Lifeline battery capacity test

[CarlF]

I'm checking my four year old Lifeline batteries by doing a 25 amp constant discharge. The Lifeline spec is 348 minutes to 10.5v.

I've never done this before. Am I supposed to discharge to 10.5v with the 25 amp load attached or 10.5v with no load?

Thanks

[smac999]

With load.

Normally a c20 test is done. To Check ah. Looks like you are doing it based on rc rating? I guess that works too.

[CSY Man]

You are probably doing permanent damage to the battery if you take it down to 10.5 volts.
I would not....

I get 5 years or so out of deep cycle batteries and once even 6 years, but that was the end.

[john61ct]

Search for 20 hour capacity test here

http://www.pbase.com/mainecruising/p...attery_monitor

Better yet read it all, and check out the rest of the site.

No harm at all in going down to 10.5V long as it's all precisely controlled and recharged immediately.

If you want can devise your own easier benchmark, but need to run it at commissioning time to compare later.

[Maine Sail]

Originally Posted by CSY Man

You are probably doing permanent damage to the battery if you take it down to 10.5 volts.
I would not....

I get 5 years or so out of deep cycle batteries and once even 6 years, but that was the end.

I test many hundreds of batteries each year and one thing I have learned is that the batteries tend to perform better, and very often deliver more capacity, after a capacity test to 10.5V. Doing a proper test includes an immediate recharged right after hitting 10.5V.

Previously blocked/clogged/closed pathways through the cell infrastructure tend to get re-opened and become usable pathways again. It's not uncommon for me to see gains of 3% to over 20% following two or more capacity tests or deep discharges to 11V and back to 100% followed by a 10.5V 20 hour test..

Sure if you take it to 10.5V and leave it there for a while this is not good but hitting 10.5V under load and then immediately beginning the recharge is going to do less damage than the continual 50% to 80% most boaters think nothing of.

[Maine Sail]

Originally Posted by CarlF

I'm checking my four year old Lifeline batteries by doing a 25 amp constant discharge. The Lifeline spec is 348 minutes to 10.5v.

I've never done this before. Am I supposed to discharge to 10.5v with the 25 amp load attached or 10.5v with no load?

Thanks

Carl,

You may be disappointed in the test results using a RC test on used batteries. An RC test would be much easier, as it is a shorter duration, but as the batteries age they tend to diverge between a 20 hour rate test and a 25A rate test with them performing worse under a high rate then a low discharge rate.

If the batteries are used for a windlass or thruster then a 25A test is a better predictor, but if they are house bank the 20 hour test is going to give you a much more realistic picture of your banks usable capacity.

This may sound counter-intuitive but before you test them you may want to run a few back to back deep cycles to open them up a bit. Take them down to 11.2V to 11.5V under a 20 hour load then immediately recharge to 100% then repeat again the next day. Do this a few times, then run a 4 +/- hour EQ at 15.5V temp compensated (Lifeline AGM's only), and when you finally run the capacity test you'll have a better picture of the actual condition. After the capacity test 100% recharge, follow it up with a few more hours at 15.5V and you're done.

[CSY Man]

Originally Posted by Maine Sail

I test many hundreds of batteries each year and one thing I have learned is that the batteries tend to perform better, and very often deliver more capacity, after a capacity test to 10.5V. Doing a proper test includes an immediate recharged right after hitting 10.5V.

Previously blocked/clogged/closed pathways through the cell infrastructure tend to get re-opened and become usable pathways again. It's not uncommon for me to see gains of 3% to over 20% following two or more capacity tests or deep discharges to 11V and back to 100% followed by a 10.5V 20 hour test..

Sure if you take it to 10.5V and leave it there for a while this is not good but hitting 10.5V under load and then immediately beginning the recharge is going to do less damage than the continual 50% to 80% most boaters think nothing of.

Cool, learn something every day.