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Thread: Battery load test

  1. #1
    Join Date
    Nov 2010
    Location
    Discovery Bay, CA
    Posts
    430

    Default Battery load test

    I am planning to do a battery load test in the coming week. While I was in the yard I was able to do a fairly controlled test of my flexible solar arrays and controller. They are working well.

    My plan is to disconnect the SAs and turn on some stuff so I achieve a 5 amp draw per my Zantrex power monitor. I am going to keep a chart like the one Bob M. recommended. I'll document voltage to two decimal places at full charge and then hourly to 50% charge. I'll determine 50% by battery voltage as opposed to what the Zantrex is telling me. I have a pretty high quality multimeter aboard so I also plan to confirm the Zantrex is reading battery voltage accurately. My multimeter has not been professionally calibrated but I don't think that's going to be an issue for this application.

    I am hoping the Zantrex is more or less accurate but Practical Sailor warned one might have considerably less capacity than one thinks, particularly as the batteries age. My 3 110AH AGMs are getting up there. It will be an interesting experiment.
    Last edited by mike cunningham; 04-26-2018 at 06:47 PM.

  2. #2
    Join Date
    Nov 2010
    Location
    Discovery Bay, CA
    Posts
    430

    Default

    Quote Originally Posted by mike cunningham View Post
    I am planning to do a battery load test in the coming week. While I was in the yard I was able to do a fairly controlled test of my flexible solar arrays and controller. They are working well.

    My plan is to disconnect the SAs and turn on some stuff so I achieve a 5 amp draw per my Zantrex power monitor. I am going to keep a chart like the one Bob M. recommended. I'll document voltage to two decimal places at full charge and then hourly to 50% charge. I'll determine 50% by battery voltage as opposed to what the Zantrex is telling me. I have a pretty high quality multimeter aboard so I also plan to confirm the Zantrex is reading battery voltage accurately. My multimeter has not been professionally calibrated but I don't think that's going to be an issue for this application.

    I am hoping the Zantrex is more or less accurate but Practical Sailor warned one might have considerably less capacity than one thinks, particularly as the batteries age. My 3 110AH AGMs are getting up there. It will be an interesting experiment.
    I completed this Test day before yesterday. Very interesting, based upon battery voltage vs SOC, the Zantrex is right on with regard to SOC percentage and appears to be reporting battery condition accurately. What is also good news is my 11 year old AGMs continue to maintain nearly their entire capacity of 110 AH per battery based upon AH consumption/time/battery voltage. I think their longevity is due to their environment (never get outside 65 to 80 degrees F) and the fact that I never cycle below 60 % SOC. During the 16 SHTP I would begin charging in the mid 60% range and go until I had them up to the high 80s%. They maintained a full charge exclusively on SAs when at anchor and in Nawiliwili.

    Having said all the above, I did spend $70 on a 18 AH Li battery as an emergency backup. This will be useful ashore as well as afloat.

  3. #3
    Join Date
    Oct 2007
    Posts
    179

    Default

    What and where did you find the 18AH Li battery?
    Quote Originally Posted by mike cunningham View Post
    I completed this Test day before yesterday. Very interesting, based upon battery voltage vs SOC, the Zantrex is right on with regard to SOC percentage and appears to be reporting battery condition accurately. What is also good news is my 11 year old AGMs continue to maintain nearly their entire capacity of 110 AH per battery based upon AH consumption/time/battery voltage. I think their longevity is due to their environment (never get outside 65 to 80 degrees F) and the fact that I never cycle below 60 % SOC. During the 16 SHTP I would begin charging in the mid 60% range and go until I had them up to the high 80s%. They maintained a full charge exclusively on SAs when at anchor and in Nawiliwili.

    Having said all the above, I did spend $70 on a 18 AH Li battery as an emergency backup. This will be useful ashore as well as afloat.

  4. #4
    Join Date
    Nov 2010
    Location
    Discovery Bay, CA
    Posts
    430

    Default

    On Amazon it's called Beat it. Someone else on the board suggested it. Fantastic, powerful, compact unit.

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