Lipo Load Bank for Discarging (moved from swap shop)

[Darin Jordan]

When you think about it; it's ALOT of energy that is being turned into heat in only a few mins. I don't suspect you will get the actual "peak" temp down, but more fans would minimize how long that "peak" is sustained. Once the load ramps down the 2 fans cool everything very quickly.

Tyler also recommends that you run the fans off the power supply, not off the "load" (I think I saw that you already were). That way the fans run at full speed and beyond the discharge cycle.

My fans are 24V, though they work fine on 12V too. I just finished up a new power supply that uses a pair of 75A power supplies and has 12V and 24V taps.

One of these days, maybe I'll add some LEDs and other "bling"... :)

[RaceMechaniX]

Darin are you missing a 0 in your wattage? 150W isn't much for cycling.
TG

[Darin Jordan]

Darin are you missing a 0 in your wattage? 150W isn't much for cycling.
TG

I meant to type "75A"... Oops. :)

[RaceMechaniX]

That's more like it!

[NativePaul]

I could be being naive here as I am inexperienced with electronics, but I was thinking of peltier devices, 60w devices are pretty cheap, a stack of 10x12v devices for 2-3s and 20x24v ones for 4-6s would be about £50/$75 for the lot.

If they were stacked together would the cold side of one would cool the hot side of the next etc, so you would only need to sink away 60w of heat from the end of each stack?

[ray schrauwen]

The one hot end of the stack I think would go nuclear. I have one somewhere...

[RaceMechaniX]

Hey guys if you are looking at building a load bank now is a good time. I just check on Allied Electrics site and some of the 1 and 2 Ohm planar resistors are back in stock and reduced prices.

https://www.alliedelec.com/spectrol-...00jb/70218911/

https://www.alliedelec.com/ohmite-tap600k2r0e/70022403/

-Tyler

[TRUCKPULL]

Tyler, Mike, or Darin

The for-mentioned heat sink - https://www.alliedelec.com/aavid-the...6000/70115158/
is not in stock.
They recommend this as a replacement - https://www.alliedelec.com/aavid-the...6000/71076834/
$71.00 US seems a little pricey.
About how much were the ones that are not in stock at the moment, if you can remember??

Larry

[RaceMechaniX]

From memory they were about the same price. Go onto eBay and find a suitable replacement.
https://www.ebay.com/itm/No-15J9645-...QAAOSwhpZaBfYk

https://www.ebay.com/itm/Brand-New-N...cAAOSwAC1aBb8d

[NativePaul]

I want to be able to graph discharges at close to the 45A I run my boats at to test packs, as well as drain unused packs back to storage voltage quickly.

The Powerful FMA chargers have good graphing capabilities, and resistive discharge capabilities, but to get the maximum discharge out of one you would need a different resistor for each voltage of battery you use, which would be 5 for me.

The high end duo ichargers can use the voltage booster that they use to charge big packs to increase the voltage of the discharge up to a user definable level (under their max charge voltage) so on a 4010 duo I could set it to 42V and with a single 1ohm resistor I can discharge a single cell through to a 6s pack (the biggest I use) at 40A. Unfortunately however the ichargers don't have the graphing ability FMA do, so I have been waiting for one of them to combine both of the features, but I see above that there is a third party graphing software for the icharger, how are you guys getting on with that? I guess it has had some use now, can it log amps volts and was over milliamphours?

Now getting onto topic, while I have been searching this I saw that the flyby have come up with a pretty neat solution to the resistive load, which is rewiring an 1800-2000w hairdryer, they are available everywhere from as little as £20 ($25?), small and light so field usable, and never get hot enough on the outside or exhaust to burn you, it is likely to be a fair bit louder than a resistor on a big heatsink with multiple slower fans, but could also do duty as a boat drier for the unfortunate, and a LiPo warmer when fed with lower voltages.

https://www.rcgroups.com/forums/showthread.php?2123395-1875W-hairdryer-converted-to-resistive-discharge-load

[RaceMechaniX]

Paul,

To answer your questions:

Graphing: The iChargers do have the capability of logging data and graphing using LogView. It's free and works quite well. I cycle batteries on my 4010 and use the logging feature to save both charging and discharge cycles in one file. The software is very good. Only downside is it does not log the cell IR values. I have to manually record these.

Discharging: The Junsi has two limits. 40A or 1000W, which ever comes first. The key is to match the load resistance to the battery voltage you are trying to drain. As you say the Junsi has a buck boost converter inside which can increase the voltage to the load to reduce the current in till it hits the 1000W limit. You also need a load resistor that is capable of 1000W too.
I use a 0.5 Ohm or 1 Ohm load with mine. The 0.5Ohm is for 4 cells and below and the 1 Ohm is up to 10 cells. This way the charger can always hit the 40A limit on the battery side without hitting the 40A limit on the load side.

Tyler

[jevmax]

Have you tried testing battery packs at realistic rates of discharge using the West Mountain Radio CBA 10X Multiplier? That would seem to be the perfect instrument for what y’all are wanting to do.

[RaceMechaniX]

I am not going to that high of a level since I can compare the lower current testing to what actually happens in a boat. If a chemistry does well on the cycle I run it generally will work well in the boat. What I run into is the mechanical limitation of the battery tabs and wires at the high currents. I do have a friend who is pulse testing these cells in the several hundreds of amps range. The results seem to correlate well.

[ray schrauwen]

Some people have gone as simple as using a plastic storage bin with unraveled magnet wire submerged in water to create resistive loads. Some even use this method to test server power supplies to make sure the can be loaded to full capacity.

[dasboata]

I bought 4 of these on ebay for $22 each if someone wants 2 LMK https://www.ebay.com/itm/VISHAY-RESI...72.m2749.l2649