Multi-day off-road vehicle camping is much more enjoyable if you have a reliable battery system to run portable fridges, lighting and electronics. We’ve found the key elements of good overlanding 12 volt power system are high-efficiency solar panels, deep-cycle battery and an efficient charge controller.
In the past, on our R-Pod travel trailer, as well as our overlanding vehicle – we skimped on the last item, the charge controller. In retrospect this wasn’t really a wise decision. After upgrading our solar charge controller to a Renogy DC-DC Dual Input MPPT charge controller, we wanted to share how it seems to be working, as well as a few install tips.
Update: We just upgraded to a Weize 100 Ah lithium battery. So far so good!
(This is a review, not install instructions. There are no affiliate links to this product and we did not receive any compensation for this post.)
Key Takeaways – (If You Don’t Want to Read Entire Post)
- Was the Renogy Dual Input DC-DC Charge Controller worth $200 more than the PWM – Yes
- Should you buy the optional BT-2 Bluetooth module for smartphone monitoring? – Yes
- What features do we like? Having one charge controller for both alternator to house battery and solar charging, power monitoring app.
- Downsides? Cost (around $220) is much higher than PWM controller. Phone app is good but could use improvement.
Prioritizes the House Battery
Look, we’re still figuring this thing out, but one thing we’ve learned is that it will charge the starting battery from the solar panels, when the house battery is full. This is good, because sometimes there are things on our vehicle that will run down the starting battery while we’re camping, and surprises when you go to leave aren’t good.
Why Use a Dual Input MPPT Solar Charge Controller?
For RV’ing, off-road vehicle camping or overlanding, it’s handy to charge your house battery when driving, so when you arrive at camp it’s fully charged. There are a couple ways to incorporate charging the house battery from your alternator with solar panels, but the simplest (not necessarily cheapest) way is to use an all-in-one charge controller that handles both tasks.
The Renogy Dual Input DC-DC charger does this for us, and by using the optional $30 BT-2 Bluetooth module, we can check how much power we’re making, battery status, etc., on our smartphone.
MPPT vs. PWM
Without getting into the science of how they work, the bottom line is this: MPPT solar charge controllers (maximum power point tracking technology) are 92-95% efficient. This excellent when compared to PWM charge controllers (pulse width modulation), which work at about 70% efficiency. Instead of precious solar power being wasted, it’s now going into our house battery.
Our Setup
We used in-line 40 amp AGU fuses at the starting battery and house battery, and ran 8 AWG wire from our truck’s battery though a neoprene grommet in the firewall and along the driver’s side floorboard – under the plastic trim, through wire sleeves – to the house battery in the rear of the cab. (Our truck has the rear seat removed.) We We secured the group 29 battery in a battery box using a ratchet strap to eye-hooks bolted into the frame.
- Charge Controller – Renogy DC-DC Dual Input MPPT On Board Battery Charger
- Solar Panels – One 100 watt Renogy semi-flexible thin panel, two Renogy 100 watt rigid panels.
- Battery – Weize 100 Ah lithium battery.
- Fuses – 40 amp in-line AGU
- Starting Battery/Alternator Wire – 8 AWG (bare minimum recommended by Renogy – 6 AWG would have been better, but so far no problems using this size.)
- Wire from controller to house battery – 6 AWG with crimped/soldered ring connectors.
- BT-2 Bluetooth module and DC Home app.
- Group 24-31 battery box
*50 amp version of controller will need heavier wiring/fuses.
Tip – Whether or not your vehicle has a variable alternator or not, you must install the ignition wire for the controller to work properly.
We store our semi-flexible Renogy 100 watt panel under the rooftop tent cover when traveling. These are fairly tough, but you do need to treat them with care. (See stress cracking on lower left of panel at grommet.)
How’s It Working?
For powering our Dometic fridge/freezer, we found that between being able to charge our house battery from our alternator while driving, and with more efficient charging from the panels, we can often get by with just one lightweight, semi-flexible 100 watt Renogy panel on short trips. (This thin panel weights only about 4 pounds and is light enough to tie anywhere on our rooftop tent when camping.)
The Renogy dual input MPPT controller also seems to charge our house battery much more efficiently on cloudy days. We also notice it replenishes the deep-cycle faster than our old controller with the same amount of sun.
We still bring our two heavier 100 watt panels, along with the thin 100 watt one when we plan to camp in the same spot for several days – for a total of 300 watts of charging power.
BT-2 Module and DC Home App
The add-on BT-2 Bluetooth module works pretty well with the Renogy DC home app. We like being able to look at our phone when arriving at camp to see if we need to set up the solar panels, or if we have charged the house battery enough while driving to last until morning.
The BT-2 module and DC-Home app work great, but there are a couple things that could be improved on. If you lose the Bluetooth signal, the info on the monitoring app keeps displaying, with the charging icon rotating, as if it’s still communicating with the controller. It works well up to about 50′ away, but if you lose signal you may be looking at old information and not know it. To re-establish a Bluetooth connection, we have to close the app, then re-start it.
Also, one one occasion we somehow got logged out of the DC Home app and while it doesn’t need internet to work, you do need a cellular or wifi connection to log into the app for the first time. This has only happened to us once while off-grid and is a minor issue. If you’re setting up the BT-2 module and DC Home app with the charge controller somewhere truly off-grid for the first time, you’ll have to drive to somewhere with a signal or wi-fi to log in.
Renogy DC-DC Dual Input Onboard Charge Controller Setup Tips
The charge controller comes with a small wire and plug to use as a battery voltage monitor. Unless you’re mounting your house battery far away from the controller, you don’t need to hook this up. It also has an input for an ignition-on wire, for vehicles with variable alternators. We hooked ours to a fuse in the passenger side fuse compartment, using a fuse tap.
We placed the battery temperature sensor inside the battery box, taped against the battery. The BT-2 Bluetooth module should be placed in a window if possible, for maximum range. Be sure to set the controller to your type of battery (flooded lead acid, lithium, etc.), using the small button under the left side cover.
The Bottom Line?
If you want an efficient solar charging controller for overlanding, and one that allows you to charge your house battery from your alternator when driving, it’s hard to beat the Renogy Renogy Dual Input MPPT DC-DC On Board Battery Charger. There aren’t many affordable alternatives out there that let you do both from one controller. It’s about twice the size of our old PWM charge controller, but we made room for it.
At just over $200 it’s the second most expensive part of our overlanding 12 volt solar power system (after the battery), but so far worth every penny.
