Any ideas on small DIY 7.4v lithium battery?

Went out last Monday, an hour to walk in, 5 min detecting and my 4500 shut down, an hour to walk out and off home to discover the problem, which was a short at the lead plug. Since I do a fair bit of time walking into likely areas in my territory I think a small lightweight backup battery and leads would be worthwhile to carry, using earbuds instead of the speaker if necessary.

Around 4 to 6AH should give a minimum of 4 hours detecting if I can't use the main battery.

I've seen the designs from other diy battery projects on this forum, the potential main problem with them is, as Narrawa suggested, the lack of a regulator to protect the detector from possible voltage problems.

Does anyone know a way of making a regulated DIY battery as above?

Thanks for any input,

Bill.

I alway carry and original spare....... I find the Minelab ones Light as.
When I first brought the 2 4500's I also ordered an extra spare battery for each detector..... it works out great if you decide to go out again at night....you can leave the first one on charge for the next day and so on.
Lithium Polymer batteries are so dangerous I was happy to buy the factory unit in its proper housing and electronics.....

Bill, i used this one a few years ago when i built my battery system for the GP-3000.
http://www.jaycar.com.au/productView.asp?ID=KA1797&form=CAT2&SUBCATID=965#11

I wouldn't really bother using a regulator unless you intend using batteries that are above your required voltage..... they themselves suck up power.
Batteries produce smooth stable power until they run down, and the regulator will have stopped long before that....
Why not just build up a supply using a configuration of series / parallel cells to get the voltage and capacity you require....

If you do require a regulator.....this is all you need..... leg 1 = positive voltage input , leg 2 = Ground , leg 3 = regulated positive output....... good for an amp.....just bolt it to something that will absorb the heat......


7808 = 78 series and the 08 is the regulated output...8 volts ( it will regulate the positive side of the power source )

Thanks guys, I've got a bit more thinking to do.

Lithium Polymer batteries are so dangerous I was happy to buy the factory unit in its proper housing and electronics......

The minelab batterys are not LiPo, batterys and are very safe. But you are right about LiPos being bad news..

The batterys in a Minelab pack are LiFePo4 type cells and are very safe. tempermental yes , if you charge them more and dont let them go flat before recharging you will get more life from your pack...
And when you store them for next year you dont have to charge them fully, better to leave them half flat.
Bob....