Alternator intermittently charging?

Check your owners manual. I don't know much about alternators, but I know in my 2007 Yukon, the owners manual says the alternator will do this based on things like power demands, battery voltage, temps, etc.

No way to make it run 14.5 all the time. That is just not possible, only option would be to do a Big 3 upgrade and upgrade the cars alternator with a bigger unit in order to make sure you don't experience as bad of a drop.

I never even considered trying to bypass that, nor do I have the knowledge to say if that's even advisable.

Coolhand20th said:

No way to make it run 14.5 all the time. That is just not possible, only option would be to do a Big 3 upgrade and upgrade the cars alternator with a bigger unit in order to make sure you don't experience as bad of a drop.

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If you're referring to a drop in charging voltage, I doubt the big 3 upgrade would help. Mine only had the factory Bose system in it, but even without any major power consumption voltage would still dip well below 13V regularly. From my understanding, it's supposed to do this at times and sounds like it was to help protect the battery from excessive wear and possibly help with fuel mileage, but don't quote me on that. The manual didn't give a lot of specifics.

If you're talking about a voltage drop from a big bass hit, then I would agree the big 3 update may help, depending on how much power the system is using.

Ven0m said:

also, how would my battery ever reach its full charge of 13.1v if the alternator is usually at 12.8? lol

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12.5V is the normal resting voltage when fully charged, so that's about right. Charging voltage is higher because the charging source (alternator) must be higher to allow the current to flow. It's like trying to fill a bucket of water from another bucket via a hose. If the filled bucket is higher than the empty one, water will flow you the empty one. If they are at the same level, water will fill the empty one until both are equal. You can think of the height difference as the voltage difference between the alternator and battery. If the alternator charged only to 12.5 V, the battery would never reach its full charge, just as if those two buckets were on the same level.

I haven't used an Optima since the early 2000's. If they are designed to run at 13.1V, I'm not sure if it will be possible to get it there without some extensive work. Maybe others can let you know if 12.5-12.8V is ok with it, but I'd also check with Optima themselves for an official answer. It could just be a moot point if things are working fine and they are ok with it in these variable charging systems.

Ven0m said:

Ok thanks for your help, i wonder if theres a way to set resting voltage to 13.2 in an ecu tune or something. oh well it is what it is i guess.

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I doubt it, its probably controlled by one of the many BCM's in cars these days. The ECU only controls fuel and spark.

Optima batteries are garbage anyway, and way overpriced. Google search if you wanna know why. This has been discussed/brought up many times.

You might have a PCM which will need to be disabled to receive the full voltage stability from the alt. OR....you have a lose connection somewhere causing your issue.

Mooncatt said:

Check your owners manual. I don't know much about alternators, but I know in my 2007 Yukon, the owners manual says the alternator will do this based on things like power demands, battery voltage, temps, etc.

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Doesn't know much but replies anyway lol.

Owners manual isn't gonna help any btw.

Boomin_tahoe said:

Doesn't know much but replies anyway lol.

Owners manual isn't gonna help any btw.

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I found out about this possibility BECAUSE of my owners manual. I made it clear that this was only one possibility and turns out he owns a GM vehicle as well, making my first reply even more valid. So why not knock it off before you dig that hole deeper?

Dig that hole deeper? Well he is right in all honesty a owners manual doesn't really tell you squat about a vehicle.  And as I said before doing a Big 3 upgrade and going to a bigger alternator & a battery in the rear is going to help stop some of the voltage drops even without a big bass hit as it will keep the battery at fully charged and with said bigger alternator it will put out more of a load overall. Also an alternator doesn't doesn't have squat to do with mileage, idk where you would come up with that but no just no, but hey what do I know I'm only ASE certified in multiple areas my dad was only a machinist for close to 40 some years and only been through several schools as well like him but w/e.

AND yes optima batteries are complete garbage and vastly overpriced.

One of the better batters out there shockingly is the Ever Start Plus Battery. And FYI people there is only 4-6 battery companies through the ENTIRE world! Everyone thinks that each battery name is owned separately and that is just not true. It is like buying a refurbished stuff in auto parts there is only iirc 4 companies that refurbish auto parts and what they do is just slap a different sticker on the box. The other difference is yes some have better quality parts put back into them and the length of the warranties and that is all. Trust me on this, between the mechanic stuff I did I was also parts manager at a few different big name auto parts and diesel truck parts companies and saw said factories myself.