Connecting a battery charger to a battery that has solar panels connected

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Avocet

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Hopefully a simple question! I have a couple of small, sealed lead acid batteries in parallel. They're about 25Ah each. There are currently 4 cheap 10 Watt solar panels connected to them, and a small load. At this time of year, and in cloudy Cumbria, the panels can't quite keep pace with the load. Can I just connect a charger to the batteries without disconnecting the solar panels, to give them a quick top-up, or do I risk damaging the panels by connecting the charger?

Two of the panels are these:

10W 12V solar panel (2m cable) for camper /caravan /boat 10 watt trickle charger | eBay

and two are these:

Powoxi Solar Panel , 12V 10W Magnetic Solar Battery Charger | eBay

All seem to have some electronics on the back of them, which I assume contain a diode of some sort?
 
Avocet said:
Hopefully a simple question! I have a couple of small, sealed lead acid batteries in parallel. They're about 25Ah each. There are currently 4 cheap 10 Watt solar panels connected to them, and a small load. At this time of year, and in cloudy Cumbria, the panels can't quite keep pace with the load. Can I just connect a charger to the batteries without disconnecting the solar panels, to give them a quick top-up, or do I risk damaging the panels by connecting the charger?

Two of the panels are these:

10W 12V solar panel (2m cable) for camper /caravan /boat 10 watt trickle charger | eBay

and two are these:

Powoxi Solar Panel , 12V 10W Magnetic Solar Battery Charger | eBay

All seem to have some electronics on the back of them, which I assume contain a diode of some sort?
Click to expand...
Yes you can connect your battery charger without disconnecting the solar panels.

The panels will have blocking diodes to prevent a small backwards flow at night.

With 40 watts of solar into only 50Ah of battery capacity you should have some form of regulator. (just PWM, MPPT not necessary) especially with sealed batteries. (A commonly applied rule of thumb says that 5watts is the maximum unregulated solar power for 50 Ah of battery capacity)

If possible a significant increase in battery capacity would be worthwhile. You have the solar power to support much more and it would help to avoid the possibility of running the batteries down too low
 
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Yes, you can use a mains charger without disconnecting the solar panels. The only concern is without a solar controller (which I assume you do not have) if the mains charger charges to 100% SOC and then the solar panels output more than the load, the batteries will be overcharged.

Even if on average the solar input cannot keep up, it may exceed the output during daylight hours in some conditions.

Lead acid batteries are reasonably tolerant of overcharging, but it is something to watch.
 
If you have a separate starter battery, I can recommend one of these

EP Solar Duo-Battery Solar Charge Controller 12/24v 10A. £33.30

I had one handling my 40w of panels on my Snapdragon for several years. It was still going strong when I sold the boat. I set it up to charge the engine battery until full, then work on the domestic, on the basis that I could live with dim lights, but I really wanted to be able to start the engine.
 
noelex said:
Yes, you can use a mains charger without disconnecting the solar panels. The only concern is without a solar controller (which I assume you do not have) if the mains charger charges to 100% SOC and then the solar panels output more than the load, the batteries will be overcharged.

Even if on average the solar input cannot keep up, it may exceed the output during daylight hours in some conditions.

Lead acid batteries are reasonably tolerant of overcharging, but it is something to watch.
Click to expand...
Without a controller, the two Photonic Universe panels can kill the batteries on their own.
 
Of course at present in UK solar panels are not likely to do much damage to the battery especially if your load is regular. But if load comes off in summer yes you would need a controller to avert battery over charge. ol'will
 
Thanks everyone, that's really helpful. I have to confess, this isn't a boaty contraption. They power an Arduino and photocell, which raise and lower the door to the chicken coop each day. There's a constant 75mA draw from the Arduino and a DC-DC converter, plus a higher current for about 20 seconds each day. It was something my son put together for a school project a couple of years ago.

The coop is in a shady part of a North-facing garden in Cumbria, so the panels don't see much sun. But no, there's no regulator. I periodically stick a meter on the batteries and disconnect a panel if they go over about 14.5V. in the summer, it's fine with just 2 panels, and 3 in spring and autumn.

I probably should get a regulator though!

And yes, the charger is relatively new. It's a Ring smart charger. I can't remember which model though.
 
You could reduce the power the Arduino draws, and use it to stop any overcharging of batteries.
 
Avocet said:
Thanks everyone, that's really helpful. I have to confess, this isn't a boaty contraption. They power an Arduino and photocell, which raise and lower the door to the chicken coop each day. There's a constant 75mA draw from the Arduino and a DC-DC converter, plus a higher current for about 20 seconds each day. It was something my son put together for a school project a couple of years ago.

The coop is in a shady part of a North-facing garden in Cumbria, so the panels don't see much sun. But no, there's no regulator. I periodically stick a meter on the batteries and disconnect a panel if they go over about 14.5V. in the summer, it's fine with just 2 panels, and 3 in spring and autumn.

I probably should get a regulator though!

And yes, the charger is relatively new. It's a Ring smart charger. I can't remember which model though.
Click to expand...

There are solid state relays that detect battery level and then shut off charger when full ... reconnect charger when low ... cost ? less than a pint of beer.

Check out sites such as Banggood ... AQliExpress ... Amazon etc.

ie >

XH-M601 Batterieladesteuermodul 12V Intelligentes Ladegerät Leistungsregelungspanel Volle Leistungsabschaltung Überladeschutzplatine Ladungsentladungssteuerung

A cheap controller for the solar can be connected between your panels and the batterys ... both systems can live alongside each other ...
 
For goodness sake! Yet another arduino/photocell/chicken coop thread. I wish people would use the search function - this topic has been covered a thousand times before on this forum.

Seriously though, Avocet - I have a cheap n cheerful solar regulator you’re welcome to if you want it. Just pm me your address.
 
fredrussell said:
For goodness sake! Yet another arduino/photocell/chicken coop thread. I wish people would use the search function - this topic has been covered a thousand times before on this forum.

Seriously though, Avocet - I have a cheap n cheerful solar regulator you’re welcome to if you want it. Just pm me your address.
Click to expand...

Pal of mine is heavily into Arduino and Pi gear ... he sets up amazing stuff with them ...
 
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