AGM or Lead-Acid?

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dkamp

dkamp

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I have a Tuff Stuff brand Voltage Regulator(7545) and Alternator(8509RCDP). Until it gets to 1000RPM the voltage output is 12.3 to 12.5
At 900RPM it is 14.6 and at 1000RPM it is 15.1
Over 3 years I killed my AutoZone H7-AGM. This AGM normal sitting voltage should be 13.1-13.4 its only 12.3 and after it sits a few days it will not start the engine.
Testing with Tuff Stuff support they say the VR and ALT are working normally.

Since I need to replace my battery should I get another AGM or go with the cheaper Lead-Acid?
Does anyone have a preferred "Brand" that seems to last more than 3 years?
DKamp
 
dkamp said:
Until it gets to 1000RPM the voltage output is 12.3 to 12.5
At 900RPM it is 14.6 and at 1000RPM it is 15.1
Click to expand...
Ok I'm confused.
You say UNTIL 1000 rpm the voltage is 12.3 to 12.5; That means below 1000 rpm the voltage is as you say, right?
But then immediately after that, you say ;
1000 is 15.1, and
900 is 14.6
So what's up?
 
IMHO 15.1 seems a bit high.

Have you come to any reason why you have been killing batteries?

Is it bolted down correctly?
Is it exposed to excessive heat?
Is it in a daily driver?

The 15.1v could be part of the reason


My current O'Riley average battery is coming up on 6 years, and around 12,000 miles. (Longest lived battery I have ever had)

Most of my newer cars batteries last around 5 years, 7,000 to 8,000 miles per year.
 
AJ:
It usually starts increasing around 800.
I don't have a very good Tach, its only has a 2 inch face. sorry for the confusion.
Do you or others use AGM batteries?
 
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Dana67Dart:
Tuff Stuff support said 15.1 was ok. What should the max voltage be?
It is only driven once every two weeks for a pleasure cruise.
It could have been my cheap trickle charger. I just got another one last week.
 
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AGM, generally do not like over voltage. Someone on here recently posted an adjustable VR they found.

Do you know how to test for voltage drop to the VR? VERY important.

It is common, if the wiring has not been upgraded, to experience voltage drop to the VR, which CAUSES over voltage. This is usually/ mostly in the harness, but can also occur in the ground path. To check

Turn the key to "run" with engine stopped. Pick the nearest electrical point to the VR IGN terminal, usually the ballast resistor "run" line from the key

Stab one probe of your meter into the top of the battery + post and the other to the "run" terminal. You are hoping for a very small reading, the lower the better. Anything over .3--.4V (3/10 of one volt) look for the cause. With original wiring, the path of loss is fuse link, bulhead connector, ammeter, through it, out on the black wire to the welded splice, to the ignition switch connector and through the switch, out on the IGN1 "run" wire, back out through the bulkhead, and to the ballst resistor and branch off to the alternator field, VR IGN terminal, electric choke, if used, etc.

======================


To check the ground side, get the engine / bay/ battery warm and normalized, and run the engine on high idle to simulate low to medium cruise RPM. In your case, make sure it is actually charging.

Stab one probe into the top of the NEG battery terminal, and stab the other into the mounting flange of the VR, HARD to get through paint/ chrome/ rust. Once again, the lower the reading, the better. Zero is perfect.
 
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dkamp said:
Since I need to replace my battery should I get another AGM or go with the cheaper Lead-Acid?
Does anyone have a preferred "Brand" that seems to last more than 3 years?
DKamp
Click to expand...
I ran a Dry-cell Optima in the trunk for over 20 years. I disconnected it every fall and re-connected in spring. Dribbled a lil gas in the carb , and hit the key; click vroom vroom.
At point of sale it was the most expensive battery I ever purchased. Over time, it became by far, the most economical.
Eventually it failed to take a charge and had to be retired.
That battery absolutely did not care how many volts it did or did not get.
 
I like to see 14.5-14.7. 15 is a bit high to suit me. My diesel pickup had red top optima's in it when I got it, got decent service out of the second pair (1st pair replaced under warrantee). When they died, I replaced them with lead acid, less than half the price of the red tops, if they last half as long, im ahead. (They did). The Delco agm in my Camaro lasted almost ten years, my opel (with HORRIBLE battery access!) has a red top that's six years old and going strong. When it dies, it'll get another redtop.
Counterpoint; I recently had to put new batteries in the pickup, again put in lead acid instead of agm's. (Sam's club). The agm warrantee was no better than the lead acid, and had no more power, for $50 more, each.
 
BTW
I got a box of used regulators here, some from the 70s. When I was hunting for regulators back in 1999, I discovered that no two of them ran the same.
Eventually I got the idea to buy one of those fancy new "constant-Voltage" regulators. I swapped it in and threw the still working one, back in the box. Not too long afterwards, that fancy new CV regulator, ran up to 20 volts. Being far from home, I unplugged it and drove on battery until the voltage droped a lil less than normal, then plugged the faulty regulator back in... and so on, until I got home.
After I diagnosed the unit and condemned it, I reached into that box of old regulators, and installed the first one that fell to hand. That was way back in the mid 2000s. That Optima battery kept on trucking until 2022.
 
I just put two new AGM batteries I bought at Walmart in a couple of my cars. 3-years is as long of warranty and sadly about as long as newly manufactured batteries last today. I like AGM batteries myself and since there are more Walmarts with better hours than auto parts stores I choose to buy them there for $168 each.

Tom
 
Typical mopar alternator/voltage regulator output at low rpms especially when cold. They tend to not start charging to that 13.8 to 14.2 until 1000 rpms. I agree that no 2 VR are the same but the output at idle is almost always low because of the design of the alternator. I read there's a Ford cop car alt. that puts out at idle. If you are staying stock then you just need to live with it like so many millions of cars have. AGM do not like overcharging and need a different charger. Your trickle charger may not be functioning unless it's designed for AGM.
I recently saw an adjustable VR here. That may be the way to go or the constant output 14.1 V race only unit. I have 1 but have never used it on a street car. If you fix your max voltage output you can run an AGM. If not, acid/lead. Good luck and check your grounds!
 
I like Duracell (East Penn) convention lead-acid, bought them from Batteries+Bulbs for each of my 3 vehicles. Haven't yet had the funds to try an AGM but these Duracells are holding up well. I just didn't want something made by Johnson Controls which is any lead-acid you buy from an auto parts or big-box store.
 
How about LI batteries.
Screenshot_20230322-222925.png
 
I put an AGM Vintage style "MOPAR" Group 27, Red Cap, Turbo-Start in my 70 Cuda in 2013. Never disconnect it but I keep a quality battery maintainer on it over the winter or if I know I'm not going to drive it for a while.
I bought the Battery in late 2012 and put it into service January of 2013.
She still cranks like new every time. My typical running voltage is 14.4V-14.5V... "¯\_(ツ)_/¯"
 
I run AGM in everything I can get them for. 66, 67, 68 Barracuda red top, 2001 Cherokee Diehard Platinum, 2009 Challenger R/T 6 speed. They usually last 10+ years for me.
 
I check for voltage drop and did have .74 Volts between the Battery and the IGN connection on the Voltage regulator.
the drop was in the Ignition switch on the column. Replaced it and now it is .51 Volts
Still testing all the connections between the two points.
 
Ever since we started recommending AGM batteries for our engines at work, I have run them in all of the toys (2 hot rods and 2 muscle cars) and they have been flawless for me. Daily car and truck have standard lead acid. That is just because the car has a good battery yet and the truck takes 2.
 
dkamp said:
I check for voltage drop and did have .74 Volts between the Battery and the IGN connection on the Voltage regulator.
the drop was in the Ignition switch on the column. Replaced it and now it is .51 Volts
Still testing all the connections between the two points.
Click to expand...
One way around that is to add a relay. Break the "run" wire coming into the engine bay, and use the firewall end to trigger a Bosch style relay. Feed the power contact with a fused/ breaker wire off a main point such as the starter relay, and connect the switched contact to the engine bay end of the "run" wire. This will relieve the key of stress, and any drop in there won't matter much

Any drop in either the ground or hot side will ADD to the set point charging voltage. So if the VR is correctly working at 14.2, and you have .74 drop, then it will charge at 14.95

Also that drop can CHANGE (get worse) under some conditions, as the contacts in the key heat up, under load, etc.
 
The O'Reilly AGM batrees are evidently pieces of ****, because our warranty return rate for AMGs was over 2 to 1 for lead acid batrees.
 
RustyRatRod said:
The O'Reilly AGM batrees are evidently pieces of ****, because our warranty return rate for AMGs was over 2 to 1 for lead acid batrees.
Click to expand...
I would bet that a part of that is that the owners weren't charging the agm's properly, or with the right charger. A discharged agm won't come back without an agm charger (cheap, at HF) or a parallel lead acid to get the LA charger started.
I think I paid $25 for my AGM/LA charger. Saved at least one $250 red top from the scrap heap for no reason.
 
33IMP said:
I would bet that a part of that is that the owners weren't charging the agm's properly, or with the right charger. A discharged agm won't come back without an agm charger (cheap, at HF) or a parallel lead acid to get the LA charger started.
I think I paid $25 for my AGM/LA charger. Saved at least one $250 red top from the scrap heap for no reason.
Click to expand...
I've always read and heard that, but they come back with an alternator.
 
33IMP said:
True, if they can get the car started. A truly dead agm might not jump start.
Click to expand...
When I find an AGM with the warranty the Motorcraft batteries have, I might get one. They all have a ten year warranty. First three is free replacement, the next seven is pro-rated. Plus, when you warranty one out, the warranty starts all over again.
 
I never had any luck with an AGM in the ATV or snow plow, so I'm back to using lead acid
The newer cars and trucks have the factory battery.
I have an Optima in the barracuda, but that's not a fair test for battery life. It never gets ran with any accessories on and not very much.
 
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