Solar pannel?

Clyde_Wanderer

Clyde_Wanderer

Well-Known Member
Joined
15 Jun 2006
Messages
2,829
Location
Glasgow
Visit site
I intend buying a solar pannel to keep my batteries topped up while boat is on mooring.
I have 2 x 110ah batteries which I just want to keep topped up.
What size and watt/amp pannel do I need and how should it be wired, ie, should the cables from pannel just be connected to the batt,s and will they need to be disconnected when I am using the boat with engine running?
Please answer in simple terms as I am not too hot on electrics. /forums/images/graemlins/blush.gif
 
I would advise a 30-40 watt panel, if it is to be left connected all week, whilst you are away etc. then I would also reccomend a charge regulator, to stop your batteries from overcharging. This regulator, will stop any need for disconnection with engine running or at night. Simple battery insurance. IMHO
 
Thanks Scott.
Now can you recommend somewhere to get a pannel at reasonable price and what exactly am I looking for when I buy the regulator?
Will the regulator be adjustable output or preset?
Thanks, Eamonn.
 
I had 2 x 10W panels through a regulator to keep similiar sized batteries topped up and found that they did the job well. The boat was kept on a swinging mooring here in Cumbria.
Connections are from the panels -> regulator ->batteries. There's no need to disconnect when the engine is running. These panels are almost a fit and forget bit of kit. They only need to be kept clean.
 
Would suggest a 20W panel is all you need to keep batteries topped up, assuming no drain or nothing more than automatic bilge pump.
Regulators aren't adjustable -- why would you want to? -- just control charging to what batteries need and stop batteries discharging at night (diode function).

What type of panel would depend on where you plan to put it. Some are flexible or semi-flexible and can be walked on, some not. Rigid panels give you more watts for your £ but are heavier. What the other post says about shadows is correct. Thin film (very flexible) panels suffer less from this but are v pricey.

PBO did a good survey of the options, October 2005 issue.
Try also www.marlec.co.uk
www.ampair.com
www.barden-uk.com
 
Hello Eamon. When you c0ome to look at the panels and prices you will realise that alot depends onhow kmuch you want to spend and hopw much space you have for it.
I would not push for a regulator if you feed the 2 batteries from a panel unless it is larger than 10 watts.
Without a regulator you get as much charge as possible and a 10 watts gives about 450 milliamps which will not do any harm to a 110 AH battery no matter how how long and how well charged so certainly won't hurt 2 in paralell.
If you want to charge both batteries then 2 diodes will work well. The volt drop of the diodes won't make any significant difference. Or if you can find the diode built into the panel and get a connection to the panel itself +ve then you can duplicate the diode for the other battery.
However if you use a regulator then the old .7 v drop for each diode will matter unless the regulator is made for 2 batteries diode separated. PM me if you are confused.
I use a 2 watt panel lashed to the boom cover on my little boat as the only battery charging and it does OK. (not that I am suggesting such a small one) olewill
 
I've given up with the solar panel since moving 'north of the border'. It was 35W, and had little hope of success. Due to the extensive cloud cover and weakness of the sun up here it was not succesful.

Have switched to a Rutland 503 windcharger, and already it is proving it's worth. Very quiet, and much more 'juice per 24hrs'.
 
Talk to Barden. They know what they are about and will provide straightforward advice. We opted for a fixed panel on the coachroof garage with the option to supplement it with a flexible panel that can be moved around with the sun if you are on board. In the Med, the fixed panel alone does enough to maintain our four batteries when the boat is left for a while. You do need some sort of control device and we invested in a vwery good ( but not cheap) battery monitor from Merlin that provides the full story on DC charge and discharge rates and individual battery states.
 
Thanks for the advice guys, now I am confused William with diodes etc.
Mostly our trips are short, 8-12 daylight hrs at a time, and apart from a gps, echo, and vhf, and sometimes the radio, there isent anymore power used unless we use a mooring, which we dont do very often, so have shore power most nights.
So I wouldent think that the batts get down much, unless when on the mooring and using the auto bilge pump, although I dont have any system for monitering the batts, at present and apart from a 1, 2, all, off, switch there is no other wizardery.
 
I have 2 x 110 AH batteries and have a 12" x 18" panel, its about 12W. I don’t use a voltage regulator or charging regulator. In theory you need all these things but in practice you pays your money and makes your choice. I bought the panel from the Irvine boat jumble two years ago and its worked perfectly since. The boat is kept on a mooring at TCC, however the odd charge at Rothesay and Largs plus the panel means the batteries have never been off for charging since we fitted the panel. Our power consumption isn’t particularly high but we do have a propex gas heater.

Diodes are fairly simple devices, see text below.
A blocking diode is usually used to allow electricity to flow from the solar panels into the batteries, but not from the batteries to radiate out from the solar panel at night. The diode should be connected to the positive lead from the solar panel to the battery with the stripe (ring) around the diode situated on the battery side. [Ref http://www.reuk.co.uk/Put-Together-an-REUK-Solar-Lighting-Kit.htm]

I use two diodes one for each battery,
The banded end of one diode is connected to bat1 pos
The banded end of the other diode is connected to bat2 pos
The other ends of both diodes are connected to the solar panel pos
The neg side of the solar panel is connected to the neg on both batteries.

This system works ok for me and I am happy that I have not connected panel as per theory. You may hear all kinds of theories as to the damage that can be caused by the above setup but in practice the UK sunshine levels work fine as a regulator
 
Thanks Tony, looks like a good site.
I think the 10 or 20 watt would be ideal, I will need to find out more about the regulators, as I am not sure what one I would need.
Incidently what should the regulated charge value be for 2 110ah batts, and does that mean that I would have to have the selector switch set to 2 all the time in order for the pannel to be charging the two batts? or does the wires from the pannel connect to the regulator and from the reg direct to the batts?
Does anyone have a good wiring diagram for a solar pannel from which I could get more of an understanding from?
 
Thanks Davie.
That sounds like a simpler system, but are your two batteries connected to two pannels? as you say you have a diode on each positive wire to each batt, so I assume that one pannel wont have two positive wires from it, so have you two pannels?
Thanks, Eamonn. PS I couldent get the site you showed.
 
Hi Aemon I will try to explain the diode thing.
You have heard of a diode charge splitter for a dual battery system.
The diodes are like one way valves from the generator to the 2 batteries via 2 diodes. This means current cannot flow from the batteries but only into them. You connect direct to the battery +ve terminals and leave the switches off or in fact any position.
Now the diodes have a finite constant voltage drop of .7 volt. This means that a regulated generator set at 14 volts output will lose .7 volt in the diodes so the batteries will not charge well.

The current into a battery is a function of the difference between the battery actual voltage (depending on amount of charge) and the regulated charging voltage. This difference is 2 vollts with a partially charged battery but diminishes rapidly as the battery gets charge.
So .7 volt less is very significant. If the regulator senses on the battery side of the didoe then it can regulate to give 14 volts after the diode. However this is a bit difficult cos regulators usually don't have the sensing input available.

A solar regulator does the same job. It accepts whatever comes into the regulator from the panel and reduces it to 14 volts. So as the battery becomes charged the inherrent voltage rises, the difference of voltage is less so the current into the battery falls so protects the battery. Any more diodes after the regulator will greatly reduce the charge.

Now a solar panel alone has very unregulated characteristics.
It produces near 20 volts without a load. But as current is drawn from the panel the voltage falls. So if you connect a solar panel to a 12 volt battery it will push 450 ma into the battery but the voltage measured will be that of the battery. If you connect it to a 6 volt battery you will still get 450ma into the battery but the voltage measured will be 6 volts or so. The additional voltage is lost in the resistance of the elements of the panel. You can short out the panel leads and still get 450 ma with no voltage at the leads.

What this means is that with a "pushing" voltage of 20 volts from the panel and an opposing voltage of about 13 to 14 volts of the battery you get 450 ma constant into the battery right through from flat to fully charged. This gives a full charge eventually to the battery and when the battery is fully charged the excess is disipated in boiling the battery or in heat.

If you fit a diode in series it reduces the 20 volts to 19.3 which still leaves a large margin above the battery voltage for charging.

However with a large battery and small panel this boiling and heat is a nothing. The battery does not notice it. Check battery water level initially more often anyway.
But put a big panel on a small battery and you will destroy the battery.

Now most solar panels have one diode in series with the output to stop any current flow from battery to panel during darkness. This is mounted in a connection box at the panel on ones I have seen.
You can use this diode as a blocker between batteries as well as its intended purpose. Does 2 jobs.
If you can get a connection to the panel side of the blocking diode you add another diode of same type and orientation and provide a second positive wire. One + wire goes to each battery. (via a fuse at the battery) If however you fit the diodes at the battery terminal you do not need fuses as the current can not get past the diodes. (with the diodes at the panel a short any where along the +wire to -ve will allow battery current to melt the wires)

So I hope that explains the use of diodes and regulators. be wary of course that "experts" are most likely trying to sell regulators so using conservitism as an excuse will never admit regulator is often not needed. (unless with big panel and small batteries) olewill
 
Thanks again William, hope you arent pulling your hair out yet!
I get it now, so if I buy a 20 watt pannel, open the control box, check the diode type, buy another the exact same, splice in another wire to the +ve wire upstream of the original doide join new my diode to this new spliced wire, connect a red wire to the circle side of my new diode, which will then connect to the second batt, and Bob is my aunts husband?
Then because of the diodes there is no risk of each battery becomming connected to each other by using the two pannel +ve wires as a link between each other?
Sorry about all the finger tapping on this subject.
Thanks, Eamonn.
 
Quite so Eamon except don't panic too much about getting an identical diode. Any silicon diode in the 1amp current capacity will suffice. Voltage rating is not important. olewill
 
You must log in or register to reply here.

Other threads that may be of interest

W
Battery suicide
Replies
17
Views
604
Refueler
Refueler
P
Adding fuses to my batteries
2 3 4
Replies
61
Views
2K
AngusMcDoon
AngusMcDoon
D
Solar Panel wiring question
Replies
3
Views
223
William_H
W

Share this page

Top