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Home Forums Technical Discussion Battery question, need advice

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  • #63524
    WrethaOffGrid
    Participant

    I am seriously considering changing over from marine type deep cycle batteries to the 6V genuine golf cart batteries (wired together to make 12V), I need some advice, I have been using Interstate marine deep cycle (which I know isn’t a true deep cycle) and it says it is 125 amp hours, 210 reserve, it’s the SRM29, right now I’m surviving on ONE battery, we usually run two of them, prefer running four but finances preclude that from happening now.

    I am looking at the Energizer CG2, the specs are

    • 6 volt
    • Minutes at 75 AMPS: 107
    • 20 AMP Hour Capacity: 208

    I hate numbers and math, what I do know is right now I can afford to get 2 of these, perhaps 4, how is that going to compare to the 125 amp hours on the battery I’m running now?

    My system is small, I’m running a few lights (some CFL and some LED), a 12 volt water pump, a couple of laptops (usually only one at a time), a small radio and a freezer to fridge conversion (doesn’t take much juice to run), my inverter is 1000 watts and tops out at 9 amps, it rarely goes up that high, it shoots up when the fridge first comes on, then levels out for the 5 or so minutes it’s running, that’s my biggest power drain.

    https://www.samsclub.com/sams/energizer-golf-cart-battery-group-size-gc2/prod6750008.ip?navAction=

    https://www.interstatebatteries.com/cs_eStore/Content.aspx?dsNav=Ntk~SearchGroup (scroll down to the SRM29 to get the specs)

    Thanks everyone

    Wretha

     

    #68144
    WrethaOffGrid
    Participant

    I have found several references that say these batteries are 225 amp hours each, of course that is what someone is saying, I still can’t find any official reference saying that, but if this is the case, I will definitely get at least 2 of these, they run around $85 each not counting the core charge, I’ll call Sam’s and find out what they charge for that and if they will take an automotive battery in trade, they have done that before when they used to carry the marine-deep cycle batteries that I purchased many years ago…

     

    Wretha

    #68145
    12vman
    Participant

    Figure most 6 volt golf cart batteries at ~200 aHr. Connecting them in series doubles the voltage but the aHr. rating remains the same as one. 2 connected in series will give you 12 v.d.c. with an aHr. rating  ~200. Usable aHr. level would be ~50. (Figuring a 25% “Safe” discharge rating)

    Never discharge a battery any less than 20-25% of its highest rating or it will shorten the life considerably. Never let the voltage drop below 11.9 volts unloaded. (Nothing drawing on it for 1/2 hour before testing)

    #68146
    WrethaOffGrid
    Participant

    Thanks 12vman, I was hoping to get your input on this…  now I have to decide whether to get 2 or go ahead and get 4, I’m really leaning toward getting 4, they will not get any cheaper and with the economy going the way it is, I suspect they would go up in price rather than down…

    I just called Sam’s and they told me the core charge would be $15 each, my internet phone flaked out on me before I could find out if they require a like battery or if they would take any other kind such as an automotive battery or 12 volt deep cycle battery.

    Now to go through my papers for my charge controller, I need to find the charge setting for these batteries, it’s been a few years since I had to change that setting. :)

    Wretha

    #68147
    12vman
    Participant

    I’d go with 4. That would give you ~100 aHr. of usable reserve..

    They usually don’t care much on what type of core that you take to them. Just as long as its one for one and about the same size. It has more to do with recycling..

    I would set the bulk charge voltage at ~14.2/14.4 volts and the float at ~13.2/13.4 volts. This is where I have my settings now. (I have 8-Rolls Surrette S-600’s) When I had 4-6 volt golf cart batteries. I carefully watched the voltage and never let them go below 11.9 volts and I got 8 yrs. usage out of them. I didn’t change the settings on my controller when I changed the batteries out..

    #68148
    WrethaOffGrid
    Participant

    In the past Sam’s Club took an automotive battery for the core when I purchased a marine/deep cycle battery…. but when I went to the Interstate store, I bought the same marine/deep cycle batteries, I had a couple of automotive batteries (not small ones either), they only gave me partial credit for the core charge, they acted put out that I didn’t bring in the same size/type of battery.

    I expect Sam’s will do the same as they did before, I’ll call before heading out (it’s a 3 hour drive one way) just to make sure, I don’t want to load them up and lug them across Texas if they will not take them… if they will take an automotive battery for the core great, if they don’t, I’m willing to put out the $100 plus tax for each battery, I will get 4 of them.

    My next investment/replacement item is going to be an inverter, I have one that may be going south on me, it’s 7 years old and used on a daily basis, I bought 2 of them before moving out here, I have taken them apart and cleaned them out many times over the years, I’ve also replaced the fans in them, they have been good and reliable all this time. The one I think is going out, randomly shuts the power off for a few seconds, the red fault light comes on while this is happening, it doesn’t matter what is running or not, I’ve seen it happen when NOTHING was plugged up to it. It doesn’t do it all the time, sometimes it’s several times a day, sometimes it goes days without happening, I can’t seem to find a pattern.

    I am going to crack it open again, blow the dust out of it, then swap it out with the one that has had less use. I am hoping to get another few years out of it, but if necessary I’ll buy another one.

    Wretha

    #68149
    WrethaOffGrid
    Participant

    Thanks 12vman for the advice on the charge controller setting, I’ll definitely keep that in mind…. are you the one who sets the voltage a bit high to purposely boil the batteries a tiny bit to prevent stratification? I remember reading about someone here doing that, I’m too lazy right now to look it up :)

    Wretha

    #68150
    12vman
    Participant

    If you allow your battery to get to 14.2/14.4 volts on the bulk charge, it will boil them enough to keep them mixed up. My controller (C-40) holds this voltage an hour (Bulk) and then drops down to 13.6/13.8 volts (Float) and hold there for the rest of the day. (On a typical “good” day) Some days doesn’t have enough sun to get them up to the bulk voltage level and hold them there for an hour but the voltage always seems to creep above the 13.4/13.6 volt level and they still boil a little.. (Bubble now and then)

    If you allow the voltage to go much above 14.4 volts, they boil too much and dry out much faster. Boiling too much also makes a mess on the tops of the batteries! It’s not necessary to boil the crap out of them..

    The settings that I suggest works well for me and has for years. Just so it’s understood, I have my battery in a climate controlled environment, in my living area, with me! I know if they are too cold or too hot. Temperature does make a difference in the settings. A warm battery boils easier than a cold battery. If you have your battery in a shed outdoors or in a cold basement, my suggestions are wrong. Just an FYI..

    Wretha, this may apply to your inverter issue..

    I was working with a fella that had the same issue. During a charge period, his inverter would shut down for an hour or so and then normalize. (Battery mounted in a non-heated area) I walked him through the bulk/float settings several times, keeping the bulk setting below the max. input voltage limit of his inverter, to no avail. He would check the voltage at the battery during float time and sure enough, the voltage was going above the physical/adjustable setting in the controller! (Too high for the inverter to accept) One thing that he didn’t tell me.. He was using the temperature compensation thermistors at the battery! This bypasses the adjustable setting in the controller and allows the bulk to go to the maximum setting to a cold battery! Needless to say, we unplugged the thermistors and all is well BUT the battery will not achieve a complete, full charge, being they are cold and a cold battery needs a higher voltage to charge completely. The controller was just doing what it was designed to do..

    When your inverter is failing, check the battery voltage at the inverter and see if its higher than the maximum input voltage limit of the inverter.. (Or very near)

     

    #68151
    WrethaOffGrid
    Participant

    Again 12vman, your wisdom and input are very appreciated, I also keep my batteries, charge controller and inverter inside my living quarters, the only part that is outside are the solar panels, I didn’t consider the temps, just the fact that I wanted to know what was going on with my system at all times, I didn’t want things out of sight (out of mind), it keeps me in the loop and stops potential problems much quicker. I don’t worry about the “dangers” of having the batteries and such inside, the sky castle is not tight, and our batteries are kept in such a way that if there was a leak, the liquid would be contained, they are also kept away from flame or anything that could spark. Now for what it’s worth, we don’t try terribly hard to keep the sky castle warm in the winter, we keep things well above freezing though, the nights might get down into the 40s F and the days usually get into the 50-60 F range.

    I didn’t know what a thermistor was so I looked it up, I can assure you we have no such device on our system. My charge controller is a C35. As far as the inverter is concerned, for now I have no idea what is causing it to do that, randomly going off, I will say that it has only done this during this last winter, it has never done it before, it seems to only happen during the day when things are charging or fully charged, I don’t ever recall it happening at night, one strange time it almost always happened (again only during the day) was when the fridge would shut OFF (not coming on) the inverter would shut off for 5-10 seconds then come back on, don’t know if that would give you a hint about something or not…

    This doesn’t happen everyday, I’d say maybe a few days a week, and it would only shut off for 5-10 seconds then come right back on, it happens when things are running, or when nothing is on.

    About a week ago, our fridge smoked on us and quit working, it was used when we got it so it could be that it was its time to die, or it could be the inverter had something to do with it. I have another fridge lined up to replace it, but I don’t want to plug it up until I find out more about what is going on, I plan on breaking down both of my inverters, cleaning them well, then I will swap the two, putting the (hopefully) good one on my main system.

    I’m in no hurry though, I hope to get to Sam’s in the next couple of weeks (it’s a 3 hour drive) to get those batteries, that’s when I’ll take everything inside the sky castle apart and re-do everything.

    I did attach a gadget to my batteries, it’s one of those desulfators, sometime after that is when my inverter started acting up, I thought it might be caused by the desulfator but when I disconnected it, the inverter continued acting up, you can read about it herehttps://offgriddev.wpengine.com/2014/02/01/battery-desulfator-review-part/
    I don’t believe the desulfator hurt anything, I had another one hooked up to my secondary setup on the back deck and it didn’t happen out there, I also swapped desulfators and the same thing happened inside. I do not have the desulfator hooked up on my inside system, but still have the one working outside.

    Wretha

    #68152
    WrethaOffGrid
    Participant

    After re-reading your post 12vman, one thing that jumped out at me, the inverter getting too much voltage during charging, on my setup, I have never been able to equalize my batteries using my C35 while my inverter was on, the inverter would go into fault mode, the red light coming on and no power coming out, I would have to shut everything off and stay around to watch things for the time it took to equalize, so honestly I didn’t do it very often… I just assumed that was normal.

     

    Wretha

    #68154
    12vman
    Participant

    I don’t ever recall it happening at night, one strange time it almost always happened (again only during the day) was when the fridge would shut OFF (not coming on) the inverter would shut off for 5-10 seconds then come back on, don’t know if that would give you a hint about something or not…

    Sounds like when the load leaves the inverter, it allows the battery voltage to rise above the inverter input threshold voltage before the controller can correct it down to the bulk voltage level. The inverter sees the voltage correction of the controller and resumes to normal..

    When the load is on the battery from the inverter, the controller is letting all of the current from the panels pass through unrestricted to assist the battery to supply the inverter. When the load is removed, the voltage can spike for a few nanoseconds until the controller responds and brings it back down to the adjusted bulk level. The inverter sees this spike and does what it’s designed to do..  Shut down if the input voltage goes too high..

    Worn out batteries will allow this to happen, being the internal resistance of the battery is higher (less resistance) and it would be easier for the panels to push the voltage up. If the battery provided a better load to the controller, the voltage spike wouldn’t be so extreme..

    I’d venture to say that your batteries are weak and you have the bulk voltage setting on the controller too near the input voltage threshold of the inverter..

    #68155
    WrethaOffGrid
    Participant

    Yes, the last 2 batteries on my bank are worn out which is why I am about to buy new batteries, I decided I was tired of putting the money into the cheaper marine deep cycle batteries only to have them not last as long as they should, I am hard on my batteries, but with the 4-6 volt golf cart batteries, these should last me a lot longer.

    What you explained, 12voltman, makes sense. I am working on getting to Sam’s soon to get those new batteries, when I have them, then I’ll tweak the settings on my charge controller, I’ll allow the batteries to fully charge, then I’ll hook up the freezer-fridge conversion, I don’t want to run the risk of frying another fridge (if that is what fried it). For now, I only have a few lights and my laptop to run, even on the worn out batteries I can go deep into the night.

    Wretha

    #68156
    12vman
    Participant

    When you equalize, this bypasses the bulk setting and allows the voltage to go to the highest point of the controller, (uncontrolled) which can be near 15 volts! It will set at this level for an hour or two and return to the float setting..

    You must be careful when you equalize. Things can fry with the voltage being this high! You’re suggested to disconnect all loads and just let the controller work the battery alone..

    #68157
    WrethaOffGrid
    Participant

    I just found out that a neighbor has some 2V batteries he wants to part with, I’m trying to get more info, like how many and such, this guy is running a 24 volt big boy system, he has regular household stuff he’s running…

    Wretha

    #68158
    12vman
    Participant

    My first concern on those batteries would be.. “How old are they?”

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