Mine’s on a Ctek all the time. But in general don’t leave a battery longer than two weeks as that’s about the time sulphation starts.
I have CTek chargers in both garages, and comfort connectors in all cars, so whichever cars are in the garages at any given time will be permanently on charge (only exception will be if I’m planning to drive the car again within the next couple of days).
I have a couple of A4 laminated “Remember to disconnect the trickle charger” notices which I place on the driver’s seat.
I thought CTek “smarts” had a de-sulphation cycle like the Optimate “smarts” do?
I have a Noco genius smart charger and leave it on all the time on the NB that sits in the garage all winter, the cable is hard wired to the battery all the time and the lead has an inline plug and socket, I just plug it in as soon as the car is put back in the garage, I have a high tech post-it tucked in the ashtray that says “warning disconnect battery” written in red pen. When I had my Spitfire and Alpine classics in the garage they each had a smart charger that I can’t remember the make of connected continuously.
Mine is connected to a CTEK whilst it’s in the garage.
You just leave them connected, they are smart so only charge if the battery drops.
Wish the lead was a bit longer, might have to buy the extension, as atm the CTEK has to be under the bonnet to reach the ND battery.
That’s why I prefer the Optimate. The charger unit is fully automatic and made to be wall mounted.
Optimate 4 for the 2015 ND SE-L and Optimate 5 for the 2019 ND 30AE because it has i-stop/i-loop.
Optimate indeed, i use two of them ; motrocycle and NA and they’re permanently connected to it.
Last battery i bought for the NA was in 2003, since then i used that Optimate and my battery is still in top-condition. Beside their effectiveness …it’s so cute to see them on their infuses waiting for a trip…
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Many modern battery chargers have a desulphation programme but whilst good isnt as good as not letting it happen in the first place.
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I was once told that you should always completely disconnect the battery from the car before putting it on charge or there was a real danger of damaging the electrical circuits of the car. Reading this thread it looks like I’m the only one still doing that. Mind you, the advice I had probably referred to the old non-SMART chargers. I had one of these until just last year.
I’ve only recently acquired a SMART charger, one of the cheap Lidl/Aldi ones admittedly, can I safely hook this up without disconnecting the battery from the car? It would sure make life a lot easier!
Apart from when I took our old MX off the road for the Winter I have never disconnected the battery.
…and yes I us an Aldi cheapie smart charger with the battery connected on both my cars.
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I think you answered your own question.
For what it’s worth, I tend to connect before switching on
For my sophisticated stop start BMW, I use the dedicated remote terminals.
The consensus here is to use the battery positive on our MX5s but to use a remote earth. This is less necessary on older versions with less sophisticated electronics but can’t do any harm, so seems a good general policy.
Similarly, removing the battery causes problems with systems having to relearn, so it would seem sensible to avoid it where possible and either top up with or leave a smart charger connected, whichever is more convenient.
My old (1990s vintage) Optimate said in the instructions to connect to the battery before plugging the charger into the mains. Newer ones I have don’t say this.
Back to the original question, I connect up about once a fortnight for two or three hours or so before starting the car and giving it a run to keep bushes moving etc. The idea being that it prevents deep discharge during starting. If the car was garaged I would leave the charger hooked up 100% of the time.
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I went to Halfords a few days ago, to collect some wiper blades for SWMBO’s Panda and they had a range of 3 different size solar panels. I think the biggest was only 40 quid or so. If I had street parking only, I would be looking seriously at this option.
The main problem with these though is connectivity.
Alas, the main problem is not enough sunlight in UK winter.
Been there, done it, and failed, simply because the 1 Ah per day of Mazda3 (or ND) dark current drain is more than the maybe 0.5 Ah of charge from the panel on a rare bright sunny winter day inside the clean windscreen, or a more usual 0.1 Ah on a dull overcast day with a dusty windscreen.
This was with a borrowed “10 Watt” panel after quickly giving up on my 2.5W Noco. The 10W panel was twice the area of the 2.5W but still only produced a miserable current - no risk of boiling the battery!
I used the OBDII connector inside the car, faced the car South and angled up the panel in the windscreen to maximise the insolation.
It would be a different matter in the tropics where the sun is a lot stronger and for longer.
The obd connection is a neat solution, is that your own idea or do they come with suitable connectors?
Its not only the strength of light that’s a problem in Winter but the duration of it as well, so solar power in Winter is a real problem.
It does seem to me though that even if there is not enough power to keep up with the drain, it might at least slow the rate of the drain, especially now both strength and duration of solar light are improving.
Yes, own idea after looking for a connector inside that remains live when ignition is switched off. There was a nice commercial lead with in-line fuse, but I cannot find it now, lots of others that might or might not be suitable.
OBD2 socket power only has a 10A fuse which feeds other essential stuff, so it is NOT suitable for a beefy battery charger, but a weedy Solar might be useful at putting off the evil day when a proper charger is applied under the bonnet.
Here is a previous post of what I tried in April with OBD2 pinout picture
and then in May
The borrowed charger was later and in the summer, but very disappointing so not worthy of a post.
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Excellent information, thanks 
I bought a CTEK MXS 5.0 for my ND2 for similar reasons. My rule of thumb ‘winter use’ tactic is to leave the battery on charge until the car gets used and then leave it off and then reconnect the charger again if car not used after 2 weeks or so.
Hi all, and many thanks for all the feedback…
I give ours an engine start and short (10 min) run every 2/3 weeks, and put it on charge every 10 days / 2 weeks. I have a multimeter and it normally drops to around 12 volts, and goes back up to around 13 volts after 2/3 hours on charge.
My understanding is that 12v is actually very low.
It might be worth getting your battery checked.