Voltage drop

better days · May 30, 2024

2018 ram 1500 hemi.
Twice now both times while at stop light the battery voltage dropped and went right back to normal. It dropped well below half and right back up.
The battery is about 2 years old.
Any ideas?

fratzog · Jun 3, 2024

A quick voltage drop is not likely to be a battery issue. It's more likely to be a connection issue. As in a bad ground, or alternator connection. Next time it happens, observe the lights and engine rpm. Are the lights dimming when the drop occurs? is the engine rpm changing? You could have an alternator going bad. Or a bad battery connection. It could even be the gauge itself. You just have to do some detective work, and follow the symptoms.

Tominator223 · Jun 3, 2024

Check connections.

turkeybird56 · Jun 3, 2024

Just a thought: the VR (voltage regulator) in the alternator could be going bad also, something to think about.

Jeepwalker · Jun 3, 2024

Could be an alternator too. Bad diode... worn out brush.

Push all the fuses down in the fuse box (they can 'work up'), and make sure your tk's battery connections are 100% good. Check the connections on the main fuses up by the battery connector...loosen-tighten..wiggle. Wiggle alternator connector and make sure the back wire (behind the Alt) is tight.

Then swing by the parts store and have them read the vehicle's codes (write down what any are). Maybe the vehicle registered a soft code. Then have the part's store perform a battery load test, which should be free, AND an on-car alternator test. That's all good info to start with and doesn't cost anything.

RamDiver · Jun 3, 2024

You might also start with a quick cleanup of the battery posts and clamps if it hasn't been done recently.

These are dirt cheap at $3 and a valuable tool to have in your collection.

https://www.harborfreight.com/automotive/battery-tools-accessories/battery-terminal-cleaner-94450.html

.

inuyasha-rules · Jun 3, 2024

I believe the hemis with mds system also shut off the alternator at idle if there isn't a large load on the electrical system. On all 3 mds hemis I've driven, there's a voltage drop from 14.whatever, down to the battery resting voltage of 13.5, and if it idles long enough for the voltage to hit 13.2, it kicks the alternator back on. All this in the name of fuel economy...

dojofo · Jun 3, 2024

As it already been mention it could be a connection or alternator issue or ressitance in the plus or ground side of your batterycables. Check your battery terminals make sure you don't have anything loose or corrosion build up at the battery postor where the cables run to. The plus will go to starter and alternator the ground should go to the engine block or bell housing. Test the battery and the alternator if you have the tools to do so. You can also do voltage drop test across the B+ and grounds with a multimeter that would give you the best idea of what's going on with your wiring/cables

Voltage drop

better days

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fratzog

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Tominator223

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turkeybird56

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Jeepwalker

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RamDiver

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inuyasha-rules

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dojofo

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