12v Battery vs 6v Battery requirements

[BRENT in 10-uh-C]

I have a brass T in the shop that presently has a 12v Group 121R battery rated at 550CCA and a T starter & later hogshead retrofitted. Space under the back seat is very limited so we are looking at a way of minimizing space. This starter is mostly used when emergency starting the engine (-stalled the engine in traffic, or when hand-cranking is inconvenient). Also, the battery will be used to power LED lamps for a short period of time (i.e.: less than 30 minutes from a show or home from dinner). I am looking at Lawn & Garden batteries that are used in 3 cylinder diesel garden tractors that have 350CCA. While I realize that the length/duration of cranking time would not be as long as it would be with a 500CCA battery, or maybe the starter would not spin the engine as fast, ...but for an engine that would normally start easy enough after 2, 3, or maybe 4 pulls with the hand crank, what would we be giving up with using the smaller 350CCA battery in lieu of a 500+CCA battery? Do you think that would work in this application??

TIA

[J1MGOLDEN]

Most people don't notice the 6 Volt and 12 Volt battery size is a little taller than the 6 Volt, but otherwise the same physical size.

The real difference is you have six more cell walls and three more cell partitions, but not near as many of the inside parts required to make the electricity.

So, if your engine does not start right away, you have to crank anyway.

[George Hand]

Brent, is there a reason a battery bracket from a factory battery car cannot be used? I believe they will fit and only would require mounting holes in the frame. On my T I keep here in Florida it has a gp. 26R 12v with 540 cca. & fits in place of the gp.1 6v. It seems to do the job for me. George

[Steve Jelf]

I switched to a 12 volt battery in my 1915 runabout. It wasn't for
starting, but for the added 12 volt tail lights, brake lights, and turn signals. I might have eventually installed a carrier, but until then I kept the battery in the trunk. I kept t up with a magneto battery charger.

[TXGOAT2]

The red top batteries are compact and lightweight and long lasting. My '26 roadster has a 6 volt red top under the front seat and it works fine and stays clean. It charges off a stock generator and cut out. I don't know how old it is, but I've been using it for 3 years with no problems.

[DHort]

My Optima 6V redtop lasted 11 years. In the winter it just sat in the car.

[TRDxB2]

I have a brass T in the shop that presently has a 12v Group 121R battery rated at 550CCA and a T starter & later hogshead retrofitted. Space under the back seat is very limited so we are looking at a way of minimizing space. This starter is mostly used when emergency starting the engine (-stalled the engine in traffic, or when hand-cranking is inconvenient). Also, the battery will be used to power LED lamps for a short period of time (i.e.: less than 30 minutes from a show or home from dinner). I am looking at Lawn & Garden batteries that are used in 3 cylinder diesel garden tractors that have 350CCA. While I realize that the length/duration of cranking time would not be as long as it would be with a 500CCA battery, or maybe the starter would not spin the engine as fast, ...but for an engine that would normally start easy enough after 2, 3, or maybe 4 pulls with the hand crank, what would we be giving up with using the smaller 350CCA battery in lieu of a 500+CCA battery? Do you think that would work in this application??

TIA

First question is why does it have a 12volt battery? Usually people do this for a weak starter before they damage it.
Next as George asked, no battery bracket? What's the reason for under the seat?
What do you have planned for charging the battery? Are you running on MAG?
So if the power requirements are just emergency starting and led lights....
Two specifications to look at for your battery
For the LED's
Ah - The ampere-hour rating denotes the power and longevity of a battery. How many hours, more or less, a battery would last without a recharge. LEDs take very little amps. So if your total led amps is 4amps & a 40Ah battery should power for about 8 hours not 10 (40/4) as expected.
CCA is specification for cold weather starting and really not the spec for a Model T
CA is the specification for cranking amps, determines how much power you have to start your car in most average climates.
RC or reserve capacity is the number of minutes a battery can provide power before needing a recharge.

Given your expected usage you don't need more than a motorcycle/atv/lawn mower battery - & trickle charger
If you want to go big & under the seat, many go with the 6V Optima Redtop because its sealed and can be put on its side

[BRENT in 10-uh-C]

First question is why does it have a 12volt battery? Usually people do this for a weak starter before they damage it.
Next as George asked, no battery bracket? What's the reason for under the seat?
What do you have planned for charging the battery? Are you running on MAG?
So if the power requirements are just emergency starting and led lights....
Two specifications to look at for your battery
For the LED's
Ah - The ampere-hour rating denotes the power and longevity of a battery. How many hours, more or less, a battery would last without a recharge. LEDs take very little amps. So if your total led amps is 4amps & a 40Ah battery should power for about 8 hours not 10 (40/4) as expected.
CCA is specification for cold weather starting and really not the spec for a Model T
CA is the specification for cranking amps, determines how much power you have to start your car in most average climates.
RC or reserve capacity is the number of minutes a battery can provide power before needing a recharge.

Given your expected usage you don't need more than a motorcycle/atv/lawn mower battery - & trickle charger
If you want to go big & under the seat, many go with the 6V Optima Redtop because its sealed and can be put on its side

Damn Frank, you come across as one of the most condescending individuals by the way you ask questions!!! At least from my view anyway, your answer would likely have been most helpful if you would have just started your paragraph beginning with "Two specifications to look at for...."
and left all the other opinions out.


But with the above said and one that tries to get along, below are my answers to your comment.......

1st, To begin with, -I'm not really sure if "why" it has a 12v battery should be of anyone's business, and I'm not so sure it is actually pertinent to my original question. The answer to the 2nd part of your question is that it uses a 12v battery because it has a 12 volt gear reduction Model-T starter installed. (-It purposely does not have an original 6v starter being powered with 12 volts.)

2nd, Quite honestly, -not everyone wants to drill holes in an early frame just to mount an original style "Battery Bracket" underneath for all the world to see. It does have the 12v battery mounted inside of a battery case that is attached to the floor of the body for safety. Since most people drive -and park their Model-T with the hood closed, most surrounding spectators never realize an electric starter has been retrofitted, -especially when a battery cannot be seen hanging from underneath the vehicle.

3rd, Nothing is changing with how the present battery was/is being charged since it evidently has worked well. The 12v battery is either being charged with a Battery Tender (-while in storage) ...or if the car is being driven, it uses one of John Regan's Magneto powered chargers that mounts directly to the terminals on the back side of the coil box.

4th, Yes, it has a fully functioning Magneto.

5th, From my experience as a former Optima dealer, when Optima moved their manufacturing operations to Mexico about 16 or 17 years ago, their QC went to being trash. I had so many warranty claims from customers that we quit carrying/installing them. Additionally, most Model-T generators or aftermarket T alternators cannot re-charge an AGM battery that is below about 11 volts without damaging the battery and/or the alternator, so they really are not a good match for how most people drive their early Ts. Therefore based on that and multiple 'less than satisfactory' experiences, any Optima in this hobby is not an option for me.



To update everyone on this, we wound-up purchasing a Group 51 series battery (-amongst 4 other batteries) because the Group 51 gave about 180 more CA than the smaller diesel garden tractor battery did. I think this Group 51 battery should fit the 'need' nicely but time will tell I suppose.

FWIW, this Group 51 battery was about ½ the size of a Group 24 battery, ...and you can see its physical size when compared to the Group 1 6v battery next to it.

[DanTreace]

Brent

Thanks for the details on that 'little' 12v battery. That should work fine for the modified 12v T starter.

Here is torque specs on the 12v modified.

A typical well working T starter on 6v will put out good 8-10 ft/lbs of torque, plenty to crank over a cold engine.

And that little battery is good for running board battery boxes used on early cars. Am putting a running board battery box on the '12 project (has a '13 frame, and don't want to drill and use the later Ford chassis holder.)

For my use 6v is ok, stock Ford, so a red top Optima fits into the battery box on the running board, that's what I'll use. My experience with Optima 6v is fine. No issues for me for years, in fact, one dated 2014 is still in the '25 touring and doing great.

[Craig Leach]

Hi Brent,
Glad you found a solution, congrats on a Wasp starter. You are correct about the charging issue with Optima batteries & they require a special
trickle charger to maintain them ( most good quality chargers now have a setting for AGM batteries). It has been my experience that the lawn
& garden mower batteries work fine with a straight 12VDC conversion using a T starter & generator. Starter engagement is softer & they charge
up pretty fast with the generator. IMHO. Now everyone is free to bash 12volt conversions in a model T
Craig.

[TRDxB2]

Damn Frank, you come across as one of the most condescending individuals by the way you ask questions!!! At least from my view anyway, your answer would likely have been most helpful if you would have just started your paragraph beginning with "Two specifications to look at for...."
and left all the other opinions out.

The questions I asked (some the same as others) were just to trying to understand the constraints placed on a battery selection.
Like some others, I don't know anything about the car you have in mid.

Since someone indicated you have a WOSP starter and not a stock Model T starter. So knowing the amperage draw would be helpful. I looked it up and the 12V is rated at 1.4kW (117amps), the same as the 6 volt.

[BRENT in 10-uh-C]

The questions I asked (some the same as others) were just to trying to understand the constraints placed on a battery selection.
Like some others, I don't know anything about the car you have in mid.

Since someone indicated you have a WOSP starter and not a stock Model T starter. So knowing the amperage draw would be helpful. I looked it up and the 12V is rated at 1.4kW (117amps), the same as the 6 volt.
wosp starter.png

Maybe I misunderstood your line of questioning so I will definitely apologize to you but I must confess that I'm still not sure how the 'Why does it have a 12volt battery? Usually people do this for a weak starter before they damage it." "Why no battery bracket?" "What's the reason for under the seat?" "What do you have planned for charging the battery?" "Are you running on MAG?" etc. line of questioning was necessary to answer my question of what are we giving up with a 350CCA battery vs. a 500CCA battery.

[TRDxB2]

The questions I asked (some the same as others) were just to trying to understand the constraints placed on a battery selection.
Like some others, I don't know anything about the car you have in mid.

Since someone indicated you have a WOSP starter and not a stock Model T starter. So knowing the amperage draw would be helpful. I looked it up and the 12V is rated at 1.4kW (117amps), the same as the 6 volt.
wosp starter.png

Maybe I misunderstood your line of questioning so I will definitely apologize to you but I must confess that I'm still not sure how the 'Why does it have a 12volt battery? Usually people do this for a weak starter before they damage it." "Why no battery bracket?" "What's the reason for under the seat?" "What do you have planned for charging the battery?" "Are you running on MAG?" etc. line of questioning was necessary to answer my question of what are we giving up with a 350CCA battery vs. a 500CCA battery.

So you can understand where I & others were coming from to actually point to a battery.
Why the 12v: There have been numerous Forum discussions about some members using a 12volt battery on a 6volt starter
Why under the seat/no battery bracket: Size restrictions (smaller 350CCA battery vs 500+CCA battery) you selected by Group size
Why charging: Ah & RC values - how long between a charge.
Why Magneto: If charging a 12 volt battery via John Regan's Magneto powered charger a different bulb could be used. The one initially specified is for 6volt battery

12v magneto charger.png (32.36 KiB) Viewed 1483 times

https://www.mtfca.com/discus/messages/29/23876.html
By John F. Regan on Sunday, January 21, 2007 - 11:32 am:
You can use the same bulb but you will get less charging using a 12V battery because there is less potential difference between the nominal 28VAC of the magneto and the 12V battery versus 28VAC and a 6V battery. If the battery is used only for hot shot starting and possibly powering a brake light then the bulb we supply in the kit probably will work fine. If you need MORE charge then you can use an 1129 bulb (which is a 6V bulb actually) in the circuit with your 12V battery. You cannot use an 1129 bulb to get more charging with 6V battery since it will burn out rather quickly. The bulb we supply in the kit is an industrial bulb that is about the lowest resistance bulb we could find that was 12V. Everage charge rate will also be reduced if you are running a 3:1 rear end due to lower average RPM of engine.

[BRENT in 10-uh-C]

So you can understand where I & others were coming from to actually point to a battery.
Why the 12v: There have been numerous Forum discussions about some members using a 12volt battery on a 6volt starter
Why under the seat/no battery bracket: Size restrictions (smaller 350CCA battery vs 500+CCA battery) you selected by Group size
Why charging: Ah & RC values - how long between a charge.
Why Magneto: If charging a 12 volt battery via John Regan's Magneto powered charger a different bulb could be used. The one initially specified is for 6volt battery
12v magneto charger.png

https://www.mtfca.com/discus/messages/29/23876.html
By John F. Regan on Sunday, January 21, 2007 - 11:32 am:
You can use the same bulb but you will get less charging using a 12V battery because there is less potential difference between the nominal 28VAC of the magneto and the 12V battery versus 28VAC and a 6V battery. If the battery is used only for hot shot starting and possibly powering a brake light then the bulb we supply in the kit probably will work fine. If you need MORE charge then you can use an 1129 bulb (which is a 6V bulb actually) in the circuit with your 12V battery. You cannot use an 1129 bulb to get more charging with 6V battery since it will burn out rather quickly. The bulb we supply in the kit is an industrial bulb that is about the lowest resistance bulb we could find that was 12V. Everage charge rate will also be reduced if you are running a 3:1 rear end due to lower average RPM of engine.

But Frank, I did not ask for any of that!! My question was simply "what do I give up using a 350CCA battery vs. a 500CCA battery?". Your answer was much akin to someone coming on the forum asking about a Runabout seat question and your answer to them was 'Why would you want a Runabout when you should own a Touring car because they are more practical and have an additional seat'. For the record, I never asked for opinions on charging the battery, nor did I inquire about what type of battery carrier I would need. The present charging method (-one of John's magneto chargers and a battery tender) still works and would not be affected differently with the 350CCA vs. the 500CCA battery. Admit it, you did treat me not as a professional restorer that has been a member here for a long time, -but more as newbie.

[TRDxB2]

All I can say is that not every member knows every other member (what they know, what cars they have or are what they are working on at any given time). Now I know someone else.
A simple derogatory answer to your question "what do I give up using a 350CCA battery vs. a 500CCA battery?" would have been 150CCA.

[TXGOAT2]

-150 CCA 0987654321

In my experience, full size batteries outlast the smaller ones almost without exception. Applying a heavy draw, such as a T starter, to a small battery will probably shorten its life, and they seem to come with a short life built in. For non-starter use, a smaller battery ought to do fine, other than its lower storage capability.

Quality of the battery seems to make a lot of difference in how much service it will provide. For instance, I just replaced an 8 year old Yuasa motorcycle battery. The Yuasa batteries are expensive, but every one of them I have ever owned has given excellent service over a very long time, and none of them have ever leaked any acid. I ran the original Yuasa battery in a 2005 Toyota pickup for 11 years. Wal Mart offers a "will fit" battery for about 35.00 that fits the 160.00 Yuasa motorcycle application, but buyers report very short life for the low price battery and its cca rating is substantially lower than the Yuasa. I reckon it's no bargain if you mean to keep whatever it's installed in. (Especially if it leaks acid all over your bike, or whatever!)