Load Tester

[tuberider]

I have one of those 100amp 12v and 6v load tester, with the analog gauge showing you the volts and good and bad areas. Well i have a 120ah gell 12v battery i want to load test. How long should i keep the load drawing to test the battery. I noticed the load tester says push the switch for ten seconds, but that doesn't tell you much. I left the load on for 15 seconds but i don't know if that's long enough.

[gspeak]

On mine, 10 seconds is plenty of time to get a reading. The instructions say NO MORE than 10 seconds.

[motion30]

I tried a tester like that on my 8d agm house battery .... set the tester on fire True story

[sartorst]

I burned my switch out testing longer than recommended so 10-15 seconds should be max!! sounds like you have a good battery if it did not fall into the red for ah rating
This type tester used to be stranded for testing battery's now the resistance type is what is used in most cases but are very expensive , but have seen battery's test good with the resistance type that were bad and failed with load type tester!!!!!

[sailinglegend]

Originally Posted by tuberider

I have one of those 100amp 12v and 6v load tester, with the analog gauge showing you the volts and good and bad areas.....................

These testers are for STARTER batteries that take a high current for a short time < 10 seconds. Deep cycle batteries are low currents for a long time, which is why it is difficult to get an accurate battery condition/capacity test, and why these testers are very expensive. I assume your Gel batteries are for your service bank?

[tuberider]

They are my house bank. Would one of those 500amp carbin pile testers make a difference. What tester are you talking about.

[sailinglegend]

Originally Posted by tuberider

They are my house bank. Would one of those 500amp carbin pile testers make a difference. What tester are you talking about.

You seem to have missed my point. You need a low current tester operating for a fixed time - this will measure the Ah taken out and the rate of the voltage drop and maybe with a whole load of other calculations with the in-built software they try and come up with a reliable result as to what the capacity of your battery actually is - which may be a lot less than what it says on the label. These testers cost 2-4000 $.

[Paul Elliott]

For what it's worth, I test my almost-1000A battery bank (4 8D AGMs) by switching on numerous high-load items and letting them run while monitoring the battery voltage during the process. I switch on the spreader lights, my few incandescent running lights, interior lights and fans, chartplotters, computer, etc, until my ammeter reads 25A or so. At 25A, it takes 20 hours to consume 500Ah, which is a good test of the battery condition, and a reasonable load for testing the house bank.

This doesn't give me a particularly accurate battery capacity number, but it does tell me if the battery is still in good health. I've had this set of AGMs for over ten years now and they are still going strong. Most of the time they are sitting idle with the solar panels keeping them topped up, but every so often they get a real workout on my Hawaii trips.