DC to DC charging 2007 Voyage

[Ibubigdaddy]

I am upgrading to Lifepo4 house batteries in our 2007 Voyage 35L. I am installing 2 100 amp batteries, new converter that can charge Lifepo4 batteries, and a DC to DC charger between the engine alternator and the Lifepo4 batteries. Due to the fact I live in Florida, I’m going to place them under the steps like my current set up. The batteries do have low temperature cut off.

My concern is placing the DC to DC charger (30 amp) to keep from overtaxing the alternator if the batteries are low.

Has anyone done this? Should the DC to DC go between the alternator and all the batteries, or between the starter battery and the Lifepo4s? Is there a good location? Thx in advance for your help.

[creativepart]

Not directly to the alternator, just connect either to the chassis battery (starter battery) or to another similar type of 12v source, not just any 12v source. You’re going to want to use a source capable of 30-amps or more depending on the DC2DC charger you use.

I connected my Victron Orion 30-amp charger directly to my chassis battery. One of the great features of the Victron is that it senses when the engine has started or stopped without needing a cable run to the ignition. Most other such chargers don’t do that and require you to run an ignition trigger cable.

I have 400aH of LFP batteries and find the 30-amp Victron plenty powerful enough for my batteries.

[Ibubigdaddy]

Thank you. That is exactly what I needed to know. First time with Lifepo4 batteries.

[creativepart]

I found there to be lots to consider when changing batteries to LFP. Since you’re installing a DC2DC charger I assume you have figured out how to prevent your alternator from charging your batteries while driving. -such as removing or replacing any latching solenoids or BIM. And you’ll likely find a need to charge your chassis battery when on shore power in a campground for more than a week or so.

I’m in South Texas, so I got batteries with low temp cut off features, too. But I found a need to both seal up the open battery compartment and to add heaters to my batteries. Not only does the temperature drop into the 30’s here, but on trips to higher elevations I was finding cold temps a recurring issue that was preventing recharging the batteries.

All that said, the LFP batteries are great and your need to run a generator is greatly reduced. I have only 300w of solar but find it doing a fine job keeping everything charged.

[Ibubigdaddy]

It’s nice to have a guide when going down a new road. I don’t think needing to charge the chassis battery is an issue. We rarely stay more than a week. I would be very interested in how you enclosed your battery compartment and heated it if it is under the steps like mine. Forgive my ignorance, but let me get this straight. Alternator to chassis battery, chassis battery to Victron, Victron to house batteries. And make sure the alternator is not charging the house batteries. Feel like I need a PhD in DC, LOL!

[creativepart]

When doing my install last April I didn’t do anything about chassis battery charging. I was plugged in to power at home and after a week I couldn’t start the RV without jumping the battery.

When in storage with the chassis battery disconnect off the battery doesn’t drop all that fast. But when sitting in a campground on shore power with the chassis battery not disconnected things are different. I had to add an Amp-L-Start to my setup to overcome this issue. It works great, but now that product is out of business. So, I don’t know what you do now.

As to closing up my batteries, mine are not under the stairs but in a compartment that was open. I used 1/4” plywood to create a battery box around the inside of the compartment. And for battery heaters I used Facon Tank heaters from Amazon.

Here’s a photo - warning it’s prettier crude:

[creativepart]

Originally Posted by Ibubigdaddy

It’s let me get this straight. Alternator to chassis battery, chassis battery to Victron, Victron to house batteries. And make sure the alternator is not charging the house batteries.

Sounds right to me. I have a lengthy post on this install over on www.irv2.com. Here’s a link:

https://www.irv2.com/forums/f54/dc2d...im-576908.html

Note: not every motorhome has a BIM like mine. But all have something that does that same set of functions.

[creativepart]

Just to throw out some more info… the new LFP batteries seem to last and last. My solar panels do such a good job charging them quickly that I actually turn off my inverter‘s charging function when camped on shore power. You have a converter charger, not inverter, so I doubt you can do that with your set up. It’s not a problem leaving the charger on, but they just don’t need much charging other than my solar.

And truthfully I don’t see that much charging coming from the DC2DC charger either. The LFPs never get into a very low state of charge so when driving the solar panels are charging while you drive and this leaves little for the Victron Orion to do.

I mean you need all of this stuff when you really need it, but most of the time it’s not doing all that much.

[Ibubigdaddy]

Thank you so much for your help. Love these forums.

[creativepart]

If you read that IRV2 link I provided about my "jouney" to LFP you will see that I went through all kinds of crazy thoughts and plans that were unworkable. So, keep that in mind. About half of that thread was me saying stuff that was basically nonsense and not at all what I ended up with.

My point is, do a LOT of research before hand, watch a ton of YouTube videos and read a lot of posts on IRV2.

(NOTE: Youtube has a ton of LFP install videos in Vans and Sprinter Vans because of the "Van LIfe" boom - much of that will not apply to your motorhome.)

[Morich]

I've not dealt with the battery change, so not much help on the changes but I might throw in some info on what you might find before change as a way to spot some details and where they are found.

There is often a need to seperate the two battery groups and that may involve the "mode solenoid" as that is where the two get connected at different times. When we push the boost or "AUX" switch to jump start the engine or when we start the engine, there is a lead "LR" going down to the mode solenoid which sends 12VDC down, through the solenoid coil to ground. The ground wire as well as the mounting screw give ground to operate the solenoid.
One each side of the solenoid, there are two big lugs where cables come from chassis and coach batteries.
This is one place where you may want to change some things to isoate each group??

Point to help might be that the cables also should have had tape near the ends to ID each cable.
I have marked this info on the drawings from here:
https://www.winnebago.com/Files/File...ire_157461.pdf

Click this snip or go direct for the full picture?



If only wanting to remove the connection , the mode solenoid would be disabled if the small LR wire is removed and taped back. This might also be aplce for some equipment is small enough as it has direct battery cables to each set. The tape ID should also be the same at the battery end.