Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 07-05-2016, 18:55   #1
Registered User
 
hd002e's Avatar

Join Date: Dec 2011
Location: New Haven, Connecticut, USA
Boat: Beneteau First 305
Posts: 76
Deep cycle and dual purpose in same bank

Battery question: i have combined marine dual purpose and marine deep cycle batteries (both are traditional, not AGM or lithium) in the same bank without an isolater in between. Will it be OK or will I see a discharge between the two?


Sent from my iPhone using Cruisers Sailing Forum
__________________

__________________
hd002e is offline   Reply With Quote
Old 07-05-2016, 19:25   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by hd002e View Post
Battery question: i have combined marine dual purpose and marine deep cycle batteries (both are traditional, not AGM or lithium) in the same bank without an isolater in between. Will it be OK or will I see a discharge between the two?


Sent from my iPhone using Cruisers Sailing Forum
I have a feeling that you already know or suspect the answer.

What will happen depends on a host of factors, inter alia:

  • age, chemistry, and condition of batteries
  • how they've been used in the past (rate and depth of discharge, charging voltages, temperatures, how often they've been 100% recharged, equalization cycles performed, etc., etc.)
  • how they'll be used in the future (rate and depth of discharge, charging voltages, temperatures, how often they'll been 100% recharged, equalization cycles performed, etc., etc.)
  • scheme of paralleling, and size & condition of cables and lugs
  • how you use your boat and what level of original capacity do you consider "good" or "need replacement"
Bottom line: You've already combined them. Monitor them as you go along. You may get the service life and quality you expect. If not, replace battery bank with new batteries of the identical size and type.


Bill
__________________

__________________
btrayfors is offline   Reply With Quote
Old 07-05-2016, 19:28   #3
Registered User
 
hd002e's Avatar

Join Date: Dec 2011
Location: New Haven, Connecticut, USA
Boat: Beneteau First 305
Posts: 76
Re: Deep cycle and dual purpose in same bank

Hey btrayfors,

Very valid points. I have brand new batteries though, just started combining them today and haven't put any load on it yet.


Sent from my iPhone using Cruisers Sailing Forum
__________________
hd002e is offline   Reply With Quote
Old 07-05-2016, 19:31   #4
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by hd002e View Post
Hey btrayfors,

Very valid points. I have brand new batteries though, just started combining them today and haven't put any load on it yet.


Sent from my iPhone using Cruisers Sailing Forum
OK, if they're brand new then buy additional marine deep cycle battery or batteries of the identical type to add to the house bank, and use the "dual-purpose" battery for starting or reserve or something else.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 07-05-2016, 19:32   #5
Registered User

Join Date: Aug 2015
Location: SW Florida
Boat: Grand Banks 49
Posts: 449
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by hd002e View Post
Battery question: i have combined marine dual purpose and marine deep cycle batteries (both are traditional, not AGM or lithium) in the same bank without an isolater in between. Will it be OK or will I see a discharge between the two?
===

In my experience so called dual purpose batteries are a compromise that don't do either one very well. You will end up deep cycling your engine starting batteries which will noticeably shorten their life and possibly leave you in an awkward situation someday. My recommendation would be to use AGM batteries for engine starting, conventional deep cycle batteries for your house bank, and some sort of switch, either manual or voltage sensing to combine them for charging only.
__________________
wayne.b is offline   Reply With Quote
Old 08-05-2016, 01:13   #6
Registered User
 
nigelmercier's Avatar

Join Date: Jul 2011
Boat: Bavaria 47
Posts: 172
Re: Deep cycle and dual purpose in same bank

I wouldn't even mix different brands, let alone types.
__________________
Nigel
Got a Bavaria? Want a Bavaria Forum? Click here!
nigelmercier is offline   Reply With Quote
Old 08-05-2016, 05:13   #7
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Deep cycle and dual purpose in same bank

Our cat came with 4 exide duel 160Ah lead acid batteries. We couldn't source the same batteries so added 2 similar standard 160Ah lead acid batteries. So far so good after a couple of years constant use. My basic understanding is the dual just have thicker plates. The exide also have quite high charge point recommendations and different SOC % to most batteries I've used before. They are all used for the house bank, wired together without isolation.
__________________
monte is offline   Reply With Quote
Old 08-05-2016, 06:33   #8
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 12,373
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by wayne.b View Post
===

In my experience so called dual purpose batteries are a compromise that don't do either one very well. You will end up deep cycling your engine starting batteries which will noticeably shorten their life and possibly leave you in an awkward situation someday. My recommendation would be to use AGM batteries for engine starting, conventional deep cycle batteries for your house bank, and some sort of switch, either manual or voltage sensing to combine them for charging only.
Curious to know why you recommend AGMs for starting batteries? My understanding is the main advantages for AGMs are the ability to take higher charge rates and ability to mount the batteries other than flat and level. What's the advantage for starting?
__________________
The water is always bluer on the other side of the ocean.
skipmac is offline   Reply With Quote
Old 08-05-2016, 07:07   #9
Registered User

Join Date: Aug 2015
Location: SW Florida
Boat: Grand Banks 49
Posts: 449
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by skipmac View Post
Curious to know why you recommend AGMs for starting batteries? My understanding is the main advantages for AGMs are the ability to take higher charge rates and ability to mount the batteries other than flat and level. What's the advantage for starting?
===

AGMs have higher cranking power than an equivalent sized flooded lead acid battery. Just as they have a higher charge acceptance rate, they can also supply more amps for short periods of time when discharging. You can see it in the numbers when you look at CCA ratings (Cold Cranking Amps). That may not be a benefit for small easily cranked engines but in my case I'm starting large diesels and the difference is very noticeable.
__________________
wayne.b is offline   Reply With Quote
Old 08-05-2016, 08:35   #10
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,725
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by hd002e View Post
Battery question: i have combined marine dual purpose and marine deep cycle batteries (both are traditional, not AGM or lithium) in the same bank without an isolater in between. Will it be OK or will I see a discharge between the two?
If they are all 12 volt batteries none are true deep cycle anyway. I don't think it is much of an issue.

Now if some are 6 volt deep cycle I would separate them.
__________________
mitiempo is offline   Reply With Quote
Old 08-05-2016, 09:37   #11
Registered User
 
Terra Nova's Avatar

Join Date: Apr 2007
Location: Marina del Rey, California
Boat: Freya 39 cutter- Terra Nova
Posts: 3,645
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by hd002e View Post
...i have combined marine dual purpose and marine deep cycle batteries (both are traditional, not AGM or lithium) in the same bank...
Very foolish move.
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
Terra Nova is offline   Reply With Quote
Old 08-05-2016, 09:52   #12
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,574
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by btrayfors View Post
OK, if they're brand new then buy additional marine deep cycle battery or batteries of the identical type to add to the house bank, and use the "dual-purpose" battery for starting or reserve or something else.

Bill
This. My favoured combo is traditional flooded 6VDC in series-parallel, with all charging sources going to that house bank. The house bank in turn supplies via echo chargers or ACRs the 12 VDC start battery and the 12 VDC windlass battery at float voltages to basically ensure that you've got them pretty close to topped-up all the time.

As a belts-and-suspenders approach, you can provide switching to take the house bank out of the circuit and use the start as a house bank in emergencies or for maintenance. You may have to change your MPPT or other charge controller settings, but it's supposed to be a Plan B if something takes down your house bank.

This is all predicated on the house bank being comprised of identical individiual batteries that are never, or close to never, treated as other than one big battery. Mix and match brings the whole bank down to its weakest component.
__________________
Can't sleep? Read www.alchemy2009.blogspot.com for fast relief. Can't read? Avoid www.volumesofsalt.blogspot.com, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote
Old 08-05-2016, 11:23   #13
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 12,373
Re: Deep cycle and dual purpose in same bank

Quote:
Originally Posted by wayne.b View Post
===

AGMs have higher cranking power than an equivalent sized flooded lead acid battery. Just as they have a higher charge acceptance rate, they can also supply more amps for short periods of time when discharging. You can see it in the numbers when you look at CCA ratings (Cold Cranking Amps). That may not be a benefit for small easily cranked engines but in my case I'm starting large diesels and the difference is very noticeable.
That makes sense. Amps that go in fast will also come out fast.
__________________
The water is always bluer on the other side of the ocean.
skipmac is offline   Reply With Quote
Old 08-05-2016, 11:54   #14
Registered User
 
Dougtiff's Avatar

Join Date: Jul 2015
Location: San Rafael, Ca.
Boat: Gaff rigged Ketch[Spray]37' on deck
Posts: 179
Re: Deep cycle and dual purpose in same bank

Your charging system should go to your STARTING batt. first then combine to the HOUSE bank [Nigel Calder].Use your DUAL purpose batt. for STARTING and the others for HOUSE bank, that way you can have different batts. this way the START is allways charged and also wire in a ON/OFF switch between the start and house bank, thatway you can combine if needed.
__________________
Dougtiff is offline   Reply With Quote
Old 08-05-2016, 12:32   #15
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,029
Re: Deep cycle and dual purpose in same bank

In theory a "dual purpose" battery has a medium-thickness plate, as opposed to the thicker plate of a true deep cycle, or the thinner plate of an SLI. The thicker plate should allow for a deeper charge cycle (which moves more metal off the plate) while maintaining the integrity of the plate. So when combined with a "dual purpose", you literally are physically putting great wear, proportionately, on the dual purpose battery and that "should" result in shortening its life faster than the deep cycle battery.
Result? Two uneven batteries and that should help to wear them both out too early.


At least, that's my understanding of it.


If they are both new...why get and mix two different battery types?? Last two left on the shelf?
__________________

__________________
hellosailor is offline   Reply With Quote
Reply

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
[SOLD] 5 of Deep Cycle Dc-Gel Group 31 Batteries - NEW and for sale challis0124 Classifieds Archive 1 20-10-2015 08:40
Same old, same old in the polar regions knottybuoyz Polar Regions 4 07-03-2008 18:44



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:08.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.