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My BIL is an auto electrician and he was telling me recently that most new batteries are fitted to cars in a lowly state of charge. This then puts excessive strain on the alternator, which in many cases results in the unit overheating & prematurely burning itself out. One questions whether some unscrupulous garages are knowingly carrying out this practice with the view that the customer will be back later requiring a new alternator. So if you are a DIYer, it would make sense to ensure your new battery is fully charged before fitting it into your vehicle.
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Is this really a problem for the alternator, then, having to charge the battery one time only from partly-charged?! This must be expected to happen many times in a car's life. No?
-Mark
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Some batteries are less than 40% charged from new and this places a very high demand on the alternator especially Winter time when there is already a heavy loading with the use of electric rear screen elements, heater fan motors, main headlights and perhaps foglights along with all the other ancillaries, so much so that the alternator has to operate at max capacity over an extended period, which leads to the failure - most of his business arises from this situation after a recent battery change.
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Nothing to do with the fact the battery was changed because the alternator was on its way out anyway then?
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I very much doubt alternator will worry too much about it.After all alternator runs all the electrics all the time.only time battery is needed is if the alternator cannot cope with demand then power is drawn off the battery as well.but then if alt cant take it time to replace.
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I was merely relaying comments from my BIL and after 40 years running his own successful business, I suggest that over that period of time his experiences have proved this to be the case.
Obviously in some instances the alternators could be nearing their replacement time, but the point I was trying to make is that their serviceable life could be extended by many thousands of miles merely by ensuring a replacement battery is fully charged to 16 volts.
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Your comments were noted.I dont dispute what you said.As most cars during a lifetime have only 2/to/3 replacement batts I doubt it is a prob.ps could be wrong but I havent yet seen a 12 volt bat reading 16 volts-14.5-14.8 yes.as I say may be wrong.I stand corrected if so?
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My BIL is an auto electrician and he was telling me recently that most new batteries are fitted to cars in a lowly state of charge. This then puts excessive strain on the alternator,
So what is this "excessive" strain?
Alternators are designed to cope with the full electrical load of the vehicle and re-charging a battery in a low state of charge is a normal requirement.
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I agree with the sceptics here. You cannot "strain" an alternator. The output current is self limiting. If you try to draw more than the alternator can give the output voltage simply drops and the current levels off. The battery will then share the load. This happens every time there is a heavier load than the alternator can supply; for example: on most cars at idle with everything switched on. At low speeds the alternator output drops.
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A battery reading of 16 volts after being fully charged is not possible. 16 volts on charge implies a high internal resistance normally due to a fault or a very old, dead battery or the battery is very hoy 50 to 60 degrees C not good. The other way to get 16 volts is to bash 100 amps into it but you can say goodbye to the battery as the plates distort and can cuase shorted cells. 14.75 to 14.95 max is where a decently charged battery sits and disconnected and left for 2 hours will give you 13.2 to 13.4 volts and 12.6 to 12.8 after 12 hours. Most batteries these days are dry charged, that is to say they are filled with the appropriate specific gravity electrolyte and not electronically charged. This gives rise to the "Not fully Charged Theory" and yes in my opinion and by experience they are not fully charged. The cranking current figure will rise by some 20% if the battery is topped by charging for 12 hours at 1.5 to 2 amps. However this slight undercharge will not cause an alternator any strain and is no different than leaving your car for two weeks with the alarm set whilst you are on holiday then coming back and starting your car. I personally always charge a new batteries for a day at 1 amp and test them for compliance to the spec ( Cranking Current etc ) before fitting. OH yes there is another way to get 16 volts, its a duff meter your using. Regards Peter
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A fully charged wet lead acid battery in good condition can range from 12.22-13.15 open circuit volts depending on eletrolyte temperature, plate chemistry etc. Open circuit volts means no load on the battery and negative lead disconnected.
For a typical low maintenance sealed battery (but excluding AGM and gel types) at 21 degrees centigrade and 100 percent charge (but with no surface charge) will read 12.66 open circuit volts and the average specific gravity (relative density)of the cells should be 1.261
Surface charge (which gives rise to false voltage readings) exists after charging but will dissipate over some hours or can be removed by applying a load to the battery (switching on the lights for three-four minutes) and then waiting 10-15 minutes.
A 50 percent charged battery at same temp will read 12.25v and SG 1.186 and a 25 percent charge will show 12.07v and SG 1.151
A fully discharged battery would be 11.9v or less
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I have noticed that places like Costco and Halfords sell filled batteries, but some Motor factors and battery specialists take empty batteries out of the box and decant acid into the all the cells, I once had one of the latter and it seemed fully charged as soon as it was filled. The shop had a 10 foot round tank on the roof with CORROSIVE signs/symbols.
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I agree Tailpipes as long as the electrolyte is the correct SG then the battery is effectively fully charged and you would not know the difference. As I said charging them justs tops up the Cranking Current figure and tests the battery. Dry fill batteries have the advantage that it is not a battery from last winter that has been in stock and the acid slowly eating away at the plates. Mnay Battery specialist do it this way as they have all the appropriate H & S procedures in place. Some motor factors and Retail outlets do not consider it appropriate or safe to have dilute sulphuric acid tanks, acid proof overalls, goggles and gloves and training all the staff in procedures and Health and Safety. Regards Peter
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Just a bit of motoring memorabilia of passing interest:
Long, long ago, when people often used to lay up their cars in the winter, one of the procedures was to dry-store the battery. This consisted of charging it, dismantling, drying and storing the individual cells, draining and storing the acid.
In the spring, the casing was cleaned out, the cells inspected, cleaned, replaced as necessary, the acid filtered or renewed, the whole put back together and the top re-sealed with bitumin or wax.
Not now much used by family motorists I suspect, but probably still applicable in industrial, railway or marine use in large installations.
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