Saturday, May 07, 2016 at 14:49
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Sorry Boobook, I must disagree with your comments re dc-dc chargers compared to simple isolators. They both have their merits but it is wrong to describe a dc-dc charger as a "huge negative".
The standard automotive alternator is basically a simple fixed-voltage charger. It maintains a fixed output voltage throughout the charging cycle. This is not unreasonable for charging flooded lead-acid cranking batteries where they are discharged very little during an engine start procedure and the recharge lasts for only a few minutes but is less than ideal for replenishing
well discharged deep-cycle batteries. This "fixed output voltage" may be modified in magnitude by modern Engine Management Systems to satisfy emission considerations but still remains as a fixed-voltage charger.
On the other hand, dc-dc chargers invariably incorporate an algorithm that provides multi-stage charging which is acknowledged as being appropriate for deep-cycle batteries, particularly AGM type. They also have the benefit of limiting the charge current to a value nominated by the battery manufacturer. An additional advantage is that this bulk-charge current can be maintained throughout that phase whereas a constant-voltage charge will diminish as the battery voltage rises.
Certainly, direct alternator charging may bang the joules into the auxiliary battery rapidly, but is this good for your battery?
To address your 4-points of question:
Can you jump start.......? Yes, I have a 200A solenoid which can connect my Aux Battery with the cranker.
Can you join batteries for winching? Yes, same as above.
Are the electronics sealed? No, they don't need to be. My dc-dc's are in the cab.
Does the retailer make more money? A very good question indeed. The commercial "Diode Boosters" are comprised of components costing less than 50 cents yet are marketed at $50 each. I would say "You go figure".
My two 20A dc-dc chargers maintain my auxiliary batteries
well and their life appears to be extending much further than when they were connected directly to the alternator via a solenoid isolator.
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