Cruisers Forum
 


Join CruisersForum Today

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 26-11-2018, 07:43   #1
Registered User

Join Date: Dec 2014
Posts: 8
Bad battery or bad charger?

Hello electron gurus. I'd appreciate your advice on the following.

The starter batteries in my catamaran are charged from the house bank by a mastervolt Magic 12/12-20A DC-to-DC converter. I recently noticed the converter was putting 15.6 volts into the starboard starter battery for several hours, and later on I saw 16v. Since that didn't look like a healthy voltage to me, I disconnected the charger. The battery then showed 12.8 volts but it dropped overnight, with zero load on that battery, to 12.2. Now it looks stable at 12.4v after using it once to start the engine (still haven't reconnected the charger).

The battery is clearly not holding its full charge. It's a 2 year-old AGM Lifeline used exclusively to start the engine. Too young to die.

I can just go ahead and replace that battery, but my question is, should I blame the battery or the charger? Why was the charger putting 16v? (According to the specs, it shouldn't even be capable of 16v for its output). Was it because the battery was dying or was that what could have killed the battery?

Thanks much,

Juan
__________________

caleuche is offline   Reply With Quote
Old 26-11-2018, 08:16   #2
Registered User

Join Date: Jan 2017
Posts: 12,649
Re: Bad battery or bad charger?

Yes constant voltage higher than Float spec will damage a sealed batt.

Getting up way higher than the Absorb spec voltage will do so much faster and more thoroughly.

A constant DCDC converter always on is a very poor design.

A proper device would only activate when a charge source is active.

Best would be a DCDC charger that drops to Float.

But even a small VSR / ACR, or an Echo Charger would be better if you wanted to save money.
__________________

john61ct is offline   Reply With Quote
Old 27-11-2018, 08:46   #3
Registered User

Join Date: Dec 2014
Posts: 8
Re: Bad battery or bad charger?

Thanks John. Looks like I have a bad battery and a faulty charger that may have killed the battery then. Two problems for the price of one.

A couple of clarifying points:
- The charge source is always active (it's the house batteries)
- The design is good. The converter acts as a smart charger. Only that the starboard one stopped working as it should, apparently.
caleuche is offline   Reply With Quote
Old 27-11-2018, 09:15   #4
Registered User

Join Date: Jan 2017
Posts: 12,649
Re: Bad battery or bad charger?

Quote:
Originally Posted by caleuche View Post
The design is good. The converter acts as a smart charger.
Says who, just the people who installed it?

Usually the term "DC converter" does not include the regulated Absorb vs Float transition functionality essential to modern usage of the term "charger", nor the "only connected while a charge source is active" (as in engine, genset, solar etc) functionality usually required.

If current is indeed **always** flowing from House to Starter, that is not optimal,

certainly inefficient, but also potentially harmful, at least to battery longevity.
john61ct is offline   Reply With Quote
Old 27-11-2018, 10:50   #5
MJH
Registered User

Join Date: Feb 2007
Location: Gig Harbor, WA
Boat: Tayana Vancouver 42ac
Posts: 315
Re: Bad battery or bad charger?

Quote:
Originally Posted by caleuche View Post
Hello electron gurus. I'd appreciate your advice on the following.

The starter batteries in my catamaran are charged from the house bank by a mastervolt Magic 12/12-20A DC-to-DC converter. I recently noticed the converter was putting 15.6 volts into the starboard starter battery for several hours, and later on I saw 16v. Since that didn't look like a healthy voltage to me, I disconnected the charger. The battery then showed 12.8 volts but it dropped overnight, with zero load on that battery, to 12.2. Now it looks stable at 12.4v after using it once to start the engine (still haven't reconnected the charger).

The battery is clearly not holding its full charge. It's a 2 year-old AGM Lifeline used exclusively to start the engine. Too young to die.

I can just go ahead and replace that battery, but my question is, should I blame the battery or the charger? Why was the charger putting 16v? (According to the specs, it shouldn't even be capable of 16v for its output). Was it because the battery was dying or was that what could have killed the battery?

Thanks much,

Juan
I don't like the idea of the starting battery being charged "from the house battery"...the start battery "should always be charged first" or in conjunction with house battery charging (the idea being you will always be able to start your engine). The Blue Sea Systems Automatic Charging Relay does that for my boat.

~ ~ _/) ~ ~ MJH
MJH is offline   Reply With Quote
Old 27-11-2018, 12:05   #6
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 7,462
Re: Bad battery or bad charger?

Quote:
Originally Posted by MJH View Post
I don't like the idea of the starting battery being charged "from the house battery"...the start battery "should always be charged first" or in conjunction with house battery charging (the idea being you will always be able to start your engine). The Blue Sea Systems Automatic Charging Relay does that for my boat.

~ ~ _/) ~ ~ MJH


Actually the ACR charges your start battery from the house, and charges it last after the house battery voltage has been brought up to the point that the ACR is activated.
Sailmonkey is offline   Reply With Quote
Old 27-11-2018, 12:52   #7
MJH
Registered User

Join Date: Feb 2007
Location: Gig Harbor, WA
Boat: Tayana Vancouver 42ac
Posts: 315
Re: Bad battery or bad charger?

Quote:
Originally Posted by Sailmonkey View Post
Actually the ACR charges your start battery from the house, and charges it last after the house battery voltage has been brought up to the point that the ACR is activated.


Blue Sea Systems words:
Manual Battery Management and ACR SubSystem

SI-ACR automatically combines batteries during charging, isolates batteries when discharging and when starting engines. The Dual Circuit Plusô Battery Switch simplifies the switching of two batteries to OFF or ON while still providing battery isolation between the engine and auxiliary battery. The Combine function can be used to parallel the batteries in the event of a low engine battery.



~ ~ _/) ~ ~ MJH
MJH is offline   Reply With Quote
Old 27-11-2018, 13:04   #8
Zil
Registered User

Join Date: Mar 2013
Location: South Jersey
Posts: 360
Re: Bad battery or bad charger?

Was the high voltage only on one starter battery? What was the other start battery doing? Are both charged from the DC/DC ?
Zil is offline   Reply With Quote
Old 27-11-2018, 13:14   #9
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 7,462
Re: Bad battery or bad charger?

Quote:
Originally Posted by MJH View Post
Blue Sea Systems words:
Manual Battery Management and ACR SubSystem

SI-ACR automatically combines batteries during charging, isolates batteries when discharging and when starting engines. The Dual Circuit Plus Battery Switch simplifies the switching of two batteries to OFF or ON while still providing battery isolation between the engine and auxiliary battery. The Combine function can be used to parallel the batteries in the event of a low engine battery.



~ ~ _/) ~ ~ MJH


If thatís how your ACR is wired, great. Ours is plumbed to charge the house first and then the start. More charging is required to the house batteries than the start could ever need.
Sailmonkey is offline   Reply With Quote
Old 27-11-2018, 14:59   #10
Registered User

Join Date: Dec 2012
Location: Mannum, Australia
Boat: Houseboat, 60ft.
Posts: 198
Re: Bad battery or bad charger?

AGM for engine starting? Not sure if that's the best way to go?
BruceS is offline   Reply With Quote
Old 27-11-2018, 17:26   #11
Registered User

Join Date: Feb 2011
Location: South-East Australia coast
Boat: 40ft fibreglass sloop
Posts: 189
Re: Bad battery or bad charger?

This Mastervolt Magic seems a versatile bit of kit. Can do a few things, one of which is a 3-stage DC-to-DC charger (see diagram below).

Seems like it should ABSORB around 14.2v and FLOAT around 13.2v.

To check whether the charger is at fault, I would try it on another known good, fully charged battery (any size) and check the Float voltage applied to said battery - if 13.2v that would be a good sign for the Mastervolt.
After that, I would explore the Absorption and Bulk charge behaviour as well. If the Mastervolt behaves, then maybe the AGM batt failed prematurely (not unheard of) though Lifeline's are good stuff so maybe it can be reconditioned via a few cycles.
Attached Thumbnails
Click image for larger version

Name:	mastervolt.jpg
Views:	67
Size:	71.0 KB
ID:	181365  
Marqus is offline   Reply With Quote
Old 27-11-2018, 18:34   #12
Registered User

Join Date: Jan 2017
Posts: 12,649
Re: Bad battery or bad charger?

Quote:
Originally Posted by MJH View Post
I don't like the idea of the starting battery being charged "from the house battery"...the start battery "should always be charged first" or in conjunction with house battery charging (the idea being you will always be able to start your engine).
absolutely not

Starters don't get discharged more than .003%

Best practice is all significant sources go direct to House that needs it, then only a little ampacity cheaper device is needed to keep it topped up.
john61ct is offline   Reply With Quote
Old 27-11-2018, 18:35   #13
Registered User

Join Date: Jan 2017
Posts: 12,649
Re: Bad battery or bad charger?

Quote:
Originally Posted by BruceS View Post
AGM for engine starting? Not sure if that's the best way to go?
fine, can in fact be better, but NP either way
john61ct is offline   Reply With Quote
Old 27-11-2018, 18:38   #14
Registered User

Join Date: Jan 2017
Posts: 12,649
Re: Bad battery or bad charger?

so yes, that line is a DC-DC 3-stage battery charger, happens to be settable to dumb down as a DC-DC converter as well.

triple the price needed, you'd think they'd last
john61ct is offline   Reply With Quote
Old 27-11-2018, 19:33   #15
Registered User

Join Date: Feb 2011
Location: South-East Australia coast
Boat: 40ft fibreglass sloop
Posts: 189
Re: Bad battery or bad charger?

Given the OP's info so far, to me it's a bit early to condemn the Mastervolt charger.

If the battery was in some way deficient, could the charger not have (by design) pushed up to 16v in BULK mode?
__________________

Marqus is offline   Reply With Quote
Reply

Tags
battery, charger

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
AC battery charger for AGM start battery and Lithium bank exMaggieDrum Electrical: Batteries, Generators & Solar 75 19-06-2018 15:35
Battery-to-battery charger (independant of source charge voltage) ayates Electrical: Batteries, Generators & Solar 38 18-03-2018 06:48
Wiring My Battery Charger to the Battery Switch ? Shoalcove Electrical: Batteries, Generators & Solar 10 23-08-2010 17:24
Opinions on this charger: BASSMASTER ProMariner Marine Battery Charger exranger Electrical: Batteries, Generators & Solar 6 30-11-2008 08:25
Battery charger to replace battery? lilly Electrical: Batteries, Generators & Solar 5 22-07-2006 19:11

Advertise Here


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:23.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×

ShowCase vBulletin Plugins by Drive Thru Online, Inc.