I am trying to set up a small 20W panel, I also need to connect outboard charger (5A), and smart mains charger. All plugged in turn into an external connection on the cockpit coaming. Have Phocos 4A rated controller, which states that it has a current draw of 4 mA. Connecting the battery to the controller with open circuit on the panel side, seemed to indicate that this draw was all the time.
As I only will use the boat+solar occasionally, I decided to use a plug system to disconnect the battery from the controller, and connect directly to the external deck socket. This should also prevent overloading the controller when using the o/b charger. To save further messing with plugs, I connected the solar input in parallel with the incomer. The theory being that an input voltage with an open circuit output shuld be OK for the controller.
With the battery thus connected to the input side, and no other connection, there is a voltage of circa 2V on the output of the controller. Conversely, with the battery connected to the output side of the controller, there is a voltage of 5.5V on the panel side. (Open circuit). This puzzles me, I thought it would have a diode to stop power loss through the panel.
Last but not least, I have blown three 10A fuses on the battery connection, for no apparent reason. The only current path that could do this that I can think of, is through the controller. All the other circuits test fine.
Any ideas?
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.
Select to expand quoteYara said..
With the battery thus connected to the input side, and no other connection, there is a voltage of circa 2V on the output of the controller.
Some educated guessing on the 2v output:
This may not be a big issue and could depend on the design of the regulator - it would normally expect to have it's output connected to a battery that may present a voltage of say 10v (batt flat) to around 12.8v (batt full). And the battery would have a finite Internal Resistance, so the regulator would not expect to see an "open circuit".
When it does see this "open circuit", then an output of 2v should not do any harm, although a good quality designer would probably tie the output to ground.
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?
Select to expand quoteTrek said..
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?
The battery is connected on the input side when I am trying to charge from the o/board or a mains charger. In this case the output of the solar controller is open circuit. I guessed it should be OK, as the voltages should be similar to a solar panel.
personally Id run the wire from the solar panel to the controller then to the(fused) battery and organize your other charging systems some other way K.I.S.S.
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?
Select to expand quoteHG02 said..
personally Id run the wire from the solar panel to the controller then to the(fused) battery and organize your other charging systems some other way K.I.S.S.
I agree. I run two panels and two controllers for two batteries. I would not bother with the outboard output. The panels need to be connected to the battery via a controller 24 hours a day. Use the power from the batteries via a rotary switch. If you have a main engine with an alternator that charges the battery via the rotary switch. When I leave the boat the batteries are shut off but the controllers still charge the batteries.
When you disconnect the panels there is going to be a lot of voltage going no where at certain times of the day if they are not fully covered.
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!
Select to expand quoteRamona said..
HG02 said..
personally Id run the wire from the solar panel to the controller then to the(fused) battery and organize your other charging systems some other way K.I.S.S.
I agree. I run two panels and two controllers for two batteries. I would not bother with the outboard output. The panels need to be connected to the battery via a controller 24 hours a day. Use the power from the batteries via a rotary switch. If you have a main engine with an alternator that charges the battery via the rotary switch. When I leave the boat the batteries are shut off but the controllers still charge the batteries.
When you disconnect the panels there is going to be a lot of voltage going no where at certain times of the day if they are not fully covered.
The boat is a trailer/sailer which spends 99% of its time under a tarp. The mains charger is fine for getting the battery fully charged before a trip. The panel will be mounted on the taffrail when I am sailing, and help the battery meet the demands of tiller pilot, sounder, etc., as well as recover from the previous night's use.
It appears that if you leave a controller connected to the battery, there is a small, but constant drain if no solar panel is connected. My research says that a Schottky diode is great for charging, but leaks from the battery when there is no sunlight. Also, call me silly, but I am loathe to drill more holes in the deck to mount another socket for the solar panel.
The boat l was racing on had a small panel 10 or 20w, and an old acid car battery. No regulator at all.
He never had any problems.
Let me ask: could one hook up three solar panels (120-80-80w) to an MPPT controller to charge three 100Ah AGM batteries, one a strarter and two house?
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
Yes, having no solar regulator may be OK sometimes if you manually control the charge by disconnecting and reconnecting, but consider...
I just got out one of my old 10W experimental solar panels (that sailors commonly use) and looked at its specification on the back. Its maximum power point is 18.39V. If the weather is endlessly sunny this “harmless” little panel connected direct to your 12V battery will eventually charge your battery to 18.39V. As it does that it will vaporise the batteries electrolyte which will increase its impedance until eventually you will have an 18V battery on a sunny day (kaboom stereo and radio) and and a battery that holds no charge on a dark day. (Known as a fried battery). I think people who have luck with that got lucky with just the right ratio of sun/dark/load/battery self discharge.
Re the 120+80+80, As HG said, depends on the regulator. Its rare to have a domestic regulator good for more than 50V (on input) so the panels would have to be in parallel which may not work. The reason being that various solar panels act as loads in the dark. Probably the biggest solar panel (with the highest maximum power point voltage would loose most of its power heating the smaller panels instead of charging the batteries. Maybe that could get fixed with blocking diodes but then you waste lots of the combined power you could get.
SInce its cold and not a boat day and Im at work I just tried putting 30V across my 10W solar panel to see what would happen. Its a 1.5A load. So if it was in parallel with your 80 or 120 panel it would soak up all their power. A separate controller for each panel and battery would work, Ive got that system on Trek.
Select to expand quoteTrek 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 .....
Select to expand quotescaramouche 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
Select to expand quoteYara 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.
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.
Select to expand quoteCharriot 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.
Thanks for clearing that up Charriot 
Select to expand quoteCharriot 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.
My question was theoretical as my system is a 120w panel with a controller charging three 100Ah batteries, one starter, two house.
I was thinking about installing an other two 80w flexible panels because the fridge is eating up my battery power in a day and a half or so in summer.
It looks like, it would be better starting the engine. By the time l burn the cost of the two panels and two controllers in diesel l'll be 120 years old.
Better utilise my old 40w panel for the starter battery with a new coontroller and separate the two house batteries for the panel.
Am l thinking correctly?
Select to expand quoteTrek 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.
Select to expand quotesirgallivant said..
My question was theoretical as my system is a 120w panel with a controller charging three 100Ah batteries, one starter, two house.
I was thinking about installing an other two 80w flexible panels because the fridge is eating up my battery power in a day and a half or so in summer.
It looks like, it would be better starting the engine. By the time l burn the cost of the two panels and two controllers in diesel l'll be 120 years old.
Better utilise my old 40w panel for the starter battery with a new coontroller and separate the two house batteries for the panel.
Am l thinking correctly?
Yep I get what you mean. If you can get another panel the same as the existing 120W one (and it will fit on boat) you can parallel them and have a "240W" panel if you wanted to. Just need a controller that can handle that and with luck the one you have might be able to. You'll obviously be doubling up on the current but keeping volts the same, that might be enough to keep the fridge going.
Select to expand quoteTrek 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)
pretty much the same with all rechargeable battery types. overcharging kills them...
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!
This site has some really good explanations on power: shore v solar v alternator.
roadslesstraveled.us/charging-rv-marine-batteries-solar-power-shore-power/
