----- Original Message -----From: chris BakerSent: Sunday, February 13, 2011 3:25 PMSubject: Re: [Electric Boats] 48V to 12VAnother option for supply 12v is tap one of the 12v batteries of the series (and don't worry Denny there's more...) and use a DC-DC battery equaliser.
This is a special DC-DC converter that converts at a 4 to1 ratio, rather than 48 to 12. The 48v side of the converter is connected to the 48v pack, and the 12v positive lead is connected to the 12v tap (which needs to be the battery whose negative pole is the 48v negative.)
This equaliser sits there minding its own business until it sees a mismatch between the 12v and 48v. That is, if the 12 v side has a dropped to lower than 1/4 of the 48v side it will direct power to the 12v battery until it comes up to be equal again.
The cool thing about this is that you can have large transient loads, such as a 12v anchor winch, because its pulling the current out of the battery but which would otherwise be far too much current to be supplied direct by a dc converter. Then the equaliser can take its time about balancing them again.
Another thing I like about this is that it is bidirectional. If the 12v side is high, the current will flow to the 48v side until it is equalised. The point of this in this discussion is that it has been mentioned that a dc converter does draw some small amount of power all the time, even if it has no work to do. So the option of adding a small 12v solar panel to account for this load is still possible. And it will keep the whole pack topped up, not just the 12v tap.
You can get these from Solar Converters at http://www.solarconverters.com/eqlist.html
I've order one of these but it hasn't arrived yet and so I can't offer any experience of its performance.
Cheers
Chris
No comments:
Post a Comment