Capacity Testing Methods?

[Maine Sail]

Originally Posted by smac999

that thing looks sweet. now to convince my boss to pony up


do you normally test single 6v batteries or in pairs at 12v?

If they are used in series for 12V I test them at 12V. A series parallel bank of say four 6V batteries gets two tests, one for each series pair.. On really large cells for 24V etc. I will often test individual cells..

[shaneinseattle]

Thank you everybody -- especially Maine Sail -- who carried this thread. The input prevented me from buying, and quickly smoking, a $50 load tester in an inappropriate application. Every dollar counts...

[Cap Erict3]

Originally Posted by shaneinseattle

I've done a fair amount of research and cannot come up with anything firm on how to do this capacity test for my battery bank.

My 12V 540 Ah bank consists of six 6V 180 Ah Gel-Tech batteries and they are over 6 years old but lightly used and on charging almost all the time.

I haven't yet purchased load testers or anything of that nature; want to make sure I get the right equipment. Not sure if I test each battery separately, or can test the bank all at once. Can I test to 50% discharge or must I test to 100% DoD? The questions go on and on...

Any comments from technically astute people that know how to design a test for this size and makeup of battery bank would be MUCH appreciated!

Thanks,

Shane

I worked for a major corporation that spent millions every year replacing ups batteries. I was part of a team tasked to provide recommendations on battery replacement. After months of research the best recommendation was that load testing to predict failure was unreliable. For mission critical batteries swap out at 50% of the projected life. Redundant systems that are not critical but well monitored can be used till 95% PL with minimal failures

[smac999]

any updates to this thread?

is the Array 3721A 40A still a good device or are their better ones now? I would like to be able to print out results either table or graph? of volts / amps / ah. the serial port seems a little old school

[wsmurdoch]

I have a West Mountain Radio Computerized Battery Analyzer (CBA IV) West Mountain Radio - CBA IV - Computerized Battery Analyzer and have used it to test my flooded lead acid batteries. I wrote a little about it in another thread https://www.cruisersforum.com/forums...ml#post3203978 . It connects to a PC via USB and the battery to be tested by cables. It produces a discharge curve for the battery as a graph along with other things. I'm happy with it. It is much better than the two homebrew devices that I had previously made and used.

Bill

[Lake-Effect]

I bought one of these inexpensive units this spring. It gives a "SOH" (state of health) reading which is analogous to capacity. I've tried it on some newish batteries as well as older boat batteries.... seems to do the job. I have yet to compare it to better-quality battery analyzers.

[CharlieJ]

@Lake-Effect #21:
The unit you reference is a knockoff of a Midtronics conductance tester. I have owned a Midtronics for about 12 years and regularly use it but take the results with a grain of salt.

As MaineSail points out up thread, conductance testers are not very accurate for AGM batteries. Here are some more of their shortcomings:
1. Only test for cranking amps: the tech has to infer the health of a house battery bank's SOH.
2. Totally inaccurate for thin plate pure lead (TPPL) batteries; e.g., Northstar.
3. Totally inaccurate for any of the lithium chemistries.
4. They are accurate for determining SOH of FLA starting batteries.

[Lake-Effect]

Originally Posted by CharlieJ

@Lake-Effect #21:
The unit you reference is a knockoff of a Midtronics conductance tester. I have owned a Midtronics for about 12 years and regularly use it but take the results with a grain of salt.

As MaineSail points out up thread, conductance testers are not very accurate for AGM batteries. Here are some more of their shortcomings:
1. Only test for cranking amps: the tech has to infer the health of a house battery bank's SOH.
2. Totally inaccurate for thin plate pure lead (TPPL) batteries; e.g., Northstar.
3. Totally inaccurate for any of the lithium chemistries.
4. They are accurate for determining SOH of FLA starting batteries.

Thanks Charlie. I appreciate the voice of experience.

Is there a newer instrument or technology that does a better job with house batteries and AGMs? Especially with regards to capacity or remaining "life" of house batteries?

That West Mtn Radio battery analyzer looks quite powerful, but maybe a bit cumbersome in the field.

[Maine Sail]

Originally Posted by CharlieJ

As MaineSail points out up thread, conductance testers are not very accurate for AGM batteries. Here are some more of their shortcomings:
1. Only test for cranking amps: the tech has to infer the health of a house battery bank's SOH.
2. Totally inaccurate for thin plate pure lead (TPPL) batteries; e.g., Northstar.
3. Totally inaccurate for any of the lithium chemistries.
4. They are accurate for determining SOH of FLA starting batteries.

This goes into a bit more depth on the subject:

https://marinehowto.com/are-battery-conductance-testers-worth-it/






.

[Lake-Effect]

Originally Posted by Maine Sail

This goes into a bit more depth on the subject:

https://marinehowto.com/are-battery-conductance-testers-worth-it/.

Very interesting. Thanks very much for undertaking such useful research and sharing the results.

My takeaways at this point:

• Instruments like the Midtronics and its imitators are mainly for testing the cranking ability of starter batteries (... logical since there are way more car batteries out there ) and they will not provide reliable measurement of capacity or SOH of deep-cycle batteries.
• The most reliable test of battery capacity is the 20-hour discharge test
• You don't get much of a tester for $40

I can totally see that the effort and expense of 20-hour testing is justified for serious long-term and offshore cruising. But for the weekenders, occasional coastal cruisers, fishing boats ... what would be a simple yet reasonable way for owners to assess the health of their house batteries?