Completely discharged battery hypermiling? Air seat radio off. Left headlight out.

[Ryland]

Your alternator is most likely only putting out 40-50 amps at the very most, your cars computer, fuel pump and other electrical loads that you have no control over are most likely drawing 10-15 amps and your starter is drawing 200 amps or more for a few seconds every time you use it so it sounds like you need a larger battery and charge it more, a solar trickle charger is going to help your battery up to a full charge and thus keep it lasting years more.
leaving your battery partly charged while parked for hours at a time is going to play a big role in how long your battery will last as it sounds like you never run the engine long enough to recover from using the starter.

[ConnClark]

Originally Posted by comptiger5000

Connclark - A deep cycle can start an engine fine. It just outputs less burst current, so you need a somewhat bigger battery than you would with a starting battery. Starting engines off marine deep cycles is common in boats. A dual purpose starting/deep cycle like an Optima yellow or an Odyssey will work fine as well.

I never said you could start an engine off a deep cycle.... I said it would shorten its life. The closer a discharge is to the maximum deliverable current of a battery the more it wears a battery out. Also if your battery is having trouble delivering the current to your starter it will undervolt the starter motor and this can cause it to over heat and burn out.

[endurance]

A typical car will have about a 44 Amp Hour battery in it. Your headlights on low beam with running lights draw about 95 watts, or about 8 amps. Your heated seats are probably one of the larger draws, probably around 180 watts, or 15 amps. Add another 40w for the stereo, or 3 amps, another 60w for the blower motor on your heater (5 amps) and you're talking about a constant draw of 31 amps. If you're EOC'ing for 30 minutes, you've tapped out over half the capacity of the battery, then you want to use the starter, which draws 75 amps. That's where your problem lies.

That's why it's best to EOC when it's light out, with minimal accessories on. Your idle probably burns on the order of .15-.25 gallons per hour. A half hour of coasting at 30mph means you'll use .075-.125 gallons while covering 15 miles (that's still 120mpg while coasting with the engine on). In any case, if you're going to try to EOC, nix the power seats, keep the blower motor on the lowest setting, and look at converting to HID headlights and LED marker lights.

Overall, even a deep cycle would have problems with your demand. If you can find a 55ah battery, great, but you're still going to have to avoid using those heated seats, buy some high efficiency lights, and be careful with demand. I'm learning I can EOC during the summer, when the sun is up early, goes down late, and I don't need the heater or defroster on, but right about now, it's impossible. It's too dark, too cold, and I still need to be able to operate the vehicle safely and reliably.

120mpg coasting still beats the heck out of 0mpg sitting on the side of the road waiting for a tow truck.

[bobmutch]

@endurance thanks for the info.

I think what I will consider doing is EOC in the daytime only with my headlights disconnected. Then in the evening I will just glide in netural. This way I am not going to be as libel to wear out my ignition, starter, and battery.

[Sulfuric]

Originally Posted by MorphDaCivic

I just purchased a Yellow Top Optima battery (D51R), it is dual purpose Deep cycle and starting. Also holds it's charge for a year without loss.

Optima batteries are expensive, but it helps that I work for the company that makes them.

Am I allowed how much of a discount you get?

[endurance]

Check craigslist. There's a local company selling them for $109 here in Denver off of Craigs list (group 31 or 34 only).