2018 T8 completely "dead"

hhl1687 · Jun 10, 2020

I believe people have discussed similar issue here but I could not locate those posts after going some lengths searching this forum ...

Due to the COVID-19 situation, we are not using our T8 for about 2 months. Right from the last use, I kept the car hooked up to the 110V charger, thinking a relatively "modern" car won't have any issues with dead 12V battery due to long period of inactivity. The drive battery should be protected by more sophisticated mechanism ...

But today, almost 2 months later, I found the car completely dead. It seemed there's no 12V power at all. Doors remain unlocked since they were unlocked after last use. Otherwise, no sign of life for any of the electronics or control ... none responds ... I popped the hood, saw a compartment with a plastic cover, with electronic connectors underneath, and some signs suggesting it may be some kind of auxiliary battery: "+" and "-" signs, but also a strike-through image of another car connected to this one using jump cable - so I guess we cannot do that for this car?

Has anyone had similar experience? What's your solution? Is a flatbed to dealer the only way out?

RootDKJ · Jun 10, 2020

You can jump start it from another 12v power source using the contact points under the hood. The regular 120v charger does not send any current to the 12v system. Volvo’s recommendation is to run the car once a week. Also, locking the doors tells the cars computer to go into sleep mode. Volvo also recommends that you leave the hybrid battery at 25% if not using the car for a while. Once 12v is restored the drive battery will be fine.

stick_shift · Jun 10, 2020

'Modern' cars are even worse than 'traditional' cars when it comes to parasitic loads. I've been living in the same covid environment as everyone else but still manage to get out several times a week, cars are all fine.

Don't expect a lead-acid battery to last more than 5 years even under the best of conditions. It's a wear item. Allowing it to drain down completely will shorten that life. Charge it up and hope for the best.

Gary-16-Xc90 · Jun 10, 2020

2018 T8 completely "dead"

Bummer.

Just to re-iterate and clarify a few key points:

1. Locking the car is essential if the car is not being driven regularly.

2. Jumping the car using the 12v jump posts is the best option - assuming that your hybrid battery was fully charged before the unexpected 2-month no drive period.

I am unclear what the 120v charger is. Is charger to keep the 12v batteries charged or is that the hybrid battery charging cable (Dual Turbo cord in US)?

I will assume that it is the latter. If the car will not be used for a period of time, it is best to leave at 25-50% charge where as stated ~25% is recommended as stated in the earlier post.

Why? The hybrid charging system in fact charges the 12v battery IF there is sufficient capacity to charge the HYBRID battery.

Once the Hybrid battery is at 100% charged (and maybe even between 90-99%), the Hybrid Charging no longer accepts and shuts off the charging to the Hybrid battery and to 12v batteries. A short hybrid charge may not be sufficient to fully charge your 12v batteries.

Suggestions
1. Unplug your 120v AC Hybrid charger from the car and the wall. The Turbo Dual has a built in breaker if my memory is correct.

2. Check your wall breakers on the electrical panel and any GCFi receptacle - just to make doubly sure that they are not tripped.

3. Try one last time to charge you hybrid battery if jumping did not work.

4. Try to jump start your car using the jumping posts using another vehicle or an appropriately rated jump start battery.

5. Check engine compartment fuses for hybrid charging system if you are an experienced DIY'r. Be careful. Excerpt below for MY16 so check your own manual, or better ask your service center.

5. Call the service center for advice, or call for a flatbed tow. Rarely, the onboard hybrid charging system fails or a fuse goes bad.

Best of luck and you will fine thereafter.

MY16 XC90 T8

All the best from Minnesota USA,
A fine MY16 XC90 T8

RootDKJ · Jun 10, 2020

Hey Gary

I don’t believe the TurboCord charges the 12v battery at all regardless if it’s at 110v or 220v

Root

Gary-16-Xc90 · Jun 10, 2020

RootDKJ said:
Hey Gary

I don't believe the TurboCord charges the 12v battery at all regardless if it's at 110v or 220v

Root

Root,

Here is the basis in my MY16 manual for my conclusion. It is not conspicuous and may be subject to interpretation:

All the best from Minnesota USA,
A fine MY16 XC90 T8

Gary-16-Xc90 · Jun 11, 2020

2018 T8 completely "dead"

Here is another post that confirms that the 12v start battery is charged by the hybrid charging system. It also suggests that the the start battery may need to be recharged if it sits for an extended period.

Of course, the hybrid battery is what actually "starts" the ICE on the T8. If the hybrid battery has no charge, ICE will not start. The IGM is what starts ICE on a T8. The Start battery is an auxiliary 12v power for locks, lights, Sensus, et al.

Start battery is an unfortunate holdover from T5 and T6 which both use the start battery to start ICE - not so with T8.

All the best from Minnesota USA,
A fine MY16 XC90 T8

VolvoUhu · Jun 12, 2020

RootDKJ said:
Hey Gary

I don't believe the TurboCord charges the 12v battery at all regardless if it's at 110v or 220v

Root

It does maintain it while the 400v is charging. To avoid discharge the car should be locked to keep most of the XC90's systems in sleep mode rather than standby.

snovvman · Jan 12, 2024

Like the OP, for a 2018 T8 that is completely dead that requires the 12V replacement, what is the battery size? The best I can find is a Group H7 located on the rear cargo driver side. Is this correct? While I am here, how does one open the hatch without power? Is there a keyhole? I am not near the car at the moment to look.

The car was not driven for over two months and remained unlocked. My two battery chargers, one 25 amp, one 4.5 amp trickle, did not work to bring the battery back to life. Previously I read that the HV battery charger did charge the 12V, but I guess the information was wrong.

2018 T8 completely "dead"

hhl1687

RootDKJ

stick_shift

Gary-16-Xc90

RootDKJ

Gary-16-Xc90

Gary-16-Xc90

VolvoUhu

snovvman

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