DC to DC inverter

New to Toyotas and towing an RV. Does anyone have thoughts on charging up RV batteries while driving? Just switched from an F150 and it wouldn’t even trickle charge the lithium batteries the traditional way.

 

Welcome!

What kind of RV?
Are you using the 7 pin plug or the 4 pin?
Do you have a charger on your RV battery?

Lithium battery chargers are specific to lithium batteries.

A DC to DC charger would probably solve your issue as they usually can switch between different batteries. Or a lithium battery charger on the RV side that gets activated when you plug in the RV to the truck.

 

Thanks! 16' 2022 Airstream Caravel with two Battleborn lithium batteries. With the F150 I would boondock/dry camp for 4-5 days and then move to the next spot. Usually with a 5-6 hour drive in between. The battery would never get more than a nominal charge that would last me half a day.

 

I know my 21 does a fine job of charging my lead acid deep cycle while driving. But your circumstances are totally different.

 

The truck charging system does not reach the needed voltage to charge our lithium trailer batteries. The truck will do fine with Lead Acid or AGM which have a lower peak voltage.

Previously, I disconnected the 12v charging feed from my Ridgeline and when we got the Tundra I unplugged the SUB Batt relay, under the hood, but nothing really changed so I just leave the relay in all the time. I wanted to avoid the load on the truck's alternator. But along the way, I switched to a 250ah monster of a Lithium battery and I find that the truck doesn't even try to charge it. I have my solar panels turned on and they can recharge my battery quite well.

If you need to charge the trailer battery from the truck the best way is a DC to DC charger like Wallygator said.

 

As @Wallygator said a dc-dc charger would be best. If you’re planning on adding solar panels then a dc-dc mppt charger would be your best bet. Only being a 5 hour drive in between stops you’re going to want the biggest charger you can get to fill those batteries up quick. If you go dc-dc mppt I’d suggest you go redarc bcdc 1240d. This will give you a full 40 amps while driving as it’ll pull what I can from the solar panels and then supplement the rest from your truck bringing it to a full 40amps. Other dc-dc mppt chargers, like Renogy and other cheaper ones, offer a 50 amp charger but if the charger detects any voltage at either the truck or solar side then it draws a line down the middle. So say you’re only getting 1 amp from your solar panels, you’d only be pulling 26 amps total. 25 from the truck and 1 from the solar.

just something to think about..

 

Good info, thanks

 

Can obviously fix this by wiring in a relay cutoff switch but can just make your life easier by purchasing redarc from the get-go

 

I’m looking at getting a fridge soon, and possibly doing a dual battery setup, so this is something to remember. I had already planned for at least one solar panel(made a rack on the cap)

 

I'm running a Victron Orion-Tr Smart 12/12-30 DC-DC charger in our trailer. Started with a 12/12-18, but decided to jump to a 30A after installing the second battery.

Ran a dedicated 4 AWG positive/negative from the truck battery, through a 50A breaker and to the rear bumper. I mounted a 175A Anderson plug on the bumper.

Installed a separate 4 AWG lead with Anderson plug from the trailer tongue to power posts inside the trailer near to the charger, then 6 AWG to the charger since that's the largest wire it can accept.

The charger has auto engine detect to allow it to turn on/off and you can also fully configure charge parameters and enable/disable it from the Victron VE.Smart Network via Bluetooth on your phone.

I can feed up to 35A into our batteries while driving now.

 

That looks EXPENSIVE!

 

Beautiful setup. Did you do all that work yourself? Have any photos of your solar array

 

Thanks, yes I've done all the work myself.

For solar we're using a homemade 200W solar suitcase that I made from two 100W Renogy Eclipse panels wired in series.

Since we camp a lot in the woods, roof-mounted panels wouldn't do much for us except while traveling, that's why I went with the DC-DC charger.

 

Some of this can be reduced by designing/building or buying custom battery packs going with LifePo4 cells (3.2v/cell nominal) instead other more standard lithium chemistries. A 12v LifePo4 battery pack will get mostly charged by the 14.4v output by most vehicle charging systems though charge controllers are still a good idea but a DC-DC converter should not be strictly necessary.

 

The wire size in the truck is not going to allow more than a trickle charge at best, if you truly want to charge LiFePO4 batteries from your vehicle a DC-DC charger is the best way.

If you have roof-mounted solar panels, then those can charge your batteries while traveling.

 

I made an account just to say thanks for posting the diagram!

 

@UATundra that's a great piece of work and excellent documentation!

 

Thats an awesome system. I have a couple of questions. For a truck setup (no trailer) I guess the "isolated" setup is needed where + from vehicle battery to lifepo4 + and (-) to (-)
Secondly, most of these systems talk about a cable to ignition to detect whether engine is running. I see this one also has a port. What is this auto engine detection thing? It would be very useful because it would negate the need to tap into the fuse box

 

I believe the isolated/non-isolated comes more into play with marine applications. I've seen both used in truck/trailer combos and also truck only setups.

You set the parameters in the app, the engine detect is based on voltage from the alternator. You set it where once the voltage reaches a trigger point the charger energizes, you also set the shut off voltage.

 

Will it work in the hybrid? Its voltage rarely moves. I guess it behaves more like a smart alternator. for Renology I would need to pull a D+ cable to an ignition powered circuit

 

That thing kinda sucks because it can only take 32V from solar. And that is doubly true if you are running a 24V battery setup. I looked at it when I first was figuring out my system. My two 100watt Renogy panels output close to 40V in series.

 

You would not want the DC/DC charger continuing to charge your house battery while the truck is off. Thats why they have the engine detection.

 

I am wondering how effective it is with a smart alternator or a hybrid motor generator.
Renology uses a IGN cable which you connect to an ignition enabled circuit. However the automatic ones I am wary off

 

I, personally, would never run panels on a vehicle in series. If one panel hits shade then the voltage is going to crash out and greatly reduce your overall watt output. If one panels hits shade in parallel, your other panel is still putting out max watts. Just something to think about.

 

And running in parallel on a cloudy day can cause parallel panel voltages to drop below the battery voltage which you dont want. This is also why I decided not to vehicle mount my panels. I can keep them in a good position all day long. My 200 watts of panel will pretty consistently run at 175-180 watts. Even today in Mid October in Northern Utah they were push 175.

 

Hi
Which one do you use? Is your truck a hybrid or regular Tundra?

the hybrid voltage goes from 11.9-14V depending upon engine state, motor generator state etc.,

I am wondering whether frequent turn of and turn off of something like a victron/renogy DC-DC chargers will be an issue

 

I use a 20A Renogy DC to DC charger to a 100ah lifep04 battery. I use the tail light circuit as the trigger wire to turn charger on once engine is running. The charge feed wire is the 30A circuit in 7pin trailer plug from the truck, which is (from the factory) switched on via relay when truck is running. Simple

 

Do you have any pic of the install? Plug and play or did you have to cut and splice wires?