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Oz34
United Kingdom
2501 Posts |
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Simon
United Kingdom
447 Posts |
 Posted - 20/02/2019 : 15:06:11
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Timely warning but perhaps not too much of a problem for MMM ers? (my battery is 13 years old and still good) I'm not sure I understand the problem though ( Aston Martin/BMW link-up) surely if connecting a good battery to a flat battery for starting, the current draw will be from the flat battery direct to the starter switch via the jump leads and good battery. Those leads will only carry the current required by the starter motor, surely then the alternator output on the donor car is irrelevant? I have found that if jump leads are not hefty enough the starter won't get enough current to turn anyway.
Simon C. |
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Cooperman
United Kingdom
758 Posts |
Posted - 20/02/2019 : 15:23:28
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I have a VOV (very old Volvo) and just before the last MOT was due the SBS warning light came on. My local independent Volvo man couldn't find the problem but reckoned it was something to do with the passenger seat air bag. Replacement cost about £900 plus labour.
We were having our carpets cleaned and I expressed my concern to the chap doing them, he replied "my brother-in-law does those, I'm sure he could sort you out." Oh yes I thought. He gave me his number and with nothing to loose, I called him and arranged to take the car over to him. After several minutes checking this and that with a plug in computer and various meters. He asked if I had had to jump start the car anytime recently. I told him I had when I was in Waitroses car park waiting for Mrs C and I was listening to a tape not the radio (which would have used less juice), I had to call the RAC as I didn't have a spanner to access the battery in the boot. "did you drive straight off when it was started?" he asked. I told him I had and had driven home. That's the answer. Apparently when you have a flat battery and jump start the engine the battery has insufficient charge to operate all the electrical items and as a consequence it can burn out the ECU or at least one of them. You need to wait about 15 minutes to charge up the battery.
He fixed it by locating a second hand one and the charge was about £300 which included the MOT and VAT.
You electrical/electronic engineers out there does this make sense to you? Or was I fobbed off?
John Cooper M 628 |
Edited by - Cooperman on 20/02/2019 15:25:34 |
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Cymber
United Kingdom
966 Posts |
Posted - 20/02/2019 : 21:34:37
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I had an interesting event on my Fiat recently. Its electronics had been playing up for a while and had gone into limp mode. I had to put the battery on charge so disconnected the battery and charged it. Afterwards all the electronic problems had gone, the electronics had reset themselves, as other electronic things do, and the engine was back on full power. A local mechanic had never heard of that happening on car electronics.
Maurice. |
Edited by - Cymber on 20/02/2019 21:37:36 |
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Matthew Magilton
Australia
179 Posts |
Posted - 21/02/2019 : 06:43:01
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Disconnecting the battery bought your engine back to full power? I would absolutely love it if that simple solution worked for my MG's too LOL.
Matthew. |
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Blithe Spirit
United Kingdom
185 Posts |
Posted - 21/02/2019 : 08:14:38
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I have a F**d Transit motorhome. A few years back I left it standing unattended for too long one winter and needed to jump start it, which I did with no problem, other than the ignition warning light remained on. Having checked that the alternator was still charging I took the van to a trusted auto electrician for advise. Upon being told I jumped started it he responded that you must never jump start a vehicle with a "smart alternator" as it can burn out the "smart" link in the ECU. He offered two solutions. A new ECU at around £700 or he could bypass a relay for £5. I chose the latter, and everything has worked fine since, except the alternator is no longer "smart",but I have noted no operational difference. So, yes, beware jump starting a car with an ECU. Not a triple m issue though!
Regards, David |
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Cooperman
United Kingdom
758 Posts |
Posted - 21/02/2019 : 09:37:33
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That confirms my feeling that anything "SMART" simply isn't in fact the complete opposite. Smart Motorways, smart meters, smart 'phones etc.
John Cooper M 628 |
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Ray White
United Kingdom
42 Posts |
Posted - 23/02/2019 : 00:13:15
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I have read through these posts on jump starting a 'modern' with interest. I have a battery charger with a 75 amp jump start facility (which I have not actually ever used) and it has just occurred to me that apart from the potential for reducing the life of a battery, using it could also inadvertently result in a failed ECU if I should drive off when the battery is not fully charged. In the past I have always thought it advisable to give the car a run to ensure the battery is fully charged. It would seem that now we need to keep the battery on the charger to slowly charge it up fully before use.
You learn something new every day.
Incidentally, I wonder how many people omit to disconnect their batteries when putting them on charge? If you don't and you leave a battery charger connected for a long time, it can fry the alternator's diode, apparently. Alternators have a fan to keep things cool; with the alternator stationary things can get pretty hot.
R. White |
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leckstein
USA
411 Posts |
Posted - 23/02/2019 : 11:28:21
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I recently purchased on Amazon a small "Suaoki" lithium battery kit. It weighs about 3 pounds and sits in a 8x5 inch case. I have not used it yet but the reviews are good .It comes with short (less than a foot) battery cables and claims to be able to start a car with a dead battery three times on one charge. It also has connections and leads to charge an Iphone, has a bright LED flashlight (Torch) and even a compass. They cost about $75 US dollars. I intend to pack it on trips in my MMM cars.
Mike L |
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BobH
United Kingdom
243 Posts |
Posted - 23/02/2019 : 12:01:19
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The charging circuitry on modern cars is a real swamp of complexity. Many cars now have an alternator which only charges the battery during braking or on the over-run, in the name of fuel efficiency, so waiting 15 minutes with one of those probably won’t work - sounds like it's that function which David’s electrician has bypassed.
Leaving the a battery connected whist charging would not to do damage to the alternator diodes on an old-fashioned system because the diodes will be reverse-biassed so not passing any current. On a modern - who knows?
A pal of mine has ten-year-old Clio which wouldn’t start. The battery seemed OK as it happily churned the engine over quite fast and repeatedly with no problem, but changing the battery cured it. Seems the electrics are now very fussy about the actual voltage they get so I can quite believe that running on a low battery could cause damage to the ECU; that might have been why the thing wouldn’t start as some sort of safety feature. Giving it enough volts to start but then dropping the volts by removing the booster might not be a good idea.
All part of built-in obsolescence I guess…… |
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gordclark
Canada
170 Posts |
Posted - 05/03/2019 : 07:07:20
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Living in the Canada, there are always opportunities to jump-start a car, and most drivers here carry a set of heavy, copper-wire jumper cables in the boot.
If possible, its always best to coordinate the connection with a second party. But let me tell you a little trick I use when I'm alone, jumping a battery. I carry a pair of heavy work gloves, so that if there's no place to put a hot lead when connecting or disconnecting, put it in the glove. Then go to the corresponding connection and pull (or set) the clamp.
Mike Leckstein's idea is great, except that the unit must be kept charged. Also, loses effeciency when left for days in the boot at -25°C (like tonight here!).
Gord Clark
Rockburn, Qué. |
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leckstein
USA
411 Posts |
Posted - 05/03/2019 : 11:17:25
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Gord: the charge is supposed to last 6 months. My thought is to keep it charged every three months and check it before going on an MG trip. I rarely drive my MG in minus 25C weather, actually I have never driven anything in - 25C degree weather!!
Mike L |
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