Why not 48V batteries?


#1

I remember back in the 1980’s there was much interest in moving from 12V to 48V. Why 48V? The voltage is low enough that it is not a shock hazard and it reduces the current by 1/4th for the same power. This reduces weight and cost by reducing the amount of copper. But here we are in 2016 still using 12V systems.


#2

Although many manufacturers were predicting a switch to 36-volt (lithium ion battery) / 42-volt (charging voltage) electrical systems, the changeover has not occurred, and the plans appear to have been canceled.[1] The availability of higher-efficiency motors, new wiring techniques and digital controls, and a focus on hybrid vehicle systems that use high-voltage starter/generators has largely eliminated the push for switching the main automotive voltages.[1] Applications that once were thought to require higher voltages, such as electrical power steering, have now been achieved with 12 volt systems.[1] 42-volt electrical components are now used in only a few automotive applications, since incandescent light bulbs work well at 12 volts and switching of a 42-volt circuit is more difficult.[1][2]


#3

Personally, I hope that all non-hybrids and non-EVs remain with the 12V system

At least during my lifetime


#4

it’s not a cheap undertaking to replace all wiring and electronics to adapt them to 48V. The cost vice savings probably are not advantageous to make the change.


#5

Agree with @TwinTurbo s post. I worked in the auto industry when “42 Volt” systems (36V batteries) were actively being considered. Lighting system guys wielded a big stick - huge investment costs - in those discussions. Lighting was one of the real killers. Still mostly incandescent bulbs at that time so the filaments would have had to be very thin, too thin, to survive vehicle vibration. LED’s pretty much fix that, now.

Another issue was limited savings in the wire sizes used to transmit power. There are limits of how small the wires can be and still not fail from vibration.

And then there is the battery. Lead acid was and still is the preferred starter battery.for a lot of reasons. Instead of 6 cells at 2.1 volts per, you need 18. That means a more expensive battery even in the same size and capacity.

Plus you needed to get all automakers, component suppliers and service professionals around the world to get on board with the whole thing. That alone would doom it to failure!


#6

If the starter motor was operated at 48 volts, that design would cure a lot of the “no crank” problem complaints we get here. 48 volt batteries would either require a different chemistry or more cells, both of which might have significant manufacturing learning curves. That’s probably the main downside. I’d guess higher battery voltages will be the norm in the future, but that trend will be competing with the apparently unstoppable trend of manufacturers switching their inventory to all electric cars, which already use higher battery voltages.


#7

People have enough trouble jumping cars, throw in another possible bad scenario, yikes!


#8

More problem with arcing too,18v seems to be the arcing threshold,plus thats fairly high voltage ,give you a pretty nasty shock .


#9

Three times the number of cells = three times the probability of a dead cell ending the useful service life of the battery before its time.


#10

Arcing was the problem I remember reading about. Like you said, above 18V an arc can be sustained, creating a fire and/or shock hazard.


#11

Yet the industry made the switch from 6 volts and positive ground to the present 12 volt neg ground.


#12

That was a very positive development.


#13

because the couldn’t get the amperage desired from a 6v battery to light and run everything that we expect these days from a car.


#14

General Aviation (Light) airplanes have been using 28 volt systems for decades now. Batteries are 24 volts, with twelve cells, typically. Advantages, as others here said, are better cranking, and smaller cables. Piper originally used aluminum cables for battery and starters, but a service bulletin made conversion to copper mandatory.


#15

Father In Law had a Mobile home, to get away from things, it had aluminum wiring, I suppose it worked well enough, but prefer copper. Was Mr Fix it for the apartment complex and mobile home.


#16

Aluminum is OK provided you use the proper coatings on the ends or fasteners so that you don’t get that galvanic corrosion when aluminum meets copper. The fire hazards were caused by not using the correct connectors. I’m pretty sure the main entrance cable here is aluminum 02 or something and the buss bars are aluminum.


#17

For light planes I can see the advantage of 28V - thinner, lighter wiring would be important on a plane. Every pound matters. The 12 cell battery is the same general size as a 6 cell car battery.


#18

So have “heavies”.
Aluminum was found to be dangerous due to galvanic corrosion at the terminations. It was tried for some years in house wiring too, and was made non-code-compliant for the same reason. Lots of house fires.

Lithium Ion is now under scrutiny for use in aircraft due to fires caused by lithium-ion array battery packs. As a matter of fact, it’s now under scrutiny for some other common applications as well. I just yesterday saw a news item wherein an SUV burned up when the cell phone being charged in it exploded and caught fire. The fire was scary huge.


#19

I am so happy that I have never had any problems with the Lithium Ion cells,the only thing I dont like is they dont seem to last as long as the MH cells ,maybe thats why Toyota went to the Li Ion cells in the newer Prius.
Reminds of a time when I had a Lawn Boy push mower you couldnt wear out ,I brag about how well it held up to the dealer,but it didnt seem to make Him very happy(I finally realized durable devices dont generate much profit )


#20

@kmccune. I have great memories of the LawnBoy push mowersm. My dad bought a new one in 1955. The instruction manual had wonderful blow-up diagrams of the engine, carburetor, and magneto. I mowed a lot of yards in those days. At the end of each season, I installed new piston rings, new magneto points and condenser,and a new needle and seat in the carburetor. The deck was magnesium and didn’t rust. With its 2 stroke engine, the mower was light and easy to push. Am owner could keep the mower going almost indefinitely. The mowers were easy to push making self propellsion unnecessary.