3.6L ESS Battery Basic Load Testing

Jebiruph

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Checking the voltage of the batteries is a good start, but a battery with good voltage can still fail when under a load. To really test the batteries, you need a load tester. Some auto parts stores will load test your battery for you, but having dual batteries complicates the testing. To do my own testing, I found a cheap load tester online for less than $25. Harbor Freight has them too (plus free voltmeter with coupon). These cheap load testers are basically a heating element (uses a lot of power) shielded in a metal box with a voltmeter built in. It's not a sophisticated load test, but it's better than nothing.

The testing is basically the same as testing voltage. The difference is after everything is hooked up, you press a button to turn on the tester and place a load on the battery. If the voltage of the batter drops too low under load, it's a bad battery. The tester should only be turned on briefly, just long enough to read the voltage. This first picture shows the tester heating up when left on too long. It will melt plastic, so be careful. Mine turned the magazine it's sitting on brown from the heat.
load test heat.jpg


To test, I disconnected the main battery positive terminal to isolate the batteries and used a digitalt meter to read voltage (instead of the meter on the load tester). Here's testing the Main battery with the tester connected to the positive post and the negative terminal. Normal voltage was 12.68v, loaded test voltage was 11.33v.
load test main.jpg


Here's testing the Aux battery with the tester connected to the disconnected positive terminal and the negative terminal. Normal voltage was 12.41v, loaded test voltage was 10.59v.
load test aux.jpg


The meter on the tester indicates the good/bad voltage ranges. Both the 650 amp Main and 200 amp Aux batteries passed the load test.
load meter.jpg


(updated 04/13/2019)
Additional 3.6L ESS system information is available here.
3.6L ESS Dual Battery Consolidated Information
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.2





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Jebiruph

Jebiruph

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  • Thread starter
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First, thanks for posting on the loneliest thread on the site. :)

The load tester I used was 100A and I think that would be good enough and can be safely used on smaller batteries. Mine is a Schumacher BT-100 100 Amp Battery Load Tester. It's no longer available on Amazon, so I can't post a link.
 

demisx

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These were my results on 2021 JLUR 3.6L/manual with dual battery/ESS. Looks like both batteries (2.5 months old) are still pretty good. Thank you for such a valuable post.

On a side note, this forum should add "bounty" or "beer money" feature. I'd love to leave a few bucks for those who make such valuable contributions to the Jeep community. I am sure there will be others too. 👍

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