Batteries won't recharge during tow.

[Don A.]

Originally Posted by Sbrownstein

Mulling it over, it makes total sense for a TT.

Thanks never expected and strangely never received but always appreciated.

[mobilemike]

Find an area in a modern truck engine compartment to mount an inverter is not going to happen. Plowing holes in the cabin of an $80k truck for DC supply and AC output cabling isn't either. The logical place to mount an inverter is under the bed forward of the rear wheels. Plenty of space and out of engine heat and gas and oil. HOWEVER that position is already half the distance to the trailer and large DC cables and associated breaker is already required. You might as well size the wire correctly and just continue it to the trailer. The front of the trailer where the batteries are. Not 40 feet away. More like 20. Yes I know DC is calculated for both direction when picking wire.

Also shore power and gensets are for charging dead batteries. We are talking 5 to 10 amps here to maintain charge on the road to cover a running fridge. While driving 5 to 8 hours to the next plug in.

Technically it may not be the best but it is simple, effective, and cheep and most importantly within the capabilities of the general public.



If you want to start a section where we can muse over complicated over-engineered solutions to simple problems I am all for that.

[babock]

Putting in an inverter and running that from the TV is just a poor man's DC to DC converter. Who cares if you lose 15% in the conversion. Who cares if you even lose 50% in the conversion!


Or you can buy a DC to DC converter and mount that in the trailer itself but that's going to be more expensive.

[Sbrownstein]

Originally Posted by babock

Putting in an inverter and running that from the TV is just a poor man's DC to DC converter. Who cares if you lose 15% in the conversion. Who cares if you even lose 50% in the conversion!


Or you can buy a DC to DC converter and mount that in the trailer itself but that's going to be more expensive.

Nope, for it to work, you are going to have to mount it in the TV. The problem is you cannot supply the necessary current to the TT at 14 volts.

[babock]

Originally Posted by Sbrownstein

Nope, for it to work, you are going to have to mount it in the TV. The problem is you cannot supply the necessary current to the TT at 14 volts.

Hence the beauty of a DC to DC converter. It doesn't need to be at 14V. It can be less than 12 even. You actually want it as close to the batteries you are charging as possible. The DC TO DC convertor converts for example 12V at 20A to 14V at 17A minus conversion losses.


We used Dc to DC converters all the time on the chassis and circuit cards we designed. We had an inaccurate 20V feed at high current across pins with loss and then had DC to DC converters on the circuit card itself supplying the accurate voltages to our components.

[DWeak]

I apologize for not reading all of the replies so if this is redundant just skip it! Anyway if your trailer is equipped with a battery shutoff switch, your batteries will not charge as you travel unless it is "on". Dealer forgot to tell me that one on the walk thru. Good luck.

[Sbrownstein]

Originally Posted by babock

Hence the beauty of a DC to DC converter. It doesn't need to be at 14V. It can be less than 12 even. You actually want it as close to the batteries you are charging as possible. The DC TO DC convertor converts for example 12V at 20A to 14V at 17A minus conversion losses...

Guess you are right, a good boost converter will trade current at a lower voltage for the voltage at a lower current. 20 amps is a big one but Thermo King has a 20 and 35 amp model for tractor trailers with battery powered lift gates. Has its own 3 level charge profile and prevents reverse current flow to the source batteries/alternator. Looks like you can get a 20 amp version on ebay for a couple of hundred bucks.

[Don A.]

Originally Posted by mobilemike

Find an area in a modern truck engine compartment to mount an inverter is not going to happen.

Well then run 4/0 welding cables back to the back and mount it in a waterproof box in the truck bed. That will work too. Or mount it on the front of your trailer or wagon you are pulling. Just trying to save you some money. No matter where you mount it, you'll get the AC a modern converter back in the trailer can take full advantage of to keep the battery properly charged and desired appliances running.

Or buy a complicated trucking DC-AC AC-DC for half a grand and up. This is an option and not a blueprint for future installs. It works and , all up to the purchaser.

Regarding "complicated over-engineered solutions to simple problems", if you can't install an inverter, I'd certainly farm out re-provisioning thicker replacement for the existing stock #12 wire back to the trailer, or utilizing fancy heavy amperage connectors at the various connection points.

Just remember these important formulas:
E = I * R (volts = amps * ohms)
(where ohms remains constant for the equation)
P = I * E (watts = amps * volts)
(calculating power)
complicated over-engineered solutions = one I didn't think of
(a joke)

[mobilemike]

4/0 welding cable for 20amps 16 feet to the bed of the truck. That is rich.

[Don & Pat]

Same here. Lots of solar that charges the batteries all the time. Its nice knowing when you park the 5th wheel for the winter that the batteries stay charged.

Enjoy the road. We sure do.

Don

--------------

Originally Posted by rarebear.nm

Increasing the size of the hot lead may help some, but keep in mind you must also replace the ground wire with the same size as the hot lead. I do not think you'll ever get enough volt and amps to do much recharging. IMO the math does not work out too well.

I have 1050 watts of solar on the roof and that keeps the batteries charged. I don't even use the converter anymore.

[Don A.]

Solar is the question and that is what do you do when there isn't any solar?

Constant rain and cloud cover, particularly in the Pacific North West will leave you with a cold dead battery. Then the generator is the answer, unless of course you don't have a multi stage converter or the 2-3 days to charge or your neighbor doesn't like generators and appears to have an itch of a grudge and from all that, a bone he needs to pick with someone.

[rarebear.nm]

Originally Posted by Don A.

Solar is the question and that is what do you do when there isn't any solar?

Constant rain and cloud cover, particularly in the Pacific North West will leave you with a cold dead battery. Then the generator is the answer, unless of course you don't have a multi stage converter or the 2-3 days to charge or your neighbor doesn't like generators and appears to have an itch of a grudge and from all that, a bone he needs to pick with someone.

As posted above somewhere, I wrote we spend four months this past summer in Canada and Alaska. Whereas, I have not RVed in the costal areas of the NW yet, can't make a statement directly about our system in that area. However, in Alaska where we experienced multiple days of constant cloud cover/rain & snow our solar panel alone kept everything charged even though we ran the furnace every night. The converters have ben turned off at the breakers since the solar was installed.

Different brands of solar panels respond differently to use of indirect and scattered light. I install 3 Silfab 350 watt panels on our 5th. On a typical morning our batteries were fully recharged by 9 - 10 am. Only once did it go a few minutes past noon.

We do carry a generator for backup and to run the microwave. In the four months we put on only 24 hours on the generator.

[Don A.]

Solar is not 100% fool proof. Even if the cells were able to process moonlight you will find those "once in a lifetime opportunities" to park somewhere in an ideal location that is shaded and there is no 110V outlet to be had. At this point you have to either walk away from the spot or run the generator, the required length of time each day depending on the characteristics of the converter and capacity of the battery bank.

I am a full-timer for over two years now, a part-timer for 20 years before that and recently covering most of N. America. While I only use my generator and 3-stage 70A 14.8VDC converter/charger 2-3 weeks out of the year, to me it is worth the investment to have a back-up power source.

No solar is made that works in the shade. And I have two laptops and a furnace, water pumps, lamps, inverter, etc with 500W on a 23' motor home and while on black cloudy days I also see a trickle of a charge, but it won't stay up with my own personal demand. Doubling that would not resolve my issue either.

If you are able to cut back enough on the days of dark cloud cover that you can exist on the reduced charge, congratulations for properly managing your sole energy source. I'm not so willing to do so if there is a back-up method to keep my batteries up.

For those reading this and deciding perhaps for the first time on your power options, as a full timer now I can say my solution has been 100% effective. If you want to chase away the clouds, always ignore the shady camping spots and try your luck with solar only, then go for only solar as an energy source but realize there is risk involved. If part of that risk is a freezer full of thawed food, a week of warm milk and lunch meat, or that same time frame with no heat, then judge your own risk acceptance. It will be different for each of us.

[rarebear.nm]

Originally Posted by Don A.

No solar is made that works in the shade. And I have two laptops and a furnace, water pumps, lamps, inverter, etc with 500W on a 23' motor home and while on black cloudy days I also see a trickle of a charge, but it won't stay up with my own personal demand. Doubling that would not resolve my issue either.

If you are able to cut back enough on the days of dark cloud cover that you can exist on the reduced charge, congratulations for properly managing your sole energy source. I'm not so willing to do so if there is a back-up method to keep my batteries up.

Solar technology is rapidly changing. As for no solar working in the shade: that's only partly true today. Many companies are selling bi-facial solar panels that have exposed solar cells on both sides. The brighter sunny side and the darker underside.

https://news.energysage.com/bifacial...-need-to-know/

The bottom side does not double the output, but is enough to make bi-facial panels economical in some installations where there is enough reflected light coming back at the bottom.

I chose residential/commercial grade solar panels over common panels sold for RVs. I spent about three months planning and designing my system prior to installing it. I had done my calculations for using it in Canada and Alaska with low sun angles, etc. It has exceeded my expectations. Many solar installations I've seen and read about are poorly designed and badly installed, at least IMO.

The only things we use the generator for is the microwave and TV. Computers and everything else is on the 12 volt system. If I replace the TV and DVD I'll install 12 volt versions.

I have 460AHr battery capacity and have two converters, a PD9245 and a PD 9270 wired in parallel, neither one is used anymore.

Since everyone's electrical usage is different your milage and experience will vary.