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Old 05-29-2019, 11:05 PM   #1
29delivery
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Default 8 volt question

Hi everyone,would running a 8 volt battery in my 36 ford have a effect on the accuracy of the gas gauge and oil pressure gauge. Thanks Ken
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Old 05-29-2019, 11:16 PM   #2
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Default Re: 8 volt question

My guess would be yes, but I've never needed to do so. But interested in the better educated opinions here. Believe volts are less a factor then the ohms resistance. whether the voltage to the sender is effected.




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Old 05-29-2019, 11:22 PM   #3
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Default Re: 8 volt question

The short answer is yes, the electrical gauges are designed to operate on 6 volts not 8. Why are you considering an 8 volt battery? There is really no need to use an 8 volt battery. It will cause premature failure of the 6 volt lamps and other problems. If you are trying to solve slow cranking then an 8 volt battery is only masking an existing fault in the system. IMHO a well maintained 6 volt system with the correct battery cable gauge and a good battery is a far better option. If you must increase the voltage then go the full 12 volt option. At least you can get 12 volt bulbs or LED bulbs and also put a proper reducer in series with your gauges to give more accurate readings. Hope this helps?
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Old 05-30-2019, 12:30 AM   #4
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Default Re: 8 volt question

I ran 8 volts in my 50 Mercury for a couple of years and I noticed no difference in gauge operation at all. My only dislike other than 6 volt battery chargers not working the best was having to adjust the voltage regulator up to 9.4 volts and I felt it was pushing the radio and headlights a bit hard. The battery sat dead for a while due to not having a battery tender and got ruined so I threw it out and purchased a new proper 6 volt battery !
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Old 05-30-2019, 01:22 AM   #5
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Default Re: 8 volt question

Certainly more volts is bad if you don't reduce. Lights only draw so many amps. But instant availability will do harm.


Think of it this way. or a water hose restricted. Volts being pressure.
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Old 05-30-2019, 05:47 AM   #6
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Default Re: 8 volt question

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If your having starting or dim lights issues, clean and add additional ground wires. My 78 yo car runs fine on 6 volts. Keep all your connections tight and bright.
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Old 05-30-2019, 07:13 AM   #7
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Default Re: 8 volt question

The 8 volt battery in my opinion is not a very good idea. As mentioned, if you have everything fixed 6 volts will do everything you need. It is hard enough to find 6 volt battery chargers and I've never seen an 8 volt one. I can understand going to 12 to add modern electronics but my GPS runs fine on 6 volts. I once left my headlights on for close to an hour and the car fired right up on the optima. It took a good 50 miles before the voltage came up enough for the charging system to come down from full charge but 2 years after that incident the battery works fine.
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Old 05-30-2019, 07:34 AM   #8
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Default Re: 8 volt question

Ken, I seem to remember a number of discussions on this 8 volt battery issue not that long ago here on the Barn. "Searching" for it, however, sometimes is a challenge for me!! The thing that motivated me to get rid of the 8 volt that was in my '47 when I bought it was that it was a "killer" for my Ford Philco radio....also dead on arrival!


As Frank did above, I cleaned up the grounds and went with an Optima. Also got the radio rebuilt and no more electrical issues. As you've probably noted from your time as a member here, there are those of us who are 6 volt fans and those of us who are 12 volt conversion fans. 8 volt fans seem to really be in the minority, but to each, his own!!
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Old 05-30-2019, 09:13 AM   #9
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Default Re: 8 volt question

Hi,thanks for the input,I was not having any hard starting problems or any of the other symptoms mentioned,The 8 volt battery was in the car when I bought it and I'm in the process of rewiring the car with the correct harness,battery cables ect and I have also checked all the gauges and replaced the fuel sender float since it sank and was not working.I was wondering about the 8 volts because of the King Seely sender and the bi metal make up of the gauge/sender design .I'll get a 6 volt battery before I start the car. Thanks for the replys. Ken
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Old 05-30-2019, 09:27 AM   #10
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Default Re: 8 volt question

On your rewire, some important considerations are:
1. Grounds, good clean grounds with grease on the bare metal surfaces and the connections. Additional grounds are always helpful.
2. Wire size, especially the starter cable and battery cables need to be the proper gage for a 6v system (heavier gauge than 12v).
3. A little grease on all the connections helps.
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Old 05-30-2019, 09:28 AM   #11
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Default Re: 8 volt question

Since your rewiring the car change it back to 6V with nice clean grounds and you should be good to go. 8V is a waste of money,time and effort.
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Old 05-30-2019, 10:11 AM   #12
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Default Re: 8 volt question

I have been having problems with the gauges on my '41 reading too high, like a quarter tank indication when I ran out of gas. The car is converted to 12 volts so I used the Runtz voltage reducers at the gauges. I checked the voltage at the gauges and the Runtz were all putting out 8 volts. I replaced them with a voltage reducer that puts out 6.2 volts, and was disappointed to discover that it made no difference in the indication on any of the gauges.

I figured out that is because the design of the gauges is such that they respond only to how much average current the sensor draws over time, as the bi-metal strip opens and closes the points inside the sensor.

Bottom line, OEM sensors for oil pressure, engine temperature and gas tank are not very sensitive to voltage. That said, you do not want to run them on 12 volts, because it might burn out the little heaters.
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Old 05-30-2019, 10:36 AM   #13
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Default Re: 8 volt question

Quote:
Originally Posted by Tinker View Post
My guess would be yes, but I've never needed to do so. But interested in the better educated opinions here. Believe volts are less a factor then the ohms resistance. whether the voltage to the sender is effected.




.

Don't knock it until you actually try it! Theory is one thing, actual experience is a whole different matter.

I lived in Eastern Idaho when I was a kid, through my teens. I bought my '36 Ford coupe in 1952 in Idaho Falls. The winters in Eastern Idaho can be brutal, -30 is quite common, it was very common to remove the battery from a vehicle and take it into the house to keep it from freezing.
I ran a 8v battery in my '36 for many years in Idaho, we adjusted the regular up to 8+ volts. I had changed my generator to a '39 two brush and a regular in lieu of the original.
My car has an original 9 tube Philco/Ford radio and a '39 heater.. The 8v battery had no adverse effects on any of the accessories, instruments and/or lights. Headlights were converted to sealed beams in '52.
I continued to use a 8v battery in my '36, through 1963, after I moved to So Cal in '56.
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Old 05-30-2019, 10:50 AM   #14
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Default Re: 8 volt question

Thanks to another Fordbarner, I found it's best to use a Constant Voltage Reducer on the FUEL, OIL PRESSURE and TEMP gauges when converting to 12V. That way those three gauges will still give very accurate 6V readings as the CVR reduces the incoming voltage to an accurate 6V.

To get accurate readings of the stock VOLT or BATT gauge it's best to isolate that gauge and install a 60 OHM resistor to reduce the incoming 12V to 6V.

Also, to get accurate FUEL gauge reading you can take the sending unit apart and adjust the star wheel under the cover. Turning it CW moves the need closer to Full. Turning it CCW moves it closer to E. This takes a lot of time and patience to get it right.
Also, CAREFULLY clean the points with 600 emory paper.

Of course, bending the float arm of the sending unit also effects gauge readings. A hairline crack in the float will also give false readings.

How to do all this has been shown on the Fordbarn SEARCH option. Here's a starting point.
https://www.fordbarn.com/forum/showt...k+sending+unit
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Old 06-02-2019, 10:50 PM   #15
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Default Re: 8 volt question

interesting info Fordy, makes sense.
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Old 06-02-2019, 11:15 PM   #16
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Default Re: 8 volt question

Quote:
Originally Posted by drolston View Post
I have been having problems with the gauges on my '41 reading too high, like a quarter tank indication when I ran out of gas. The car is converted to 12 volts so I used the Runtz voltage reducers at the gauges. I checked the voltage at the gauges and the Runtz were all putting out 8 volts. I replaced them with a voltage reducer that puts out 6.2 volts, and was disappointed to discover that it made no difference in the indication on any of the gauges.

I figured out that is because the design of the gauges is such that they respond only to how much average current the sensor draws over time, as the bi-metal strip opens and closes the points inside the sensor.

Bottom line, OEM sensors for oil pressure, engine temperature and gas tank are not very sensitive to voltage. That said, you do not want to run them on 12 volts, because it might burn out the little heaters.

57 fords use a ceramic 12v to 6v ignition reducer, its a stock component. Bulky but could be used for all gauges that is required. In theory.... Not sure of it's amp capacity as it's only to reduce the coil down to 6v. But it's a high demand/usage voltage reducer as the coil requires constant voltage and amps. So it might hold up... Maybe... or not....


A light on 12v with 6v bulbs are fine till you turn them on and draw amps, then they blow out. Gauges are amp activate always when running. Voltage is always active when on but is harmless less a -/+ is made/connected. In layman terms. Gauges rely on current sent from the senders that use ohms (reduce or increase voltage for signal). Voltage sensitive.

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