24-volt battery vehicles? 3

[felixc]

Hi,
are there countries where the working voltage in vehicles is at 24 volts? Or are there classes of motor vehicles, trucks, or maybe agricultural vehicles, that use 24 volts? One of my customers suddenly has concerns that the systems that I am working on could be used on 24-volt vehicles. My design actually runs from 9 to 18 volts, with transient suppressors for spikes at higher voltages.
Felix

 

[brett12]

why not just use a voltage regulator, like L7805 or L7812?

 

[nbucska]

Felixc: Add a cheap switching regulator !!

<nbucska@pcperipherals.com>

 

[schiao]

Class 8 trucks mainly use 24vdc for accessories and some 12vdc for low amp apps like communication or signaling devices.

 

[felixc]

Thanks guys for all the comments. The design has been done using a LM1572 from National Semi. It is a 500KHz switcher. With a switch to turn off whenever the voltage was exceeding 18 volts. I needed 1.5 amps at 5 volts. The product has a sealed casing, plastic, and is quite small. Power efficiency and real estate were important constraints in this design, as this was a retrofit of features that were external to the device. A couple of thousands of boxes have been produced with no troubles so far. Cross fingers.
With the emerging 42-volt standard, new switchers chips have appeared during 2003, that can handle higher input voltages. More will come in the future, I'm sure.

 

[wilg]

In the US Air Force, our
systems were all 28V.

 

[truck]

Current over the road trucks (Class 8) pretty much all use 12V systems - there are a lot of batteries but they are wired in parallel.



Truck

 

[finman]

UK military uses 24v apparently so that we can jump start HMMWV's that have a flat battery (Lerner 1 please note) Land Rovers for military use have 24v systems but the civvy versions run 12v.

I have a feeling that a lot of civilian heavy commercial trucks also use 24v but you'd need to check that out.

 

[bwain]

Most light aircraft went from 12to 24 volts in the 1970s as electrical systems were getting too heavy due to adding more features (radios, lights, heaters, sensors, etc.). The higher voltage allowed smaller, lighter wires and electrical equipment.

 

[nzsparkz]

24volt
European and Japanese heavy trucks.
Many Japanese small trucks and 4X4s.
Most earthmoving machines, cranes etc.
Most military vehicles.
Most large marine engines.
Rail engines.
Some large self contained agriculture equiment,eg combines.

12volt
Cars.
Most agriculture equipment, tractors etc.
Onroad USA trucks (I believe this is to allow the use of cheap readily available accessories, eg TV's, fridges etc)

Some vehicles used to have a 24v start 12v run system. This system used a series parallel switch to link the two 12v batteries in series for 24v starting, and in parallel to give 12v for normal running.

Working on both 12v and 24v systems I see the advantage of using 24v.
Starting is easier due to the higher cranking speeds that 24v systems usually have.
Tail lights are also brighter in truck/trailer units due to the reduced voltage drop in the wiring looms.

 

[tirby]

Gentlemen,
I have some equipment that uses cat 3512b engines that are 24 volt systems. The mechanic that works on these units wants to hookup 6 12 volt 55 watt work lights and pull the 12 volt off the center post on the 24 volt batteries(2 12 volt in series) I need some reference materials on unbalanced charging.

 

[tirby]

Gentlemen,
I have some equipment that uses cat 3512b engines that are 24 volt systems. The mechanic that works on these units wants to hookup 6 12 volt 55 watt work lights and pull the 12 volt off the center post on the 24 volt batteries(2 12 volt in series) I need some reference materials on unbalanced charging.

 

[ivymike]

Why not runs the lights in series instead?

 

[ivymike]

(in pairs, assuming each light wants 12V)

 

[tirby]

each light wants 12 volts
havent thought about running in series
my idea was to use 24 volt bulbs (less current, less drain)

 

[GregLocock]

Unbalanced loading of individual cells in a series battery is a recipe for disaster.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[abcd3286]

A common setup on larger truck is
24 V start to keep startr motor size down
12 V run to take advantage of all the 12 V stuff on market

 

[rmw]

25 years ago I had professional reasons for being intimately familiar with electrical systems in tractor trailer type trucks as well as busses in the USA (as well as in Europe). Back then, in the USA 12/24 systems which used a crossover relay called a 'series/parallel' switch to series 2 or 4 12V batteries to make 24V for starting (only) were quite common.

After the truck was started, the 'series/parallel' switch put all the batteries in parallel for 12V operation of the electrical system.

Battery technology improved, and not only do trucks no longer use four 12V batteries for 12 V start, they now commonly use only three. The weight savings of even one battery is significant.

I haven't seen a 12/24 volt start system on a modern truck in years, but I still have quite a few 'series/parallel' switches in my possession if anyone still uses 12/24V start.

The only heavy duty vehicles that commonly use 24 volt systems in the USA are MCI busses, the brand manufactured for and by Greyhound. Finding 24 volt bulbs and apurtenances for them is a pain in the neck for their owners, since they are not common to tractor trailers and not on truck stop shelves.

As an aside, I haven't seen any air starters in the last 20 years either in case anyone asks. Officially it was 19 lb. lighter than an electric start, but few people had the brass to use them. When their one battery went junk and it failed to start, there were two things to jump, electrics for the fuel cut off switch and an air line to recharge the starter air resorvoirs.

Now an opinion. European trucks back then (I can't speak for now) used 24 Volt electrical systems while the USA used 12. European fuel costs have been in the range of double that of the USA for about the same time period. Across the fleet of tractor trailers in Europe, the reduced weight of the electrical systems due to the use of 24V systems represents real weight. IF or when diesel fuel costs permanently stay above $3.00 USD/gal, look for 24V or 42V electrical systems in our rigs. It represents real weight savings across the number of truck/trailers in our country.

rmw

 

[truck]

There are still air starting systems around (one of the larger fleets still uses them), but they are not nearly as common as they used to be.

Truck

 

[pennpoint]

Well in MHO. You can bet on 42VDC systems on some, most then, on all cars and trucks.
42VDC driving all the auxillary equipment:
Fuel pumps
Lighting
Power breaks
Air Conditioning
Power stearing
Power seats
Power this
Power that
The only belt (aux) drive off the engine will be to the altenator.
I cannot say when but, it will come.

Regards
pennpoint

 

[IceStationZebra]

I concur with nzsparkz. In my 20 years of experience in the medium duty off road sector everything I have come in contact with was 12v.

The only exception was a military spec forklift, with 24v being a NATO spec. We even had to equip it with a NATO jumping receptical, which is one big round socket with both terminals, so young "jarheads" can't reverse the polarity and blow something up.

As for electric forklifts, there are several commonly used voltages. 24, 36, 48 and some 72