What is your average alternator voltage above idle w/accessories running (at the battery/downstream of the diode isolator)? AGM's need 14.4v or more to take a full charge, and lots of cars don't come close to that, or use dynamic voltage to conserve MPG's...

 

I use Xs-power D series in my accord. I've had it a couple years with no issues.

AGM's need 14.4v or more to take a full charge,

I didn't know this. 😕 my Accord charges 14.4 only at night with the lights on. During the day with no accessories it will sit in the 12s, with the AC on in the 13s. Wonder if it's degrading the battery.

 

An AGM starting battery can get by with a bit below that - but AGM's absolutely require more than standard flooded cell batteries...

You can use a diode to increase the alt output by .5v...

 

On my Nissan Titan there’s a sensor (Hall effect?) that encompasses the battery ground wire. It’s said to reduce voltage going to the battery but I never heard it explained as for MPG purposes. I suppose it makes sense though, electrical loads do put some physical strain on the alternator.

Some guys shunt this by putting some aluminum foil between the wire and sensor. Didn’t know AGM requires a higher charge rate to maintain health.

Good to know removing it can assist charging an AGM. I wonder if doing so would harm a flooded acid battery?

But yes to OP’s query the Optima batteries (red and yellow) are rumored to have taken a dive in quality. Odyssey seems to be the better now but usually at significant cost.

 

It's not the "Charge Rate" but simply the voltage potential needs to be higher for AGM. Not more power - just more voltage to get the power (at whatever charge rate) into it.

My understanding is all of the Alternator voltage regulation below 14v is directly for MPG, but I may be mistaken. That sensor on the ground might be a crude ammeter just to let the charging logic system know what voltage to set the alternator's regulator at based off realtime load demands...

For cars that simply run lower voltage (and don't dynamically regulate below 13v or so), you can use a diode in the Alternator's sense fuse that will trick the system into putting pout .5v more to the battery. Simply drops the B+ feedback into the regulator by .5v, so the alt will put out .5v more than stock. My 4Runner needed this as it ran in the mid 13's, and I added an AGM. With the diode, I was always above 14v. My GX is pretty close to 14v most of the time - and I don't have an AGM - so I haven't bothered with the diode.

And I have also heard many reports of lower quality from Optima's the past 10 years...

 

Not entirely for MPG - although that is a consideration as manufacturers continue to look for ways to eliminate or reduce adiabatic losses. The reality of microprocessor driven voltage regulation is that the batteries need this regulation. Continuous maximum voltage charging can cause all kinds of problems and all batteries benefit from some cycling and then floating at a lower charge voltage to prevent sulfation and other surface charging issues. Without going into a battery charging dissertation, is it sufficient to say that AGM batteries have a higher charging threshold and don't suffer the same over charging maladies that regular Lead Acid batteries do?

I'm running dual AGM setup but TMK the Mopar Voltage Regulation is a steady 14.4 VDC by design (mine seems to run 14.6 when cold and drifts down to 14.3 during the summer months when engine bay thermal soak sets in - running a 185 degree thermostat has helped that dramatically.)

 

Optima Batteries took a huge dive when they were taken over by Johnson Controls and then in 2019 they diverged into Clarios and have gotten even worse. Clarios simply cut's too many corners in the tolerances, QC and production variability.

Northstar and Odyssey are the 2 most recommended battery makers now and with dual battery setup you should look for a Low Internal Resistance Audio Battery for the Trunk that more closely approximates an Electrolytic for faster current sourcing. AGM Starter batteries have some internal resistance engineered in for maintaining a higher voltage but with current driven amplifiers the low internal resistance of an XS Power or Stinger Audio Battery has definite advantages and you don't need huge amp hour rating unless you do a lot of engine off listening. A smaller audio battery that can deliver current faster is preferred over a huge A/H Rating.

 

Fantastic point. Low source resistance (DC, or impedance if AC) is generally a good thing for most situations - and certainly with a power supply. Even your home's 120VAC "source impedance" can be improved for multi-kW home-audio needs. It's easier to pull power from the lower source resistance (or impedance).

If you Alternator is powerful enough to average out the dynamic music load and keep your battery happy, then the need for large batteries and huge reserve times are unnecessary.

Not entirely for MPG - although that is a consideration as manufacturers continue to look for ways to eliminate or reduce adiabatic losses. The reality of microprocessor driven voltage regulation is that the batteries need this regulation. Continuous maximum voltage charging can cause all kinds of problems and all batteries benefit from some cycling and then floating at a lower charge voltage to prevent sulfation and other surface charging issues. Without going into a battery charging dissertation, is it sufficient to say that AGM batteries have a higher charging threshold and don't suffer the same over charging maladies that regular Lead Acid batteries do?

I'm running dual AGM setup but TMK the Mopar Voltage Regulation is a steady 14.4 VDC by design (mine seems to run 14.6 when cold and drifts down to 14.3 during the summer months when engine bay thermal soak sets in - running a 185 degree thermostat has helped that dramatically.)

I'm not a battery expert by any means. It is my basic understanding the AGM's require a higher voltage to accept a full-charge than a regular flooded cell type. I believe lots of the same benefits of microprocessor controlled charging are applicable to AGM's, but the logic needs to know it's charging an AGM and thus will need a higher voltage.

The maintainers/chargers obviously have selection for battery type - I'm not aware of any cars that let you select the battery type accordingly for their dynamic regulation. But an AGM will be undercharged and pre-maturely degraded unless charged/maintained at the proper voltage. This is likely why so many experience poor lifespans from very pricey AGM's. And it seems like most with AGM's need to use maintainers just to keep the battery relatively happy. In the end, one's audio system might actually end up with less power because the AGM is only 50% charged all the time!

I'd assume a stout 14.4v from your Mopar is fine - especially bumping to 14.6 when cold. It's when the AGM NEVER sees a full charge from a <13.5v electrical system that it will degrade and not provide full CCA or rated lifespan. Then people chase their tail with an expensive alternator upgrade to cure the low-regulator-voltage issue causing their AGM's to fall flat.

I appreciate SPL - alot! 4kW in my last install, and 2.1kW in current install. But in a modern car with a 150A-250A alternator, I have never needed anything more than good regulated SMPS amplifiers and proper gauge wire with a heathy battery. And, of course, a charging system that is properly regulated for the battery it is charging...

This was much different in the 90's and my pile of old Rockford POWER series amps (Still have my POWER1000, POWER300 and Punch150 in storage!). They were linear PSU and unregulated. A "Stiff and Stout" power supply voltage was paramount to getting full power. Not true today with regulated SMPS amps...

 

The X2 Power batteries from Batteries Plus are a good option. They are built by Northstar but is a little cheaper than an Odyssey battery. It looks like it is about $350 for a group 34.
I have a couple of cars that, unfortunately, are living on maintainers so I've just been running Walmart lead acid batteries and replacing once out of warranty. I got tired of replacing pricier AGM batteries on cars I rarely drive.

 

Does anybody know FULL THROTTLE batteries?

 

I really like the x2 power batteries mentioned here. Have one in my boat and it has never let me down. Used to be a die hard optima fan but no more with the quality issues.

 

Yeah Optima batteries went downhill many years ago. Back around 20 years ago I put red tops in every vehicle I drove and they were rock solid. Even had one that I bought in '03 and it lived through 4 different vehicles until early 2009 when it started getting weak. Then the price shot up and the quality went down. Every red top I bought since then would last maybe a year, or two, at most before they would fail.

 

I can only give a simple mans description of the batts and review. Ran a red top in a truck for years never a problem. One morning truck didn’t start, this is like 6 years or so with red top in truck. Get another red top, dies in about a year. Replaced under warranty, replacement red top dies in less time so moved on from brand.

 

Greetings folks! For as long as I can remember I've always used Optima Red Tops as my starter battery. However within recent years I've had to replace them quite a bit. In this car in particular the red top was replaced twice under warranty & once again its failed, but now its up to me to replace. What are you guys using these days up front? I have a yellow top in the trunk with an isolator installed and that's been working wonderfully. This car is garaged quite a bit as I don't drive it during the rainy season, so I want something stout that has a decent shelf life and holds its charge well. I use a Nuco Genius 5 on the starter battery & a genius10 on the trunk battery, so while not in use the battery is maintained. Any suggestions? I usually run a group 34/78 or 25/75 so I can have two sets of terminals. The vehicle OEM battery is 590CCA, so anything rated close to that would be great.

Optima was formerly owned by Johnson Controls, they were good back then. Now someone else owns them and they suck.
I have an older Yellow Top under the hood and an XS Power in the back.

 

Years ago I put aoptima battery in my Saab, worked perfectly for 8+ years until I sold the car.

a few years ago I put one of their batteries in my jeep, just out of warranty it crapped out on me…. As people stated they are not what they use to be after being bought out and I believed moved out of the country for manufacturing.

 

I have had good experience with Odyssey. You can also get hold down kits from Odyssey or on Summit

 

I now have had two Optima batteries in a 3-year period, both dead.....I'm tired of it!!

 

Ever since Johnson Controls bought them the quality has gone down hill . I used to use them all the time years ago and most of the time I got 7-8 yrs out of an original Optima, no where near the same anymore

EDIT just noticed this is old post