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Anybody Hot Rod an HHPI ?
Posted by: ROBOCOP
Date: September 20, 2014 01:10PM
I have a couple of HHPI's so I was feeling brave to experiment with one of them. One version is the older black head phone model with a custom Eric Foster 11 inch coil modded by Mr. Bill back in the day. That one I leave alone. I have 2 others that are the newest white models. One of them got the treatment.

The battery life on the HHPI is an interesting thing. With the best alkaline 9V batteries you start out with 9.6 + 9.6 volts or 19.2 volts. (series battery system).
After an hour of use the alkalines drop one volt each so you're down to 17.2 volts, after the second hour it's another one volt drop so 15.2 volts.

With lithium ion 9 volt batteries which start at 8.24 volts each I'm starting at 16.48 volts. They drop one tenth of a volt per hour so after the first hour I'm at 16.28, second hour 16.08, etc.

I wanted the performance of the first hour of the best alkalines so I went with a 19.2 volt Sears craftsman 4 amp battery in a plano box. Used a Sears craftsman work light as a battery connection to a DC voltage control card. Fabbed a small wire harness for inside the battery ear cup and installed a connector on the battery ear cup for the detachable battery connection. The small wire harness is removable if I wanted to revert back to using 9 v batteries.

It was my concept but I found a talented tech who put it together. I also have a Sears hedge trimmer and power drill which work off the same batteries so I really get to exercise them.
The Sears smart charger will recharge the 4 amp battery in one hour and the 1200 mah batteries in about a half hour. I detect every day and the running time and depth performance should be interesting. I back pack the plano box now and with cooler weather I should cover a lot of the Treasure coast.


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