Stop Start function and trickle charging

Faults and Technical chat for the Volvo XC40
Wedgie
Posts: 96
Joined: Sun Jul 15, 2018 3:09 pm

Post by Wedgie »

Had an interesting discovery today. I have been using a CTEK MXS 5.0 trickle changer on the car since new but the battery has never seemed fully charged and the stop start rarely functioned , perhaps not surprising given the lack of use due to Covid. I needed a second trickle charger for my motorbike and decided to use the MXS 5.0 on the bike and bought a new MXS 10 to use on the XC40. The battery is 70Ah in the XC40 and the MXS 5.0 is rated at 14-160Ah so should be fine. The MXS10 is rated at 20-300Ah . After 24 hours on the MXS 10 the car was showing fully charged and the stop start worked even after several short journeys and several starts.

Skyrimmer
Posts: 248
Joined: Fri Jun 07, 2019 3:14 pm
Location: Norfolk

Post by Skyrimmer »

I thought the stop/start worked off the support battery. How does charging the main battery get stop/ start working? I would be interested in getting one of these as my stop/start never seems to activate.
XC40 Bright Silver T3 Momentum pro with just about every option plus mud flaps and sunglasses holder.
Rollo
Posts: 5
Joined: Thu Apr 01, 2021 7:40 am

Post by Rollo »

Skyrimmer wrote: Wed Mar 31, 2021 10:23 pm I thought the stop/start worked off the support battery. How does charging the main battery get stop/ start working? I would be interested in getting one of these as my stop/start never seems to activate.
For cars having the Stop/Start system the car has two batteries, a larger Starter battery and a smaller Support battery.

The Starter battery starts the car and the Support provides support and runs ancillary operations which you may have operating while the larger battery does its starter job.

If you use too many electrical ancillary systems - radio, wipers, heated wheel, heater while using the stop/start system then the relatively small Support battery can't cope and the stop/start system is flagged as unavailable. Same thing if the Support battery isn't charged enough, small runs etc - then it won't have enough power to run the ancillary systems, and again the stop/start system will be flagged as unavailable.

In that scenario the larger starter motor takes over and runs both the starter motor and the ancillary systems. But not the power sapping stop/start system.
Wedgie
Posts: 96
Joined: Sun Jul 15, 2018 3:09 pm

Post by Wedgie »

Skyrimmer wrote: Wed Mar 31, 2021 10:23 pm I thought the stop/start worked off the support battery. How does charging the main battery get stop/ start working? I would be interested in getting one of these as my stop/start never seems to activate.
As Rollo as said, in simple the stop start motor is wired in line with the main battery and the electronics in the car protect the main battery by stopping stop start system when power is low or demand is high.
Chris John
Posts: 496
Joined: Mon Jul 20, 2020 9:08 pm

Post by Chris John »

It does make me chuckle that people spend £40k plus on a vehicle and then have to buy a charger to keep the systems running

My stop/start hasn’t worked for weeks, mainly due to lockdown and short journeys. Stay at home was relaxed on Monday, went for a drive and it’s working fine now 👍🏻
Volvo XC40 T5 R-Drive Pro. Thunder Grey with lots of extras
Deleted User 3359

Post by Deleted User 3359 »

Chris John wrote: Thu Apr 01, 2021 9:23 am It does make me chuckle that people spend £40k plus on a vehicle and then have to buy a charger to keep the systems running

My stop/start hasn’t worked for weeks, mainly due to lockdown and short journeys. Stay at home was relaxed on Monday, went for a drive and it’s working fine now 👍🏻
You're missing the point that an alternator on a charging system will rarely recover the battery to greater than 80% charge...
Rollo
Posts: 5
Joined: Thu Apr 01, 2021 7:40 am

Post by Rollo »

The manual says if you don't do a lot of mileage buy a charger or run the car for 15 minutes each week. I prefer to run my car for 15 minutes than waste money on a charger.

I have next to no interest in the capacity or charge rate or percentage charge in the battery or any other spec. Just want to get in and drive 🙂.
blastpipe
Posts: 565
Joined: Tue Aug 28, 2018 9:04 pm
Location: UK

Post by blastpipe »

Is there a difference between the T/D models and the newer B models with regards to batteries and stop start functionality?
T4 Auto AWD R Design March 2019
Chris John
Posts: 496
Joined: Mon Jul 20, 2020 9:08 pm

Post by Chris John »

Cornishman wrote: Thu Apr 01, 2021 9:32 am
Chris John wrote: Thu Apr 01, 2021 9:23 am It does make me chuckle that people spend £40k plus on a vehicle and then have to buy a charger to keep the systems running

My stop/start hasn’t worked for weeks, mainly due to lockdown and short journeys. Stay at home was relaxed on Monday, went for a drive and it’s working fine now 👍🏻
You're missing the point that an alternator on a charging system will rarely recover the battery to greater than 80% charge...
No you’re missing the point. I don’t expect to spend over £40k on a vehicle then have to buy a charger.....just like I didn’t have to on my Merc
Volvo XC40 T5 R-Drive Pro. Thunder Grey with lots of extras
Rollo
Posts: 5
Joined: Thu Apr 01, 2021 7:40 am

Post by Rollo »

There's nothing special about a Mercedes or a Volvo. They are just cars with engines and batteries. Both abide by the laws of physics.

If you don't use them the batteries will go flat.

If you don't use them very much to keep the batteries in trim you can either trickle charge or run the cars once a week.

It's in the Volvo manual, I dare say it's in the Mercedes manual as well. If it's not in the Mercedes manual they've made a mistake and left it out.

On a personal note my, bought new, RD T4 My20 AWD was a little under £32k. I'd feel aggrieved if I'd spent £40k for it, it's certainly not a £40k in feeling or quality.

Never had a problem with the stop/start system. Whenever it's stopped it's always worked again after a short run, as expected.
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