info on a 12volt pump

I have a 97 Ford Econoline Super Duty with a 7.3 diesel. I need some info on what is the best method to hook this 12Volt Pump up so that I can run the pump during a job, charge the pump while driving, and not interfere with the normal electrical system negatively. I'm thinking maybe add a third battery dedicated to the pump only - but I'm not sure how to wire it into the electrical system so it does everything listed above. All help is greatly appreciated.

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Landis Roof Cleaning
Birdsboro, Pa 19508

A 3rd battery? Is it a 24V system?

And what do you mean by "charge the pump while driving"?


If you have a 24V system, I suggest you get a 24V pump.
Otherwise you need a dc-dc converter to drop 24V to 12V, and another 1 or 2 batteries if you want independence from your 24CV crankers.

With a diesel vehichle, there are already two batteries setup. I believe one is for the start up of the diesel engine and one is for running all of the other accessories.

As for charging the pump, I meant to say, if I install a third battery -dedicated to the pump only, the battery is what I want to charge while the vehicle is running. I just need to know how to hook up the third battery to the vehichle's electrical system so it doesn't pull from the main vehicle batteries  but still re-charges itself while the vehicle is running.

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Landis Roof Cleaning
Birdsboro, Pa 19508

Assuming it is a 12 volt system (ie, NOT a 24V alternator), and if you have a charge light, then I suggest a relay controlled by the charge light circuit - ie, D+ or L from the alternator (or its regulator). (eg, Google "UIBI oldspark".)
That assumes the D+ or L circuit can supply the current for the relay coil. If not, it may damage/destroy the regulator.

Hence the circuit is front battery(s)+12V via fuse then relay to the 3rd battery's fuse & 3rd battery.

Cable, fuse & relay sizing depends on the pump's current and the maximum battery recharge current.
Instead of fuses I suggest self resetting circuit-breakers, else (or and?) a battery protector for the 3rd battery (ie, a low-voltage cutout).

Self resetting CBs are small and cheap up to 50A, hence a 60A relay with 50A rated cabling and 50A CBs. Or 30A relay with 30A cable and 30A (or smaller) CBs etc.