

| Subject: | charging aux battery: too much of a good thing? |
| From: | Ian Allan |
| Date: | Tue, 20 Apr 2010 21:03:46 -0400 |
Mark: Congrats on the Bostig. Very intelligent:-) I think that the Ford alternator is 105 amp. Much more than that needs a serious drive pulley. I think that there should be an ID tag on the alternator with that info. So far as the batteries are concerned I think you are good to go. Don't change a thing unless you find that the batteries are quite hot to the touch or you have to add water on a regular basis. To get a lead acid battery to full charge you need voltage in the high thirteen to low fourteen volt range/ 13.6 won't cut it but will never hurt the batteries. The real test is to apply a digital voltmeter across the battery terminals after the engine has been running for at least 10 minutes. Hey, here is a little caution with the Surepower. Be aware that after shutdown and pulling the neg. terminal on your main battery, the batteries remain banked for some time. I think from 2 to 5 minutes before the Surepower switch isolates the batteries from each other. > Today I was able to fire up my 3 battery system for the first time. A > dedicated 125 amp hour deep cycle was added for the Vitrifrigo fridge > only. With the Zetec it fits easily in the engine compartment and is a > foot from the alternator. I used short #6 wires with a Surepower 1314 > between the alternator and the battery, and ran #6 between the neg > post > and the engine block. > > As part of this setup I added an amp meter for the fridge battery so I > could see how fast it was charging and then know how long I needed to > run the engine to get another night of camping. I was surprised to see > the meter reading over 60 amps going into the battery when I first > started the engine even though the battery was fairly full. This > quickly > tapered down over a few minutes to a steady 25 amps. I wonder if > maybe I > have too much charging? > > I have not been able to pin down the capacity of this Ford > alternator. I > have seen it listed as 105 amp, 115 amp, and 130 amp. I don't care > much > either way as 105 would be plenty but it would be good to know. I am > measuring 14.5+ volts at the alternator which I believe is pretty > common > with modern vehicles but I wonder how good it will be for the battery > long term. I could slow down the charging rate by switching to longer > and thinner battery cables but this would not drop the voltage much > after the battery was full. That seems too high for a "float charge" > but > I don't know how it will be in practice. Anybody know? Suggestions? > > > Mark > Ian Allan 94 Eurovan Westfalia 86 Syncro 85 Westfalia/Bostig 84 Westfalia 02 Jetta 1.8t
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