Ineffective solar charging and upgrades

[fifer]

At the moment I have a 20W panel which is connected directly via the bus bars (no controller) through a BEP VSR to the 12V 140Ah domestic battey set and the starter battery. The starter battery is charged preferentially. The panel sits in front of the sprayhood under the boom, and the 27ft boat is on a swinging mooring. There is a Merlin Smartguage which monitors the domestic and starter battery voltage. This is all something the last owner set up.

Whilst I'm away from the boat the domestic battery voltage is maintained at whatever it is when I leave the boat, but never increases, even with all this sun.

I also have a shore power connection and CTEK M200 batterycharger which used to keep the batteries topped up whilst the boat lived on a pontoon.

I'd like to improve the battery charging whilst on the mooring and at anchor. If I buy a larger panel (and put it somewhere else) I presume I will need a controller and probably larger domestic batteries. I might also try and find a second hand wind generator at some point.

What modifications would I have to make to introduce a solar/wind controller to the current setup? Would the mains charger and solar charger compete with each other whilst connected to mains power? Any recommendations for controllers and/or panels up to 100W or so?

 

[Graham376]

How often do you use your boat? Do you leave your car battery on charge every time you leave it? Suggest you connect your panel via a small regulator directly to the domestic battery and leave the (presumably isolated) engine battery to just sit. Our left disconnected car battery will still start the engine first time when reconnected after 6 months or more.

 

[lw395]

You should get say an amp from the 20W panel. Maybe 6Ah a day.
5 days away from the boat should take it from say 70 to 85% charged?

What exactly do you want/need/hope for?

 

[Dutch01527]

I have a similar set up albeit with a regulator. Panel keeps both batteries charged with no problem even in winter. It also charges low level batteries back up over a few days.

I think that you have a fault somewhere in your system . I would pay a marine electrician to diagnose the problem. One of those jobs where experience could save a lot of time and money in the long run. It might be a simple fix.

I am pretty sure that buying a bigger panel is not the answer, that would charge faster but at the moment it is not charging at all and a bigger panel would not fix that issue.

 

[BabaYaga]

At the moment I have a 20W panel which is connected directly via the bus bars (no controller) through a BEP VSR to the 12V 140Ah domestic battey set and the starter battery. The starter battery is charged preferentially. The panel sits in front of the sprayhood under the boom, and the 27ft boat is on a swinging mooring. There is a Merlin Smartguage which monitors the domestic and starter battery voltage. This is all something the last owner set up.

Whilst I'm away from the boat the domestic battery voltage is maintained at whatever it is when I leave the boat, but never increases, even with all this sun.

I also have a shore power connection and CTEK M200 batterycharger which used to keep the batteries topped up whilst the boat lived on a pontoon.

I'd like to improve the battery charging whilst on the mooring and at anchor. If I buy a larger panel (and put it somewhere else) I presume I will need a controller and probably larger domestic batteries. I might also try and find a second hand wind generator at some point.

What modifications would I have to make to introduce a solar/wind controller to the current setup? Would the mains charger and solar charger compete with each other whilst connected to mains power? Any recommendations for controllers and/or panels up to 100W or so?

I think you must state voltages read on house and starter batteries to get useful replies.
In my view 20W on 140 Ah with no regulator and no load is asking for problems.

 

[adamlang]

Does the VSR cause the voltage to drop? I'm still trying to learn some of this stuff.

 

[fifer]

Bit more detail.

With the smartguage I can see the voltages on both batteries. The domestic bank usually hovers around 12.6ish whilst the starter ranges from 12.6 up to 13.2V. At 13.2V the VSR parallels the batteries and the voltage equalises over both at 12.6 or 12.7 - so nothing happening in terms of charging the batteries.

I'll check the open circuit voltage on the panel this eve whilst there's still light.

Thanks for the replies

 

[PaulRainbow]

Does the VSR cause the voltage to drop? I'm still trying to learn some of this stuff.

No, a VSR does not suffer from voltage drop in the way that diodes do.

 

[William_H]

I think the problem is in trying to use a VSR on a 20w solar panel. Essentially the solar panel connected directly to one battery will keep it fairly well charged but not enough to raise the voltage to 13.5 or so which the VSR is probably set to operate at. If the VSR should operate it will likely draw a significant portion of the 1 amp from the solar panel just operating the relay coil. I think 20w solar panel direct to largish battery is fine. If you want to feed 2 batteries fit 2 diodes (shotky type) in the wire from solar panel to each pos battery terminal. This will share the 1 amp between two batteries. Leave VSR and isolation switches off. However another simpler solution is to fit another solar panel feeding the other battery direct. Actual size of second panel depends on available mounting space and options. Any more than 20 w should have a controller. The purpose of the PWM (cheap) controllers is to limit solar charge when battery is fully charged to avert over charge and boiling. A small panel with large battery is not capable of overcharging so controller is useless.
If you do solar without regulator the solar charge will not be affected by mains charger but may theoretically reduce mains charger charge current so no concerns. Mains charger can be used via the VSR as plenty of power available to waste in VSR coil and to get voltage up to VSR volts to operate it. to share charge.
Note the current taken by the VSR coil would depend on it's capability. If it is also able to provide emergency starting battery paralleling then contacts must be large /heavy so needs a powerful coil to operate it. (possibly an amp) a smaller charge only type VSR might have a lighter coil perhaps only taking 1/4 amp. The electronics will take a small current all the time. All significant with just 1 amp of solar charge. ol'will

 

[fifer]

I did some quick tests on the panel last night. In the early evening in overcast conditions the open circuit voltage was 19.1V whilst the no load current was a low fraction of an amp. Therefore it's still an open question as to whether the panel produces and current in sunny conditions.

I'm thinking the panel is in all likelyhood the root of the problem now - It's a NASA Marine 20W which would be £130 to replace directly which seems very steep.

 

[ghostlymoron]

There's lots of cheaper 20w panels as about. I've had a couple of Lensum branded ones which were fine and cost about half the NASA ones
Incidentally I had a very similar set up to yours also on a swinger and found it kept the batteries well up. Usually weekend sailing and left during the week. I would therefore agree that the basic setup is fine and there's a fault somewhere.

 

[macd]

I'm thinking the panel is in all likelyhood the root of the problem now - It's a NASA Marine 20W which would be £130 to replace directly which seems very steep.

Steep it is, as said. I paid about that for our 85W panels, which have proved completely reliable. The NASA ones were probably bought by them as a generic.

 

[ghostlymoron]

You said the open circuit voltage is 19v which sounds ok but you need to disconnect from everything and but something like a 12v bulb on it to see if it lights up. I don't know what wattage perhaps someone could advise.

 

[peteK]

As already mentioned expecting a 20w panel to power the vsr and charge 2 batteries is expecting too much.
Rewire it leaving the vsr to charge the batteries via the alternator and the panels to charge via a regulater.

 

[fifer]

As already mentioned expecting a 20w panel to power the vsr and charge 2 batteries is expecting too much.
Rewire it leaving the vsr to charge the batteries via the alternator and the panels to charge via a regulater.

This is the VSR type.
http://www.bepmarine.com/en/710-140a

Would it really have that significant a power draw? It's selling point is its low power consumption.

 

[VicS]

I did some quick tests on the panel last night. In the early evening in overcast conditions the open circuit voltage was 19.1V whilst the no load current was a low fraction of an amp. Therefore it's still an open question as to whether the panel produces and current in sunny conditions.

I'm thinking the panel is in all likelyhood the root of the problem now - It's a NASA Marine 20W which would be £130 to replace directly which seems very steep.

In addition to checking the open circuit volts check the maximum, or short circuit, current. With everything else disconnected connect an ammeter directly to the panel while its in full sun A 20 watt panel should be able to deliver about 1.2 to 1.3 amps under these conditions

 

[ithet]

I have a 10w panel connected directly to 240a/h domestic bank (it was originally bought for small battery). Its open circuit voltage is about 19/20v and connected to the resting battery the most I see around 13v. It seems to keep the bank topped up so that after disconnection and stabilising I see 12.6-12.7v.

I also think you problem could be expecting to charge via a VSR.

 

[fifer]

Thanks for all the helpful replies!

I tested the panel again today in bright sunlight and whilst it generates an acceptable voltage it produces no current, therefore I've convinced myself it is dead.

I've also done some reading around the VSR issue brought up and I accept this may cause issues even with a new panel.

So there are a few options now:
1) Get a new 20W panel and controller and wire it up to the batteries bypassing the VSR as suggested (cheaper and relatively simple).
2) Get a bigger panel and controller and wire it to the VSR in the current manner (more expensive and harder to find a suitable location on a small boat)
3) Something else?

I'll need to go have a think!

 

[VicS]

I have a 10w panel connected directly to 240a/h domestic bank (it was originally bought for small battery). Its open circuit voltage is about 19/20v and connected to the resting battery the most I see around 13v. It seems to keep the bank topped up so that after disconnection and stabilising I see 12.6-12.7v.

I also think you problem could be expecting to charge via a VSR.[/QUOTE]

If the solar panel does not get the priority battery above 13 volts then the VSR won't charge the second battery because it does not operate until it reaches 13.2 volts.

In the OP's case the priority battery is the smaller engine start battery. Hopefully that will reach 13.2 volts without problems but the trouble my arise if the house battery is so low that that VSR will not stay closed long enough to get it above 12.7V which is the voltage at which it disengages

 

[Kurrawong_Kid]

I was going to replace 2 old solar panels (20 watt) because I thought they were shot! However Henry, at Fox’s (now left) persuaded me to invest in a set of mounts to enable the panels to be directed more effectively towards the sun. In bright sunlight they will input 2 amps when that is done, but only .3/4 amps if off centre. Try alignment first!