Solar panel disconnect when Engine power switched on.

[Shaddickp]

I need some electrical advice. I installed solar panels to my boat which has an MD2030D Volvo penta engine. After installation the tacho stopped working when it was sunny. So I figured I must switch off the panels when the engine is switched on. Now I want to fit a relay into the +ve cable from the panels to automatically isolate the panels when the engine is switched on. I used a normally closed (NC) relay connecting solar +ve wire to pole 30 on relay, and pole 87 connected to my MPPT controller. All good so far I think. Then with reference to the engine control panel diagram, I connected the Red/Blue coming from the power on switch 9 that would normally connect to the start push button 10, to pole 86 of relay, and then pole 85 of relay back on to 10 where the old Red/Blue connected. All looked good when I powered on using switch 9, the solar panel was switched off, the preheat worked ok, all warning lights ok, but when I pushed the start button 10, nothing happened. Engine did not start, no starter or anything. So I reconnected the R/BL from 9 back to 10 and all fine.
So is the relay preventing enough current to go across 86-85 and thus stopping start button 10 from working? Should I use instead the R/BL going from engine power on button 9 to pole 5 on the the Alarm/ Glow rocker number 12, or will that just now mean the Glow switch will not be able to draw enough current? Or finally should I put it between 5 (on rocker 12) and the wiring harness loom (15) pole 3, again R/BL wire?
Apologies for the war and peace description.

 

[Tranona]

Why are you connecting the solar to the switch panel? It is more usually connected direct to the battery(s) you are keepi9ng charged.

 

[Boathook]

The solar panels should have there own mppt controller that is connected direct to the batteries via fuses.

 

[Shaddickp]

Because when the engine is started I want to effectively turn off the solar panels and let the alternator do the charging. So all I'm doing is putting a switch in the +ve cable from the panels to the MPPT controller, which breaks that connection when the engine control panel is powered on.

 

[Shaddickp]

The solar panels should have there own mppt controller that is connected direct to the batteries via fuses.

Yes that is my current setup, but because the solar voltage is higher than the alternator voltage then the alternator (which has a battery sensing wire) cuts out, hence the tacho stopping especially when sunny.

 

[rotrax]

Yes that is my current setup, but because the solar voltage is higher than the alternator voltage then the alternator (which has a battery sensing wire) cuts out, hence the tacho stopping especially when sunny.

Put a load on. My smart regulator stops my alternator charging when motoring on a sunny day with a big solar output. I just put the Nav lights on. My tach does not stop.

 

[Shaddickp]

Put a load on. My smart regulator stops my alternator charging when motoring on a sunny day with a big solar output. I just put the Nav lights on. My tach does not stop.

Thanks but that's not the solution I'm looking for. I've read in another thread about installing a NC relay, which seems a smart solution, but there wasn't enough detail about wiring up to my type of engine control panel. Thanks all the same.

 

[[70521]]

If you have your solar panels connected to an MPPT then the battery bank. When the engine is charging the battery bank the solar panels have a wee rest. No need to overcomplicate a simple format that works in boats across the known universe.

 

[Shaddickp]

If you have your solar panels connected to an MPPT then the battery bank. When the engine is charging the battery bank the solar panels have a wee rest. No need to overcomplicate a simple format that works in boats across the known universe.

Yes I would do that but because there is a battery sense wire connected to the bank I'm charging it 'sees' the higher voltage (but much smaller current) of the output from the MPPT and switches off the alternator (the regulator on the alternator is actually doing this I think). That is the issue I'm trying to overcome.

 

[Shaddickp]

Small correction - references to pole 87 on the relay should say 87a

 

[PaulRainbow]

I need some electrical advice. I installed solar panels to my boat which has an MD2030D Volvo penta engine. After installation the tacho stopped working when it was sunny. So I figured I must switch off the panels when the engine is switched on. Now I want to fit a relay into the +ve cable from the panels to automatically isolate the panels when the engine is switched on. I used a normally closed (NC) relay connecting solar +ve wire to pole 30 on relay, and pole 87 connected to my MPPT controller. All good so far I think. Then with reference to the engine control panel diagram, I connected the Red/Blue coming from the power on switch 9 that would normally connect to the start push button 10, to pole 86 of relay, and then pole 85 of relay back on to 10 where the old Red/Blue connected. All looked good when I powered on using switch 9, the solar panel was switched off, the preheat worked ok, all warning lights ok, but when I pushed the start button 10, nothing happened. Engine did not start, no starter or anything. So I reconnected the R/BL from 9 back to 10 and all fine.
So is the relay preventing enough current to go across 86-85 and thus stopping start button 10 from working? Should I use instead the R/BL going from engine power on button 9 to pole 5 on the the Alarm/ Glow rocker number 12, or will that just now mean the Glow switch will not be able to draw enough current? Or finally should I put it between 5 (on rocker 12) and the wiring harness loom (15) pole 3, again R/BL wire?
Apologies for the war and peace description.

Connect terminal 85 to negative and terminal 30 to the red/blue if you want the relay to open when you turn the power on or to (7) red/green if you want it to open when the engine is actually running.

 

[Shaddickp]

Thank you Paul I will do that. Thanks for taking the time to read my post and provide a solution

 

[Shaddickp]

Connect terminal 85 to negative and terminal 30 to the red/blue if you want the relay to open when you turn the power on or to (7) red/green if you want it to open when the engine is actually running.

Did you mean terminal 86 rather than 30, currently I've got the solar +ve on that?

 

[Alex_Blackwood]

Did you mean terminal 86 rather than 30, currently I've got the solar +ve on that?

I did wonder that? It was early in the morning

 

[Shaddickp]

Thanks Alex, that confirms my thinking.

 

[PaulRainbow]

Did you mean terminal 86 rather than 30, currently I've got the solar +ve on that?

Sorry, 85 and 86 are the coil terminals, so connect them to negative and the red/blue

30 and 87a for the solar connections.