H/O Alt, volt drop in reverse and at idle.

[Lowkey 10+ year member]

So say my explorer which revved out at about 5000 RPM, my alternator is spinning faster at idle because they can put a smaller pulley on my motor, since my motor spins 1500 RPM's less than yours. It's just gearing, essentially.

Is it something I should be worried about? I'm pretty soft on the gas, never really go above 3000. Typically around 2000.

 

[Buck 5,000+ posts]

Is it something I should be worried about? I'm pretty soft on the gas, never really go above 3000. Typically around 2000.

You're just gonna have to deal with the voltage drops, unless you get some good reserve amperage in there. Some companies design alts better than others, so you could see if another company claims to make one that works better with minimal input RPM.

 

[Lowkey 10+ year member]

You're just gonna have to deal with the voltage drops, unless you get some good reserve amperage in there. Some companies design alts better than others, so you could see if another company claims to make one that works better with minimal input RPM.

I think I'll be alright, appreciate the insight. I just added a massive 200ah secondary battery. I imagine it will give me more than enough reserve for the brief times the voltage is in the 13s.

 

[hispls 5,000+ posts]

I think I'll be alright, appreciate the insight. I just added a massive 200ah secondary battery. I imagine it will give me more than enough reserve for the brief times the voltage is in the 13s.

Sounds like everything is behaving as it should and 13V isn't going to hurt anything.

 

[Buck 5,000+ posts]

Sounds like everything is behaving as it should and 13V isn't going to hurt anything.

x2. This is one of those things that people just have to deal with, with certain motors in cars.

OP, you could get a big ole v8 that turns slow and you'll have alt power for days haha. I've even heard some people go as far as putting an artifical RPM limiter on their motor so they can run a smaller pulley for idle, but that'll get you killed on the road in a daily driver. Those small motors build all their power from high revving. I would never limit my RPM on a small motor like that, that's very dangerous.

I wonder if super caps or something like that would help you here. I'm not super familiar with them, but some others may be. I'm sure there's a way to mitigate this problem, to some extent.

 

[Lowkey 10+ year member]

x2. This is one of those things that people just have to deal with, with certain motors in cars.

OP, you could get a big ole v8 that turns slow and you'll have alt power for days haha. I've even heard some people go as far as putting an artifical RPM limiter on their motor so they can run a smaller pulley for idle, but that'll get you killed on the road in a daily driver. Those small motors build all their power from high revving. I would never limit my RPM on a small motor like that, that's very dangerous.

I wonder if super caps or something like that would help you here. I'm not super familiar with them, but some others may be. I'm sure there's a way to mitigate this problem, to some extent.

I did some testing with a DMM and both my batteries are sitting at 12.6 with the car off and around 14.6/7 with it on. So in the end I think its high enough 90% of the time to keep the batteries charged without problem.

Next time I buy a car though its going to be bigger, American and the alternator will be on top, no more of this buried under the engine crap!

 

[Buck 5,000+ posts]

I did some testing with a DMM and both my batteries are sitting at 12.6 with the car off and around 14.6/7 with it on. So in the end I think its high enough 90% of the time to keep the batteries charged without problem.

Next time I buy a car though its going to be bigger, American and the alternator will be on top, no more of this buried under the engine crap!

Haha right! I understand the struggle. I've seen dudes so mad when they get their 300 amp alt and it doesn't even charge at idle. Those voltages seem fine to me, I don't see a problem there. Just charge your batteries every now and then I've you're dipping into them occasionally. Before I got an alt, I charged my 4 batcaps nightly.

 

[hispls 5,000+ posts]

Next time I buy a car though its going to be bigger, American and the alternator will be on top, no more of this buried under the engine crap

That's the spirit.

batteries are sitting at 12.6 with the car off and around 14.6/7 with it on

If they're a few years old you may want to have them load tested. Resting voltage isn't the best indicator of whether or not a battery is still serviceable. That said, alternator charging low at low idle isn't unusual and generally anything over 12V and your equipment should not be damaged.

 

[Bass Dad]

I know this has been a bit ago but maybe this will help. People tend to buy the biggest alt they can get for their vehicles but they don’t realize that those 320 and 370 amp alternators only make that much at cruising speeds and at idle the 240 amp versions make more amps. Also, I’d go get the correct belt Autotech should have told you the exact part number of the new belt you would need. I know mechman will but I haven’t dealt with Autotech any. If I were you I’d get the correct belt and a super cap bank then it won’t matter what you are getting at idle