If the 10A fuses are blowing then the current to do that is probably from the battery since none of the other sources mentioned can deliver 10A. . Maybe the Phocos is faulty.

If a solar regulator is connected to a battery and you measure its unconnected terminals where the solar panel would normally connect it would not be unusual to read a small voltage there. Solar regulators (good ones) use electronic parts called MOSFETS usually in a configuration called "ideal diode". Thats to get rid of the power wasted by the 0.6V loss across a diode. A few mA could leak through backwards and give you that reading.

The 4mA is probably normal, the little circuit inside the Phocos would need some power to work (light up the LED for example).

Sketch a circuit if you can and post it so we can see your wiring.

Also, unless I missed something shouldn't the battery be connected on the output side of the controller or are you trying to test it by connecting battery on input side?

Only one power source connected at a time.

I was told by a spakie, one does not need a controller for a 20w panel if one is disconecting it after use.
Is this correct?

It's true usually no harm will come connecting solar panel direct to battery but you lose a huge amount of power. If you look at datasheets of solar panels you will see they put out most power at 20v up to 35v. Check the one on my boat trek. Sms the word status to 0431935720. The voltage you see there is perfect for the given amount of Sun at that instant. Ie. My solar panel can put out 2.5amps at 35v. That's over 80watts. My regulator converts the 2.5amps at 35v into around 6amps at 12v which is 60w charge power. If I connected panel directly I would get 1.5a at 12v which is 18w because my panel can't work properly when forced down to 12v. Some solar panels conduct in reverse in the dark. So you would charge in daytime and flatten in night time *! wouldn't rely on the word of some sparkies!

i would not bother with the outboard charge either just go with the solar panel

That would depend on the MPPT controller, from memory mines 350 watt max maybe slightly more , they all vary
Ive a blue sea unit that charges all batteries drops out if the motor circuit is powered but keep the house going is power up.

www.12volt.com.au/redirect.html?a=/General%20Htmls/webcat2003/batterysystems.html

Trek said..
It's true usually no harm will come connecting solar panel direct to battery but you lose a huge amount of power. If you look at datasheets of solar panels you will see they put out most power at 20v up to 35v. Check the one on my boat trek. Sms the word status to 0431935720. The voltage you see there is perfect for the given amount of Sun at that instant. Ie. My solar panel can put out 2.5amps at 35v. That's over 80watts. My regulator converts the 2.5amps at 35v into around 6amps at 12v which is 60w charge power. If I connected panel directly I would get 1.5a at 12v which is 18w because my panel can't work properly when forced down to 12v. Some solar panels conduct in reverse in the dark. So you would charge in daytime and flatten in night time *! wouldn't rely on the word of some sparkies!

.... forgot to say only if the the solar panel charge is less than the load .....

scaramouche said..
Tried your status
very impressive,great system for peace of mind

Send 333 to 0466 838 137, even more cool, you can see Treks deck, but takes 2 min

As was mentioned before, 20W solar would not need controller , it just introducing about 0.5 volt drop.
solar panels are always equiped with build in diode, means there is no reverse current when in dark.
also there is no adverse affect if load is connected or not.
they supply current or not, that's what they do.
It is irrelevant when the other devices or charges are connected the same time, in fact, it is advantage to have
them connected because solar can add to change even when engine is running.

Charriot said..
As was mentioned before, 20W solar would not need controller , it just introducing about 0.5 volt drop.
solar panels are always equiped with build in diode, means there is no reverse current when in dark.
also there is no adverse affect if load is connected or not.
they supply current or not, that's what they do.
It is irrelevant when the other devices or charges are connected the same time, in fact, it is advantage to have
them connected because solar can add to change even when engine is running.

It might be surprising but a 20W solar panel can easily overcharge and wreck a 12V battery if left connected unchecked. I have done it! The electrolyte will eventually evaporate, the plates will buckle and bingo a dead battery with a shorted cell. When they don't its by good luck. I contract design solar electronic equipment for a battery company and they make a lot lot of sales to boat owners (and farmers) who have wrecked their batteries by either overcharging them or running them flat to completely dead. A controller will not let either happen.

Its true many solar panels have blocking diodes but many don't. The 10W unit I tested today above does NOT have a blocking diode because its out of an array. If you have an array of 20 solar panels you don't want 20 x 0.6V drop and the consequent waste of power. So many solar panels I design with do NOT have blocking diodes. And Schottky diodes are only a minor improvement, 0.4V drop instead of 0.6V.

It really is relevant what devices are connected at the same time. Ohms law. If the load on the battery is more than the charge current coming in the battery will eventually go flat.

If the current entering the battery is significantly more than it can handle it will eventually become overcharged, the electrolyte will evaporate and the battery will be wrecked. If you add a load to the battery higher than the current entering the battery it will eventually go flat instead.

You are right that leaving the solar connected takes load off the engine. The alternator on Trek turns out 40A so the 8A I can get out of my solar is pretty good by comparison. Someone tried that on cars to make them more efficient, but the 1kW solar on the car roof is a bit sad compared to a 100kW petrol engine.

Trek said..

Yara said..
Only one power source connected at a time.

Yara, how about this setup?



The socket is in cockpit. The 7.5A fuse means you can use the socket as an outlet (for spot light etc) when you are not charging via outboard or mains charger.

I have decided to bite the bullet, and completely separate the two systems. It only needs another socket connected to the controller. Then, when not in use, everything can be isolated. The final issue is whether the controller is faulty, and if I have the wiring by the book, I will be able to tell that.
Thanks everyone for your help.

Trek said..

Charriot said..
As was mentioned before, 20W solar would not need controller , it just introducing about 0.5 volt drop.
solar panels are always equiped with build in diode, means there is no reverse current when in dark.
also there is no adverse affect if load is connected or not.
they supply current or not, that's what they do.
It is irrelevant when the other devices or charges are connected the same time, in fact, it is advantage to have
them connected because solar can add to change even when engine is running.

It might be surprising but a 20W solar panel can easily overcharge and wreck a 12V battery if left connected unchecked. I have done it! The electrolyte will eventually evaporate, the plates will buckle and bingo a dead battery with a shorted cell. When they don't its by good luck. I contract design solar electronic equipment for a battery company and they make a lot lot of sales to boat owners (and farmers) who have wrecked their batteries by either overcharging them or running them flat to completely dead. A controller will not let either happen.

Its true many solar panels have blocking diodes but many don't. The 10W unit I tested today above does NOT have a blocking diode because its out of an array. If you have an array of 20 solar panels you don't want 20 x 0.6V drop and the consequent waste of power. So many solar panels I design with do NOT have blocking diodes. And Schottky diodes are only a minor improvement, 0.4V drop instead of 0.6V.

It really is relevant what devices are connected at the same time. Ohms law. If the load on the battery is more than the charge current coming in the battery will eventually go flat.

If the current entering the battery is significantly more than it can handle it will eventually become overcharged, the electrolyte will evaporate and the battery will be wrecked. If you add a load to the battery higher than the current entering the battery it will eventually go flat instead.

You are right that leaving the solar connected takes load off the engine. The alternator on Trek turns out 40A so the 8A I can get out of my solar is pretty good by comparison. Someone tried that on cars to make them more efficient, but the 1kW solar on the car roof is a bit sad compared to a 100kW petrol engine.

The array would not have been a 10 or 20 watt panel though would it ?
But I wouldn't do it either with controller and frying a battery

Theres another good article here

batteryuniversity.com/index.php/learn/article/charging_the_lead_acid_battery

Where the writer notes.......

"The correct setting of the charge voltage limit is critical and ranges from 2.30V to 2.45V per cell. Setting the voltage threshold is a compromise and battery experts refer to this as “dancing on the head of a needle.” On one hand, the battery wants to be fully charged to get maximum capacity and avoid sulfation on the negative plate; on the other hand, over-saturation by not switching to float charge causes grid corrosion on the positive plate. This also leads to gassing and water-loss"

........is what I've mentioned above. With no controller the battery charge voltage is uncontrolled. It will sooner than later be wrecked. But most farmers and sailors dont realise its their handling of the batteries charging that has killed it. They just think its a crook battery

(the 2.30V to 2.45V is x6 for a 12V battery)

Thanks Tony! But no, l got only the 120w and the old 40w at home. My controller is the one controlled the 40w panel before l got the 120w one. I think it is 10Amp, so it would not handle the two panels paralelled. Would need a 20Amp one if l figured correctly.
I would not have, at the moment, space for another 120w panel. I was thinking about two 50w ones zippered to the bimini, or get two 80w ones and hang them on the life lines on the quarters.
What does 'doubling up' on the current mean? Bigger fuses or what? (Current is watts.?)
At the moment there are no fuses between the charge controler and the battery connection. The system is running like this for years and years.
I am really electrically challenged.
Thanks for your advice mate!