Solar panel to batteries connection.

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Nicholas123

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My solar panel is wired strait to my starter battery from it's controller thing & though this battery seems to be nicely charged up my domestic battery is not so should I wire it to the main three way switch (choice of battery one battery two or both)?
The negative on the batteries has a link but not the positive so if I position the switch on the 'both' setting does the domestic battery already get a share from the solar panel :confused:
 
Croak said:
The only problem being when it is switched off.
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I know that means the alternator would be damaged when the engine is running but is there any way that my domestic battery can get a charge from the solar panel with the present arrangement?Sorry if I'm coming over as particularly thick with this question but electrics are certainly not my speciality.
 
I think its ok to use a diode splitter from your solar cell to gharge up each battery but preventing one discharging into the other. I have howerver a lingering doubt that if you were motoring at night that ppart of the the alternator output would go through the solar cell. Mmmmmmm more thought required!
 
Nicholas123 said:
My solar panel is wired strait to my starter battery from it's controller thing & though this battery seems to be nicely charged up my domestic battery is not so should I wire it to the main three way switch (choice of battery one battery two or both)?
The negative on the batteries has a link but not the positive so if I position the switch on the 'both' setting does the domestic battery already get a share from the solar panel :confused:
Click to expand...

Nicholas123 said:
I know that means the alternator would be damaged when the engine is running but is there any way that my domestic battery can get a charge from the solar panel with the present arrangement?Sorry if I'm coming over as particularly thick with this question but electrics are certainly not my speciality.
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SHUG said:
I think its ok to use a diode splitter from your solar cell to gharge up each battery but preventing one discharging into the other. I have howerver a lingering doubt that if you were motoring at night that ppart of the the alternator output would go through the solar cell. Mmmmmmm more thought required!
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Several solutions including

Leaving the battery switch set to both..... not the best solution because you then have all the electrics switched on and the batteries paralleled

Charge the domestic battery from the solar panel rather that the starter battery because the engine will keep that adequately charged .

Fit a solar regulator with two outputs.

Rewire the electrical system separating engine, charging and domestic systems using individual isolating switches ( and an emergency linking switch)
Arrange the charging to be via a VSR which if a "dual sensing" type will allow you to wire it so that the engine charges the starter battery as its first priority while the solar panel charges the domestic battery as its first priority.

A diode splitter added to the solar controller may not work as the controller may need a power supply from the battery which the diodes will prevent.
Even if it does work you will suffer from volts drop across the diode splitter leading to incomplete charging.

You seem to have some false impressions about what will cause damage to the alternator.
It is likely to be damaged if you disconnect both batteries, eg by switching the selector to"OFF", while the engine is running. If you change from one battery to the other while the engine is running always do so via the "BOTH" position
 
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VicS said:
Charge the domestic battery from the solar panel rather that the starter battery because the engine will keep that adequately charged .
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This is what I have. Only drain on starter battery is starting the engine, which then tops it up fairly quickly, so I can't see any reason to need to keep it under charge when not in use.
 
VicS said:
It is likely to be damaged if you disconnect both batteries, eg by switching the selector to"OFF", while the engine is running. If you change from one battery to the other while the engine is running always do so via the "BOTH" position
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That is my understanding & indeed what I do Vic.
I am at present conducting an experiment to see if my solar panel will charge up my domestic battery in the 'both' position.I would not have it in this position while the engine is running but would target individual batteries for charging from the alternator.
Changing the solar panel to the domestic battery is a good suggestion but I don't really like having any other odd bits of wire going directly to the batteries so am considering wiring them to the main battery switch or maybe to one of the many junction boxes that are scattered about.The whole electrical system is a series of add ons & is in a bloody mess.
 
If you wire it in to charge in the both position, the solar panel will not charge your battery when you put it in the off position when you leave your boat.
 
I have the dual battery bank solar panel controller, which connects directly to each battery bank. It preferentially charges the domestic bank, then the starter battery when the domestic is full. I normally start the engine on the domestic bank, position 2 on the 1-2-both switch, when the alternator charges the domestic bank and all of the panel's charge goes to the starter battery. At this time of the year both batteries are fully charged for much of the time, except overnight with the fridge permanently on, when the domestic voltage drops to about 12.3 by early morning. By 0900 it is measuring 13.0.
 
vyv_cox said:
I have the dual battery bank solar panel controller, which connects directly to each battery bank. It preferentially charges the domestic bank, then the starter battery when the domestic is full. I normally start the engine on the domestic bank, position 2 on the 1-2-both switch, when the alternator charges the domestic bank and all of the panel's charge goes to the starter battery. [/QUOT]

I must be tired, for this second sentence( second half ) confused me. :confused:
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VicS said:
Not even to isolate the batteries when leaving the boat ?
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No,I usually leave it on the battery I hope the solar panel will charge but I make sure all the main functions are turned off on the main switch panel & assume fuses will take care of any eventuality.
Thinking about it you don't turn off your house main electricity when you leave it do you.
 
Cardo said:
The mains electricity in your house doesn't generally run out if you leave something running!
Flattening batteries is likely to irrevocably damage them.
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That's true but I have been monitoring the situation & the dodgiest application I have come across so far was an automatic bilge pump which was wired directly to the batteries.I noticed a small 'leakage' indicated by current at the solar power controller thing & now by cutting out that bilge pump it has been fixed.
 
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Nicholas123 said:
That's true but I have been monitoring the situation & the dodgiest application I have come across so far was an automatic bilge pump which was wired directly to the batteries.I noticed a small 'leakage' indicated by current at the solar power controller thing & now by cutting out that bilge pump it has been fixed.
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The wiring of auto bilge pumps is an ongoing debate. Some say this should be wired direct to the batteries. If your boat develops a leak whilst you're away, you'd probably want your bilge pump to keep the water out. Better a flat battery than a sunken boat!
On the other hand, some bilge pumps (well, the switches in them) seem to use a sizeable (in the long term) amount of power checking to see if there is water about, so could potentially flatten a battery even if there's no water about.

If you have a solar panel keeping things topped up, it could be a good idea to have the bilge pump wired up direct, I guess.
 
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