No auto stop-start on 2013 Focus - bad battery?

[watercooled]

So I've a 2013 Ford Focus with auto stop-start, and it doesn't stop-start...

Now in and of itself that doesn't actually bother me, and I'd rather it did have a way to permanently disable it rather than having to push a button every time you get in. But I still find it a bit concerning that it's not working.

Having looked online, apparently the stop-start system in these cars is very sensitive to things like outside temp, engine temp, cabin temp and climate control settings, and battery voltage. When I switch on the ignition, the A light goes orange>green>off so I assume it's self-testing OK, and after recently stalling (3rd instead of 1st), I pushed the clutch down and it instantly restarted itself so it does seem to be somewhat functional.

Now, I suspect the battery is on its way out, as after driving (or charging) it's only around 12.3-12.4v, and after sitting overnight it's more like 12.2v. Alternator seems OK as it goes 14+ with the engine running. That would add up as I've read the stop-start won't kick in if it pegs the battery at <75% charge or so.

I just took it for a free battery test and the meter came up 'Good, Recharge' which is strange as it was trickle charging all day yesterday!

Other measurements from the meter (the guy gave me the print-out):
12.18v standing voltage
577 CCA measured (vs 590 rated, so not bad)
11.89v cranking
10.2v lowest recorded

Now it still starts OK which I suspect is partly down to it being such a large battery for the engine anyway, but it's an expensive gamble for a replacement! Something like £120 for just the battery.

[peterb]

I suspect the battery is the caue of the problem - it seems to be intermittent and linked to the state of battery charge - as you state, it works correctly when the engine has only just stopped - after it has been running and therefore te battery will be at a transiently higher than normal voltage. (The nominal open cct voltage of a single lead acid cell is 2.1v - this will be slightly higher for a fully charged cell. As the cell ages, the internal resistance will increase, so the voltage drops off under load.

Four years is a typical age for a conventional lead acid battery to start failing. However Batteries fitted in cars with start/stop systems are often AG M types that generally have a longer life, although constant start stopping does take its toll. (An AGM battery in my car - not fitted with a stop/start system lasted 8 years)

You might find this interesting https://en.wikipedia.org/wiki/Lead–a...r_common_usage

[watercooled]

I'm not sure how that tester used works out the battery's CCA capacity, but if it's really managing 577A then that's not bad for a 590A rated battery. I'm thinking the stall-restart might not take any of those paramaters into account as it *needs* to restart then, it's not choosing to shut down at idle. The thing is it doesn't turn off whilst waiting at lights or whatever like you'd expect it to, even when the engine is warm, fan/AC turned off, etc.

The type fitted is an 'enhanced' flooded battery, not an AGM, but like I say it's a really big battery for the size of the engine. AFAIK the battery has been fitted since new, it's a generic Ford one, so it's quite possible it's just had it and needs replacing. It also seems to be sealed so I don't want to risk breaking something to have a look at electrolyte levels.

I've tried leaving it on a trickle charger but it still just doesn't seem to hold a full charge.

A replacement enhanced flooded battery from Yuasa is >£100, I suspect AGM would be a fair bit more!

[kalniel]

How long have you had it? In my experience Ford stop start is very sensitive, needs all sorts of things like a long journey recently, no particulate build up if dpf, even odd things like having enough fuel in the tank seemed to affect it. If you've not had it long, give it an Italian tune up, a long motorway blast and *then* on the next journey see what happens.

[Kumagoro]

If you do end up needing a battery http://www.batterymegastore.co.uk have good prices and next day delivery.

[watercooled]

I've only had it a few weeks and TBH it's mostly been around-town sort of driving. It's a petrol so no dpf but I get what you mean. I suspect it was sitting in the dealership for a month or two before I bought it too.

I'm planning a ~100 mile motorway trip next week so I'll see how it does after that. Again, the stop start not working doesn't actually bother me, I'm just wondering if it's indicative of something else that needs looking at. Some sort of status on the display would be useful! Plus, me being me, I can't just accept something behaving strangely if I don't understand why!

[Xlucine]

I've only had it a few weeks and TBH it's mostly been around-town sort of driving. It's a petrol so no dpf but I get what you mean. I suspect it was sitting in the dealership for a month or two before I bought it too.

I'm planning a ~100 mile motorway trip next week so I'll see how it does after that. Again, the stop start not working doesn't actually bother me, I'm just wondering if it's indicative of something else that needs looking at. Some sort of status on the display would be useful! Plus, me being me, I can't just accept something behaving strangely if I don't understand why!

Any chance of a warranty fix? Might be worth asking, it's recent enough to the purchase that you might be able to blag someone having a look at it for free.

[peterb]

A replacement enhanced flooded battery from Yuasa is >£100, I suspect AGM would be a fair bit more!

I got a 700 CCA Bosch AGM battery for around £140 from www.tayna.co.uk

[watercooled]

Any chance of a warranty fix? Might be worth asking, it's recent enough to the purchase that you might be able to blag someone having a look at it for free.

Based on their response when I asked about another minor and easily repairable issue, I'm guessing not!

I got a 700 CCA Bosch AGM battery for around £140 from www.tayna.co.uk

Yeah they do have some decent deals on AGM batteries though the recommendations they give aren't correct for my car (it recommends standard flooded batteries which explicitly say no start-stop). Any idea if it's OK to just drop in an AGM battery in place of a EFB? I know they have slightly different charge voltages.

[peterb]

Yeah they do have some decent deals on AGM batteries though the recommendations they give aren't correct for my car (it recommends standard flooded batteries which explicitly say no start-stop). Any idea if it's OK to just drop in an AGM battery in place of a EFB? I know they have slightly different charge voltages.

Thats a tricky one. My car shouldn't have had an AGM although it was fitted from new AFAIK. The model after with stop start has quite a complex monitoring circuit that changes the charge current as the battery ages, presumably to provide optimum charging at all times to cope with start/stop conditions. I think mine was probably undercharged - which might have contributed to its longevity.

The short answer is that you probably would be OK - but in the absence of an authoritative answer, I'd probably be inclined to replace like with like.

[GoNz0]

New batteries normally have to be coded in so it often isn't just the cost of a new battery, I would find out about that before you take the plunge. But normally it is due to it not holding enough charge, unfortunately you will have to have the ECU read to see what codes it throws to be sure, this will cost the least to start with.

[watercooled]

AFAICT there are two things I need to consider after a battery swap - the battery monitoring itself and the ECU. According to the manual, the radio is coded to the vehicle's VIN and doesn't need a code to be entered manually.

After disconnecting a battery for more than a few minutes, the ECU enters learning mode and you need to leave it idling for a few minutes followed by a few miles of driving. I think battery monitoring information is held in non-volatile memory so needs to be reset manually, which can apparently be done without OBD tools (have to press buttons in a certain order).

[watercooled]

Hmm, having read some of those posts, it might even be worth trying the BMS reset with the current battery - some people have said it fixed start-stop after it not working for a year or so. I'm not really hopefully given the battery doesn't seem to be holding a full charge, but suppose it's worth a go.

I know a few mechanics so I'll see if they're able to get anything from the ECU too.

[Tumble]

I'm driving a 15 plate Mondeo at the moment, and the start stop is borked from the factory. talking to a Ford tech about it, he said the issue is that the auto SS system won't function if the battery is at less than 85% state of charge, but that the alternator, in the interests of efficiency, doesn't actually start charging the battery until it's at around 75% This has the effect of keeping the battery somewhere around 80% most of the time, which means that the system is disabled most of the time. It's not like I do a lot of short journeys either - nearly 68k on the clock in 2 years. ...

[watercooled]

That sounds quite familiar! A lot of what I've heard about Fords (including on this thread) is the start-stop is very fiddly - I've been in a few Mondeos where it seemed to work fine, but where the owners did mostly long commutes.

Some articles seem to imply Fords will do some sort of regenerative braking to assist in battery charging; I wonder if this just means the alternator is loaded more heavily during braking, as I don't see any additional components in the parts list that could relate to this?

Edit: Having just said that, I'm not sure if I'm just imagining it but the car does seem to have significant engine braking to the point you can easily 'feel' when the clutch is pushed down - I wonder if that's why?

[kalniel]

I'd have thought you could feel engine braking in most cars to be honest, regardless of regen . Extent just depends on how large the flywheel is and what the software tells the fuelling to do to smooth it off.