#97163  by Neddy
 Mon Jul 27, 2015 10:07 pm
This schematic diagram has more detail and colour-coding makes it easier to understand.


The left-hand rotary switch selects the power source. The default position is "Inverter".
"Mains" is selected when you are plugged into the grid. This makes the dotted Red connections which do 4 things :-
(1) Mains power is delivered to the RV power sockets.
(2) The 230v/24v Charger is turned on.
(3) Charger output 1 is directed to the Starter battery.
(4) Charger output 2 is directed to the House battery.

The right-hand rotary switch controls the Inverter. The default position is Off.
(There is no point running the inverter if you are not using it).
When free camping, 230v needs are supplied by powering the inverter from the House battery.
When switched to "House Battery" the Green connections are made and :-
(1) The inverter is turned On.
(2) 230 volts is delivered from the inverter to the RV power sockets.

If you want to charge the House battery when motoring, the Inverter switch is set to "Starter Battery" (Alternator).
This makes the Yellow connections which do 3 things :-
(1) The inverter is turned On, powered by the Starter battery/Alternator.
(2) The Inverter output is directed to the 230v/24v Charger.
(3) Charger output 2 is directed to the House battery.

It is good to have a pilot light to show when the Inverter is turned on. This diagram has two neon lights, Amber to show that the inverter is running, powered by the House battery, and Red when the Inverter is running, powered by the Starter battery/Alternator. You could even have a Green neon to show when Mains power is connected if you wanted to pursue the traffic light theme a little further.

This schematic diagram should be all that a competent electrician needs to wire up your RV.
The Power switch as shown has 3 poles, but more are required for other functions such as :-
Switching Neutral as well as Phase connections.
Creating an N-E link for an Inverter with a "floating" output.
Supplying heavy current equipment (such as electric hot water cylinders) with Mains power only.
 #97166  by NeilV
 Mon Jul 27, 2015 11:57 pm
It just keeps getting better and better :)

Thanks again!

In my case (24v house/starter and alternator) would there be any downside to paralleling the 2 battery banks (thus both charged by alternator) and then ALSO running the inverter/smart charger to 'boost' the charge voltages (although in this case to both due to parallel??)

Just thinking out, this would "use the batteries to charge themselves" but since it's not a closed loop (alternator charging too) it would (sort of) work like an mmpt controller??
 #97175  by Neddy
 Tue Jul 28, 2015 9:07 am
Neil, the simplest, cheapest option for you is to parallel up your House and Starter batteries whenever the engine is running. Manual changeover switches cost roughly $40 - $70.
Engine charging of the House battery is restricted to a relatively low rate.

A better option would be to use a Voltage Sensitive Relay to make the switching completely automatic.
A VSR costs about $100. Engine charging of the House battery is restricted to a relatively low rate.

I am unclear as to exactly what you are looking for, but if you want a super-simple system offering maximum bang for minimum bucks, a really good option is to use a VSR to switch an Inverter coupled to a Charger connected to your House battery.
Neil, you already have this gear, so for you, the cost remains at just $100.
You get maximum charging for your House battery whenever the engine is running, completely automatically.

It's time for you to stop thinking of more alternatives and variations. Make a decision and start doing.
Enough suggestions already!

 #97182  by NeilV
 Tue Jul 28, 2015 1:29 pm
Neddy wrote: It's time for you to stop thinking of more alternatives and variations. Make a decision and start doing.
Enough suggestions already!

:oops: Hehehe, sorry... I do think too much!

will probably do the Dual switching suggested by your picture instead VSR as BEP switches are only $35 and give better options for using the inverter for more than just charging when parked up without 'shore' power... sorry for 'overanalysing' this!
 #97709  by Neddy
 Tue Aug 04, 2015 3:25 pm
From Neil's "Hard to imagine how much it takes" thread :-
"I added a switch between the batteries (paralleled starter and house) to initially utilise the alternator output..."
Neil, this is quite likely to be counter-productive. Consider these facts :-
(1) Given your 500 watts of solar power, your House battery will normally be at a fairly high state of charge.
(2) Your Starter battery will normally be at around perhaps 70% charged.
(3) Your alternator charge voltage is likely to be relatively low, maybe around 27 volts or even less.
(4) Your solar controller voltage will be much higher than that - 29.4 volts perhaps?
So, let's look at what happens when you put these two very different batteries in parallel.
A heavy current will flow from the House battery to the Start battery as they are forced to the same voltage, maybe around 28.2 volts. This means that, far from utilising the alternator, you will be taking load OFF it as your House battery discharges into your Starter battery.
This is pretty much the exact opposite of what you want. Your Starter battery is getting extra charge it doesn't want and doesn't need, while your House battery is being needlessly and pointlessly depleted.

"......... without the charger losses.."

Such losses are insignificant - and the House battery would of course be charging - not discharging!

".... if needed on shorter trips".
It is on shorter trips that House battery losses would be maximised. Leave the two batteries in parallel for long enough and they will eventually equalise and House battery losses will taper off. At this point there will be zero alternator input and your solar panels will (quite needlessly) be struggling to charge both batteries. Solar panel input into your House battery would be halved, therefore, and it would take double the usual time to fully charge your House battery.

"....and allow both banks to charge from the one charger when plugged to 240v like at present."
Exactly the same issues apply. "Dual Output" chargers are made so that batteries at different states of charge can be on different charge regimes. Neil, you have got a dual output charger - why not use it?

To sum up, if your House battery is less than maybe 60% charged you will gain something from paralleling it with the Starter battery when motoring. If your House battery is about 70% charged, you will gain nothing. If your House battery is better than perhaps 75% charged, paralleling it with the Starter battery will result in a net loss to the House battery.

 #97711  by NeilV
 Tue Aug 04, 2015 3:46 pm
Okay.... So don't use it quite like that once I have solar then :D

I'm still thinking that parallel charging the 2 sets FROM the solar - like when I'm in my new house and the vans parked up for the school term (teacher) would be a good idea? I do have the dual charger, but thought that I would still need to follow your maximised charging regime as suggested before the solar commitment.

Should my new plan just be to leave the house ones to solar charging, and the starter ones to alternator charging, except when 'parked up' out of use when perhaps parallel charging them from solar?

The only disadvantage I see there is that they might equalise with the worse battery, probably the start set, and thus degrade my AGMs...[thinking this out as I type]

So maybe leave them totally separate unless some critical event requires one to bail out the other, and use the smart charger to maintain starters, and solar to maintain house when in bus is in 'storage' conditions?
 #97765  by Neddy
 Wed Aug 05, 2015 9:55 am
"Maybe leave House and Starters totally separate unless some critical event requires one to bail out the other?"
YES! That's it in a nutshell. Your bottom-line emergency backup system is your parallel switch.
Really good to have - but never used in normal practice.

"..... and use solar to maintain House when in bus is in 'storage' conditions?


"..... and use the smart charger to maintain starters".
If need be. How old are your Starters? Are you having a problem with them not retaining their charge?

Viewing Starter charging as a separate issue, you have many options, including :-
(1) Do nothing. Your Starters should retain their engine-starting ability for many months.
(2) If indicated, buy new Starters that will keep their charge.
(3) Charge the Starters periodically with your mains powered charger.
(4) Charge the Starters periodically with your Solar setup. (2-way switch. Solar to House OR Starters.)
(5) Parallel your House and Starter batteries when leaving the vehicle for any length of time. Solar will maintain both. Sort of.
(6) Use parallel solar charging, but with the Starters set to a lower voltage. (Very easily done by adding a diode).
(7) Add a small solar panel dedicated to trickle-charging the Starters.

Each of these options has its own pros and cons, strengths and weaknesses.
I like #1 or #2. Your Starter batteries should not be a source of worry.
With your emergency parallel switch, they needn't be.

 #97766  by NeilV
 Wed Aug 05, 2015 10:45 am
Starters are good, less than a year old, and the only reason for recharging them is I have left several of the original long incandescent/fluorescent (mixed) lights in place, as they will provide both 'running' lights and better lighting options when parked (if needed)

Guess I can work that on a case by case basis...

Thanks again for clearing up all my inaccurate understandings, especially as I didn't update my ideas with the small 'excess' of solar I might soon have (in Summer anyway) :oops:
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