24 volt to 12 volt

Chris11 · August 2016

Hello again smart Americans,

I'm at the point of doing the pump house solar permanently. I have one 24 volt 185 watt panel. The pump, 120 volts, is about 8 amps....so about 1000 watts. I've been running it flawlessly on 4 6 volt golf cart bats through a 24 volt inverter...but I need those bats for another solar project.

How feasible is it to run just one 12 volt bat? I do have both 24 volt and 12 volt Chinese inverters that seem to be working great...I'm just concerned that a single 12 volt bat wont' be able to handle the necessary amperage draw. Oh, it isn't a huge usage pump...just for a weekend get away.

Can anyone give their thoughts?

Thank you, Chris

westbranch · August 2016

that pump,( comparing it to one of mine it should be about 1/2 HP rated?,) drawing 8 amps@ 120V, out of a 24 Volt system would need , while running, ~40 A to get ~ 1000W ..... this does not mean that that is the MAX amp output needed from the battery, nor the peak load on the inverter....
Most motors have a startup draw that can be in the range of 3 to 10 times the running load (A)... so you could have ~120A (2880W) to ~400 Amp(9600W) draw just to start the motor spinning, this is an instantaneous load that quickly drops to your 120V@8A....... Have a look at the rating for those GC batteries and see if you can find a 12 V battery with that amount of Amp rating... (NOT!!!)

So the short answer is NO... you, in all probability , will not be able to use a 12 Volt battery...
also you would need to substantially up-size the wires to the inverter, etc etc...

Chris11 · August 2016

Thank you Mr. Branch. Today I bought two Marine bats from Costco so I'll continue with the 24 volt inverter.

westbranch · August 2016

good choice... now you might want to consider the number of amp hrs you need for that motor.... I have a feeling that those new batts are lower Ahr rating than the older 6 V GC batts... as well as not being able to recover from heavy loads, like a well pump. GC batts are designed for heavy work!

Do you have a clamp on DC Amp meter?
Moderator BB has been recommending the Sears one at ~ $60 #82369

BB. · August 2016

Here is the link to the Sears DC Clamp Meter:

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

-Bill

Chris11 · August 2016

I do have a Kilawatt meter. That should do the same thing I would think.

Mr. Branch....I agree. The marine bats aren't as good as the 6 volt, but as I said, the pump is used intermittently, mostly on weekends, and not even for drinking water. Beer is better.

To tell you the truth I don't think we use enough water on the place to warrant the money I've spent on the well and solar system. However, as we speak, errr type, a septic system is being installed and since I'm building a western themed town, I'm going to put in an oldie type outhouse but with a flush toilet. I'm sure it will be the only outhouse with water in the county so the money will be well spent. At that point if the marine bats don't cut it I can upgrade.

Pic attached of the latest addition....the church with working bell.

Chris11 · August 2016

24 volt to 12 volt

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