Dual-Battery Trailer wiring diagram

[ldivinag]

So NL uses a time delay rather than sensing the voltage of the starting battery and only charging the house batteries after the start battery has reached a threshold voltage?

it does both.

check out the diagram on page 11:

http://www.sierraexpeditions.com/productimg/split-charge_manual.pdf

it does a good job of explaining the heart of NL thing...

 

[ntsqd]

From what I'm reading there the NL does sense battery voltage, but the solenoid engagement is only determined by a timer triggered by a voltage threshold ("Phase 0", page 11). I think that the threshold used is below that of a fully charged starting battery (13.1 vs. 13.6). This makes no sense to me. If you're going to sense voltage, why not trigger a connection when you know that the starting battery is fully charged rather than estimating when it is fully charged?

 

[ldivinag]

cost? simplicity?

you will need another circuit to test and jump when the primary batt is 100%.

i dont mind their 10 minute cycle. after all, after the 10 minutes, it checks. if still under 13.7, then repeat 10 minute cycle...

 

[eugene]

I just went back to a seperator myself, I prefer the isolator but since its in the middle of the starting battery charge circuit its one more point of failure to fail like it did last month. I picked up one from NAPA and have it mounted where my isolator was until I can put it in a better spot. Its also supposed to sense voltage on each battery not not engage the solonoid unless the voltage is high enough.

 

[ntsqd]

It would cost more and add complexity to include a timer in the design. I'm guessing that NL felt it worth doing or they wouldn't have done it that way. I just don't see why they went that route.

 

[eugene]

Mine has a timer as well, its there for short term voltage changes, for example ideling and roll up the power window and the voltage will drop for a second, that way the seperator isn't switching in and out during those momentary times.

 

[evldave]

Just a quick update on this...got back from my trip to tahoe and the setup worked great! I unplugged the fridge from the trailer and ran it off the battery cart (separate from trailer + truck). Once the battery ran down, I rolled the cart back to the truck, started it and let it run for a minute or two, then plugged in the cart, it charged right up and worked great. Took about an hour to charge the battery almost back to 100%.

Using 4ga wire, I was getting ~0.3v drop from main battery to the charging battery in the rear. I was surprised, I was expecting more drop (through solenoid + wire + connectors).

Next up will be to upgrade to larger solenoid + 0ga wire + extra jumper switch to be able to jump backwards through the system. Realistically, this is a low priority since I can easily manually jump from the backup using the jumper cables I carry.