External discharge with power resistors and iCharger 206B

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leaftye
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External discharge with power resistors and iCharger 206B

Here's a long shot, but you guys are pretty smart.  If we can figure this out, maybe it'll help the other members testing batteries right now too.  

 

My Turnigy Reaktor (iCharger 206B clone) can use regenerative discharge to a lead acid battery for up to 20A/300W, but I'm thinking about using a bank of power resistors instead.  The primary advantage is not having to take care of a lead acid battery.  

 

I intend to log discharge data to my computer to test batteries, and from what I understand, using fans and bulbs as resistive sources doesn't work because their resistance changes...or something.  Whatever it is, I found a couple posts that says it's only good for discharging batteries, but not for testing.

 

Only one lithium ion cell (4.2V) will be used.  As I understand, the 20A limit applies no matter what, so the 300W limit won't be reached with one lithium ion cell.  I'd like to discharge at 10A and 20A, although I'd happily go over 20A too if it can be done.


First question is about the balance leads.  The manual says they have to be used, so do I use the last two wires of any balance cables?  I've done this with a regular discharge, so I think this would work here too.


Next question is simple, but answer isn't.  What power resistors do I use to achieve the maximum discharge capacities of this charger?  If it helps, I'm looking at these resistors, but am open to others.

100W 0.5 ohm  

50W 1 ohm  

50W 0.3 ohm  


I'm trying to use this guy's iCharger Extended Discharge Tool spreadsheet.

http://www.rcgroups.com/forums/member.php?u=142090

 

The iCharger manuals can be downloaded here.

http://www.rcgroups.com/forums/showthread.php?t=839657

 

These resistors will need to be kept cool, and I'm not asking for help with that, but here's my plan if you're curious.  The resistors will be glued to 2"x3" hollow aluminum tubing.  Plastic tubing will be run into the ends and sealed with a plate and sealed with GE Silicone II.  The tubing will have water run through it with an aquarium pump drawing and discharging water from a 5 gallon bucket filled with chilled water.  Why this way instead of a big heat sink and fan?  All I need is the rectangular tubing, so this costs me very little.  Quiet cooling and huge heat capacity is nice too.

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

Edited by: leaftye on 07/23/2014 - 02:29
Illuminaria
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..depending on what you already have. You can set the LV cutoff, but that’s with 3 series cells using balance cables, or wires with magnets on the end. Sorry, for parallel discharge to storage level I do use regenerative..and a old group 24 battery in plastic box. My 106b gets barely warm doing it this way and no fan running.

The huge user base on the link you posted would be the better place to post this question as way more users there for ideas.

leaftye
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The bulb idea would normally be great, except I need to log discharge data. Bulbs don't work because it means not all the current flows through the charger, which means inaccurate data.  I appreciate the idea though.   

I am going to do some regenerative discharge for now, but the lead acid batteries I have right now probably won't last another two years.  Getting new lead acid batteries every few years just for battery testing isn't practical when resistors might last a lifetime and cost much less.

I'll try asking on rcgroups if this thread doesn't produce the answers I'm looking for.  There are some pretty smart and experienced people here though, and some of them are into rc.  

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

raccoon city
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leaftye wrote:

There are some pretty smart and experienced people here though, and some of them are into rc.

8)

Illuminaria
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leaftye wrote:

The bulb idea would normally be great, except I need to log discharge data. Bulbs don’t work because it means not all the current flows through the charger, which means inaccurate data.  I appreciate the idea though.   

I am going to do some regenerative discharge for now, but the lead acid batteries I have right now probably won’t last another two years.  Getting new lead acid batteries every few years just for battery testing isn’t practical when resistors might last a lifetime and cost much less.

I’ll try asking on rcgroups if this thread doesn’t produce the answers I’m looking for.  There are some pretty smart and experienced people here though, and some of them are into rc.  

I’m a dumb one and did not know light bulbs were different from hot resisters Smile These are in series with the out put side and Logview seems to have it figured out using Ohm’s law but can’t check absolute accuracy. This is why I like regenerative discharge and never looked back vs external.

Yeah my battery is used for my heli lipos, car audio, now flashlights. Out in the field the car battery works nice as well but certainly understand not wanting a nasty old wet cell on the bench. Unfortunately we cant use bench supplies with regenerative discharge.

leaftye
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Wait, when you say your bulbs are on the output side, do you mean on the same side and the regenerative battery, or on the positive cable connected to the battery being discharged?  If it's the latter, and it's not connected to the negative wire going to the same battery, then all the current would pass through the charger like I need it to.  

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

Illuminaria
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load is on output (+) side and icharger must use balance cable. Check out the diagram in icharger manual.

I only deal with 7A not 20A discharge so your options would be different from mine but icharger deals with heating resistive change on the bulb. Your best option sounds better with power resister depending on balance cable needed to be built.

leaftye
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Update

 

I gave up on external discharge using power resistors since the folks on rcgroups don't seem to like it anymore.  I ended up picking up some li-pos to use with regenerative discharge testing.  The big disadvantage with those is that they have to be discharged, which slows down testing.  The other 20% inaccuracy.  Maybe some day I'll get a CBA tester or dc electronic load station so I can do back-to-back discharge tests with fewer breaks and much more accurate results in high current discharge tests.

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

WarHawk-AVG
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Ceramic resistors bathed in oil (kind of like those oil filled room heaters)

leaftye
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If I end up getting something like a iCharger 406B, I may try using resistors again.  Oil cooling could work, but I still favor my original plan to use water cooling because water has a huge heat capacity, and if the water starts getting hot, I can exchange it, dump in some ice, or use a bigger reservoir afterwards.  Also, water is dirt cheap and easy to clean up compared to oil.  I doubt I'll get a 406B though.  I have no need for that much charging capacity, but I do for discharging, so I'd rather put the money into something made specifically for discharging.

 

Now if I could use that oil to fry some chicken while doing discharge tests...

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

Illuminaria
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You do have the option to use fans, lights, space heater (DC) or whatnot to reduce recharge load across battery. I only deal with cycling 24 ICR laptop pulls so using small box fans works fine but have 50 watt hollow wire wound as back up for my LiPo packs.

I did a month school at Honeywell, Torrey Pines, where there must have been 5 of the HP load stations set up for DC thruster testing. So, suspect the San Diego area has a big market in used equipment or rentals for short term use?

lagman
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@leaftye and all the others:
I see that you are struggling between two options that are both bad.
1- Using a resistor in line with the battery tested. Not very elegant as you need to calculate a new resistance value for different batteries and discharge current
2- Using the regenerative discharge function and a lead acid battery. Accurate, versatile, but expensive, bulky, needs maintenance and once the lead acid battery is full it stops the discharge…

There is a better solution that combines both of the above solutions!

The user eecs on RCGroup had a brilliant idea. If you are an electronics engineer you already understood how brilliant that is… For the others I’ll quickly explain.

The idea is to use transistors on the input side between the charger and the PSU.
When you want to charge a battery, the two diodes conduct current from the PSU to the charger. In that case the transistors are OFF and everything works as usual (except that there is about 10W lost in the diodes at 20A).
When the user activates the regenerative discharge, the charger will try to feed power back to the PSU. This raises the input voltage and doesn’t work with a PSU… But when the voltage rises above 12V, the transistors start to conduct!
During regen discharge, the input voltage will stabilize to about 16V (the transistors need 4V to conduct) and dissipate the power.

That’s the best solution I’ve found so far. It’s relatively cheap. Transistors are about $1 each and can dissipate 75W each. You just need to find a good way to cool them…
With this solution, no more messing with output resistors inline with the tested battery!

I’ll soon build that thing, I ordered all the parts needed but I’m waiting for Hobbyking to have stock on the Reaktor in the EU warehouse… J)
If there is an interest I can document the steps needed to build that thing. It is quite simple to build if you know how to solder and properly heatsink a transistor!

So… Is there an interest?

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

leaftye
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Illuminaria wrote:
So, suspect the San Diego area has a big market in used equipment or rentals for short term use?

It might, but I need long term use.  I got a dc load now.

 

lagman wrote:
So... Is there an interest?

Yes, I'm interested in seeing your build. I just ordered a second Reaktor yesterday.  It should be here in a couple days.  I don't know if I'll use it now that I have a big dc load, but it'll be nice to have the option.  I could compare the results of these options.

 

I've been using regenerative discharge, and it's not ideal, but it's not too bad.  The input battery is a pair of 2000 mAh 3S li-pos in parallel.  I can discharge quite a few batteries into it before it needs to get drained, but it'll drain plenty of power if it's left attached to the charger between discharge tests.  

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

lagman
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leaftye wrote:
Yes, I’m interested in seeing your build. I just ordered a second Reaktor yesterday.  It should be here in a couple days.  I don’t know if I’ll use it now that I have a big dc load, but it’ll be nice to have the option.  I could compare the results of these options.

 

I’ve been using regenerative discharge, and it’s not ideal, but it’s not too bad.  The input battery is a pair of 2000 mAh 3S li-pos in parallel.  I can discharge quite a few batteries into it before it needs to get drained, but it’ll drain plenty of power if it’s left attached to the charger between discharge tests.  


I’ll do it… When I get my reaktor.
If you can test the accuracy of the Reaktor against your DC electronic load I would be very interested in seeing the results. (I want to know how close a discharge capacity measurement is to the reality).

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

leaftye
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lagman wrote:
I'll do it... When I get my reaktor. If you can test the accuracy of the Reaktor against your DC electronic load I would be very interested in seeing the results. (I want to know how close a discharge capacity measurement is to the reality).

I'm going to redo the Basen tests that were done with regenerative discharge, which will make it easy to do a comparison.  

My Reaktor is moving faster than I expected.  It might be here tomorrow.

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

lagman
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Damn you are lucky. It really pisses me off that they have no stock in the EU warehouse!
What dc load did you buy?

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

leaftye
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lagman wrote:
Damn you are lucky. It really pisses me off that they have no stock in the EU warehouse! What dc load did you buy?

Not lucky.  I coughed up the extra money for DHL delivery from the international warehouse.  I wanted to wait for the US warehouse to get stocked, but I felt I owed it to certain people to get this done sooner than later.  I'm going to be really upset if the US warehouse gets new stock today or tomorrow.

 

The dc load is a Maynuo M9712C. 

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

texaspyro
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As far as renting test equipment goes… it is very rare to be able to rent a piece of equipment for a month for less than you could buy something workable on Ebay. I’ own a buttload of test equipment for that very reason…

paulxteam
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Hello, i saw your idea for the external resistance circuit and i want to build one for my reaktor 250w charger, if you could put some pictures of the circuit that would be great because i know how to solder and measure but don t really understand everything on that scheme you uploaded, thanks.

Paul

garrybunk
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leaftye or lagman, was there ever a post on that build? I’m curious to investigate this as I’m considering trying to discharge test 8.4v bike light battery packs at 3A to 5A (may even go higher). My charger is a rebadged iCharger 206B.

Or anyone else have “How-To” links? (I thought I was going to use external power resistors.)

Thanks,
-Garry

My Bike Lights Thread, Optics (TIR) Comparison Beamshots, Diffusion Techniques


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