to put in a 3x3 grid to yield a 1-ohm, 900W load for my 308DUO. I also bought some heavy aluminum channel stock to act as a heat sink.

One suggestion I saw was to immerse the load in distilled water, which would not be corrosive and would provide good cooling.

[Sirolf]

I not familiar with an iCharger and don't think you can use it with an external discharge system.

By diversity i mean i like to set my discharge amps myself. As you can see i use 12 regulators and divided into groups of 2. Every group can be switched on and off independantly therefor controlling the amps.

2 groups already can pull 5 amps on a 12S lipo

[NHENRY]

Originally Posted by Grumpy_Old_Man

If using the iCharger then there are no problems, you just plug the batteries in and discharge. the iCharger takes care of differences in battery voltage and also cuts off the discharge when you get to target voltage... It makes it all very simple.

Ok thanks for this! I have decided to go with a 1000 watt 1 ohm wire wound chassis resistor!

[NHENRY]

Thanks Sirolf!

[Smoggie]

Originally Posted by Sirolf

I not familiar with an iCharger and don't think you can use it with an external discharge system.

By diversity i mean i like to set my discharge amps myself. As you can see i use 12 regulators and divided into groups of 2. Every group can be switched on and off independantly therefor controlling the amps.

2 groups already can pull 5 amps on a 12S lipo

Yes you most certainly can use external discharge systems with the iCharger duos, they are the best chargers available for it. You can do either regenerative or using a resister for load. Uniquely among chargers you can cross discharge with the batteries on one of the dual channels and the load on the other. You can do up to 40A / 1000W discharge this way.

I can pull 40A out of 6s LiPos with this discharge setup (I do it regularly). I use a modified hairdryer for a resistive load, works great! One of the advantages is that you can discharge any cell count battery without adjusting anything, the charger does all that automatically.

You can actually do up to 1600W discharge if you hook up batteries to both channels and put the load on the input side of the charger but the cross channel method is a little more convenient, and 1000W is plenty.

Pretty much knocks the socks off any other discharge method that I'm aware of.

[Smoggie]

Originally Posted by TheBum

I bought nine 1-ohm, 100W resistors on eBay that I plan to put in a 3x3 grid to yield a 1-ohm, 900W load for my 308DUO. I also bought some heavy aluminum channel stock to act as a heat sink.

Bum,

How would you maintain 1 Ohm resistance if using three? Wired in series will be 3 Ohm (too high). Wired in parallel will be 0.33 Ohm (too low)

I'd have thought that you would want either 0.33 ohm resistors (wired three in series) or 3 ohm resistors (wired three in parallel). Either would give overall 1 Ohm resistance and 300W power rating.

[TheBum]

Originally Posted by Grumpy_Old_Man

Bum,

How would you maintain 1 Ohm resistance if using three? Wired in series will be 3 Ohm (too high). Wired in parallel will be 0.33 Ohm (too low)

I'd have thought that you would want either 0.33 ohm resistors (wired three in series) or 3 ohm resistors (wired three in parallel). Either would give overall 1 Ohm resistance and 300W power rating.

I'd be using nine: three in series and three in parallel. That's equivalent to three 3-ohm resistors in parallel, which yields 1 ohm.

[Smoggie]

Ahh.. sorry, i missed the 900W bit!

Yes that will work fine. Immersing electronics in water 'feels' wrong somehow, but if it's distilled then it should work i guess. You would pretty quickly boil the water unless you used a pretty big reservoir.

The hairdryer is worth considering, the only tricky bit is finding a dryer that can easily be wired to give the correct resistance.

[Crowbar]

Try a Deep Cycle (aka AGM) battery. You can discharge your LiPos into that and then recharge your LiPos from the deep cycle.

[pctomlin]

I utilized some of the information and learnings from Redbirds thread and built this to discharge batteries.

https://www.helifreak.com/showthread.php?t=409353

[Smoggie]

Originally Posted by Crowbar

Try a Deep Cycle (aka AGM) battery. You can discharge your LiPos into that and then recharge your LiPos from the deep cycle.

Yes, but the problem with a deep cycle (other than it being big expensive and weighing a ton) is that it's only 12V so would severely limit the power of the charger. You would need at least two deep cycles in series to get the most out of the charger. Also the current the iCharger would pull from a deep cycle (65A) would kill the battery quite quickly. They aren't designed to be discharged continuously at that sort of current.

I'm assuming here that the charger in question is being powered in the home from a wall socket/PSU.

[rhodesengr]

I use my icharger in Discharge+ mode. The problem is that no one resistor will give you maxium discharge current and the manual does not make it very clear.

So for example, I have a 1 ohm 225 watt Ohmite resistor. I set it up with some 3S batteries. The most current I could get was about 11 amps. I set for 15 but the icharger self regulated at 11.

So 10 amps is a lot better that what you would get using regular discharge mode but I don't think that is the rated maximum.

So the question is which way do you go to get more current and what happens if you go to 6S. Since the manual does not do a great job of explaining all this, you'd have to play around.

If you have several 1 ohm resistors, 2 in parallel would give you .5 ohm and two in series would give you 2 ohms. So one could try those value and see how they affect max discharge current.

Whatever you end up using, always do the power calc. P=I*I*R Watts.
Make sure the dissipated wattage is within the rating of your resistor.

[Smoggie]

The iCharger duos make it very easy. You just need a resistor load of around 1 Ohm which you hook up on one channel and you put the batteries on the other. It's doesn't matter what cell count battery you hook up, the iCharger Duo looks after all of that.

[cyclo]

Here is a useful Watts / Volts / Amps / Ohms Calculator:

http://www.rapidtables.com/calc/elec...calculator.htm

Just enter any two (or three) values to get the other value(s).

I use a simple parallel/series resistor configuration myself to get the desired 2.5 ohms. So when discharging a 5000 mah 6S lipo the array will dissipate up to 254W when the lipo is fully charged. Takes around 10 minutes to discharge it to 50%.