Automatic solar/alternator circuit I designed

[Not That Bob]

I want to dip my toe in Solar.

The plan is to have an separate alternator for the house battery, as well a small solar panel ( batteryMINDder  scc-105) to mainly maintain the battery via solar.

Please keep in mind, I have no electrical training so be kind on my diagram ( first hand drawn then, MS paint).

Look it over and tell me if you see any major flaws in my design.

The white lines are ignition off.
With ignition off, power flows from solar-panel/controller to the battery threw the relay using the normally closed terminal (87A I believe).
The alternator is  disconnected via the solenoid since it is not getting any voltage from ignition.

The red lines are when ignition is on.
The signal wire from the ignition trips the relay (now feeding 87 terminal) so the battery is now disconnected from solar.
The signal wire also trips the solenoid which allows the alternator to charge the battery while driving.

Will having nowhere for the solar output to go hurt the panel/controller?

I could wire a small fan or something to draw some power if needed to keep the solar side safe?

Thanks Bob (Not That Bob)

 

[29chico]

I want to dip my toe in Solar.

The plan is to have an separate alternator for the house battery, as well a small solar panel ( batteryMINDder  scc-105) to mainly maintain the battery via solar.

Please keep in mind, I have no electrical training so be kind on my diagram ( first hand drawn then, MS paint).

Look it over and tell me if you see any major flaws in my design.

The white lines are ignition off.
With ignition off, power flows from solar-panel/controller to the battery threw the relay using the normally closed terminal (87A I believe).
The alternator is  disconnected via the solenoid since it is not getting any voltage from ignition.

The red lines are when ignition is on.
The signal wire from the ignition trips the relay (now feeding 87 terminal) so the battery is now disconnected from solar.
The signal wire also trips the solenoid which allows the alternator to charge the battery while driving.

Will having nowhere for the solar output to go hurt the panel/controller?

I could wire a small fan or something to draw some power if needed to keep the solar side safe?

Thanks Bob (Not That Bob)

No need/not a good idea to disconnect the solar charge controller.   So no need for the 5 pole relay.

You will need a fuse at the battery positive terminal to protect the wires.  The fuse should be no farther than 7" from the pos post, the closer the better.  Make sure to run fat wires in the charging circuit.  The solenoid control wiring can be smaller.

I'd suggest the scc-180 charge controller from batteryminder and at least a 100w panel.  Just be sure to never connect that charge control to a lithium battery later as the desulfation action is not compatible with lithium cells.

Bob (that Bob) and James just posted a video about using a continuous duty solenoid.  My only only concern about that video is that they seem to be using a no name & probably China made solenoid.  Those cheap solenoids sell for around $13 on Amazon and the the Cole-Hersey made in USA versions go for about $7 more.

Video link:

 

[highdesertranger]

x2 on what Chico said. never disconnect your charge controller from the battery. in fact when you first hook everything up, you hook the charge controller to the battery first then hook up the solar panel. I run mine combined all the time no need to break the circuit except with the dual battery solenoid. also the advice about the Cole Hersee solenoid is spot on. highdesertranger

 

[Not That Bob]

No need/not a good idea to disconnect the solar charge controller.   So no need for the 5 pole relay.

I was worried about feedback/backfeed from the alternator effecting the controller.  Most diagrams I found online have something between the alternator/battery/controller. Still worried that alternator charging may confuse/damage controller?

You will need a fuse at the battery positive terminal to protect the wires.  The fuse should be no farther than 7" from the pos post, the closer the better.  Make sure to run fat wires in the charging circuit.  The solenoid control wiring can be smaller.

Not to worry, I have wired race cars from scratch so wiring size, fuses, grounds are not an issue.

I'd suggest the scc-180 charge controller from batteryminder and at least a 100w panel.  Just be sure to never connect that charge control to a lithium battery later as the desulfation action is not compatible with lithium cells.

I have a self imposed limit of around $150 on panel/controller.

Bob (that Bob) and James just posted a video about using a continuous duty solenoid.  My only only concern about that video is that they seem to be using a no name & probably China made solenoid.  Those cheap solenoids sell for around $13 on Amazon and the the Cole-Hersey made in USA versions go for about $7 more.

I will/do only use quality components ,thanks for the heads up.

Thanks Bob

 

[NeedAnEscape]

If you are using a second alternator to charge the house batteries, and are not connecting it to the starting battery and main alternator, you do not need a solenoid to disconnect the second alternator from the house batteries.

 

[ViaVacavi]

I agree with these guys. I have a solar charge controller, battery isolator and a 12v converter for shore power charging all connected to the house battery in parallel with no switching of any kind between the three. You really shouldn't have to worry about it. All three charging modes can work simultaneously on my build with no issues at all

 

[ViaVacavi]

If you are using a second alternator to charge the house batteries, and are not connecting it to the starting battery and main alternator, you do not need a solenoid to disconnect the second alternator from the house batteries.

I would like to add to this just for the sake of conversation  and thought.
Why use a 2nd alternator?  Why not just add an isolator?  In either case, you're adding one component. The difference is that continuous  duty solenoids are much cheaper, readily available, easier to replace , less likely to fail, won't add extra parasitic drag, take up less space, add less weight and require no modification to engine belt routing.  You also lose the ability to tie the start and house batteries together, which is an added bonus jump  start system if your start battery dies.

 

[Optimistic Paranoid]

Boats often use two alternators, and, more importantly, two voltage regulators.

With only one alternator, the computer or voltage regulator has to monitor the engine battery and cut back the output as necessary to prevent overcharging and damaging it.  This also cuts way back on the amount of current available to the house batteries.

With a separate alternator and voltage regulator on the house batteries, lots and lots of current can go to the house batteries even as the engine charging system cuts way back.

Moreover, the voltage regulator available through marine suppliers often has adjustable set points and the ability to do bulk, absorption, and float stages just like the better battery chargers.

 

[highdesertranger]

x2 on what OP said. highdesertranger

 

[SternWake]

No reason to disable any charging source. They can all work together when battery is low. When max. Voltage reached on one source, it drops out. Others continue.

My solar been assisting my alternator for 9 years.

Ive bypassed vehicles.voltage regulator and wired up adjustable external regulator. Potentiometer on dashboard next to voltmeter. If i dial voltage above solar setpoints, Solar drops out. Below, they work together.

I basically keep it at 14.4. Lowered only when i know battery is full.

Balmar voltage regulator s are great, programmable, expensive, ideal. And overkill for most wheeled vehicles.

Most vehicles vr are bipolar and far from ideal for depleted house batteries.

thick copper helps stabilize bipolar swings. Somewhat, but great ly helps reduce charge times to 80% charged

 

[Not That Bob]

Nothing personal to anyone but I like multiple responses and everyone seems to be in agreement, no cut-out needed. Got it!

Damn I thought I created a neat circuit, oh well.

Anyway, besides the benefits OP posted, I want to keep separate systems and like redundancy.

On the engine there is a unused bracket for the air pump where the alternator can go.

If my engine alternator fails, a few minutes with a wrench and I can be on my way. 

Thanks everyone.

 

[Optimistic Paranoid]

I don't know what year vehicle you are talking about, but at some point, they stopped using voltage regulators and the Engine Control Computer took over regulating the alternator as one of it's many functions.

I doubt if you are going to be able to find a voltage regulator that would work with one of these computer controlled alternators if you use one as your second alternator, and if you use one of the old style non-computer alternators as your second alternator, you won't be able to substitute it for your primary alternator if it fails.

I think.

 

[SternWake]

If one can easily add an alternator and dedicate it to house batteries. Thats pretty much ideal.

Get an alternator that requires external voltage regulation so yu can fine tune.

My ecm originally house my voltage regulator. A 10 ohm 50 watt resistor inline on original harness keeps check engine light off.

If i allow too much time over 14.7 v. The check engine light comes on. Goes out next engine start. But code is stored. Mpg tanks..open loop. Reset ecm all returns to normal

 

[Not That Bob]

No computer, old school 85 S10 with 350 swap running a Holley carby.
Alternator should be fine.

I started a build thread here: https://vanlivingforum.com/Thread-Slow-S10-build