I agree. I'm curious as to the results.Test it, what’s the worse that’s gonna happen?
+1Test it, what’s the worse that’s gonna happen? Again under load measure the voltage from the battery to the tester on the positive leg, it’ll show how much that fuse is heating up or lead loss you’re seeing.
I was told to use a fuse though, because these cheap Chinese Capacitor testers frequently fry out. And when they do, they create a direct short. If I perform a test overnight, it could start a fire if the battery cell is shorted like that, and I have 48 cells to test.30 A 32v AGC fuse is about 3 milliohms but the wildcard is the cheap fuse holder which may be a lot more. Looks from pic you are using an auto type spade lug fuse which is different, maybe better or worse depending on quality. I measured some I had and just the fuse without holder was 2 milliohms for a 30 amp auto fuse. Best of four measured was 1.9 milliohm, worst was 2.1 millohms. 40A auto fuse measured 1.6 milliohms.
Adding in an optimistic 2 milliohms for fuse holder.
5 milliohm with 20 amps is 0.1v drop.
12" length of #10 wire is 1.02 milliohm x 2 wires =2.04 milliohm @ 20 amps is 0.041 V drop.
Without knowing actual terminal lugs and fuse holder adder.
Fuse and its holder is definitely dominating voltage drop. At 0.1v drop and 20 amps the fuse holder will get warm to touch.
2 feet of #14 is 5.15 milliohm so net with #10 and fuse will be slightly worse voltage drop, assuming terminal lugs are equal.
By “terminate” you mean stop the test?If you terminate discharge at 0.1v higher it can be a big difference on total AH pulled depending on what voltage you terminate at.
If you terminate at 2.8v to 2.5v it won't make too much difference. Watt-hr reading will be off by about 3% since it is being summed with continuous 0.1v lower voltage.
What Ah capacity am I looking for?A battery capacity is based on a defined minimum terminal voltage. So for LFP cells the voltage you terminate the discharge has some effect on the cummulative AH count collected over time. The termination voltage you use is somewhat dependent on what load current you test battery at.
20 amps on a 100 AH cell is only 20% CA discharge rate so terminating discharge at 3.00v to 2.90v of cell voltage would give you a good representation of AH capacity. With added cabling voltage drop you should terminate discharge at a bit lower voltage as seen by tester. When the terminating voltage you set is tripped, the AH counter stops. Terminating discharge at lower actual cell voltage stresses battery a little more so best not to go lower then you need to get a good AH representation.
Again, with the four wire remote voltage sensing you would be getting battery voltage reading directly from battery terminals so high current 'A' line voltage drop would not matter.
I've already purchased the newer, better 180w Capacity tester with separate voltage leads from the load. (the 4-wire version).My 2 cents.
I purchased the same unit and on a single LifeFo4 cell it would not pull more then 7 amps.
I did run more then one volt meter just to double check as I figured for $50 I was not buying a lab grade test unit.
The main thing I was looking for was if the batteries I purchased were the ah they said they were.
I was not in a rush so I let it run and the few batteries I tested all came out 1% or less that what they were rated.
I have a 2nd batch of batteries in transit from Cali and once I get them I will top balance and test the same way.
80%? Hey thanks!! You are the first person to answer that. So far, the worst of my batteries have been testing at around 93Ah…Batteries are considered "used up" when <80% of capacity is remaining. That being said they would still be perfectly usable at those capacities. The most important factor is the internal resistance, as once that is very high, you will see a large voltage drop when drawing any significant amount of current.
You can check the internal resistance using a standard tester like all the YR1030:
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Do you have any idea where they started?I've already purchased the newer, better 180w Capacity tester with separate voltage leads from the load. (the 4-wire version).
Since my battery cells are 6 years old, what Capacity am I looking for? How do I know if these are still good or not?
I have 48 cells to test. Once I get a bunch of results, say from 89Ah to 103Ah, which ones do I throw out? Or do I start matching the best to the worst and keep them all?
(Example: 103Ah & 102AH matched with the 89Ah and 90Ah to form one 4S battery?)
30 A 32v AGC fuse is about 3 milliohms but the wildcard is the cheap fuse holder which may be a lot more. Looks from pic you are using an auto type spade lug fuse which is different, maybe better or worse depending on quality. I measured some I had and just the fuse without holder was 2 milliohms for a 30 amp auto fuse. Best of four measured was 1.9 milliohm, worst was 2.1 millohms. 40A auto fuse measured 1.6 milliohms.
Adding in an optimistic 2 milliohms for fuse holder.
5 milliohm with 20 amps is 0.1v drop.
12" length of #10 wire is 1.02 milliohm x 2 wires =2.04 milliohm @ 20 amps is 0.041 V drop.
Without knowing actual terminal lugs and fuse holder adder.
Fuse and its holder is definitely dominating voltage drop. At 0.1v drop and 20 amps the fuse holder will get warm to touch.
2 feet of #14 is 5.15 milliohm so net with #10 and fuse will be slightly worse voltage drop, assuming terminal lugs are equal.
When brand new they tested at around 115Ah because the original owner was bragging how the system was 1,400Ah. I couldn’t figure out how he came to that number until I saw that CALB cells usually test at 115Ah or so for the first 20 cycles even though they eventually rest at 100Ah.Do you have any idea where they started?
For me at 85% and above I am using it if it is working.
After I installed the ring terminals and upgraded to 10 gauge wire, the voltage difference went down to just 0.1v at a 20A load from the capacity tester.Those fuses resistance change with current though, as they get close to their rating the resistance goes up this causing the heating/blown fuse. Testing the static resistance isn’t really testing much.
Again measure the voltage drop from battery to tester terminal under load (even 5-10a) will get you your lead/fuse losses.
Yes, I was able to run the capacity test at 20A using the old 2-wire 150W tester. However, it shut off around 4 hours into it displaying low voltage cutoff. So I turned down the amperage to 10A load and continued the test.So we’re you able to run a full test at say 10 or 20a and saw good voltage on the tester?