Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 01-09-2011, 18:03   #1
Registered User

Join Date: Mar 2011
Posts: 253
Simple Battery Question


I'm looking for a bit of advice on my battery set up. I have a Bristol 35 with 2 dual purpose marine batteries with a simple 1, 2, and both switch. I have been starting on both, running the engine on both to charge both and then while under sail or over night switching to one of the batteries to save one for starting.

One of my batteries seems to not be holding a charge as well and I will replace. Should I stick with 2 deep cycles or go for one starting and one deep cycle?

Am I managing these batteries correctly and if I switched to one starting, how should I change what I'm doing?


shamrock is offline   Reply With Quote
Old 01-09-2011, 18:13   #2
Registered User

Join Date: Dec 2008
Location: ontario canada
Boat: grampian 26
Posts: 1,743
Re: Simple Battery Question

Never use your start battery as a house battery.

perchance is offline   Reply With Quote
Old 01-09-2011, 18:38   #3
Registered User
Strygaldwir's Avatar

Join Date: Dec 2004
Location: Deale, Maryland
Boat: SeaView - Privilege 37
Posts: 1,019
Images: 5
Re: Simple Battery Question

I'd agree with the sentiment to not use the starter battery for long discharge. It will not hold up as well.

You don't have to use both batteries to start, in most instances. I'd tend to leave the starter battery for starting and the deep cycle battery for house usage.

So, I'd recommend one starter battery, one Deep Cycle battery. Even though they can be used for either roles, they are optimized for the specific role and will give better performance and life if used coorespondingly.
Strygaldwir is offline   Reply With Quote
Old 01-09-2011, 18:43   #4
CF Adviser
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,256
Re: Simple Battery Question

With your kind of setup, I prefer to go with two identical batteries. However, the downside is that you never want to mix an old battery with a new one in this type of system. Therefore, I recommend you replace both batteries with new deep cycles.

This system is simplicity at its finest. You just need to remember to keep working the switch.
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 01-09-2011, 18:46   #5
cat herder, extreme blacksheep
zeehag's Avatar

Cruisers Forum Supporter

Join Date: Jul 2008
Location: furycame alley , tropics, mexico for now
Boat: 1976 FORMOSA yankee clipper 41
Posts: 16,500
Images: 56
Send a message via Yahoo to zeehag Send a message via Skype™ to zeehag
Re: Simple Battery Question

my boat uses a single 8d battery for starting. is also usable for house. my house are 4 golfcart batteries, 6v. both banks are deep cycle.
if you are on anchor, do not use your starting battery for house. if you use deep cycle batteries for each, is not a problem i have ever seen.
at anchor you can run out of juice. is harder to do that on a dock.
zeehag is offline   Reply With Quote
Old 01-09-2011, 19:18   #6
Moderator Emeritus
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 9,844
Re: Simple Battery Question

In the future you might consider purchasing a battery combiner. This way you do not have to remember to disconnect or reconnect the start battery. You can also use the start battery as a house battery. The combiner will disconnect the house load on it before it gets too low to start the engine and reconnect it when the DC system voltage is high enough to charge it.

You would want two deep cycles. I agree with Bash on getting two deep cycles now.

Life begins where land ends.
David M is offline   Reply With Quote
Old 01-09-2011, 19:54   #7
Registered User
Ziggy's Avatar

Join Date: Apr 2008
Location: U.S., Northeast
Boat: Contessa 32
Posts: 1,353
Images: 2
Re: Simple Battery Question

1) Two deep cycle batteries are better than one starting + one deep cycle

2) Blue Sea Systems makes a nifty kit that includes a battery switch and a charging relay: Add a Battery - Blue Sea Systems .
The future ain't what it used to be.
-- Yogi Berra, 1925-2015
Ziggy is offline   Reply With Quote
Old 01-09-2011, 20:32   #8
Senior Cruiser
roverhi's Avatar

Cruisers Forum Supporter

Join Date: Aug 2005
Location: Kona, Hawaii
Boat: 1969 Pearson 35 #108
Posts: 5,450
Send a message via Yahoo to roverhi
Re: Simple Battery Question

When you switch to 'both' to start, you may be in for a surprize. If one of your batteries is dead, the good battery will dump it's juice into the bad battery leaving you with two dead batteries and no start. Start with the battery switch on 'one' or 'two' but not on both except as a desperation move. Switch to 'both' after the engine is running and preferably with the engine only at idle. I'm sure you have a make before break switch but it you don't, switching at idle, with no load on the alternator, should keep you from blowing the diodes.
Peter O.
'Ae'a Pearson 35
roverhi is online now   Reply With Quote
Old 01-09-2011, 22:31   #9
Registered User
Adelie's Avatar

Join Date: Feb 2010
Location: El Ciudad del Mission San Diego de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 2,364
Re: Simple Battery Question

The 'dual purpose marine' batteries you have now are not true deep cycle batteries. They are a hybrid that can be discharged somewhat more than a starting battery but less than a true deep cycle. You may have been inadvertantly abusing them by treating them like deep cycles and that is why one of them is going now. Couldn't say for sure without knowing how old they are, how much maintenance you do to them and at what frequency, their recharging protocol, how low you go before recharging and how many cycles they have been thru. Don't bother to figure all that out, not germain to what to do going foreward.

I would keep one of your existing batteries as a starter and get one or two deep cylces for house loads. The marine battery can handle a deeper than normal discharge occasionally handling house loads.

Then the question becomes how do you want to charge everything. Adding a high capacity alternator with smart regulator for the house batteries, retaining the stock alternator for the starting battery and have two independant electrical systems would be my pick. It's simple, it charges somewhat faster and has redundancy. But it also presuposes that you have room for the extra alternator and the bucks for everything.

Various combining and isolating electronics would be my second choice if there was a constraint on the system previously described, but I haven't really ever researched those alternatives.
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
Adelie is online now   Reply With Quote
Old 02-09-2011, 18:49   #10
Registered User

Join Date: Mar 2011
Posts: 253
Thanks everyone for the comments!

shamrock is offline   Reply With Quote


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Xantrex Link Pro Sailagain Electrical: Batteries, Generators & Solar 52 19-11-2011 17:54
Battery Testing Methods Dockhead Electrical: Batteries, Generators & Solar 12 28-08-2011 08:08
Start Battery Issues barbara ann Electrical: Batteries, Generators & Solar 1 10-08-2011 10:59
Yet Another Battery Choice Question . HarveyN Electrical: Batteries, Generators & Solar 2 04-08-2011 05:12
Battery, alternator, shut question phantomracer Electrical: Batteries, Generators & Solar 9 26-06-2011 18:38

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:06.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.