Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 18-04-2021, 13:18   #1
Registered User

Join Date: Sep 2020
Location: Mount Vernon, WA
Boat: Alajuela Crealock 37
Posts: 78
Parallel Why NOT?

Older simple boat with two “dual-purpose” batteries.
Is there ANY reason that a simple boat owner with only two combo batteries WOULDNT want to go to parellel hook up?
A broader question:
Is there ever a reason why someone would not want to hook there batteries in parallel?

AmzngGrace is offline   Reply With Quote
Old 18-04-2021, 13:36   #2
Moderator
 
JPA Cate's Avatar

Join Date: Nov 2011
Location: aboard, cruising in Australia
Boat: Sayer 46' Solent rig sloop
Posts: 21,230
Re: Parallel Why NOT?

When/if you flatten those parallel batteries, how do you start the engine? We have, for many years, kept a separate start battery, and also have it rigged so the engine may be started from below on a separate switch.

Ann
__________________
Who scorns the calm has forgotten the storm.
JPA Cate is offline   Reply With Quote
Old 18-04-2021, 13:39   #3
Registered User

Join Date: Nov 2013
Location: Nice, France
Boat: Hunter Marine 38
Posts: 1,092
Re: Parallel Why NOT?

"Is there ever a reason why someone would not want to hook there batteries in parallel?"
Reasons: batteries of dissimilar chemistry, dissimilar capacity, dissimilar age, .....
There must be more of course.
sailormed is offline   Reply With Quote
Old 18-04-2021, 13:41   #4
Registered User

Join Date: Sep 2020
Location: Mount Vernon, WA
Boat: Alajuela Crealock 37
Posts: 78
Re: Parallel Why NOT?

Is there any reason other than using up both batteries and not able to start to preclude hooking two batteries together in parallel THAT ARE EXACTLY THE SAME AGE, CAPACITY AND CHEMISTRY?

Why I am asking...
I am thinking about my weak links, (many). I want to hook up a 1000-1500 w (cayman vs tigris) windlass to my boat that has 2 100aH batteries. I am moving mentally from the tigris 1500w to cayman 1000w to make it easier for my system to run (55a alternator) while engine running. Can I, and does it make sense to wire (optionally when using windlass) both batteries in parallel? I would separate them afterwards to minimize impact on ability to start boat the next morning after using my house battery for lights and various other circuits...
AmzngGrace is offline   Reply With Quote
Old 18-04-2021, 13:57   #5
Registered User

Join Date: Aug 2011
Location: Hampton Roads, VA
Boat: Bristol 27 #335
Posts: 7,356
Re: Parallel Why NOT?

Mine have always been in parallel since 2011

After I removed the diesel from my boat, I put the starter battery in parallel with a so called deep cycle battery and they lasted about 4 years.

Now I have two of the so called deep cycle batteries in parallel and they run everything on my boat and are charged via solar (115 watts to 155 watts) They run the inverter, computers, autopilot, lights, GPS, depth, phone charging, HDTV, etc

I have a pull start outboard so no starting battery needed.

These batteries are 90 ah each.

When they wear out, I may go with a couple 200 ah or better 6 volt batteries in series but have a charged 12 volt for backup and this will be about the time I retire and start cruising long distance
thomm225 is offline   Reply With Quote
Old 18-04-2021, 14:28   #6
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 15,052
Images: 14
Re: Parallel Why NOT?

A popular mod for older boats with a basic electrics fit is to parallel them and then add a third engine start battery. That doubles the house bank capacity instantly for all the electronics you need I did ours when we first got her in 2007.

So two batteries and the engine running, that should power a 1kw windlass. You might put a el cheapo battery monitor in the house bank circuit to monitor what's going on and ensure the batteries are fully charged afterwards/

https://www.amazon.co.uk/Battery-Mon...8781207&sr=8-5
Pete7 is online now   Reply With Quote
Old 18-04-2021, 14:56   #7
Registered User

Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft Catalina 381
Posts: 2,026
Re: Parallel Why NOT?

Personally, I'm of the opinion that engine starting power is safety critical. Any boat with one or more engines or generators should always have at least one battery dedicated to starting. It only starts engines and gets recharged and never powers anything else.
rslifkin is offline   Reply With Quote
Old 18-04-2021, 15:09   #8
Registered User

Join Date: May 2011
Location: Lake Ont
Posts: 7,192
Re: Parallel Why NOT?

Quote:
Originally Posted by AmzngGrace View Post
Is there ANY reason that a simple boat owner with only two combo batteries WOULDNT want to go to parellel hook up?
A broader question:
Is there ever a reason why someone would not want to hook there batteries in parallel?

Paralleling batteries is only actually necessary when you are occasionally pulling more current than one battery can comfortably deliver. Otherwise, you will still have the same overall Ah capacity whether you run the batteries in parallel, or run from one and then the other.

Downsides of a fixed parallel battery arrangement:
  • batteries need to be of the same type, size, age, condition
  • a failing battery -eg shorted cell - pulls the entire bank down, and neither battery can be fully charged
  • if the bank is discharged, you are now out of DC power
For the price of a 1-2-both-off switch, you can have the batteries isolated, and you can parallel them if desired.

But my preferred arrangement is Pete7's suggestion - a house bank and a dedicated start battery.
Lake-Effect is offline   Reply With Quote
Old 18-04-2021, 15:24   #9
Registered User

Join Date: Sep 2020
Location: Mount Vernon, WA
Boat: Alajuela Crealock 37
Posts: 78
Re: Parallel Why NOT?

So 1-2-both-off switch automatically gives me twice the current?

FYI left as shown is to starter, right is from battery 1, center is battery 2.
Attached Thumbnails
Click image for larger version

Name:	375A9E91-CEC3-4235-A669-996D5C60E5E8.jpeg
Views:	20
Size:	108.8 KB
ID:	236805  
AmzngGrace is offline   Reply With Quote
Old 18-04-2021, 15:55   #10
Registered User

Join Date: May 2011
Location: Lake Ont
Posts: 7,192
Re: Parallel Why NOT?

Quote:
Originally Posted by AmzngGrace View Post
So [batteries in parallel] gives me twice the current?
In theory, if you have two identical batteries, each capable of delivering X amps, then the two in parallel could deliver 2 times X amps.

The question is, of course, are you ever demanding 2 times X amps from your batteries? Have you ever measured your highest current draw? If you never need more current than one battery can deliver, there's really no point to leaving your batteries connected in parallel.
Lake-Effect is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
LiFePo4 -- Parallel or Not? Dockhead Lithium Power Systems 88 26-12-2020 23:32
Why not Croatia? Why Croatia? jgw50 Europe & Mediterranean 50 14-08-2019 21:19
Micah's Folly...why not, and why anyway... micah719 Monohull Sailboats 10 17-07-2014 13:15
Four Solar Panels - Parallel , Series or Series-Parallel west coaster Electrical: Batteries, Generators & Solar 76 07-07-2011 14:35

Advertise Here


All times are GMT -7. The time now is 10:21.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.