I agree with the separate 12v system. You always have it on standby in case
you need the bilge pump or the VHF radio. And the 72v to 12v converter on my
GEM car is the biggest hassle on board.
And if you have your druthers buy a 4-12v bank charger so each battery is
charged separately. Just loading the bank with a 48v charge will lead to
uneven charging like my GEM (which is coming out with balancers).
Byron
-----Original Message-----
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
On Behalf Of dennis wolfe
Sent: Sunday, February 13, 2011 9:03 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] 48V to 12V
I would not tap one of the batteries unless you have a charger with four
separate 12v outputs. Tapping one battery for 12v will cause that battery
to discharge more than the other three. One charger in series will not be
able to fully charge that lower one.
A separate 12v battery just for 12v loads is the most conservative
electrical solution but means you need an extra battery and charger - a
heavy, expensive, bulky choice
A 48/12 converter is cheap, light, small, works just fine. Be sure to turn
off the master circuit breaker (or switch) when not using the boat and any
parasitic drain from the converter will be unnoticeable.
Denny Wolfe
www.wolfEboats.com
----- Original Message -----
From: "John Green" <v_2jgree@operamail.com>
To: <electricboats@yahoogroups.com>
Sent: Sunday, February 13, 2011 4:18 AM
Subject: [Electric Boats] 48V to 12V
> Hi, This might depend on usage. There is always a tendency to try to do
> things 'properly' which in this case means setting up a 12 v circuit for
> the pump that doesn't detract from other needs.
> If the boat is generally dry, and the pump is just there for 'what if' a
> leak occurs, then perhaps you can just tap the bilge pump off a single one
> of the 12v batteries.
> You might also consider mounting the electric bilge pump/float switch a
> bit higher, and having a manual bilge pump for the lower levels, the idea
> in both cases being that the electric pump seldom if ever runs anyway.
> As a side comment, it was pointed out to me on another forum that there is
> little point in having a small bilge pump - to be of good practical use, a
> boat like mine, at 26 feet long, should have a 2000 GPH pump!!! - an
> example was given of flow rates if a through hull fitting sheared off, or
> water cooling hose for the ICE came off.
> Unless the boat takes water all the time, I can't see any point in a
> dedicated battery.
> This may not be the 'proper' way, but it might be the most cost effective,
> easy to do, and practical.
> John
>
> 5a. 48V to 12V
> Posted by: "MartiT" mthorkilson@yahoo.com mthorkilson
> Date: Sat Feb 12, 2011 7:20 pm ((PST))
>
> I'm installing a electric inboard in my little 20' wood sailboat.
> The original gas inboard did not have a generator/electric starter.
> For that matter, there was no electrical system at all. The
> replacement will be powered by four 12V AGM batteries connected in
> series to power the 48V motor. A 15A 48V charger is also going to be
> installed. I want to install a 12V electic bilge pump in the boat.
> What are my options? Can I install a 48V - 12V converter and then
> wire the pump directly via a fuse? I'm not keen on another (heavy)
> battery dedicated for the bilge pump.
>
>
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