DC to DC charger

pianotuna wrote:

Reisender wrote:
I’m not sure what the source is here. Is it the trucks 12 volt system you want to use to charge the truck campers battery? Why would you need a DC to DC converter for that. That is what the trucks charge line is for on the 7 pin. What am I missing?

We use a DC to DC converter but it is from one static battery bank to another. So no alternator etc.

My oem and additional charging circuits worked well for lead acid. But when I changed to telcom, I got no charging from the alternator unless something such as the microwave was running.

I've added a dc to DC 20 amp charger, and I'm seeing up to 19.6 amps going into the house bank. I started a thread with my observations.

Interesting. Thanks Don.

I just use a pair of 8 gauge wires from the truck battery to the camper batteries. That eliminates the voltage drop of the 7 pin and puts a nice charge into the camper batteries whenever I drive. I use a 200 amp blade switch that is mounted on the truck battery to isolate the truck battery when the situation calls for it, but that is rare.

Hemi Joel wrote:
I just use a pair of 8 gauge wires from the truck battery to the camper batteries. That eliminates the voltage drop of the 7 pin and puts a nice charge into the camper batteries whenever I drive. I use a 200 amp blade switch that is mounted on the truck battery to isolate the truck battery when the situation calls for it, but that is rare.

I added dual #8 wires. When I switch to telcom jars--no more charging. I do have manual control over the 200 amp solenoids I added. The dc to DC charger was, for me, a huge improvement.

I mounted my Victron Orion in the camper as shown here

I already did a cable upgrade between the truck can camper back in 2015. Here's that project

Hemi Joel wrote:
I just use a pair of 8 gauge wires from the truck battery to the camper batteries. That eliminates the voltage drop of the 7 pin and puts a nice charge into the camper batteries whenever I drive.

It has been proven 100s of times, that with modern vehicles, large gauge wires will NOT give you a 100% charge on your auxillary battery bank.

Some charge, yes. Just not 100%.

deltabravo wrote:
I mounted my Victron Orion in the camper as shown here

I already did a cable upgrade between the truck can camper back in 2015. Here's that project

Of course, you now know that wiring upgrade is not required when you get a new truck !

theoldwizard1 wrote:
Of course, you now know that wiring upgrade is not required when you get a new truck !

No, I don't know that.
I can't envision how the excessively long wire run of smaller gauge wiring of the stock truck wiring (on a new truck) will provide the amperage I see with my upgraded system

theoldwizard1 wrote:

Hemi Joel wrote:
I just use a pair of 8 gauge wires from the truck battery to the camper batteries. That eliminates the voltage drop of the 7 pin and puts a nice charge into the camper batteries whenever I drive.

It has been proven 100s of times, that with modern vehicles, large gauge wires will NOT give you a 100% charge on your auxillary battery bank.

Some charge, yes. Just not 100%.

That makes no sense at all. The alternator doesn't know how many batteries are connected to it. It senses voltage. Batteries that are connected equalize over time.

Regardless, it has been working for me for over 10 years. If you want to buy a device to charge your 12 volt batteries better than a 12 alternator that was designed to charge 12 volt batteries, that's your call.

With a modern vehicle the charge voltage will be at least 13.5 volts, probably more. That will charge the house batteries 100%, though it may take a long time, and only if the charge wire to the camper is large enough to service the house loads. If you have your refer on DC for example, it is drawing around 30 amps. The #10 typical of a 7 pin harness will be dropping about 1.8V in the 60' round trip on the wire. Now your 13.5V is only 11.7 and, yeah, no charge, in fact it will drain the house. May burn up the 7 pin too. Change that wire out to #6 with a proper connector, and even at the same length and amperage, you will have a 0.7V drop, your 13.5 volts is now 12.8, almost no charge but at least not draining the house battery

A DC to DC charger placed near the alternator, without remote sense, does not solve this wiring problem, voltage will still be low. Placed near the load, or with remote sense near the load, it band-aids the problem: It will boost the voltage back to where is it supposed to be, at the cost of drawing even more current through the inadequate wires.

You need to address the wiring problem first, then consider a DC to DC charger. Or don't run large house loads (like the refer) on DC.

Hi HMS Beagle,

With lead acid house bank and lead acid starter I had charging. Enough that a 60 amp fuse fell on its sword.

My upgrade was to dual #8 (oem was #8) with twin 50 amp automatic circuit breakers. My ammeter maxes out at 70 amps--and I did have occasions where it would not display.

The lead acid were replaced with telcom jars, and whoops there was no charging from the alternator to the house unless I was running the microwave or other heavy draw. In fact it regularly sent power to the alternator. I replaced the starter battery with an AGM. No improvement.

My 20 amp renogy 20 amp dc to DC charger is sending up to 19.6 amps to the house bank. It is NOT a short run and is #8 wire. There is no voltage sensor.

I'm happy as a clam to have charging going on.