Seldom used vehicles or those that may be laid up for weeks, months or more tend to present issues battery related and others all of which crop up on forums from time to time..

Just thought to add my own non expert experiences on the use of the CTEC chargers I have bought, in the off chance it might be found helpful. As ever, each to their own ideals.

I have a couple of CTEC chargers, the first I bought quite a number of years back, as the inhibitor/anti theft circuit retro fitted to my Old +8 would drain the battery over time if the Mog was not driven as regularly as it should have been... )-:

A few years back when I bought a more modern sports car which would also not be made regular use of, I bought a CTEC suitable for it`s AGM battery.

As best I understand it, seems CTEC advise not to leave the charger switched on and unattended until the light emitting diodes (LED`s) indicate that the charger has completed it`s cycle of charging at or around max output,after which it should have adjusted it`s output current down and into normal/ float charging mode, at which time it will maintain the battery voltage in readiness to start the machine.

The word float relative to charging a battery is that the charger via it`s internal sensing ability, will allow the voltage to fall to a predetermined level, at which time a very low level charge in fractions of an amp will then be applied by the charger to bring the voltage back up to fully charged state, thus the battery voltage and charger output are deemed to be floating between those two voltage parameters.

My Morgan has a CTEK MXS 3.6.... 3.6 being the max output in amps of the charger when initially connected to a battery requiring charge, creates a situation where the charger determines it`s max output might be required to bring it up to fully charged state in the shortest possible time relative to the chargers max output. When operating at max output the case of the charger will feel warm, whereas when operating in the float cycle the charger the case of the charger will be quite a bit cooler.

If the charger does not switch automatically into normal/flat mode :-

In the case of my CTEC MXS 3.6, 24 hrs, the battery and or the machine it is connected to while charging is in progress would seem to have issues..?

If possible, it might be thought worthwhile to disconnect the vehicles negative lead from the battery thus isolating the battery and charger circuit from any vehicle related electrical issues..

With the charger and battery together isolated from outside influences, if the charger fails to bring the battery up to normal within the advised period of time relative to charger type, then it would seem likely that the battery has an issue.

My more modern sports car having an AGM battery, I bought a CTEC MXS 5.0, which if you have been paying attention has a 5 amp max output... (-: It operates on the same principal as my older CTEC, but has the option to select AGM and RECONDITION options, the latter perhaps in an attempt to bring a long stored battery back up to a stage where it might provide it`s best possible output..?

I have to admit, that I have left both chargers permanently connected to my two cars for a period of years, fortunately without issue.. I monitor them from time to time, more so over Winter, and have not ever stood by when initially connecting the chargers to either of the batteries or others I have used the chargers on, until the chargers indicated normal/float mode had been arrived at, as advised in the chargers manuals.

I guess if you connect the chargers to a battery that has excessive internal losses due to age etc, there is a chance that the charger will be working at max and get quite warm, up to a point where the charger will reduce it`s output as it has temperature sensing built in.

CTEC advise that the charger is perhaps not left connected to the battery terminals IF the mains is switched off to the charger, as it seems that then the charger it`s self via it`s internal circuitry may become a load on the battery and discharge the battery over time... I live in an area where power cuts can occur though only out for a day or so at most, which to date has not upset either chargers the MXS 5.0 seems to hold the pre-sets I have selected and as best I can remember I think the older MXS 3.6 may require my preferred settings re-selected..