DC Load test large battery packs. Rheostat?

I have large battery packs, up to 60v@36Ah and output around 2000-3000w, which i would like to troubleshoot by loading them.

I'm thinking a variable rheostat + Battery Coulometer

https://www.aliexpress.com/item/33003268665.html?spm=a2g0o.productlist.0.0.1e486bf7G9ytVD&algo_pvid=900dedeb-d0b5-45cc-82ec-46fa5f01717f&algo_expid=900dedeb-d0b5-45cc-82ec-46fa5f01717f-0&btsid=0b0a0ae216030144815793199e0419&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

https://www.aliexpress.com/item/32702066121.html?spm=a2g0o.productlist.0.0.2dc54e81NxnVXw&algo_pvid=602dac5b-673b-4adb-927f-eab0d8544445&algo_expid=602dac5b-673b-4adb-927f-eab0d8544445-0&btsid=0b0a0ae216030146078298578e0407&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

I'm thinking of using the Battery Coulometer to capacity test them at of course something like 0.2C.

Is this a good idea or am I lost here?

Bump anyone?

It doesnt look like that rheostat will stress your 60v packs to 3kW ? ..(50A)
For that 3kW you would need a 1.2ohm resistance load, but that site doesnt list a 1 ohm resistor above 2kW capacity.. ( 34A max @ 60V)...but fine for the 0.2 C tests.
Maybe another vendor ?
Or,..this is another option..
https://endless-sphere.com/forums/viewtopic.php?f=14&t=74567&hilit=Hairdryer
Just watch the video !

Hillhater said:

It doesnt look like that rheostat will stress your 60v packs to 3kW ? ..(50A)
For that 3kW you would need a 1.2ohm resistance load, but that site doesnt list a 1 ohm resistor above 2kW capacity.. ( 34A max @ 60V)...but fine for the 0.2 C tests.
Maybe another vendor ?
Or,..this is another option..
https://endless-sphere.com/forums/viewtopic.php?f=14&t=74567&hilit=Hairdryer
Just watch the video !

Click to expand...

Thanks, but the rheostat is variable up to say 10 ohms so i should be able to set the resistance to 1.2 ohms
I will check the video. Thanks!!

Thanks, but the rheostat is variable up to say 10 ohms so i should be able to set the resistance to 1.2 ohms
I will check the video. Thanks!!
[/quote]

If you have a 10 ohm rheostat capable of dissipating (say) 100W and you set it to 1 ohm, it has only 10W capability at that setting. It will burn out if you ask it to dissipate 100W. Better to obtain large fixed resistors and connect them in series and/or parallel to obtain the desired load resistance, with combined (additive) capacity to dissipate the full power applied. They will get quite hot if operated at capacity, so overbuild by a substantial factor.

eikido said:

Thanks, but the rheostat is variable up to say 10 ohms so i should be able to set the resistance to 1.2 ohms
I will check the video. Thanks!!

Click to expand...

The description lists the MAX RESISTANCE of the 3000W rheostat at 5ohm...and 1 ohm for the 2000W version.
Remember MAX RESISTANCE is the smallest numeric it can reach
So the only rheostat they offer that can be set at 1 ohm , is the 2000W version

PS... also read the other posts on that linked thread...several options for load test rigs suggested.

I built one arger than DrBass.


Alot more powerful. Some 30 Kw. i used a CA3 datalogger, 500A shunt, and 30kw of ( 1100w-1700w) strip heaters. About 30 of them.

DogDipstick said:

I built one arger than DrBass.


Alot more powerful. Some 30 Kw. i used a CA3 datalogger, 500A shunt, and 30kw of ( 1100w-1700w) strip heaters. About 30 of them.

Click to expand...

Oh man, I'm so glad i asked all of you guys.

DogDipstick, what ohms are your heater loads?

eikido said:

DogDipstick said:

I built one arger than DrBass.


Alot more powerful. Some 30 Kw. i used a CA3 datalogger, 500A shunt, and 30kw of ( 1100w-1700w) strip heaters. About 30 of them.

Click to expand...

Oh man, I'm so glad i asked all of you guys.

DogDipstick, what ohms are your heater loads?

Click to expand...

1200w @ 240v = 48 Ohme.

About 20 of those. So about 2.4 Ohms when in parallel, as they are.

Then I also have 1700w @ 240v strips, they are ~33 Ohms ea.. 10 of those... so 3.3Ohms.

part numbers

Tempco csf00019, 1700w, 240v
Tempco csh00331 1200w, 240v.

At 80v, the 20 ( 2.4Ohm array) will pull about 2700w at 80v voltage.

It is a nice space heater. Lol.

DogDipstick said:

I built one arger than DrBass.
Alot more powerful. Some 30 Kw. ............
........ About 30 of them.

Click to expand...

Im sure yours is bigger ...physically, and probably cost wise also, !...
But i am not convinced it is bigger power capacity than the Dr’s hair dryers..
??? Maybe you should think through the maths again ?
20 of your elements at 80v gives 2700W ...$s??
5 of DrB’s dryers at 80v gives 3200W ......for $50 !
Or,..for the OPs 60v, 3000W testing 10 of his dryers at 60V. Gives 3000W ...for $100
He would need 40+ of those 1200W strips for a similar load, ....or 28 of the 1700W strips !
PS...how much did you pay for those strips ???
(Walmart lists them at $160 each ! )
https://www.walmart.com/ip/TEMPCO-CSF00019-Heater-240V-19-1-2-In-L-1200-Deg-F/140731763

Hi,

Take a look at my load bank.



Rack houses 24 locomotive braking resistors, 1.2kW each. Can easily series parallel reconnect for desired load. Most I've done was 200V, 400A. Gray box on side is 1000A contactor with homebuilt IGBT buck converter. Resistors were surplus buy at $7 each.

Regards,
major

wow that's major

Hillhater said:

(Walmart lists them at $160 each ! )
https://www.walmart.com/ip/TEMPCO-CSF00019-Heater-240V-19-1-2-In-L-1200-Deg-F/140731763

Click to expand...

I paid about a dollar each. Scrap broker relationship has its benefits. Completely willing to triple my profit if you wish to buy some from me at 3$ ea.


The CA3 and the CA datalogger, shunt, is where most of the cost is. That is about 250$ shipped.. then I can also use it on a bike ( the datalogger, swap in swap out hot plug) . I also have a roll of 1Ohm/foot Nichrome that I calculated for a huge load (( for single cell voltage tests.. not a pack.. ) .. Id need like ten sets of 1mOh) ( sets of foot long, in parallel.. )) for a good load And a barrel of water... but that is wet and messy. My garage is not heated if I dont have propane this or that month. So I use the load bank and fans.

Daisy chaining hair dryers? lol. Nah. ...heating the garage effectively? yup. I got a ton of stored power to burn at any time.

It also houses 2-4 kwh of ballast battery to run a 16s (2.7kw) or 22s (3.7Kw) Cellpro Powerlab off of. That is for cell level data-logging, charging the ballast, and ... heating the garage through the load array: at will.

I do not want to push the strips red hot, even thought they certainty will go there. They get dull red around 140v.... and over.. to bright red @ 200v+. The datalog takes a few hours, on a big pack.... ; I do not want to be in constant attendance. I got other things to do in the shop too. There is also a constant current source in the circuit too.

I got it down to the BTU. Dont worry. It is a good load. I do the math for the applicable device under test....... and set up the load just for that ( test).. so the power / current will be different between different tested voltages and packs.

It is honestly a work. Lol.

major said:

Hi,

Take a look at my load bank.


Regards,
major

Click to expand...

hahah looks about exactly like mine.. rack mounted, strips on top.. utility junction box: Lol. Shelves. I have been onthe lookout in plasma cutters for an IGBT that I do not have to pay for.

...............but my GoKart is a classic 1963 Rupp DartKart,.... bout the only difference.