Adding a DC to DC Charger to our 2019 T@B 320 S

mnmarkiemark

After a tough learning experience last fall out in the smoky west we came home knowing the weakness of batteries and solar power. After spending some time searching the forum I decided to install a 20 amp DC to DC charger to safeguard against drawing down our new AGM battery while traveling down the road and running the Norcold 3 way refrigerator. The following photos should help explain what we did. My thanks to those who have gone before and shared their experience and solutions.

Photo 1:
 I had already installed two aluminum storage boxes on the trailer tongue. This shows how I mounted the charger (upside down, it didn't seem to care). I already had a new AGM battery in place, series 24, it barely fit end to end in the box. Rest of the story and more photos to follow.

mnmarkiemark

Next photo: 
This shows the Anderson type connectors I used. Ran 8 gauge wire direct from the battery to this connector with a 30 amp auto resetting breaker on the hot side. Figuring out where to run the wires was one of the most challenging parts. 

mnmarkiemark

Next Photo: 
This is the auto resetting breaker I ended up using. I tried a 30 amp fuse but had some trouble with the installation. Found this thing on Amazon and so far it is doing the job.

mnmarkiemark

Last Photo:

This is how I rigged up a switch to turn the whole thing on which I do just before traveling. I put it right inside the door just above the refrigerator. It lights up when it's turned on. I like it there because it's easy to reach from the ground and the other refrigerator controls are right there so I'm not as likely to forget to switch to battery power before hitting the road. Since adding this charger we have had no problems with the refrigerator keeping up or the battery being drawn down. 

Dutch061

Nice install, I have been researching DC to DC Charge controllers and have watched a few videos form various sources including Battleborn.

It is my understanding from this research that unless you upgrade the wiring for the charging circuit from the TV (which you have) AND have either a very high DC draw (if I remember correctly the DC Draw is 10 amps or more) or VERY low resistance batteries (IE Lithium) that the factory wiring on most TV will limit the current removing the need for this.

In your case where you need and want to have more current available, adding a specific circuit outside of the 7 pin connecter and a 20 amp DC Charge Controller is a perfect way to achieve your goal! And 8 gauge wiring has plenty of capacity at 60 amps.

Brad

mnmarkiemark

Thanks Brad,
I'm just happy that it works as we were having so much trouble with battery drain from the refrigerator when traveling. Now our food stays nice and cold and the battery stays charged. I installed a Victron battery charge monitor and that has really helped us see what's happening with it. I would say the monitor should be one of the first mods someone should make because it is so important to understand what's going on with  your battery before it's too late. We learned that the hard way last fall. 

Dutch061

@mnmarkiemark, I agree the BMV-712 is an item that I consider a "must have" for boondocking. Even though I had what I consider "an above average understanding of Capacity, Amp Hours, etc. I have learned it to an entire new depth as I have worked with this RV and some of the configuration settings.

I had no previous experience with solar panels or solar charge controllers etc. but have thoroughly enjoyed the learning curve and feel that Victron, Renogy and others have some really neat stuff to offer. 

We had a 2017 320-S previous to the 400 BDL, and I also learned the hard way about the refrigerator and running it on 12 volts. Fortunately, the first time it happened we were at a site with full hookups. 

Brad

CharlieRN

Thanks @mnmarkiemark - I've been thinking about switching to a lithium battery which means adding a DC:DC charger, and your post and photos help a lot.

Adding a charger is actually mandatory now, as I just pulled the trigger on a Battleborn LiFePO4 battery on sale for under $750. They are "blemished" but that refers only to cosmetic issues and they still come with the standard BB warranty. The new battery, even though it's "only" rated at 100Ah, will more than double my present usable capacity. Combined with the on-board solar and my Renogy 100w solar suitcase, I should be good for a few worry-free days of boondocking.

Dutch061

@CharlieRN, based on videos from Battleborn you will not need to add the charge controller, your TV should have small enough wire to limit the amperage. If you were to add the dedicated circuit outside the 7 pin, then it becomes mandatory.

Brad

CharlieRN

Brad - I asked about that when I spoke with Battleborn.

My assumption was that the only negative in not using a DC:DC charger was the likelihood that the charging profile of the TV alternator would not fully charge a LiFePO4 battery. They told me that was only partly true, and that it was possible to damage the alternator if you did not use a DC:DC charger or at least an isolator. Their recommendation was to disconnect the battery circuit in the 7-pin to get the alternator out of the loop if you do not use a charger or isolator.

I'm not saying that you're wrong, only repeating what BB said. I'll take a look through their videos to see if the advice I got is inconsistent with what they say there.

Edited to add that my 7-pin battery wire is 10 gauge (with circuit breaker), so perhaps that's the difference.

Dutch061

@CharlieRN, yes that would certainly make a difference. For me my current TV is a 2017 F-150 that doesn't charge the batteries anyway. The new TV may be a different story but it will have a 240 amp alternator so it still shouldn't be an issue. 

No offense taken here, I am wrong at times like everyone else. 

Brad

Edit: BTW I believe that you will be very surprised with how well the Lithium batteries will perform.

CharlieRN

Dutch061 said:

. . .
Edit: BTW I believe that you will be very surprised with how well the Lithium batteries will perform.

I am totally prepared to be very pleasantly surprised . . .

mnmarkiemark

I made a mistake when I wrote that the new AGM battery is a series 24. It's a Duracell 31 series deep cycle with 105 amps. I would like to get a lithium battery some day but right now the cost is just too much. We were out for a 5 day dry camping trip to northern Minnesota about a month ago. Partly sunny every day except for one more cloudy with some rain. We had a pretty open site and caught the sun about 65 percent of the available hours. The solar collector did a good job and the larger AGM battery never dropped below 95%. It's so much better then the original setup. Doing another 5 day trip next week so we'll see how that goes.

CharlieRN

@mnmarkiemark - couple of questions on your installation if you don't mind.

It looks like you used the Renogy 20 amp unit, one that I'd also like to use because it gets good reviews and is good value for money.

One of the drawbacks to the unit however is that it does not auto-detect power. So you need to run a separate connection to a switched hot side (ignition) wire somewhere on the TV. How did you handle this?

There is also a connection on the changer to limit current - did you wire this or just ignore it?

Regarding the battery connections, is is necessary to run both positive (fused) and negative cabling back to the TV battery? Or can you simply use a chassis ground?

mnmarkiemark

Charlie,
Glad to answer your questions as best I can.
I use the lighted switch that I installed above the refrigerator as a separate power source to signal the Renogy when we are ready to travel. The charger will not operate unless that switch is on. I like having that separate control.
 
I did not do anything to limit the current.
As you know the Renogy has what they call a Smart Protection Feature to prevent overcharging and overheating plus reverse polarity protection.
Should I be worried about the current draw?

I chose to run both negative and positive wires from the battery to the Anderson connector on the TV. I figured since I had to get under my TV anyway that it wasn't going to take much more effort to do both. Grounding to the chassis might work just as well, I'm really not sure.
On the house battery side the positive runs directly to the battery but the negative runs to the shunt on the Vicktron battery charge monitor/controller. Every negative wire runs from that shunt.
So far this setup has worked perfectly.
It is so nice to arrive at a destination with a fully charged battery and cold food in the refrigerator.
Hope all goes well if you put one in!

CharlieRN

@mnmarkiemark -  thanks very much for the information. The idea of a separate switch to energize the charger is a nice idea. On the current limiter circuit, everything I read says that there is no need to worry about using this feature. In the Will Prowse video, he says something like "I'm not really sure why Renogy added this . . ."

Again, thanks.

patandjeff

good post thanks .. we are using, Renogy  20 amp B to B charger , 8 gauge wiring pur renogy spec.
voltage drop is quite a lot in DC wiring unlike AC wiring ,use a DC wire table.
We use the Anderson connector as the switch , AMG batteries , all works as intended.

DenisP

I installed a Victron 30A DC/DC charger (isolator) in my 2018 400.  I used 6 gauge wire with Anderson connectors at the bumper of my 2013 Tundra.  The Victron Charger works in concert with my BMV-712 and Victron Smart solar 75/15 controller and all are monitored through the Victron connect app.  The Victron DC/DC detects when the truck is running and disconnects when it is not running.  So far very pleased.

mnmarkiemark

Denis,
That sounds like a perfect solution.