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

 

[GregLocock]

Yes, trucks often use 24V. I expect tractors do as well, but I can't remember. Fork lifs use 48V. Soon some cars will be using 42V. Cheers

Greg Locock

 

[pbloore]

As Geg said, Trucks (Goods Vehicles) often use a 24V system but no cars that I can think of (with the possible exception of some of the big 'trucks' used in the USA).

42V systems are one of the big pushes for the future for efficiency and weight saving reasons, but there are a number of practical problems that have delayed the volume introduction into the market.

 

[patdaly]

Arent Military vehicles in the US either 24 or 28 V?

 

[felixc]

Thanks for the answers. A sub-question that I should have asked along with the first one: in such vehicles with 24 volts, is the cigarette lighter socket still at 12 volts? My instrument would plug in there. Is this socket a standard at 12 volts?

 

[evelrod]

I recently had a chance to check a few tractor/trailer (trucks) rigs to see what voltage they were using (a result of a post in another forum). What I found was an almost universal use of 24V with a couple of exceptions. My youngest, now disability retired from the US Army says that all the vehicles he came in contact with were 24V. That was my experience of many years ago, also.
As a kid on the ranch and, later on my father-in-law's farm the tractors were 12V but, they were rather old and small in comparison to some of todays units.

Rod

 

[oab]

Felixc. The 24v systems in trucks are all 24v. Some use an inverter to supply 12v for radios etc.
Harvey.

 

[harrisj]

felixc / patdaly:

Not only US Army trucks but almost all land-based military vehicles world-wide have 24V batteries.

There is some comfusion about 24 / 28V. 24V is the nominal battery voltage; with the engine running, you get 28V. Equipment is therefore specified to run successfully between 18 and 32V for military equipemt in UK.

Lots of larger pleasure boats use 24/28V systems also. It's partly due to the need to crank large diesel engines - lots of amps at 12V!

Cheers - John

 

[burman2k]

There are some tow-trucks that uses 24V (two 12V) to jump start the vehicles in cold weather (very remote areas). So if the vehicle has a dead battery (low SOC or open battery), you could see a voltage higher than your protection circuit rated at 18V.

 

[dkelly]

In a previous life, I worked on a offroad/mining vehicles that ran two 12 volt batteries (24 v) for the starting circuit, and then ran 12 volts for the accessories/communications radios. I suspected that these where a compromise/oversight design based on what was available for the right price. The system worked well, but you always needed to have your voltage meter at the ready.

 

[HDS]

What is the SAE standard number for cigertte lighters / power outlets in cars? It might say what voltage can come out of there.

Do not worry about it. All the things I have seen designed for cigertte lighters didn't worry about 24V.

 

[felixc]

Thank you guys! It looks like 24 volts may be found at many places. I will add a high-side switch to turn off the device if the voltage exceeds 18 volts. In addition to a TVS for surges, and a polyswitch for short circuit protection. So it won't work during overvoltages but it won't break, with hopes that the owner will figure out that something may be wrong.

 

[patprimmer]

All 24 volt systems I have seen, run 2 X 12 volt batteries in series. It's pretty easy to run a circuit from one of the batteries only. Regards
pat

 

[harrisj]

Pat

Yes you can do this and it works. Remember you're charging in series and therefore both batts will get the same charge energy. But you're depleting one that also provides the 12v supply. Eventually you end up with one good and one flat battery, unless you devise an off-line system for charging at 12v in parallel.

Better solution is to use a 24 to 12 voltage converter. These come in 2 types - the cheap ones are inefficient but it doesn't matter unless you're using something for long periods off charge. The better ones are switch mode units which are around 80 - 90% efficient. Get them from auto or marine stores.

Cheers - John

 

[mbenoit]

don't know about electric vehicules but what I know is that
for forklift trucks you have dc motor controllers that work
at different voltages : 24 Volts, 36 Volts, 48 Volts , 72
Volts , 80 Volts. depending of the importance of the truck
and the technology of the controller is different
(mosfet, thyristor, transistor)
MB.
--

http://matthieu.benoit.free.fr/

 

[voltair]

I agree with harrisj about taking 12V from one of the two 12V in series. The advice from vehicle manufacturers is never to do that. Always use a 24v/12v converter. The exception being that it is ok to connect the memory of the radio to one of the batteries due to the very small current used.
Incidently, in Europe, all heavy trucks and buses(7 tons and above) are all 24v, probably due to the large torque required to turn the engine in cold weather.

 

[Rob45]

Don't know which commercial trucks in the U.S. use 24V, but the largest US-owned manufacturer of Class 8 trucks - the largest trucks - do NOT use 24 volt systems. We use 12V exclusively.
Lots of 12V batteries, but only 12V total.

 

[nbucska]

Felixc:
If your design works with 9 to 18 V , it must take a fairly
low current; could you please tell us how much it is?

<nbucska@pcperipherals.com>

 

[Lerner1]

All Military-series (or M-Series) vehicles used by the United States Military run on a 24V system. This is so our troops can get a jump start and can just start other colilition vehicles because many foreign countries have start 24/ run 24 vehicles. Now although the HMMWV is 24 volt, the Hummer (civilian version) is a normal start 12, run 12 system. But vehicles like the M113 Armored Personnel Carrier, M1A1 Tank, M1078 LMTV, and M35 &quot;Deuce&quot; transport truck are all start 24, run 24.

SSgt J. Lerner
Vehicle Maintenance, USAF

 

[Xtrema]

http://www.sae.org

has a hotlink to info on 42v battery. Looks like the coming thing. Should you design for this higher voltage now so the instrument works in the future applications?