solar panel wiring - help please

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peter2407

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I am trying to wire up an 80w solar panel through a regulator to the battery bank, which I thought would be a simple job, but doesnt appear to be. The panel has a +ve and -ve marked lead, the regulator has connectors that say: PV+, BAT+, V SET, COM (and there may be a " - ", but its a bit faded) and COM -. Can someone advise me on the wiring arrangements please? My preference would be to trickle charge but the engine start battery and the 2 domestic batteries, but if that is not possible/advisable, then the starter battery only. TIA.
 
peter2407 said:
I am trying to wire up an 80w solar panel through a regulator to the battery bank, which I thought would be a simple job, but doesnt appear to be. The panel has a +ve and -ve marked lead, the regulator has connectors that say: PV+, BAT+, V SET, COM (and there may be a " - ", but its a bit faded) and COM -. Can someone advise me on the wiring arrangements please? My preference would be to trickle charge but the engine start battery and the 2 domestic batteries, but if that is not possible/advisable, then the starter battery only. TIA.
Click to expand...

Make / type of regulator ???

Pictures ?? Someone might recognise it


Instructions on line ??????

Google is usually your friend.
 
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Vic - did the google thing but no luck. Its a SUN-PRO 1200NR by Petrillo Scientific Instruments. This is actually a temporary thing to test the panel as I have a digital version coming.
 
peter2407 said:
I am trying to wire up an 80w solar panel through a regulator to the battery bank, which I thought would be a simple job, but doesnt appear to be. The panel has a +ve and -ve marked lead, the regulator has connectors that say: PV+, BAT+, V SET, COM (and there may be a " - ", but its a bit faded) and COM -. Can someone advise me on the wiring arrangements please? My preference would be to trickle charge but the engine start battery and the 2 domestic batteries, but if that is not possible/advisable, then the starter battery only. TIA.
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I'm making an educated gues, so follow this at your own risk!

PV+ to the solar panel +
BAT+ to the battery (fuse this one, as close as practicable to the battery)
COM/- negatives from battery & panel.

I'd guess V SET is something to do with calibration.

Actually, to test the panel, put it outside with a voltmeter on it. In March, in the southern UK, I'd expect to get 12v plus into a voltmeter much of the day. Around midday, I'd think the panel should get a 20w bulb good & bright as long as there's a bit of sun.
 
peter2407 said:
I am trying to wire up an 80w solar panel through a regulator to the battery bank, which I thought would be a simple job, but doesnt appear to be. The panel has a +ve and -ve marked lead, the regulator has connectors that say: PV+, BAT+, V SET, COM (and there may be a " - ", but its a bit faded) and COM -. Can someone advise me on the wiring arrangements please? My preference would be to trickle charge but the engine start battery and the 2 domestic batteries, but if that is not possible/advisable, then the starter battery only. TIA.
Click to expand...

I don't bother connecting solar to engine battery, it gets enough charge when the engine starts whereas the domestics take much longer to charge and can always start the engine in emergency. If you want to charge both then you either need a dual output regulator or 2 x regs, one to each battery.
 
I suspect that both COM terminals are COM - (common negative). You can test this with a multimeter, there should be 0 ohms (or a beep with the continuity tester) between the two terminals.
If that's the case, then the solar panel + goes to PV+, battery + goes to BAT + and the two negatives go to a COM - each.
V SET may be for battery sensing

wrt fuse, an 80W panel can nominally supply ~6.5A at 12V; realistically, you're probably going to get 30-50% of that. A 5A fuse should be fine, 10A will definitely cover it.

AFAICT, the fuse would be to protect in the event of the battery supplying a short circuit rather than a problem with the solar panel.
 
The fuse should be close to the connection to the battery +. Its purpose is to protect the regulator and the wiring from the very high current that the battery can deliver in the event of a fault.

It should be rated slightly higher than the maximum likely charging current. The wiring should have a safe current carrying capacity greater than the fuse rating. In reality the wring will have to be significantly heavier than this to avoid excessive volts drop and will depend upon max current and wiring run length.
 
Thanks

Thanks all. I was intending to be a cheap skate and use a regular two strand (term?) electrical extension lead for the wiring - any issue with that?
 
peter2407 said:
Thanks all. I was intending to be a cheap skate and use a regular two strand (term?) electrical extension lead for the wiring - any issue with that?
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Ordinary twin core flex will be Ok, although tinned cable is more corrosion resistant, provided the cable length is fairly short.

Solar panel output specs are quoted at the maximum power point which is typically around 17 to 18 volts for a 12 volt panel. This means at maximum power output the current will be around 4,5 amps for an 80 watt panel. Even when short circuited the current will still be less than about 5 amps.

However to avoid excessive volts drop the wiring must be heavier than domestic 6 amp (0.75mm²) cable if it is of any significant length

If the total positive plus negative wire length is 20 ft you will need AWG 14 or 2.0mm². If its 30 ft you will need AWG 12 (3.3mm²) and if its 40 ft you will need AWG 10 ( 5.26mm²) Graham's suggestion of 6mm is spot on then for 40 ft (or slightly more) Remember these are positive plus negative wire lengths. Ie double the actual cable run distance.
 
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peter2407 said:
Thanks all. Steve - what size fuse would you use?
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What the folk above said :)

VicS knows what he's talking about, so if he says 5 amps, that's what I'd use!

Graham's comment about connecting to the domestic battery makes sense but, if you're going to buy another controller, you can get a dual battery job for not a lot more than a half-decent single job. Call me Mr Paranoid, but my dual controller works on the starter battery until it burps, then turns its attention to the domestic. My reasoning is that that way, my starter battery is alway fully charged, even if the boat's been sitting for a while, so I can get the engine going, no matter what. If the domestic's got a bit tired, I can always start the engine to shove a bit in quickly. In practice, even in the middle of winter, both batteries are fully charged from the previous visit after a couple of weeks and, in summer, our 40w of panels keep up with general usage - lights, radio & so on provided I don't run the cold box, and I've got a fridge mate to make sure that only happens whan there's plenty of juice about.
 
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peter2407 said:
Thanks all. I was intending to be a cheap skate and use a regular two strand (term?) electrical extension lead for the wiring - any issue with that?
Click to expand...

This was the result of being a cheapskate. Owner added more solar panels, didn't bother uprating the cable or the fuses.
1b609ad6866b578a47065ec443fc39ad_zps55fe1dde.jpg
 
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