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:

This is the BM3 app

 

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 Volt 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.

Hi Shadowfax from West Australia new owner 2018 model

What is the best connector to purchase to access TESLA destination chargers? Can I replace the 12 volt battery with a lithium ion type.

www.i-paceforum.com

Cheers, Steve

edit: typos

 

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.

 

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.

 

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?

 

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.

 

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.

 

Spent 2 weeks in Hawaii with my Ipace sitting in the garage at 54% charge. Came back and it was still at 54% charge. No problems with the 12V batteries - watt cat showing 13v on the 'aux battery' and 90% on the TCU. Missed driving it after 2 weeks of various rental cars - Chrysler Pacifica , Ford fusion hybrid, Nissan Ultima - all felt like tin cans.

Didn't see a single Ipace in Hawaii . A lot of Teslas though and 1 Audi E-tron.

 

I travel for work a lot and have rented a lot of cars. They all smell the same (the same cleaning fluid must get used everywhere)...

 

My batteries and monitors are doing well. I check them every 2-4 weeks. I had the first non 100% recently (96%). Has anyone that uses these had an imminent or actual 12v go bad? If so what were the signs?

 

Correct float battery voltage depends on temperature. If memory serves it is a negative coefficient so charge voltage should be lower at higher temps. At 20’C (could be 25, can‘t remember exactly) it is 13.8V. So any well designed charger should show an output voltage that varies with battery temperature (often assumed to be the same as ambient) and might account for someone in Hawaii seeing a different voltage to someone in Norway, for example. Constant current float is another method. Obviously a charger may also include other charge modes but I would expect, most of the time, we would just see float mode with the ipace, or a digital/modulated variation of that (e.g. the 5% hysterisis mentioned above). I don’t know how the ipace dcdc charge method is actually designed.

 

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.

What would one look for in the graphs in order to predict a failure? Would you expect to see frequent discharges and recharges while the car was idle?

Would those who already have a monitor be confident of spotting a failure (rather than preemptively replacing batteries, possibly at your own expense)?

And @Ayepace, I believe you've had both 12v batteries replaced. Did you have this monitor installed before that replacement? If so, did you get any hints that the batteries were failing?

 

Only the auxiliary battery has been replaced as of this typing. Yes, I've had the monitors on the car batteries since this thread was started.

The aux battery died in February while the car was being driven, 10 miles after leaving home where the monitor said it was 100% charged. The car managed to recharge it sufficiently over 45 minutes while I ate at a restaurant and I was able to drive back home without incident. It was time to replace it because every startup after that got the "OK to drive with caution" message. The monitor showed periods of nothing (not enough power/voltage to run the monitor) followed by charging-by-the-car periods that brought the monitor back to life.

I could have used my alternate battery (that's a different thread), but since it is under warranty, I had the car towed in to the nearest dealer for its replacement. The Jaguar prescribed process was strictly followed. Both batteries were removed and tested. The aux battery was replaced and the startup battery was returned to the car fully charged. The dealer tech even reconnected the monitors.

I am expecting the startup battery to fail eventually. Probably in the near future. My eyeball monitor has noticed that the voltage at 100% charge of the 12V battery shows a trend of a gradual decrease. This was also true of the aux battery before replacement. After replacement, the aux battery is showing a steady voltage of 13.08 (+/- up to .02). These are not scientifically accurate monitors so I only look for a trend. The startup battery showed 13.0 after the car charging stopped in the wee hours of this morning and shows a gradual decline over the day down to 12.9. This isn't much but it is not as steady as the newer aux battery. Before driving it yesterday, the voltage was down to 12.79.

 

The monitor showed periods of nothing (not enough power/voltage to run the monitor) followed by charging-by-the-car periods that brought the monitor back to life.

Do you think a battery load tester would be a better predictor of failure? Their charging and cranking test modes wouldn't be useful on an EV, but the battery health mode might be. You can get a pretty good one for under $40.

 

That would be a bit of an effort to disconnect the batteries and load test them on some schedule (monthly?). Unlike an ICE where the battery won't get a charge without the engine running and driving an alternator, the batteries have to be disconnected (known as a 12V system shutdown) or they'll trigger charging with the DC-DC converter drawing power from the traction battery.

 

Is there any concern with parasitic draw by these monitors? (I mean, probably not, but maybe someone here has experience in that regard)

 

Having used these devices on vehicles for over 1 year, I can say there is no concern. They draw so little energy that it isn't really detectable. The cars draw more energy to keep their alarm systems and body control modules active in their low power states.

 

Having used these devices on vehicles for over 1 year, I can say there is no concern. They draw so little energy that it isn't really detectable. The cars draw more energy to keep their alarm systems and body control modules active in their low power states

I checked the usage of these units with an ammeter. Mine are rated at 1.5 mA, but they actually use 0.9 mA. So the power consumption (at 12.6v) is 0.0113 watts, or just over one hundredth of a watt. (I tested it on an FJ Cruiser, whose normally current usage at rest is 10.1 mA.) To put that into perspective, an old-fashioned dome line will use 1 to 2 watts.

I also measured the rate of battery decay to resting voltage, both with and without the monitors hooked up. There was no discernable difference in the time it took to decay 1/10 volt.

 

As the starter battery is a flooded lead acid and the aux is an AGM they will behave differently. Also the Aux is smaller capacity.

 

The 12V reading shown by MyPace and WattCat comes from the JLR API. I've compared it to at rest readings (not charging or car on times) and found it closer to the startup battery than the 2018-2020 aux battery. It's number is inaccurate during driving/charging periods. It is too high.

It is true that my aux battery went from good to fail in an instant. However, prior to that the monitoring showed a downward trend in battery voltage when at rest. I pressed my luck. My startup battery is showing this now. The car is past 5 years since it was built. If the startup battery makes it past warranty end, I will replace it as preventive maintenance.

When my cat came back from the vet at 42k service it didn't shutdown the 12V system. I was able to use the battery monitor graph to show the tech that it actually started doing that while at their shop and continued for 3 days (weekend interval) since the voltage was at a constant charging voltage. He appreciated seeing that as it was proof without having to do his own testing.

I have recently changed to BM200 monitors. The app is more informative. It shows battery SOC, voltage, and temperature individually and together. In fact it gave me an alert that the startup battery is at 78% power as I was typing this. The graph shows the downward trend as the cat has been napping for 5 days.

I do recommend the monitors as long as the owner uses them to watch for trends rather than considering them as scientifically accurate monitors, and is aware that batteries can fail at any time.

As an aside I had one on my whole house generator startup battery. It always showed a good constant voltage. Unfortunately, I wasn't aware that indicated the system was keeping a charging level on it all the time. The battery reached end-of-life with no way for me to know in advance. One day the generator just didn't start on its scheduled test cycle. This proves that one has to look at the rest periods, not the charging periods.

Finally, it may be worth the cost of a new battery to have peace of mind. You could take it out and have it tested and replace it based on testing results.

 

Finally, it may be worth the cost of a new battery to have peace of mind.

[I'll second that. I replaced both 12V batteries prophylactically at just over 3 years and 25,000 miles. Aaaah, peace of mind. But I also installed access to a pair of wired 12V monitors, should I need it.]

 

Thank you all for your input. I went out today and opened the frunk to try and figure out when my starter battery was installed, but unfortunately it seems no one circled the month / year on the label, so impossible to tell. I was only able to tell that it’s JLR branded, so possibly original from 2020 or possibly sometime after. I’ll probably go ahead and replace it preemptively. Thank you all for your help and sharing knowledge

 

I saw a writeup today that says the car Companys making electric cars are using the wrong batteries for 12v systems. They are using starter batteries, instead of deep cycle batteries (trolling motor batteries). That would get rid of the 12v battery failures the industry is having. There are no 12v loads in electric cars that require a starter battery. Wow!