Test: Alternator vs. no alternator = 10% MPG gain @ 70 km/h

[electricman]

And - the 4 x 40 Ah Cells = 4 x 1.6 Kg, 6.4 Kg/14.08 Lbs.!

[ConnClark]

Originally Posted by Christ

There is also not alot of need for an alt on cup cars... Not alot of lights and stereo/climate control, ya know? That being the case, it might have produced enough power to keep the battery charged and keep the ignition system operating, but likely not much else.

Actually there is quite a need for an alternator for cup cars. You have an electric fuel pump, Cooling and ventilation fans, Telemetry recording device and sensors, Helmet and cool suit cooler, on board camera, and the list goes on.

[Kevinr]

I own a 1994 Geo Metro XFI with 120k and I am adding a kill switch for my alternator.

What battery do you guys suggest?

I will also be adding a battery monitor that plugs into my cigarette light for less than $20

Also a cheap 5 amp solar panel that I will plug in when I am parked.

Any ideas so I don't get left stranded?

[MetroMPG]

Hi Kevinr -

Apologies for the delayed response. Your message got stuck in the moderation queue for some reason. It normally just traps spammers.

Originally Posted by Kevinr

I will also be adding a battery monitor that plugs into my cigarette light for less than $20

I got one of those on eBay. Something like this:



It works, but was off by about .2 volts. Make sure you calibrate yours against a trusted voltmeter before you rely on it.

Any ideas so I don't get left stranded?

Monitor the voltage. Learn how to bump start in advance, in case you kill the battery

FYI, I'll say again that this modification is NOT battery friendly.

Deep discharges are bad for a lead acid battery, and will shorten its life. If used aggressively (deep discharges), I suspect this mod may end up costing money in the long run unless you have a source of free or cheap batteries to keep the project going.

[oil pan 4]

You will want to use a deep cycle starting battery.
Regular starting batteries will see a big reduction in life expenctancy if you use more than 20% to 30% of their capacity.
No matter what battery you go with you will want to stay with in the upper 50% of its capacity to get the most life.

[Ladogaboy]

I would use a Lithium battery instead. They can withstand regular discharges of ~80% or so, they hold a better charge (more amps), and they are lighter. If it's not an inconvenience, just pull the battery and recharge it on a wall charger after every commute.

[oil pan 4]

I have a lithium battery in my car and there is no chance I would be discharging it more than 40%. I for one wont risk a $300+ battery for a few mpg.

[Ladogaboy]

Then you aren't really seeing the full benefit of the Li battery. If you are concerned with going greater than 40% depth of discharge, you could always just track your power usage and build a Li battery accordingly.

[deathtrain]

Originally Posted by oil pan 4

I have a lithium battery in my car and there is no chance I would be discharging it more than 40%. I for one wont risk a $300+ battery for a few mpg.

what battery are you using? and you using it for craking and running?

[brucepick]

Powering headlights without the alternator?

I did a search on "headlights" and "light" in this thread - found nothing.

I'm now using a regular 'starting' type battery. Even a half minute or so of EOC runs down the battery to 11.5V or less if headlights are on, with headlight dimming as a visible result. And they really only have full brightness between about 13-14V, when the alternator is running. So any upgrade to the alternator/battery system will have to take into account the need for headlights to be on. My commute is 55 miles each way so the solution has to be good for that distance.

Has anyone here had luck running headlight off a deep cycle 12V battery that also powers the rest of the car, with alternator in use when needed? If that works well it would be a relatively low cost and easy solution.

My headlights are already running via relays so I could easily power them from a separate battery - but again, if voltage drop over 2-3 hours use will give me dim headlights, I'll need another solution.

"Another solution" is a 14V deep cycle AGM battery + charger by XS Power.
14V AGM deep cycle, $260
14V AGM_capable charger, $200
Definitely not a low-cost solution but the 14V battery - charged between driving episodes - should run the headlights very nicely, I would think.