24 vdc portable power supply

Hello all,
I am looking for a portable, (battery powered), 24 vdc power supply.
My situation is this....

I have a flow sensor that I would like to use as a portable diagnostic tool. I would like not to have to provide 120 vac to the unit. It requires 24 vdc at 100ma. I have a couple sensor testers here but they all use two 9 volt batteries and the output voltage is not enough. Is there a pre-canned solution for this out there or am I making my own? I did some searching and came up empty.

Thanks for any help,
Dave

How about this?
http://www.looppowersupply.com/products.html

Or, check some "Loopys" for calibrations put out 24vdc.

George

George Graziano said:

How about this?
http://www.looppowersupply.com/products.html

Or, check some "Loopys" for calibrations put out 24vdc.

George

Click to expand...

Yes!, but no.

Correct me if I'm wrong but I see the max current on those are 25ma. What I am looking for would be 100ma.

But that is exactly like what I am looking for.

Thank you.

Dave

What are your supply voltage permissible ranges? 3 9V batteries in series is 27V.If you must drop it closer to 24VDC exactly, you could put in a series 3V zener, or 4 series 1N4004 diodes.

Lithium will be best. They hold voltage till end of charge, then drop rapidly.
Lithium 18650 = 3.7V
7 x 3.7VDC = 25.9 VDC

Multi-Cell Lithium battery holders are all over.

I do rdrast's thing, three series wired 9V batteries for powering loop powered transmitters that typically can handle power supply voltages from 14-35Vdc when I need to ensure the unit is getting clean, isolated DC power.

I've run a radar level transmitter for four days continuous at 18mA output with a battery pack.

Extrapolating for 100mA output, a 9V battery pack will probably last almost a day of continuous output.

It's cheap and easy to make - Radio Shack sells (or used to sell) the 9V battery.

I use a coaxial DC power connector jack on the battery pack and a mating plug on a separate cable with flying leads. I keep the flying leads cable off the battery pack during storage or movement to ensure that leads to the battery pack don't short because those 9V batteries produce enough current to burn the insulation off the wires and start a fire in the event of a short.

If you would prefer something that stays at 24V:
I can't point you to specific web pages because I get the UK ones at the top of my list. Search for 'in vehicle dc/dc converter' or for a more open search just use 'dc/dc converter'. Don't know if it is any good, but I found this on Amazon.com:
http://www.amazon.com/gp/product/B0...erter 24V&qid=1443598934&ref_=sr_1_17&sr=8-17
10-22V input, 24V output

rdrast said:

What are your supply voltage permissible ranges? 3 9V batteries in series is 27V.If you must drop it closer to 24VDC exactly, you could put in a series 3V zener, or 4 series 1N4004 diodes.

Click to expand...

Permissible input voltage is up to 30 volts dc. I think I am liking NetNathan's suggestion of a multi-cell lithium setup. I hadn't considered that but it makes perfect sense.

Thanks for all of the replies.

Dave

A battery from a battery drill would work well and you would have the correct charger for the battery.

And then there's the very interesting adjustable boost regulator:
https://www.pololu.com/product/799