What's the advantage of 24volt system?

[fasttruck]

12 volt lightsn & 24v starter ? Sure! Check your average b61 mack with batteries and my mortal emeny the series-parallel switch. Provides 24 to start and then 12 volts for accessories. Also part of the charging circut so if one pair of batteries is dead (and the truck won't start) and the other is chared, s-p switch is probably the villian. First were mechanical switches then electronic switxhes offered then reliable 12 volt starters became available and most big trucks use 12 v systems today. Mci and prevost buses were also available with straight 24 v systems but i do not know if all of them were built that way.

 

[drgreg]

Vehicles developed after WWII used 24 volt systems in lieu of the 6 or 12 volt systems used durring the war. The change was made to enable the vehicles to support more electrical components such as more powerful radios which were being developed, but it also served to reduce the demand for blackmarket military truck parts since few civilian vehicles used 24 volt systems.
U.S. MWV pg 337

 

[steelandcanvas]

but it also served to reduce the demand for blackmarket military truck parts since few civilian vehicles used 24 volt systems.
U.S. MWV pg 337

I totally agree with this reasoning. I think you hit the nail on the head Drgreg.

 

[emr]

it is alot more than black market and probably not at all at the design level, it is for all things being interchangable and run, like said above radios all size trucks being able to be slaved, it is what the M series was all about, simple, all vehivles start much easier with 24 volt in all weather conditions, they thought of going to 36 in the past and recently for that very same reason, I believe our Northern cousins the Canadians run some 36 if not they sure have been testing it, and it has nothing to do with the black market, plenty is in writing about why, none mentions the black mrkt...

 

[drgreg]

What is being tested now is totally not relevant to reasoning from 57 years ago. A universal voltage is a no brainer and as stated 24 volts was selected to handle required loads. The info on the blackmarket is from a book, as ref. in my post, I did not just make it up.

 

[kendelrio]

Dunno if this has been addressed, but the voltage/amperage relationship is inversely proportional. The higher the volts, the lover the amps. Amps generate heat, which is bad in an electrical system. On our subs, we have tethers 10,000 feet long, and in order to not burn the fiber system up with the amp draw, we jack our electric output surface side to 3,000 volts to drop the amperage (and heat generated).

 

[drgreg]

WTB 3000 volt starter for deuce & 250 12 volt batteries.

 

[reddogkaiser]

QUOTE: I have never seen a big rig that was 24v either. Some maunfacturers may have made some prototypes but to my knowledge they never produced any in large numbers. One of the main reasons I doubt they did is you couldn't run the lights on any trailer on the market unless you changed the bulbs.

Actually, most kenworths in the 80's used a series/parallel switch and four 6volt batteries, the switch would start the engine on 24 volts then automatically switch to 12 volts for the lights, gauges etc. They were a HUGE pain in the a** with a HUGE failure rate!! The only good side was the starter, a 24 volt starter will spin longer with more torque than a 12 volt starter!!

 

[scootertrs]

My 2 bits.. We run Cats and Komatsus and Cases and other heavy equipment. All, with the exception of a couple of screens are 24 Volt. My deuce and my 5 ton are 24 volt. My duramax is 12 V... but 2 batteries in parallel. What I have found is that the higher the amp you draw, the thicker the wire you need. (for the same force or torque) Thus as someone earlier stated... Watts translates to HP, Watts also translates to Volts times amps... thus if you double your voltage your amperage need is halved and your wire diameter is reduced accordingly.

My biggest hurdle I have yet to overcome is... in a mixed 24V and 12V job site, most of the heavy equipment "mechanics" do the "plug and pray" method of jumping equipment. If you are not careful, diode bridges in alternators blow, batteries get cooked and worse yet... in this day and age of computerized engine and cab controls... your ace mechanic cooks your computer. In a John Deere excavator, the price can be upwards of $7500.00. for a momentary screwup.

We have actually retrofitted most of our equipment with large golf cart sized battery connectors and gotten away from the alligator clips. The jumper box for the equipment will only plug in one way and if it plugs , its corre4ct, if it doesnt... you can't make it go. Also I made some jumper wires for equjipment-equipment jumping that takes away the head scratching... you just plug it in and go... You would be surprised at the "inventive" ways that people try to jump a piece of equipment... even mechanics with dozens of years in the field!

I also built a battery tester-that allows you to test the 2 batteries simultaneously and indipendently while cranking... basically 2 12 volt volteters and a 30 volt voltmeter. Sometimes one battery goes bad while the other is OK. If anybody wants my schematic for this, I would be glad to post or send, just pm me. You cannot imagine how much money, time and aggravation this little gizmo saved me. It also helps diagnose faulty wiring or corroded wire issues.

My other 2 bits are... if a battery fails to start your truck once, and it was not because you left your lights on or your wiring was bad or your alternator is not working... replace it... don't screw with it, don't hope for a miracle. I cannot count how many alternators and starters have been ruined at my site simply because the batteries were bad.