Relay to disable solar when engine running

[hlev00]

I want to disable my solar when my engine is running to avoid the solar voltage targets from conflicting with the alternator targets. If both are running the solar seems to confuse the Balmar gear. If I am running the engine, the alternator (Balmar 100A + ARS-5 regulator) can supply plenty of charging current compared to my solar (2X 190W banks each with a Victron 75/15 MPPT controller). Some suggestions are to set the solar target voltages below the engine alternator targets but then the solar never gets the batteries (Trojan T125) to their proper voltages.

So I am thinking of using two relays (one for each solar bank) so that when the engine is running the solar is disabled, but as soon as I shut down the engine, the solar will do what it can. I would use the relay to disrupt the current coming from the panels to the MPPT controllers. Automotive relays are designed around 12V @ 40A (480W) which is a lot more than either solar bank can supply. Is it okay if the solar voltages are higher as long as the total Watts are less than 480W?

Thanks,
Harry

[nwdiver]

Run your solar to your hot water tank, use the juice……

[Seman]

yes, your 40A 12V relay will do the job The 12V is the relay operating voltage, not the contact switching voltage. switching voltage most likely rated at 250V.

[smac999]

Leave them both on.

What problems are you having? They should be fine together.

[more]

Originally Posted by hlev00

I want to disable my solar when my engine is running to avoid the solar voltage targets from conflicting with the alternator targets. If both are running the solar seems to confuse the Balmar gear. If I am running the engine, the alternator (Balmar 100A + ARS-5 regulator) can supply plenty of charging current compared to my solar (2X 190W banks each with a Victron 75/15 MPPT controller). Some suggestions are to set the solar target voltages below the engine alternator targets but then the solar never gets the batteries (Trojan T125) to their proper voltages.

So I am thinking of using two relays (one for each solar bank) so that when the engine is running the solar is disabled, but as soon as I shut down the engine, the solar will do what it can. I would use the relay to disrupt the current coming from the panels to the MPPT controllers. Automotive relays are designed around 12V @ 40A (480W) which is a lot more than either solar bank can supply. Is it okay if the solar voltages are higher as long as the total Watts are less than 480W?

Thanks,
Harry

what are you talking? what theoretical possible conflict.

[lmxr]

Originally Posted by hlev00

[...]Is it okay if the solar voltages are higher as long as the total Watts are less than 480W?

In case of mechanical relays, the higher voltage will cause more sparking than designed and as such will cause the relay to wear out far faster. In case of solid-state relays, it is not unlikely that it will short out.

Have you considered doing something with the VE.Direct communication port on the Victron MPPTs? Victron has cables that allow to switch them on and off easily.

[noelex 77]

Originally Posted by hlev00

If both are running the solar seems to confuse the Balmar gear.

In what way?

Forget the relays. You are creating extra work and potential failure points.

If you can describe the conflict you are experiencing there is likely some simple solution. Modern solar and alternator controllers have multiple user adjustable parameters. Charging conflicts are rare but these can usually easily fixed if they do occur.

[HeywoodJ]

Originally Posted by noelex 77

In what way?

Forget the relays. You are creating extra work and potential failure points.

If you can describe the conflict you are experiencing there is likely some simple solution. Modern solar and alternator controllers have multiple user adjustable parameters. Charging conflicts are rare but these can usually easily fixed if they do occur.

+1

If the alternators are not putting out much current because the solar is already reaching the maximum voltage then the batteries are full anyway and don't need a ton of current from the alternator. Once you reach your target voltage all sources should adjust output to keep it there.

One thing that can appear to cause issues is a difference in the voltage measurement. If, for instance, you have all sources set to 14.4V for bulk charge, and the solar is measuring that as 14.4 while the alternator is measuring that as 14.5 then the alternator will drop out before you want it to. In that case you need to dig into why they are measuring differently and possibly adjust setpoints to account for measurement inaccuracies.

[hlev00]

I understood that as long as both are monitoring the voltages that it doesn’t matter if they are both charging at the same time. What I noticed the other day though was with solar and alternator charging, the amps going into the battery were less than the alternator alone. I will repeat the experiment again.

I definitely have measurement point issues. The ARS-5 only measures at the alternator and there is voltage drop between that and the batteries. I was thinking a couple of relays would help in the short run but it may just keep me from fixing the basics first.

[PaulCrawhorn]

If the bank is not reasonably depleted, it will only accept a low current no matter how much is available.

Even with infinite current available your bank takes over seven hours to get from 50% to 100% full.

More than five hours of that will be at lowered current maybe from 85% to 100%.

And four hours of that might be from 95% to 100%.

The exact pattern depends on many factors, but the point is you must get the battery depleted in order to say anything much about the current level it is able to draw.

[Wotname]

Originally Posted by hlev00

......... I would use the relay to disrupt the current coming from the panels to the MPPT controllers. Automotive relays are designed around 12V @ 40A (480W) which is a lot more than either solar bank can supply. ...........

Thanks,
Harry

Be cautious about disconnecting solar panel under load e.g. using a relay to open the circuit. The panels I'm familiar with specifically warn against this practice.

[HeywoodJ]

Well, if for some reason you want to go down the road of turning off the solar, Victron offers a remote on/off cable that may be suitable (depending on your exact system configuration) that may be a viable option. If you wired that through a relay connected to the ignition switch (probably the NC contacts). That would probably be a better solution than interrupting the solar charge current (although it may be more costly as relays are cheap), but that way you could just "tell" the solar to turn off (and back on) automatically.

Still, I suspect the problem is with your voltage drop and local voltage monitoring at the ARS-5. Not much you can do about that, as the current drops the voltage drop will be less and thus setting the voltage values high on the ARS-5 to compensate will lead to overcharge when run for long periods.

[dkenny64]

I agree with others.. leave them both on.

we went on a short trip, about a month. ended up motoring for hours at a time
800w into 2 house banks and the engine start via 3 controllers..(solar side).
no problems with over charging. using epever 40a controllers.. most mornings
the batteries were 12.4 or higher. most nights were at anchor.


another thought..most controllers don't like the disconnection from the battery before they are disconnected from the panels.



-dkenny64

[misssherry]

Originally Posted by hlev00

I understood that as long as both are monitoring the voltages that it doesn’t matter if they are both charging at the same time. What I noticed the other day though was with solar and alternator charging, the amps going into the battery were less than the alternator alone. I will repeat the experiment again.

I definitely have measurement point issues. The ARS-5 only measures at the alternator and there is voltage drop between that and the batteries. I was thinking a couple of relays would help in the short run but it may just keep me from fixing the basics first.

My ARS-5 has a remote sensing wire that attaches directly to the battery. If the sensing wire is not installed the regulator defaults to the alternator for sensing.

[Redline452]

Originally Posted by hlev00

I definitely have measurement point issues. The ARS-5 only measures at the alternator and there is voltage drop between that and the batteries.

For what it's worth, I recently tracked down a voltage drop on our house bank and discovered that the main battery switch was the cause - over half a volt at 10A. Not having been switched off in several years, it cleaned up after being cycled on-off several times. It was the T-handle type that turns 360 degrees, "on" horizontal and "off" when vertical. Did not see that coming. Exercised all the other switches and breakers as well.