Battery Question

[Trenton]

Hi All,

I just bought a '64 b model mack that has(4) six volt batteries on it wired positive ground. Can I replace the (4) six volt with (2) 12 volt batteries wired positive ground? My second question is what does it take to transform the truck from positive ground to negative ground?

Thank you in advanced for your help

Trenton

[randyp]

Hi All,

I just bought a '64 b model mack that has(4) six volt batteries on it wired positive ground. Can I replace the (4) six volt with (2) 12 volt batteries wired positive ground? My second question is what does it take to transform the truck from positive ground to negative ground?

Thank you in advanced for your help

Trenton

Hi Trenton, I dont know bout all involved in changing ground polarity, there are some on here who when they read this will clue u in, but I asked the question one time bout 4 batteries verses 2, and was advised I may have less cranking amps with just the 2, so I stayed with 4 on a 86 R688ST, 2 on each side. I hope you get a more expert opinion on it, I do know, stay on top of batteries and keep terminals clean and tight and will have less trouble with them. Prof. Rob gave an excellent dissertation on this subject a while back, so check the archives. Every now and then, Rob seems to be of some use on here. space cadet randy

[Underdog]

When I got my '63 F-model it had 2 12 volt batteries and a broken post on the series-parallel switch, so I decided to eliminate the switch and wire the starter direct 12 volt. I reasoned that money saved on a new switch could be spent on replacing the 24 volt starter motor with a 12 volt unit if needed. So far though I have not spent that money, as the 24 starter cranks fine on 12 volts.

Also, for ease installing electrical accessories and to avoid confusion with jumper cables,etc. I converted to negative ground. The starter is not polarized, and as I recall the voltmeter and fuel gauge wires are swapped for neg. ground. I used the Mack Service manuals for my upgrades as they have all the schematics for 12 or 24 volt start systems as well as pos. and neg. ground systems.

[Mike]

Hi All,

I just bought a '64 b model mack that has(4) six volt batteries on it wired positive ground. Can I replace the (4) six volt with (2) 12 volt batteries wired positive ground? My second question is what does it take to transform the truck from positive ground to negative ground?

Thank you in advanced for your help

Trenton

Trenton,

A good place to start would be the web-site called oldmacksrus.com click on Info, then click on B Model Info and you choose which diagram you want. The 24 volt pos. and neg. ground diagrams are there for your electrical pleasures.

Hope that helps.

mike

[RowdyRebel]

Hi All,

I just bought a '64 b model mack that has(4) six volt batteries on it wired positive ground. Can I replace the (4) six volt with (2) 12 volt batteries wired positive ground? My second question is what does it take to transform the truck from positive ground to negative ground?

Thank you in advanced for your help

Trenton

First of all, it all depends on how everything is set up. I've not ever done any work on a truck that old (just an old 6 volt single battery 8N Ford tractor), so I'm just going to talk theory, not specifics.

If all 4 positive terminals are daisy chained (++++), and all 4 negative terminals are daisy chained(----), you only have a 6 volt system. If you put two 12 volt batteries in, you can cook the electric system because it isn't meant to handle 12 volts. Granted, a truck that old won't have any electronics, so it won't be as bad as running high voltage through a newer truck, but the starter will turn fast and have a shortened life span, the batteries won't charge (6-volt generator and voltage regulator) and you may even have trouble keeping light bulbs from burning out.

Now if they are hooked up with 2 positive terminals daisy chained to 2 negative terminals (++--), and 2 negative terminals daisy chained to 2 positive terminals (--++), then you have a 12 volt system. In that case, hooking up a pair of 12 volt batteries (++) and (--) would work...although you may run short on cranking amps.

The easiest way to know would either be to look at how the batteries are connected, or to hook up a multimeter to see what the voltage output of the system is.

Now as for converting positive ground to negative, just remember that every motor on the truck will have to have the wires switched or they will run backwards. That may not always be possible, because (for example) if the starter grounds through the engine block to the chassis, you would have to rebuild the starter to change the polarity or it would spin the engine the wrong way whenever you turned the key. EVERY electric motor on the truck would give you a similar problem...windshield wipers...washer fluid pump...everything. If they have ground wires, you can make the switch easily...but for motors that ground direct, it gets trickier. Personally, it just seems like it would be a lot of work with no real added benefit....

[HK Trucking]

Now as for converting positive ground to negative, just remember that every motor on the truck will have to have the wires switched or they will run backwards.

That's true for the heater/defroster blower motor(s).

That may not always be possible, because (for example) if the starter grounds through the engine block to the chassis, you would have to rebuild the starter to change the polarity or it would spin the engine the wrong way whenever you turned the key.

That's incorrect. Starters are not polarity sensitive.

EVERY electric motor on the truck would give you a similar problem...windshield wipers

A 64 B model has air operated wipers...

.washer fluid pump...

Not applicable on a 64 B model.

.

[RowdyRebel]

That's true for the heater/defroster blower motor(s).

That's incorrect. Starters are not polarity sensitive.

A 64 B model has air operated wipers...

Not applicable on a 64 B model.

.

Thanks for the corrections. Like I said...I got no experience with them old trucks, just talking theory and potential problems he may run into.

[ThaddeusW]

Thanks for the corrections. Like I said...I got no experience with them old trucks, just talking theory and potential problems he may run into.

Just a little FYI on DC motors:

DC motors that are permanent magnet will reverse with a polarity change (like those in wiper and washer fluid motors). This is because the field polarity of the permanent magnets (they take the place of the stationary otherwise known as stator coils) does not change. In a starter motor, the stator coils are wound and not permanent magnets. The armature (rotor) coils are wired in series with the stator coils. Even if you reverse the polarity the motor will spin in the same direction because the stator and rotor coils always have the same magnetic field polarity. If you want to reverse a series wound DC motor you have to be able to reverse the polarity of either the armature or stator windings in relation to the other. This is impossible in a starter because the series winding is permanent ly connected internally.

There are a few different kinds of DC motor setups: series, compound and shunt. Series are the best for high starting torque because the load causes the armature to draw more current, but the armature and stator are in series. So as the armature current increases, so does the stator current which causes the starting torque of the motor to quickly build up overcoming the resistance of the load. They draw lots and lots of current and if ran with no load they will run away and fail catastrophically (just like a runaway diesel). Shunt wound has low starting torque but can be run with no load as it is speed regulated. The compound wound offers the best of both motors but is a bit more complex and therefor more expensive.

[Mike]

Just a little FYI on DC motors:

DC motors that are permanent magnet will reverse with a polarity change (like those in wiper and washer fluid motors). This is because the field polarity of the permanent magnets (they take the place of the stationary otherwise known as stator coils) does not change. In a starter motor, the stator coils are wound and not permanent magnets. The armature (rotor) coils are wired in series with the stator coils. Even if you reverse the polarity the motor will spin in the same direction because the stator and rotor coils always have the magnetic field polarity. If you want to reverse a series wound DC motor you have to be able to reverse the polarity of either the armature or stator windings in relation to the other. This is impossible in a starter because the series winding is permanent ly connected internally.

There are a few different kinds of DC motor setups: series, compound and shunt. Series are the best for high starting torque because the load causes the armature to draw more current, but the armature and stator are in series. So as the armature current increases, so does the stator current which causes the starting torque of the motor to quickly build up overcoming the resistance of the load. They draw lots and lots of current and if ran with no load they will run away and fail catastrophically (just like a runaway diesel). Shunt wound has low starting torque but can be run with no load as it is speed regulated. The compound wound offers the best of both motors but is a bit more complex and therefor more expensive.

VERY Interesting Thad.....very interesting and true. Thanks for explaining this.

mike

[RowdyRebel]

Just a little FYI on DC motors:

DC motors that are permanent magnet will reverse with a polarity change (like those in wiper and washer fluid motors). This is because the field polarity of the permanent magnets (they take the place of the stationary otherwise known as stator coils) does not change. In a starter motor, the stator coils are wound and not permanent magnets. The armature (rotor) coils are wired in series with the stator coils. Even if you reverse the polarity the motor will spin in the same direction because the stator and rotor coils always have the magnetic field polarity. If you want to reverse a series wound DC motor you have to be able to reverse the polarity of either the armature or stator windings in relation to the other. This is impossible in a starter because the series winding is permanent ly connected internally.

There are a few different kinds of DC motor setups: series, compound and shunt. Series are the best for high starting torque because the load causes the armature to draw more current, but the armature and stator are in series. So as the armature current increases, so does the stator current which causes the starting torque of the motor to quickly build up overcoming the resistance of the load. They draw lots and lots of current and if ran with no load they will run away and fail catastrophically (just like a runaway diesel). Shunt wound has low starting torque but can be run with no load as it is speed regulated. The compound wound offers the best of both motors but is a bit more complex and therefor more expensive.

Ya learn sump'n new every day...

[Trenton]

Thank you all for the information.

Trenton

[randyp]

Thank you all for the information.

Trenton

heh heh,,,see? I told you to just give it time, and you would get a world of information.,Theys gurus,thats all they is to it,,genius gurus! Fine Job gentleman! Philanthropist Randy