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sailman

Solar Charging tie in

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How do you tie in solar charging into the existing charging system? Currently I have a mastervolt battery charger, engine alternator. The batteries (house, starter and windlass) are tied together with a xantrex battery monitor to regulate which battery gets priority and then topping off all batteries evenly.

 

I want to increase my house bank capacity and add solar charging. My concern is the tie in? Do I have to have the solar regulator on a separate switch so that it can not be active if on of the two other chargers (shore power or alternator) is active? Would a different battery monitor handle this?

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I can try to explain ...

 

All charging sources can go to the batteries directly. All your sources (alternator, shore-power and solar) will have regulators or smart-charge logic to ensure you don't cook your batteries. I think from your description, you have an "Echo-Charge" or similar, which will allow your house batteries to trickle charge to your starter battery when a charge voltage is seen in your house bank. I leave my boat plugged in when I leave, but the solar panels are also charging. I have had no issues with this set-up.

 

As for your battery monitor, most I have seen have a shunt on the negative battery terminal that measures current. As long as you maintain your connections so that your charge source has the negative connection on this shunt, you will be able to see the charge activity from your solar panels.

 

Hope this helps.

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Thanks for the reply. That makes sense. So your solar charger is run right to the batteries with the negative connection on the shunt?

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Yes. Only clarification is that the panel is wired directly to the regulator, then from the regulator the +ve goes straight to the battery and the -ve lead goes to the shunt.

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Keep in mind that you will want a fuse in the + lead to the battery bank as close to the battery as possible. The neg lead from the controller goes to the loads side of the shunt or will not be captured/seen by the battery monitor. The only wire on the battery side of a shunt should be the neg battery jumper wire to the shunt.... Every other negative wire on the boat, including a start or AUX battery, goes on the loads side of the shunt or your battery monitor will never work correctly...

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You can do that, but there isn't much advantage unless you plan to turn off the solar (and why do that?). A fixed fuse is cheaper and easier.

 

I use a Bluesea ST fuse block for my unswitched loads: solar, bilge pump, unswitched power on stereo, unswitched power on Webasto heater. Makes it really easy to add a fuse to these circuits and label them without having the expense/panel space usage on my circuit panel. I also like knowing that I just need to turn all 12V switches to OFF when leaving the boat.

 

alex

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Is it ok to wire the positive lead from the solar panel to a circuit breaker on the electrical panel?

Are you going to leave your DC system on, including the battery switch, when you're not there..?? Do you really want all those extra connections and potential for voltage drop in your solar path..? Direct to the battery bank or its bus, with proper fusing, is the preferred approach...

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Is it ok to wire the positive lead from the solar panel to a circuit breaker on the electrical panel?

Are you going to leave your DC system on, including the battery switch, when you're not there..?? Do you really want all those extra connections and potential for voltage drop in your solar path..? Direct to the battery bank or its bus, with proper fusing, is the preferred approach...

 

I dare say if you are worried about voltage drop from a solar charging current from your DC panel to your batteries you might reassess your priorities...

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Solar panels should be shorted out when not in a charging circuit. It's not as critical with a small array, but larger arrays can have a few hundred volts output. Don't put a switch on the positive lead. It can cause surges from the array that may damage downstream equipment. If you want to shut down a panel, cover it with something that will block the sun. We used cardboard sheets during our install. Oh, blocking 10% of a panel reduces output by 90%.

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Is it ok to wire the positive lead from the solar panel to a circuit breaker on the electrical panel?

Are you going to leave your DC system on, including the battery switch, when you're not there..?? Do you really want all those extra connections and potential for voltage drop in your solar path..? Direct to the battery bank or its bus, with proper fusing, is the preferred approach...

 

I dare say if you are worried about voltage drop from a solar charging current from your DC panel to your batteries you might reassess your priorities...

 

 

By all means then go ahead and wire it with some 22 GA wire.... :rolleyes:;)

 

I say this because many boat builders already grossly undersized the wire feeding the DC panel. Does he have an array capable of 50A or 3A? We don't know.. There are plenty of boats out there who can't even meet max 3% voltage drop for nav-lights due to undersized DC panel wiring........

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For my system, there is one Group 27 battery, one 30A circuit breaker close to the battery, then a panel with 8 circuit breakers. The wiring has all been selected to be at least as large as recommended when using the 3% voltage drop tables for marine wiring. The battery circuit breaker is usually on. When I leave the boat, I turn off the autopilot, VHF, lights if they were on, and the GPS chartplotter if it was on. The circuit breaker to the solar panel is left on.

 

It seems that if I disconnected the solar panel from the circuit breaker and instead connected it to a fuse then directly to the battery, there would be three fewer connections, but the connections that would be eliminated are all larger wire connections between the battery and the panel. Existing includes regulator wire to panel, main panel feed to panel, both sides of 30A circuit breaker, then battery for five connections between the regulator and the battery. A direct wired system would have regulator wire to fuse, fuse to battery for two connections between the regulator and the battery.

 

The panel is 10 Watt, and there is a charge controller between the panel and the circuit breaker.

 

The maximum voltage with the charge controller is 14.1.

 

Maine Sail- The "HowTo" Articles in your LINK are some of the best content anywhere for sailboat related mechanical topics. I have read some of them several times and referred others to them, as well. Thank you for making those.

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Project update:

 

100W Renogy Solar panel is installed. I bought four Suncor Rail fittings 756057.jpg and made slits in the bimini to allow the top to poke through. I then bought some 1/4" aluminum bar stock and made four ells and drilled them out to accept a 1/4-20 bolt. These were then mounted to the panel and the panel then screwed to the bimini. I can remove the panel in about fifteen minutes if needed and the charging wire have waterproof plugs that are easily accessed. The wires were run along the bimini frame to an entry in the cockpit coaming and then run to the Solar Controller. So far it is working like a charm. I have been thinking about getting a small LED amp meter and mounting it to see how much energy is being pushed into the batteries, the controller has a load connection which would power the meter.

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