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XC90 T8 Start Battery Failures...Views : 1142 Replies : 14Users Viewing This Thread : |
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Feb 3rd, 2024, 11:05 | #1 |
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XC90 T8 Start Battery Failures...
Hi,
I have a curious situation on going with start battery failures in my T8. In December during the cold snap I came to the car to find it dead. Opened the doors, jump started, start battery health looked suspect. Cold weather & 8 year old battery so I assumed it's time was up and purchased a replacement AGM battery. Two weeks later came out to the car and it was dead again. Charged the battery and all good. Car went in to the local dealer to have the sunroof fixed two weeks later and at the same time I asked them if they could check the battery/charging system due to what I had seen. They said check on battery fine, all ok. I went to collect the car, paid and they said they would bring the car round to the front. Service manager then appears, embarrassed, as car won't start. Test the battery again, condition poor so this was replaced. I was still concerned but needed to follow the process so took the car home and five days later having sat locked & charging when I went to use it - dead again. Now struggling to charge that new battery. My belief is that the start battery is charged from the hybrid battery. The only change that occurred about the time that this started was fitment of a new wall charger at home (which has charged the hybrid battery in the T8 and other cars). So, good people - my questions are Does the hybrid battery charge the start battery? Any experience of this hybrid-start battery process failing? Any ideas of what else could kill off the start battery? Any possibility that a wall charger (in this instance a Hypervolt Home 3 Pro) could interfere with the start battery (I think I'm clutching at straws with this one)? Thanks in advance...... |
Feb 3rd, 2024, 11:23 | #2 |
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I can’t answer your questions but I’ve posted about a few issues recently.
I’ve had the turtle/tortoise symbol appear claiming an issue with the hybrid drive train and the battery having insufficient charge. It had plenty of charge so that was nonsense and the irony is the car will only run on battery in this situation. Today, a week later I’m being shown 12v battery warning issues, and not remedied by trickle charging. So whilst I can’t answer your questions I’m wondering if the two are related and a hybrid battery issue is knocking on to a 12v issue or vice versa. Given the complexity of the system and the fact my car is 3 years old at the end of March I’m getting itchy feet. |
Feb 3rd, 2024, 11:52 | #3 | |
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Quote:
The car has a 12v battery and a 400v battery. The 12v battery simply runs the 12v systems in the car, such as the electronics, the windows, seats etc... It does not start the engine. The 400v battery is the traction battery and powers the car electric rear motor (ERAD) and also starts the car engine (ICE) through the starter/generator. The starter/generator is located top righthandside under the bonnet (facing from the front, looking at the windscreen). You can see the big Orange cables running to it (which denote the 400v system). The 12v battery is charged from the 400v battery via a transformer. I think (but not 100%) they share a common earth in the car body. So the 12v battery does not start the engine. It is not the "start battery". But it does require to have some charge otherwise the car systems will not power up. In the instances that this has happened, have you had charge in the 400v battery? A faulty wall charger could drain the 400v battery (this happened to a friend with a hybrid c class merc) and then after time the 12v battery could also go flat, but this is unlikely. Because the 12v battery is constantly looked after by the 400v battery then generally it causes no issues. I have not heard of any T8 owners having to replace the 12v battery. My assumption would be either your wall box is draining your 400v battery (and is therefore faulty) or you have a fault in the 400v to 12v transformer/rectifier circuit.
__________________
Currently:- - MY24 EX30 Ultra, Long Range, Single Motor, Black, Mist - MY16 XC90 T8 Momentum, Magic Blue 176k FOR SALE - MY17 V60 T4 Power Blue. Previously:- 1997 V70 T5 exPolice; 2005 V50 2.0D; 2013 XC70 D5 Last edited by Philip Fisher; Feb 3rd, 2024 at 11:54. |
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Feb 3rd, 2024, 13:04 | #4 |
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Thanks for this Philip.
I’ve experienced a low 12v battery recently. I mostly do short journeys on electric and keep the 400v battery charged up after use. Is your understanding that the 400v battery should prevent my 12v battery from ever being low? Thanks |
Feb 3rd, 2024, 17:04 | #5 |
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That is my understanding yes. The only way it can get charged is from the 400v battery. The car has no 12v alternator.
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Currently:- - MY24 EX30 Ultra, Long Range, Single Motor, Black, Mist - MY16 XC90 T8 Momentum, Magic Blue 176k FOR SALE - MY17 V60 T4 Power Blue. Previously:- 1997 V70 T5 exPolice; 2005 V50 2.0D; 2013 XC70 D5 |
Feb 3rd, 2024, 19:16 | #6 |
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Interesting. I had a botched software update recently, Volvo told me my 12v battery was low at the time and it transpires this seems to be the cause of this update issue.
Given they would have known my car was a T8, I wonder why, if your hypothesis is true, that Volvo didn’t think it was strange, or that there was some problem, if my 12v battery was as low as it seemingly was. Furthermore see a reply I made to a trickle charging thread I started. Trickle charging from the front didn’t charge the battery in the boot….. the plot thickens. |
Feb 3rd, 2024, 20:15 | #7 | ||
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Quote:
Quote:
In normal use the 400v system charges the 12v battery through a transformer. To manually charge the 12v battery you can charge through the terminals or connect to the battery. Both should charge the 12v system.
__________________
Currently:- - MY24 EX30 Ultra, Long Range, Single Motor, Black, Mist - MY16 XC90 T8 Momentum, Magic Blue 176k FOR SALE - MY17 V60 T4 Power Blue. Previously:- 1997 V70 T5 exPolice; 2005 V50 2.0D; 2013 XC70 D5 |
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Feb 4th, 2024, 21:22 | #8 | |
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Quote:
At all points the 400v battery has been partially or completely charged. There is no indication that the wall charger is discharging the hybrid battery at least with the trial I managed over the last 24 hours. I did try a clamp meter which clearly showed the charging but not discharging but it is a fairly coarse device. I will see if I can get more from Volvo on how the 400V transformer rectifier works and then the intermediate 400 - 12V device. I'd assume that to be some form of DC to DC converter. The converter between the 400V and the 12v battery does need to be investigated. In the case of the most recent failure after a brand new battery being fitted by the dealer, the car had only been operated for the duration of about an hour before sitting for four days and at that point becoming unusable. I've not been able to get any charge back in to the battery. We've only had 7 years and by comparison an embarrassing 50k miles. Thanks again for the information. |
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Mar 17th, 2024, 22:51 | #9 |
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So, by way of an update my T8 has spent a bit more than 4 weeks with the Volvo dealer. They have established that there is an intermittent excessive drain on the 12v battery. Much of the time the demand on the 12v battery will sit under an amp but quite frequently it will shoot up to 15 Amps. They have tried a range of methods to try to identify what is driving the increase to 15 Amps but without success yet.
The car has in effect been with them since the 5th Feb. I have borrowed the car from them on two weekends to drive long distances. In less than a day after significant use, the 12v battery will go flat. I carry an additional 12v battery and jump leads to get the electronics on and the car going again. Last weekend I drove 230 miles one day. When I came back to the car 16 hours later the 12V battery was flat again. The dealer is stuck and now talking about involving Volvo themselves. If they establish the cause I'll post the outcome. |
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Apr 27th, 2024, 18:38 | #10 |
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After 78 days .....
Having suggested the IHU, the internal wiring (the car had sunroof issues which the former Volvo Chigwell struggled to repair some years ago) in the end it was attributed to the central electronic module CEM (Part No 36003038) and replacing that does appear to have sorted the issue out. I've had the car back for five days. Must say that I had reached a point where I was looking for a replacement car. I was disappointed that focus/progress only developed after I wrote to more senior people in this dealership. Volvo themselves who I turned to after the first month (01628422522) were not worth the phone calls.
Just to re-iterate the symptoms - rapid 12v battery discharge as a consequence of unexplained drain which continuously varies between 1 and 15 amps. The 12v battery (new) was being discharged in little more than 12hours. 2016 XC90 T8 Momentum (with all the extras at the time apart from HUD). |
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