CTEK D250S

[Shaw]

Just ordered a ctek D250s
Just been reading up on the fitting of this charger could someone please confirm which is the proper way of fitting this unit iwas going to connect straight into the large cable under the passenger seat as photo butt on this fitting instruction it shows a relay http://ctek.com/sradmin/ARCHIVE/Support/dcdc_support/D250S_Dual_with_Smart_altenator.pdf
wher on the other it shows none http://ctek.com/sradmin/ARCHIVE/Support/dcdc_support/D250S_Dual_with_Charger_at_Service_battery.pdf
the charger will not have a solar panel used on it
if someone could please clarify this for me
Thanks Howard

 

[Pauly]

You dont need a relay if you are not using solar panels.
The battery connection on the D250S is not setup for vehicles with smart alternators as these can produce slightly higher voltages (circa 15V) so these types of vehicles should be connected to the solar panel connection instead as this will utilise the voltage regulating part of the charger to send the correct voltage to the 2nd battery.
The relay is only required if you have solar as well so you can connect both inputs to one terminal without connecting them directly together

 

[Shaw]

@Pauly Thanks alot

 

[Loz]

I wired mine using the second drawing for my power pack that connected to my Touareg with bluemotion and start stop and it worked just fine. So it's not too critical, it's a very capable unit.
Make sure the earth is chassis earth not directly to battery neg terminal.

 

[MartyMoose]

I'm going to offer a slightly different perspective on this. Ctek advise connecting to the PV terminal because it can accept a range of lower voltages, as produced by a smart alternator, and still give a constant 14.7v out for charging. The feeling is that the output from a smart alternator connected to the normal input of the 250S will be intermittent and too low to allow the charger to switch on (it needs to be greater than 13.1v for 5 seconds). The problem with the PV connection is the very fact that it does accept a lower voltage input, and so the relay is needed to stop the starter battery becoming the charging source when the ignition is off. It is in fact doing the job of the 'split charge relay' of olden times.

Having said all that, I have recently taken various voltage readings on my van. After starting the engine the voltage remains at 14.8v for a few minutes and then drops to 13.3v. In normal driving it is constantly ramping up and down between these two figures as I slow down and accelerate respectively. With the ignition off it drops to 12.8v. For this reason I think it is OK to connect to the normal Ctek input because the alternator output is always greater than the minimum switch on voltage of 13.1v. The Ctek does the rest and bumps it up to 14.7v to charge the leisure battery. You don't need a relay in that configuration because with the ignition off the input voltage is too low for the Ctek to switch on and so the starter and leisure batteries are isolated.

I am about to install a Ctek d250S myself, so will know soon enough if it works like this!

 

[Andy Cody]

I have the Ctek D250s connected up as per manufacturs guidance (input straight from the main van battery) and it seems to be functioning fine. Unfortunately I haven't got round to fitting a meter yet so couldn't tell you the figures but the lights change from standby to charging as they should.

 

[travelvolts]

I'm going to offer a slightly different perspective on this. Ctek advise connecting to the PV terminal because it can accept a range of lower voltages, as produced by a smart alternator, and still give a constant 14.7v out for charging. The feeling is that the output from a smart alternator connected to the normal input of the 250S will be intermittent and too low to allow the charger to switch on (it needs to be greater than 13.1v for 5 seconds). The problem with the PV connection is the very fact that it does accept a lower voltage input, and so the relay is needed to stop the starter battery becoming the charging source when the ignition is off. It is in fact doing the job of the 'split charge relay' of olden times.

Having said all that, I have recently taken various voltage readings on my van. After starting the engine the voltage remains at 14.8v for a few minutes and then drops to 13.3v. In normal driving it is constantly ramping up and down between these two figures as I slow down and accelerate respectively. With the ignition off it drops to 12.8v. For this reason I think it is OK to connect to the normal Ctek input because the alternator output is always greater than the minimum switch on voltage of 13.1v. The Ctek does the rest and bumps it up to 14.7v to charge the leisure battery. You don't need a relay in that configuration because with the ignition off the input voltage is too low for the Ctek to switch on and so the starter and leisure batteries are isolated.

I am about to install a Ctek d250S myself, so will know soon enough if it works like this!

Unless I am very much mistaken the charging voltage of the Dual is 14.4 and not 14.7. Also, I don't think that the MPPT input is designed for voltages much lower than 12 either as this would put too much demand on the panel in terms of current. I do think that the MPPT input is used for IAs though because it can make the most of the varying output voltage from the alternator. In this respect I think the Ctek looses out to other B2B chargers and it's time that they pulled their finger out and updated the software in the Dual.

 

[MartyMoose]

You are right @travelvolts, it is 14.4v not 14.7v as I stated. Slip of the pen on my part. The original post was asking whether a relay was needed if connecting to the PV terminal and I was trying to offer some constructive advice as to why it was. Ctek don't say what the minimum input on the PV needs to be, and I wasn't implying it would be less than 12v, only that it would happily accept the 12.8v (or so) from the starter battery and use it to charge the leisure battery (if you didn'the use a relay). The voltage readings I have taken obviously relate to a VW T6 smart alternator and these indicate that connection to the normal input of ctek d250 should, in my opinion, be perfectly acceptable. Others on this forum have connected it so and had no problems. Other smart alternators may have different output ranges and I wonder if Ctek are just hedging there bets by advising as they do. Unfortunately the technical specifications available from Ctek are limited and so we can only make informed opinions based on what they are willing to share with us.

I have also looked into the Sterling b2b charger and I don't they have done much to address the issue of smart alternators either. They use an adjustable timer to keep the charger going when the alternator voltage drops, but as far as I can tell this has always been a feature on their products, and not something specifically intended for smart alternators. They all need to get their fingers out; the future is already here!

 

[travelvolts]

As far as I know all b2b chargers have a timer that allows harvesting from the vehicle battery once the engine stops. However, the main charging is achieved by pulling the vehicle battery voltage down. This prevents the alternator from shutting down as it thinks that the vehicle is running a heavy consumer like AC. Without interfacing the vehicles ecu, and I think that we are a long way off that, I can't see how else it can be done. I have spoken with CTEK about this on numerous occasions and you are right, they are not very forthcoming and extremely protective of their tech people.

 

[Andy Cody]

It's an interesting point MartyMoose makes about the running voltage not dropping below 13.3v as I'd much prefer to keep the two inputs separate if possible to avoid having to use a relay.
I'm yet to install a solar panel so am currently charging via the alternator only (via the normal port) but thinking about it, I've not seen the green light to show that the leisure battery (Xplorer 110ah from Travelvolts) has been fully charged yet. I've been doing the odd 30 minute / 1 hour drive in between running the Erberspacher for around 20 minutes so maybe I'm not doing decent enough journeys to give it a full top up?

Also, without hijacking the thread, I noticed on a cold evening that the leisure battery sides were dripping with what I can only assume was condensation. Is this normal? Plus I've only installed a vent tube to one side of the battery (only one supplied). Do I need to blank the other side?

 

[travelvolts]

Hi Andy, you should connect your input on the Dual to the solar connection. It is normal to get some condensation on your battery. Have you sealed the unused vent hole? If not use a piece of blue tack or similar.

 

[Keeff]

I don't have any charging equipment on mine but do have a volt meter and mine can drop as low as 12.2 volts with the engine running . It never drops below 13.2 volts if the lights are on . When I lift off the throttle it goes up to 15 volts or first few miles in the morning . I wish they could run like this all the time with the lights on because the standard lights are better when the volts are up to 15 v .

 

[Andy Cody]

Hi Andy, you should connect your input on the Dual to the solar connection. It is normal to get some condensation on your battery. Have you sealed the unused vent hole? If not use a piece of blue tack or similar.

Thanks Martyn. I'll try connecting it to the solar MPPT port then.
Looks like I'll need to run a switched live and relay ready for when I install the solar panel then.
I'll blank up the other vent hole while I'm at it.
I'm concerned the battery condensation will run down into my floor pan and corrode the earth connection and wondering if I should keep the battery in a bag or get a jacket to stop a puddle forming.

 

[MartyMoose]

Andy, just to reitterate, if you connect to the PV port direct from your main battery, you must go through a relay so the Ctek is only connected with ignition on. If you don't then you will flatten or deplete your main battery. It might not be now when your leisure battery is nicely charged but maybe after you've been parked up for a while with a few 12v devices running. This is not the time of year to have a weak starter battery.

Apologies if I'm preaching to the converted but it's sometimes difficult to get a feel for people's understanding from just a few lines of text. All the best.

 

[Pauly]

Just reread the posts and @MartyMoose is right, connecting the feed to solar with no relay will put a draw on the start battery.
FWIW i have mine connected with no solar to regular battery terminal and seems to work fine, have been thinking about getting it changed over but not got around to it yet

 

[travelvolts]

Andy, just to reitterate, if you connect to the PV port direct from your main battery, you must go through a relay so the Ctek is only connected with ignition on. If you don't then you will flatten or deplete your main battery. It might not be now when your leisure battery is nicely charged but maybe after you've been parked up for a while with a few 12v devices running. This is not the time of year to have a weak starter battery.

Apologies if I'm preaching to the converted but it's sometimes difficult to get a feel for people's understanding from just a few lines of text. All the best.

My apologies, I have should have made this clear when I suggested it. This is covered in the instructions supplied with the unit but I should have explained it better for other forum users not purchasing from Travelvolts.