help (24V pump)

[StressMan79]

I'm looking for an inexpensive on demand pump with 1/2 inch connections that provides approximately 3 gpm, that runs on 24VDC.This last bit seems to be the kicker, as I found 48-131-a(e)65 that should be fairly cheap, but no one sells it. I'm also looking for a pump that does around 55 psi. The others I found are max of 45.

Help, the google search always brings back links for the -101-, the 12 VDC version... Lots of them available. did find the 24 volt version on ebay.co.uk... what is the deal?

Thanks

-Peter

[loghousenut]

Why not use the 12v pump and run it off of a 12 volt side of your battery?

[StressMan79]

LHN, that is a terrible idea. Id be better off running my 6v's in a 2+2 config, scrapping my inverters and charge controller. you know that this would power the pump off just half the bank, draining it very unsymmetrically, and you can't recharge it w/ the solar array... so you'd run your array down to say 9+15, keep sucking that side lower and lower, and now the solar controller thinks that you don't have enough juice, keeps charging the bank, boiling the first half dry.

Eventually your batteries are very dead.

[loghousenut]

I figured it was a terrible idea but I really wanted to hear someone with brains say it out loud. I would never have come up with the idea on my own. If I hadn't seen it done so many times, I would never have even thought to mention it.

Rural Oregon... Go figure.






Are you really sure it won't work?

[loghousenut]

If I hadn't seen it done so many times, I would never have even thought to mention it.

Rural Oregon... Go figure.






Are you really sure it won't work?



OK let me qualify my statement just a bit. I have built a 12v system or two and been around a few more and a few 24v and 48v systems, both with and without inverters. I can't say that I've seen a BIG 12v load successfully tapped off of a well running higher voltage system. I have seen a few small loads tapped off. Things like a 12v burgler alarm or maybe a light in a battery shack, etc, etc. I will defer completely to the engineer in this case and trust your better judgement entirely... As usual!!!

[donjuedo]

I could see some value in tapping off half, but for that to be good, there would be more work.

My brother's BMS (battery management system) monitors each cell to see when one gets too far from the average. Then it does what's called balancing, to bring the voltages back together. I was very disappointed to find that meant draining the good ones. Yup, just throwing away energy. I wanted to see it charge the low ones only.

In your case, you could have a circuit check which of your two 12V batteries is higher, then connect the pump to that one, when it's time to turn on. It balances your 24 V pack, and without throwing away energy.

The only catch is, someone has to design that special circuit. It's not rocket science, but quite a bit of time.