Hi

 

I have a Skoda Superb 2.0 SE TDI 4x4 CR Estate MK2 170 hp / 125 kW Diesel Car, date of reg:16/03/2015. It has the stop start feature, so I'm guessing it has variable voltage (smart) alternator, can anyone confirm this?

 

I need to know because I tow a caravan and I'm switching to a Lithium Leisure battery and from what I have read if the car does have one of these fitted there is a risk of charging with the wrong voltage when towing, so I would need to fit a battery-to-battery charger installed. Also I think there is a risk of overcharging the battery.

 

Source of Lithium leasure battery info is here.

 

Thanks

 

Mark

Welcome to the forum Mark,

 

For a few years, the Alternator will not work at 100% all of the time.  They battery tries to maintain about 80% SOC (State of Charge) roughly iirc, and allows a little headroom of energy to be input on overrun.

Even without the stop start, mine sits at 14-ish for a while until it thinks it's replaced the starting energy then drops back to 13.6 for the rest of the trip.  That's IMO too low, I'd prefer 13.8 or so for the lead-acid-calcium battery.  If you've got an AGM I'd want even higher.  They keep the voltage low for an emissions reduction thing (less alternator load = less fuel = fewer emissions).   I don't know of the stop-start models have brake-energy-recuperation; I suspect that came in with the MQB platform.

 

You'll want a DC-DC charger regardless of 'smart' alternator or not and they're pretty inexpensive these days considering the improvement in charging times they offer.

 

You'd also be advised to run better wiring from the main fuse box under the bonnet to your caravan.  Here in AU we tend to run large cables to an 'Anderson' plug at the rear bumper for charging van house batteries.  Not sure what is typical in EU but having seen the wiring in the OEM trailer loom I'm not satisfied it can supply much current without significant voltage drop, further emphasising the need for a DC-DC charger.

It is not too low, 13.3 volts is sufficient, 13.0 volts will maintain battery charge against a moderate electrical load, higher voltages will recharge a depleted battery quicker, that is why you are seeing the initial 14 volts dropping back, it has indeed replaced the energy lost when starting, these vehicles have tremendously powerfull alternators, don't believe the old wives tales of needing a 20 minute drive, your charging voltage is the proof, once recharged the voltage settles at the level required to balance the electrical discharge, this will vary.

 

If you do not believe me then measure the voltage from a battery charger on fast charge, slow charge and maintenance charge.