Can I use 12v charger to...

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rgk1
rgk1 Solar Expert Posts: 135 ✭✭✭
in Solar Beginners Corner #1
Can I use my Iota DLS/45 12 volt charger to charge a 24v bank? I have made the switch to 24 volt and am very aware of the expensive trap I have fallen into. I never imagined my solar hobby would ever evolve beyond a very small 12 volt system. But, realizing the advantages of 24 volts and picking up a practically brand new 24 volt inverter very cheap leaves me wonderig what I can salvage from my 12 volt project.

The current batteries are no problem. A total of eight 6 volt and a pair of matching 12 volt ones. I have mothballed the Morningstar Sunsaver MPPT controller, but even that can do 24 volt. My old SureSine inverter? Heck, who can't find a good use for something like that? That brings me down to an expensive to replace charger for those times the sun don't shine. I consider it a critical piece since the most important goal was to have some power in an emergency situation.

To make a long story short and get down to the question, can I use my 12 volt a/c charger to charge the 24 volt bank by using bus bars and tapping into each 12 volt section of the 24 volt bank? I have never heard of such a configuration so probably can't be done, but I have to ask.
4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Can I use 12v charger to...

    Not simultaneously you can't.
    But you can charge "half at a time". It will not be a good way to charge, but for emergency Bulk charging it would work.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #3
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    Re: Can I use 12v charger to...

    I use 4 of the eight (identical other than service life) batteries daily. So, probably better to just keep the other 4 on standby and on float in a 12 volt configuration untill the rare occasion that the current set are discharged and no sun to recharge, then swap them out? I was just trying to keep from having to swap them out in such an event.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Can I use 12v charger to...

    For maintenance charging that's probably your best bet.
    There's no way to charge 24 Volts directly from 12, and you don't want any connections mid-way between strings either.

    (Anybody who says "use a DC to DC converter" is gonna get a kick in the head. :p)
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #5
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    Re: Can I use 12v charger to...

    Thank's Cariboocoot. Thats what I thought, but like I said. Just had to ask.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
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    Re: Can I use 12v charger to...
    rgk1 wrote: »
    The current batteries are no problem. A total of eight 6 volt and a pair of matching 12 volt ones.

    This sounds like trouble... are the 12 volt batteries hooked up in parallel with the two strings of 6 volt batteries? Also your signature line has only 4 batteries. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Can I use 12v charger to...
    vtmaps wrote: »
    This sounds like trouble... are the 12 volt batteries hooked up in parallel with the two strings of 6 volt batteries? Also your signature line has only 4 batteries. --vtMaps

    It depends on if he means the 12 Volt batteries match each other or match the 6 Volts in capacity. It is also not a good idea to mix old batteries with new, and for the same reason: batteries of different capacity will have different charge rates. What started out as a 200 Amp hour battery won't be that after it is used for awhile.

    It sounds like at this point he has a 6 Volt set and a 12 Volt set to be used separately as dual banks. I wouldn't recommend putting them all together for a 24 Volt system even so, due to the inevitable differences in age/capacity.

    Yet another adventure in the near impossible quest to scale up a solar power system without tossing the whole thing and starting over. :p
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #8
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    Re: Can I use 12v charger to...

    What I have is 8 - 6 volt batteries (powersonic agms) that are all the same brand/size/age. I also have 2 - 12 volt batteries (universal battery) that are a matched set. For the last 12 months I have only had 4 of the 6 volt ones in service. These were in a 12 volt configuration till a few weeks ago. When i got the new inverter, I reconfigured the same 4 for 24v operation. The other four 6 volts were/are configured for 12 volt and kept separate and on float with the iota charger since i can no longer keep it hard wired to the new 24 volt system. The other 2 universal batteries are charged occasionaly.

    The universal batteries are about 2 years old and the powersonic have date codes of late '06 early '07. I bought the powersonics used and really didn't expect much from them, but so far have found no reason to take them out of service.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Can I use 12v charger to...
    rgk1 wrote: »
    What I have is 8 - 6 volt batteries (powersonic agms) that are all the same brand/size/age. I also have 2 - 12 volt batteries (universal battery) that are a matched set. For the last 12 months I have only had 4 of the 6 volt ones in service. These were in a 12 volt configuration till a few weeks ago. When i got the new inverter, I reconfigured the same 4 for 24v operation. The other four 6 volts were/are configured for 12 volt and kept separate and on float with the iota charger since i can no longer keep it hard wired to the new 24 volt system. The other 2 universal batteries are charged occasionaly.

    The universal batteries are about 2 years old and the powersonic have date codes of late '06 early '07. I bought the powersonics used and really didn't expect much from them, but so far have found no reason to take them out of service.

    Okay, the main issue here is Amp hour capacity. Unless the capacity is the same for a 24 Volt string of the 6 Volt batteries and a 24 Volt string of the 12 Volt batteries you really should not parallel the two. The greater the difference in capacity, the poorer the result will be. If they are two different types (you mention the 6 Volts are AGM but not if the 12 Volts are) it is even worse as the charge Voltages will be different. It is probably not a good idea to use the 12 Volt Universals in conjunction with the 6 Volt Powersonics at all.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #10
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    Re: Can I use 12v charger to...

    Right. Only 4 batteries are in use....four of the 6 volt/210ah (wired in series 24volt/210ah). Sitting on the shelf connected to nothing are the two 12 volt Universal agms. Also sitting on the shelf and connected to nothing are the other 4 powersonic agm's. I have those 4 wired in a 12 volt configuration for ease of charge/float with the Iota 12 volt charger.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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