What Size Battery Charger Do I Need For My Off-Grid Setup?

If you want to live or travel off-grid, you need to get one thing right first: the right size battery charger. So, how do you know which size charger you need?

Work out your charger size based on the following factors:

1. Battery Type

For lead acid deep cycle batteries (AGM or Gel), ideally you want a charger with an Amp output of 10-20% of the total battery bank. So, for a 100Ah battery, you would buy a 20Amp charger.

Different battery types have different requirements for charging. That’s because the battery chemistry reacts differently when being charged.

For Lithium and Lead Crystal batteries, the charger to battery ratio is based on 30% for maximum performance and lifespan. That means a 200Ah requires a 60Amp charger.

2. Charge Profile

This includes the Maximum Charge Voltage and Maximum Charge Current.

The Maximum Charge Voltage is the highest acceptable charge voltage the battery can take to charge.

This Maximum Charge Current is highest charge current that the battery can receive when charging.

You must charge the battery within the specifications of the maximum charge voltage and charge current. If not, you can severely reduce the battery’s health and life.

Let’s say you have a 200Ah Lithium battery with a maximum charge voltage of 15.5V and a maximum charge current of 150A. The charge profile must suit these specifications.

3. Multiple Charging Sources

Most RV’s have multiple charging sources: mains, solar and vehicle charging. If you have the ability to run multiple charging sources at that same time, these should not exceed:

  • 35% of the battery capacity combined for Lead Acid/AGM
  • 30% for Lead Crystal
  • 60% for Lithium

The good news is a lot of chargers have the ability to dial down the current output of the charger.

Take the Enerdrive ePOWER range. Both the AC and DC2DC chargers in this range have adjustable current outputs. This allows for installing a bigger charger at the start, which is ideal if you think you may increase your battery capacity or number of battery banks at a later date. No need to buy another charger down the road and waste money. Plus with this range you can also select the type of battery you have – bonus!

Enerdrive eTips – Enerdrive ePower Battery Chargers

Another thing to note, is that when powering your battery charger from a generator you need to ensure that the battery chargers power draw doesn’t overload the capacity of the generator. For example, an Enerdrive ePower 60Amp battery charger can be dialled down to allow you to run it off a small 1000W inverter.

4. System Voltage

Your charger output needs to be suitable for your system voltage.

If you have a 12V system, choose a 12V battery charger.

For a 24V system, you need a 24V battery charger. You get the gist…

Different Types of Battery Chargers:

AC to DC

AC to DC chargers are designed to charge your battery from a generator or mains power. So, rather than using your generator’s 12V supply, use a regulated charger and plug it into the AC source on the generator.

Why? Because it provides faster charging and wastes less fuel. That’s a big benefit if you’re in a remote camp spot, hours from the nearest fuel stop!

My Generator’s Top Picks:

DC to DC

A DC2DC battery charger is like a smart charger for your 12V system. The best thing about a DC to DC charger is that it will boost charge into your battery while you’re driving. It also acts as an isolator, so your starter battery doesn’t go flat when you stop for a while.

My Generator’s Top Picks:

For more details on AC and DC Battery Chargers check out our Camping Battery Chargers Buyer’s Guide

Battery Management Systems

Another option is a battery management system. This provides a complete system for charging auxiliary batteries, so you can be confident they’re always fully charged.

For example, the Redarc Manager30 charges an auxiliary battery from the vehicle on the move, while also being a 240 volt charger, a solar regulator, a battery isolator, and a load disconnect controller.  It has AC, DC and solar inputs, and is compatible with all vehicles and alternator systems, including variable voltage alternators. It also features a remote battery monitor.

What is a REDARC Manager30 and What Does It Do?

Need more advice on choosing the right battery charger size for your off-grid set up? Our team is ready to help. Get in touch!

DISCLAIMER* Please note, this advice is general in nature and we strongly recommend consulting the product manual and where relevant, a professional installer.

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