Probably need new batteries, best bang for the buck?

YostFMX
YostFMX Solar Expert Posts: 94 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have 4 Everlast 115 amp hr Walmart batteries that are 2 years old now, they dont hold out thru the night running my little chest freezer/converted to a frige. When the batteries are at 12.0v or lower the start up is too much for the power left in the batteries. Ive have one of those same batteries in my motorhome with small panels and that one lasted 2 years as well. Before buy new batteries can i fix these some how? Or is there a way to check if they are shot? I dont know much about batteries...

So those batteries are $75 each, lasted 2 years. Whats the best batteries for the value? I mean if i dont want a $300 battery that last 4 years, that makes no sense money wise.

Oh and the batteries are stored at a range from 30 low in the winter to 110 high in the summer.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Probably need new batteries, best bang for the buck?
    YostFMX wrote: »
    I have 4 Everlast 115 amp hr Walmart batteries that are 2 years old now, they dont hold out thru the night running my little chest freezer/converted to a frige. When the batteries are at 12.0v or lower the start up is too much for the power left in the batteries. Ive have one of those same batteries in my motorhome with small panels and that one lasted 2 years as well. Before buy new batteries can i fix these some how? Or is there a way to check if they are shot? I dont know much about batteries...

    So those batteries are $75 each, lasted 2 years. Whats the best batteries for the value? I mean if i dont want a $300 battery that last 4 years, that makes no sense money wise.

    Oh and the batteries are stored at a range from 30 low in the winter to 110 high in the summer.

    You've pretty much proven they're shot since they won't hold out through the night.
    One clue here: "When the batteries are at 12.0v or lower ..." 12 Volts is the bottom of SOC; you don't want to get there is it can be avoided and you certainly don't want to go below it.

    There is no way to fix a battery, despite what the snake oil salesmen say.

    What you need to do here is measure the power your converted freezer uses and recalculate that including conversion efficiency and self consumption of the inverter. Then get enough battery to power that without going down to 50%. Make sure they are true deep cycles, not "Marine/RV", make sure you have enough charging capacity to recharge them.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #3
    Re: Probably need new batteries, best bang for the buck?

    Humm so Marine/RV is diffenent than deep cycle? Everyone has said they are the same (not on here but ppl in auto parts). I guess look for ones that say deep cycle on them huh?

    I think i figured it right? 5-13% range of charging/totally storage. 615 watts of panels with 460 amp hrs of batteries (everything 12v)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Probably need new batteries, best bang for the buck?

    Definitely not the same: Marine/RV are like automotive batteries with thicker plates. They do not stand up to the daily cycling of an RE application.

    The 5% minimum charge current is NET, meaning after loads, and usually is inadequate to charge batteries in the amount of sun time available. If you target 10% you will have sufficient charging on most sunny days even with some load allowance.

    460 Amp hours @ 12 Volts is just a bit over what you can get from four GC2's (best buy in batteries).
    It would want 46 Amps peak current, or 716 Watts using an MPPT controller. 615 Watts would give you just about 40 Amps, or 8.5%, which should also work.
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #5
    Re: Probably need new batteries, best bang for the buck?

    I'm another proponent for GC2 batteries. I just replaced a 6 year old battery bank.

    Pics and details here: http://forum.solar-electric.com/showthread.php?20953-Sam-s-Club-Golf-Car-Batteries-Price-and-Opinion-check&p=176169#post176169
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  • SolInvictus
    SolInvictus Solar Expert Posts: 138 ✭
    #6
    Re: Probably need new batteries, best bang for the buck?
    YostFMX wrote: »
    4 Everlast 115 amp hr Walmart batteries that are 2 years old now

    Before buy new batteries can i fix these some how?

    Oh and the batteries are stored at a range from 30 low in the winter to 110 high in the summer.
    If the temperature of the batteries is 30 F now, they probably store about 60% of the energy compared to when it is 80 F and can not source as much power. If you can warm the batteries some, such as to 60 F, then they might be able to start your freezer converted to a refrigerator.

    Another possibility is to add more thermal mass to the refrigerator and run it for less time at night. For example, do not run it between midnight and sunrise during the winter.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #7
    Re: Probably need new batteries, best bang for the buck?

    That makes sense because it the batteries flaked out on me the first cold night. It went from hot to cold real fast out here in the CA desert. Its holding out 4 out of 5 days thru the night and thats with only running a 19'' tv and no lights, but it seems they are shot, + they arent even deep cycle (so i find out :-(

    So Sams Club is a free/no membership for this weekend so im thinking about buying some of the duracell GC2 now. From looking online it seemed hard for me to figure out how many i need. I'm only know Amp Hrs... So how many batteries do i need? Im not even sure how many amp hrs they are each.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Probably need new batteries, best bang for the buck?

    A GC2 is usually 220 Amp hours @ 6 Volts. You put two in series and get 220 Amp hours @ 12 Volts. Of this, only 110 Amp hours would be available as you do not want to discharge below 50%. It is better if you can keep it down around 25%, especially if you're short on recharging potential (i.e. panels). So that's 1.32 kW hours max, not including conversion and other losses. Half that if you limit the DOD to 25%. I don't know how that works with your power consumption.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #9
    Re: Probably need new batteries, best bang for the buck?

    Thanks so much for the fast reply, so it seems 4 batteries will do it for me. Just link the + to + then - to - on 2 sets of them then + to - those together huh? Im pretty sure thats right...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Probably need new batteries, best bang for the buck?

    Sort of the other way around. As in this diagram.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #11
    Re: Probably need new batteries, best bang for the buck?

    Humm thats interesting. It going to be hard for me to do that because i have mine 4 stacked vertically right now (i know it makes the wires longer) and its going to be hard to wire them like you have shown... If i had to can i wire 2 batteries together + to -, + to - make one 12v battery? That would be how you do it right? (I sse now that yea i said it wrong before, sorry) then take my '2, 12v batteries' and link them + to +, - to -, as i have them stacked so that would see the easiest way to do it. If i can line them all up front to back i will try to.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #12
    Re: Probably need new batteries, best bang for the buck?

    Umm i guess i dont get it because it looks like from that picture it would make 48v, or would how im saying make 48v.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: Probably need new batteries, best bang for the buck?
    YostFMX wrote: »
    Umm i guess i dont get it because it looks like from that picture it would make 48v, or would how im saying make 48v.

    We're talking about four 6 Volt batteries; there is no way to connect them that will make 48 Volts because 4 x 6 is 24; that would be the most Voltage you could get from them and that would require all four in series.

    The diagram shows two parallel strings (2X Amp hours) of two in series (2X Voltage) so the four 220 Amp hour 6 Volt batteries make a bank of 440 Amp hours at 12 Volts.

    How you achieve this mechanically matters only in that any parallel wiring (as in between the two strings and between the two batteries within each string) need to be equal length so that there is not a great difference in resistance caused by the wiring. That way the current should be shared fairly equally between the two strings. This is the reason for the 'diagonal' connections of positive and negative connections to the battery bank.
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  • YostFMX
    YostFMX Solar Expert Posts: 94 ✭✭✭
    #14
    Re: Probably need new batteries, best bang for the buck?

    So I bought four 6V GC2s from Sams Club (Energizer made by Johnson Control) Can I wire them like this in the drawing? Will A and B work just the same of is one better than the other? I wanted to wire it A because that will make my inverter wires both the same length as the way my inverter is the + is longer.
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