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An auto stop/start battery charging question

 IHN
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Our Honda Jazz does the auto stop/start thing when idling in neutral (so, sitting at lights etc). Lately it's not been doing it, and I suspect it's because it's being used for a lot of short journeys so the battery isn't getting a proper charge.

I figured it would do no harm to stick on a battery charger overnight. I have a charger, I presume I can just connect it and let it do it's thing, there's nothing I need to bear in mind cos of the stop/start shenanigans?


 
Posted : 07/04/2026 1:28 pm
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Should be fine to do that - if it's an AGM battery, select that on the charger. 

Given weather, temperature etc, my van hasn't been doing stop/start much. Did after it finally got a good run a couple of weeks ago.


 
Posted : 07/04/2026 1:41 pm
jamj1974 reacted
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How old is the car/battery.

That is sometimes a sign the battery is not performing as it should. Basically can't hold enough power. Happened to me on an old car and a new one with a faulty battery. New battery fixed it both times.


 
Posted : 07/04/2026 1:42 pm
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On my Ducato the Stop/Start kicks in if the main battery has been disconnected. I always opt to disable the function. Despite several long runs recently it's not kicked in for months which I'm happy about.

 

Have been told by several mechanics that it's better if the engine keeps running and there's less wear on the starter motor. Don't feel guilty as I'm very, very rarely driving through towns in stop-start traffic.

 

It's more a gimmick for manufacturers to lower their emissions.


 
Posted : 07/04/2026 1:51 pm
 IHN
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Posted by: fossy

if it's an AGM battery, select that on the charger. 

...er, and how would I know/check if it was or not?


 
Posted : 07/04/2026 1:57 pm
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It's written on the battery ! It will say AGM.   How new is the charger ?


 
Posted : 07/04/2026 2:01 pm
 IHN
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That's good then 🙂 Charger is a Noco one, bought in Covid (when the old car didn't move for months...)


 
Posted : 07/04/2026 2:09 pm
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Good chargers Noco. I have a CTEK charger and NOCO jump starter. A lot of stop start batteries are AGM. 


 
Posted : 07/04/2026 2:13 pm
IHN reacted
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Have been told by several mechanics that it's better if the engine keeps running and there's less wear on the starter motor. Don't feel guilty as I'm very, very rarely driving through towns in stop-start traffic.

 

 

 

It's more a gimmick for manufacturers to lower their emissio

ns.

Perpetuation of myths without any factual knowledge isn't really a great thing 

Yes, it is to lower emissions. This is a good thing 

No, it's really unlikely that multiple teams of engineers from multiple manufacturers with vast supply chains haven't considered the wear and tear implications on a starter motor. Confirmation bias and anecdotes are strong on this one. It's not in their interest to have multiple warranty claims for premature failures.

There's all sorts of stuff going on with stop/start that adds up to an awful lot more than just killing the ignition. From stopping at certain points in the cycle, to changing timing etc, and that's veggie you look at the negative effect on engines from things like sitting idling for extended periods, as they would do without stop start.


 
Posted : 07/04/2026 2:36 pm
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Good chargers Noco.

Big brand but actually perform poorly against both their peers and their rated outputs and ability to recover deep cycled batteries. 

Found that out after i bought mine and wondered why it wasnt doing what my previous ring charger did with ease - disapointed. Their boost pack is still great. 

 


 
Posted : 07/04/2026 3:13 pm
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Both of our vehicles don't auto stop start any longer. It's because the batteries are old, although still entirely adequate for starting duties. I'm not spending £££ to replace them just to get that function back, and I'm quite happy assume that the energy required to produce a new lead acid battery and recycle an old one outweighs the energy saved by a few minutes of saved idling every journey. 

I agree about the non-issue of increased engine and ancillaries wear though. 


 
Posted : 07/04/2026 3:30 pm
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Posted by: submarined

No, it's really unlikely that multiple teams of engineers from multiple manufacturers with vast supply chains haven't considered the wear and tear implications

Posted by: submarined

It's not in their interest to have multiple warranty claims for premature failures.

Would these be the same geniuses (genii?) who came up with 7mm timing chains and wet belts...they obviously know what they're doing!

 


 
Posted : 07/04/2026 8:27 pm
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Having air con running can prevent stop/start too I think.


 
Posted : 07/04/2026 8:43 pm
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Normal wet battery charger will damage an AGM battery.

Make sure the charger has the AGM option.

Get the battery health checked. Usually free or buy a cheap tester.


 
Posted : 07/04/2026 9:24 pm
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Some manufacturers (Toyota definitely) limit the total number of starts the auto start will do to protect against wear. Once the car has done x starts the auto function will never work again regardless of battery age.


 
Posted : 07/04/2026 9:31 pm
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Posted by: dafydd17

Posted by: submarined

No, it's really unlikely that multiple teams of engineers from multiple manufacturers with vast supply chains haven't considered the wear and tear implications

Posted by: submarined

It's not in their interest to have multiple warranty claims for premature failures.

Would these be the same geniuses (genii?) who came up with 7mm timing chains and wet belts...they obviously know what they're doing!

 

Yeah, possibly the same ones who came up with the rotary engine as well. Nobody's perfect. 

Still trust them more than a mechanic's anecdotal evidence 

Less facetiously, it's an industry wide thing, not one manufacturer doing 1 daft thing.

Some manufacturers (Toyota definitely) limit the total number of starts the auto start will do to protect against wear. Once the car has done x starts the auto function will never work again regardless of battery age.

I was under the impression that was for the starter, and could be reset when the starter was replaced. Iirc it's also something like 350k(citation needed) cycles, which averages out at around 50 years for your average use case (eg not a taxi, so probably about 2 years for most Priuseseses)


 
Posted : 07/04/2026 10:07 pm
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Posted by: submarined

 

I was under the impression that was for the starter, and could be reset when the starter was replaced. Iirc it's also something like 350k(citation needed) cycles, which averages out at around 50 years for your average use case (eg not a taxi, so probably about 2 years for most Priuseseses)

Yes, that's what I meant. Not so much a response to the OP, but to the discussion. However, it's possible to artificially adjust the number of starts so that it no longer functions. I wouldn't because I quite like the feature and also that it gives an indication of battery condition. Plus in all the cars I've ever owned I've never had to replace a starter motor so i'm not particularly worried about one failing.

 


 
Posted : 07/04/2026 10:44 pm
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Less facetiously, it's an industry wide thing, not one manufacturer doing 1 daft thing.

You're still talking about wet belts and weak chains are you? 🙃

 


 
Posted : 07/04/2026 10:58 pm
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Posted by: submarined

Posted by: dafydd17

Posted by: submarined

No, it's really unlikely that multiple teams of engineers from multiple manufacturers with vast supply chains haven't considered the wear and tear implications

Posted by: submarined

It's not in their interest to have multiple warranty claims for premature failures.

Would these be the same geniuses (genii?) who came up with 7mm timing chains and wet belts...they obviously know what they're doing!

 

Yeah, possibly the same ones who came up with the rotary engine as well. Nobody's perfect. 

Still trust them more than a mechanic's anecdotal evidence 

Less facetiously, it's an industry wide thing, not one manufacturer doing 1 daft thing.

Some manufacturers (Toyota definitely) limit the total number of starts the auto start will do to protect against wear. Once the car has done x starts the auto function will never work again regardless of battery age.

I was under the impression that was for the starter, and could be reset when the starter was replaced. Iirc it's also something like 350k(citation needed) cycles, which averages out at around 50 years for your average use case (eg not a taxi, so probably about 2 years for most Priuseseses)

That one manufacturer being the Ford, Citroen, Peugeot, VW, Vauxhall, Honda, Toyota, Renault, Audi, Seat, Skoda group?

 


 
Posted : 08/04/2026 12:59 am
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If you replace the battery, even like for like, it needs coding in/some kind of electronic magic from a diagnostic device (at least it did for our Focus) so the car knows there's a new battery and then reactivates the system.  

As for switching the system off permanently I just don't get it.  

Rest deleted so back OT.  

OP a longer drive might also sort it.  It might be it takes an hour or so though.  


 
Posted : 08/04/2026 7:24 am
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That one manufacturer being the Ford, Citroen, Peugeot, VW, Vauxhall, Honda, Toyota, Renault, Audi, Seat, Skoda group?

Honestly, I'm not quite sure what we're talking about now, and if all have the same issue, with the one single thing, but my stance remains that generally, I have to balance factors and so trust qualified engineers' judgment and experience. Accepting that there will always be influence from budget and perhaps other factors in design. 

Stop start has been around for a long time now, and as far as I'm aware, we're not facing a scandalous epidemic of starter motor failures and premature engine wear.


 
Posted : 08/04/2026 7:28 am
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AIUI, stop/start is to (mainly) fiddle the numbers a la VW dieselgate. I may be well out of touch but the received wisdom was always, an engine experiences the most wear during start up, though that may be cold start up. I turn my stop/start off as I can't see the benefit during my use case. I use my car infrequently for long journeys only - motorways for multiple hours. Stop/start isn't really a thing unless there's a queue.

As for trusting the designers/engineers. As has been said; wet belt, Euro 5/6 compliance, disposable engines, cars essentially designed to last the life of the warranty, diesel gate, difficult/impossible servicing? Those designers/engineers? I'm sure they know their stuff I just don't think their actions/decisions are always to our (the consumers) benefit. A lot of decisions are made (one way or another) to make profit (or reduce cost - same/same) for the manufacturer which doesn't always benefit us during ownership.

 


 
Posted : 08/04/2026 8:00 am
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Posted by: boblo

Stop/start is to (mainly) fiddle the numbers a la VW dieselgate.

Really! That's a load of rubbish. Emission tests are based on the engine running which it's not while stopped. Would make sold all difference to emission measurements (unlike the fiddle in diesel gate). Stop/start does however improve the air and noise around junctions with frequent queues. It would also make sod all difference to economy tests.

Having Aircon on does not always prevent stopping. If the Aircon is set to max cold then it might prevent stopping but on other settings the latent cold is used (with the engine restarting after a period if the temp goes up to much).


 
Posted : 08/04/2026 8:12 am
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My van is the first car I've had with stop start. If I commute in it (usually bad weather as I cycle to work) it can have the engine turned off for over 5 minutes whilst idle in traffic - that's not insignificant in an hour (say 10%). I recently did a three hour trip, and because there was hardly any stopping, I think it switched off for less than a minute. I do know the ECU is busy balancing how many electrical devices may be on, a/c is always on, the heated seats may be on, ambient air temperature, and engine temperature, the list goes on. It won't use the stop start when it's been sat for a week not moving.


 
Posted : 08/04/2026 9:06 am
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Posted by: alpin

Have been told by several mechanics that it's better if the engine keeps running and there's less wear on the starter motor.

Shame the mechanics didn't tell the people who design, build, and warranty the car this. Or it could just be that stop/start has negligible impact on engine wear and reliability?


 
Posted : 08/04/2026 9:23 am
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Posted by: submarined

That one manufacturer being the Ford, Citroen, Peugeot, VW, Vauxhall, Honda, Toyota, Renault, Audi, Seat, Skoda group?

Honestly, I'm not quite sure what we're talking about now, and if all have the same issue, with the one single thing, but my stance remains that generally, I have to balance factors and so trust qualified engineers' judgment and experience. Accepting that there will always be influence from budget and perhaps other factors in design. 

Stop start has been around for a long time now, and as far as I'm aware, we're not facing a scandalous epidemic of starter motor failures and premature engine wear.

Some of the manufacturers that use a wet belt in their engine line up.

As for stop/start we've only one vehicle with it fitted. It worked for about two weeks when I fitted a new battery, hasn't worked since, I won't be spending money to find out why.

 


 
Posted : 08/04/2026 9:33 am
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Posted by: submarined

Perpetuation of myths without any factual knowledge isn't really a great thing 

Yes, it is to lower emissions. This is a good thing 

No, it's really unlikely that multiple teams of engineers from multiple manufacturers with vast supply chains haven't considered the wear and tear implications on a starter motor. Confirmation bias and anecdotes are strong on this one. It's not in their interest to have multiple warranty claims for premature failures.

This.

I've been driving for 35 years.  The last time I had to replace a starter motor was in a 1977 Ford Fiesta.

Posted by: boblo

I may be well out of touch but the received wisdom was always, an engine experiences the most wear during start up, though that may be cold start up.

Step away from the 1977 Ford Fiesta.


 
Posted : 08/04/2026 9:53 am
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Stop-start will obviously reduce fuel consumption/emissions. My understanding is that the emissions 'scandal' or whatever with VW was that they programmed the engine management to reduce fuel use at a narrow power/speed (whatever) band - at which the testing was done. 


 
Posted : 08/04/2026 10:04 am
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There's exactly what it was boxelder.


 
Posted : 08/04/2026 1:09 pm
 mert
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They also had a way to detect when the bonnet was open. Having flat spots and emissions tweaks at certain engine load/speed scenarios wasn't the issue. Switching them on and off when the car was in a test/emissions rig was. (They've since clamped down on the weird engine behaviours too. That's now not acceptable.)

Stop/start saves about 5-7% on a typical emissions test cycle, converts to about 3% in the real world, for typical drivers.

Posted by: boblo
I may be well out of touch but the received wisdom was always, an engine experiences the most wear during start up, though that may be cold start up. I turn my stop/start off as I can't see the benefit during my use case. I use my car infrequently for long journeys only - motorways for multiple hours. Stop/start isn't really a thing unless there's a queue.
Maximum wear is at *cold* start. Warm start it's negligible, the starters and ring gears for S/S cars are typically sized for 300-500000 starts. An old starter system would typically be sized for around 75000 starts. With a proper ISG the extra wear is immeasurably small.

If you're doing lots of long motorway driving, why even bother switching it off, it won't activate.

Posted by: alpin

Have been told by several mechanics that it's better if the engine keeps running and there's less wear on the starter motor. Don't feel guilty as I'm very, very rarely driving through towns in stop-start traffic.

You've been told by several people who really haven't got the faintest idea what they are talking about.

 


 
Posted : 08/04/2026 1:45 pm
 rsl1
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I find it wild to be on a cycling forum reading about people turning their start stop off. It makes such a difference if you're filtering in traffic and everyone's engine is off. Basically unfathomable to me how it can bother a driver so much that they feel the need to go out of their way to turn it off. 


 
Posted : 08/04/2026 3:58 pm
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People fear change.

Stop/start can be an issue if it stops right at the second you want it to start, but that just requires a slight rethink in how you drive.  Blipping the accelerator will wake it up ahead of you setting off and you probably shouldn't be driving requiring split-second timing as a matter of course anyway.

But as above, and as on the previous driving thread, things have changed since the days of my mk1 Fiesta.  Warm-starting that thing in traffic was like getting your grandad's lawnmower going.  It was stolen one time, I was astounded that some random scrote had actually managed to get it moving.


 
Posted : 08/04/2026 5:43 pm
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I’ve switch my stop/start off in my MG HS trophy (auto) when I get into it as it is very slow to restart from off, the dealership knows about the glitch but MG hasn’t provided a software update…..and they still haven’t provided updates for the utter shite gear change/it often drops gears for no reason and bounces off the rev limiter and that was immediately noticeable when I first drove it 2 years ago.

 


 
Posted : 08/04/2026 5:55 pm
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Been out RIDING my BIKE so not able to rejoin the squabble until now 🙃

When I said 'a la dieselgate' up there^, I meant 'a bit like' not 'exactly the same as' in fiddling the numbers to improve the headlines. Helpfully, up there someone says ~3% improvement in emissions and presumably a bit in fuel consumption? A few years ago, I turned off the air-conditioning over winter to 'save' fuel. All good until I turned it back on and it leaked due to dry seals or some such. Cost a couple of £k to sort - dashboard out etc. An example of well intentioned actions costing more in the real world. I know the systems are supposed to be designed for multiples more of stop/starts but they would say that wouldn't they...? Mine's staying off unless my use pattern changes.

 

 

 


 
Posted : 08/04/2026 6:02 pm