June 24, 2024

Is your converter/charger damaging your batteries?

Do your batteries a favor and upgrade your stock charger/controller to a smart charger/controller. You’ll charge batteries faster and extend their life.

Is your converter/charger damaging your batteries?

If your RV has an older single-stage converter/charger unit installed, then you should seriously consider replacing it.

Single stage converter/chargers can shorten the lifespan of your batteries by overcharging them. Newer converter/chargers have multi-stage charging capability and are recommended for modern RV deep cycle batteries. Many can even be programmed to the exact manufacturer recommended charge settings. There are even models that support the unique requirements of lithium deep cycle batteries.

What does the converter/charger do?

First of all, the converter/charger will be powered when connected to a 120 volt shore power connection or generator. It has two functions as the name implies. First, it converts AC electricity (from the shore power) to 12 volt DC electricity needed to keep your lights, and other 12V equipment running. Secondly, it is a battery charger that will recharge your deep cycle house batteries.

What’s wrong with older single-stage converter/chargers?

Battery manufacturers have specific guidelines for properly charging their batteries. Lead-acid batteries (flooded or AGM) require a four-stage charging cycle. Each stage has specific voltage and current profiles designed to get the battery safely to a full-charge without overcharging it. Lithium batteries also have specific charging guidelines set by their manufacturer.

Single stage chargers simply push a fixed voltage into the battery at all times. This often causes these problems:

  • They do not supply sufficient charge voltage during charging which may tripple the charge time or prevent your batteries from reaching a full charge
  • When batteries are fully charged, they keep pushing a higher voltage into the batteries which can cause overcharging, buid up of heat and gas, and a significant reduction in lifespan.

When these problems occur, you may also find that your batteries aren’t holding a charge and frequently need replacing. If this is the case, it’s highly recommended to upgrade to a four-stage converter/charger.

How to Replace The Old Converter/Charger?

I upgraded the stock converter/charger in my RV with a charger that has multi-stage charging. Swapping out the old with the new charger was as simple as unscrewing a few screws and moving some wires.

After a quick visit to the Progressive Dynamics website, I found a drop-in replacement for my Parallax 7155 converter/charger unit. It was the PD4600 series converter/charger.

Progressive Dynamics PD4600 Four-Stage Replacement Converter/Charger (Amazon.com)

The primary advantage of the new unit is the smart battery charging feature. When the batteries are low, the charger kicks into bulk charge mode (around 14.4 volts) and gradually decreases the voltage as the battery reaches a full charge. When connected to shore power, my batteries were able to reach a full charge within 2-3 hours. With the old charger, the charge voltage was too low (13.8V) to ever fully recharge my batteries.

NOTE: For best results, contact your battery manufacturer for recommended chargers that are compatible with their batteries. If the charger is programmable, they will also be able to tell you the recommended settings for each charge phase.

Replacing the original charger with the new one was a breeze. You can see for yourself in this video.

Does It Work With Lithium Batteries?

The PD4600 series converter/charger is not designed to charge lithium batteries automatically. There is a manual workaround.

Pressing the little button on the DC distribution block will manually switch it a specific charge phase. I used this feature to force it into bulk mode. This works, but you’d have to manually monitor the charge voltage then switch it back to normal mode when it reaches full charge. But there is a better way.

Progressive Dynamics now makes Lithium compatible chargers. After upgrading my batteries to LiFePO4 lithium batteries, I needed to also upgrade my charger. The one I installed was the Progressive Dynamics PD4655LIV model designed for lithium batteries. Here’s a link to the site where I bought mine.

Replace RV Converter/Charger for Lithium - RVWITHTITO

Installation of the PD6455LIV was very easy. It looks identical to the other model and the wiring also matched exactly. All that was needed was to remove the old one and wire up the new one.

After installation, the lithium batteries started charging automatically.


Having used these Progressive Dynamics replacement chargers for many years now, I can tell you that I’ve never had a problem. They’ve worked great. But be sure to select the unit designed to replace your existing charger. It’s not a one-size-fits all replacement.