Thursday, December 8, 2022


Charging chassis battery through a lighter socket?


By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received from a reader while he was serving as’s technical editor.

Dear Chris,
Because our chassis battery does not charge when we are plugged into shore power, we plug in a small 12-volt solar panel and set it on the dash when we are parked for extended periods of time. We test periodically and it seems to be providing a trickle charge to the chassis batteries. Do you know whether there are any negatives to doing this? —Phyllis and Lamont, The Cooking Ladies

Dear Phyllis and Lamont,
Thanks for writing in. Always good to hear from The Cooking Ladies!

These chargers are fine as far as they go. They usually have small capacity (<4 watts) and will trickle charge an already charged battery to keep it maintained. They are not designed to charge a dead battery, however, and can only supplement a small drain on the battery.

Courtesy Xantrex

If you have a need for more charging capability, installing a battery maintainer may be a better choice. Xantrex makes the Digital Echo~Charge which detects when the house battery bank is being charged and directs a portion of the charge current to auxiliary or starting batteries. The charger current offered by the Digital Echo~Charge is limited to 15 amps; however, that is sufficient to keep both sets of batteries where they should be.

Hope this helps!

Editor: the Xantrex Digital Echo-Charge is available on Amazon.


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Richard Smith
6 years ago

The Xantrex Digital Echo~Charger is way more than what you need to spend for this task. I recommend either the Trik-L-Start or the Amp-L-Start device which accomplishes the same task at a reasonable price.