Basic Solar Wiring - 1 2 Both Switch

[Uncle Bob]

Originally Posted by oivivio

Thank you Chris for the great feedback!

That is a good call Capt.Don. I left the panel disconnected before I left the boat as to keep solar power from coming into the system. How should I go about wiring directly to the batteries when a 1 2 Both switch is involved? Seems if I wire the charge controller to battery 1, I would get the following scenarios:

1 2 Both switch in the '1' position = Battery 1 to be charged
1 2 Both switch in the 'Both' position = Battery 1 & 2 to be charged
1 2 Both switch in the '2' position = Nothing charges? Could this be damaging to the controller?

How should I wire to ensure both batteries charge regardless of the 1 2 Both switch position? (I believe this would require an automatic charge relay?)

Thanks for all the help!

Simple, morning star sun saver duo controler. Charges two batteries independently and is smart enough to apply all available current to one battery if the other is full.
Also don't connect to the 1 2 both switch, connect to the battery with a suitable fuse at the battery.

[GILow]

Originally Posted by Uncle Bob

Simple, morning star sun saver duo controler. Charges two batteries independently and is smart enough to apply all available current to one battery if the other is full.
Also don't connect to the 1 2 both switch, connect to the battery with a suitable fuse at the battery.

+1 to this.

You have a controller already, so check if it has a secondary circuit for a starter battery. Our Votronic had one, I didn't know this when I bought it, only noticed it in the documentation included in the box.

Of course our engine battery bank is 24 volts so the circuit is no bloody help at all.. but nice to know I can charge the engine batteries one at a time if desperate.

[mitiempo]

Originally Posted by Uncle Bob

Simple, morning star sun saver duo controler. Charges two batteries independently and is smart enough to apply all available current to one battery if the other is full.

The Morningstar Sun Saver Duo is a PWM controller with minimal adjustment options. He already has an excellent quality MPPT controller with the added benefit of full adjustment of everything from absorption and float voltages to equalization and temperature adjustments.

His best option is to buy and install an ACR which will take care of the start battery automatically. All charge sources should be wired directly to the house bank.

Another option is to install a battery to battery charger (Xantrex Echo Charge) between the banks with again all charge sources wired directly to the house bank.

[ramblinrod]

Originally Posted by skipmac

One or two suggestions for the "easiest" but not necessarily the best option.

If one does not have an ACR (auto charge relay) the alternator should be connected directly to the start battery. This prevents accidentally disconnecting the alternator and damaging the alternator regulator. It is also considered the fail safe condition. Without human intervention the start battery will be charged by the alternator. The thought being that a dead start battery is less safe than a dead house battery.

When an ACR is used, the alternator charges the house bank, and the start battery is charged via the ACR without human intervention.

Beware that ACRs wreak havoc with coulomb counter type battery monitors, that aren't aware that various batteries are being switched in and out, especially with small house banks and light loads.

[skipmac]

Originally Posted by ramblinrod

If one does not have an ACR (auto charge relay) the alternator should be connected directly to the start battery. This prevents accidentally disconnecting the alternator and damaging the alternator regulator. It is also considered the fail safe condition. Without human intervention the start battery will be charged by the alternator. The thought being that a dead start battery is less safe than a dead house battery.

My opinion (for what that's worth) but also that of several boating experts whose opinions I highly respect like Maine Sail aka Compass Marine, the simplest, best, safest and most bulletproof option is to connect ALL charging sources directly to the house batteries. Several reasons.

1. The house batteries are by far the ones that need charging. Starting uses a tiny fraction of the amp hour capacity from the start batteries.

2. The alternator will always be connected to a battery so will avoid any risk of accidentally disconnecting and damaging the alternator with or without an ACR.

3. Install one of the several, very reliable and simple auto battery connectors which can be ACR, VCR, Echo Charge, Combiner, etc. This gives automatic, no user intervention, fail safe charge to the start battery so it will always be charged with zero risk of someone (like a tired captain, "helpful" guest, curious child) putting the 1/2/Both switch in the wrong position leaving the start battery dead.

4. The various types of automatic combiners are not expensive, $90-$125 if I recall, are reliable and easy to install.

Originally Posted by ramblinrod

Beware that ACRs wreak havoc with coulomb counter type battery monitors, that aren't aware that various batteries are being switched in and out, especially with small house banks and light loads.

My battery monitor and batteries are wired so all current in or out is counted by the monitor so net amps in or out are constantly and correctly shown. The monitor only counts amps IN/OUT for the house batteries but shows voltage for the start battery which is all that's needed.

[foufou]

The instructions I got with my charge controller said to connect controller output to batteries without going through the 1/2 both switch. But isolate each battery by putting a diode in series to each battery. This is to prevent one battery from discharging the other. It made sense at the time and has worked flawlessly. These are only trickle charge sized panels, about 1 amp. Does this make sense?

[skipmac]

Originally Posted by foufou

The instructions I got with my charge controller said to connect controller output to batteries without going through the 1/2 both switch. But isolate each battery by putting a diode in series to each battery. This is to prevent one battery from discharging the other. It made sense at the time and has worked flawlessly. These are only trickle charge sized panels, about 1 amp. Does this make sense?

Does that mean a diode in the line between the charge controller output and the battery terminal? If that is what they mean by in series then depending on what kind of diode that could reduce the charge voltage to the battery by as much as 0.7V. That may not sound like a lot but in charging it is significant.

[lonesoldier0408]

So, a large enough diode between the 1, 2, both switch and the start battery, would prevent battery flow from start battery to house bank? I know batteries tend to equalize, when connected. 🤔

[skipmac]

Originally Posted by lonesoldier0408

So, a large enough diode between the 1, 2, both switch and the start battery, would prevent battery flow from start battery to house bank? I know batteries tend to equalize, when connected. 🤔

If you place a diode between the start battery and the switch then if the diode is oriented correctly it will allow current to flow to the start battery but not from the start battery back to the switch.

BUT, the voltage at the start battery would be 0.7V lower and reduce the charging to the battery.

It would need to be a large, power rated diode if you ever planned to use the house bank as a backup to start the engine.

[Maine Sail]

Originally Posted by ramblinrod

Beware that ACRs wreak havoc with coulomb counter type battery monitors, that aren't aware that various batteries are being switched in and out, especially with small house banks and light loads.

Coulomb counters have many issues but this is not one of them. That is unless of course you wire the start battery to the shunt incorrectly, which I see regularly...

With a shunt based Ah counter the start battery is always wired to the load side of the shunt so that any energy taken by the start battery or fed by it to house is accounted for.. ACR's don't change the shunt wiring..

[Cadence]

Originally Posted by pesarsten

That is an excellent point capt.Don. , I installed a Morningstar sun saver that required the battery connection first, charge controller did not function if solar in power was present before battery voltage. Most battery switches disconnect when switched.

I am interested in the solution. I believe most here have reccomended wiring direct to house bank.

I would not swear to it but I believe those are wiper switches which make before break. Now going to off might cause a problem.

[SV Second Wind]

Wow. Thank you for all the great advice! So it sounds like the easiest/cheapest way may not be the best approach and a simple ACR would alleviate a lot of headache down the road.

When sizing ACRs, what should I consider? The total charging amperage running through the circuit? My solar controller has a 15amp max output, so I'm thinking I need to understand what the max amp output of the alternator is? I have a Yanmar 2GM20F. I believe it is the stock alternator. I searched online and it sounds like stock is 35 or 55 amp output. If it is a 55 amp alternator + 15 amp solar controller = 70amps. I'm assuming the following be too small?

65 Amp BlueSea m-ACR
https://www.bluesea.com/products/760..._12_24V_DC_65A

Maybe this would be a better choice?
120 Amp BlueSea ACR
https://www.bluesea.com/products/761...4V_DC_120A/FAQ

Thanks!

Brad

[skipmac]

Hi Brad,

If there's a chance you might install a larger alternator in the future go for the larger unit.

Here's another option.

Combiner 100 Sheet

[JimsCAL]

Originally Posted by oivivio

Wow. Thank you for all the great advice! So it sounds like the easiest/cheapest way may not be the best approach and a simple ACR would alleviate a lot of headache down the road.

When sizing ACRs, what should I consider? The total charging amperage running through the circuit? My solar controller has a 15amp max output, so I'm thinking I need to understand what the max amp output of the alternator is? I have a Yanmar 2GM20F. I believe it is the stock alternator. I searched online and it sounds like stock is 35 or 55 amp output. If it is a 55 amp alternator + 15 amp solar controller = 70amps. I'm assuming the following be too small?

65 Amp BlueSea m-ACR
https://www.bluesea.com/products/760..._12_24V_DC_65A

Maybe this would be a better choice?
120 Amp BlueSea ACR
https://www.bluesea.com/products/761...4V_DC_120A/FAQ

Thanks!

Brad

I installed the smaller one on my 3GM30F with stock alternator and 20 watt panel with PWM controller for keeping the batteries topped off while on the mooring. No issues in three years of use. I have no plans to upgrade the alternator, but may add a little solar capacity.

[SV Second Wind]

Good call skipmac. If I end up increasing my house bank capacity, I should probably consider increasing the alternator.

Thank you for all the advice! I'm ready to get this thing wired up correctly and keeping those batteries topped up.

Cheers!

Brad


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