Ranger Mods

Nov 2015 PX2, Smart charge turned off.

Charge voltage usually sits at 14.3 to 14.4.

Yesterday the Ranger decided to charge at 14.9 to 15v - Ultragauge give a voltage too high alarm, voltage confirmed by plug in voltmeter.
After a series of short 20 min runs with short rest between runs the voltage on each run dropped down 14.6 to 14.7 after 1st run, 14.5 after 2nd run and 14.3 to 14.4 (normal) after the last run with a rest before restart.

This morning charging at 14.7v.

Battery only a few months old.

A week ago the Ranger was at the Ford dealer having the crank angle sensor replaced so battery disconnected for a while.
The dealer left a lot of DTC's in the modules from testing stuff, mostly communication between module errors, so I cleared the DTC's using Forscan.

Charge voltage was OK after doing this which was a week ago.

Anyone have any idea, I do not think there is a fault as such and expect it to go back to normal, I have read on another forum of a Ford Focus doing exactly the same thing but no explanation why.

regards
Max

Lots of dual battery discussion around so you might want to search a bit. There's one thread here: viewtopic.php?f=12&t=456 but I'm sure there's other mentions etc. Do you actually have dual batteries? Current thinking is it might be a bad idea to have it enabled without actually having dual batteries. FWIW I never saw over 14.8 when I had mine enabled. Interesting that 15v is considered too high. From the small amount of research I did on these batteries they require rather high voltage to properly charge, up to 16v was noted in several sources.

If the battery was disconnected then perhaps the BMS needs to be reset? I'm sure Saeb will chime in with his thoughts.

I do have dual batteries, the 2nd battery is charged by a DCDC charger with the negative connected to the chassis.

I am not worried about the voltage too much but am interested in what the BMS is doing.

For 18 months the charge voltage has been around 14.3 to 14.4v and then the other day (as mentioned above) 15v at first but ramping down after short trips with a rest between them. The battery is relatively new and would have had close to full charge.

Today did a short 20 min drive, voltage at 14.7 for the whole drive, if you restart quickly the voltage goes back to 14.7v, let the car rest for an hour and restart, the charge voltage is 14.3 to 14.4v.

The ranger is locked each night so the BMS has plenty of time to sense the battery SOC.

I am curious if the BMS may be doing some sort of calibration, a web search has not found anything conclusive yet.

It is constantly monitored. It should also be rest when a new battery is installed.

With a DC to DC there is no need for dual battery mode.

I assume you have set the alarm in the UG for this voltage as an alarm? Pretty sure it was adjustable.

Basically by disabling the BMS you are doubling the SOC. It is never disabled at all really and not recommended to disable unless you have a second battery with a standard solonied setup.

Each to their own but long term batteries may not last as long or may boil in vehicles with disabled as such BMS.