Battery size?
 

I was just reading the no altenator thread in the experiment forum. It had me thinking.

(since I have a slow dail-up connection I can not search for this topic too see if it has been covered, So if it has let me know.)

I was told that if all things where created equal a BIGGER battery would be stronger thus more desirable. However, in my brother's Civic HX the battery is half the size of the one in my Sidekick.

So my question is this. As far as FE goes what would be better? The BIG strong battery or the smaller weaker one? If Honda deems the small one fit it would reason to me it's better, but then again what do I know?

Also, can one use a NiMH or Li-Po like in my RC cars?

I think honda goes smaller because it's cheaper and lighter, my battery is smaller than the HX battery even. I could even run a lawnmower battery. A lot of performance nuts will go ahead and run small, sealed batteries to save weight and have the ability to move them to the trunk.

I see the point of a large battery for the no alternator mod, but without an alt I don't see the benefit.

<-- put a 12lb. lawn mower battery in his civic. stock battery was like 35lbs. i saved more weight on that lawn mower battery than i did on a carbon fiber hood and it ran totally fine for 2 years. it probably wouldve gone longer but i got into a car accident.

Good to know one would hold up for so long!

If you're planning to disconnect the alternator ever, then you need a large battery. I have over 150 lbs worth of batteries (3 of them) in my car for that reason. Yet, the FE benefit of running off those batteries outweighs (bad pun) the penalty of carrying the extra pounds.

If you're running the alternator all the time, I'd go for the lightest battery that will do the job.

Out of those 2 years was it just normal driving? No EOC or engine off at lights ect..

The thing to watch out for with smaller batteries is the parasitic loads while sitting unused. If you don't drive the car on a regular basis, simple loads like a power hungry digital clock and alarm system can kill the battery. Driven daily without overdraining, a small gel-cell should last about as long as any other battery however. As it applies to alternator-off driving, I'd advise against it.

nope none of that. just driving to classes then driving to work. occassional racing, where the car is started, ran for less than a minute then turned off and repeated all day long.

i just found out my starter needed 220 amps so i got a battery that had 230 cold cranking amps (cca). if i left the lights on for 90minutes the car would not start, it would just lightly turn.

The larger the battery the more power loss in general. Say a battery is rated at 100 amp hours (large battery). Typically a lead acid looses about 1&#37; a day. So every day you would need to add at least 1 amp or about 14w of power to keep the battery topped off. Now if you have a 25 amp hour battery it will only need about .25 amps to top it off or 3.5w. Not a huge difference, but it adds up.

As Snax I would consider what the other parasitic loads are on the battery, alarm systems, ECU's ect...

And obviously the overall weight as well.

I would oversize the battery if the car regularly sat unused for more then a week at a time, you live where it's cold like 0F or -17C and you need more cranking power or add a lot of other odd loads like an inverter or huge stereo or DVD players or such.

I thought about replacing my lead acid battery with NiMh batteries, but then it was pointed out that small packs can't take the high discharge needed to crank over the starter, and that to buld up a Lithium battery that could take that load seems to cost around $900, NiMh around $700, altho a very very large capasitor charged off of a smaller battery pack will alow you to do this with fewer batterys, but I haven't been able to find any capasitors that large, but have read about people that some how found them.
I've also wondered how those optima batterys compare, the sprail wound high performance batterys, but even those look to cost about $120, and the battery I have seems to be fine for now.