[Nerys]

yes they do. at least in a GEO they make sense together. My objective is to remove "ALL" Load from the engine except that of "moving" the car. my only two accessories are water pump and alternator.

the water pump (electric) at full tilt is 4-5 amps. I can drop that to 2-3 amps since I am cooling a wee little geo and not the V8 Racing engine they are designed for.

that amp load is SMALLER than the current amp load of my incandescent light bulbs. by a lot.

so going to LED and possibly 35w HID for the head lights will save me more than double the power that the electric water pump will consume at full tilt. 4 times at lower draw.

2 deep cycle batteries will let me go one week without a recharge (without going below 50% DOD)

except in the winter where I need the head lights more often and the blower. then every 3-4 days will need to plug in (but I will plug in nightly anyway to be on the safe side)

the water pump is a larger mechanical load on the engine than the Alternator if memory serves me correctly. though this may be different on the geo.

thats the math I came up with ecomodded. figure twin 100 amp hour batteries which meant without going below 50% DOD I had 100 amp hours to play with.

In the beginning I could even go on ONE deep cycle as long as I charge up at work and at home. (I have an optima blue top scored lucky on craigslist)

lets put it this way. I left ALL the lights on for 3 hours accidentally (2 hours 58 minutes) and the car started right up (though at idle the alternator REALLY bogged the engine down with the load of recharging that battery)

Really impressed me these blue tops. (scored it for $60 on craigslist !!) got it for my boat I use it in the geo when not in the boat.

6 amps for the car itself. .5 amp for lighting (50% usage) (once I go all led less than that but rounding up for safety) 3 amps for the stereo and surround sound (I was surprised how little power it consumed) 1 amp for misc accessories and 3 for the water pump.

13.5 amps so far MAX possible plus the head lights. 7 amps. figure 50% usage so 3.5 amps or a total max possible of 17 amps.

so 50% DOD is roughly 5.88 hours figure 6 hours so 300 miles. or about 5 days and thats worst case scenario. (except if I need the blower)

more than enough power if I charge at work and at home and more than enough power if I "forget" or the charger "fails" for some reason.

I will leave the alternator and water pump physically in place. I was THINKING about install another pulley to a small tiny efficient electric motor to very slowly "turn" the water pump and alternator. this way my belt and my bearings won't "rot away" on me. this way I can just rebelt if I need too for any reason.