'17 LTZ charging system question

rav3 · May 19, 2021

Guys, I have a question for you on out charging systems. My truck is a '17 Double door LTZ with Max towing, 5.3l V8 & 6L80e six speed transmission & a KG4 150 AMP alternator with 37k miles and original battery. Truck was built in 12-16. Monday I hook up my 6amp battery charger that charges automatically; (reduces AMPs as the battery charges up & will go to '0' AMPs when fully charged. I left it on for about 4 hours, at which time it had dropped down to less that 2 AMPs. Today, took the truck for a drive & noticed that the system Volts was running 12.3 to 12.4....Hummm. Stopped at Lowe's for 15 mins & noticed that after starting the engine, volts were 14.5v for a short while & then dropped back to 12.3-12.4 (I have a digital unit that I plug into the cigarette lighter socket & it shows me what the system volts are).

I then drove thru the mountains for 45 mins or so & the volts stayed at the 12.3-12.4. Usually, I'll see the volts run from 13.8 to 14.5. With 12.7 being fully charged battery, did I mess up the battery regulating unit that sits on top of the battery or is this normal?

MikeBMW · May 19, 2021

Totally normal. The computer controls alternator output so as to not overcharge the battery.
A slightly lower battery will receive a higher charge while a fully charged battery will receive a lower charge.

Edited May 19, 2021 by MikeBMW

JimCost2014 · May 21, 2021

Ooooh, I get to post this again, your truck is performing as designed.

Battery Load Management The vehicle has Electric Power Management (EPM), which estimates the battery's temperature and state of charge. It then adjusts the voltage for best performance and extended life of the battery. When the battery's state of charge is low, the voltage is raised slightly to quickly bring the charge back up. When the state of charge is high, the voltage is lowered slightly to prevent overcharging. The voltmeter gauge or the voltage display on the Driver Information Center (DIC), if equipped, may show the voltage moving up or down. This is normal. If there is a problem, an alert will be displayed. The battery can be discharged at idle if the electrical loads are very high. This is true for all vehicles. This is because the generator (alternator) may not be spinning fast enough at idle to produce all the power that is needed for very high electrical loads. A high electrical load occurs when several of the following are on, such as: headlamps, high beams, fog lamps, rear window defogger, climate control fan at high speed, heated seats, engine cooling fans, trailer loads, and loads plugged into accessory power outlets. EPM works to prevent excessive discharge of the battery. It does this by balancing the generator's output and the vehicle's electrical needs. It can increase engine idle speed to generate more power, whenever needed. It can temporarily reduce the power demands of some accessories. Normally, these actions occur in steps or levels, without being noticeable. In rare cases at the highest levels of corrective action, this action may be noticeable to the driver. If so, a DIC message might be displayed and it is recommended that the driver reduce the electrical loads as much as possible. See Battery Voltage and Charging Messages 0 155. Battery Power Protection This feature shuts off the dome and reading lamps, if they are left on for more than 10 minutes after the ignition is turned off. The cargo lamp shuts off after 20 minutes. This prevents the battery from running down