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Kirkham Motorsports

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  • 1 Post By Argess

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Old 05-24-2022, 07:01 AM
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Default AGM vs traditional flooded battery

I've been thinking of replacing my battery with an AGM one, however I'm not sure if my 1960s style Ford alternator and regulator will over or undercharge it and from what I understand, AGM batteries are susceptible to damage from this. Opinions welcome. T-Y.

ps: I can't seem to find a battery with end tabs to suit the mounting and those J-hooks with wing-nuts look they will be a pain to fiddle with under the fender, so I'll stick with a 24F7 and use a strap around the battery and tray.
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Old 05-24-2022, 07:09 PM
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if the output of the alternator is too high, you will shorten the lifespan of the AGM. I would not spend the additional money on an AGM in our application unless it was a modern powerplant with a charging system that adjusts output as needed.
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Old 05-24-2022, 07:31 PM
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I run an AGM in my ERA because I don't want to have to check the fluid level. I have to remove the RR wheel to access the battery compartment. I run just a one wire 100a alternator with its internal regulator and have not had any issues. My 2˘.
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Old 05-25-2022, 05:54 AM
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I use a cutoff on my under-hood acid flooded battery and just replaced it after 10 years. It is a pain to replace through the wheel well but every 10 years isn’t bad. - except I’ll be 80 then, bummer.
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Old 05-25-2022, 08:15 AM
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I was mostly interested in the AGM as it is maintenance free and won't spill if tipped over. The battery in my ERA is under the right front fender. You have to take the valve cover off to remove or install it. For installing it, the battery slips in at an angle and finally gets in place on its side. Then you rotate it upright. Checking the water level of at least 3 of the cells is difficult too. So the issues are similar to Karl's.

As I can no longer find the proper 24F7 battery with the hold-down side tabs, I'm free to choose something else, so I was investigating the AGM batteries but research showed some issues, so I thought I'd ask here.
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Old 05-25-2022, 08:20 AM
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DanEC, You've had very good luck with your battery, enjoy! Our Arizona desert is extremely harsh on flooded batteries. They have been greatly improved the last few years and now sometimes last more than 2 or 3 years as in the past.
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Old 05-25-2022, 12:56 PM
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I am using a Deadnutson alternator with AGM batteries and I have had no issues in 3 years:
https://www.deadnutson.com/1965-1971...e-alternators/

In my limited experience, I think you need an AGM specific battery charger / tender for AGM batteries, but my standard alternator has worked fine.
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Old 05-25-2022, 02:28 PM
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Isn't the Optima Red Top AGM class? I ran a 2x6V configuration all the time I owned my Cobra and never had any alternator or other charging issues.

In addition the Optima I had in my Ford GT lasted over 7 years being on a Battery Tender. (The Ford GT battery is an Optima Red Top with a Ford label.)
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Old 05-25-2022, 03:35 PM
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I've been using the Optima 35R in my ERA with the battery under the right front fender. It does have the end tabs to allow the ERA provided battery hold down to be used (although I did have to put a spacer under the battery). I like it so much better than the old lead acid battery I used to use. The lead acid battery would "sweat" acid which would drip down and stain my stainless pipes. I've had the Optima for 3-4 years with no problems (and I use a 120A 1-wire alternator).

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Old 05-25-2022, 07:19 PM
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Quote:
Originally Posted by twobjshelbys View Post
Isn't the Optima Red Top AGM class? I ran a 2x6V configuration all the time I owned my Cobra and never had any alternator or other charging issues.
Same for KMP259 for and we use a single wire Alternator..
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Old 05-26-2022, 06:08 PM
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I’ve done a little more research and as far as I’m concerned, all those “positive” attributes of an AGM battery are all unfortunately outweighed by the following “negative” comments I found on the net:

1/ https://www.repairsmith.com/i/blog/agm-vs-lead-acid/

Flooded lead acid batteries are much more tolerant to overcharging than AGM batteries. The sealed aspect of AGM batteries makes them more prone to thermal runaway, which can be triggered by overcharging. Even if you discount thermal runaway, overcharging will shorten an AGM battery’s lifespan faster. So, when charging an AGM battery, use a regulated battery charger to control the voltage and current going into the battery.

Note: Thermal runaway is when a battery generates too much heat than it can dissipate. The battery will dry out and melt, release toxic chemicals, and cause fires or explode in extreme cases. Nearby batteries will be affected and may result in a domino effect.


2/ https://batteryuniversity.com/articl...-glass-mat-agm

As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive.

AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F).


Yes, I’ve never heard of this happening, and I know many Cobra owners use an AGM battery, but I’m sort of a low risk fellow at times. Too bad though. I almost bought one.
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Old 05-27-2022, 04:54 AM
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Argess - are you dealing with an ERA? If so you should be able to remove the battery through the wheel well after removing the tire and the liner panel, and without tipping. Possibly early ERAs didn’t have this feature - not sure.
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Old 05-27-2022, 06:26 AM
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That was my answer...... I work in the industry and deal with alot of batteries, do not even get me started on Optima batteries, I would never own one. Seen too many issues in applications.


Quote:
Originally Posted by Argess View Post
I’ve done a little more research and as far as I’m concerned, all those “positive” attributes of an AGM battery are all unfortunately outweighed by the following “negative” comments I found on the net:

1/ https://www.repairsmith.com/i/blog/agm-vs-lead-acid/

Flooded lead acid batteries are much more tolerant to overcharging than AGM batteries. The sealed aspect of AGM batteries makes them more prone to thermal runaway, which can be triggered by overcharging. Even if you discount thermal runaway, overcharging will shorten an AGM battery’s lifespan faster. So, when charging an AGM battery, use a regulated battery charger to control the voltage and current going into the battery.

Note: Thermal runaway is when a battery generates too much heat than it can dissipate. The battery will dry out and melt, release toxic chemicals, and cause fires or explode in extreme cases. Nearby batteries will be affected and may result in a domino effect.


2/ https://batteryuniversity.com/articl...-glass-mat-agm

As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive.

AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F).


Yes, I’ve never heard of this happening, and I know many Cobra owners use an AGM battery, but I’m sort of a low risk fellow at times. Too bad though. I almost bought one.
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Old 05-27-2022, 07:41 AM
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My last two Interstate Mega-Tron batteries have both lasted 7 to 8 years in my ERA and probably would have lasted longer had I not broken down and replaced them. And I performed no maintenance on them whatsoever during all that time. Never even looked at the water levels. I would occasionally peek at the terminals to see if there was an abundance of that funky white stuff on them, but there was never enough to warrant doing anything so that's it. I wouldn't replace the battery in there with anything else.
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Old 05-27-2022, 08:33 AM
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I've had a similar experience Patrick. I think I got my Cobra on the road back in 1997 and have just now had my 2nd battery fail. Like you, I never checked the acid/water, however on this second battery, the level was down almost a half inch in each cell. That didn't do it any good even though it lasted a long time.

As previously mentioned, my issue has been all new batteries do not have the clamp down end tabs. Also manipulating the battery into the battery tray might result in spillage with a vented battery. (Dan: mine is an older ERA and doesn't have that access panel)

I have a strap and a parachute buckle to fix the first problem. I'll just have to check for chafing of the strap for a while. The latter issue is to go with a sealed flooded lead acid battery.

I still havn't completely given up on AGM as so many people claim success, and to be truthful, I can't see an extra 1/2 volt from the alternator/regulator causing much of a problem by generating significant heat. Even if the float draw was 5 amps, that's only an extra 2.5 watts. Then again, I'm not sure what happens when you exceed the float voltage on an AGM.

There's a lot of conflicting information. Many articles claim not to have an AGM battery in the engine compartment due to heat, but other articles state that an AGM battery handles heat better than a traditional lead acid battery.
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