Customer Question: I want dual-batteries, what do I need?

Customer Question: I want dual-batteries, what do I need?

Wagan Tech5/ 2/23

by: Justin gray

"I want to run a dual battery set-up in my work/overland truck; what do I need to get it done right the first time? Also, is it possible to make this future-proof (like I can upgrade stuff if needed later)? Please make this as easy as possible, I'm new to this! ...I also want to add an inverter in the future."

Here's a list of what you'll need:

  • Battery
  • DC-DC Charger
  • Fuses + fuse holder
  • Tools
  • Wiring + connectors


  • Power Inverter
  • Solar Panel



This is an important piece of the equation. You'll want a battery that can handle your power needs. Sometimes the space available to add a second battery is limited; I will always suggest to get the biggest battery that will fit.

Any battery chemistry is acceptable depending on your needs/wants; SLA (Sealed Lead Acid), Flooded Lead-acid, Gel, AGM (Absorbed Glass Mat). Calcium, LiFePO4 Lithium Iron Phosphate batteries

Do you have to match the battery that is already in the vehicle? No, that is not necessary.


  DC-DC Charger

Getting the right charger for your needs is easy as most people only need the 25A version.

No solar panel will be used: If your battery is going to be 100Ah or less, go for the 25A charger; if greater than 100Ah, go for the 40A version.

Solar panel will be used: If the combined solar panels are 375W or less, the 25A model is ideal. For systems up to 600W, the 40A is the best choice.

*Note: If the battery or solar panel you are using crosses either threshold, go with the 40A charger.



Both DC chargers require 2 fuses for installation. We recommend an ANL type fuse or a bolt-down fuse.

Blade-type fuses are not recommended as they can result in a high resistance connection which causes excess heat and may damage the fuse holder and/or the wiring. Self-resetting circuit breakers are not recommended as they may trip prematurely due to the heat generated by the current flowing through the wires.

Our 25A DC-DC Charger requires two: 40A fuses

Our 40A DC-DC Charger requires two: 60A fuses

  Fuse Holder:

This device securely attaches the fuse to the wiring and is needed to protect the fuse from anything that can interfere with the electrical connection.



Typical hand tools you'll need are:

  • Wire cutters
  • Wire strippers (or a knife)
  • Crimping tool
  • Adjustable wrench 

Wire cutters will be needed to cut the wire to length.

The wire strippers will remove the protective sheath that covers the bare wire - you'll need to remove the sheath in order to attach the wire connectors.

A crimping tool is needed to attach the included connectors to the wire.

The adjustable wrench is used to affix your bolt-down/ANL fuse to the holder assembly.


  Wiring + Connectors

The Wiring size (aka: wire gauge) needed is determined by how long it is from the DC charger to the battery (length of run). If the wiring is a shorter distance, it can be a smaller gauge. You can use a string to measure how long the DC charger installation area is from the battery.

To prevent heat buildup and loss, be sure to use the correct size wire! Reference the chart below for correct gauge (AWG) wire you'll need:

wire gauge chart


Our DC chargers come with butt connectors that you may use to join wires. You will also need the appropriate size ring terminals to connect the second battery and fuse holders to the wiring.


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