One or two charge controllers needed?

Otter

Otter

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Just taken delivery of two 60w solar panels for either side of the wheelhouse roof.

Neither have an integrated blocking diode, so in darkness they will drain the battery. Both will be badly affected by shadows if they fall on the panel, so I thought I might need two controllers rather than wiring them in together to one controller. If one panel is shaded then will the good panel pass power into the bad one etc?

What's the best budget charge controller that has an integrated blocking diode and will isolate from the batteries when they are fully charged?

Is there a simple meter to show how much juice the panel is producing?

Thanks.


Simon
 
I won't pretend to great expertise, but I did the same as you, got two, albeit smaller panels, for the same reason of shading. I wired them in parallel into a single dual battery controller. I got this one :http://www.sunstore.co.uk/EP-Solar-Duo-Battery-Solar-Charge-Controller-12-24v-10A.html and it seems to be doing what it says on the tin.

As for whether the shaded one would steal from the good one, since they give some charge even on a dull day, when there aren't any shadows, I wouldn't expect it to be a problem.

A simple ammeter in the charging circuit would tell you how much charge you're getting. I'd fit it just downstream of the controller. Chinese ones on Fleabay for around a fiver. If you want to go all posh, Sunstore has a cleverer gizmo for around £35.
 
Merely solder a diode inline on each panel to prevent the issue?

Then I can recommend any MPPT controller, but I use the HRDX Marlec one with the Wind Gen input too, and outputs for both Starter and Domestics.
 
The discharge into a shaded panel is very small. Usually the losses in a blocking diode are higher than the savings.

If the solar controller has a mechanism to prevent overall discharge (90% of them do) then just wire the 2 panels in parallel to the single controler and forget any additional diodes.

The improvement with a MPPT regulator when the two panels are likely to experience disparate conditions will be small. With a cheap MPPT regulator you may well see a net loss compared with a simpler PWM type.
 
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It's debateable whether the night time loss of power versus the power loss caused by blocking diodes is worth bothering about. Certainly at this time of year, when we have getting on for 18 hours of daylight, I remove the blocking diode from my setup. I put it back in in the Autumn but it's questionable whether or not it makes any real difference even then.
 
It's an idea. The set up is two 60w panels into a bank of 4x105ah batteries. On a really good day I may see 4amps an hour going in, as that is less than the 1% rule I don't strictly need a charge controller. I guess I could just switch the panel feed to the batteries off at night?

Über dumb question - it doesn't do solar panels any harm to be in full sun but not connected to anything does it?
 
You could switch the panels off at night, but it's hardly worth it unless you are going to get up at 4.00am to switch on again!
If you are going to get up at a sensible time then you will have lost any charge from sunrise....though admitedly they would not be pumping power into your batteries at full chat.

No problem with leaving the panels on open circuit (i.e. not connected)

Personally, I would monitor the performance of the panels for a while, then decide what to do about controllers and/or blocking diodes. If you leave the boat unattended for long periods then overcharging could conceivably become a problem, but it all depends on your usage.
You might also want to look up "bypass diodes" if shading of the panels is an issue. Same diodes, but wired up differently and perform a different function.
 
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