DC-DC charger help pls

[Allie4140]

Hi y’all! My name is eva. I am trying to install a Renogy dc to dc charger and I don’t understand how to connect it to the starting battery. I’ve searched yt and watched videos but I’m not getting it I guess. Idk how to connect it to a fuse that is on when the can is running. My van is really old and the fuses aren’t labeled. Can I just connect it to the starting battery, then to a kill switch and then onto the charger? I only want the charger to run when I’ve no sun for my solar. I’ve lithium batteries if that makes a difference. I wld be so thankful for any help. Thank you so so so much.


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[MrAlvinDude]

Hi Allie4140 (Eva).

Is the DC-DC charger one like this?
https://www.renogy.com/12v-dc-to-dc-on-board-battery-charger/


As is also shown in this video?


If it is, then you can connect the DC-DC charger the following way:

Starter battery - fuse -  long wire - DC-DC charger - short wire - lithium battery. 

(It is most likely recommended to place the DC-DC charger close to the lithium battery, as the DC-DC charger will eliminate any voltage drop in the power line/wire, going from the starter battery to the lithium battery. )


And then you add a small switch in the "D+ signal cable".
This switch carries hardly any amps, so it can be any little easy-to-place switch.


This way you can chose to use the DC-DC charger,  ONLY when the switch in the "D+ signal cable" is on.


If you connect the other end of the "D+ signal cable", to a location in the wiring system of your car, that only has power when the engine is running, then you have the double security of the DC-DC charger only being active and ON, when both situations are true.
As in:  when both;  the motor is running, AND when the switch in the  "D+ signal cable"  is ON.


You can add a Main/Kill switch in the power lines, but it is not necessary, as there is already a remote-controlled Main/Kill switch built into the DC-DC charger.

And this remote Main/Kill switch is ONLY ON, when +12V is supplied to the "D+ signal cable - screw terminal" on the DC-DC charger unit.

So when the "D+ signal cable - screw terminal" on the DC-DC charger unit, is NOT connected to a 12V source, then the (built-in) remote-controlled  Main/Kill switch is OFF.  And no charging of the house/lithium battery is happening. 




I hope this explanation makes sense ?  Otherwise, please ask more. Okay?

 

[highdesertranger]

Welcome Eva to the CRVL forums! To help you learn the ins and outs of these forums, this "Tips, Tricks and Rules" post lists some helpful information to get you started.

Most of our rules boil down to two simple over-riding principles: 1) What you post should provide good information (like your introductory post), and 2) Any response to someone else's post should make them feel glad they are part of this forum community.

We look forward to hearing more from you.

a quick tip, when asking a question about a specific item it is easier for us if you give us a link the the item in question.

highdesertranger

 

[tx2sturgis]

That ignition line is a trigger, it tells the B2B charger when to begin charging. 

It can be hooked to any source that is active 12v when the engine is running...you can use a circuit tester and find a fuse that is only live when the engine is running, or, failing that, you can tap into the 'RADIO' fuse....it wont be ideal....because you will not be able to leave the ignition switch on ACC for long.....but you can buy a piggyback 'fuse tap' that will let you do this easily...look in the fuses and bulbs aisle at any autozone, o'reilleys, napa, etc. You will need to use the type of tap that is compatible with whatever fuse type you have.

 

[user 423]

My van is really old and the fuses aren’t labeled.

If you search on Google Images for "fuse block diagram", (for your make and model) you would probably be able to find one that has been copied out of a service manual.

Also, it's a good idea to have a Owner's Manual for your van. They can usually be found on eBay at reasonable cost.

An OM will have a fuse diagram plus other info you should know about your van.