Knackered alternator - how far can I go / driving advice

[trashbat]

So on Thursday, for the first time, my battery light started staying on when starting the car, until revved past about 2k RPM, where it went out.

That same evening it quickly escalated into every single system like ABS, EBD, stability etc producing warnings, as they do with low power, leading to me pulling over and restarting (idiot), except obviously it didn't because it was flat as a pancake. I got some help and a battery charge from the RAC which was enough to get me home. We reckon it's the alternator.

For most of today the battery's been on charge using a Ring smart charger, and seems to be well into the realms of diminishing returns from that now.

Tomorrow morning I ideally need to get 40 miles of motorway & A-road to the specialist. Obviously I can turn off all the obvious stuff to help with this, but I'm wondering if it'll be enough.

So, petrol car (2 ltr), 60Ah battery that's 3.5 years old and apparently in reasonable health. What are my chances, and beyond the obvious, what I can do to improve them? Worth pulling fuses? Any optimal driving style? Talk numbers at me

[nyt]

I once drove back from Germany without a working alternator.

If there's no rain and you don't run with headlights then you should be alright imho

[t400ble]

40 miles? probably too far

[s p a c e m a n]

Take it that it's manual as an auto wouldn't have lasted 5 minutes. Depends what the alternators actually putting out, but I fancy your chances and would do it myself.

[TooMany2cvs]

trashbat said:

Tomorrow morning I ideally need to get 40 miles of motorway & A-road to the specialist. Obviously I can turn off all the obvious stuff to help with this, but I'm wondering if it'll be enough.

So, petrol car (2 ltr), 60Ah battery that's 3.5 years old and apparently in reasonable health. What are my chances, and beyond the obvious, what I can do to improve them? Worth pulling fuses? Any optimal driving style? Talk numbers at me

Drive as smoothly as possible, to minimise brake light use.

You might make it, but the battery won't have much left in it when you get there. You might not. If you were going to pull fuses, it'd be stuff that's ignition-on, such as the electronic nannies. But if they're not doing anything, their current draw will be minimal anyway.

Perhaps more importantly, have you seen the forecast for tomorrow? Definite lights-and-wipers day...

[mybrainhurts]

I've done 40 - 50 miles with no alternator belt in daylight with good weather, mostly motorway.

Also 30 miles in the dark and cold, no motorways.

Both diesels.

[Slidingpillar]

Tomorrow from the forecast is not a day to go anywhere in a car with no battery charging.

If the wipers and lights weren't needed, a decent battery ought be all right over that distance. Give in full charge overnight, and if you live on a hill, bump start it too.

[trashbat]

fking weather!

I've Rain-X'd the st out of it though

Good tip on the bump start but no such luck I think. Depends if I can push it far enough.

Technically I only need to get 10 miles away from home for the RAC to tow me to where I like, but I really don't want that argument, or to break down on the shoulderless A31, or be towed at all for that matter.

On the other hand, I can hope that the alternator is just not working well rather than completely fked. For all I know it's been bringing the battery down gradually for a while.

Edited by trashbat on Friday 6th June 20:13

[TooMany2cvs]

trashbat said:

Good tip on the bump start but no such luck I think. Depends if I can push it far enough.

RainX doesn't help other people see you, and lights take more power than wipers do.

trashbat said:

Technically I only need to get 10 miles away from home for the RAC to tow me to where I like

Perhaps don't be so tightfisted with your RAC cover, then...?

trashbat said:

On the other hand, I can hope that the alternator is just not working well rather than completely fked. For all I know it's been bringing the battery down gradually for a while.

EVERYBODY who mucks about with cars really does need a multimeter. They're dirt cheap - ten to fifteen quid'll get you all you really need. Or a couple of quid on a Chinese fleaBay ciggy-lighter-plugin voltmeter.

[trashbat]

I have decent RAC cover (Recovery and At Home, as opposed to just Roadside). The 10 mile bit is what the bloke said yesterday, although he may be wrong as it looks like I'm covered for onward travel once I get only a short distance from home. No experience of it as I've never used their services before until yesterday.

I also have a multimeter but couldn't determine much about whether it was delivering charge, as the figures changed significantly.

Edited by trashbat on Friday 6th June 21:07

[Impasse]

I managed to get a 1998 GT3 Esprit from Donington to SE Hampshire with the battery light aglow. Gentle cruising (drive it hypermiling standards) and zero excess electrical items used. So no wipers, side/head lights, indicators, electric windows, radio, interior fan, or sitting with your foot on the brake in traffic.

And most of all, do not stall it.

[Gixer]

I drove a Supra from cliff to Hastings and back with no alternator years ago, and it rained most the time. Supra had a massive battery though.

More recently I had one fail on the way to Lakeside I still went there and back. Kept everything off that I didn't need. Probably about 35miles no problem. Battery still had good charge when I put a VM on it when I got back.

If you can take a spare battery with you, then if yours dies, swap em over

[trashbat]

Impasse said:

Gentle cruising (drive it hypermiling standards)

See, there's a question. How much of the battery usage is going to be time-based, and how much is based along the lines of fuel efficiency?

E.g. is it better to drive at 40mph for an hour, or 80mph for 30 mins?

[TooMany2cvs]

trashbat said:

ee, there's a question. How much of the battery usage is going to be time-based, and how much is based along the lines of fuel efficiency?

E.g. is it better to drive at 40mph for an hour, or 80mph for 30 mins?

A small amount is going to be rev-based (fuel injection, sparks), but most is going to be time-based (engine management, dash, ABS etc).

[trashbat]

Cheers, that's kind of what I figured. The load from lights etc is easy to work out but the average load of other systems, less so.

Seems like the answer is fast as safely possible, and then hoping that the alternator isn't completely dead, keep the revs up.

Well we'll see tomorrow

[basherX]

Perhaps someone could explain something to me about alternators (I'm a bit of a mechanical idiot)...

We had the one on our Mondeo fail at Easter. No battery light which it would have expected and the chap from the AA said this wasn't uncommon. But what really puzzled me was that during the two weeks before failure there was about a 8% fall in fuel consumption which has then reverted after the replacement was fitted. How does the alternator affect fuel consumption? Is it related to physical resistance? Or just coincidental...?

[Andyjc86]

What car is it? An alternator is bread and butter on most cars, can you not find somewhere closer?

[Andyjc86]

What car is it? An alternator is bread and butter on most cars, can you not find somewhere closer?

[trashbat]

Andyjc86 said:

What car is it? An alternator is bread and butter on most cars, can you not find somewhere closer?

Yes and no.

It's an Alfa 156. The alternator on this is squirreled away and seems to requires dropping the subframe or removing the head, depending whether you go at it from top or bottom. This makes it maybe a four hour job.

What's that got to do with it? Well I was due to have the engine rebuilt (prior to some further work) in just a few weeks at the specialist, so it saves a significant sum combining the jobs.

[Raize]

The vast majority of current draw will be from the fuel pump rather than the spark plugs. In most cars the fuel pump delivers fuel at a constant rate which is then returned to the tank if not injected. Thus I believe that your range will be measured in minutes rather than miles.