12v gel cell - maintainer module?

[Paul Drawmer]

I'm putting together a backup power supply for my router and fibre termination. When we get a power cut, the phone is dead, and mobile coverage is rubbish here.

What I'm looking for is a 240 battery maintenance module to automatically look after the 24Ah gel cell that's going in the box. There are several free standing units on the market, but I want just the electrics on a board that I can incorporate in the box.

I don't need uninterruptible power, so I can build myself something with a decent reserve, that just needs switching over from mains to battery. Switching back to mains power will let the charger module revert to looking after the gell cell.

[biggiles]

This is a car forum, so the obvious answer is something from CTEK or Optimate perhaps?

I solved the problem in a different way, using one of these off the shelf: https://www.amazon.co.uk/gp/product/B08FBB4Q8V - it works well, keeps the internet/phone working through power cuts.

And I also have some usb-c-to-12v leads, so can use any of the powerbanks littered around the house (or a car) to power any other equipment.

[Griffith4ever]

Couple of points:

1) If you use a CTEK/Lidl/Aldo battery charger you won't need it to "hand-off" in the event of a power cut - it'll just stop charging. I'm guessing you want to use the battery to direct power your router and modem, bypassing their own 12v PSUs? The CTEK idea is solid. It'll still be charging your battery (trickle) all teh time, which does no harm. Do make sure whichever you buy will auto resume after power loss - the Lidle ones usually don't.

2)You can get a wee UPS for £50 on amazon. Why re-invent the wheel? I have one, slightly larger (£110) whcih powers my router and my NAS RAID. It also powers my PC and monitor, but the £50 jobbies will run your modem and router all day long.

[Paul Drawmer]

I have an old Optimate, what I'm looking for is basically, just the board from that.

My router and fibre termination together draw about 1.5amp at 12 volt. So most affordable UPS boxes would die pretty quickly. I'm not reinventing the wheel, I'm swapping the uninterruptible for more hours. The gel cell is 24Ah.

[Griffith4ever]

Fair enough, but even this low voltage UPS is good for about 4 hours powering a router:

https://www.amazon.co.uk/dp/B09VCJF97Q?ref=emc_s_m...

Only 8.8Ah.

I'd buy that, then open it up and use it as the mainboard - connect it to your 24Ah battery instead of its inbuilt one. Saying that, its using a Lithium battery so the charging would be wrong for your gel... but you get the idea.

In fact, why not get a leisure battery, 110Ah - you could run of it for ages! Then get one of the below to charge it. I have one - it auto resumes after a power cut.

https://www.amazon.co.uk/Aibeau-Maintainer-Automat...

[OutInTheShed]

A lot of burglar alarms and the like will simply have a 13.8V power supply which float charges a sealed lead-acid battery.
Such PSUsare abundant on ebay
Not all lead-acid batteries are the same, you should check the float charging voltage.
Too high a voltage will kill the battery.
A float voltage will take a long time (days) to recharge the battery.
So a smart charger like a Ctek can be a better idea.

I'm not aware of any pcb level modules worth considering.
I'm aware of certain products with LA batteries in, where the product's microprocessor also controls some rudimentary smart charging.

I have an old car battery in the garage on float charge permanently, the charger is a wall-wart style, made by a small firm in England.
Not sure they still do them, the market is swamped with stuff from China of varying quality. In theory I'd use that battery for the router in a power cut, but I've not needed to.

[tr7v8]

That seems a lot of work when a little UPS will do the same for little cost.

[OutInTheShed]

tr7v8 said:

That seems a lot of work when a little UPS will do the same for little cost.

Fair comment that there are some good little UPS devices about at sensible prices.

You need to decide what you want to achieve.
I happen to have a battery which came out of a car, it has lost some oomph, but will still power a few things.
I had the charger spare, left over from when I had another vehicle.
It's a setup I use for testing anything 12V.

For some people it would be worth spending a bit more money.
Maybe you want to store enough energy to recharge a few phones, tablets, laptops?
Run a few 12V lights?
Power the fridge from an inverter?
Survive a longer outage?
Maybe your wifi network is a mesh with a few units eating power?
The small powerbank things don't have too many watt-hours in them.

Personally, if we had long power cuts, I'd need light in the shed for long enough for me to strip the carb on the generator as it hasn't been started for ages...Or I could cycle to the boat, which is obviously off grid....

But my experience has been more outages of internet than power, so it's not really a priority to even spend £50 on.

But I've been looking at Lithium batteries to run a portable fridge outdoors, which is thread drift....