Dual battery scenario.

Why would you want two batteries?

stereo, brighter & powerful headlights, electric engine cooling fan, GPS ect.

Good question, I'd like some info on that proposal also.

I would probably upgrade my Alternator instead, that makes more sense IMHO

I know for a fact from my experience with 4x4s that a beefy alternator and an Optima will run 6 100w off-road lights plus ground-pounding stereo plus GPS plus DVD player plus CB plus a 12,000lb winch plus electric fans, etc. etc. Only guys that want to run stuff like TV's etc. at the campsite without risking running down their starting battery run two batteries. I can't imagine any reason to have two batteries in a Spider.....

Heck, I used to run highbeams, a pair of 55w fog lights, a pair of 100w driving lights and a 4-amplifier, 11 speaker stereo system cranked all the way up on the stock alternator in a Honda CRX with an Optima. It'd do that - all at the same time - all night long.

Chris

If you do feel compelled to try dual batteries, connecting them in series doubles the output voltage while connecting them in parallel does not. (as in you'd want to connect them in parallel unless you're going for a 24V circut)

GV27 said:

I know for a fact from my experience with 4x4s that a beefy alternator and an Optima will run 6 100w off-road lights plus ground-pounding stereo plus GPS plus DVD player plus CB plus a 12,000lb winch plus electric fans, etc. etc. Only guys that want to run stuff like TV's etc. at the campsite without risking running down their starting battery run two batteries. I can't imagine any reason to have two batteries in a Spider.....

Heck, I used to run highbeams, a pair of 55w fog lights, a pair of 100w driving lights and a 4-amplifier, 11 speaker stereo system cranked all the way up on the stock alternator in a Honda CRX with an Optima. It'd do that - all at the same time- all night long.

Chris

Click to expand...

yellow, blue, red top

I plan to use a milano alternator. but it is a 45amp I think. my stereo amp is power hungry and my red top is straining.

Red top. I guess you must have a real beast of an amp. IIRC my 4 amps added up to 600 watts RMS. Plus 300 watts of lights. Like I said, I've seen a LOT more than that run off of a red top. I think my buddy's Grand Prix has a stereo in it with like 2000 watts or something. One red top. Like a 100 amp alternator or something like that and caps as well, though......

I dunno....you only have a 100 and some HP, I wouldn't want to add much more than 500 or 600 lbs of weight......

Wild and wacky, a little crazy...

The 1986 Alfa has the battery in the back for weight distribution. If you want more electrical power output- run a higher output alternator as suggested above. Maybe sirens and flashing lights too. You could also consider buying a newer import car which already features the mighty sound system. Consider a four wheeler with lights, lift kit, but then we're not talking Alfa Romeo. Buy a motorhome. They have two batteries for all the goodies. You can tow your Alfa with it too.

I know the S4 spiders came with a 70A alternator and I'm pretty sure some of the later S3's did also. You might want to try a used one.

landman said:

I plan to use a milano alternator. but it is a 45amp I think.

Click to expand...

Milano alternators were 65 amp, except for the late 3.0 which was 70 amp IIRC.

to answer your question, I have run two batteries in a couple of my spiders. I tend to drive early 70's models so the battery is in the front (stock). what IO did was use a wire harness from a later model spider that has its battery kept in the trunk. I will admit that the jury is still out on whether or not it made a big difference. A new battery in good condition can sustain its charge for a good long while as long as the rest of the charging system is in order. Mostly I used two because I like to relocate any engine compartment battery to the trunk any way, so I occasionaly will use a second if It drains too quickly. I also like to use the stereo when the car is idle. IMHO get a good quality battery (new) before you go to great lengths in other directions.

And get one of the 65 or 70 amp alternators, if you want to keep to alfa parts. BTW - there are 85 amp to 130 amp bosch alternators from BMW's and MBZ's available - they're a bit big and need a different drive belt and bracket.

70 amps = about 950 watts
130 amps = about 1700 watts (13.3 volts)

Robert

60sRacer said:

And get one of the 65 or 70 amp alternators, if you want to keep to alfa parts. BTW - there are 85 amp to 130 amp bosch alternators from BMW's and MBZ's available - they're a bit big and need a different drive belt and bracket.

70 amps = about 950 watts
130 amps = about 1700 watts (13.3 volts)

Robert

Click to expand...

I'd agree with most who recommend a higher output alternator. You could put 10 batteries in your Alfa, but with only 45 amps to charge them, they won't do you any good.

Dual batteries are most useful in starting large motors on cold mornings, or running accessories for a long time with the engine not running.

I'd upgrade your alternator first, then maybe stick with a single, higher amperage battery.

My .02,

bs