12v LED lights/Lead acid battery help

[Outofphase]

Hello all, this is my first post so please don't grill me too soon

So I've finally got mains in my shed after a few years of using 12v lighting and rolling the extension lead out when required. For a year or two, I have been running 6 x 4.5w LED clusters as main lights using a pair of 12v 17ah Sealed lead acid batteries in parallel. I disconnect and charge the batteries individally on a dedicated 2A charger.

However, since I now have mains (but still want my batteries as backup), I want a way to charge my batteries in-situ. From what I read online, a regulated 13.8v supply can be left indefinitely on a 12v SLA to keep it topped up. I could easily make up a 230v - 13.8vdc supply but I don't want a shed full of hydrogen if I leave it on too long

Another idea was to have a 12v power supply and a DPDT switch to select between battery and 'mains' power. I would still have to charge my batteries, just not as often.

I have a good understanding of this kind of thing, but a little guidance wouldn't hurt

Would a constant 13.8v supply to the batteries kill them?

 

[Pat H]

Bung a solar panel on the roof with a charger and let that do the job.

 

[Outofphase]

Cheers Pat. I did look at solar panels a while ago, but my shed is under a shaded area and wouldn't get the sunlight too well. I don't mean to reject the idea, I would just rather go for the dependability of a mains-powered device.

 

[Pat H]

Then I'd look at one of the smart chargers designed for longer term battery charging.

Automatic Electronic Car Battery Charger 4A Fast/Trickle/Pulse Modes 4 AMP | eBay - http://www.ebay.co.uk/itm/Automatic-Electronic-Car-Battery-Charger-4A-Fast-Trickle-Pulse-Modes-4-AMP-/322354687132?hash=item4b0dd62c9c:g:meUAAOSwnHZYSsIX

 

[Outofphase]

I should've mentioned I would like to be able to fit it into a small enclosure (188x120x53 to be precise) and be able to turn it on/off using a toggle switch. I'm trying to keep it diy. Would the 13.8v power supply be a bad idea? I found a lot of chargers switch to 13.8v once the battery is charged. I have a variable DC power supply circuit already, just need reassurance that I won't blow anything up by leaving it on my batteries.

 

[HandySparks]

Would a constant 13.8v supply to the batteries kill them?

Worth checking the manufacturer's data sheet for the batteries in question. It should say what the recommended long term trickle charge voltage is. After all, there are quite a few devices which stay permanently on charge (eg alarm systems).

 

[Outofphase]

http://www.bb-battery.com/productpages/BP/BP17-12.pdf
http://www.bb-battery.com/productpages/BP/BP17-12.pdf
It doesn't seem to say anything about charging, only discharge I'm afraid.

 

[UKMeterman]

Have a look here for the info,
Battery Shop Online Data Sheets - http://www.batteryshoponline.co.uk/data-sheets-4-w.asp
Batteries from them or Electronic Components from Rapid - the Electronic Parts Specialist | Rapid Online - https://www.rapidonline.com
Charger eneloop Rechargeable Batteries, Smart Battery Chargers, Jump starters Tantronics - https://www.tantronics.co.uk/index.php/
Do get a charger for SLA batteries, they are a little picky about float voltages.