Smart charger

Rockingrabbit gurgled happily, sounding much like they were saying:

If the battery is disconnected, there's no reason why it needs to have the charge maintained - I leave cars sat like that over winters, with no problems starting again come spring. In the past, I've even skipped a summer with no problems.

'course, there's also no rational reason to isolate the garage power...

The C-tek smart charger does exactly what you ask, if it is left connected to the battery then the charging will recommence when the mains power comes back on. I bought mine from costco at about 35 quid (not there at present I believe), car shops sell them for 50, I believe (some one else, like Dave P will know) that the lidl/aldi ones are just the same and only about 12 quid, but they are not always in stock, just occasionally, sign up for their specials newsletter and you can get to know in advance.

With a smart charger (or any charger afaik) there is no need to disconnect anything.

I can think of a few.

Willy Eckerslyke gurgled happily, sounding much like they were saying:

Do they all involve dangerously shonky wiring?

No. Use your imagination - unattended outbuilding, owner on hols, nice supply of free electricity...

Start and charge boost chargers and modern Man trucks really don't get on well, it's quicker to disconnect & reconnect the battery than wait for the list offaultwarnings to clear on the dashboard. Butunless you're using something gratuitous I'd agree.

yes, I was really thinking car maintenance, and real BFO chargers are not too domestic. I have got a wheel about starter charger, but I haven't used it in anger in years and years. The last truck I worked on was a TK Bedford, about as simple as they get !! I was walking past a transport yard the other day and saw a guy in clean overalls!, using a laptop! to talk to a big truck, and I thought: What has it all come to? Where are the big boots, thick grease, missing teeth, big adjustable, and sledgehammer that I remember from my youth?

Oh you still need those as well :-)

Machine mart sell a range of smart chargers

The Lidl one does need a button pressing to get it started after powering up.

I think there's a fundamental reason for this. Most need battery volts - even low - to determine the polarity is correct before allowing you to actually start the thing charging. This part of the circuit consumes power and would flatten a battery (over a period) if it remained in circuit with no mains present. Disconnecting the mains effectively disconnects the charger from the battery.

I have one of these permanently fitted to the old Rover, with a waterproof mains socket for the mains lead. It would have been convenient to have it start up as soon as it was plugged in, but so far haven't worked out a method of doing this. Although running the mains lead out to it takes longer than opening the hatch, lifting the boot floor to access the spare wheel well, and pressing the button a couple of times.

aah, so now we know a fundamental difference between the lidl ones and the c-tek.

Thanks for all the thoughts on this. There are plenty of C-tek chargers on ebay.

Yes I do agree that there is no big problem leaving the power to the garage switched on. Wiring is recent and modern and done properly, but wife is a little nervous about leaving anything left on.

I did start by leaving car connected to battery (Mondeo) but as we all know the small current being drawn takes the battery volts down over a few weeks. Still started fine (in Summer) but I do not like battery falling below 12.4 Volts minimum. It went as low as 12.1 Volts a few weeks ago so probably sulfated. It is 10 years old and appears to be original Ford battery.

Rockingrabbit gurgled happily, sounding much like they were saying:

So well overdue for replacement, then. How much were you intending to spend on this charger, when a new battery from any of several suppliers on the web is less than £50?

my one is a ctek Zaphire 90 with 3.3a max current.

Think the volts have to go much lower than 12.1 for sulphation to occur.

The batteries on Fords equipped with Smart Charge often last this long or more.

The OP leaves his vehicle unused for "many weeks at a time", so the best way to prolong battery life is by keeping it fully charged.

Chris

If the C-Tek is this one, which appears to fulfil the need of charging when mains is applied with no button pushing :-

The Lidl one gives approx 5 amps so an overnight charge will be sufficient for most conditions. And is also a maintenance charger. At a third of the price.

I've had a Gunsen one for years. It has automatic/manual and 100% charge/float modes. No buttons to press. Several on eBay, for example: