Battery Question

[armylifer]

I am hoping that someone can answer a question I have about automobile batteries. I own a 1922 Model T that has a 6 volt generator for charging the 6 volt car battery. The generator output is roughly 75 watts at about 7.5 volts, depending on engine RPM. The generator is the type that has a 3rd brush, which is used to adjust the generator output. I could adjust it to put out 8.1 volts (I tested this) but the generator starts getting hotter than I feel comfortable with, at that output. The generator also has a cutout that stops charging (actually cuts the battery out of the circuit) if the battery voltage is higher than the generator output, such as when the engine is idling.

The question that I have is this; what would the effect be if I were to put an 8 volt battery in place of the 6 volt battery. Would there be a detrimental effect to the 8 volt battery if the generator is only charging the battery when the battery voltage drops to ~7.5 volts? Would an 8 volt battery be harmed if it is kept in a constant state of charge that is less than the full rated voltage?

BTW, the electrical system in the car will handle the additional voltage. There is no issue with the wiring because it is designed to handle the ~30 volts from the magneto when running off the magneto.

 

[ccoon520]

It probably wouldn't hurt the battery (assuming Lead Acid) but the car is designed around a 6 volt system so sending more voltage will probably not be good for electrical components in the car for the long run. Is it just a cost/availability thing or is there something that the 6v battery isn't keeping up with?

 

[mcmxi]

The question that I have is this; what would the effect be if I were to put an 8 volt battery in place of the 6 volt battery. Would there be a detrimental effect to the 8 volt battery if the generator is only charging the battery when the battery voltage drops to ~7.5 volts? Would an 8 volt battery be harmed if it is kept in a constant state of charge that is less than the full rated voltage?

You would most certainly shorten the life of the 8V battery in this application due to sulfation i.e. a build up of lead sulfate crystals on the surfaces of the internal plates.

A 12V car battery needs to be maintained at a voltage of 12.4V or higher to prevent sulfation. A fully charged 12V battery will show 12.8V to 13.2V. I would expect a fully charged 8V battery to be up around 9V.

 

[armylifer]

It probably wouldn't hurt the battery (assuming Lead Acid) but the car is designed around a 6 volt system so sending more voltage will probably not be good for electrical components in the car for the long run. Is it just a cost/availability thing or is there something that the 6v battery isn't keeping up with?

As I said in my post, the electrical system is designed to handle more than 30 volts because that is what the magneto is putting out in normal operation.

The reason I want to go to a higher voltage battery is because I like to drive with the lights on even during daylight hours. The stock charging system does not charge the battery with the lights on unless I am going faster than 35 mph. I normally drive at about 30 to 33 MPH. The car can sustain the faster speeds but then you put excessive wear on 100 year old parts so slower speeds are the norm when driving an all original car this old.

Many people upgrade their charging systems to 12 volt but I do not want to go that route. It is expensive to do and it actually devalues the car with certain segments of the collector world. This car is all original and I want to keep it that way as much as possible.

EDIT: Just in case you did not know, the lights run off the battery and the engine runs off the magneto.

 

[armylifer]

You would most certainly shorten the life of the 8V battery in this application due to sulfation i.e. a build up of lead sulfate crystals on the surfaces of the internal plates.

A 12V car battery needs to be maintained at a voltage of 12.4V or higher to prevent sulfation. A fully charged 12V battery will show 12.8V to 13.2V. I would expect a fully charged 8V battery to be up around 9V.

That is the kind of information I am looking for. Thank you!

 

[GreensvilleJay]

Using an 8 volt battery is a 'cheat' and will burn out your 6 volt lightbulbs in short order.

Simple solution, keep the 6 volt system and replace the lights with LEDs. A 'lamp' consisting of two White LEDS in series will run off a '6 volt system'. Someone probably makes them for 'old cars'.
I went another route, used a voltage upverter to change 6 VDC into 12VDC to run 'off the shelf' LEDS designed for cars. Cost was about $10 per headlight.
The genny sounds like it'll only output 10 amps, so you need to start there, look at the AMPS the lights use.
A 30 watt lamp will draw about 5 amps ( 30 A / 6V = 5 amps).

You can probably get higher powered generators, 'retro' alternators, and a few other options. Much depends on if you want the 'stock' look of your ride,size of wallet and how handy you are.

 

[armylifer]

Using an 8 volt battery is a 'cheat' and will burn out your 6 volt lightbulbs in short order.

Simple solution, keep the 6 volt system and replace the lights with LEDs. A 'lamp' consisting of two White LEDS in series will run off a '6 volt system'. Someone probably makes them for 'old cars'.
I went another route, used a voltage upverter to change 6 VDC into 12VDC to run 'off the shelf' LEDS designed for cars. Cost was about $10 per headlight.
The genny sounds like it'll only output 10 amps, so you need to start there, look at the AMPS the lights use.
A 30 watt lamp will draw about 5 amps ( 30 A / 6V = 5 amps).

You can probably get higher powered generators, 'retro' alternators, and a few other options. Much depends on if you want the 'stock' look of your ride,size of wallet and how handy you are.

The generator will put out more than 10 amps if I adjust the 3rd brush but I don't want to adjust it higher than the 10 amps it is putting out right now. One reason is because I don't want to overcharge the battery. The other reason is because the generator gets hotter than I like when I adjust the output higher than it is right now.

I actually found some 6 volt LED light bulbs on Amazon but they will not be here until around May 5th. I think that those light bulbs will solve the issue but I asked as a general question anyway because it was a thought I was tossing around for some time.

 

[GreensvilleJay]

Battery won't be overcharged if the cutout relay is working properly

 

[armylifer]

Battery won't be overcharged if the cutout relay is working properly

The cutout on a Model T is designed differently than that. It is designed to allow reverse current flow if the battery voltage is higher than the generator output. Since the generator output at operating speeds is always greater than the battery resting voltage, the battery is always charging when at driving speeds. You can see the cutout working when at or near idle engine speed because the ammeter will show a discharge until either the battery reaches a voltage less than the generator is putting out or you raise the engine speed to a point where the generator is putting out higher voltage than the battery has.

 

[BruceP]

QUESTION: Is there a 'problem' you are trying to resolve by using 8v battery?

 

[armylifer]

QUESTION: Is there a 'problem' you are trying to resolve by using 8v battery?

Not a problem per-se'. I want to be able to run with the headlights on always. Normally I would be able to do that if it had the stock headlight bulbs that were used back in the day. The trouble is the newer bulbs available now take higher amperage than back in the day. When I am driving at 30 MPH the generator is charging at 10 amps without the headlights on. However, driving at that same 30 MPH with the headlights on is using 12 amps, thereby discharging 2 amps all the while I am driving. This is not really a problem because the battery has enough reserve capacity to last all day long without overly discharging the battery enough to harm it. The problem I am trying to address is concerning an upcoming 3 day tour that I am participating in. I am concerned that if I drive that whole time with the lights on that I may harm the 6 volt battery with a constant 2 or more amp discharge for the whole 3 day tour.

Of course I could solve that by not running with the lights on full time, as the car was originally designed to do. But I have learned that people tend to misjudge the distance and speed that I am driving so I add a level of safety by running with my lights on full time. I was hoping that if I put a higher voltage battery in it that I might get a little more reserve time out of it. I already have the highest capacity 6 volt battery available. I was just soliciting the OTT knowledge base to see if there would be an advantage to be gained if I went with an 8 volt battery versus the 6 volt one.

 

[torch]

If you are just after increased visibility for this one journey, what about something like this:

https://www.amazon.ca/Roadside-Flashing-Warning-Emergency-Magnetic/dp/B0796RHMQR/ref=sr_1_38?crid=VNF73X2YHQRQ&keywords=battery%2Bflashing%2BLED%2Bwarning%2Blight&qid=1649727083&sprefix=battery%2Bflashing%2Bled%2Bwarning%2Blight%2Caps%2C85&sr=8-38&th=1

 

[armylifer]

If you are just after increased visibility for this one journey, what about something like this:

https://www.amazon.ca/Roadside-Flashing-Warning-Emergency-Magnetic/dp/B0796RHMQR/ref=sr_1_38?crid=VNF73X2YHQRQ&keywords=battery%2Bflashing%2BLED%2Bwarning%2Blight&qid=1649727083&sprefix=battery%2Bflashing%2Bled%2Bwarning%2Blight%2Caps%2C85&sr=8-38&th=1

I think that light would be illegal for use on a privately owned vehicle, at least in WA State.

 

[torch]

Oh, well, don't do that then. No issues using an amber flashing light in Ontario, but different jurisdictions may have different laws for sure.

 

[D2Cat]

I think that light would be illegal for use on a privately owned vehicle, at least in WA State.

You folks can't use amber flashing lights on private snow plow truck either?

 

[Lil Foot]

In AZ & the peoples republic of CA, you cannot use red or blue beacons, but other colors are OK.
I have a yellow one & a green one that I use in the dunes or when decorating vehicles for Christmas & such.
YMMV.

 

[torch]

In AZ & the peoples republic of CA, you cannot use red or blue beacons, but other colors are OK.

I double checked the Ontario HTA. Red and blue are reserved for emergency vehicles as are flashing headlights, and green for volunteer firefighters' private vehicles while responding to an emergency.

Tow trucks must display a flashing amber while towing a vehicle, and I think escort vehicles for oversize loads, but there's no restrictions on other vehicles using them too.

 

[GreensvilleJay]

yup ,escorts need the flasher ambers on..
even when they're 100s of meters away from their super oversized load that's doing 122KpH ( 70 MILES PER HOUR )

 

[armylifer]

The lights themselves are not illegal. How they are used is what the restriction is. In this case, they could only be used when my car is not in motion. Here is a link to the applicable section in WA state law. There are other sections that apply to auxiliary lighting but they do not apply to my vehicle in this case

RCW 46.37.210: Additional lighting equipment.

app.leg.wa.gov

 

[BruceP]

You folks can't use amber flashing lights on private snow plow truck either?

In Vermont, one needs a PERMIT to even have such a light on a private vehicle. If your wife (without permit) wants to use that vehicle, the light must be covered. (usually a winter tuque is used.)