AGM / GEL Battery Load Testing

[ZAR]

Good Day,
Please if somebody could help me with this?

How do I effectively test a AGM / GEL battery to determine if it is bad or not?
I Want to be able to verify the rated Ah on it by conducting some kind of load test, what will the formula be for this this?
And also is there a battery tester available on the market for this kind of measurements?

Thank you in advance.

 

[snoobler]

Most batteries have a "reserve capacity".

This is the number of minutes the battery will deliver 25A above 10.5V.

Apply a 300W load and record the number of minutes until 10.5V is reached.

Compare that to the rated Reserve Capacity, e.g., if the reserve capacity is 180 minutes, and you get 160, the battery has 160/180 = 88.9% of its rated capacity.

 

[ZAR]

Thank you!

 

[Jim Burrow]

Most batteries have a "reserve capacity".

This is the number of minutes the battery will deliver 25A above 10.5V.

Apply a 300W load and record the number of minutes until 10.5V is reached.

Compare that to the rated Reserve Capacity, e.g., if the reserve capacity is 180 minutes, and you get 160, the battery has 160/180 = 88.9% of its rated capacity.

Hi Snoobler, I like your reply, but I have a question.

I'm 76 and have bought many, many batteries for my cars over the years and not from anyone bran. I've bought cheap batteries and expensive batteries and I have never seen a reserve capacity attached to them. The latest two batteries that I bought from Walmart, I even went online to research them and still never a reference to reserve capacity.

The question I have, where do you find this reserve Capacity you reference?

 

[snoobler]

Automotive batteries rarely have a reserve capacity listed since they're not designed for cyclic use. Walmart batteries are even less likely to divulge meaningful data.

Here's an example of meaningful specifications for comparably priced Interstate deep cycle batteries:

Marine Deep-Cycle Batteries | Interstate Batteries

Interstate’s SRM Deep Cycle batteries are the most popular line of marine batteries and offer strong, reliable power. This type of battery is used to start the motor power your trolling motor, and power your other accessories like fish-finders, whether your engine is running or not.

www.interstatebatteries.com

Being targeted for the deep cycle application, they also give the C20 capacity.

If one can't find a C20 or RC rating on a battery for a cyclic application, it shouldn't be used.

 

[Jim Burrow]

Automotive batteries rarely have a reserve capacity listed since they're not designed for cyclic use. Walmart batteries are even less likely to divulge meaningful data.

Here's an example of meaningful specifications for comparably priced Interstate deep cycle batteries:

Marine Deep-Cycle Batteries | Interstate Batteries

Interstate’s SRM Deep Cycle batteries are the most popular line of marine batteries and offer strong, reliable power. This type of battery is used to start the motor power your trolling motor, and power your other accessories like fish-finders, whether your engine is running or not.

www.interstatebatteries.com

Being targeted for the deep cycle application, they also give the C20 capacity.

If one can't find a C20 or RC rating on a battery for a cyclic application, it shouldn't be used.

thank you so much for the feedback. I had bought two Marine batteries from Walmart to use on my system until I could afford to put out $1600 per for 24v lithium batteries. that is still some time off, living on a fixed income.

To my disappointment (as at the time I didn't know about what you mentioned) all I can get out of these two batteries in series is 25ah with my 2424lv controlling the discharge with no solar or utility connects to the controller. The Controller turns off at 21 volts, but when the system is running normal and loss of the sun in the evening, the controller kicks in the Utility at 21.9 volts and continues until full charge and then float at 27-volts or if still in the dark, will kick off the Utility and the batteries once again supply the input power.

With respect to the batteries, I was hoping to get at least 50 or 60-ah per discharge, but no such luck.

 

[snoobler]

If they are the same group size, they should be close to the Interstate numbers. They're both made by Johnson Controls in Mexico.

This one?

http://watts247.com/manuals/mpp/PIP-LV%20110_120VAC/PIP-MS%20LV%201KVA%201-5KVA%20manual-20200318.pdf

What are settings 12 and 13?

Discharging your batteries to 21.9 will likely wear them out in 6-12 months.

 

[Jim Burrow]

These are only temporary batteries and not expecting to have them last forever. I sure hope in the next 6 months to have saved enough to buy the 24v lithium batteries for Big Batteries. I leave about a 4-hour drive from Big Batteries and I can pick them up in person and save on shipping cost.

I'm going down to 21.9 volts to get the batteries to supply power to the converter as long as possible for testing.

 

[snoobler]

What are settings 12 and 13?

 

[Jim Burrow]

What are settings 12 and 13?

Option 12 for this 2424lv is to Setting the voltage point back to utility source at 22.0 volts. Played with other settings.
Option 13 for this 2424lv is Setting the voltage point back to battery mode at 28.0 volts. played with "full" charge but like 28.0 better at this time in testing.

 

[snoobler]

IMHO, since you can't absorb or float, try 29.2V for #13. You're likely not getting the batteries charged much past 70%.

Check voltage drop between 2424's terminals and battery terminals. If you have even 0.2V drop, you're charging to even lower SoC.

Charge current should be set to 0.2C max. If those are group 24 batteries, assume about 80Ah, so they should only be charged at about 16A. If you charge them at a higher rate, they will hit termination voltage sooner and achieve lower states of charge.

Lastly, worth checking specific gravity if flooded to confirm end of charge SoC. 1.265 is a good number to confirm near 100% SoC.

 

[Jim Burrow]

Thanks for the tips. I sure will check all you recommend.