RV power, solar, alternator and Shore power charging

[zdavesf]

Hello all, I am hoping some of you can help me or even guide me to another forum where this topic may be more appropriate. Thank you very much.

I would like to re-wire my 19' 1982 Datsun RV's power system as it just doesnt do what i want it to do. As far as capacity I really dont need a tremendous amount as this setup up will mostly just power lights, laptop, waterpump, small furnace fan in the cold and a small tv (no satelite). I do mostly dry camping (a week or two at a time) but I typically am driving to a new location for 4 or 5 hours every other day. as for charging i would like to have the three options availabe:
1) I would like to perminently mount a 120watt (or there abouts) solar panel to the roof (i know may not get the best angle...)
2) 120vac to 12 converter/charger ( i currently have the original converter it works but im pretty sure it will start boiling the battery if i leave it plugged in for more then a couple days)
3) charge from the alternator. right now it is wired with a solenoid 65amp capacity i believe) but its only 14 awg wire which seems pretty small. but its been there for 30 years so im guessing not much current is passing through it (i know it works cause i have checked it).

With all that being said my question is:
I think i need to use an isolator (ie BIG diode) to prevent any of these three chargers backfeed into one another and blowing up. I like the idea of the solenoind allowing the rv battery to boost the starter battery, but i can always put a 150 amp bypass switch with a fuse/breaker to do it manually (I have read on this forum that it is frowned upon to parrallel these batteries as you could get a huge current dump between the two, so an isolator is prefered.)

so should i connect a isolator between each of these chargers and the battery (terminals A B C and D on my drawing?
if so wouldnt these chargers need to be able to increase there charging voltage by about 0.6volts to compensate for the diode drop in the isolator?
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Thank you for all your help

[Sunking]

OK I can help you. Rather than answer your questions point by point here is what I would do.

• For each 12 volt 100 AH auxiliary battery install 100 watts of solar panel. So for example let's say you install 2 Trojan 6 volt 220 AH batteries, back them up with 220 watts of solar panels using a MPPT charge controller. Mount the panels flat on the roof.
• Install a battery monitor so you can monitor the aux battery voltage without having to open something up.
• Install a battery isolator between your starting battery and aux battery to allow you to charge the Aux battery from the vehicle alternator in the event the solar panels cannot keep up with demand. The isolator prevents you aux battery from supplying the vehicle starter and electrical circuits like head lights, radio, ect...

[zdavesf]

Thank you for the responce.

So what your saying (or you did not mention so im taking it as dont worry about it) is that If I have shore power (120VAC converter/charger) and the solar charge controller both connected to the rv batteries and charging at the same time i dont have to worry about them back feeding?

If this is an issue I can always use a relay/solenoid to disconnect the solar controller if need be i guess (or a switch but i like having things automatic because i tend to forget )

Dave

[Naptown]

Look into the marine chargers/inverters. some of these have very sophisticated battery monitoring systems will transfer to charge automatically when plugged in and switch to battery when unplugged. These are always used with an alternate charging system (engine alternator) And I believe some also can have a solar option but not sure.
I had one on a sailboat it was a Xantrex a bit pricey but worth it.
I would have a battery selector switch so all batteries can be charged at once but only house batteries are used for the inverter. (To prevent running down the engine starting battery.)

[Mike90250]

Most cheap inverters cannot be connected to a grounded system, only the battery - (minus) terminal can be grounded. Before you buy an inverter, make sure it will accept your wire scheme. I know most pure sine inverters ($$) have a transformer in their output, and can be properly grounded without letting all the "magic smoke" sealed inside them, escape.

[ballyboing]

hi there. i'm not sure if i'm reading this right. i'm also about to wire solar to a rv trailer, is it possible to go from the 1)solar panel to 2)charge controller to 3)battery bank to 4)inverter to 5)mains 120v input of the rv. ie replace the lead from shore power with the lead from the inverter. or will this create a problem as this will create a loop?

i've just spent an hour trying to draw a diagram on paint but i'm no good at it. it looks like spaggetti and lego.

thanks

[Mike90250]

hi there. i'm not sure if i'm reading this right. i'm also about to wire solar to a rv trailer, is it possible to go from the 1)solar panel to 2)charge controller to 3)battery bank to 4)inverter to 5)mains 120v input of the rv. ie replace the lead from shore power with the lead from the inverter. or will this create a problem as this will create a loop?

i've just spent an hour trying to draw a diagram on paint but i'm no good at it. it looks like spaggetti and lego.

thanks

You HAVE to have some sort of interlock or safety in the shore power section, because if you ever connect Hover Dam (shore power) to your battery powered inverter, it will take a long time to get rid of the stink from the smoke.

[ballyboing]

thanks mike-i've got some big windows so geting rid of smoke shouldn't be a problem.
or on the other hand i've designed up a system that will allow me to have a few sockets running from the inverter and then just use the battery to do the rest thereby unplugging the Shore power altogether.

[inetdog]

thanks mike-i've got some big windows so geting rid of smoke shouldn't be a problem.
or on the other hand i've designed up a system that will allow me to have a few sockets running from the inverter and then just use the battery to do the rest thereby unplugging the Shore power altogether.

The fact that you are using a DPDT relay to simultaneously switch both the hot and neutral of the AC sockets between shore and inverter power looks like it should take care of any grounded-neutral issues as well as any interconnection of hot wire issues. Just make sure that you do not plug anything into the outlet that has a three wire cord and also has an internal connection (short) between neutral and ground, since that will also trigger smoke production.

[laptopbatterystore]

Ways to Charge a RV Battery When Camping

Run the engine. RV systems with two batteries are equipped with a solenoid device that manages power generated by the alternator of the running engine. The power is routed first to the chassis battery -- starting the engine is always prioritized -- and then switched to the coach battery when the solenoid senses the chassis battery is full. Running an RV engine -- even on idle -- is typically fuel-costly, and therefore not an economical option, but it may be necessary if a shore connection is unavailable.

[coolgee6]

cool

charge from the alternator. right now it is wired with a solenoid 65amp capacity i believe) but its only 14 awg wire which seems pretty small. but its been there for 30 years so im guessing not much current?