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19 I-pace HSE Polaris/Fuji white with most options and a lot of accessories
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Discussion Starter · #1 ·
Disclaimer: I do not sell nor have any interest in products mentioned below. They are mentioned and pictured as reference material only. There are several products on the market that provide the functions mentioned. Readers may search for and purchase these or similar products at their own choice. Suggested search string "bluetooth 12v battery monitor".

These are not certified as scientifically accurate devices. Use them as a general guide for what is happening with your batteries, not as exact voltage reading devices. I found that voltages reported by them to be lower by about 0.7 volt from "Auxiliary battery voltage" reported in WattCat (datum supplied to Jaguar servers by the car). The devices snapshot the voltage readings and can vary by tenths of a volt at any given instant causing ripples in the data as you can see in the graphs below.

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Monitoring 12V batteries in EVs would be a wise thing to do. Failures can lead to being stranded, or in the worse cases having a vehicle stop in traffic even though the traction battery has plenty of power. Reference this thread for how to handle 12V battery failures.

As a chance at getting a heads-up to a weak 12V battery and get it replaced before there's a problem, one can add monitoring devices. Below I show adding devices that monitor the voltage and capacity of 12V batteries. They require a smartphone for an app that displays the information and can trigger problem notifications on the smartphone. They'll require a Bluetooth connection and location permission.

I already have devices of brand INEX in use on other 12V battery applications. The app for them is limited to 4 devices so I had to find ones that used a different app (or somehow figure out how to run two separate copies of the same app on 1 phone). I went cheap and got a different brand, Quicklinks, as shown below.
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The devices (regardless of brand) come with instructions for installation of the device, installation of the appropriate app, and how t use the app. Read the instructions carefully. I found installation of the first device is easy, but adding a second (or more) device to the app may not be as easy.

I installed one on the starter battery first as seen below. Using a 10mm socket tool, attach the positive wire (red connector) to the battery positive bus bar, and the negative wire (black connector) directly to the negative post clamp. This latter connection bypasses the BMS to prevent any potential interference from one to the other. Model year 2019 is shown. Model year 2021 and following will be slightly different.

Note the orientation of the positive connection. This allowed the red cap to be re-installed on the bus bar (not shown). I tucked the monitor further down before re-installing the cover too.
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For the auxiliary battery on pre-model year 2021 vehicles, attach the black connector to the negative post at the clamp for the ground cable, and the red connector to the 13mm nut attaching the fuses to the positive post bar. This latter location allows for re-installing the red protective cap. You may have to adjust it a little from what is shown in the picture as one of the cap's holding clips is located near this location. I had to adjust mine after I had taken this picture.
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I used the app to verify the device worked after I installed the starter battery monitor and followed the setup instructions. Then I installed the auxiliary battery monitor and used the app for its setup. You might want to install both monitors, if needed, and then use the app. The sequence doesn't matter and I don't know if it is any easier one way or the other.

Now that the devices are monitoring the batteries I can get the current state of charge/capacity and voltage for each. The app for these devices (and the INEX ones I have on other batteries) can produce a graph for each battery's voltage for a day. The devices will retain up to 35 days of data if you don't happen to look at app for some reason (eg. away on a business trip).
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Here's a day's graph for the auxiliary battery on my car. At the left, the car is sitting in the garage unattached to a charger. This was 12.8V A dip to 12.42V occurred when I opened the driver's door. A rise to 14.25V occurred when I started to drive. A dip to 12.48V came at my first stop. A return to 14.1xV happened when I resumed driving but dropped to the stretch of approximately 13V for a period of car sleeping time. The next short trip sent it up to the 14.xV range with a drop to 12.9V when I was back in the garage and shut it down.
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As soon as I attached the charging cable, it jumped up to 14.1+V and then slowly tapered down over the course of the long charging session. The dip to the right was caused by a brief power drop to the house (it happens a lot) and you can see the very end of the graph showing the voltage had dropped to what it was before the driving and charging, after the charging had completed.

Here's the same day's graph for the starter battery.
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Although similar ups and downs of voltage occur, they are not equal.

I have noticed that everything that causes a current draw of the 12V system may cause a period of "charging" to occur after the momentary drop. Unlocking a door, opening the rear hatch, opening the frunk, etc., may cause a brief jump up in the voltage to the 14.x range for both batteries and the starter battery will show deeper dips in voltage at the start and end of the "event". I haven't had the devices installed long enough to ensure my perceptions are correct all of the time. It will be interesting to see what these reveal. Maybe others have had such devices installed longer and can add insight from their observations.

Some of the monitoring apps (like the one for the INEX brand) allow you export (eg. email) the data (date-time and voltage) and that allows you to examine it on another device. Sadly the one for the Quicklinks monitor does not.
 

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I am using the same thing as well. Instead of using the free app, i have purchased the paid app BM3 which can monitor 4 batteries simultaneously and also export the data.

Your car charges the batteries at +14V while driving but my car only charges at +-13.7V while driving. This is one thing that i observed after the dealer replaced the wiring. Previously my car also charged at +14V.

Attached is the graph i have for a typical day:
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This is the BM3 app
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Ayepace, thanks for this well presented reminder of this modification for everyone on this forum.

By using the App with these relatively cheap Battery Monitors, EV owners could observe 12 battery problems well before they could cause dangerous break downs while driving.

I have been using 2 of these monitors over 12 months now. This thread below mentions my mods.


Cheers, Steve
 

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Timely. I was charging my nearly 3 year old/60,000 km car yday. I set the juicenet charger to only 90%. I think the car goes to initialization mode after the charge is stopped by the juicenet. I think this continues to drain the 12V battery in this mode as I got a warning from wattcat that my 12V is low at 12.1 a few hours after charging stopped. I took it to the dealer to get checked out as the car is going to sit for a couple weeks. They say both auxiliary and starter battery are fine. The dealer also said there's no specific interval to install new 12V batteries - wait till you get a problem - seems like a recipe for disaster.

They're still in the warranty period so would be replaced if they fail. Not sure I want to go 4 years on the same starter battery. My auxiliary battery has been replaced once. Unfortunately they have to charge me a diagnostic fee as the car didn't show any errors.
 

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2019 S with S21B and 16.2
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Adding to the data: my car charges at 14.1 volts and the batteries are at 13.0 volts right after charging. The auxiliary battery is at 12.9 volts and the starter battery is at 12.8 volts after sitting 14 hours. I compared the monitor reading with a Fluke and they were within 0.02 volts.
 

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Side question:

On many occasions, AyePace recommends to connect a charger to the +ve pole of the battery and the -ve to the chassis instead of the -ve pole of the battery. Is there a reason for that?
 

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19 I-pace HSE Polaris/Fuji white with most options and a lot of accessories
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Discussion Starter · #7 · (Edited)
Side answer:

The negative connection from the charger needs to be connected to the chassis because (1) it is safer in case of explosive gases near/from the battery (vent tube not connected or broken), (2) it is easier to make this connection for both 12V batteries, (3) a fully dead battery won't act as a total energy sink if you're just trying to get it started/powered up, and (4) the BSM on the negative post of the starter battery needs to observe the current flow through the battery and this won't happen if you connect directly to the starter negative post.

For #2, there's that chassis brace running along the back of the frunk compartment between the shock/suspension towers that makes a good ground point if your charger can attach to it. If you have the side covers pulls loose, you can see where the ground cables attach between the body and the battery. You can use those points too.

For #3, Here's an example of what I mean. I once had a completely dead battery in a Discovery. Attaching jumpers to the posts of the battery would not get it to turn the starter or even shift to neutral. Moving the negative connection to the engine (essentially opposite end of the ground cable) and it started up.

For #4, the BSM is under the plate seen to the left in the first battery picture posted above. You could clamp to there (not the battery post) but you can find other places with more area for the clamp. You won't chance frying the BSM with an electrical arc too.
 

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So, I checked the history after a couple days. It looks like when driving it charges at 14.0-14.2 volts. When it is plugged in to level 2 it charges at 13.6-13.7 volts.
 

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Side answer:

The negative connection from the charger needs to be connected to the chassis because (1) it is safer in case of explosive gases near/from the battery (vent tube not connected or broken), (2) it is easier to make this connection for both 12V batteries, (3) a fully dead battery won't act as a total energy sink if you're just trying to get it started/powered up, and (4) the BSM on the negative post of the starter battery needs to observe the current flow through the battery and this won't happen if you connect directly to the starter negative post.

For #2, there's that chassis brace running along the back of the frunk compartment between the shock/suspension towers that makes a good ground point if your charger can attach to it. If you have the side covers pulls loose, you can see where the ground cables attach between the body and the battery. You can use those points too.

For #3, Here's an example of what I mean. I once had a completely dead battery in a Discovery. Attaching jumpers to the posts of the battery would not get it to turn the starter or even shift to neutral. Moving the negative connection to the engine (essentially opposite end of the ground cable) and it started up.

For #4, the BSM is under the plate seen to the left in the first battery picture posted above. You could clamp to there (not the battery post) but you can find other places with more area for the clamp. You won't chance frying the BSM with an electrical arc too.
Thank you for all of your information and advice.
Since we bought our 2019 SE in June 2019 and don't know how long it sat on the lot before that, and
since we are planning to drive from South Carolina to Key Largo in November, and
since we don't want our cat to turn into a brick somewhere on the road in Florida,
we made an appointment at our dealer in Charleston in September to have both 12V batteries replaced.
If they test "bad" Jaguar will pay, I told them if they test "good" replace them anyway and we will pay.
For us, way too much aggravation to have surprises on the road.
 
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