Dual-battery setup for the Hybrid 4Runner

[vready]

In a previous post, I described how I built my 2025 TRD Off-Road Premium iForceMAX 4Runner to be a self-sufficient adventure vehicle for extended, multi-day camping and overland/off-roading trips. I equipped it with a Dometic CFX3 45 Electric Cooler which runs off 12v DC, along with other 12v accessories that make camping trips comfortable and convenient.

To power my accessories while in camp, I was looking for a dual-battery solution that would do the following things for me:

• Power my refrigerator and other accessories for extended stays (1024Wh capacity)
• Recharge using the hybrid charging system and augment my 12v starter battery
• Allow everything to run off shore power, when AC hookups are available
• Efficiently recharge the auxiliary battery whenever the engine is running/idling
• System that is simple to configure and monitor without a lot of complexity
• Doesn’t require major vehicle modifications or diminish cargo carrying capacity
• Ability for the auxiliary battery to recharge or jump my starter battery, if needed
• Allow solar charging of the auxiliary battery for extended stays in one location
• Can be unplugged and removed from the vehicle in 30 seconds when not needed

After researching various options, I went with the EcoFlow Delta 3 Plus Portable Power Station. I like it because it’s compact, has convenient output ports for AC/DC/USB, meets all of my functional requirements, and comes with a great iPhone app which allows me to monitor and control everything in one place.

In addition to the Delta 3 Plus, I’m using the EcoFlow 800W Alternator Charger, and the EcoFlow 220W Bifacial Portable Solar Panel.


Here’s an overview of how the entire system is wired:

* Yes, I know most hybrids don't have an alternator. It represents the vehicle charging system (DC-DC converter).

Here’s how it’s installed and how I use it:

The Delta 3 Plus fits nicely behind the passenger seat in the rear footwell. Whenever it’s installed in the vehicle, I run a short, 2-foot TrippLite Series 15 Amp power cord from the EcoFlow into the 2,400W AC outlet in the center console for charging. This allows me to turn on the AC 120V switch and charge the Delta 3 Plus using the Toyota hybrid charging system whenever the engine is running.

Next, I installed the 800W Alternator Charger under the driver seat. I connect the charging input labeled “Battery” to the Delta 3 Plus using the provided cable, and I ran the other cable labeled “Alt In” to the Odyssey AGM48 starter battery in the rear cargo area by routing it under the door sill covers and behind the plastic side panels.

When I’m in a developed campsite with electrical hookups, I use this GE 3-outlet Power Strip Surge Protector 15ft Extension cable, which is rated for 13Amps / 1625 watts, to connect the EcoFlow to shore power. I simply unplug the AC cord from the Toyota 2400W outlet, and plug it into the extension cable.

I don’t use the solar panel very often (because I’m usual driving from place-to-place enough that I can just charge off the alternator), but when I need it, the 220W Bifacial Solar Panel plugs right into the Delta 3 Plus and is very compact and easy to stow. Since I have a Free Spirit Recreation FSR Aspen V2 Rooftop Tent with a clamshell closure, I can just stow the solar panels inside the RTT when I’m not using them.

Here’s a look at the EcoFlow iPhone app and Apple CarPlay widgets:

The app for the Delta 3 Plus shows the input and output draws, the current battery charge level, and the expected run-time based on recent usage patterns. You can also selectively turn off AC, DC and USB ports, as needed.

The Alternator Charger has three modes:​

​

Charge: charges the EcoFlow using the vehicle’s charging system at up to 800W​

​

Reverse Charge: Allows you to recharge or jump the starter battery using 800W​

​

Battery Maintenance: Used for off-grid basecamps to prevent the starter battery from dying while running 12V accessories.​

The EcoFlow Carplay app allows you to control and monitor the Alternator Charger right from your dashboard. You can turn it on/off and toggle between charging and reverse charge modes.

Here are some things I really like about how it all works together:

• The EcoFlow can charge from the 120V outlet or the Alternator Charger— or both
  • I like to charge at 400W from the outlet and 800W from the Alternator charger
  • This is due to the fan noise when the hybrid charging exceeds 400W
• The combined 1200W can fully recharge the EcoFlow in about 45 minutes
• On shore power, the EcoFlow delivers pass-thru power to all connected devices
• The Alternator Charger can charge the EcoFlow, or reverse charge the starter battery
• The Battery Maintenance feature prevents my starter battery from getting too low
• The iPhone app and CarPlay widget provide useful and detailed real-time data
• My Dometic fridge can run for 2-3 days straight on a full charge while off-grid

EcoFlow has some promotions running right now with discounts on the 800W Alternator Charger, and bundle pricing when you buy the solar panel or Alternator Charger with the Delta 3 Plus.

• EcoFlow Delta 3 Plus (with free carry bag included) - $599 (was $799)
• EcoFlow 800W Alternator Charger - $269 (was $599)
• EcoFlow 220W Bifacial Solar Panel - $299 (was $649)
• EcoFlow Delta 3 Plus bundle with 220W solar panel - $799 (was $1,448)
• EcoFlow Delta 3 Plus bundle with 800W alt. charger - $899 (was $1,398)

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[Gator 22]

Excellent write up, thank you.

 

[BobCape]

Great info! Very detailed and just what I needed. I just bought a 2026 TRD Off-Road Premium iForceMAX 4Runner and have been planning to do something similar. With your writeup I know where to start.

 

[mfoga]

Have you found any issues with the drawing to much power from vehicle battery at any time? Can you just disconnect the cable for charging device to remove battery when not is use?

This might work better than my setup.
Delta 2 plugged into the AC port and also have a solar panel mounted to the RTT. The problem is I would I forget to plus the stupid button.

 

[vready]

Have you found any issues with the drawing to much power from vehicle battery at any time? Can you just disconnect the cable for charging device to remove battery when not is use?

This might work better than my setup.
Delta 2 plugged into the AC port and also have a solar panel mounted to the RTT. The problem is I would I forget to plus the stupid button.

No issues with the the 800W Alternator Charger drawing down the starter battery. It just gets charged by the alternator (or DC-DC Converter) when the engine is running and doesn't have any draw when the engine is turned off. You can also set a trigger voltage in the EcoFlow app (the starter battery is typically at 12.4v when it's charged, but reads 13.9-14v when the charging system is active) which turns the Alternator Charger on when the vehicle starts.

One thing I didn't mention is that I power camp lights and run power to my rooftop tent, and a few other accessories off my starter battery using a SwitchPros 9100 switch panel, so that is what tends to slowly drain my starter battery while I'm around camp.

The "Battery Maintenance" mode on the EcoFlow 800W Alternator Charger takes care of this by reverse charging the starter battery to sustain those 12v accessories (in addition to the ones plugged directly into the Delta 3 Plus) and keep it at a healthy voltage. The SwitchPros also has a user-defineable cut-off voltage that you can set to prevent those accessories from over-depleting the starter battery.

 

[mcd_ovrlnd]

Similar setup but using Bluetti Charger 2 and DC hub. Mine is installed in the back.

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