Solar Panel Wiring - to two batteries??

[Guest]

I am about to permenantly instal a small solar panel to help keep my batteries topped up when on a swinging mooring.

I had this panel on my previous baot and simply used large spring connectors to connect directly onto one of the batteries when leaviing the boat. Alternating it occasionally between the domestic supply and the starter battery.

I would like to acheive a more professional solution, but presume that if I want to wire to both batteries I would need a blocking diode or similar, to stop one battery simply discaheging into the other one. I guess though that the diode may reduce the small amount of current available from the panel so may not be a wise idea?

Any suggestions - I don't want or really need an additional panel.

Fair winds

Malcolm

 

[Strathglass]

You will require two diodes one in the feed to each battery. ALSO you MUST put an in-line fuse in each positive lead, as near each battery as possible. Otherwise the fire risk is severe
Iain Simpson

 

[Shanty]

Yes, you will need a blocking diode, or, as you say the charge will equalise between the two batteries. Use a Schottky diode, as these have about half the voltage drop of conventional diodes (from Maplins - about 9p each).

BTW - Your solar panel may already have a diode built in, to prevent the panel from discharging the battery during the hours of darkness, however this won't separate your two batteries.

 

[broadbent]

Is theft a serious problem?
And if so, how do you secure your panels?

 

[tomboy352]

If you dont want to use the power consuming diodes, you might try paralleling up the batteries ( battery switch to BOTH) or putting a remouvable link between the positive posts, and another between the neg. posts (if the dont already link via engine block) . 2.5m m multistrand should carry the small solar charging current. This link would need to be remouved or switched out when not in use . IMPORTANT Use inline fuses in all wires.

 

[jfkal]

I'd go for proper splitting diodes (which you should have anyway with 2 batteries).
Take out the panel internal diodes in order to get rif of their voltage drop. If the panel has more the 10 W you NEED a regulator otherwise the charge will boil away your battery water or damage your sealed or gel batteries

 

[vyv_cox]

I have a device called a Fox-I-90, which cost a bit more than 9p at Maplins. It preferentially charges the service batteries and diverts to the starter battery if its voltage falls below a certan level. It also has LEDs to show whether it is providing any input to the batteries and a current/voltage LCD display for each battery. This may now be an obsolete model, superseded by the 100. They have a website at http://www.sunware.de/DE/Produkte/Regler/FOX_X00.htm, text is in German but the pictures and tables are not. It costs 76 Euros.

 

[Guest]

Vyv

Many thanks for this link to a an valuable website. I did manage to find english pages on their products:

http://www.sunware.de/US/Products/regulators/FOX_X00.htm

Looks that is the way I will go

Malcolm

 

[Julian]

Using two diodes will effectively route charge current to the battery with the lowest terminal voltage untill they are equal.