Jump Start Battery - Opinions?

http://hitches4less.com/jumpstarters.html

For peace of mind with my new stereo install, I was thinking about purchasing one of the jump starter battery boxes in case I run my battery down at the lake.

What size do I need? Will be these effective with a deep cycle battery?

I thought about adding another battery, but this jump starter would come in handy with starting stuff around the garage or just nice to have in my truck to help myself of someone else out.

Any opinions??? thanks

Deep cycle batteries are not designed for spinning American V8 engines. too much internal resistance. They result in burned cables, crusty starters, and solenoids with welded contacts.

If you have starting problems consider ditching the deep cycle battery

Get a nice 825 Amp cranking battery and fugetaboutit.

The Deep Cycle battery cannot provide BOTH high amps and High voltage at the same time. When amp approach 50-75, the battery's internal resistance lowers the delivered voltage, self-limiting the power delivered.

So you crank longer and slower. DC motors pull more amps the slower they turn, less amps the faster they spin. A struggling starter motor pulls max amps, which means max heat. The starter relay has insufficient voltage because the starter is pulling the battery voltage too low because it appears like a dead short. Insufficient contact pressure arcs the contacts and welds them together, so when you let off the key, the starter keeps turning, frying the cables and/or starter while you struggle to disconnect the battery.

To sum up Deep cycle batteries struggle to produce the immediate power needed to start a V8. you can get by with a 2-cyle outboard, but not an auto engine (for long) More starters are fried and repalced due to deep cycle batteries in the wrong application.

I think an isolator is a diode network that keeps you from pulling you starting battery down when running accessories, but permits charging from one source.

Could add a trolling motor

I dont plan on running my battery down, if we are on the lake, the motor is usually running. However it is more for like a just in case situation, would it work fine for that?

I have a 300 amp jump starter and it has started my boat eight times on one charge. Then I decided to buy an alternator. I still keep it on the boat fully charged. Its small, its safe and it works.