"Jeff" wrote in message
...

Finally I got an EchoCharge for about $100

The starting batteries get an appropriate trickle charge whenever a
charge source is
available, and everything is disconnected otherwise. The starting
batteries virtually never present a large load, so there is no
noticeable "kick in" of the EchoCharge.

So perhaps this would work in my case? If my house bank gets up to 13v
before this kicks in, and starting battery is at 12v or less, hopefully with
my small alternator, voltage does not drop below 13v causing cycling?


I don't like the diode isolator solution, because of the voltage drop
which means you have to raise the voltage in the regulator to
compensate. And it seems you're just converting some of your juice to
heat.

Yes, this is least attractive good option.

As for adding a "120 Amp alternator," your battery bank will
not accept that much power. Even with a smart regulator, it would
only accept about 50 Amps. On the other hand, your 55 Amp Yanmar
(actually probably Hitachi) alternator probably only puts out about
25-30 Amps, because it has a simple built in regulator. The new
alternator would want a smart regulator, so this is adding up to a
serious upgrade - if you want thoughtful advice on this you'll have to
tell us want you plan to power with this!

Presently, the boat (32 foot sail) would be used for short cruises - maybe
up to a week long. It will have new refrigeration that will draw 4 amps when
running and hopefully no more than 40AH per day. Other loads are lights,
radios, instruments, Autohelm (seldom used), windlass (not presently
connected). I expect I will have to run engine for a couple of hours per day
or get back to shore power.


The Honda generator is not a bad way to go, I've been on the verge of
getting one for a few years. The output is much higher than 10 Amps,
because you can feed the AC output into your battery charger.

I would like to get one too. I could probably sell the idea to the
"management" as a safety item for home power back up next time we have an
ice-storm or other unforeseen power outage. On the boat, our engine does
not have a heat exchanger, and I have considered this as a way of producing
hot water - Run the generator for a while - charge the batteries and heat
the hot water. A bit of an expensive solution, but a nice-to-have!

Thanks for the input

GM



GBM wrote:
I was thinking about adding a battery combiner to my boat's electrical
system, but I may have to rethink this.

Present System
------------------
Bank 1 - Starting battery
Bank 2 - House - 2x6V Trojans (225AH)
Shore power charger - 2 bank Truecharge 10 charger connected direct to
batteries with fused leads
Alternator - 55Amp on Yanmar 2QM15.

Presently, my alternator charges back via the starter motor cable. It
leads
to the common terminal of the "red" 1-2-All switch. The batteries are
connected to the other two terminals in the usual way. So, I can chose
to
charge either battery or both. House load also connects to common
terminal
but also has it's own breaker switch.

1. Using Combiner
----------------------
I have looked at using the New Zealand made BEP VSR (Voltage Sensitive
Relay) as the combiner. But, in reading their website, they warn against
using such devices if the alternator and batteries are not matched. They
say
that for the combiner to work, the alternator must be larger (80-90A) or
the
batteries smaller (100-130AH). Otherwise, the unit will oscillate and
not
work properly.
http://www.bepmarine.com/showproduct.cfm?productid=12
http://www.bepmarine.com/products/inst-710-100a-vsr(web).pdf

Another supplier - Sure Power talks of same problem but says that time
delay
avoids chattering - But they don't provide details - Perhaps if
alternator
is connected to house battery, it may work better?
http://www.surepower.com/separator.html

West Marine do not mention this problem in my older catalogue.

2. Echo-Charge
-------------------
Another possibility is to use a Xantrex Echo-Charge.
http://www.xantrex.com/web/id/103/p/.../5/product.asp

Seems alternator is connected to House bank. Then when voltage reaches
13v
this unit actuates and then charges starting battery. No mention of
cycling
with undersize alternator. When unit kicks in, wouldn't voltage likely
drop?

3. Diode isolator
--------------------
Would work, but voltage drop would likely reduce battery capacity and
life.

4. Manual switching
-------------------------
That's what we do now! We have zap-Stop to protect alternator. But, it
is
easy to forget to switch the batteries.

5. New Alternator
---------------------
Installing a larger alternator (say 120A) would be an option, but with
single belt and a real HP output of less than 10HP at normal rpm, this
could
diminish engine output and perhaps put loads on engine that 'it's not
designed for. (The 55A is the optional alt. - normal is 35A!). Seems
overkill just to allow easier switching, but this would allow quicker
recharging of house batteries.

6. Portable Generator
--------------------------
This has passed my mind - Use a portable Honda to charge the house
batteries. But at 10A, this would require a long run!

Ideas, comments or condolences welcomed

GM