6/12v series parallel circuit

[tkeithlu]

The tech "Steve" at Texas Industrial Electrics has come up with a less expensve and rather ingenious circuit for starting with 12v while running on 6.

Yeah, in a perfect world I would keep my 1924 T on six volts. Difficulty keeping all the contacts beautiful in a Florida salt spray environment led me to wanting to add a second battery and send 12v to the starter while not changing over to a 12v system. I tried a 12/24 series/parallel relay that was lying around after adding a battery under the rear deck just in front of the rear axle. It worked at 6.3v, but at 6.1v the coil couldn't keep the contacts in place against the return spring. It went clunk but nothing came out the series end. A 6/12 series/parallel switch is $550+, too much on our "It's a toy" model T budget. Steve came up with this circuit, which uses two $90 six volt relays. The ingenoius part is that he figured out how to wire them so that the generator still charges both batteries when they are in parallel, but there is not a feedback route while the starter is fired up. [image]

[/image]

[Scott_Conger]

Welcome to the Forum

As a 59 year resident of Florida until 6 years ago, being involved with "T"s since 1974 and living 2 blocks from the water, I never had a problem with any of my "T"s electrical system, or have them fail to start due to electrical issues. I have no idea how beautiful the contacts were (then or now), but they always worked and with correct stock wiring.

It's your car, and if it makes you happy, then go for it. But to me, it is a solution looking for a problem...and it will eventually will become it's own problem, for certain,

If you are having problems with any contacts, I will bet dollars to donuts that you have too light of a gauge of battery cable. I cannot count the times I've suggested this to guys as a potential problem and have them tell me "they're just fine...in fact, they're brand new" and then come to find out (when you actually LOOK at them) they were 12V cables that the NAPA guy said would work.

Best of luck

[TXGOAT2]

Ignition grease and quality wiring will prevent most electrical issues in simple circuits around marine environments. It looks like a good solution for someone wanting to use high draw 12 volt devices. Of course, for something like camping, you'd need a rather large auxilliary battery to supply much power for very long without running the engine, and you'd still have a very low output primary power source in the T generator. If I wanted a 12 volt system, I'd look into mounting an internal regulated 50 amp alternator with modern flat belt drive, 12 volt starter, and 12 volt battery, lights, etc. I believe that would be satisfactory for a stock ignition system with a functioning magneto or any type of modern distributor conversion. A 12 volt DC system not designed for marine service will deteriorate about the same way a 6 volt system will. A 50 amp alternator would add significant parasitic load to a T engine if operating at full capacity, but it would rarely, if ever, be in full output mode.

[mtntee20]

Hi Tim,

Being familiar with series/parallel starting systems and with basic wiring schematic practices, I believe there is a small mistake in the wiring diagram. I suggest you confer with your tech. Steve to ensure his specifications are correct.

When drawing a schematic with different width lines, representing different wire gauges, the same width is used for the same gauge. Thus the thick red wires and thick black wires should be the same gauge wherever they are the same width on the schematic.

Steve has BOTH the red and black wires labeled 1/0 or 2/0 in places AND 10 gauge in other places. I believe they should be 1/0 or 2/0 in ALL PLACES where they are depicted as the same width.

Another small problem is there is NO gauge designation for the Main 6 volt battery ground wire. This should be labeled as 1/0 or 2/0 as it will be carrying high amperage as does the #2 6 volt battery POSITIVE output that is labeled as such.

Maybe this is all spot on but a 50-100 amp circuit breaker in a 10 gauge wire appears to be incorrect when the current rating for 10 gauge wire is 15 amps maximum continuous.

It's been a long time since I was working electricity/electronics. Things, assuredly, have changed over the years. Thus, I may be full of crap. BUT, it would be smart to ensure all is correct before installing and finding out otherwise. There are members on this forum who have had electrical fires in their Ts.

Good Luck,

[TXGOAT2]

A 12 volt starter offers little or no advantage over a properly operating 6 volt starter. The most reliable starting systems I've ever owned have been 6 volt systems. A full 12 volt system has many advantages for someone who wants to use various modern devices in an old car, and not a few disadvantages. For LED lights, a 6 to 12 volt converter is probably a good option, perhaps with a small 12 volt battery for a stabilizer and a source for charging phones, etc.

[tkeithlu]

I forgot to mention that in order to prevent feeding 6 volts continuously to the starter, the 12v needs to be run back through the unused NO relay contacts. In my arrangement, all the current carrying wire is 2 gauge fine standed and the control wire 10 gauge. I'm using a six volt starter, but feeding it 12 volts.

The points on 12v/6v are well taken, and I wish I had one of you here to advise me. I can barely get a newly rebuilt 6v starter to turn with a new 6v battery. I've wondered whether I've got extra friction in the transmission bands, but loosening them does seem to help. Any thoughts?

[Scott_Conger]

If your rebuilt starter is off of eBay, good luck. If it is from a reputable supplier and will barely turn the engine over, then I would be even more inclined to believe that your starter cables are too lightweight and could even perhaps use a good ground strap at the engine. Some folks swear by the extra ground strap...I've never needed one.

A new 6V battery and new starter should turn the car over pretty briskly. Going to 12V without knowing what is going on is solving a symptom and not the illness. Along the way, like most people who do this, you will be breaking bendix's and bending bendix springs. Some folks swear it's a wonderful thing and (claim to) suffer no ill consequences, but the vast majority end up fixing things periodically after they break.

I believe there are more hobbyists around you than you realize. Contact the Suncoast T Club or contact MTFCA and ask for a membership list for FL

You do have help out there!

[TRDxB2]

A 12 volt starter offers little or no advantage over a properly operating 6 volt starter. The most reliable starting systems I've ever owned have been 6 volt systems. A full 12 volt system has many advantages for someone who wants to use various modern devices in an old car, and not a few disadvantages. For LED lights, a 6 to 12 volt converter is probably a good option, perhaps with a small 12 volt battery for a stabilizer and a source for charging phones, etc.

You are so right! Much of the 6v vs 12v thinking is based on post 1930 cars (batteries and charging system) and in understanding battery specifications and when a battery needs to be charged. And as Scott mentioned the correct size battery to starter cable.
A stock starter Model T needs a battery for the starter, 3 light bulbs and possible the 4 buzz coils if not run on MAG. ModifiedT's use more light bulbs.
GPS and phone chargers next to nothing.
--
The battery specification for a starter is CCA
Cold Cranking Amps (CCA) : CCA is a rating used in the battery industry to define a battery's ability to start an engine in cold temperatures. The rating refers to the number of amps a battery can deliver at 0°F for 30 seconds while maintaining a voltage of at least (7.2 volts for a 12-volt battery) (3.6volts for a 6-volt battery). The higher the CCA rating, the greater the starting power of the battery.
--
The battery specification to power lighting & ignition systems is Ah
Ah, ampere hours, is simply the unit of measure for a battery's storage capacity. That is the number of amperes that it can provide for a given length of time in hours. For example: a 200 Ah battery can roughly output 10 amperes for 20 hours
--
Reserve Capacity is the amount of time in minutes a battery can deliver, at 25 degrees Celsius, 25 amps before a voltage drops to (10.5 V for a 12 volt) and (5.25 for a 6 volt). So this can give you an idea on how long a vehicle can be driven under a normal electrical load. This is important for modern cars with a high electrical load, nonexistent in a Model T.
--
Understanding battery charging
Volts, not amps, are what a battery needs to be charged. The amperage values determines the length of time to fully charge a battery.
So what does an Amp Gauge indicate? The amount & direction of current flow, amperage not volts. As far as a battery goes its only an indication of it being charged or used and not if its under or over charged. The Model T generator's 3rd brush is used to regulated the amount of amperage produced.
The Fun Projects Voltage Regulator only limited the amount of voltage output. A cut-out acts as a switch to connect/disconnect the circuit between the generator & battery. You can regulate charging your battery while driving and preventing over charging by just turning the lights on & off
--
So which battery
No - not talking about lead acid or AGM but Starter vs Deep Cycle
A starter battery, also known as Starting, Lighting and Ignition (SLI) battery is designed to provide maximum power for a short duration - about 1-3 seconds. Despite its ability to generate high current, it cannot handle deep discharges without permanent long-term effects. Conversely, a deep cycle battery provides continuous power instead of short surges of power. It’s designed to handle the cyclic demands of deep discharge.
-Optima AGM Red Top: 6-Volt, 800 CCA.; 50Ah; Reserve capacity of 100 minutes; $240
-Traveller(Die Hard), 875A Heavy-Duty Battery 6volt Group 1 flooded battery: 700 CCA; 63Ah;Reserve Capacity: 150 min; $120

[Steve Jelf]

I bet if you try 1/0 battery cable with all connections clean and tight, that rebuilt starter will work just fine with a single 6 volt battery. The usual aim of a 12 volt conversion is to make the engine "spin fast enough to start". Starting on battery, a Model T doesn't need to spin fast.

https://www.youtube.com/watch?v=3pv6HWWOGYA

[Tim Rogers]

Plenty of facts and great info on this thread, but I'm convinced that 12 volt superiority myth will never die...

[Art M]

Frank. Thanks for yhe battery rating information

Steve, I agree that contacts etc are often overlooked


Art Mirtes

[TXGOAT2]

To OP:
Don't overlook the possibility that your clutch is dragging. Some clutch drag is normal, and it will act against the starter, be it human or electrical. Thick oil or adjustment problems can make clutch drag severe enough to overload the starter and can make crank-starting almost impossible, especially at lower temperatures. 6 volt systems require the proper, heavy gauge, high quality starter and ground cables and good clean connections and a good starter switch. It's been my experience that 12 volts systems have the same requirements. In both 6 and twelve volt systems, the starter is a low voltage, high current device, and it cannot perform well if full rated current is not available to it.

[speedytinc]

You putting 12V to a 6V starter is a bad idea thats been done & is ignorantly still done. With good connections, a good starter & proper cables, its not necessary & is detrimental to the bendix & ring gear. I'm sure you've heard this.

Possibly your idea of this 6/12v relay unit could have benefit & less a damaging effect if the starter saw 6V to engage the drive, then 12V kicks in to turn the motor over. Still all unnecessary. This is a band-aid to mask the real problems.

Another, less harmful band-aid would be to install an 8V battery. A bit more expensive than a 6V battery, but compatible with all the 6V system.
(lights , dizzy coils, etc. are rated 6-8 volts.) Benefit brighter lights.

[Kerry]

All sounds like a lot of work and expense, just drop in an 8v battery, change nothing and drive for ever.

[Luke]

Timothy,

I agree with many of the other posts here; if you're doing this because the starter motor turns over too slowly then you should probably sort that out first.

However I want to comment on your original post; I would not add such complexity to the Model T, it's simply not called for. A good T will start and run fine on 6V, it will start ok and probably run even better on 12V, and the generator will charge 12V without issue, there's simply no need to switch between the two voltages as per your circuit should you decide to put a 12V battery in place.

The money you'd save on the switching relays etc would be better employed in purchasing some LED bulbs, and altering the starter motor to better operate on 12V.

In terms of fault-finding with your present issue; firstly, can you reasonably easily turn over the vehicle with the crank? If not then take note of some of the suggestions above about what might be causing drag etc.

If however it turns over ok you'll need to use a voltmeter and start at the battery then work your way forward looking for any significant voltage drops when the starter motor is employed. If you have one an IR camera is a very useful tool and will quickly identify poor connections and/or cables. Checking the battery will tell you if it's dropping too low at start (thus suggesting has too high an internal resistance and may require replacement), looking for voltage drops across cables and/or connections will determine if that cable or connection has too high a resistance. If so clean or replace the connection, or replace the cable (or crimp lug if that's where the issue lays).

Luke.

[speedytinc]

Timothy,

I agree with many of the other posts here; if you're doing this because the starter motor turns over too slowly then you should probably sort that out first.

However I want to comment on your original post; I would not add such complexity to the Model T, it's simply not called for. A good T will start and run fine on 6V, it will start ok and probably run even better on 12V, and the generator will charge 12V without issue, there's simply no need to switch between the two voltages as per your circuit should you decide to put a 12V battery in place.

The money you'd save on the switching relays etc would be better employed in purchasing some LED bulbs, and altering the starter motor to better operate on 12V.

In terms of fault-finding with your present issue; firstly, can you reasonably easily turn over the vehicle with the crank? If not then take note of some of the suggestions above about what might be causing drag etc.

If however it turns over ok you'll need to use a voltmeter and start at the battery then work your way forward looking for any significant voltage drops when the starter motor is employed. If you have one an IR camera is a very useful tool and will quickly identify poor connections and/or cables. Checking the battery will tell you if it's dropping too low at start (thus suggesting has too high an internal resistance and may require replacement), looking for voltage drops across cables and/or connections will determine if that cable or connection has too high a resistance. If so clean or replace the connection, or replace the cable (or crimp lug if that's where the issue lays).

Luke.

Well said, Luke.
I forgot to mention checking for voltage loss @ all the connections.

[Craig Leach]

Hi Tim,
Putting the 6 vs 12 volt argument aside. I have seen this on a car years ago but did not figure out how it was done. With that aside in
your schematic, yes the 10Gauge wire is incorrect it should be a 00 /000 wire on the cranking circuit. A 10 gauge wire will most likely
be a smoke indicating slow blow fuse. the other issue I seen is the batteries are in parallel not series so that would still be 6 volts.
One issue that will occur using 6 & 12volts is while cranking anything in the 6 volt circuit that is on will be damaged i.e. brake light
bulb if you have your foot on the brake & head lights if left on. and still only one battery is in the charging circuit. To charge both
batteries you need a battery isolator switch and they are hard to find in 6 volts. Tim I have some unorthodox ideas on this that are not
conducive to the forum conversation, give me a email and we'll bang some ideas around OK.
Craig.

[Allan]

Scott had the right idea. He moved out of Florida!

Alan from down under.

[Scott_Conger]

Alan, you are so right!

[Novice]

My advice. Clean up the contacts front to back. use 000 cable from battery to foot switch and starter. Put Vaseline or red battery terminal spray on battery. starter switch and starter lugs / connections. On My T I found someone had replaced a cable going from the battery to starter switch with a long light gauge 12 volt cable. Made a cut to length custom cable out of 3/8 " 000 ? stranded cable and now it cranks over just fine. No it wont spin like a jet turbine. But for a engine designed in the early 1900s to be hand cranked it turns plenty fast and you don't haft to worry about the 12 volts messing up the six volt starter and Bendix. Ford made a dual voltage electrical system in the mid fifties. used two batteries and was a engineering night mare. Built for cold weather starting. didn't last but a year or two ? used on fire trucks and commercial vehicles. Good Luck

"My 2 cents worth maybe less"

[TRDxB2]

I think the impression that a 12 volt battery is a better starting battery than a 6 volt is because the proper battery specification is not being compared. A starters power, torque, is driven by amperage not volts. If you go buy a drill you'd likely pick the one with the highest torque specification which is in amps (some now use UWO, Unit Watts Out. basically the same, higher the value the more torque). Torque is needed to rotate a stiff engine. Jump starting an engine doesn't take much vehicle speed to cause suffient engine RPM's to get a car started

[Luke]

Frank,

Just to clarify, power is a function of both voltage and current (W=E*I). Torque, typically measured in ft/lbs or Nm, is a function of power and angular velocity, thus torque is affected by voltage as well as current.

You are right that the battery (the supply of energy from which power is derived) matters, and that to some extent this is independent of the system voltage. However the starting system, which comprises a number of components (including the wiring), may work appreciably better if the power|torque is derived from a higher voltage and lower current since for a given size of cable you will only be able to pass a certain amount of current.

Luke.

[TXGOAT2]

As I understand it, higher voltage will push more current (amperage) through a given circuit. A 6 volt system in good condition, including the battery, is fully capable of moving more than enough current to operate the starter to near its design limit. Raising the supply voltage significantly above what a system or component is designed for, that is in good condition, will lead to trouble sooner or later. Probably sooner. Slamming a 6 volt starter with 10 volts or more can be expected to damage it, and likley damage the flywheel ring gear and other mechanical parts as well. If all connections are good, applying 12 volts from a healthy 12 volt battery to a 6 volt starter will overload the battery and the starter and could be expected to shorten the life of both of them, and the starter switch as well.

[Luke]

Pat,

Voltage and current are two separate things, thus a higher voltage will not 'push more current'.

However a higher voltage at the same current will ultimately deliver more power, or conversely a higher voltage will deliver the same power at a lower current. This is why a higher voltage is preferable for systems that have components only just able to carry a given current at a lower voltage, or wiring that is of a size/length/resistance such that voltage drop is significant enough to affect the desired outcome...

You are right with regard to applying 12V to the T starter. There have been several ways espoused as to how to deal with this, I favour simply connecting all the field coils in series (as opposed to series/parallel per the original), which deals with the issue nicely - and inexpensively.

Alternatively, at least in the U.S., it would seem that 12V field coils are easily obtainable at a good price (or just speak to AdminJeff .

Luke.