Resting Battery Voltage

hodges97

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I tow my Ranger 4 down behind a motorhome. I pulled up behind the coach to hook up as usual. (the truck had been driven a good bit the day before). When I put my Break Buddy in as my final part of my hookup procedure, it wouldn't allow the compressor to start. Break Buddy has good service so I called them. Somebody actually answered the phone. He said the error message I was getting was low voltage. I said, OK, I will check but didn't believe him. Well, sure enough, the battery was at 12.1 Volts and the dedicated plug in the cab was at 11.95. I started the motorhome which runs a cheater wire to my battery and in 10 minutes or so, everything worked.

For 3 days, I checked voltage. Sometimes it was as high as 12.6 volts. Some times is was as low as 12.05 volts. Sometimes the voltage was the same at the battery and the plug in the cab. Sometimes the voltage was .1 volts lowere in the cab.

I'm assuming I've got a parasitic draw or a bad battery. This thing is 5 months old and shouldn't be doing this.
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SemperVee

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I tow my Ranger 4 down behind a motorhome. I pulled up behind the coach to hook up as usual. (the truck had been driven a good bit the day before). When I put my Break Buddy in as my final part of my hookup procedure, it wouldn't allow the compressor to start. Break Buddy has good service so I called them. Somebody actually answered the phone. He said the error message I was getting was low voltage. I said, OK, I will check but didn't believe him. Well, sure enough, the battery was at 12.1 Volts and the dedicated plug in the cab was at 11.95. I started the motorhome which runs a cheater wire to my battery and in 10 minutes or so, everything worked.

For 3 days, I checked voltage. Sometimes it was as high as 12.6 volts. Some times is was as low as 12.05 volts. Sometimes the voltage was the same at the battery and the plug in the cab. Sometimes the voltage was .1 volts lowere in the cab.

I'm assuming I've got a parasitic draw or a bad battery. This thing is 5 months old and shouldn't be doing this.
The FORD is controlling your charging.. See my post..https://www.ranger5g.com/forum/threads/battery-voltage-is-questionable-what-is-yours.7239/
 
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hodges97

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Thanks for the reply. I went thru that thread before I posted. I saw lots of theories in that thread but was there any resolution? If there was, I didn't find it. A battery tender and or a LI jump box doesn't really suit me as a solution.
 

charwest

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is one of your accessories or tow devices eating power after ignition is off? i noticed my start up voltage was a little lower than i expected and wondered if it might be because we leave a cell booster plugged into a powerpoint. not sure if that was my problem, or if it was even a problem, but i used forscan to change my powerpoint-on interval after removing key to 5 minutes instead of the stock 75 minutes. obviously if you have anything sipping power for a full 75' after key out that could cause the battery to run lower than expected.

i agree there is some magic behind-the-curtains stuff with the ford BMS /charging stuff, but if you are actually being effected with inability to power your devices that would be a bummer.
 
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hodges97

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The good news is I have an excellent Ford service department a mile from my house. The ranger is a spare vehicle and I told the Service Manager to take it and keep it till they had resolution. I think there's a chance it's the battery. There is nothing plugged in anywhere when it overnights. It's odd.
 


painter1

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The good news is I have an excellent Ford service department a mile from my house. The ranger is a spare vehicle and I told the Service Manager to take it and keep it till they had resolution. I think there's a chance it's the battery. There is nothing plugged in anywhere when it overnights. It's odd.
Would be good if they load test the battery - at least once.

I'm glad you mentioned resting voltage in your OP. That's important but is undefined. Ideally instructions for resting and using voltage for soc would come from the specific battery mfr. Consistency in measuring conditions would be best for comparisons.

If you do have a parasitic draw, that can skew the voltage reading if the battery is measured while under any load. If that parasitic draw is intermittent or variable while voltage is measured it could further muddy the waters. Best if the battery is disconnected for the resting and measuring period, but them you may not want to reset any electronics.

One point I haven't seen mentioned is battery temperature effect on soc reading. Best charging voltage is also temperature compensated.

In short, batteries and charging is a rabbit hole, one I've spent too much time in. Fortunately they usually work just fine with out any minding.

Good luck with it !
 

cocheese72

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Mine has been under 12.6 volts, unlike other vehicles I have. Not sure how low it has gone, but I have seen it at 12.4 volts sitting for maybe 2 days. I have gotten warnings from the Ford Pass app saying remote features have been disabled. The truck has always started though. I noticed this week that auto-stop had ceased working. I have not been driving much and when I do it is 2.6 miles one way, then back. I believe this is not allowing the battery to fully charge back up.

I put it on the tender this week and it took a long time but it went from charging to absorption, then full charge. This allowed auto-stop to work again. I am trying to avoid messing with dealers if this is normal behavior.
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