DC to DC Battery Charger (VS.) battery isolator?!

DC to DC Battery Charger (VS.) battery isolator?!

Wagan Tech7/29/23

by Justin Gray

One of the most common questions we receive in regards to battery charging is:
"Why should I get a DC-DC Charger instead of a battery isolator"?
The answer is actually pretty simple!

Battery Isolator
A battery isolator aka "Automatic Charging Relay" (ACR) is basically a gate. It opens up to allow current to flow to your second battery and closes to stop your second battery from draining your primary (starting) battery. It is simple and useful, but has long-term use drawbacks.

  • It is not a battery charger. It may seem to "recharge" your battery, but it actually is not a battery charger per se. All they do is simply let the current flow. A modern battery charger will monitor the battery and adjust the current to optimize the charge to match the needs of the battery.
  • Battery isolators don't allow your battery to get a full-charge. Due to line loss, limitations of your vehicle's alternator/charging system, and the inefficient design of an isolator, your battery will never be fully charged; this will degrade it's overall lifespan and usefulness over time.
  • You can't mix battery chemistries. If you're using a standard battery (SLA Sealed-Lead Acid, AGM Absorbed Glass-Mat, Maintenance Free, Flooded, Wet Cell, VRLA Valve-Regulated Lead-Acid, Gel, Standard Lead-Acid, Vented, Deep Cycle) and want to add a Lithium battery (LiFePo4, LPF) to your system, you can't do it with a standard isolator.


DC to DC Battery Charger
A DC to DC battery charger is a device designed to charge an auxiliary battery (2nd battery) from the vehicle's main battery while the engine is running (or from solar while the engine is off). It converts the vehicle's alternator output (DC voltage) to a regulated and appropriate charging voltage for the auxiliary battery. This ensures that the auxiliary battery receives the correct charging profile, allowing it to charge efficiently and safely.

  • Efficient charging: DC to DC chargers provide a more controlled and regulated charging process, optimizing the charging cycle for the auxiliary battery and fully charging it.
  • Multi-stage charging: offers multi-stage charging, including bulk charging, absorption, and float stages, similar to the process of a standard battery charger.
  • Battery protection: DC to DC chargers typically include safety features like overcharge protection and reverse polarity protection.
  • Sophisticated battery management: can handle different battery chemistries and offer configurable charging parameters.

In summary, a DC to DC battery charger is a more sophisticated and advanced solution for dual battery systems. It provides efficient charging, multi-stage charging profiles, and fully recharges your battery. On the other hand, a battery isolator is a more straightforward device that doesn't regulate the charging process but automatically connects the batteries for charging. The choice between the two depends on your specific needs, budget, and optimization you want for charging your auxiliary battery.

Take a look at our sophisticated DC-DC Battery Chargers:

25A DC-DC Battery Charger

40A DC-DC Battery Charger


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