Thank you for the excellent inputs Ben.
It is 22:30 and I just got home from a friend's retirement party.
Although we have been drinking ouzo all night I will try to explain what
I thought would be a typical daily battery charging scenario in terms
of labor required by the sailor :
1. Start the engine, and let it accelerate to the optimum charging speed.
2. Either watch your ammeter or get an audible alarm from your DC/DC
when the battery voltage levels of at its maximum amplitude.
3. Shutdown the engine.
4. Flip the battery switch to bank#1 on odd days and bank 2 on even days.
5. After less than eight hours the DC/DC will beep again indicating it has done
its job.
Simply flip the battery switch back to "BOTH"
Not too complicated if you ask me.
The DC/DC is designed by the cruisers for the cruisers so it will do exactly
what we want it to do.
The DC/DC will survive with input shorted, output shorted, or the input shorted
to output.
As Ben said, a couple of comparators in the DC/DC detects battery switch
positions
and enables the DC/DC when bank#1 or #2 is selected. DC/DC shuts itsself down
in all
other battery switch positions automatically. No fussing from the user is
required.
No need for extra batteries. DC/DC uses an average of less than 300mA per day.
Can we buy the 12Vdc to 15Vdc DC/DC instead of building one ?
I would love to buy it instead of building it but I don't think we can find one.
Anybody who knows a part number please speak up.
More later.
Thanks again Ben.
> From: [email protected]
> Date: Thu, 5 May 2011 11:09:01 -0400
> To: [email protected]
> Subject: Re: [Liveaboard] Ahmet's Equalizer
>
> On Tue, May 03, 2011 at 01:07:33PM -0400, [email protected] wrote:
> >
> > A postscript to my latest message describing Ahmet's Equalizer.
> >
> > I thought Ahmet was quite clear in his explanation of the device he had
> > come up with. It was clear to me at least.
> >
> > "A very efficient DC/DC power converter (after a bulk charge with the
> > engine or Honda 2000)
> > takes the energy from one battery bank and slowly tops up the other house
> > bank. Next day
> > the process is repeated topping off or equalizing the other house bank"
>
> It sounds like a reasonable idea - although you want to be aware that
> you're trading a certain amount of battery life (by cycling the
> batteries more than you would otherwise) as well as battery capacity
> (since a fair amount of that capacity is now going to be used for this
> job) for this ability. If you're already fully exercising your banks on
> a daily basis, you'll need to add more batteries.
>
> Also, unless I'm mistaken, this presumes that you're only going to draw
> from one bank at a time - i.e., that you have at least double the
> capacity that you use for your daily needs (a *highly* doubtful
> assertion for most cruising boats.) Even if you do have that capacity,
> the question is, which bank will you use for your daily energy needs? If
> it's the one that you're charging from, then you'll be loading that bank
> pretty heavily by pulling both what you need *and* the charge current
> for the second bank (i.e., each bank will now need to be powerful enough
> to supply your needs and to charge the other bank.) If, on the other
> hand, you're going to draw from the one being charged, then that bank
> will never get fully charged. Perhaps I'm failing to understand the
> usage scenario here.
>
> Next, this system will need a variety of sensors that would cut it off.
> E.g., when the two banks are tied together via a "Both" setting on the
> battery switch (this would short the input of the converter to the
> output - perhaps not the most desirable scenario. :) You also probably
> don't want this operating when the engine is running (maybe not - I'm
> not very clear on that design goal) and maybe when there's a large load
> on either one of the banks (you'd need a shunt for each bank, a pair of
> comparators matched to the shunts, and some serious brain sweat put into
> figuring out what "large" means in this case. It would be different for
> each bank capacity/load combination.)
>
> Overall, it doesn't sound like a big problem to build one, especially
> since you can get good quality, high-current boost converters fairly
> cheaply these days - no need to design or build them yourself, like you
> had to in the 70s or early 80s. Again, the problem that I'm seeing is
> that of usage, given the typical battery use on a cruising boat. I may
> be wrong, but it seems like you'd be fussing with the thing all the
> time, and having to make decisions about what to do with it on a daily
> basis. That, in my experience, means that it just won't get used after
> the first week or so.
>
>
> Ben
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