2011 Silverado electrical drain

edpare · December 27, 2020

I have a 2011 Silverado 2500 HD LZ with Duramax diesel. I use it to pull a travel trailer. When not in use, it is parked for weeks at a time. I often find the batteries run down and I can’t figure out why. I reckon the radio receiver for key fob commands must use something, but enough to pull the batteries below 12.6 volts in two weeks? I keep a 2-amp trickle charger on it but it can only just barely keep them at 12.8 V, much less 13.6. Any ideas?

davester · December 28, 2020

13.6V? A charged battery is 12.6V, it can be slightly over that for awhile after it's been on a charger. If there is 13.5V across the battery terminals of a 12V car battery, there's an external charger applying power to it.

MORSNO · December 28, 2020

9 hours ago, davester said:

13.6V? A charged battery is 12.6V, it can be slightly over that for awhile after it's been on a charger. If there is 13.5V across the battery terminals of a 12V car battery, there's an external charger applying power to it.

This is correct. 12.6v is fully charged for a 12v lead acid wet battery. An AGM battery will read 12.8v. Anything higher is when a charger/alternator is charging it. FYI, 12.3v is 50% charged, anything below 12v is almost unusable and considered dead. Those of us who dry camp with truck campers watch our camper battery voltages.

edpare · January 1, 2021

Sorry I wasn’t clear. The system goes from 12.6 to 12.3 or less in only two days. A corollary symptom is that my 2A trickle charger used to be able to maintain 13.6 on float but can no longer do so on this battery. Charger works fine on other batts. Thus, I have an unknown electrical drain.