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Thread: Learjet's dodgy 12V solar installation

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    An even more impressive set up.

    Are you still using the same old car batteries as the original setup Learjet, or have these been replaced over time?



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    Quote Originally Posted by peteramjet View Post
    An even more impressive set up.

    Are you still using the same old car batteries as the original setup Learjet, or have these been replaced over time?
    Never used car batteries. The original were ex UPS batteries from a mate that had a computer store. After that went to 12V deep cycle AGM, which I still have but they need replacing as they are tired. I would like to go to series 2V cells as I've heard better things about them longevity wise.

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    It's a very impressive setup Learjet, and shows what can be done with a little thought, imagination and of course, expertise.

    I have enjoyed reading of your progress from the project's inception almost seven years ago.

    Thanks for this latest update.

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    Thanks Tristen. A pity the early pics are missing, I guess lost in server changes etc.

    I have a mate getting in some 250 watt panels, also ex grid install so might get another kW for good measure and make a ground mount for them. The tomatoes could do with some shade this time of year.

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    I though the AGM batteries were ex-4WD? Must have crossed threads somewhere - either way it's impressive they are still going.

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    Quote Originally Posted by peteramjet View Post
    I though the AGM batteries were ex-4WD? Must have crossed threads somewhere - either way it's impressive they are still going.
    Nah mate, the first lot (AGM deep cycle ex UPS) lasted 2 years and died. They were already a couple of years old. I got a second lot that seemed tired from the start. I'm on my third set now and they are getting tired. Really not getting much life out of them at all. I don't discharge deeply so I'm starting to suspect the regulators I used with them were crap. One of the batteries was getting warm. It didn't like the constant charge at 14.3V and is happier with 13.7V. With the new regulators I can configure most parameters so I'll play around and see how they fare.

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    Quote Originally Posted by Learjet View Post
    I would like to go to series 2V cells as I've heard better things about them longevity wise.
    Yeah, I got 16 years out of last set of 6 x 2 V cells (large format vented lead acid), even then it was only 1 cell that gave up, the rest were still good, but too old to bother with trying to match another cell to.

    My latest set of 6 x 2 V cells are BAE SLA's & at the cycle depth I use them at they should do 16 - 20 years I hope.

    The good thing about the 2 Volt string is you can individually check cell voltage & equalise charge when necessary or even separately charge the individual low cell to catch up with the others.


    Quote Originally Posted by Learjet View Post
    Nah mate, the first lot (AGM deep cycle ex UPS) lasted 2 years and died. They were already a couple of years old. I got a second lot that seemed tired from the start. I'm on my third set now and they are getting tired. Really not getting much life out of them at all. I don't discharge deeply so I'm starting to suspect the regulators I used with them were crap. One of the batteries was getting warm. It didn't like the constant charge at 14.3V and is happier with 13.7V. With the new regulators I can configure most parameters so I'll play around and see how they fare.
    You're on the right track, any of the sealed technology lead acid cells don't like to be kept at 2.383 V/cell (14.3 V). Recommended for my BAE SLA's is to charge to between 2.3 & 2.4 V/cell after a discharge cycle only, depending on depth of discharge, then drop straight back to float at 2.25 V/cell (13.5 V)
    For shallow cycling & non cyclic operation they recommend just using the float voltage of 2.25 V/cell (13.5 V).

    Hope that helps.
    Cheers, Tiny
    "You can lead a person to knowledge, but you can't make them think? If you're not part of the solution, you're part of the problem.
    The information is out there; you just have to let it in."

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    Thanks Tiny. Since I only do a shallow discharge, I'll wind down the charge voltage to 13.5V and see if they last a bit longer.

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    Quote Originally Posted by Learjet View Post
    Thanks Tiny. Since I only do a shallow discharge, I'll wind down the charge voltage to 13.5V and see if they last a bit longer.
    When they say shallow they mean real shallow. So to be safe; if you do that you will also need to do a charge up to ~14.3 V about once a month to make sure you are getting a reasonable equalisation of your cells.

    I have my regulator set to do it automatically.
    Once a month it takes the bank to 14.3 to equalise, then drops back to 14.0 for an hour for absorption of the equalisation charge. Then it auto drops back to float at 13.5.
    Last edited by Tiny; 12-09-17 at 01:39 PM.
    Cheers, Tiny
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    Cool thanks. Yes I read they need a 14.3V equalisation charge. That get that briefly when there are clouds too as the regulator has a lag and the voltage can reach 14.5V briefly as the cloud pulls away.

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