How do Solar and Alternator play together

Fred Mc · July 26, 2018, 01:24:03 PM

I don't have a problem (YET) but after reading Neodaddy's problems I want to make sure I'm doing it right.

My bus was converted 30 years ago and had the typical converter for power when plugged into a power outlet.We either plugged into the pole or ran the house system off the bus start batteries. Recently I added solar panels and 2x 12v deep cycle batteries. The house power is now completely separate from the start system although I can connect the house and start systems for charging.(I haven't tried that yet as the solar keeps the batteries charged and I'm worried about a problem due to having 3 12v batteries for start and 2 12v deep cycle for house). I can also power the house system from the start batteries for power when traveling.
I also haven't tried having the solar charge system and the converter(power pole) connected (through the batteries) at the same time.
The charge controller from the solar puts out around 18Volts.

I'm not concerned about keeping the bus start battery system completely separate from the house system ( there is a battery disconnect switch for the start batteries that I turn off when camped) but I'm curious what would happen when the solar charge controller is putting 18V into the house batteries and the converter puts its voltage(whatever that may be) into the same batteries.(not curious enough to try it before getting advice though)

Regards

Fred

richard5933 · July 26, 2018, 01:28:44 PM

What I've read is that any secondary charging source which is turned on and connected to the bus system while the bus engine is running has the potential to confuse the bus alternator/regulator and cause a no-gen light to come on. Don't know all the details, but I've set up my system so that either the bus is charging things or the converter/solar is charging things, never both.

Fred Mc · July 26, 2018, 01:33:04 PM

Richard.
so then you don't try and charge both systems via a switch like some others do.

Regards

Fred

richard5933 · July 26, 2018, 02:20:29 PM

Charging both systems from one source through a switch/solenoid isn't the problem. On our 4106 we had a solenoid that allowed us to charge both house and bus batteries from the same source. While on the road it was the bus alternator. While parked and plugged in it was the converter/charger. If we had solar it could have been solar.

The problem comes when you try and do the opposite - charge the bus batteries from multiple sources. If you run a secondary charge into the bus batteries while the bus alternator is running, the regulator will see the incoming voltage from the secondary source and come to the (wrong) conclusion that there is no need to send through a charge from the alternator. Then you get a no-gen light. Then things get confusing.

The bus alternator is probably much more powerful than any other source coming in, be it solar or converter/charger. There is really on need to have those system connected to the bus batteries while the engine is spinning the alternator. Once the engine is shut down, then it's time to engage the other charging sources.

Iceni John · July 26, 2018, 03:01:19 PM

Cole-Hersee makes some nice 250A Schottky diodes that could be used to separate two different charging sources. I'm using two of them to separate my house battery banks so one cannot backfeed into the other, but they could be used for plenty of other purposes.

John

buswarrior · July 26, 2018, 03:34:21 PM

No free lunch.

Diodes make trouble of their own to charge quality/completeness.

All those "isolator" things are not on the true alternative energy peeps radars, except to shoot them...

Happy coaching!
Buswarrior

richard5933 · July 26, 2018, 03:57:27 PM

Quote from: Iceni John on July 26, 2018, 03:01:19 PM
Cole-Hersee makes some nice 250A Schottky diodes that could be used to separate two different charging sources. I'm using two of them to separate my house battery banks so one cannot backfeed into the other, but they could be used for plenty of other purposes.

John

You'd be trying to keep the bus batteries & regulator from seeing the charge coming in from the solar. If you put diodes in the circuit to prevent them from seeing the charge, you'd also be keeping the charge from actually getting to the batteries. The diodes would work if you're trying to connect two battery banks to a single charging source so that you can keep the battery banks from draining each other. In this case you're trying to feed one battery bank from multiple sources at the same time.

Since the alternator is more than capable of charging everything, I'm not sure there is really a reason to have the solar connected to the bus batteries at the same time as the alternator is running.

Perhaps it would be possible to use a relay to disconnect the solar from the bus batteries whenever there is current flowing from the alternator?

luvrbus · July 26, 2018, 04:02:08 PM

Quote from: buswarrior on July 26, 2018, 03:34:21 PM
No free lunch.

Diodes make trouble of their own to charge quality/completeness.

All those "isolator" things are not on the true alternative energy peeps radars, except to shoot them...

Happy coaching!
Buswarrior

Most contain 1 direction diodes to prevent feed back is all they are in 25 years I haven't had a problem with one, I don't care much for the cost though

Fred Mc · July 26, 2018, 04:15:28 PM

"Perhaps it would be possible to use a relay to disconnect the solar from the bus batteries whenever there is current flowing from the alternator?"

Or the KISS method-just flip a switch.

Lee Bradley · July 26, 2018, 05:19:57 PM

Other than the alternator light coming on and the tachometer not working, I have no problem with the solar shutting down the alternator. Just means the alternator is not adding a load to the engine; huge gain in MPG LOL. When the load on the system exceeds the solar output, the alternator picks up the additional load. That way the solar is used to its full capacity and the alternator is secondary source.