T&T: Whole new electric system

[Candy Chapman and Gary Bell]

As I just said in a message titled "Batteries," I presently have two 
West Marine Sea Volt GC2 golf cart 6volt wet cells in series for my PDQ 
34 power catamaran house bank (200 AmpHours -- pretty pathetic compared 
to most everybody elses' banks, but that's all the boat designer left 
room for!!).  Since my accursed Prosine 2K went disastrously TU a while 
back I am looking forward to a whole new system, featuring a Victron 2.5 
kw Phoenix, and I think I'll bite the bullet and get four 12volt AGM's 
for the house bank, partly so I can tuck a couple more in where they 
would be hard to water.  PDQ power cats are notoriously touchy about 
weight and balance, and I can't think of a suitable larger place to move 
my house bank.  I only have a 'few' more cereal box tops to save up -- 
poor timing buying a Victron with the US dollar plunging, but I think it 
is still the best choice.   

I know, I ranted at length against parallel banks in the past, and I 
still feel there is a significant risk of shorting a flooded cell in a 
parallel bank and having that battery hog the charge out of it's 
neighbors and overheat -- a nasty situation a couple of list folk have 
actually reported.  I feel AGM's are mostly immune to that risk because 
their plates are already packed snugly together with insulating 
fiberglass mats saturated with electrolyte between them, making buckling 
and spalling problems very unlikely and virtually harmless if it did 
happen.  In my case, I can presently get only two wet cell golf cart 
batteries into the factory space, so that they are still available for 
rewatering without cutting a new hole in the deck, or I can stuff four 
AGM's in and get eight times the charge acceptance rate (four times from 
upgrading to AGM and two times for doubling the size of the bank).  I 
can forget about rewatering and slip over to monitoring volts and 
amp-hours with an occasional visual and IR thermometer inspection; never 
worry about spilled electrolyte, etc. etc..  

My Bold New Plan also calls for adding two more remote batteries:  (1) a 
biggish single AGM start type way up forward to start the genset and run 
the windlass, with a nearby small independent charger, and (2) a deep 
cycle AGM under the flybridge to provide power for the VHF and SSB 
radios -- completely isolated from the rest of the boat, and with 
another small independent charger nearby which is fitted with a relay to 
automatically disconnect this charger when either radio is on -- 
eliminating noise issues on the radios as well as to and  from 
everything else on the boat.   I plan to use the automatic combiner I 
already have (and the heavy cables formerly used to bring 12 volt 
windlass power forward) to provide emergency support between the 
genset/windlass system and the house bank/Victron.   I will provide a 
small charger for the two independent start batteries and add a manually 
switched fused jumper between them.  They will remain the 'no 
maintenance' semi-sealed automotive flooded cell batteries, and not 
connected to the house bank. 

I have (and love) three of those portable power boxes, the jumpstart 
battery, trickle charger and tire pump, etc. that I keep one charged 
aboard.  In addition to all that, I keep a size 31 deep cycle flooded 
cell in a portable battery box for the electric trolling motor fitted to 
my dinghy, to run my 3700 gph emergency pump, to run the little dinghy 
dewatering pump I use around the marina, to run work lights, to run the 
Admiral's 12 volt hair dryer thawing pipes, or whatever I think of next. 

At the same time I want to install independent 12 volt and 120 volt 
outlets in every accessible space aboard for work lights, power tools, 
emergency pumps, etc.  without extension cords running through 
unclosable hatches and doors.  

Listees, feel free to sharpshoot my plan.  I have mostly book learning 
and less real experience at some parts of this.  I want a safe, 
versatile and effective system and I also want to spend my boat bucks 
wisely. 

Regards again from that old drone,
Mister Science (Gary's name when he is on his soap box)