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Old 02-10-2019, 09:24 PM
bistander bistander is offline
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EverStart U1 Battery

Quote:
Originally Posted by BobFrench View Post
I have been running a 3 Battery System with the following setup using 6 batteries, ...



Bob
Hi Bob,

I noticed you are using the EverStart brand U1, 230 CCA FLA batteries. Did you verify these to specifications or other test for capacity when you first got them? I ask because I have noticed something about one I just tested. I'll outline that below. First, a photo of my battery, and the Black & Decker (B&D) charger which I used.



I am using a West Mountain Radio CBA III tester and laptop to log constant current discharge and plot against Ampere-hours. Here is a family of curves at various C-rates. About 7.5A is the limit of the unit. The C/20 was interrupted due to laptop timeout. More on that later.



Next is a discharge comparison of the first run on this battery at 7.0A and cut-off set to 9.0V vs a similar run at 7.2A (C/2.5) with cut-off set to 10.5V done 4 days later. Notice a 12.7% increase in charge (Ah) on the later test. Also the the higher voltage for the later test indicates a much lower internal resistance and likely near 20% more energy from the battery under the same conditions and charged the same.



On the above curve, red trace for the 7.0A, notice the line goes horizontal near the end. This prompted me to further investigate when running the C/20 curve by setting a low cut-off. As I mentioned earlier, the length of the 20 hour discharge caused several computer disruptions so I simply started up again renaming part1, part2, etc, without recharging in between the parts. By doing this, the charge (Ah) from the individual parts are additive. Total Ah is 17.57Ah for the 20 hour rate. Although I was unable to find a specification on the EverStart U1, 230CCA battery, similar products appeared to be rated around 18Ah for 20 hours.* {see edit}



These "knees" on the discharge curves indicate a single cell (of the 6-cell battery) giving up. So this battery has one cell good for 12.02Ah, one cell good for ~15.36Ah and 4 cells good for 17.57Ah or more.

Just for kicks, I used my new instrument to record a partial recharge of this battery after the last test and calculated the Ah and Wh and plotted it. Takes a bit of time to do, but I think will yield some accurate energy data for both charge and discharge. Attached.



Regards,

bi

{edit of 13Feb2019} With further literature search, group U1 size lead-acid batteries are rated 32 to 35 Ah.
Attached Images
File Type: jpg U1N1andB&Dcharger.jpg (248.5 KB, 141 views)
File Type: png U1BatteryCcurves.png (48.6 KB, 125 views)
File Type: png U1BatteryAt0.4C.png (44.7 KB, 120 views)
File Type: png U1N1onB&Dcharger.png (31.3 KB, 121 views)
File Type: png U1BatteryAt0.05C.png (67.0 KB, 125 views)
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Last edited by bistander; 02-13-2019 at 08:53 PM.
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