CTEK D250SE intermittent charging from alternator

[BobMcBob]

Hi, first post. I hope it's OK to post here, I have a T5 but there seem to be several split charge experts on here and I've not been able to find any help anywhere else, CTEK haven't even replied to me.

So I have a C250SE that has been working fine since I installed it 3 years ago. My solar isn't permanently connected, but this has never been a problem and CTEK told me it was fine to do it that way. This week however I did a 3 hour journey with the fridge running - something I've done plenty of times before. When I arrived at my destination though, my leisure battery (NDS Green Power AGM) was reading 12.4V and the CTEK was in "power saving mode". The starter battery was at 13V. (Note, the T5 doesn't have a smart alternator).

After checking the voltages across the terminals on the CTEK and verifying they agreed with the voltages across the battery terminals I started then engine again. The lights came on to indicate the leisure battery was being charged from the alternator. The voltage across the starter battery from the alternator was 14.5V. Then the lights went out. About 15 seconds later they came on again for about 2 seconds. This on-off then continued until I switched the engine off.

I connected the solar panel and this charged the leisure battery fully, then by evening it was trickle charging the starter battery. So all the connections seem fine.

On my return journey I checked the lights again about 5 minutes in and they indicated charging from the alternator, but when I arrived home once again the leisure battery was at 12.4V and the CTEK was in power saving mode.

There does appear to be a problem somewhere but I'm at a complete loss. I've read a lot of posts about blown fuses and diodes inside the CTEK but my symptoms don't quite match. I'm starting to suspect the alternator but that's only a year old. I'd be very grateful for any help.

 

[Dellmassive]

got a few pics of the unit, connections and so pics of the voltages with the engine running & off.

well see if we can help out

 

[Dellmassive]

my unit . . .

[Guide] DC-DC Charger (for leisure battery) -- How I Done It --

Thanks Lee. Or should I say Mr. Renogy! Been looking at your threads so will work out how to do it all now. Thanks bud.

www.t6forum.com

.

 

[BobMcBob]

Thanks for the reply and the pics. I can't get any photos of mine right now but I have learned 2 things:

I've used cheap ring connectors and maxi blade fuses. Although it has been working fine for 3 years, it seems to me my cabling might be suspect, so I'm going to renew it using better quality parts (I re-used an existing cable when I did the initial install).

I put a multimeter across the terminals (alternator input and negative) on the CTEK and started the engine. The voltage was 14.5V. The alternator light on the CTEK came on. Voltage still 14.5V. Then the charging light for the leisure battery came on and the voltage dropped rapidly - it took about 2 seconds and then it must have dropped below the kick-in threshold for the CTEK because it stopped charging and went to sleep mode.

So - the extra current being pulled by the CTEK is causing the input voltage to drop off rapidly but not immediately. I know the starter battery is old and should really be replaced (it died over the winter and I had to jump start the van twice) so I'll do that and I'll renew the cabling while I'm at it. If it's not that then I guess it must be the alternator?

 

[Sim60]

Does your T5 have stop/start and a smart alternator? I think the later ones do - in which case you need to have the smart alternator I/p on the CTEK wired up to an ignition signal which will force the CTEK to charge the LB even when the alternator output voltage drops

 

[BobMcBob]

It definitely doesn't have stop/start, and this setup used to work until recently. It is a new alternator though, so I should check they fitted the right one... anybody know if there's an easy visual way to tell?

 

[Sim60]

CTEK spec is to cut out if input is <12.8 V for more than 10sec in conventional alternator setup

 

[dubLU]

Are you still having issues?
If so you might want to follow these steps as your symptoms are the same as mine were. I had this explained to me by an amp maker who came to my rescue via a friend
Although you are reading voltage at the ALT input and although ctek led's are indicating some ALT activity you must check the internal fuse on the ctek. It is the corner fuse which is by itself. Circuit wise it fuses the high amp stuff that goes on, however ALT activity like the reverse trickle charge will still appear to be operating as the ALT led does show some illumination.
If the fuse has blown and you can see some burned area or other signs that other components have been taken out you might need a pro repair / new unit. If its clean then the following may work.
I nibbled of the plastic from the fuse leaving the two metal legs exposed. A fuse holder with flying leads can then be spade connected onto these legs. I cable tied it down
The midi fuse by the battery is 30amp and this internal fuse is 30amp, As midi fuses have a higher tolerance to spikes than blade fuses I think this is why the 30amp internal fuse blew.
I have replace the engine bay 30amp midi with a 25amp midi hoping that fries before the internal fuse. The 25amp midi fuse has blown once this season, but at least its a quick change.

 

[BobMcBob]

Thanks for that it's helpful. I haven't had much of a chance to look at it recently but that definitely gives me the best starting point when I get time.

 

[dubLU]

Cool, keep us informed.

 

[BobMcBob]

One thing I did notice the other day - normally when I disconnect the solar panel the charging lights stay on for some time afterwards (presumably while the CTEK is using up the stored charge?) but now when I do it the lights go out immediately. From your description, the sudden voltage drop, and this evidence I'd guess there's a short somewhere. The battery is holding charge so I guess this points to be CTEK as the culprit?

 

[dubLU]

M solar has always worked well but like you I have different ctek led behaviours. Even this week it has started doing things a little differently. Before you undertake the extraction of the ctek to check internal fuse, I would first check the fuse on the switched live piggy back which should be in the fuse board in the passenger footwell area, if thats OK check there is a switched live signal where it connects to the ctek switched live 12v input, you may have to break the connection if its a splice crimp, replace them with bullet crimp or spades. If fuse OK and switch 12v is present at the ctek then extraction and internal fuse inspection is your option.
I'll dig some photo's out and post here.

 

[BobMcBob]

Finally got the van back from its annual service (takes longer every year ). I asked them to fit a new starter battery and well, it seems to have fixed the problem. Ran the engine for 2 minutes and the charging lights stayed on, voltage across the CTEK was roughly 13.8V throughout.

 

[dubLU]

What a brucey bonus, congrats.

Maybe still consider putting a 25amp midi fuse at the starter battery side midi-fuse holder, will offer some protection for the internal alternator IN fuse. Will save you a ton of ball ache replacing the internal fuse i(f your lucky enough to only blow the fuse and not the many components around it) and is easy to replace.