How to use 12v appliances with 24v system

GWILESKI
GWILESKI Registered Users Posts: 2
in Solar Beginners Corner #1
What are the best ways to run 12v appliances, lights, water pump,etc from a 24v solar system?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: How to use 12v appliances with 24v system

    Welcome to the forum.

    For some things you can use a DC-to-DC converter, providing you can find one that will handle the current demand of the device(s) in question.

    Otherwise you can use the 24 Volt system to charge a 12 Volt system, but that requires a separate 12 Volt battery and a charger or MPPT type charge controller.

    On the whole I recommend against 12 VDC appliances unless they are absolutely necessary. Contrary to popular opinion low Voltage devices are less efficient than high Voltage ones.
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #3
    Re: How to use 12v appliances with 24v system
    GWILESKI wrote: »
    What are the best ways to run 12v appliances, lights, water pump,etc from a 24v solar system?

    Either tap off your lower battery and then use a bank balancer to make sure you don't unbalance the system, or use a DC/DC converter to drop 24V to 12V. They are readily available from suppliers like Meanwell, Vicor, PowerOne etc.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: How to use 12v appliances with 24v system

    Notice that all the replies pretty much revolve around down converting from 24 volts to 12 volts... In many cases, the down converting (and if you use a second 12 volt battery bank) are going to cost just as much (if not more) that a AC Inverter and be just about as efficient as good quality/efficient 120 VAC appliances.

    And, many times, the 120 VAC lighting and appliances can be cheaper than the 12 volt counterparts. Try a paper design "both ways" with your 12 volt and 120 volt loads and see what shakes out.

    If you have 12 volt native loads (like radio transceivers), then perhaps you are "stuck" with 12 volt solutions (but that even runs into issues... A typical 12 volt HAM transceiver wants ~13.8 volts to run at 100% of rated transmitter power--And a typical deep cycle battery bank will run from ~10.5 to 15.5 volts discharging to charging--Which many 12 volt devices do not like, or can even fail).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #5
    Re: How to use 12v appliances with 24v system

    Its the "worstest: thing to do run something off one of the 12v batteries.. You will never successfully balance them when recharging. A 24v to 12v converter is the only way.But as has been pointed out most converters only put out exactly 12v and that is a bit on the low side for some devices..
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  • ramloui
    ramloui Solar Expert Posts: 109 ✭✭
    #6
    Re: How to use 12v appliances with 24v system

    I will also be faced with the same issue and this is how I plan to solve it:
    My current system is 12V nominal and most of the power is converted to 120VAC with a MSW inverter that feeds the cabin except for the water pumps which are 12 VDC. My plan is to replace the inverter with a 24V pure sine this spring and rewire the battery bank to 24 V. At first I thought I would need a DC to DC converter for the pumps or swap them out for 120V models.

    But then it occured to me that the Iota charger I have will produce the 12 V nominal I need for the pumps from the 120V supplied by the inverter. I know this is not efficient. There are power losses converting 24 VDC to 120 VAC and back down to 12 VDC. However, I'm thinking that I should use the equipment I have on hand and I figure that there would also be some power loss if I used a DC to DC converter. I don't know the real figures but I may not be that far with my plan.

    Can't wait for spring and go back to the cabin...
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #7
    Re: How to use 12v appliances with 24v system
    ramloui wrote: »
    I will also be faced with the same issue and this is how I plan to solve it:
    My current system is 12V nominal and most of the power is converted to 120VAC with a MSW inverter that feeds the cabin except for the water pumps which are 12 VDC. My plan is to replace the inverter with a 24V pure sine this spring and rewire the battery bank to 24 V. At first I thought I would need a DC to DC converter for the pumps or swap them out for 120V models.

    But then it occured to me that the Iota charger I have will produce the 12 V nominal I need for the pumps from the 120V supplied by the inverter. I know this is not efficient. There are power losses converting 24 VDC to 120 VAC and back down to 12 VDC. However, I'm thinking that I should use the equipment I have on hand and I figure that there would also be some power loss if I used a DC to DC converter. I don't know the real figures but I may not be that far with my plan.

    Can't wait for spring and go back to the cabin...

    I know it will cost more, but what about switching the pump out to a 110v one? Especially one of the new energy efficient ones. Someone on here recently did that when they were recently faced with a similar problem when their x240 transformer failed. Ended up being easier, although a tad more expensive, to just get a new pump.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • ramloui
    ramloui Solar Expert Posts: 109 ✭✭
    #8
    Re: How to use 12v appliances with 24v system

    Yeah, that is definitely an option. However,maybe I'm not reading the spec sheet correctly but the 120VAC models don't seem to deliver flows as high as the 12VDC models.

    Also, I'm running 2 pumps in parallel to get good high flow (Shur-Flo 2088 ). I like a long hot shower with water pressure that is more than just a dribble:D.
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #9
    Re: How to use 12v appliances with 24v system
    ramloui wrote: »
    Yeah, that is definitely an option. However,maybe I'm not reading the spec sheet correctly but the 120VAC models don't seem to deliver flows as high as the 12VDC models.

    Also, I'm running 2 pumps in parallel to get good high flow (Shur-Flo 2088 ). I like a long hot shower with water pressure that is more than just a dribble:D.

    I believe that texaswellman is an expert in this area and helped out the other poster a few weeks ago and he was very happy with the results. Perhaps he will read this and chime in.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #10
    Re: How to use 12v appliances with 24v system
    ramloui wrote: »
    Yeah, that is definitely an option. However,maybe I'm not reading the spec sheet correctly but the 120VAC models don't seem to deliver flows as high as the 12VDC models.

    Also, I'm running 2 pumps in parallel to get good high flow (Shur-Flo 2088 ). I like a long hot shower with water pressure that is more than just a dribble:D.
    The pump you mentioned is 30 year old design and never had the flow your looking for or the pressure. The Aqutech 550 series is a, 5 diaphragm, 5.5 gpm and adjustable up to 80 psi. Available in 12, 24 or 120 volt.

    http://www.energybay.org/aquatec-550-pressure-pump-24vdc
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  • ramloui
    ramloui Solar Expert Posts: 109 ✭✭
    #11
    Re: How to use 12v appliances with 24v system

    OOOOOhhhh!!! Now I'm interested!!! I have a new option! Thanks for the suggestion!
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
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  • Out There
    Out There Solar Expert Posts: 96 ✭✭✭✭
    #12
    Re: How to use 12v appliances with 24v system

    With Texas Wellman's advice and encouragement, I recently purchased the Grundfos 110v pump, which has so far been GREAT! It keeps up with our demand and I'm totally happy with it. The other option (and what the previous owner did) was to invert the 24vDC power to 110vAC and then use a step-up transformer to generate the 240v needed for the pump. Another nice benefit of the Grunfos is the soft-start feature and no requirement for a pump control box! 110v directly to the pressure switch. Simple!
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