Solar panel ....Do I really need a smart charger?

[ctroutz]

Pretty fed up last few months having to lug 2x110 batteries off boat to re-charge as they lose it completely (no ignition light or even gauges) after only about a fortnight. Being an electroplank I'm trying to make contact with someone in the yard (Kemps Southampton) to check it out but in the meantime I've invested anyway in two new Batteries to prove a point.
Related to this I was intending to fit the 50w solar panel I took off my old boat and bought a cheap 10amp regulator to go with it. My intention was to leave it connected permanently as some sort of insurance in respect of engine starting. Is that enough or would I be better off with a decent 'smart' charger instead? So far, to keep it simple I've only been using the switch in BOTH or OFF modes and the 'leakage' has been happening while it's been OFF.
I'd appreciate some advice or If I get really lucky there'll be someone locally out there who praps would have a look for 'mates rates'.
Many thanks, Graham.

 

[Kelpie]

Get the solar panel hooked up, stop draining your batteries as you are killing them.
I did my own solar setup with a 50w panel and a PWM controller, total cost under £100.

 

[macd]

ctroutz: there's no way two 110Ah batteries should discharge totally in a fortnight unless they're either very ill or there is a significant drain on them whilst main switch is 'off' (bilge pump busy, perhaps?)

If there is no significant drain on them, they can be expected to self-discharge by around 1% per week, depending on temperature. As Kelpie suggests, a 50W panel will more than cover this, even in a British winter.

'Smart' charging is another issue. With the simplest (=cheapest) sort of charger, the batteries will probably never be charged more than about 85%. This is not good for their long-term health, as well as denying you the use of 15% of their nominal capacity (but actually 30% or more of their true available capacity, since they should not be discharged by more than around 50% or, again, their life span suffers).

 

[ctroutz]

ctroutz: there's no way two 110Ah batteries should discharge totally in a fortnight unless they're either very ill or there is a significant drain on them whilst main switch is 'off' (bilge pump busy, perhaps?)

If there is no significant drain on them, they can be expected to self-discharge by around 1% per week, depending on temperature. As Kelpie suggests, a 50W panel will more than cover this, even in a British winter.

'Smart' charging is another issue. With the simplest (=cheapest) sort of charger, the batteries will probably never be charged more than about 85%. This is not good for their long-term health, as well as denying you the use of 15% of their nominal capacity (but actually 30% or more of their true available capacity, since they should not be discharged by more than around 50% or, again, their life span suffers).

Thanks Kelpie and Macd. I should have thought of the bilge pump. I've only been able to do a 'drop' test on the old batteries but that showed OK.
From what you say, I'd better sort this out before I fit my new batteries. I take your point about cheap chargers but what's cheap (£50-60 has been suggested as adequate ?) What I can't get my head round is whether there is any point in fitting a 'smart' charger between panel and batteries, as well as or instead of the regulator I mentioned???

 

[TQA]

With the set up and use pattern you describe all you need is the simplest possible regulator to avoid overcharging.

Although I would not recommend this you could probably get away without any regulator at all just connect the panel directly but make sure the circuit has a blocking diode in somewhere.

 

[Kelpie]

Most solar panels have a diode built in.
I dont't use any kind of charge, smart or not, just a PWM charge controller (regulator) which you can get for about £20 from eBay. Appears to do a very good job.

 

[Stemar]

I have one of these to control my two 20w panels and charge an 85AH starter battery and 125AH domestic. It works on the starter battery until it's full then turns its attention to the domestic one.

Last winter it put back what I used over a weekend on board by the following weekend and kept up with our needs (lights, water pump& occasional CD player) at anchor during the summer. Just a happy customer.

 

[VicS]

Thanks Kelpie and Macd. I should have thought of the bilge pump. I've only been able to do a 'drop' test on the old batteries but that showed OK.
From what you say, I'd better sort this out before I fit my new batteries. I take your point about cheap chargers but what's cheap (£50-60 has been suggested as adequate ?) What I can't get my head round is whether there is any point in fitting a 'smart' charger between panel and batteries, as well as or instead of the regulator I mentioned???

I dont understand what you mean by this.

Fit a solar panel and a regulator, preferably a PWM or MPPT one.

BUT with bilge pump on auto you will probably also need to fit a battery charger. As it will be left on all the time you really need an automatic/ smart charger to avoid overcharging.

I suggest you look at the range of Ctek chargers and choose one appropriate for your total battery capacity.


This leaves one issue however.

To charge both batteries you either need to

• leave the selector switch set on both.
• or find a dual output charger and solar regulator
• or install some form of split charging system such as a VSR
• or just charge and use one battery at a time

 

[RichardS]

As someone above said, for £100 you can get a 40W panel + PWM controller which will keep independently fully charged two different sets of batteries.

I have my three house batteries as one set and my two starter batteries as the other set and they are always fully charged even though I leave the boat for 4 or 5 months at a time over winter.

The panel is secured to the deck with cable ties and the wiring from the batteries to the controller is plain home 3 core solid. Took a few minutes to wire up as the cables just run across the saloon floor. I pack it all away in a locker when I am on board. I will wire it up permanently with proper marine cable one day but it's well down the jobs list. In the meantime, my batteries are kept in the best possible condition.

Richard

 

[macd]

I dont understand what you mean by this...BUT with bilge pump on auto you will probably also need to fit a battery charger.
[/LIST]

That was my understanding, too, of ctroutz' reference to a (battery) charger, as a quite distinct entity from a solar regulator/controller (which need only be fairly basic).

 

[seadog30]

Hi

+1 to comments from Mac

We have 2 x 110Ahr house batteries and a 20 watt solar unit (with no regulator) hard wired to the battery bank (with a 5Amp fuse to protect the wires.) 20 Watts keeps the batteries fresh and as the batteries are now 6 or 7 years old and in good condition. I check the resting volts every month or so and they are always better than 12.8V. When we use a lot of power i.e. being on board for a few days running the engine on the way back adds the main recharge and the solar while on the mooring keeps the batteries topped up.

So the message is get some new batteries as your current ones must be clapped and connect a small Solar unit to maintain the charge, you do not need a regulator with only 20 or 30 Watts solar as this will not fry 220 Ahr of battery.

If you want sufficient solar to fully recharge the battery i.e. 100Watts + then you will need a regulator.

Good luck

 

[William_H]

I imagine by "smart charger OP means a solar panel controller (regulator) with smart charge characteristics. ie large charge at first then tapering off to float charge in stages.
This concept is fine for a charger being fed by mains or even engine alternator with unlimited power available.
With solar especially in winter in UK with limited panel size the whole concept is lost in that max current is quite small so smart characteristics can't work. ie it would be on max current all the time. You might as well fit a simple cheap regulator which cuts charge in the (unlikely) event batteries are fully charged or just risk no regulator and give batteries all that solar can provide. Actual solar current depends on orientation of the panel to sun (at midday) and angled to the suns inclination low in winter. If you are ona swing mooring then solar current will be much less because you can't orientate to the sun (south).
So just fit the panels witha regulator and see how the batteries go. Obviously a bilge pump will drain the batteries. With a large leak the solar may not be able to keep up anyway. So you really need to know the daily current consumption. good luck olewill

 

[VicS]

Hi

+1 to comments from Mac

We have 2 x 110Ahr house batteries and a 20 watt solar unit (with no regulator) hard wired to the battery bank (with a 5Amp fuse to protect the wires.) 20 Watts keeps the batteries fresh and as the batteries are now 6 or 7 years old and in good condition. I check the resting volts every month or so and they are always better than 12.8V. When we use a lot of power i.e. being on board for a few days running the engine on the way back adds the main recharge and the solar while on the mooring keeps the batteries topped up.

So the message is get some new batteries as your current ones must be clapped and connect a small Solar unit to maintain the charge, you do not need a regulator with only 20 or 30 Watts solar as this will not fry 220 Ahr of battery.

If you want sufficient solar to fully recharge the battery i.e. 100Watts + then you will need a regulator.

Good luck

Rule of thumb is that up to 10 watts per 100Ah does not need a regulator.

 

[GHA]

you do not need a regulator with only 20 or 30 Watts solar as this will not fry 220 Ahr of battery.

It could though.....

 

[charles_reed]

Reading between the lines, I suspect the OP has asked the wrong question(s).

It appears he has a problem of his two 110 AH batteries going flat in a week - whether or not this is due to having an electric bilge pump constantly on is a moot point which he has not confirmed. If two 110AH batteries are being flattened in a week, by his bilge pump he has and immediate and obvious danger - a pretty large leak which will, given a chance, sink his boat.
Alternatively, no bilge pumps but his batteries are flat in a week - either duff batteries or a wiring fault.
If my reading of the thread is correct (and like others I'm confused by the information) the question about a "smart" charger and a 50 watt (he says amps but I hesitate to believe that) will do nothing to relieve the problem - in fact a 50w PV panel into 220 AH of battery probably needs no controller at all.

So perhaps, instead of us all trotting around like a flock of sheep with an untrained dog - perhaps the OP could refine his situation:-

Does he have 2 110AH batteries? For how long? How does he usually charge them - from the OP, he appears to take them back home and charge them there. What sort of charger? How does he know it works? Does he have a permanently working bilge-pump? If so, does he know why?
Finally, and in answer to his original question - there is no such thing as a "smart" charger for solar panels. He could, if he wanted to throw his money away fit an MPPT controller, or if less generous a PWM controller but with a 50w panel, in a UK winter he probably needs neither, but in summer, might be advised to fit a £5 on-off unit.

Meanwhile, I'll go back to that long grass in the far corner of the field and stop anxiously running round like all you tups. (I'm surprised @ VicS, not being more acerbic)

 

[sailinglegend420]

..... - in fact a 50w PV panel into 220 AH of battery probably needs no controller at all.......

Charles, you and several posters need to watch the video above from Maine Sail in the USA. He's one of the most respected posters on the whole internet. He demonstrates that even with a small 12 watt panel with no controller it will be putting over 15 volts into a fully charged 220 Ah Lifeline AGM. It only puts in 0.7 amps because the battery limits how much current it will take, but it's the voltage that does the damage. Anything above 14.4v will cause excessive gassing when the battery is already fully charged. Open cell batteries can be topped up, but sealed batteries will be murdered!

Finally, and in answer to his original question - there is no such thing as a "smart" charger for solar panels......

Not quite sure what you mean by this?

There are of course "Smart" multi-stage solar chargers or charge controllers or regulators - call them what you like - that go to an Absorption voltage of about 14.4v and then drop down to a lower Float voltage when they "think" the batteries are fully charged. If you're trying to be smart by saying there are no such things as " Smart" solar chargers because they are not that smart then I would agree with you - but I think you could just be misleading readers.

 

[Ruffles]

It appears he has a problem of his two 110 AH batteries going flat in a week -

Absolutely.

I have two 110 Ah batteries. Newest is over 10 years old. They seem to last 6 months on the hard and still start the engine.

Definitely prioritise fixing this over buying more gadgets.

 

[William_H]

Charles, you and several posters need to watch the video above from Maine Sail in the USA. He's one of the most respected posters on the whole internet. He demonstrates that even with a small 12 watt panel with no controller it will be putting over 15 volts into a fully charged 220 Ah Lifeline AGM. It only puts in 0.7 amps because the battery limits how much current it will take, but it's the voltage that does the damage. Anything above 14.4v will cause excessive gassing when the battery is already fully charged. Open cell batteries can be topped up, but sealed batteries will be murdered!


Not quite sure what you mean by this?

There are of course "Smart" multi-stage solar chargers or charge controllers or regulators - call them what you like - that go to an Absorption voltage of about 14.4v and then drop down to a lower Float voltage when they "think" the batteries are fully charged. If you're trying to be smart by saying there are no such things as " Smart" solar chargers because they are not that smart then I would agree with you - but I think you could just be misleading readers.

This statement that it is the volts that damage a battery can be misleading. Sure any lead acid battery showing 15 volts at the terminals on charge is definitely fully charged and should definitely be absorbing many amps (depending on the size of the battery) and will be overcharged. However a 15 watt pael in full sun and best orientated will only give .75 amp.
That means that with a big battery 220AH it could never get the battery up to 15volts. (it could get a small battery up to more than 15v of course) The voltage of the panel falls with current. The .75 amp is hardly more than a trickle charge which is OK to be fed in constantly. Then factor in that your .75 amps will only be for a part of any 24hr period. ie about 8 hrs.
You may respect the US poster but I don't. Just do the voltage and current measurements yourself if you can get enough sun to work the panel fully.
So back to the simple statement a small solar panel without regulator or control is OK on a large battery. Not a large panel or not on a small battery.
Bare in mind also that you can get a lot more usn in parts of USA than UK.
Meanwhile I have 30 watts into a 85 AH battery with no regulator or control. No sign of overcharge after a year but then on a timer it runs lights every night for a few hours so is discharged a fair bit. However it is nearly summer here (36max today) so lots of sun. good luck olewill

 

[GHA]

That means that with a big battery 220AH it could never get the battery up to 15volts. (it could get a small battery up to more than 15v of course)

How come the meter in the video is showing over 15v with a 12w panel connected to 220Ah?

 

[VicS]

Rule of thumb is that up to 10 watts per 100Ah does not need a regulator.

But I am inclined to take note of the warning in the video.

I have had disappointingly short lives for batteries around the 50 to 60Ah size connected to a 5 watt unregulated solar panel on the boat.
Car batteries meanwhile have been lasting well ~ 2 are around 10 years and still OK.