Fallacy of testing batteries under light charge?

softdown
softdown Solar Expert Posts: 3,915 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Some of you may recall that I did not scrap my old 8D's - eight of them since one was replaced under warranty. They still powered my house but were replaced for two reasons:
1) Tired of replacing a battery every few months - with the resulting power outage because another cell went bad. Almost always the cell next to the negative post by the way.
2) The excellent Fullrivers sat for two years before I got a steal of a price on them. Then they sat here for almost another year. Figured - may as well use them.  

Keep waiting for the 8D's to expire and they just don't. They do help carry the load - I disconnected the group of four and the overnight voltage sank as a result. Wish I could remember how much.

Got a nice battery tester which is just awesome for testing automotive batteries. Perhaps all batteries up to 220 Ah or 2000 CCA. It says that all four of my 8Ds are still good. All still around 1000 CCA or better - there were 1400 when new. But the batteries were receiving a light cloudy day charge from the panels. Putting the ebay link here because their price is best there and listed by apparent manufacturer. https://www.ebay.com/itm/12V-Car-Battery-Tester-Charger-Portable-Auto-Maintainer-100-2000-CCA-Ancel-BA101/152286369381?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

It doesn't seem right to scrap batteries that still offer 1000 CCA. I have another four sitting around that must be charged periodically. Sometimes I consider hooking them up as well. That would very likely extend the life of my valuable Fullriver batteries.

The purists here, thinking Photowit in particular, will protest of course. Because thats what purists do. But the Fullrivers with two years of use test out as comparable to the unused and stored Fullrivers. It is not hurting the Fullrivers at all.

Still have the cables from when eight 8D's powered my house. Would be so easy to hook up the other four sitting in storage. I like to see the battery bank still showing over 50 volts in the morning. So - why not? 
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #2
    As suspected, checking batteries under charge has a couple problems. Mostly that they are able to borrow power from other batteries. 
    Just got this battery checker and learning the ropes.

    With the charging cable disconnected,  one old battery (2011) yielded these inferior results:
    29% healthy
    862 CCA
    3.54 resistance

    Not really terrible but think I'll replace while feeling like it - with cold, dark days rapidly approaching. 
    Been tempted to swap out this battery for 1/2 year now. Voltage and SG issues of course. But I currently prefer the numbers this tester yields.

    I've checked saltwater SG thousands of times. It isn't quite the holy grail that some believe - in my experience. Testing equipment etc...
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    edited September 2019 #3
    Further work reveals that the quality of the connections has a lot to do with test results. After removing "Walmarts Best" - the "marine rated" connectors, that battery tested out much stronger. Seen that more than once this morning.

    If I planned to rely on the 8D's I would certainly replace "Walmarts Best" with some professional grade connectors. EDIT - it is also entirely possible that the connection between the battery connections and the test equipment significantly effected the results.

    I would also seek to avoid regular ~3/4" battery posts in solar applications. I think that is pretty important. 

    To be fair, I could have done better maintaining the connections. I didn't know the felt washers are actually very functional. Plus I never succeeded in protecting the connections with a suitable sealant. Vaseline did not work well. I just periodically scrubbed any "dirty" connections after spraying with battery terminal cleaner - which is a lot better than nothing, 

    Also - a battery acid crystal in the eye may cause concern for a couple seconds before the natural wetness dilutes it. I was about 1/4 second from flushing before the discomfort went away. Lost my vision a short time later though. A coincidence in all likelihood. j/k
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    There used to be a good link to a very good battery FAQ sticky on this forum, that details the pitfalls of deepcycle of grid batteries, including surface voltage, SG, charge and discharge current and voltages, EQ regimen, and perhaps most importantly...safety.

     IMHO the fact that you got an acid crystal in your eye should serve as a warning to all!  Batteries can be very dangerous, and the can (and have blinded people.  They also explode if not being serviced with care!  Don’t ask me how I know!  

    Tony

    PS. I did a search but couldn’t find the above mentioned FAQ post/thread. Perhaps someone has it stashed and can repost it?


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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #5
    icarus said:
    There used to be a good link to a very good battery FAQ sticky on this forum, that details the pitfalls of deepcycle of grid batteries, including surface voltage, SG, charge and discharge current and voltages, EQ regimen, and perhaps most importantly...safety.

     IMHO the fact that you got an acid crystal in your eye should serve as a warning to all!  Batteries can be very dangerous, and the can (and have blinded people.  They also explode if not being serviced with care!  Don’t ask me how I know!  

    Tony

    PS. I did a search but couldn’t find the above mentioned FAQ post/thread. Perhaps someone has it stashed and can repost it?


    Seems to be missing word?
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #6
    I have eight 8D's that have about 1000 CCA or much better, one is unused. If I hooked up all eight while carefully installing brass battery terminals - I would bet that would add a few years to my very expensive Fullriver battery lives. Light usage of the 8D's is no harder on them than "cold storage" with periodic charges. 

    Not for the purist - I don't care. Photowit can eat a Klondike.  The resistance values are pretty similar  - a bit surprising. My automotive battery tester seems a bit confused about the Fullrivers. The tester is mostly designed for CCA and automotive batteries I think. Though it readily offers the option of Ah ratings. In fact, that is the default measurement on the "fast test". The Fullrivers simply were not made to deliver high CCA values. High CCA values are delivered via a lot of thin plates. Solar batteries have thick plates. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #7
    It would costs me $50 to add four 8Ds while employing brass battery terminals on all eight. Since using the current 8Ds with the Fullrivers has not done any measurable harm in 2 years and 2 months - why not? A small risk? Sure. I'm fine with small risks. Nothing ventured - nothing gained. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #8
    Those who did not speak - forever hold your peace. Installation of four more 8Ds is 75% complete. Figured I better move them while I still can. Doing endurance training which usually equates to losing weight and heavy lifting capabilities. Batteries are not getting lighter. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,622 admin
    edited September 2019 #9
    The three page Forum FAQ is here:
    And here are three good FAQs for Batteries (originally supplied by Tony/Icarus -- 10 Years ago!):
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #10
    Thanks Bill, 

    These ought to be a MUST read for every battery based user.  

    T
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