Anybody install a diode to boost alternator voltage for your AGM batteries?

[19963.4lsr5]

Any starting battery left below 80% will cause it to start to sulfate. Too long like that it will harden and reduce the capacity of the battery.


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[Endlessblockades]

I have done amazing things with my little NOCO Genius 10(?). I've had it for a couple years and revived batteries in vehicles with years of weeds growing in the engine bays. It will easily recharge a battery that is at 1 Volt and can even resurrect a zero volt battery with a little work. Can be used as a tender for AGM and deep-cycle and has a desulfate repair cycle too. Works with every battery type. Cheap and small. Sales pitch over, sorry.....

 

[Devbot]

AGM claims to last 2X longer

Those look sick but you can drop $1000 on a Dakota battery if you're not careful. I start to wince north of $200.

Mine lasted less than 8 months before getting a dead cell :smash:

One thing I learned from my father in law. If you not using a lead acid battery. You keep it on a battery tender. He had batteries last 10 to 13 years or so on all his equipment. All the lawn mowers etc lasted a alot longer on battery tenders. I was shocked at first. But it really makes sense as keeping them fully charged is alot easier on the plates.

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We just replaced the battery on our CJ7 last winter, old batt was dated January 2009 :trophy: It was still going strong too, even did a load test before replacing it; it was only replaced because I got a free replacement after my AGM died but I had already bought another batt by that point

 

[Late_Night]

Yeah, I installed one, but the cold idle voltage was close to 15 volts so I took it out.

Cold idle without the diode was around 14.5, so I am going to check the "hot" charging voltage and see if it is below 14.8 which is the max charging voltage recommended by East Penn for their AGM batteries.

I may also try to figure out which diode will give me a 0.3 volt boost.

I also may just say screw it since the charging voltage seems to be in spec of 13.8 - 14.8 volts... and screwing with things that ain't broke usually causes problems.

The diode is GM P/N 12135037.

 

[pluton]

Yeah, I installed one, but the cold idle voltage was close to 15 volts so I took it out.

Cold idle without the diode was around 14.5, so I am going to check the "hot" charging voltage and see if it is below 14.8 which is the max charging voltage recommended by East Penn for their AGM batteries.

I may also try to figure out which diode will give me a 0.3 volt boost.

I also may just say screw it since the charging voltage seems to be in spec of 13.8 - 14.8 volts... and screwing with things that ain't broke usually causes problems.

The diode is GM P/N 12135037.

Charging voltage of 13.8-14.8 ain't bad...maybe you some kind of magic alternator/voltage regulator! As you will recall from earlier in this thread, I installed the HKB variable diode, and set it at +.6V in the spring of 2022. I left it at the +.6V position all winter, including several weeks of work in Lax Vegas where it was routinely ≈32ºF in the mornings. The voltage on the Scangauge never went above 14.9V at cold start, and always quickly came down to "normal" levels as the engine warmed up. I have found in the subsequent year that the battery stays more fully charged even after a week of around town short trip driving. Right now, I can't drive the 4Runner due to a foot operation, so I got a Renogy solar trickle charger 10W Solar Battery Charger and Maintainer | Renogy Solar which stays hooked up and gets about 5-7 hours of sunlight every day.

 

[Late_Night]

Charging voltage of 13.8-14.8 ain't bad...maybe you some kind of magic alternator/voltage regulator! As you will recall from earlier in this thread, I installed the HKB variable diode, and set it at +.6V in the spring of 2022. I left it at the +.6V position all winter, including several weeks of work in Lax Vegas where it was routinely ≈32ºF in the mornings. The voltage on the Scangauge never went above 14.9V at cold start, and always quickly came down to "normal" levels as the engine warmed up. I have found in the subsequent year that the battery stays more fully charged even after a week of around town short trip driving. Right now, I can't drive the 4Runner due to a foot operation, so I got a Renogy solar trickle charger 10W Solar Battery Charger and Maintainer | Renogy Solar which stays hooked up and gets about 5-7 hours of sunlight every day.

Maybe magic! Yes, previous post was noted, appreciate the info, and I always trust but verify. The alt is 27060-62160-84 and I fried the rectifier a few weeks ago, then replaced it with an aftermarket rectifier. Running 2 awg wires. Nothing too radical.