Tell me if I am crazy Solar RV Escape module

[j-c-c]

The 12V inverter in my application would only be for backup of very rare use, in order to reduce the outcome you note above. It's mainly to back up independently the 48V 2800W solar system in case it ever when offline for whatever reason.

[freebeard]

How would you ensure the backup inverter wouldn't drain the battery enough to prevent the engine from starting when required?

With a latching relay, but I'm not prepared to explain how.

[j-c-c]

Maybe, but on this one item, the solution KISS is my motto.

[JSH]

Originally Posted by Piotrsko

is this a financial decision or a practical engineering one? Dc to Ac then back to Dc conversions are really lossy and expensive for all the pieces parts involved. Suppose you could build your own supercap voltage multiplier and PWM stepdowns, but all the voltage multiplier circuitry I have experienced is not that high currents and really fussy about parameters.

I'm doing something similar but I already have a 12V setup because I'm starting with an ambulance. There is a charger for shore power and a full sine wave invertor that powered the medical equipment.

The sticking point for me was how would I charge the 12V vehicle system from the 48V house batteries. There are 48V to 12V DC - DC inverters but they cost quite a bit and I'm not keen on finding room for even more hardware and cabling. I'm planning on just using a standard 120V to 12V battery charger plugged into the house system. Yes it is very inefficient but I already have on and I'm running a very oversized 48V system.

I'm also a fan of K.I.S.S.

[cRiPpLe_rOoStEr]

Considering how high usually are the electrical loads on ambulances, it's quite surprising a 24 volt setup similar to most military vehicles and medium-duty commercial trucks is not implemented as standard.

[JSH]

Originally Posted by cRiPpLe_rOoStEr

Considering how high usually are the electrical loads on ambulances, it's quite surprising a 24 volt setup similar to most military vehicles and medium-duty commercial trucks is not implemented as standard.

The problem is the cost of transition - same as with light duty vehicles. The bulk of automotive electronics are 12V so they are cheaper than low volume 24V or 48V systems.

While some MD commercial trucks in the USA have 24V battery systems they are still running 12V electronics. Only the charging / starting loop are 24V. For the cab and chassis components the voltage is stepped down to 12V - again to save cost.

[cRiPpLe_rOoStEr]

Sure some devices such as lighting, "infotainment" and other accessories to which 12V is mainstream would remain that way, but for other high-intensity electrical loads it seems justifiable to switch to 24V. Yet with so many new vehicles featuring a 48V MHEV setup it's more likely that 48V will become more relevant than 24V soon.

[j-c-c]

I covered a lot of this hassle discussed here in another thread, that mostly related to the project in this thread.
Fla statue 316.515.3a states among other things a straight truck is limited to extreme length of 40' excluding safety and energy conservation devices approved by the department.
Elsewhere statues state a 2 axle RV's length is controlled by Statue 316.515.3a.
Elsewhere, "department" is defined as FLHSMV, Florida Highway Safety and Motor Vehicles.
So many weeks ago I began my quest to find out what exactly defined/determined what was an "energy conservation device approved by the department".

1. First stop was a call to the county's DMV, no clue but suggested I speak with county department manager.
2. County DMV manager had no clue, suggested I call Tallahassee FLHSMV.
3. Calling Tallahassee, after on hold for one hour, and requesting first my DL or VIN number they answered and had no clue what the answer was, suggested I call Regional FLHSMV DOT office in Palmetto Fla, that does "inspections", whatever that means.
4, I called Pakmetto 10:00am, waited for hour, the very polite lady did not have a clue, but took my name number and my question and said someone would call me back regarding the matter. I asked would that likely be today, she said yes, and definitely by tomorrow.
5. After no call back, I emailed my question and request for assistance to Molly Best, Director of Communications for FLHS MV in Tallahassee,
4 weeks later still no reply
6. Three weeks ago, I sent a certified letter FLHSMV in Tallahassee, repeating my requests. No reply as of today
7. Today I visited the Ft Meyers Regional FLHSMV-Florida Highway Patrol Office (since likely they would be the citing agency on the side road) and requested the opportunity to speak directly with a "Commercial Vehicles" (DOT) patrol officer.

The conversation was rather strained and unfruitful. The officer stated among other things, after first calling a number of people for over 1/2 hour to research my question, she stated:
She has been trooper for over 20 years, straight trucks do not get "energy conservation devices", only semi do, why would I want to install one, they don't save any gas on a straight truck, when I said I disagreed, she said it was a "fact", also stated I was not listening to her because she was a women, she did attempt to educate me as to what an energy conservation device was (which was never the issue), and was rather condescending considering the officers other unsupported statements, and that "energy devices" are only approved by the Department if the original Chassis manufacturer approves them, which I questioned how does that work, because in most cases, the trucks/chassis are built and shipped unfinished without any bodies, to be installed by other vendors?

The officer said it doesn't matter, must be an original chassis manufacturer, which I find preposterous. I asked her if this requirement is retroactive, and what happens if it's on a truck/trailer say from 80's, the officer said it might be grandfathered in in some cases, but she did know which ones.

The system in Florida is clueless.

[freebeard]

Maybe it's time for some malicious compliance?

Unbelievable House Truck Transforms Into Fantasy Castle

[JSH]

Originally Posted by j-c-c

I covered a lot of this hassle discussed here in another thread, that mostly related to the project in this thread.
Fla statue 316.515.3a states among other things a straight truck is limited to extreme length of 40' excluding safety and energy conservation devices approved by the department.
Elsewhere statues state a 2 axle RV's length is controlled by Statue 316.515.3a.
Elsewhere, "department" is defined as FLHSMV, Florida Highway Safety and Motor Vehicles.
So many weeks ago I began my quest to find out what exactly defined/determined what was an "energy conservation device approved by the department".

Energy conservation devices are aerodynamic aids. They work on straight trucks as well as trailers.