Battery chargers

[Winnie]

And this mxs3. 8 should be okay to leave plugged in for extended periods of time?

[the evil twin]

And this mxs3. 8 should be okay to leave plugged in for extended periods of time?

The first CTEK I commissioned was well over 5 years ago (XS 0.8).
Been running 24/7 ever since, still has the original batteries in it (twin 28 AH sealed)
Specifically MXS 3.8, maybe 3-4 years ago
Have yet to see one crap itself

[bazzaboy]

As others have said, what about a small solar panel? I have two small panels, I think their about 7-8 amps each. One panel is connected to my wife's car, which only gets used about once a week, and the other is on my patrol connected to the start battery. Works perfectly and ensures that both vehicles will start when needed. If the patrol is needed for a trip, I stick my 40amp smart charger on the start & second batteries to get them fully charged before heading off.
IMO doing it this way will ensure maximum battery life expectancy.

[dom14]

Hi Dom,
I was pretty sure someone would post what you have in reply to what I wrote. It is what I would have expected too, but my experience suggests different.

I have learned over the years that there are smart chargers & smart chargers! Not all work the same. ’Smart’ can mean different things.

All smart chargers will be multi stage chargers, & it is not unusual to see the term smart charger used to just mean multi stage charger. All should when fully charged drop into float mode, generally providing a constant voltage between 13.3v & 13.8v (with a 12v charger) with little to no current

Most will have a voltage threshold below which the charger will switch back into bulk charging mode. Some will drop back into float mode when a voltage threshold is reached. Some will just remain in bulk charging mode for a set period of time. This runs a risk of overcharging.

The 7 amp ctek I had automatically changed from float to bulk every 10 days regardless of battery voltage. This would have been ok if the battery capacity had matched the charger, but as the charger was too small somehow the charger always thought that the batteries needed charge & if left in float mode would have overcharged them. Essentially the charger was ’too smart’.

If the ctek was left connected to my batteries when the vehicle was outside the solar regulator would periodically show a high voltage disconnect error, whilst still logging the battery voltage from the ctek. On occasions this would rise to as much as 16.1v leading to concern about the possibility of thermal runaway & even fire. This was a result of mismatched charger to battery capacity. I can’t recall more specific details, but had correspondence with Ctek at the time & am confident the charger was not faulty. They suggested I test it on just one of the 150ah batteries (instead of the two of them together) & there was no problem. Together 300Ah was a different story. I had expected that a smaller charger would just take longer to charge them, but there is clearly more to it than that.

Hi Cuppa,
Yeah, I agree. Makers of smart chargers can muck around with the meaning of "smart charging".
Yeah, I meant it as a multi-stage charger, preferably controlled by a microprocessor, otherwise it wouldn't be that much of a smart charging.
Ideally, smart charger should take the battery voltage into account and adjust it's output accordingly.
It's suppose to do that at the time you connect the charger to the battery.
If the smart charger doesn't do that and relies on an internal timer to dictate the bulk, adsorption and float charge stages, then it can't be that smart.
Let's say you have a battery that is 98% charged. And you connect your "smart charger" and it immediately charges that battery on bulk stage. And that can't be good and bound to end up overcharging the battery.

The idea of "smart charging" is that it has to be smarter than alternator regulator.
Alternator never overcharges a battery, 'cos the regulator does the job of taking the input from the battery voltage and
adjusts the output voltage(or amps) of the alternator.
The only thing alternator does not have is the so called "smart charging" capacity to charge a battery to 100%, 'cos the smart charging process break down the charging process to stages to suit the battery chemistry, which is an average alternator(unless it's a smart alternator controlled by a dedicated microprocessor or the ECU) can't do.

So the microprocessor in the smart charger must take the battery voltage into account and adjust it's float charge accordingly, effectively preventing the battery from overcharging.
If the so called smart charger can't do that and solely rely on an internal timer to regulate the stages of smart charging, then IMO, if I'm correct, it's no smart charger at all. On the contrary, as in your case it can end up cooking the battery.

If you can't leave your smart charger plugged into the battery all the time and it kills the battery by overcharging it(regardless of batter AH rating), then I think it's a good idea to be really careful about leaving them plugged in all the time.
Even though I agree with "smart charging process" in principle, I'm still suspicious of the smart chargers that they might end up cooking the battery. Hence the reason I don't leave my three stage smart charger(20A) connected to the battery for too long(definitely won't leave it plugged indefinitely).

So, if your 7amp Ctek smart charger switches to bulk stage every ten days(regardless of the battery SOC), then IMO it's not a smart charger and should be careful with using it as a full time plugged in smart charger.

I'm not that all aware of the different Ctek chargers(with different amp setting) for different AH batteries.
I thought, the charger should ideally adjust the charging process to different AH rating batteries.

I also have trouble with the idea of smart charging with 3.xx A rating smart chargers.
My smart charger is rated 20A, which means at bulk(or boost) stage it can allow 20A maximum current.
A smart charger with 1 - 3A maximum during bulk stage, doesn't look all that bulk( or boost) to me.
In other words, it may be missing the boost stage of smart charging altogether.

[Winnie]

Update... so in the end I got the CTEK MXS3.8
When I plugged it in the other day, it jumped straight to charging stage 3 and pulled the Redarc in not long after that so both batteries are charging and I'm happy with that.

[dom14]

Update... so in the end I got the CTEK MXS3.8
When I plugged it in the other day, it jumped straight to charging stage 3 and pulled the Redarc in not long after that so both batteries are charging and I'm happy with that.

Sounds like it comes with electronics to assess the battery SOC the moment you plug it and it chooses the charge state accordingly.
Microcontroler controlled smart charger, by the sound of it?