The Average 6 Volt Group 1 Battery Life

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J1MGOLDEN
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The Average 6 Volt Group 1 Battery Life

Post by J1MGOLDEN » Sun Nov 16, 2025 2:44 pm

Are there any opinions on how long a 6 Volt Group 1 Battery should live, if it is seldom used, but left in the vehicle, or which battery is the best??


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Re: The Average 6 Volt Group 1 Battery Life

Post by Moxie26 » Sun Nov 16, 2025 2:53 pm

Batteries always last longer when not in use being charged by a certified trickle charger, no matter what brand of battery, the trickle charger is a great help making the battery last longer.


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Re: The Average 6 Volt Group 1 Battery Life

Post by John kuehn » Sun Nov 16, 2025 3:07 pm

Model T’s among other older cars and tractors use a Group 1 6 volt battery. I’ve used the ones avaliable at Farm and Ranch stores and I’ve had them last as long as 4 years down to 18 months only because I didn’t check the build date on the battery! I use a trickle charger for my T’s since they aren’t used as much as the 54 NAA Ford tractor that’s used fairly regular. On the other hand the battery in my 76 656 IHC Tractor is 12 volt and is 9 years old and still going strong and it’s used fairly often but not a whole lot.

I’ve learned to ALWAYS check the date when the batteries are made no matter where you buy them or what brand. That makes a difference on any brand.


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Sun Nov 16, 2025 3:52 pm

Do check dates on new batteries. They aren't all new! How long a battery lasts depends on a great many variables. A battery that is of adequate size for the job it is intended to do will last longer than an undersized battery. A well-regulated charging system will extend battery life by avoiding overcharging and undercharging. Some old vehicles, like Model Ts, and many old tractors rely on the operator to manage the charging system to the best advantage. It's best to have a battery tied down to prevent it bouncing around and being subject to excess vibration. Keeping the fluid level up to spec is helpful. A starter and related parts in good order will protect a battery from excess current draw and heavy charge/discharge cycles. A well tuned engine that starts easily will do the same. As noted above, batteries in storage need to be charged from time to time or kept on a good maintainer. I'd avoid jump starting, especially with an older battery. Both extreme heat and extreme cold are hard on batteries. Keeping a battery clean will prevent self-discharge and corrosion. Generally speaking, cheap batteries don't last long, and usually aren't a bargain. Trying to get by with an old, weak battery can be very hard on the starter, and wind up costing more than a good new battery, besides causing no-starts at inconvenient times and places.

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Re: The Average 6 Volt Group 1 Battery Life

Post by Mark Nunn » Sun Nov 16, 2025 4:27 pm

I was having persistent low-voltage problems last spring. I bought a new Duralast battery last April. The build date was 10/23. While somewhat better, the problem continued. My April battery dropped from 6.3 to 3.3 volts when the starter was engaged. I replaced it yesterday under warrantee. Autozone tested it and was bad. It should have been 575 CCA but tested at 225. Yesterday's new battery has a build date of 11/23. It tested as good. Starting the car today with a full charge dropped battery voltage from 6.25 to 4.5 with the starter running. I think that is still too low. Is losing 1.75V acceptable? The engine would spin but not fire until I let off the starter button. Starter, rather than a battery problem?

Sorry for hijacking the thread. I just now came in from the shop in frustration.


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Re: The Average 6 Volt Group 1 Battery Life

Post by Allan » Sun Nov 16, 2025 4:31 pm

"or which battery is best?" An Optima red top is my go to. More expensive initially, but I have two in intermittent service. One is 9 years old, the other, 7 yo. Amortised over that length of time they turn out to be the best bet economically.

Allan from down under.


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Sun Nov 16, 2025 4:39 pm

Mark, your problem could be excess current draw from the stater, or it could be a cable/ground issue. Or it could be the battery. In my opinion, a new battery is no older than 6 months. Fresher is better. The battery needs to be the correct size for the application, or a size or two larger, if space allows. Cheap batteries are rarely cheap.


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Sun Nov 16, 2025 4:40 pm

My T has a Red Top in it that is over 11 years old. Still starts. The car has a stock generator and cutout.


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Sun Nov 16, 2025 4:50 pm

If the engine starts when the starter switch is released, it's probably because the system voltage goes back up. Voltage drop when cranking is normal. Exactly how much is acceptable, I don't know, but I think it can exceed 1 to 1.5 volts in a 6 volt system. Anything that makes the engine harder to crank will increase the voltage drop, and a tired, or undercharged, or undersized battery will show a higher voltage drop as will a vehicle with starter, starter cable or starter switch issues.
Well tuned coils will perform better at lower voltages than coils that are not in good working order. Clean plugs, properly gapped, will help.


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Re: The Average 6 Volt Group 1 Battery Life

Post by John kuehn » Sun Nov 16, 2025 5:54 pm

The battery suppliers to the stores that carry them are SUPPOSED to rearrange the batteries according to build date age and move them to the front while the new and newer ones go towards the back of the line. What I started doing is to go to the back of the line and that’s usually where the newer build date batteries are.
The same thing is done on perishable products in grocery stores.
The Group 1 6 volt batteries don’t move as fast as 12 v batteries and that’s another reason why some don’t last long because the build date wasn’t checked. Using a trickle charger will almost always help with longevity BUT not so much when it’s an older build date battery to begin with. In my area I called Auto Zone checking for a 6 V Group 1 battery and the parts guy had never heard of one using that ID.

He did look in the back of the store and did find one but it wasn’t marked Group 1 6 Volt but another ID number. I decided to get one at Atwood’s that was less than 5 months old. And it was in the back of the line.

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Re: The Average 6 Volt Group 1 Battery Life

Post by varmint » Sun Nov 16, 2025 6:24 pm

The Duralast battery only has a 1 year warranty, if that says anything.
Vern (Vieux Carre)


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Sun Nov 16, 2025 6:34 pm

It used to be that 1 year warranty batteries were low-price "replacement" units favored by tote the note used car dealers. That may not be true anymore, since batteries generally last longer these days and keeping costs down to attract buyers is common. Warranties are not free... they are insurance, and they carry a cost/liability to the warrantor.


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Re: The Average 6 Volt Group 1 Battery Life

Post by Stu Tomlinson » Sun Nov 16, 2025 6:59 pm

I have had one 6v Optima battery that lasted over 10 years without being kept on a maintainer for long periods of time.

I had another standard 6v battery last for 8 years but was continually kept on a maintainer.

Without maintainers I have seen battery life as short as 3 years.

My opinion is that Optima has a long life and is the best battery, and having a maintainer is the best way to go.

In each of these cases, each of these batteries have been in cars stored in a garage the is stays an above freezing at all times.

Stu


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Mon Nov 17, 2025 1:18 pm

Batteries seem to benefit from "exercise". Sitting for longer periods of time while partially discharged seems to be very hard on them, and sitting around deeply discharged is ruinous. The Li and LiFe types may be more resistant to sitting idle and to self-discharge than wet lead-acid types. AGMs seem to do better than the flooded lead acid ones.

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Re: The Average 6 Volt Group 1 Battery Life

Post by JohnH » Tue Nov 18, 2025 2:35 am

I've had about 8 years out of standard 6V batteries. That is with them on a maintainer whenever the car is parked at home. The beauty of the Model T of course, is you can still drive around with a worn out battery, if you're prepared to crank start it. My most recent battery is a Red Top Optima, which I've had for almost 6 years. I wouldn't go back to standard wet lead acid batteries now, having used that. The starting is better since it has lower internal resistance, and it has maintained that without deterioration so far. Also of course is no acid film all over everything, and the need to check the water. The Optima is much more expensive, but worth it in the long term.


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Re: The Average 6 Volt Group 1 Battery Life

Post by TXGOAT2 » Tue Nov 18, 2025 1:35 pm

The Optimas are clean, lightweight, and long-lasting. They probably don't have the reserve capacity of a big wet cell battery, but they can give a short burst of high current, which makes them an excellent starting battery. I believe that any type battery used in a Model T could be expected to last longer if the car was equipped with an accessory voltage regulator.

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