Wiring the CTEK D250S

sfsmedic

Adventurer
I just purchased the CTEK D250S to start my dual battery install on my truck. I will add solar as well but that's down the road and 1 of the reasons I chose the D250S. I have a couple questions though that I can't seem to find a straight answer for. Vehicle install will be on a 2012 Tacoma with the house battery in the bed.

1 what size fuse am I running between the battery and D250s. I've read many places 50A, so that's what I am leaning towards.

2. Most the wiring diagrams I see have the wiring pretty straight forward but 2 places I saw commentary saying that with newer vehicles should use a relay between the d250s and alternator. Anyone else hear or do this or disregard it and their experiences would be great.

3. A couple diagrams show the positive coming off the alternator not the starter battery and some show positive off the battery. In reality it's the same thing isn't it since the alternator goes to the starter batter where the house battery and the starter battery positive cables connect anyhow right?

I attached the 3 diagrams I have below.

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Brett C.
IronworksTactical.com - owner
 

mib1392

Observer
No need for a relay. That's what the CTEK is about... plus the modified charging program.
I used it (old Volkswagen though) as in your 2nd graph and it worked out perfectly as it should. Charging current to the 2nd battery was about 15A (at around 14V) with running engine, so a fuse with 30A should be fine.


best,
Mike
 

sfsmedic

Adventurer
Didn't I already answer this some other place? ;)

Gotta spread the wealth? Lol. Also Check out the relay link below. Still has me baffled.

No need for a relay. That's what the CTEK is about... plus the modified charging program.


best,
Mike

Mike that's what I thought but I got the relay info off of CTEK (or maybe someone using cteks name for their site) site. Which was why I asked. Check out the link. Bottom right of the page.

http://www.ctek-chargers.com.au/ctek-d250s-dual.html


Brett C.
IronworksTactical.com - owner
 

4RunAmok

Explorer
This has already been answered elsewhere, but that relay is for applications where the alternator is variable or low voltage, and their fix is to let the Solar post of the CTEK D250S handle the voltage irregularities, like it's used to doing with a solar panel that experiences shade and clouds, etc.
 

sfsmedic

Adventurer
This has already been answered elsewhere, but that relay is for applications where the alternator is variable or low voltage, and their fix is to let the Solar post of the CTEK D250S handle the voltage irregularities, like it's used to doing with a solar panel that experiences shade and clouds, etc.

Thanks. On both places you answered.


Sent from my iPhone using Tapatalk
 

mib1392

Observer
I never heard of the relay option. And to be honest, the site doesn't look like a official CTEK rep. I'm quite confident with the "no-relay" option as I bought the Dual back then when it just came on the market, and did VERY extensive search to know if there are flaws and what the alternatives were (esp. with the IUoU charging line and a solar input). After quite extensive use (5 month road trip) the only thing I wasn't perfectly happy about is the 15A the normal Dual without Smartpass handles. I might buy another DCDC charger if I needed it again, such as Votronic (45A, but also double the price).
 

4RunAmok

Explorer
Most people will not need to use the relay in their installations.

Modern alternators are up to snuff. But some alternators out there don't pump out the required voltage for the D250S (low voltage alternators or variable voltage), so the Relay hooks the alternator to the solar post, and alternates between a solar panel and the alternator depending on the ignition state.
 

sfsmedic

Adventurer
1. 30A with the Ctek D250S or 50A if using smart pass.
2. No
3. Positive from starter batt.

Finally talked to someone at CTEK. They said you do not need an inline fuse between the battery and CTEK at all and it's recommended you don't use one. Kind of surprised me.

We ended up wiring positive from start battery to CTEK in bed (next to house battery) and house battery positive to CTEK as prescribed by CTEK. Then we earth grounded from frame to house battery and then to CTEK from house battery post. Couldn't see a reason to earth ground the CTEK on its own, just run off house battery ground post. The starter batter remained OEM setup for ground. Does anyone see an issue with the ground?


Brett C.
IronworksTactical.com - owner
 

4RunAmok

Explorer
Provided you cleaned the frame real well, maybe with a wire brush on a drill to remove paint and muck, your ground to the frame should be great. Some people even like to spray paint the connection after it's tightened to keep rust from forming.
 

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