Voltage drop when parked

[FAB Cruiser]

I'm trying to figure out if I have an issues with parasitic voltage drop.

Over a 7 day period with a brand new battery, the voltage dropped from 12.7V to 12.3V. So it's losing 0.4V per week. When driving, the voltage sits at a steady 14V+

When the car was new, I drove it more and never noticed an issue. Now I'm driving it less and I can have a starting issue if leaving it too long (say over 10 days to two weeks). However, during COVID lockdown, it is was parked away from home for 7 weeks and started first click!

In terms of any potential parasitic drains, I did have the common issue a couple of years ago with the drivers window dropping up and down an inch every now and again. The garage cleaned the connectors and the issue went away.

Any feedback appreciated.

Cheers
David

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[Skye]

Changing the battery after eight years, I can see that. It had a good, long life. I provide some tips below. If you continue to believe you might have a charging system issue, check with a dealer or service shop; have them do a running test of the alternator, then a battery load test.

Most modern cars, even though they could be "off", they're not really off. For example, a sitting S550 will continue to communicate status to Ford (Telematics, Ford Pass App), from time-to-time.

I can think of a few things you can do do support the battery and the electrical system better:

- You recently installed a new battery. If you haven't done so already, perform a Battery Management System (BMS) reset. The S550 has an electrical management program; it understands the battery will be less-and-less efficient over time, due to wear and tear of the internals. The car's BMS will adjust how it charges the battery as it ages. With a new battery, you need to reset the charging system. A BMS reset does that

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

- Go through the car's communications preferences and disable everything linking the car to the outside world, mainly, bluetooth and wireless, if enabled. Many enjoy using these features linking their phones and entertainment systems, but they use power

- If not doing so already, lock the car when not in use. If left unlocked, Bluetooth continues to be available, looking for or being ready to accept the fob

- Purchase and use a Faraday pouch for the fob. Locking the car helps prohibit communication, from the car. But the fob is the other half of the equation. Left in the open and moved, it attempts to talk to the car, potentially waking it up, and initiating communications. Further, it's a good security stance: using a Faraday pouch prevents a relay attack and theft of the car. I use a pouch from SLNT, but there are multiple vendors

https://slnt.com/?srsltid=AfmBOorsQOcntgAsP5_vMQKs5zVx0abqBTsRFhlJr9jqpdZI4lZd3aoB

- Consider installing a battery tender, to maintain and exercise the battery when not in use. While tenders do provide a top-up charge, an equally important function is they condition the battery, exercising so it is at it's best

https://www.ford.com/product/ford-performance-50-smart-battery-charger-maintainer-p2939588882

I have NO idea why the UK version of ^ this unit is so expensive. Check with you're local dealer. These units are made by CTEK, a popular tender company.

https://www.ctek.com/charging-solut...RP21a_7Mx99IW9kCN9l0umT58KUjxdiE4OIRoJikvD-or

"Battery Tender" brand tenders are very popular.

https://www.batterytender.com/?srsltid=AfmBOoobA5GF5qiMxxVWL94evImv8SzRJrZBdEP0jvLv7amDvnYJVwR4

It's pretty easy to install one of these units. They can be setup in such a way so as to connect from a plug without popping the bonnet.

https://www.mustang6g.com/forums/threads/batter-tender-battery-connection.172738/

Finally, when you do drive the car, it's best to drive long enough for everything to heat-up, the fluids to circulate well. While the occasional short trip is OK, it's best to avoid them.

 

[FAB Cruiser]

Thanks for the great advice. I’ll run through the list.
I do have that Battery Conditioner (branded CTek) but I don’t have permanent mains power to my carport currently, so only use it with an extension lead on an ad hoc basis, which I appreciate defeats the object.

 

[sk47]

Purchase and use a Faraday pouch for the fob. Locking the car helps prohibit communication, from the car. But the fob is the other half of the equation. Left in the open and moved, it attempts to talk to the car, potentially waking it up, and initiating communications. Further, it's a good security stance: using a Faraday pouch prevents a relay attack and theft of the car. I use a pouch from SLNT, but there are multiple vendors

Hello; I have a bag which once held coffee. Cleaned it out and put my cell phone in it. The phone would not get calls when in the closed bag. Note-it is the foil lined sort. This idea is sound.

I do not know how far away the car can sense a key fob. I do know of folks who can start a car remotely from inside a house.

Side note- My brother bought a pontoon boat a few years ago. He kept having problems starting it after it sat for a week or more. I went with him one day and noticed a battery cut-off switch near the battery. Found out he was not using that cut-off switch. Now that he uses that switch each time the boat can sit a long time and will crank good.
I suspect a cut-off switch may not do so well on a modern car and may well mess with ongoing systems. What do those who store over winter do?

 

[Skye]

Hello; I have a bag which once held coffee. Cleaned it out and put my cell phone in it. The phone would not get calls when in the closed bag. Note-it is the foil lined sort. This idea is sound.

Thieves in stores do same, to bypass the scanners at the stores exits. Radio waves will pass around or be reflected away from the bag.

I do not know how far away the car can sense a key fob.

There are several environmental variables, but a general distance of at least 30 ft / 10m, if not more. I routinely pick up signals from across the neighborhood. Most do not realize these interfaces (bluetooth and wireless) are on by default, from washing machines to the thermostat in their homes.

I suspect a cut-off switch may not do so well on a modern car and may well mess with ongoing systems. What do those who store over winter do?

While an "on/off" switch could be installed on a modern car, there are aesthetics. The tender will work fine while the car is in storage: connect and walk away. For those storing cars long-term without electrical access, many disconnect the battery leads or remove the battery all-together. While there is memory if left off for a long period, it will not affect the operation of the car. After putting a charged battery in, the car will prime the fuel pump and system as the Driver door is opened, the car starting immediately once the "start" button is pressed.

 

[overheadmanifoldsprocket]

This might not help you as your car is a 2017 model, but I've noticed hardly any battery power loss when my car has been sat for 2-3 weeks ever since I switched off keyless entry. But unless anyone knows a way around it, I don't think that's an option on the pre-facelift unfortunately.

 

[ice445]

I can never get an accurate reading on my car with a multimeter unless I disconnect the battery from the car

 

[FAB Cruiser]

Hi all,

I'm restarting this thread as things went from bad to worse...

I followed the advice to minimize battery drain. I also disconnected my tracker. However, with a brand new battery fitted, It still suffered an overnight voltage drop and within a few days it needed a charge to start.

Driving the car, I was sometimes seeing a fluctuating voltage on the dash but most recently I had a steady 14.3V

Now, the car won't start at all! Even after a full charge. Currently at the battery (connected to car) I get 13.4V on a meter. On the dash I get 12.4V.

I did try too many times and got the 'Cranking Time Exceeded' but that has now cleared.

I'm booked it at the excellent Hendy Performance next week to get it professionally looked at, but at the moment it looks like I'm going to need a recovery truck.

I'd appreciate any further suggestions on causes of parasitic battery drain as well as tips to get it started so I can at least drive the 20 miles to the garage.

Many thanks again...
David

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