Automotive Industry migrates to 48V electrical system

I was asked by my boss,the owner of a MSS, to find out why the self proclaimed "best technician" was working on a radio for days. Seems he applied 72v to a Motrac unaware that the locomotives used a Dc/Dc inverter to go from 72 down to 12 v. Then he argued with me about how I didn't know what I was talking about. The Motracs were rugged and a half dozen components fixed the radio. He had put 6ea. 12v car batteries in series....

 

That would work fine if it had been an AAR Motrac, like most of the Class A railroads used. This must have been some square-wheel wooden axle line.

 

The stall preventer dive is a feature! Boeing calls it the "ground locator" feature.

 

I watched the video and can only say that is I'm not surprised. I lived and worked in Silicon Valley in the 1990's and saw my share of immoral and unethical stuff going on.

 

Wiring panels in parallel could lead to the panel getting more sun taking all the load (due to having higher voltage), as well as the possibility the panel in stronger light might force reverse current through the other panel, potentially damaging it. Diodes ought to prevent these problems, but the voltage drop across a silicon diode is similar to the voltage produced by a solar cell. Likewise, wiring them in series means both (all) panels will potentially carry more than their rated current. The correct way to do this is to wire each panel to a solar panel controller, then wire the outputs of the controllers in series or parallel as needed to provider higher voltage or current.

Attaching the panel without clearance behind may lead to overheating -- airflow behind the panel is important for controlling temperature when it's in direct sun.

 

I beg to differ. First of all, on one solar panel, numerous solar cells are connected in series and a number of those series strings are connected in parallel. If connecting solar panels in parallel could damage them because one panel gets more sunlight than the other, then one panel could be damaged if a few cells are catching shade. But they don't. These individual string in a panel have reverse bias diodes in parallel with each string to prevent damage caused by partial shading.

Also, it is common practise to connect solar panels in an installation in series and connect the entire string to an inverter. That's how it's done on my house and 20 others around me. Some inverters have two solar panel connections and take two strings. It goes without saying (I hope) that ifo you connect two or more panels in series, that they should be similar panels with the exact same current rating.

Also, a solar panel is not a simple voltage source. It can best be seen as a complex voltage and current source, delivering power at an optimal load. So it's perfectly fine to load a panel to force the voltate down until a certain current is reached where the power is at maximum. Compare it you the output of your transceiver loaded with an optimum of 50Ohms

 

That's what I thought, panels can be connected in series.
If they're the same voltage and current and one panel is slightly shaded, then it shouldn't be damaged by the panel in full sun right?
Back on topic, I see the move to 48v to be quite the undertaking since there's a LOT of equipment out there that uses 12V or 13.8V.

 

https://www.castanet.net/news/Skywatching/252819/Super-sized-solar-storms

What else is there to say?

 

Sorry, "Hammy", it's been demonstrated, time, and time again.

If you want to "believe" something against evidence, feel free to do so ... this is just willful ignorance, or stupidity, at this point on your part.

 

The important points is Holmes is NOT the 2019 poster child for 'inventors'.

 

Agreed, The monster Ni-Cad used to spin the 2080 HP Turboprop engines to life took unbelievable starting current each. We'd spin 1.... then turn on its Generator and put bug juice back in the battery to ready the bat to spin 2... Just before starting #2 we'd turn the generator on 1 off. The generators were the 10HP DC starter motors on each engine used in reverse.... This process was only used if we were at an off-world location without a proper cart.

We routinely started with a CART .... Well the batteries in fact would lose capacity... Due to all the cart starts day in and day out. The rest of the time the batteries just powered lighting and the radio rack before start...

The maintenance department had a HUGE battery load with big heating coils. During a prescribed service interval the batteries were deep cycled to "X" much lower juice and then recharged under controlled conditions. That cured most memory issues. Without this battery maintenance thousands of dollars worth of battery would have been a throw away in 2 years. They could get 10 years out of a properly maintained battery...

More importantly proper maintenance lessened the chance of a cell short, thermal runaways and battery explosions. Which any pilot worth their salt would prefer to avoid. Dying at the hand of the energizer bunny beating his drum is not my idea of a good way to go. If you read all the posts I've made about my experience with big Ni-Cads in this thread you'd see this is a real potential issue and threat.

IN the meantime. I went to the toolbox and drug out my Fluke Networks Pro3000 cable toner. I have the case of a disappearing hot wire in an 1896 DC lighting 3-way switch now being run on AC... So I'm going to tone out the cables. When I power the system from below from the main panel it works, but there's no neutral in the switch boxes... One of these had a round switch u turned a knob for the 3 Way. No Box. Well Code now requires neutral in switchboxes of 3 Way circuits... It would be a wonderful test feature in my case.... BUT the downstairs switch is fed off the Basement Main, the upstairs switch where the neutral is for all the lights ran from the Subpanel... I get proper voltage switching, however the AFCI/GFCI breaker in the basement Main panel trips when I place lightbulbs on it... I need BOTH hot and neutral out of the same panel. ANOTHER NEC code requirement. I just wanted to see it work. There is a BUNCH of K&T wires heading down al one provided power to the main for switch... BUT the toner from the FLUKE's 9V battery is the original from when the toner was purchased in 2005. The bottom of the case is all humped out and no toner. (Duracell) The sensing wand however has an EverReady battery and it works just fine in both units. I need to walk to the store now to buy a 9V'er... GEEZE. Batteries should last forever. sigh

Erika DD

 

I am not sure NiCad airplane batteries are still a thing. I read plenty about thermal runaway issues, but the turboprop I flew had a nice Concorde lead-acid battery that was a drop-in replacement for whatever NiCad they had originally wanted to use. Never had an issue with one and never a hung start When I worked for Piedmont Airlines my favorite toy was the mobile generator tractor. It was by far the fastest piece of ground equipment with a big engine and a four speed I think it could put out up to 400 amps at 28 volts. If memory serves even that wouldn't start the 737s, it would start the APU. If the APU was dead we had a huge air tank/compressor cart that I hated. If the hose popped off the airplane it would whip around and beat the crap out of you

 

48 volts would be nice to run a big amplifier.

You could smoke the electronics in your automobile, And the one next to you.

 

Yeah the Ni-Cad is a Dinosaur Prehistoric thing of the past in big power systems... Of my 10,000 flying stories, maybe 100 of them are battery or power related related. Yuck. I checked on the planes I flew and they now all have Li-Ion conversions for them. The planes with them nose mounted just made their W/B issues even worse than with the L/A or Ni-Cad in there. I never had to mess with the carts, we always had our Maintenance Guy at each station so he'd deal with details, especially things that took a huge ladder to deal with like engine cowl plugs and covers and checking and adding fluids when necessary. We had big heaters with long canvas ducts over 12" in diameter that the mechanic would pull onto the flight deck... It was nice to not FMAO while freight crews loaded us.... Have a nice day. Erika DD

 

That is your opinion, to which you are entitled................