2-3 years ago my wife's T11 micra refused to start due to no battery power. So I put the charger on it. The switched on to hear a funny sort of squeely clicking noise and immeadiately switched it off.
It turned out the battery (an original) had gone open circuit, or at least, was in a state where it was unable to take much charging current.
All battery chargers produce a voltage higher than the 12 - 14.5 volts or so of a battery and, in the run of the mill chargers, the charge current is limited by either a series resistor (a bit old hat nowadays) or a series inductor (nowadays designed into the transformer as leakge inductance).
So an open circuit battery will have perhaps 20 or may be even 24 volts put across it and this can get to the electrics with possible unfortunate consequences.
I was lucky not to have damaged the electrics of the car. But 2 years later when I sold it, it was still all OK.
I tell you this in case it should happen to anyone else. In my case I will never put a charger on a battery again, that is still connected to the car, without doing a few checks.
May be Honest John's recommended smart charger is smart enough to take this into account -- anyone know. A design, for instance, could have a voltage limiter than stopped the charger voltage going above 15 volts even if the leads were not connected to a battery.
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Correction to a post above - as engine oil gets colder its viscosity is LOWER not HIGHER..............and vice-versa
/picky mode
;-)
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Am I missing something ? Of the 22 liquids listed by Kaye and Laby (Table of Physical and Chemical Constants)none have a higher viscosity as the temperature rises. OK, they do not actually list motorcar oil but . . .
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I am no chemist but my understanding of motor oil viscosities, as quoted on the packaging, is that they are designed to get thicker when hot. Multigrade 10W/50 is viscosity 10 when cold and when 50 when hot; it is written down somewhere what the 2 temperatures are but certainly it does get thicker when hot SFAIK!
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Motor oil thins out when hot........ever drained hot oil?
In other words, it gets LESS viscous
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That's right DL..Armitage, the 50 figure doesn't mean that the oil gets more viscous as the engine heats up - which would be contrary to our natural assumptions - what it does mean is the oil is engineered to thin less quickly than it would otherwise, and so at full working temperature it has only thinned down the same amount as a thick monograde oil would have which was rated SAE 50 at room temp.
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Or rather, I agree with your second post DL but not your first.
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1. "as engine oil gets colder its viscosity is LOWER not HIGHER..............and vice-versa"
2. "Motor oil thins out when hot........ever drained hot oil? In other words, it gets LESS viscous"
In (1) Engine oil cold = lower/less viscous
In (2) Engine oil hot = lower/less viscous
Which is correct? I think we should be told.
V
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As I understand it, 10W/50 has the viscosity of a 50 reference oil at the (specified) higher temperature but the reference oil is still less viscous than the 10 is at the lower temperature. In other words the 10W/50 oil will get less less viscous as the temp. rises but by a lesser amount because of the additives that enable it to be called 10W/50. I am sure an oil expert can come in arbitrate on this one, perhaps Sean.
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I am no chemist but my understanding of motor oil viscosities, as quoted on the packaging, is that they are designed to get thicker when hot.
All engine oils get thinner when heated.
Multigrades get less thinner than mono grades when heated.
The winter grades of 5W, 10W and 20W are determined by the oils' viscosity at
0° Fahrenheit (-18°C), while grades 20,30, 40 and 50 are determined by its viscosity at
212° Fahrenheit (100°C). Those are the predetermined temperatures.
This means that a 10w/40 oil will have the same viscosity as a mono grade 40 at 100c, but the viscosity of 10w at -18c
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Isn't it funny how this message started out as 'Maintenance Free Batteries'!
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Doc
Yes - spot on!
Regards
John S
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"awful things, these maintenance-free batteries. They still suffer evaporative loss of water but it is difficult to check the level or top them up."
"My daughter's cinquecento had one of these batteries and when it finally failed I would estimate there were only a couple of inches of electrolyte left."
Too true, Dr. Chris. The space left in the battery by the evaporation of the electrolyte then fills up with the hydrogen and oxygen produced during charging. This is an explosive mixture.
I once made a spark near a similarly depleted battery in a Talbot Sunbeam (I plead stupidity on both counts, m'lud). After the resulting explosion, I would estimate there were only a couple of inches of the chunky plastic battery casing left. The remainder had been transformed into plastic shrapnel which, with the battery acid, had showered the surrounding area. Fortunately, I was inside the car turning the engine over & there was no-one else in the vicinity.
I'd strongly recommend that you top the battery up, even at the risk of it failing.
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As a very non-technical person, I would merely add that if your battery is dodgy in October you can bet your life that it will let you down on that cold, wet morning in January when you have an important meeting and you woke up late. For the price of a new battery how about just getting a new one and have peace of mind for the winter?!
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Exploding batteries scare the life out of me
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Maybe the battery will let me down, but I am too cheap to throw it away if it can be kept going for a while. I have got some de-ionised water and will top it upop this weekend. I will let you all know what happens (unless it explodes and kills me of course...)
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Further thoughts. The electrolyte is probably mostly lost through electrolysis, rather than evaporation (pedant mode off).
These things are a booby-trap for the unwary. Someone gets a duff battery, like Joe's, they try to jump start it, make a spark and bang. You may thing I've exaggerated, but I don't think so. The bang was about as loud as a grenade (more like an L2 than a 36) and I was left with the electrodes dangling by their cables in a shallow tray of steaming acid. It was almost funny.
So read & memorize the bit in the Haynes manual about jump starting. The final connection to earth will make a spark and is made a looooooooooong way away from the battery.
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Well blow me. I was able to see the fluid level quite clearly, and there is a pointer showing what the level should be. All of the cells were pretty mush full, none of them was below 1cm of the level indicated. I topped them all up. We will see if that does the trick, but I would be surprised.
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It will do the trick until a few cold mornings hit. Mark my words - you will need a new one! They ain't that expensive! Or at least get it tested properly
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Regarding topping up batteries I have always prised off the labels etc and done this.
However when the battery on my Vectra was flat a few months ago could find no way of getting into it.
All was revealed when I went into Halfords last week and they had a pile of Lindsay Porters colour manuals for Cavalier Vectra Calibra amongst others reduced from £19.99 to £4.99.
Bought one and in the battery section I note that....
\"A so called maintenance free battery may have flush fitting strips over its cells which can be prised up for the addition of electrolyte perhaps prolonging its life.
This does not apply to batteries supplied as original equipment on new Vauxhalls. They Cannot be opened up....\"
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There's "maintenance-free" and maintenance-free.
When I'm about to change my Vauxhalls, usually at about 6 years old, I remove the really maintenance-free GM battery from the car and use it in my caravan, instead of an expensive leisure battery. The old caravan battery, about 12 years old, is then put in the car ready to be traded-in. This works very well as I've never had a failure from a GM Vauxhall maintenance-free battery.
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Likewise, the OE and replacement Delco batteries on my Vauxhall Royale Coupe were, I feel sure, maintenance-free and the car was on only its second one in 16 years when I sold it.
Some maintenance-free batteries have a labyrinth system to prevent them exploding, e.g. when a spark is caused nearby. A friend had a top-up type battery explode in his face when disconnecting it from a charger -- luckily he didn't suffer any permanent injury but it was not nice!
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My wife's Peugeot 106 "maintenance free" battery from Halfords has lasted 6 years.. mind you it was replaced under warranty after 35months:-)
madf
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My wife's Peugeot 106 "maintenance free" battery from Halfords has lasted 6 years.. mind you it was replaced under warranty after 35months:-)
So it has actually lasted just 3 years...
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Doc, That was mads little joke......
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A bit like the man who had a yard broom that lasted 20 years.
"It's only had 3 new handles and 4 new heads!"
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Just a *gentle* reminder that this is Technical Matters. Discussion is on the other side of the fence. Should you wish to this thread be moved across to there, then it can be arranged.
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Joe - so would I. The battery will be date-stamped, either explicitly or by a code. If it is as old as the car it could well be on its last legs, whether fully maintained or not. A few batteries go for 10 years, but not many, especially if the engine is started many times a day.
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