New Battery Installed - Weird Charging

[rocket rod]

Howdy All

Yesterday I had my OEM battery (D4 MY16) replaced under warranty through Land Rover Assist (they subcontract RAC WA). They replaced it with an RAC branded battery, manufacturer unknown and 2 year warranty. I'm not necessarily fussed about that but I noticed today when driving the charging of the battery didn't seem right.

Before my battery died my in cab volt meter showed 14.7V when driving, full revs or idling. Now with the new battery, when driving it shows 12.4V but when I take my foot off the pedal (still coasting) it goes up to 14.7V. When I have the lights on, driving 13.1V, foot off 14.7V. I also have a Traxide system and the voltage on that battery changes the same way too.

I used my GAP tool to run the Replace Battery rountine. I'm not sure whether the BMS needs a little time to work how to charge the new battery or not or does the OEM battery have some smarts in it that are needed by the BMS to function properly?

Thoughts?

[PhilipA]

AFAIK that is what they are supposed to do with a good battery.
Saves fuel.

Regards Philip A

[Tombie]

Yep. That’s how it should behave.

[rocket rod]

Thanks for the feedback guys. BTW the resting voltage is 12.7V and the car starts better than before so I'll assume all is OK.

[Mike57]

The voltage increases when braking, that is normal. Known as regenerative braking, the extra load adds to the the engine braking and recharges the battery at the same time. 12.7 volts is a good battery.

[rocket rod]

The 14.7V appears when I take my foot off the pedal and the engine returns to idle when say approaching lights, before braking. It may happen during braking as well but didn't check.

[drivesafe]

Spot on Rod, the alternator voltage is controlled by the position of the accelerator pedal, not the brake pedal.

[Mog60]

A timely question from Rod (we did the CSR with you last year Rod) as I am in a similar situation and am really wanting to understand the normal range of voltages that my 2014 Discovery IV should be producing. I have just replaced my original AGM cranking battery, which was four years old, with an AGM Varta G14. I also have a Traxide dual battery system installed and used my GAP IID tool to reset the battery management system for the new Battery. What I experienced after installing the new (fully charged battery) was that the Traxide in-cab-module LED would flash (e.g. 5 red 1 green) even when driving and intermittently glow dull, randomly going back to flashing and cycling through this sequence. I rang Tim for help (many thanks Tim) and he suggested that I might benefit from a BMS patch which was duly done by my LR dealership last week. I also asked them to check the alternator over and they reported that it was fine. However, the BMS patch does not seem to have made any difference to the in-cab-module LED often flashing whilst driving. This flashing seems to start once the batteries have had a chance to charge up. My cigar lighter voltmeter shows that the voltage varies a lot (in a similar way that your does Rod). Overall, whilst driving the voltage changes almost unpredictably (to my novice eyes) sometimes 13.1v sometimes 12.5v or lower and from memory, other voltages too. Like Rod’s, the voltage generally goes up to 14.7v or so whilst engine breaking but confusingly today coming down a long steep hill using engine breaking (towards the end a 7 hour drive) the voltage was around 12.8v. It seems to me that the Traxide in cab module LED will start flashing if the voltage goes below 12.7 or so. My batteries seem to be charging ok (both now sitting at 12.64v (5 hours after my long drive) but..... I don’t know what range of voltages is normal and also why my in cab module should now be flashing when it didn’t do this before and the LED formerly glowed dimly whilst driving to avoid distraction to the driver.

Any assistance in understanding this would be very gratefully received. Peter

[Mike57]

Your range of voltages and the variations (almost random) seem to be the same as my 2014 TDV6. I had the BMS update applied in about 2015 when I was getting low voltage warnings too often but the battery was fine. i don't have a dual battery permanently installed.

[Mog60]

Thanks for your reply Mike. It's good to have your input. I have been doing a bit more searching around and this thread from 2015 seems to have some useful information but I am still reading through it....DC-DC charger- which one?. I still have a lot to learn
Peter

Your range of voltages and the variations (almost random) seem to be the same as my 2014 TDV6. I had the BMS update applied in about 2015 when I was getting low voltage warnings too often but the battery was fine. i don't have a dual battery permanently installed.