[Sentoa] Domestic power

FFB13 at aol.com FFB13 at aol.com
Sun Nov 6 08:42:38 EST 2016

the reasons i have a northern light 6k generator in my  32'
and food for thought to some  .......
I keep my boat in key biscayne fla.---hot hot hot  .. 
and i turn on my generator every time i go out .why  ??   the weather    
need to run my 2  a/c's---
and when i go to Bimini , or the keys ,or bahamas in  summer i arrive there 
fresh and cool and stay so.
also my refrigerator .. i gave up with the expensive  dual (inverters for 
battery use and electricity )  refrigerators and  just went out and got a 
$250.00 refrigerator from sears ...and have had  it now for 7 years or so ...my 
previous 3 refrigerators with the built  in inverter and high price ( over 
$2.0 ) did not last as long  .
additionally, when i keep the boat behind my  house  the generator serves 
as a back up to my home's electrical panel in  case of storms when we may 
loose our electricity . ( i had a conversion made to  my electrical panel, and 
an outside plug placed in my rear wall facing the  dock and a 110 foot cable 
(very heavy )...)it will give me enough electricity  for 2 spare a/c wall 
units (not for central air )
lights ,ceiling fans 
and i supply my neighbor with electricity for their  refrigerator and a few 
lights .
and of course a complete check list on how to turn it  on and connect it to 
the panel  to prevent damage to others and my house  .
32 ft #36
In a message dated 11/6/2016 7:53:59 A.M. Eastern Standard Time,  
sentoa at lists.sentoa.org writes:

-----Original Message-----
Date: Sun, 6 Nov 2016 07:53:13  -0500
From: Dave Jones <senojev at aol.com>
To:  sentoa at lists.sentoa.org
Cc: dave at tek5systems.com
Subject: Re: [Sentoa]  Domestic power


You raise a number of questions with your request for  generator advice.

In answer to part of your questions, you need new  batteries if you are 
sure they are toast. 

Should you have a generator?  It depends on a number of factors. If you 
never leave the dock, a genset does  not make sense assuming you have shore 
power. If you only travel marina to  marina, other than some very hot days, a 
genset is not really needed. If you  anchor one or two nights at a time, you 
can get by without a genset if your  battery bank is properly sized - 
assuming A/C and a good supply of hot water  is not required. If you anchor for 
extended periods of time (no engine  running), you need some way to charge 
your house bank unless you have a huge  battery bank. A genset is one way to 
achieve this. An alternative is to use  solar panels of the right size to keep 
your house bank charged or limit its  discharge. Relying on running the 
main engine at anchor to charge batteries is  not good: it will be so lightly 
loaded that it will not reach a good operating  temperature. The standard 
alternator, although rated at 125 amps, for example,  is only producing a 
fraction of this at low rpm and ideal temperature  conditions. Unless it is 
converted to external regulation, it does not provide  optimal charging 
characteristics for a house bank. It is only designed to keep  up with the loads you 
normally see in an automotive application, such as  lighting, heater motor, 

You should start your decision making by  doing an analysis of what your 
power needs really are. There are several ways  to do this - the best being 
actual data if you have some type of battery  monitor so you can measure daily 
usage. Failing that, make an estimate of all  of the loads on your house 
bank and duration to come up with a daily  consumption and what it is 
projected to be. Plan for the future: are your  cruising plans likely to inlclude 
the Loop. For example, you run interior  lights totaling 96 watts ( or 8 amps 
draw) at 12V for two hours a day = 16  amps/day; run stereo drawing 4 amps 
for six hours a day =  24 amps/day,  etc. Include as many loads as you can 
including water pumps. Add in any  intermittantly used 120V items such as a 
microwave, TV, coffee pot and reduce  the consumption to12V ..... a 1200 watt 
microwave used for 15 minutes a day  uses 25 amps/day via the inverter. Sum 
all these loads to arrive at a good  approximation of your daily needs. 
Based on several years of typical cruising,  we use around 200 amps per day from 
our house bank.

The load analysis  will give you at a good idea of how to size your house 
bank. The house bank  should not be discharged to less than 50% of its 
capacity on a regular basis  before recharging. Occasional discharge to less than 
50% is OK but should be  avoided. Battery life is closely linked to depth of 
discharge; the less of a  discharge, the longer the life ... almost a 
straight line relationship.  Another issue with deeper discharges is the amount 
of time it takes to  recharge the battery bank. If you use 200 amps from a 
400 amp bank and your  charger is rated at 100 amps, it will take more than 2 
hours to charge the  bank to 100%: probably close to 2.75 hours. Not 
charging the bank to 100%  regularly shortens its life significantly. A good rule 
of thumb is to size the  battery at 4 times your daily needs, i.e. if you use 
200 amps per day, the  bank should be 800 amp capacity. This means you can 
run two days without  charging but remember you will have to put that 400 
amps back in  somehow.

How to put back that 400 amps is another decision point.  Disregarding the 
engine alternator option, there are only two ways to do  this:
    *   A genset with a large inverter/charger. Do not make the  mistake of 
getting a stand-alone inverter and relying on the wimpy 40 amp  charger 
likely installed by the factory.  
    *   Solar or windpower  
    *   A combination of the above

Solar should be given strong consideration for several  reasons. It is 
relatively inexpensive to buy and install, requires little to  no maintenance, 
is silent and unobtrusive, and requires little attention. On  our 37, I have 
two 310 watt panels which would probably fit on a 32 pilot  house roof. On a 
reasonably clear summer day in the northern US, I can top up  my 880 amp 
house bank by noon or early afternoon. If I time my use of AC  loads, I could 
even run the hot water heater for 20 minutes and still make  that up by 
nightfall. My system ran around  $1800 self-installed in one  day, The cost was 
reduced significantly by taking the energy related tax  credit available at 
the time (think this has been extended) as the boat  qualifies as a second 

Wind power is also an option but has some disadvantages such  as noise and 
can be obtrusive. It does have some advantages including the  possibility of 
round the clock generation (if there is a wind). Combined with  solar it 
may be a good combination.

A genset in combination with a large inverter/charger (2500  watt 150A 
charger) is the only way to go if you anticipate high longer  duration AC needs 
such as A/C and electric oven or cooktop. This option is  expensive and 
takes a significant amount of space. A 5kw genset would be in  the ballpark of 
$10,000 installed last I heard and may well be more. Add in  another $3,500 
for the inverter/charger and you are talking big bucks.  Depending upon your 
engine room layout, the install may be simple or complex  if the factory 
used the space tradtionally occupied by the genset. If you  choose this option, 
size the genset appropriately based on your load analysis;  underloading 
the genset is as bad as underloading the main engine. A 5kw  genset would 
probably be adequate for your needs. Do not undersize the  inverter/charger 
(especially the charger side) as you want to have the highest  capability 
possibility and the incremental cost for the greater output is  small.

Your new house bank should be capable of being charged at a  higher rate 
than any available charger. For Lifeline AGM batteries, they  recommend bulk 
charging at no less than 0.2 x the bank amp rating, i.e, 80A  for a 400 amp 
bank, to avoid any loss of life. Charging to 5x capacity is  possible with 
AGMs. Flooded lead acid batteries should also be charged at a  similar minimum 

Regarding the use of a genset in an anchorage brought up by  another 
responder - do not worry! A modern genset with a good sound enclosure  and exhaust 
system is almost silent a boat length away.

In conclusion, you need to determine what your current and  projected needs 
are and then design an electrical system to meet those needs.  IMHO, a 
small genset in combination with a large inverter/charger and solar  panels is 
the ideal solution.

Hope this helps you decide what to do.

Feel free to email me if you want to discuss anything  more.

Dave Jones
NT 37-212
Sir Tugley Blue
Wintering in Brooklin, ME

-----Original  Message-----
From: Al Johnson via Sentoa  <sentoa at lists.sentoa.org>
To: David Denu  <dave at tek5systems.com>
Cc: Al Johnson  <johnson.alan.b at gmail.com>; sentoa  
<sentoa at lists.sentoa.org>
Sent: Thu, Nov 3, 2016 10:48 pm
Subject:  Re: [Sentoa] Domestic power

Attached  Message
>From Al  Johnson <johnson.alan.b at gmail.com>  To David  Denu 
<dave at tek5systems.com>  Cc sentoa at lists.sentoa.org  <sentoa at lists.sentoa.org>  Subject Re:  
Domestic power  Date Thu, 3  Nov 2016 22:47:43 -0400
Have you considered solar panels? A friend just  added two panels to his 
sailboat (for a bank of four batteries) and has more  power than he knows what 
to do with. He is also based on Lake Champlain.

Al Johnson
Nuthin' Fancy
Williston, VT

Sent from my iPhone

On Nov 3, 2016, at 8:56 PM, David Denu <dave at tek5systems.com>  wrote:

It's becoming winter here in Vermont and the Tug is on the hard and  
winterized (I hope).   
Anyway - my house batteries have morphed into serveral hundred pounds  of 
useless dead weight. They won't hold a charge more than a few  days. 
The setup on my boat is like this:
- House batteries two 4D wired in parallel
- dedicated diesel starter battery 
- two large-ish (group 24?) batteries in parallel for bow  thrust/windlass
That's a lot of batteries. 
As it sits, there is no 115v unless connected to  shore power. So, I'm 
thinking about the option of  retrofitting a generator into my NT32. The other 
option is new batteries and  a decent sized inverter.   
Obviously a generator is beaucoup dollars, but we would have all  the 
modern conveniences (microwave, AC) at anchor. 

Anyone know how much of a challenge it is to do the work? Open to other  

Dave Denu
Respite NT32
Charlotte, VT

Sent from a mobile device  ...

Sentoa  mailing list
Sentoa at lists.sentoa.org

Sentoa  mailing  list
Sentoa at lists.sentoa.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sentoa.org/pipermail/sentoa_lists.sentoa.org/attachments/20161106/85a9915c/attachment-0002.html>

More information about the Sentoa mailing list