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Discussion Starter · #1 ·
I need to leave the car parked for about four months. From what I've read on the forums, I'm guessing that if I leave the traction battery at about 60%, it should still have a charge remaining when I get back.

The problem will more-likely be with the 12v battery. I’d like to leave it connected to an AGM battery trickle charger. (There’s a great suggestion made in this post on charging the 12v battery)

But in the Owner's Manual, they state that the 12v battery must be removed from the vehicle if it requires charging. And further, they say that the battery should only be removed/replaced by an authorized dealer. Not exactly convenient when you need a charge to get into the car, or want to maintain a trickle charge.

Does anyone know why they want the battery removed for charging?

My guess is that this is not an electrical issue… they’re probably worried about gasses collecting, since this battery’s is in a relatively confined space.

I’m thinking that with a good quality AGM charger, it’s unlikely that you’d generate gasses like you do with an overcharged lead-acid battery.

Any advice, or experience with charging in place?
 

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Gases are not a problem. The batteries have vent tubes attached to route any gases out of the confined area. The starter battery is a flooded battery not an AGM battery.

They do not want a charger attached that bypasses the BMS (battery monitoring sensor) attached to the negative post. That module monitors the state of charge and turns on the DC-DC converter as needed to recharge the 12V batteries. This will draw power from the traction battery.

The trickle charger extension that I posted about in the thread cited does not bypass the BMS. Its connections are the same as the body-to-negative post ground strap and the 12V connection from the DC-DC converter.

I tested using a low power intelligent charger with the extension. It worked as designed, stopped charging when it was "full", etc.

If the battery is replaced, the BMS needs to be reset to know the full state of charge for a new battery. It is documented that it will "reset" itself if not reset but the time for that adjustment isn't a set time. This leads to the recommendation to have a dealer replace the battery. It is also out of concern that the process is done properly without cables touching anything else. There's still a charge on the 12V positive cable from the other 12V battery and/or DC-DC converter. A dealer, replacing the battery per instructions, would use special JLR tools attached to the cables to insulate them during replacement.
 

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Discussion Starter · #3 ·
Thank you...great info. The manual says "An Absorbed Glass Matt (AGM) battery is fitted to this vehicle. AGM batteries are sealed for life and require no maintenance. To prevent damage to an AGM battery, do not attempt to open or remove the top from a battery." But the 12v starter battery is indeed a flooded battery.

Could they be referring to the Aux battery? Is that an AGM?

And if the Aux battery is an AGM, is there an open relay between the Aux battery and the starter battery, to prevent one from charging both the AGM and Flooded batteries at the same time (with the same charger setting)?

I checked a few other Jaguar Owner's Manuals, and they all say that only the dealer should remove/replace the battery. Probably for the same reasons mentioned above.

But only the I-Pace manual says you must remove the battery from the car before charging it. That still doesn't make sense...
 

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This has been covered in other threads.
The manual is incorrect with respect to the starter battery.
The small auxiliary is AGM.

There is a power supply distribution box that sends 12V power to the batteries. The wiring diagram does not reveal what is inside the box for achieving separation. It is more than a simple box of relays.
 

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This is my reasoning for the confused JLR battery charging instructions:

On my car the original larger "Start" battery had a float voltage just after charging of around 12.7 Volts, the small AGM "Aux" battery had a float voltage after charging of about 13.1 Volts. The "Start" battery has some "always on" loads, SIM data, security & unlocking etc.

When the "Start" battery eventually discharges to about 12.2 Volts, my DC-DC converter charger automatically connects both batteries together and starts charging them at 14.7 Volts, this charging voltage gradually falls as the batteries charge. This charging event can slightly deplete the Traction Battery. If my car is connected to the small A/C charger it will top up the traction battery if the % falls below 100%.

This charging system was originally engineered (and documented) with 2 x AGM batteries, the dissimilar batteries are what we got instead. Sometimes these differing loads, owners use of accessories and the battery characteristics result in one of the batteries going bad, ( either overcharged or sulfated ) this confuses the monitoring system and causes errors and alarms.

I replaced my "Start" battery with an AGM to match the charging system. Model Year 2021 cars have only one battery as a simple fix. I use Bluetooth battery monitors for my peace of mind.

See my signature below for my Mods.

Cheers, Steve

Edited per symos comment.
 

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Discussion Starter · #7 ·
When the "Start" battery eventually discharges to about 12.2 Volts, my DC-DC converter charger automatically connects both batteries together and starts charging them at 14.7 Volts, this charging voltage gradually falls as the batteries charge.
Lobster, does this charging take place on its own, without having to turn on the ignition? Is it necessary to have the traction battery charger connected?
 

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GoldRiver, a longer explanation to your question.

I installed my bluetooth Battery Monitors in Oct 2020, well before I replaced the "Start" battery.

The battery voltage events recorded from my car may be typical of only my car and its software update status at that time. :unsure:

The monitoring App daily 24 hour battery voltage graphs are still on my phone. Looking back in time I can observe many seemingly random events where the car momentarily wakes, and connects the two batteries to the normal connected loads, this produces a downward voltage spike on my graphs. I believe these to be inbuilt voltage sampling events.

Also of interest, my AC charger mentioned above, is connected to an Off Peak circuit controlled by my electricity provider, the circuit switches ON at 10:30PM and OFF at 06:30AM. When the AC supply turns ON I can see that the car always momentarily samples the 12V batteries. When the AC turns OFF it samples the batteries again.

If the car measures the battery voltage to be less than 12.2 volts a charging event is initiated, these charging events were for 75 minutes. My car would charge the 12 volt batteries from the traction battery if the charger was not connected. I was observing a loss of range due to these charging events, as the car was not in use at the time.

Cheers, Steve

P.S. My car always charges the 12V batteries when the ignition is turned on and also while it is is driving.
 

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Discussion Starter · #9 ·
Thanks, Steve.

So if I understand correctly... With a trickle-charger connected to the starting battery, the car would "wake" periodically, check the voltage, find it within range, and go back to sleep. It would not see the need to connect the two batteries together and begin charging.

If so, would the Aux battery's voltage eventually become low, even though the starting battery was kept at normal voltage? I'm guessing the system would trigger some kind of charging event if that happened. If that's true, you could have the trickle charger and the DC Converter Charger charging at the same time.

Maybe this is far-fetched. Ayepace has a well-functioning trickle setup...

What I'm trying to figure out is why JLR says that it's necessary to remove the Start battery from the vehicle before charging on the I-Pace (and only the I-Pace). Any idea why they say that?
 

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I don't advise the use of very low cost simple mode constant voltage trickle chargers. Smart chargers with modes for Gel, AGM, wet-cell, calcium batteries with multi stage charging characteristics are to be recommended as they will not boil your battery dry if left connected, as they should drop to a negligible current float voltage after charging.

I have been using a 2 / 6 / 12 / 25 Amp smart charger on my cars and caravan every month if they have not been used. All of these vehicle batteries have bluetooth battery monitors. It is very easy to measure 4 batteries at the same time, in less than 1 minute I can simultaneously download up to 30 days of data from each device. I used to use a digital volt meter for these tests.

The Start battery has a much lower resting voltage after charging than the AGM Aux battery, and it also has constant small parasitic load. My Aux battery has a very low self discharge rate, I have never observed it with a lower voltage than the Start battery.

The Start battery has a current measuring module on the -ve terminal this is used to regulate recharging from the DC/DC converter. The Aux battery does not seem to have this module, so I do not think the car knows this SOC, but I have noticed many reports of cars that shut down when the Aux battery drops below 12V.

I think JLR's battery recharging advice conflicts with their abuse of these dissimilar characteristic 12V batteries in the I-Pace charging system. On my car these two batteries are always charged at the same time and same voltage. :mad:

Cheers, Steve
 
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Per the workshop manual information, both batteries are monitored. The starter battery has the Battery Management System module to directly monitor its SOC and turn on the DC-DC converter to supply charging. The auxiliary battery appears to be a more indirect method of a microcontroller in the Power Supply Distribution Box and communication with the BCM/GWM.

The PSDB connects/disconnects loads to the starter battery or the auxiliary battery, and charging the auxiliary battery, using MOSFETs as commanded by the BCM/GWM. The two batteries are isolated from each other. The PSDB can direct charging to either or both as commanded by the BCM/GWM.

The auxiliary battery is important because it supplies 12V to the brake booster module, front electric power inverter converter and parking lock actuator in the front electric drive unit. This battery ensures there is power to be able to safely bring the battery to a stop after a failure of the startup battery system (or it gets drained too far).

This is a very condensed version of information. There's a lot more in the 17 page document.

This leads to the realization that the 12V batteries could fail for
  • defective battery
  • defect in wiring
  • defect in PSDB
  • defect in DC-DC converter
  • defect in BCM/GWM
  • defect in BMS
  • software updates required for any/all of those control modules
 

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Aypace, thanks for posting those interesting extracts. Unfortunately I must be the only owner on here logging the 12 volt batteries. It would be great if a few of us could monitor their batteries, as your dot point comments suggest any defects in these modules could contribute to battery failures. My monitored records may not be typical.

re: "The PSDB connects/disconnects loads to the starter battery or the auxiliary battery, and charging the auxiliary battery, using MOSFETs as commanded by the BCM/GWM. The two batteries are isolated from each other. The PSDB can direct charging to either or both as commanded by the BCM/GWM. "

My two 12 V batteries are only ever isolated from each other when the "Ignition" is OFF, the exception to this is when the DC/DC Converter starts a charging event (when the car is locked ). When charging occurs both of my batteries always receive exactly the same voltage.

Cheers, Steve
 

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I agree with your observations. Just because it "can" doesn't necessarily mean it always utilizes that function. For all we know, the programming might make an assumption that if the starter battery needs charging then the auxiliary battery may need topping up too.

There's also a statement that both batteries get charged while the traction battery is being charged.

There's also a description of difference in behavior for power modes (e.g. car fully powered up and being driven vs. shut off). I didn't go into that.
 

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Discussion Starter · #14 ·
Have a look at this interesting post, from the UK forum:
I was separated from my I-Pace for 11 months during the peak of Covid. I left it with about 65% charge on the main battery and plugged into nothing. I returned to find it ready to go with nearly the same charge on the main battery as it had when I left. I didn't give a thought to the 12v battery but I guess it was fine because I got in and drove away. Maybe I was lucky. (from wilhawk)

It sounds like he benefitted from the scenario that Lobster describes above. That is, where the car wakes up, samples the voltage, and initiates a charging event if required. I'm puzzled...
 

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Yes that is the way it is supposed to work. However, that requires all software components are updated to current status and 12V batteries that are not defective.

Normally dealers are told to hook up external power supplies to ICE vehicles sitting in show rooms. Provided the dealer isn't one that turns on any electrical draining features of the car (e.g. parking lights) for extended times, Jaguar published showroom instructions to dealers that they should not attach the external supplies to the I-pace. Instead, the car will keep the 12V batteries charged on its own. They only need to connect a level 2 charger to charge the traction battery (and 12V batteries) if it sits for a very long time.
 

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Discussion Starter · #16 ·
Thanks, Ayepace. And I'm wondering... for charging (while away) to work as designed, does it matter whether or not the car is locked and alarmed? It seems I read that somewhere, but I can't find where it was.
 

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In my experience, if the car is not locked and armed then my "smart" charger only works for a short times and then registers a full battery even though the voltage meter shows on the low side. That's with my car having the latest software installed.
 
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