Battery operated backpack sprayer pump

[vacman]

Hello everyone,

It’s been a while since I have posted here but I’m glad the forum is chugging along. I need some help on a repair project I have. I have a battery operated backpack sprayer that I screwed something up on and have a question. The original battery was a removable 18V of unknown brand and I wanted to change it to use a Milwaukee brand Battery. In my experimentation I reversed polarity and shorted something out so no power gets through the way it was designed. I took everything apart and I am able to bypass the original circuitry and it works but my wonderment is this - is the pump that is in there likely to truly be 18 volts or would it be a more common 12 volt? I tried looking for a small pump that is 18 volts but couldn’t really find anything with that rating which has increased my suspicion that it might be 12volts. Would that piece that fried out be a step down transformer? In my testing, I tried both the 18 volt battery directly and tried it it with a step down transformer to 12 volts and it works either way. I know it might work for a short while with the wrong voltage but it won’t last forever that way so I’d like to wire it up properly if I can verify what voltage the pump needs. Before some suggests it, there isn’t any tag on the pump that will tell me.

Hopefully someone has some experience with stuff like this and can shed some light.

Thanks in advance.

John

 

[jaxs]

My first thought is a new hand pump sprayer might cost than you'll spend to repair that motor.
Any electric device normally has a tag or ink stamp but in the absence of that I;d look for make and model on sprayer.
In my experience higher volts and lower amps rules when it comes to mechanical power so I doubt theres a stepdown transformer involved.
Origional 6 volt starters on tractors converted to 12 volts last along time so I'd go with 18 on the sprayer.

 

[Richard001]

My guess is that there is a reverse voltage protection diode some place that became shorted when you applied the voltage wrong.

Is there a circuit board ?

What brand and model is the sprayer ?

Richard

 

[vacman]

Thanks for your replies and ideas. This sprayer is as no-name and generic as you can get. The only sticker anywhere on it is a large one on the front saying it’s 18V Lithium powered. Inside there are no identifying tags especially on the pump itself where I looked to see if I could get the voltage information. There is a circuit board that was molded into a plastic housing that holds the on/off switch. There was also some kind of battery charge indicator that is visible above that switch which is on the front side of that circuit board. It could be that there was a protection fuse in there that blew which was my first thought but it’s not fixable. I bypassed that circuit board altogether and I can get the sprayer to work so the switch and pump are not damaged. My quandary is that it will work both with the 18 volt battery direct as well as if I use a 12v step down transformer. It could be that it won’t matter in which case I will just use the 18v direct but I’d hate to fry out the pump by using too much voltage.

Thanks again for your help.
John

 

[Richard001]

Can you post a photo of the unit and a close up of the circuit board. Perhaps someone will recognize it.

If the sprayer was originally powered by a 18V battery, then you should not have to worry about the motor.

A lot of battery powered tools use 18V batteries. So there are alot of 18v motors out there.

 

[etpm]

The DC motor in your sprayer will run on 12 volts but just slower. For the type of motor most likely in your sprayer the voltage controls the speed and the current controls the torque. So if the 12 volt supply you used can also supply enough current the motor will indeed spin, just slower.
Eric

 

[Rustyiron]

Stay clear of no name battery powered stuff. Even if the unit stays working, the battery will eventually no longer hold a charge, then you have your situation.
A side handle pump on a "backpack" sprayer takes very little effort and with proper care, last for years.
(In case you need to replace this one)