agm charging - SailNet Community
 2Likes
  • 2 Post By RegisteredUser
 
LinkBack Thread Tools
post #1 of 10 Old 3 Weeks Ago Thread Starter
dadio917
 
dadio917's Avatar
 
Join Date: Apr 2011
Location: Lake Tahoe....boat is in SF Bay
Posts: 269
Thanks: 0
Thanked 7 Times in 7 Posts
Rep Power: 9
 
agm charging

hi - we've got ~520AH of lifeline group 30 batteries and three charging mechanisms...heart interface shore power, 120A alternator with next step regulator, and solar with victron charge controller. Also have a link 10 battery monitor which supplies endless hours of entertainment.

am finally doing some extended cruising so seeing it all operate in detail.

my post concerns the AH reading from the link 10 monitor which should indicate a state of charge. I last calibrated when installing the solar and at the time was just using solar. theoretically it should read 0 at full charge. So here's the anomaly I've noticed that I'm wondering if I should worry about:
if on solar long enough it gets to about 0.
if charged with engine it gets to about -30AH
if charged on shore power gets to about +30

I'm sure this is because the bulk/absorption/float settings are not identical on the three charging systems. what I'm wondering is if I should worry about it? Are the batteries being over or under charged with that 60A swing?

voltages have looked fine to my eye. Never discharged below about 12.3V after a heavy night of sailing with all nav gear, lights, auto helm, and fridge.

Dadio917
Valiant 39
dadio917 is offline  
Sponsored Links
Advertisement
 
post #2 of 10 Old 3 Weeks Ago
Senior Member
 
chef2sail's Avatar
 
Join Date: Nov 2007
Location: Maryland
Posts: 9,898
Thanks: 76
Thanked 175 Times in 167 Posts
Rep Power: 12
 
Send a message via AIM to chef2sail
Re: agm charging

Correct me I may be wrong but a battery reading of 12.3 means itís discharged 50%. With a battery bank of 520 ah....260 usable you have used what 130 ah or 260 ah. Both seem a lot to use in your boat size for one day. Our boat 720ah averages 60-75 ah per day diet.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
___________________________
S/V Haleakala (Hawaiian for" House of the Sun")
C&C 35 MKIII Hull # 76
Parkville, Maryland
(photos by Joe McCary)
Charter member of the Chesapeake Lion posse

Our blog-
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


ďSailing is just the bottom line, like adding up the score in bridge. My real interest is in the tremendous game of life.Ē- Dennis Conner
chef2sail is online now  
post #3 of 10 Old 3 Weeks Ago
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 19,324
Thanks: 82
Thanked 544 Times in 521 Posts
Rep Power: 11
   
Re: agm charging

Amp hour counters are notoriously inaccurate tools for measuring state of charge. 30 amps out of 500 may be as close as it can get. The rate at which amps go out and in matter, not just the quantity. Iím pretty sure there is also an inefficiency in replacing amps that have been drawn down. Batteries also degrade over time, so wonít always accept there original capacity. Loved your line..... endless hours of entertainment. Been there done that. Doing it now.

My guess is your alternator isnít following the same Bulk-Absorb-Float profile as your shore charger.

The best way to know you are actually at or very near a Full is to monitor the amps of charge that your battery is accepting, during the Absorb stage. Not count total amps in/out. This is different from what the charger is putting out, which is also supplying power to whatever devices are drawing power at the same time. All battery types can be a bit different, but I understand a good rule of thumb for Full is when the bank is accepting charge amps, in Absorb, that are approx 0.5% of bank capacity. ie 1amp for every 200hrs of bank size.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
 
post #4 of 10 Old 3 Weeks Ago
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Northport, NY
Posts: 3,080
Thanks: 2
Thanked 83 Times in 83 Posts
Rep Power: 0
 
Re: agm charging

Quote:
Originally Posted by Minnewaska View Post
The best way to know you are actually at or very near a Full is to monitor the amps of charge that your battery is accepting, during the Absorb stage. Not count total amps in/out. This is different from what the charger is putting out, which is also supplying power to whatever devices are drawing power at the same time. All battery types can be a bit different, but I understand a good rule of thumb for Full is when the bank is accepting charge amps, in Absorb, that are approx 0.5% of bank capacity. ie 1amp for every 200hrs of bank size.
Are you stating that the the AMP reading when the engine is running is based on how many amps the batteries can take?

How does the regulator figure that out?

I don't understand this too well.... but I figured the only thing that can actually be measured is the voltage. You can measure the amps in a battery if I am correct. You can measure the current in a wire.

My crude understanding is that the smart regulator measure the system (battery?) voltage. If it's low according to a charging profile... the smart regulator energized the field to kick out more amps... and the voltage is raised when doing this. The charging profile is an algorithm.... I think. You have to set this for the battery capacity... because the smart regulator isn't smart enough to figure that out.

The best way to manage you batts is to carefully observe their voltage (resting).. any loads or alt inputs will fool you and the smart regulator and monitors. Keep in mind that the more frequently you discharge your batteries... the shorter they will last. This means be conservative in the use of electricity on board.

pay attention... someone's life depends on it
SanderO is online now  
post #5 of 10 Old 3 Weeks Ago
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 19,324
Thanks: 82
Thanked 544 Times in 521 Posts
Rep Power: 11
   
Re: agm charging

Quote:
Originally Posted by SanderO View Post
Are you stating that the the AMP reading when the engine is running is based on how many amps the batteries can take?

How does the regulator figure that out?.......
The regulator canít figure it out and Iím not sure which amp reading youíre referring to. A charge controller builds to a defined voltage in Bulk, then holds that voltage until the bank can no longer accept a defined amount of amps. You need a shunt at the house bank that can tell how many amps are actually being accepted as charge into the bank, regardless of what the charge source can produce. The charge source output is somewhat irrelevant, as it has to put charge into the bank, plus provide current to whatever appliances are running at the same time. Iím sure there is waste in top of that.

Iím no pro, so there is probably a better way to describe this.

Resting voltage can be a reasonable way to know you donít discharge too far, but itís hard to know youíve fully charged. Of course, no boat that has anything turned on is ever resting.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
post #6 of 10 Old 3 Weeks Ago
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Northport, NY
Posts: 3,080
Thanks: 2
Thanked 83 Times in 83 Posts
Rep Power: 0
 
Re: agm charging

Quote:
Originally Posted by Minnewaska View Post
The regulator canít figure it out and Iím not sure which amp reading youíre referring to. A charge controller builds to a defined voltage in Bulk, then holds that voltage until the bank can no longer accept a defined amount of amps. You need a shunt at the house bank that can tell how many amps are actually being accepted as charge into the bank, regardless of what the charge source can produce. The charge source output is somewhat irrelevant, as it has to put charge into the bank, plus provide current to whatever appliances are running at the same time. Iím sure there is waste in top of that.

Iím no pro, so there is probably a better way to describe this.

Resting voltage can be a reasonable way to know you donít discharge too far, but itís hard to know youíve fully charged. Of course, no boat that has anything turned on is ever resting.
I think this whole charging thing has been probably way over thought as it applies to most people with auxilliary diesels on sailboats.

These boats have an increasing appetite for electricity over the years and require more and more power for these devices.

I've observed the development/process over 35 years I have owned a sailboat. Yes I added more and more things which needed power... then added a larger batteries to feed them.. and a higher output alternator to top off the batteries faster... and then some solar to replenish the batts when the engine was not on and the sun was shining and I was away. The along came these very accurate measuring devices and monitors and smart regulators which had profiles which take into account the performance characteristics of various batteries. These measuring devices required a shunt.

"An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case, a separate shunt, a resistor of very low but accurately known resistance, is placed in parallel with a voltmeter, so that all of the current to be measured will flow through the shunt. The resistance is chosen so that the resultant voltage drop is measurable, but low enough not to disrupt the circuit. The voltage across the shunt is proportional to the current flowing through it, and so the measured voltage can be scaled to directly display the current value"

Amps in the circuit are derived from precision voltage measurements. So now you can tell how many amps you're adding from charging devices... or using by load devices.

People who are big time electricity users need to do something. Bigger and bigger batts often can work. So more charging is chosen... generators, high output alts... fields of solar panels... co generation from spinning props and so on.... and of course we now have high efficient LED lighting and low consumption electronics.

If you have a smallish boat you need to design a system and your USE of electricity which FITS your boat... this includes the load side and the charging side.

My hunch is that your boat's architecture will be a voice in what works. But everyone seems to be addicted to electrons and what they can do.... and that work comes at a cost.

I have 2 8D - AGMs and a Optima blue top for engine starting. I have a high output alt with a smart regulator a couple of yr old 55 watt solar panels. I don't use an entertainment system... nor a 12v frig. My AP is very low draw. All lighting is LED... and I pretty much have no problem with having enough power... or recharging the house bank. My alt is running a few hrs per day when I am on board and I am never using shore power as I am on a mooring or anchor.

Best advice is to keep it simple and sail more.

pay attention... someone's life depends on it
SanderO is online now  
post #7 of 10 Old 3 Weeks Ago Thread Starter
dadio917
 
dadio917's Avatar
 
Join Date: Apr 2011
Location: Lake Tahoe....boat is in SF Bay
Posts: 269
Thanks: 0
Thanked 7 Times in 7 Posts
Rep Power: 9
 
Re: agm charging

Last night, anchored here in Hawaii where our fridge/freezer is running pretty heavy, we used about 65-75A. That included an hour or so of lighting up the nav gear when a squall came by and our anchor alarm went off (had it programmed a bit tight). So, about 70a and voltage reads 12.65, which if I remember is pretty full.

The 12.35 we got down to was on a passage, not sure how many hours. It was pretty rough and were running the electric pilot, and cloudy so not many electrons from the sun. So I should not have thrown the 12.3 number out. Normally in the morning before solar kicks in weíre still 12.6-12.65.

My original question stands: how worried should I be that the three different charging systems would be out of sync?

Dadio917
Valiant 39
dadio917 is offline  
post #8 of 10 Old 3 Weeks Ago
Senior Member
 
Join Date: Jan 2017
Posts: 1,075
Thanks: 109
Thanked 40 Times in 40 Posts
Rep Power: 3
 
Re: agm charging

You cannot count on a Ah counter to be very accurate at the best of times, you know Maine Sail's marinehowto.com articles right?

Each charge source should be adjusted so they each have the same CV / Absorb setpoint, and its transition from Holding Absorb voltage to Float (stop-charge point) is calibrated to **not** happen **until** amps tapers to your selected endAmps, ideally as specified by the batt maker's datasheet. Or use .005C as a default, or maybe .01C with AGM.

Very few charge sources can do so directly, so shoot for "at least a few times a week" for longevity, lengthening Hold Absorb time until it does during those operating conditions.

And when you verify that has been done - the taper current or lower indeed got hit before dropping to Float, then you reset your BM tell it you just hit 100%

and it will be a lot more accurate than if you haven't been doing that, at least every few cycles.
john61ct is online now  
post #9 of 10 Old 3 Weeks Ago
Senior Member
 
Join Date: Aug 2010
Location: The Bahamas
Posts: 3,307
Thanks: 3
Thanked 124 Times in 122 Posts
Rep Power: 9
 
Re: agm charging

My feeling is that some of these gadgets can make you crazy...and never deliver what you desire. They will improve..over time..and maybe become valuable.

Id check batts with voltage meter at certain times of the day and get a record of info.
Certainly the diff between good sun and cloudy is huge. Wanna learn how long you can stretch it when cloudy.
You may have the right balance
SanderO and mbianka like this.
RegisteredUser is online now  
post #10 of 10 Old 3 Weeks Ago
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Northport, NY
Posts: 3,080
Thanks: 2
Thanked 83 Times in 83 Posts
Rep Power: 0
 
Re: agm charging

Quote:
Originally Posted by RegisteredUser View Post
My feeling is that some of these gadgets can make you crazy...and never deliver what you desire. They will improve..over time..and maybe become valuable.

Id check batts with voltage meter at certain times of the day and get a record of info.
Certainly the diff between good sun and cloudy is huge. Wanna learn how long you can stretch it when cloudy.
You may have the right balance
I installed a link 20... with the ability to show SOC and AH used and so on... Most of that is inaccurate and a waste of time. What I do find valuable is that is a very precise voltmeter and does show amps going in or amps going out. I can easily see the value of amp load of whatever is turn on/functioning and I can see the amps the charging sources are providing at any time. The AH counter and so on goes out of sync all the time so I simply ignore it. When system voltage is reading low charging is called for. The display can cycle or remain on one type of data. I leave it on volts. It monitors 2 banks... in my case... house and start.

pay attention... someone's life depends on it
SanderO is online now  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome