Question about CTEK D250S install for dual battery and solar.

Brett C

Adventurist
Senior Staff
Moderator
Hope this is in the right place.

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


Brett C.
IronworksTactical.com - owner
 
Page says its a 20A charge. No idea if that is max or only while on solar. Couldn't easily find a factory wiring diagram.
 
Point 1) The Charge Current of the D250S is 20 amps. I would use a 25 or 30 Amp Maxi fuse or breaker, I'm partial to breakers.

Point 2) I'm pretty sure the D250S is made for the solar to go to the Solar Post, the Main Battery/Alternator to the post below it, and the Aux Battery to the post on the lower right.

In that first diagram. When the ignition is off, the relay is connecting the solar panel to the common post on the relay (which is connected to the Solar post on the D250S), when the ignition is on, it's connecting the Main Battery/Alternator to the common post. Thus isolating the two charging sources.

I'm pretty sure the D250S is taking care of that isolation internally. In fact, going without the relay will allow the internal solar controller to charge both batteries, the way it's designed to do.

Point 3) In reality, yes, it's the same. Your alternator connects to your main battery through the fuse block in the engine compartment via it's own fusible link. You connecting to the post at the battery, at the post where the fusible link is, or at the alternator itself is of little difference. Do whichever is easiest.
 
Ahhh, I get it now..

Notice the note to the right of the image that you posted from their site; VARIABLE, or LOW VOLTAGE alternators.

Basically, the Solar post on the CTEK is capable of handling low and variable voltages, like those that come from solar panels that are prone to voltage inconsistencies due to shading, clouds, etc.

If you have an older alternator without voltage regulation (making it variable) or that might feed less than 13 volts, you might have to go with this relay method. The Solar post on the CTEK will manage this erratic power supply.

If on the other hand, you have a modern and stronger alternator, just stick with the Alternator post.

EDIT: I should add that if I found myself in that situation, like I am currently with the weak 4Runner alternator, I would head out to an alternator shop and invest in an upgraded alternator. What's happening to me right now is my Automatic Charging Relay is disconnecting my batteries when I'm at idle for longer than 10 seconds, because my charging voltage from my alternator is dropping below 13.1 volts. So I'm bartering a deal (since I don't have all the cash) with a local alternator guy to get me a new alternator (14.4 volt, 120 Amp) and this will stop happening.
 
So since I have a new alternator in my 2012 Tacoma I wouldn't go that route. Also that explanation makes sense. Thanks.


Brett C.
IronworksTactical.com - owner
 
Now to try to find some reading to understand batteries. Ugh. Need to figure out what I'll be using for my house battery so I make the correct purchase.


Sent from my iPhone using Tapatalk
 
Ahhh, I get it now..

Notice the note to the right of the image that you posted from their site; VARIABLE, or LOW VOLTAGE alternators.

Basically, the Solar post on the CTEK is capable of handling low and variable voltages, like those that come from solar panels that are prone to voltage inconsistencies due to shading, clouds, etc.

If you have an older alternator without voltage regulation (making it variable) or that might feed less than 13 volts, you might have to go with this relay method. The Solar post on the CTEK will manage this erratic power supply.

If on the other hand, you have a modern and stronger alternator, just stick with the Alternator post.

EDIT: I should add that if I found myself in that situation, like I am currently with the weak 4Runner alternator, I would head out to an alternator shop and invest in an upgraded alternator. What's happening to me right now is my Automatic Charging Relay is disconnecting my batteries when I'm at idle for longer than 10 seconds, because my charging voltage from my alternator is dropping below 13.1 volts. So I'm bartering a deal (since I don't have all the cash) with a local alternator guy to get me a new alternator (14.4 volt, 120 Amp) and this will stop happening.

Just FYI just in case that deal falls through. Im A DC power alternator dealer. They make very good high output alternators. As soon as I need it I'll be getting one of their units for my truck. I'll hook u up at my cost since your helping me with my truck.

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Thank for the offer, Raul!

I probably could not afford it even at cost, lol! We're a DC Power dealer too, and I didn't even bother looking at their option.

I know for the E350 surveillance van I built, the 280 amp alternator was like $900! :wow
 
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