[PUP] Energy resource management

[2elnav at netbistro.com]

A point of clarification. I was only thinking of solar as a trickle charge
to top up the battery bank in float stage. There is no way you  can
achieve anywhere near a good bulk rate with solar. The boat cannot support
enough square footage area of solar panels.

There is another good reason for the split bank concept.  If you cannot 
provide enough charge current to get above the 0.2 X battery capacity A-H
capacity then reducing the bank size while bulk charging may be the only
way. Leece-Neville use to make a wonderful 300 Amp @ 24V alternator. They
still provide data sheets on the Prestolite website but the product line
(VLF)  is now listed as being discontinued.
I have one of these monsters and I know of a few more surplus units.
You may also be able to find  one of the bigger rebuild shops  with reman
units in stock.
However, there is another way. The trucking industry uses 160 amp
Leece-Neville alternators - at least on the older (pre 2000) trucks. Some
clever mounting using jack shafts and pillow bearings can provide you with
a 2X 150A = 300 Amp charging plant that can be driven by a coaxial flex
coupling and drive shaft.

John also wrote:
> "That's ~8kw, net of house loads and charger efficiency losses --
> probably need 10KW with only light house loads on the DC system just to
> charge".

REPLY
Quite true, but that is still only about 15 HP of power from the engine.
If you have a 25HP or larger wing engine, its quite doable.

regards
Arild


---------------------- original message --------------------------

> There is a downside to long, slow charging, at least when it comes to
> AGM batteries, which would be a big issue with solar. Lifeline (and I
> assume this applies to all low-resistance AGM's) is very specific that
> for repetitive charging, you should charge at a rate of 0.2 x battery
> bank capacity in amp/hours, otherwise you'll lose capacity over time.
>
> So you get clobbered on both ends if you aren't careful. Here's the
> link:
>
> http://www.lifelinebatteries.com/manual.pdf
>
> In my case, when I parallel all 12 batteries, I've got 1530 amp/hours
> capacity at 24v (charge relays automatically connect thruster
> batteries to house bank during charge). Per Lifeline, I should have an
> initial NET (after house loads) charge current of AT LEAST 306 amps,
> with a maximum of 5x capacity -- a staggering 7650amps (you really
> can't charge these batteries too fast). Between my Xantrex 4KW
> inverter/charger and two additional Mastervolt chargers (each rated at
> 50amps at 24v), I can't get above 220 amps at 24v.
>
> Guess I need to add yet another 100 amp at 24v charger. Good news is
> that its more load for the genset (makes it more efficient) and
> shortens bulk recharge time.
>
> But that said, I've never met anyone who could achieve a 320amp charge
> rate at 24v on their boat (640 amps at the usual 12v). That's ~8kw,
> net of house loads and charger efficiency losses -- probably need 10KW
> with only light house loads on the DC system just to charge.
>
> It also says that bringing the house bank back up with my engine-
> driven 170amp at 24v alternator is a recipe for short battery life and
> short alternator life. Which says I have to do the bulk charge with
> the Genset even if I'm underway. Not many people think of doing that
> when pulling out of an anchorage with a half-depleted house bank.
>
> And clearly, if you go to solar charging, stick with old-fashioned
> flooded cell batteries. You can't get enough amperage for a large AGM
> bank unless your whole boat is covered in solar cells. Even then...
>
> Arild is right... energy management gets to be a huge deal if you need
> a lot of power. And the idea of split battery banks sounds better all
> the time.
>
> John Marshall