Friday, Jul 15, 2005 at 17:01
Ok,
At the risk of getting my toes crushed.
Firstly, whatever the alternator puts out is fixed, it will vary a bit, but there is nothing you can do about it. Connect a reasonably flat battery to a voltage source of 14V, it will take heaps of current, in fact it will make the output from the alternator drop a bit, say down to 13V and there will be about 40 amps going into the battery. After a short while (1/2 hour of driving) the current will drop back to say 20 amps and slowly, over a period of a couple of hours, it will drop down to 2-4 amps. It may take another couple of hours after that, before it drops to less than 1 amp and that is when the battery approaches full charge. At that point, the regulator voltage will be in the range 14 - 14.4V.
Now, the long lead going back to the trailer, and I will assume that it uses decent size wire and connectors, will limit the CURRENT, it will not limit the charge voltage at all. So, while it won't take 40 amps initially, it will take longer to charge, but when the battery does get nearly full, the resistance of the wire, which should much less than 1 Ohm, will not have any effect on whether you can full charge or not. It will take longer for sure, but in a day's driving, it should still fully charge to whatever it is capable of achieving with a given alternator voltage. With a sealed battery, it is also safer to err on the side of undercharge, as you cannot replace electrolyte if it boils off. Fortunately, most sealed batteries require a higher voltage to fully charge than the alternator puts out, so that will not be a problem.
As for sulphating, that is really only a problem if a battery is left discharged for a long period. If it is regularly charged and brought up to say 90% as it will be in a car, the heat in the engine bay will kill it long before it has a chance to sulphate.
I use Exide Extreme ZZ size and tend to get more than 4 years out of them. At 140 bucks... there is no advantage to pay for fancy batteries, except for the trailer where a fully sealed job maybe safer.
Cheers
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