Big Squid Lipo-shootout 2

[simplechamp]

Originally Posted by magman

Now that is a great idea. I wonder if someone here could do some real bias testing on 4s and 5s set ups with say 4-8 different manufacturers batteries and post the results

I've seen a few threads around discussing that very thing. I thought BrianG had ordered a bunch of high-wattage resistors at one point to build a test rig, but not sure how that panned out.

It would definitely be an expensive challenge to build a test rig that could handle higher voltage packs at 30C discharge rates. Also, finding people do donate packs for testing that may or may not survive said 30C discharge might be tough.

I would rather see how a pack holds out for 10 sec. at 30C than the whole discharge cycle at 6C like BigSquid did. That is a more realistic torture test of what it would experience in the vehicle.

[BrianG]

Originally Posted by simplechamp

I've seen a few threads around discussing that very thing. I thought BrianG had ordered a bunch of high-wattage resistors at one point to build a test rig, but not sure how that panned out....

It really didn't pan out. Testing methodology wold have been too arbitrary (but MUCH better than any butt-dyno testing on these reviews TBH) to be of any viable use. I did do a small 10A version, and it worked, but needed constant manual adjustment to maintain a consistent current depending on the cell's IR, which does change over the cycle. What is needed is a true constant-current system that can be computer controlled for continuous testing and repetitive burst testing, which would compensate for dropping battery voltages.

And, at higher pack voltages, testing on a bench creates a LOT of heat!!! After calculating the thermal load, I would need a HUGE heatsink; something like a 400ft^2 heatsink and that's with forced airflow. 6s @ 200A is almost 4500w. Any idea how much heat that is? Believe me, my small 10A test rig on 3s generated a substantial amount of heat.

Then, as the BigSquid shootout proved, people will always complain (not targeting you Neil) that testing procedures weren't right. And getting everyone to agree would be impossible. And even if a procedure was finalized, it would be too complex for Joe Sixpack to comprehend, and would just end up getting whatever pack had the flashiest label (or best advertising).