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Jump starters
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Rover_Driver wrote: »Modern alternators have a the output to power all the vehicle electrical load and still have sufficient left to fully charge the battery.
Modern alternators?
The last car that I had that had a flat battery was built in late 2011.
The reason for the flat battery was a failed alternator.
Battery was so flat you couldn't even put it in neutral to get it on the low loader. (61plate XJL)
With new alternator in place Jaguar decided not to trickle charge the battery.
Net result was the car suffered with constant battery low warnings when sitting in the car with the radio on.
It got better when I charged it properly, funnily enough.
Though was never the same and I replaced it within a year.
So which cars have a more modern alternator than a £60k Jaguar?0 -
Graphs available on the internet typically show charging currents of 40 amps at idling speed. That's 500 watts. Easily put to the test though: switch on everything with engine at idle and then Rev. up ....do the lights brighten up? Do they dim down when you slow down to idle again?0
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Modern alternators?
The last car that I had that had a flat battery was built in late 2011.
Modern alternators - even in 2011 - have a maximum output around 100 amps, more than enough to supply the vehicle with the power it needs and keep the battery fully charged.
A problem battery was more likely to cause the problem with your Jaguar.0 -
Rover_Driver wrote: »Modern alternators - even in 2011 - have a maximum output around 100 amps, more than enough to supply the vehicle with the power it needs and keep the battery fully charged.
A problem battery was more likely to cause the problem with your Jaguar.
Did you actually read my post?
The alternator failed on the A4 and completely discharged the battery.
The discharged battery was not charged by Jaguar, probably because the Tech involved was of the same opinion as you, in this case the wrong one.
The day before the Alternator charge I could sit in the car for 30/40mins listening to the radio before the low battery warning would pop up (the XF and XJ both have this warning)
The same car a few days after getting it back would not allow me to sit listening to the radio for longer than 5/6 minutes before setting of the low battery warning.
It improved back to near previous levels after a proper overnight charge.
The battery lasted nearly a year, which was a lot of miles, and gave up the ghost when the weather got really cold.
Funnily enough the XJ and XF are known to be hard on batteries due to the amount of ECUs in the vehicles.
Why not prove some information to prove me wrong?
Here is a link that might prove helpful.
https://www.optimabatteries.com/en-us/experience/power-source/fact-alternators-are-not-designed-to-charge-dead-batteries/0 -
Graphs available on the internet typically show charging currents of 40 amps at idling speed. That's 500 watts. Easily put to the test though: switch on everything with engine at idle and then Rev. up ....do the lights brighten up? Do they dim down when you slow down to idle again?
Practical demonstration in an LDV V8 fitted with battery charge indicators on the dash for all three batteries. Green, Amber and Red.
No1 Starting Battery.
No2 Accesories
No3 Sirens and Lights.
Fitted with two alternators.
Sit in said vehicle for anything over 15/20 minutes with lights on, MDT and SatNav on and reading lights on. Quicker if you have the AC running.
First the No3 battery charge light goes Amber then No2. Shortly after No3 and No 2 will go red and and lastly No1 will flicker between Amber and Red.
Give vehicle a rev and all lights go to green. No1 first, then 2 and lastly 3. No 3 reaching a good charge level was awkward if the vehicle had not been left connected to the trickle charger overnight as you could easily hit the Sirens just after leaving station and all they would do was squawk quietly.
Standard workshop policy for all possible battery/charging issues was to charge the rack of batteries overnight before a new battery is even considered. There were under bonnet batteries and a slide out rack in the side cupboard.
That is a practical example that I have witnessed hundreds of times. Vehicle a properly maintained NHS vehicle. Hence the twin alternators, fitted using the biggest alternator bracket you are ever likely to see.
On tickover even two alternators struggled to cope with the draw from the vehicle systems.
If you sat without the AC or any lights in there was no problem.0 -
Graphs available on the internet typically show charging currents of 40 amps at idling speed. That's 500 watts. Easily put to the test though: switch on everything with engine at idle and then Rev. up ....do the lights brighten up? Do they dim down when you slow down to idle again?
And your point?
What graphs exactly?0 -
I had to Google LDV 80 to ascertain that it's a Chinese van which they export to Australia and Ireland ...didn't feel so bad about my ignorance once L'd learned that. Seems to me that someone didn't uprate the charging system to cope with the added electrical demands.
I think, though, that we're arguing at cross purposes. I agree that if a lead acid battery gets REALLY flat then it's difficult to recharge. Smart chargers (and I assume that all modern cars systems come under this heading) are protected against producing too much current by recognising the low voltage of a really flat battery and delivering only a small voltage which takes hours to get the battery to a state where it can safely be given a normal charging regime. Because it takes many hours this more economically done with a mains powered charger rather than driving around for 12 hours or more. I still believe that a modern standard production car can recharge it's battery from flat given enough time.
Regarding output at idling speed, I've never seen any variation in headlamp output, nor heard any variation in heater fan speed, from my present two modern cars apart from a flicker from the Jazz when the aircon compressor cuts in so I'm confident that they both charge the batteries at idling speed. The original selling point of the alternator when it was introduced in the 1970's was that its stronger armature permitted gearing up to a speed which gave battery charging even at idling speed unlike the dynamo which it replaced0 -
Did you actually read my post?
The alternator failed on the A4 and completely discharged the battery.
The discharged battery was not charged by Jaguar, probably because the Tech involved was of the same opinion as you, in this case the wrong one.
The day before the Alternator charge I could sit in the car for 30/40mins listening to the radio before the low battery warning would pop up (the XF and XJ both have this warning)
The same car a few days after getting it back would not allow me to sit listening to the radio for longer than 5/6 minutes before setting of the low battery warning.
It improved back to near previous levels after a proper overnight charge.
The battery lasted nearly a year, which was a lot of miles, and gave up the ghost when the weather got really cold.
Funnily enough the XJ and XF are known to be hard on batteries due to the amount of ECUs in the vehicles.
Why not prove some information to prove me wrong?
Here is a link that might prove helpful.
https://www.optimabatteries.com/en-us/experience/power-source/fact-alternators-are-not-designed-to-charge-dead-batteries/
I think you have caused some confusion here and whist you think it's clear in your head what you are now saying is an alternator is not designed to charge dead a battery. When previously you stated.Personally I would buy a proper smart charger for the X Trail.
As far as Jump Starters go as they are usually marked up as suitable for a range of engine sizes.
If you buy CarMechanics Mag there are often adverts for decent car tools and stuff like chargers and jump starters.
Remember that getting a flat battery started with a jump is only part of the problem
The alternator was never designed to fully charge a battery.
So if your battery has gone flat then it will never fully charge without the use of a decent charger.
Which is why I mentioned a smart charger first.
Any trip you take in your X Trail will be pre planned.
This giving you plenty of time to charge the battery up properly beforehand.
Which kind of suggests once battery voltage is lost the alternator is not designed to fully recharge it. Which is of course in correct.
You suggest people provide evidence to back up their arguements and the one time you do it contradicts you. Irironic really.0 -
Fortyfoot - while I appreciate you are asking about a jump-starter, that will certainly fix your problem - but only in the very short term, by getting the engine running, rather than doing anything about the underlying problem.
Taking more out of a battery than you are putting back in after starting is quite easy - especially in winter, with cold starts, lights and heaters etc.
Couple that perhaps with short journeys and the battery has no chance of being replenished,
I'd give serious thought to getting a 'Smart-Charger' as others have suggested, and keep your batteries fully topped up.
Prevention is better than cure.
A Smart Charger is also considerably cheaper than a booster starter-pack.
Lidl & Aldi regularly have them on special offer - mine cost £13.990
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