CTEK MXS3.8 - Charge cycle never completes

[Art Vandelay]

Hi All,
This relates to the starter battery.
The MXS3.8 has a charging programme:
1 - Desulphation: maintenance aspect
2 - Soft Start: Tests if the battery can accept charge
3 - Bulk: Maximum current charge
4 - Absorption: declining current charge
5 - Analyse: Tests if battery can hold charge
6 - Float: Maintains voltage at max level
7 - Pulse: Keeps battery topped up at 95-100%

My issue.
My charger never reaches level 6. I'm pretty confident that the battery is fine - Varta, brand new last year and has been maintained properly since. I wonder whether it is due to the leisure batteries feeding off the starter battery meaning that, as they draw from the starter battery whilst being charged, this prevents the starter battery ever reaching 100%??
I've tested this by charging the leisure batteries to 100% (both new last year and correctly maintained) and then plugging in the CTEK to the starter....but I get the same result.

Anyone else have a similar experience?
Thanks

 

[AlanC]

Hi All,
This relates to the starter battery.
The MXS3.8 has a charging programme:
1 - Desulphation: maintenance aspect
2 - Soft Start: Tests if the battery can accept charge
3 - Bulk: Maximum current charge
4 - Absorption: declining current charge
5 - Analyse: Tests if battery can hold charge
6 - Float: Maintains voltage at max level
7 - Pulse: Keeps battery topped up at 95-100%

My issue.
My charger never reaches level 6. I'm pretty confident that the battery is fine - Varta, brand new last year and has been maintained properly since. I wonder whether it is due to the leisure batteries feeding off the starter battery meaning that, as they draw from the starter battery whilst being charged, this prevents the starter battery ever reaching 100%??
I've tested this by charging the leisure batteries to 100% (both new last year and correctly maintained) and then plugging in the CTEK to the starter....but I get the same result.

Anyone else have a similar experience?
Thanks

How long have you kept the charger connected to the battery?

Alan

 

[Art Vandelay]

@AlanC Currently been on for 40 hours. Will leave on for another 24.

 

[ArunAlec]

I’m sure @Loz will be along but I would not expect the leisure batteries to be able to draw from the starter battery. Apart from the debated “trickle” charge of the starter when on hookup the starter and leisure circuits should be independent.

 

[KGCali]

I have a CTEK charger and my Cali main battery charges fine, I usually leave it on 24 hours. I've only done this a couple of times as I find the inbuilt charger on EHU charges the main battery fine once the leisure batteries are fully charged, I do this every month on my Cali.
I've had a similar problem to yours on my wife's Mazda with the CTEK where the error indicator illuminates after stage 5 (battery can't hold charge). This only occurs when the battery is dead, she doesn't drive it much, then once the errors occurs I disconnect the charger for a few minutes and then reconnect it and it usually charges the battery fully on the 2nd or 3rd attempt after 24 hours. Hope that helps.

 

[Loz]

The leisure batteries won’t be charged as the split charge relay is controlled by the engine running signal from the BCU

what does happen though, I have observed, is that if you charge the starter battery over 80% certain systems come on and this drains it backdown to 80% at which point all system go back to sleep. So there is no point and no harm leaving the charger on the starter battery on charge.

 

[sidepod]

The charger unit has two separate outputs, one for leisure bats one for starter. It has to like this otherwise it would effectively bridge the split charge system. In other words the two batteries remain independent on hook up.

 

[Hyvast]

if you are on site for a long weekend and hooked up, then you charger will be in circuit all the time, so ho scan leaving it plugged in at home be harmful to the charger or the batteries?

 

[WelshGas]

if you are on site for a long weekend and hooked up, then you charger will be in circuit all the time, so ho scan leaving it plugged in at home be harmful to the charger or the batteries?

No. The built in charger is a “smart” charger and will regulate the charge.
The vehicle batteries like being charged.
Obviously you will be using some electricity but you could always use a Timer to switch the mains on periodically .

 

[Hyvast]

So those worried about leaving the charger on at home when the Cali is not being used, need not worry of the hook up was active for days on end

 

[yossarian]

Getting past stage 5 requires little to no current drawn from your battery. The charger sees the battery and any permanent loads (various ECUs, dashcam, lights, radio etc) as a "single unit".

A battery with permanent loads looks like a battery with a high self discharge to the charger.

If you want to check if quiescent current is the cause then disconnect one of the battery terminals from the vehicle and charge the battery directly on the terminals. Hopefully it will progress to the last stage.

 

[Wildcamper]

So those worried about leaving the charger on at home when the Cali is not being used, need not worry of the hook up was active for days on end

As said somewhere else, at home our van is permanently plugged in, leisure and vehicle, and has been for 3 years. The charge rate drops to under 1 amp and stays there.