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Turning the key off; Changing the battery switchdavid10-21-03  12:09 am
Maintaing good connections at the batteriesDavid Sheriff04-04-05  12:25 pm
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David Sheriff
Board Administrator
Username: admin

Post Number: 79
Registered: 01-2004
Posted on Saturday, January 13, 2007 - 09:29 pm:   Edit Post Print Post

If the location is below decks and shielded from the weather butt
splices applied with a proper crimper will be very reliable. Tug on
each splice to make sure the wire is well captured. I recommend
staying with the original wiring scheme to avoid trouble. In other
words, no extending a red wire with a yellow one. Finally, its
usually better not to string butt splices in series. If there is
already a splice in a wire close to where you want to extend it, cut
that one out so you don't leave in old things needlessly.

Goo is worse than worthless. it rarely waterproofs completely and it
makes things very difficult if you ever want to troubleshoot the
system. If you want to waterproof the splices, use the special
heat-shrink connectors with the adhesive built-in. Then make sure you
heat each one until the adhesive actually melts and flows around the
wire. The wire insulation has to be reasonably clean too.

I think properly applied butt splices are more reliable than soldering
and heat shrinking. This is mostly because its easier to master a
crimper than a soldering tool. And by a crimper I mean the kind that
the manufacturer's recommend, not just mashing the connection with an
electrician's pliers.

David Sheriff
Board Administrator
Username: admin

Post Number: 78
Registered: 01-2004
Posted on Saturday, January 13, 2007 - 09:28 pm:   Edit Post Print Post

From a recent email exchange:

Hello David, I have a Pacific Seacraft 44 and was hit and run by an island trader near Trinidad. The repair required taking out the Newmar electric panel and moving the wiring. Upon reassembling I find that there is not enough length in the wire to reconnect at the breakers or busses without splices. How do you recommend doing the splices--is it ok to have them inside the panel and under the plastic board. are butt connectors ok, should I use some goo around them?

David Sheriff
Board Administrator
Username: Admin

Post Number: 45
Registered: 01-2004
Posted on Tuesday, February 07, 2006 - 09:35 am:   Edit Post Print Post

Regarding battery disconnect switches and boat fires. ABYC standards require a battery disconnect switch for any battery over 800 CCA. There is no requirement that the switch be accessible outside the engine compartment, so it would seem the switch is mostly intended to prevent one from melting wrenches while working on the engine.

I think the real problemn in Hen Highly's experience Bucky notes below is the absence of proper fusing including a main fuse for the house DC wiring, which is very common. A reasonably sized fuse located close to the battery as the rules require will blow before the wiring will get hot enough to ignite anything. Every conductor must be fused at the source, which protects the boat from fire. This is frequently ignored, particularly with do-it-yourself owner modifications.

So, if you're looking for the battery switch when you have a fire, you probably should have properly fused things when you had the chance.

Ted Lavino
Senior Member
Username: Tlavino

Post Number: 165
Registered: 01-2004
Posted on Wednesday, March 24, 2004 - 10:03 pm:   Edit Post Print Post

Greetings All,

A great primer on batteries and charging systems:

http://www.windsun.com/Batteries/Battery_FAQ.htm#Industrial%20deep%20cycle%20bat teries

Kendall Bailey
Senior Member
Username: Bucky

Post Number: 50
Registered: 03-2003
Posted on Tuesday, March 02, 2004 - 07:22 pm:   Edit Post Print Post

Re. Battery disconnect switch
Some years ago while boating to Catalina, Ken Highley came across another boat on fire. He was able to knock the fire down with fire extinguishers, but the fire quickly returned. Electrical fire and neither the boat's crew or he could get to the battery disconnect switch due to the fire location and intensity. The boat was a total loss.

Ted Lavino
Senior Member
Username: Tlavino

Post Number: 108
Registered: 01-2004
Posted on Tuesday, March 02, 2004 - 01:51 pm:   Edit Post Print Post

Another great article on battery technologies specifically by Chuck Husick (formerly of West Marine):


Ted Lavino
Senior Member
Username: Tlavino

Post Number: 107
Registered: 01-2004
Posted on Tuesday, March 02, 2004 - 01:42 pm:   Edit Post Print Post

One question that seems to be endlessly debated is the tradeoffs of the three leading battery technologies in tersms of cost per amp of usseable capacity, time required to replenish a given useable capacity, and the longevity in terms of A/H in and out. At the risk of starting something here, my thoughts are as follows:

Flooded cells cost less per rated a-h than AGM or Gel, but are more sensitive to deep discharges. In other words the rated capacity of a particular bank is say 500a-h but my understanding is to maximize the useful life, you should not discharge them below 50% of their charge, leaving a useful capacity of 250 ah. On the charging side, my understanding is that the last 20% of the charge cyle takes a very long time to complete., which leaves us with about 30% of useful capacity on an ongoing basis (hence the rule of thumb to size the battery bank 3-4x your useage requirements between charges). In other words wet cells would normally stay between 50 and 80% of their charge during their life.

My understanding of gel cells is that they have the same limitations as flooded cells described above, but they accept a higher charge rate given the same size bank as flooded, reducing the time spent recharging. This is assuming your alternator has the output to keep up, which in many cases is a faulty assumption as the battery bank grows larger.

My understanding of AGM batteries is that they can accept the fast recharge rate of gels, but they also are not as sensitive to deep discharges, so there is more useful capacity in a given bank size with AGM vs. flooded or gel. My understanding of the down side is that AGM batteries are more expensive and also have a shorter life in terms of number of discharge cycles than gel.

Again this is my understanding and comments are welcome...

David Sheriff
Board Administrator
Username: David

Post Number: 144
Registered: 10-2002
Posted on Tuesday, March 02, 2004 - 01:13 pm:   Edit Post Print Post

I scanned the article and it looks fairly accurate. I fully agree with the article's recommendation for asymmetrical battery banks: a large bank dedicated to the house and a separate battery dedicated to the engine.

The only thing that jumped out at me was the stuff about battery switches. Battery switches are not required for batteries or battery banks less than 800 CCA. A single group 27 deep cycle battery is less than 800 CCA. Battery paralleling switches are a good idea, but not required.

I also do not have any problem with battery paralleling relays to charge separate battery banks. Multiple output battery chargers normally apply the same charge sequence to each battery bank regardless of their relative state of discharge. This works because batteries become increasingly reluctant to accept charge as they become more fully charged. The charging current, therefore, ends up going to the battery which needs it. Provided the charging voltages are not excessive, I have never seen "overcharging" as a significant problem.

The article discusses the characteristics of wet cells, AGM and gel-cells, but does not caution against mixing battery types in the same system. The author may have taken this point for granted as bad practice, but I see it all the time. Generally, charging systems are set up for one type of battery. Mixing battery types will shorten the life of the batteries that do not match the charging system's parameters.

The advice about securing batteries is also good practice, but the idea that your battery bank will therefore survive intact and remain useful in the event the boat turns upside down is a bit of wishful thinking. So many bad things will happen in the unlikely event the boat is inverted that I would not lay awake at night worrying that my batteries were not that tightly secured. If you are worried about overturning, make sure you have an EPIRB.

Ted Lavino
Senior Member
Username: Tlavino

Post Number: 106
Registered: 01-2004
Posted on Tuesday, March 02, 2004 - 01:41 pm:   Edit Post Print Post

I think the author was making a backhanded reference to not mixing technologies when he talks about having a separate alternator for house vs. engine. Implicit in that configuration would be the the assumption of different charging profiles for the house bank vs. engine.

How I read the author's comments re: overcharging with parallel relays has to do with the charge profile (i.e. flooded vs. gel) and the correct voltages associated with charging differing technologies.

Regarding switches, I agree that they are not required, but I personally would sleep better knowing I had the means to disconnect each battery entirely from the rest of the system.

Ted Lavino
Senior Member
Username: Tlavino

Post Number: 104
Registered: 01-2004
Posted on Monday, March 01, 2004 - 03:17 pm:   Edit Post Print Post

Greetings All,

I saw a great introduction to current battery technologies in Ocean Navigator:


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