Solar panel connecting, what do I need?

[ctroutz]

I'd like to fit a solar panel on my Colvic Watson. At present I rely on two 110ah batteries(pos.to pos, neg.to neg.)via a normal 3 position switch but I only normally operate on OFF or BOTH.
I have a panel (bout 800mmx700mm) taken off my old boat, prob. 10+ yrs old? No Maker's details but the plate' states; YDMO5OWS Max power 50w,
Voltage @ PMax 17.8v, Current@PMax 2.80 amps,Open circuit voltage21.6v,Short Circuit current 3.03 amps,Max op. system voltage 1000v. Not sure which bits are important so I've put it all down.
I've got basic wiring diagrams but haven't a clue as to what voltage regulator or controller to get or anything else I might need. To keep it simple I was going to avoid the switch and just wire direct to the batteries.
I'd much appreciate some help and suggestions..... Thanks.

 

[tawhiri]

You will need a regulator. I cooked my battery with a direct connection from a 50W pannal. However that was in Croatia during summer. You either need a dual regulator or have the batteries on the Both postion when you are not on board. Put the regulator as close a posible to batteries with a fuse on the plus line between battery + and regulator output. I have a cheap 10 Amp regulator which cost 6 quid. When I am on board it is only connected to the house battery and when I am away it is connected to both. The point is that most of the work is being done by the regulator, so the voltage drop between battery and regulator should be as small as possble, with a generous cross section wire as short as possible.
No doubt others will try and convince you to buy an MPPT.

 

[VicMallows]

Agree. One of the £6 PWM regulators (originally intended for street lights) available on EBAY will be fine. (some at £6 are actually advertised as MPPT, but I would be be very skeptical of that claim). A bonus is that they also provide a very effective dusk-dawn function for the anchor light!

 

[LadyInBed]

A bonus is that they also provide a very effective dusk-dawn function for the anchor light!

There's a thought, a relay across the Reg 'Lighting' output to turn the anchor light On - Off :encouragement:

PS Or are those terminals 12v continious o/p?

 

[VicS]

There's a thought, a relay across the Reg 'Lighting' output to turn the anchor light On - Off :encouragement:

PS Or are those terminals 12v continious o/p?

I think you will find the function of the load terminals varies.

Regulators intended for street light systems will turn a light on at dusk and off at dawn. Check the specs but there may be no need for a relay to switch an anchor light.

Other types will switch a load off when the battery volts falls below a certain level and back on again when risen to some higher level. Can be used to stop a fridge running a battery unacceptably low for example.

 

[bluerm166]

To answer the question :
If you intend to wire 'directly' to the batteries,one way is to connect the solar panel to a regulator,then split the emerging positive cable with a changeover switch that connects to battery 1 or 2,each via an inline fuse again on the positive.Alternatively there is a previous recent thread about using a regulator with twin outputs that will charge either battery automatically as it needs it,avoiding the need for manual changeover.The regulator will probably be 6 amp rated.The fuses can be rated 5 amps and are essential.If you use a simple changeover switch it can be 12/24 volt and handle say 10 amps.

PS It's not clear if your batteries are actually wired in tandem so as to operate together whatever one/both/two switch position is used.If they are always linked then a twin output regulator (or changeover switch) wont do anything for you.

 

[William_H]

There is the option of direct connection to the batteries but via 2 diodes to the +ve terminals of the battery. This means batteries can be left in the off position. If the diodes are physically near the battery terminals you will not need a fuse at each battery. Otherwise you will. Charging without a reg may be OK if panel is falt (as needed if boat is on a swing mooring) and you are in high latitudes and have large batteries.
If you want a regulator then how about 2 regulators fed by one solar panel. That will mean each battery is isolated from the other and charged accordingly.
Or as said one regulator with 2 outputs. good luck olewill

 

[ctroutz]

THANKS ALL, very helpful.....dunno what thickos like me would do without you! Olewill...What do you mean by 'falt'? not 'full at low tide' I take it, although I've had a boat that was. Also, is the diode option in addition or instead of regulator(s)? Bluerm...Currently 2 batts. connected pos/pos, neg/neg. That's parallel innit???
I think I'll order a couple of those ebay regs. anyway while I'm pondering. Cheers y'all.

 

[tawhiri]

Yes two regulators will controll the batteries independantly. However the leakage current from my regulator is 30mA and if you use two regulators then you will have 60mA leakage current.
Over a night time 12 hour period this will be more than 1 Amp hour.

 

[ctroutz]

Yes two regulators will controll the batteries independantly. However the leakage current from my regulator is 30mA and if you use two regulators then you will have 60mA leakage current.
Over a night time 12 hour period this will be more than 1 Amp hour.

Hi thanks for that. Is a loss of 1 amp hour a lot? Overnight, could you not isolate one battery on the main switch or some other way?
(think I'd better invest in a guide to understanding electricity before I sail too far).

Do the PWM regulators suggested come from China? Most cheapish ones appear to on ebay. Do the ones suggested have a 'name' ? Thanks.

 

[bluerm166]

I don't think you can charge two parallelled batteries independently so if you keep this arrangement only one regulator is required.Only if you separate the batteries and combine them in normal use as you now do via the power switch 'BOTH' position (or one at a time),so disconnect them via the 'OFF' position,could you then wire the solar charge separately to each to operate when you leave the boat.

 

[VicS]

I'd like to fit a solar panel on my Colvic Watson. At present I rely on two 110ah batteries(pos.to pos, neg.to neg.)via a normal 3 position switch but I only normally operate on OFF or BOTH.

I'd much appreciate some help and suggestions..... Thanks.

To answer the question :
If you intend to wire 'directly' to the batteries,one way is to connect the solar panel to a regulator,then split the emerging positive cable with a changeover switch that connects to battery 1 or 2,each via an inline fuse again on the positive.Alternatively there is a previous recent thread about using a regulator with twin outputs that will charge either battery automatically as it needs it,avoiding the need for manual changeover.The regulator will probably be 6 amp rated.The fuses can be rated 5 amps and are essential.If you use a simple changeover switch it can be 12/24 volt and handle say 10 amps.

PS It's not clear if your batteries are actually wired in tandem so as to operate together whatever one/both/two switch position is used.If they are always linked then a twin output regulator (or changeover switch) wont do anything for you.

I don't think you can charge two parallelled batteries independently so if you keep this arrangement only one regulator is required.Only if you separate the batteries and combine them in normal use as you now do via the power switch 'BOTH' position (or one at a time),so disconnect them via the 'OFF' position,could you then wire the solar charge separately to each to operate when you leave the boat.

THANKS ALL, Olewill...What do you mean by 'falt'? ...Currently 2 batts. connected pos/pos, neg/neg. That's parallel innit???
I think I'll order a couple of those ebay regs. anyway while I'm pondering. Cheers y'all.

A typo. He means flat ... as opposed to inclined towards the sun.



Your present wiring of the batteries seems a bit odd. You say you have them connected permanently together in parallel yet you also say you have a 1,2,both,off switch.

The normal way, and the most simple way of combining two batteries with a 1,2,both switch is shown below in figure 1.
It allows you to select either battery, or both, to be in use or charging from the engine. This gives you the option of using one or other for starting and using the other for running the domestic services etc when the engine is not running.

Figure 2 shows how a solar panel can be connected using a dual output regulator ( fuses in the + connections omitted for clarity) This allows the two batteries to be charged independently even when the main isolator is off.

There would be no point in using a dual regulator, or two separate regulators, if the batteries are permanently connected together in parallel.

There will now be posts from those who think 1,2,both switches should never have been invented urging you to adopt what they consider to be a "better" and "simpler" system using 3 separate on/off switches instead of the single selector switch, but thats their problem.

 

[VicMallows]

Hi thanks for that. Is a loss of 1 amp hour a lot?

Well, if you consider just one night it probably is not of much significance. But over a month it would be quite significant for many boats! .....although hopefully the solar panel would more than keep up.

I think that figure is rather pessimistic though. I've measured my (cheap, street light, PWM) controller as consuming 10-20mA in night-time mode. I then realised that nearly all of this is to illuminate the LED indicator lights! When I get around to it I will fit a switch to turn off the lights.

 

[William_H]

Thanks Vic olewill is nhot only old but going dyslexic. I did mean flat and yes as opposed to angled to the sun at midday.
I did not realise that PWM controllers waste so much current on standby and perhaps VicMallows has the answer in disconnecting lights.
Now much depends on how the OP views his batteries especially when he leaves the boat. Does he insist on switching batteries off for safety or is he willing to leave them on both position with potentially power to many devices. Many would say all should be off but in modern times so many devices are left connected to battery ie clocks radio memory gas alarms bilge pumps etc (plus solar and wind gens) that you wonder why we would try to disconnect everything else. (even though the switch was fitted to provide complete disconnection of all)
Anyway if he is happy to leave battery switch on "both" then both batteries can be treated as one for solar charging.
If however he wants to leave power "off" then both batteries are isolated frrom one another. This can be good if one battery is not as healthy as the other. (a dead one may kill the other), then to feed the 2 batteries from one panel he needs diodes. Now a silicn diode drops .7 volt regardless of current. This is not a problem if the panel feeds the battery directly. The panel does not produce a regulated voltage but rather up to 20 volts dpending on sunshine and this is dragged down by current flow to equal that of the battery. So losing .7 volt will not greatly affect charge.
However to avoid overcharge of a battery you need to feed it with a regulated 14volts or cut off charge when the battery volts reach 14v (maybe a bit more) Now if you have a regulator that feeds 2 batteries via 2 diodes then that .7 volt will make the regulator/controller think the battery has reached 14v when it has only reached 13.3v.(not enough to charge the battery) So you need to up the regulated or cut off voltage of the regulator/ controller or have 2 regulators fed from one panel via diodes before they start regulating/controlling.
All this talk of regulators assumes that you will get enough sunshine /power from the panel to overcharge the battery. Maybe yes maybe no. It would be worth monitoring actual performance.
Another option being 2 panels. any way you choose good luck olewill

 

[whiteoaks7]

All seems a bit complicated this. If the batteries are hard wired together then they are one battery. If they are separate then a diode to split the delivery of power is good but make it a Schottky type since these have a very low forward voltage loss - not the 0.7 volts someone was quoting. The downside of doing the diode trick is that a failing battery will suck all the energy available into it at the expense of the other so don't do it if one of the batteries is dodgy (I speak from experience). You do need a regulator, a PWM will do. If you want to find out how much energy you can capture have a look at the european JRC website http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#. although there are many others.

We feed solar power only to the house battery since the start battery is virtually always charged by default when the engine runs so we sidestep the switch, however, if the starter does need a top-up switching to 'both' - providing the input voltage is higher than both battery voltages - is an option we take.

Love the anchor light idea - I wish I'd thought of that before spending time with the soldering iron!