The 6 golf cart bank on our boat shows 12.4 volts on the Link and on a good meter after a couple of hours "at rest". It's a bear to access, so before I start removing the interconnect cables to isolate each battery, I'm wondering if a bad cell is the most likely cause??
Battery bank @ 12.4 volts?
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ksanders
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What do you mean "bad cell"???
From your description there is nothing wrong with your battery bank.
Bag your troubleshooting and enjoy your boat. 12.4 volts out of a 12 volt system is just fine!
Here's how lead acid batteries really work on boats.
Your charger will end up while on shore power "floating" your battery bank at somewhere between 13.1 and 13.5 volts. Opinions vary as to the best float voltage but anything in that range will work just fine.
Once you remove shore power the normal loads on your boat will draw current from your batteries. Boats all vary as to the actual loads, but even the smallest cruiser has at least a fridge on all the time.
Your battery voltage will go down and stabilize at 12.0 volts. It will stay at 12.0 volts give or take during much of the discharge cycle.
As the batteries are depleted they will eventually go down in voltage somewhat depending on how deeply you discharge them prior to re-charging.
There is a battery myth floating around here to read the "at rest" voltage of your bank to judge its health and or charge. While that method might be OK for a set of batteries with no load, it is not applicable to a marine house bank, bacause a house bank does not sit "at rest". Even if you removed all loads from your house bank the "at rest" voltage method is not all that good.
From your description there is nothing wrong with your battery bank.
Bag your troubleshooting and enjoy your boat. 12.4 volts out of a 12 volt system is just fine!
Here's how lead acid batteries really work on boats.
Your charger will end up while on shore power "floating" your battery bank at somewhere between 13.1 and 13.5 volts. Opinions vary as to the best float voltage but anything in that range will work just fine.
Once you remove shore power the normal loads on your boat will draw current from your batteries. Boats all vary as to the actual loads, but even the smallest cruiser has at least a fridge on all the time.
Your battery voltage will go down and stabilize at 12.0 volts. It will stay at 12.0 volts give or take during much of the discharge cycle.
As the batteries are depleted they will eventually go down in voltage somewhat depending on how deeply you discharge them prior to re-charging.
There is a battery myth floating around here to read the "at rest" voltage of your bank to judge its health and or charge. While that method might be OK for a set of batteries with no load, it is not applicable to a marine house bank, bacause a house bank does not sit "at rest". Even if you removed all loads from your house bank the "at rest" voltage method is not all that good.
SteveH
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Each cell generates 2.1 V, so doesn't sound like a dead cell.
SteveH
SteveH
Guess I thought there was an issue because the bank used to settle at 12.6 with everything off. The house bank has been in float mode on the three stage charger for a couple of weeks. I did have the big panel switch set on "off" before the "at rest" period, and the fridge was running on AC. For some reason I thought a weak cell in one of the six batteries might pull the overall voltage down. Guess not. Anyway, thanks...I'll not worry about it. Not a big deal at the marina anyway...just thinking ahead for an upcoming extended cruise.
ksanders
Moderator Emeritus
If you really want to test your battery bank, then just unplug your shore power cord, letting your boat discharge the battery bank just like you were on the hook.
I did just that yesterday. I called the harbor and had someone shut off my shore power breaker in the morning.
I monitored the voltage throughout the day, and it stayed at 12.0 volts +- 0.1 volt.
At the end of the day I called the harbor and asked them to turn back on my shore power.
I did not believe I had an issue, but I'd seen some voltage fluctuations on my alarm system so I thought it was a good idea to check. I know my boat draws something around 20 amps +- DC all the time so I know it was a good test.
Here's the cool thing...
I did it from home.
I did just that yesterday. I called the harbor and had someone shut off my shore power breaker in the morning.
I monitored the voltage throughout the day, and it stayed at 12.0 volts +- 0.1 volt.
At the end of the day I called the harbor and asked them to turn back on my shore power.
I did not believe I had an issue, but I'd seen some voltage fluctuations on my alarm system so I thought it was a good idea to check. I know my boat draws something around 20 amps +- DC all the time so I know it was a good test.
Here's the cool thing...
I did it from home.
Since you said getting to the batteries isn't that easy, so no load test or specific gravity readings, unplug from shore power and shut off all your DC loads. After several hours your batteries should be at ~12.65. If they are at 12.4, you need to access them unless your charger isn't working correctly. How's the water level?
How old are your batteries? If they are 5 years old, give or take, they could be just worn out or sulfated.
How old are your batteries? If they are 5 years old, give or take, they could be just worn out or sulfated.
Well, I don't agree with everything that has been said here. A true resting voltage which is what the OP has measured is a valid indicator of battery state of charge. If it was 12.6 and it is now 12.4 then something has changed for the worse.
But, not to belabor it, the simplest way to know the condition of your house batteries is to do a load test. Charge the batteries fully with the shorepower charger then turn it off. Then turn on enough lights or some other continuous load to pull enough current equal to about 1/20 of the battery bank capacity. You will need a clamp on DC ammeter for this.
Then let it sit for as long as it takes for the lights to dim and get down to 10 V or so. Amphour capacity equals average current times hours to discharge.
I have done this for gels and AGMs which can't be checked with a hydrometer and it works.
David
But, not to belabor it, the simplest way to know the condition of your house batteries is to do a load test. Charge the batteries fully with the shorepower charger then turn it off. Then turn on enough lights or some other continuous load to pull enough current equal to about 1/20 of the battery bank capacity. You will need a clamp on DC ammeter for this.
Then let it sit for as long as it takes for the lights to dim and get down to 10 V or so. Amphour capacity equals average current times hours to discharge.
I have done this for gels and AGMs which can't be checked with a hydrometer and it works.
David
Yes, of course. The electrolytes in my brain must be low. I'll shut everything down and check each of them. And then probably do as suggested and turn off the charger and do a long term load check.
The bank is on it's sixth summer...mostly in the slip and on the charger for four months. During the time in the storage building, they get charged roughly once per month. Equalized at Spring launch, mid summer, and before haul out in the Fall. Water levels always kept up. But in spite of light usage, they are getting old. Thanks for the info and advice.
ksanders
Moderator Emeritus
I'm going to be perfectly honest here...
I have been to two several day each battery maintenance schools for flooded lead acid batteries. As part of my profession I have maintained industrial flooded lead acid battery systems in Telephone Central Offices, Microwave sites, Ocean Fiber Landing Satations, and Power Substations for over 30 years.
I say this to give a little history, and perhaps some credance to what I'm going to say.
During all that time, several employers, many many systems, I have NEVER used a no load "at rest" method to determine battery system health. Never.
Most companies I've worked for used a battery discharge test, where we put the batteries on a load for a specific period of time, while measuring the per cell voltage, and intercell (strap) voltage drop, etc...
I do not dispute that some recreatiuonal battery users utilize a "no load" test, but thats not a testing methodology people that work on live industrial battery systems for a living generally use. At least not in the telecommunications, or power industries.
I could stand corrected though. In the last 100+ years of battery system maintenance history the nice folks at the phone company have learned allot about battery maintenance, but clearly not everything.
I have been to two several day each battery maintenance schools for flooded lead acid batteries. As part of my profession I have maintained industrial flooded lead acid battery systems in Telephone Central Offices, Microwave sites, Ocean Fiber Landing Satations, and Power Substations for over 30 years.
I say this to give a little history, and perhaps some credance to what I'm going to say.
During all that time, several employers, many many systems, I have NEVER used a no load "at rest" method to determine battery system health. Never.
Most companies I've worked for used a battery discharge test, where we put the batteries on a load for a specific period of time, while measuring the per cell voltage, and intercell (strap) voltage drop, etc...
I do not dispute that some recreatiuonal battery users utilize a "no load" test, but thats not a testing methodology people that work on live industrial battery systems for a living generally use. At least not in the telecommunications, or power industries.
I could stand corrected though. In the last 100+ years of battery system maintenance history the nice folks at the phone company have learned allot about battery maintenance, but clearly not everything.
psneeld
Guru
I know you have extensive background in all of this....
But for me and a boatload of other captains/marine techs out there....we know it's not really a great test of battery health...most of us load test when in doubt...but a real rough rule of thumb is if you shut off your battery charger and put a couple light loads on it for a few minutes...if you aren't seeing somewhere between 12.5 and 12.6 I would pull out a load tester of devise another load testing strategy.
Doesn't work all the time...but many use it a lot. If I was responsible for keeping systems with the reliability you need...sure other tests are much superior.
psneeld
Guru
Right from EXIDE battery website...crap I know but there's a shread of truth to it.
http://www.exide.com/Media/files/Do...nd Maintenance/Checking battery condition.pdf
Checking Battery Condition
•
Carefully, examine the battery externally.
o
Watch for terminal corrosion on the battery and make sure all connections are clean and tight.
o
If you see any cracks or holes in the container, cover or vents, we recommend you have your
battery replaced.
battery replaced.
•
During regular service intervals, ask your technician to test your battery. This type of test can be
performed quickly by most automotive service centers. These tests will determine your batteries health
by measuring its “State-Of- Charge”.
performed quickly by most automotive service centers. These tests will determine your batteries health
by measuring its “State-Of- Charge”.
Determining State-Of-Charge
12.75 & Above 100% Charged
12.60 to 12.74 85% to 100% Charged
12.40 to 12.59 75% to 85% Charged
12.20 to 12.39 50% to 75% Charged
12.00 to 12.19 25% to 50% Charged
11.99 & Below Fully Discharged
Note: The state of charge listed is an approximation. The relationship between state of charge and voltage vary
by CCA rating and case size.12.60 to 12.74 85% to 100% Charged
12.40 to 12.59 75% to 85% Charged
12.20 to 12.39 50% to 75% Charged
12.00 to 12.19 25% to 50% Charged
11.99 & Below Fully Discharged
Note: The state of charge listed is an approximation. The relationship between state of charge and voltage vary
http://www.exide.com/Media/files/Do...nd Maintenance/Checking battery condition.pdf
ksanders
Moderator Emeritus
Very interesting. I guess there is a difference between what manufacturers tell consumers on their public web sites and what they write in their industrial battery maintenance manuals.
I guess for consumers and automotive batteries they write for the average consumer to check their battery themselves.
Thanks for posting that. At least I know where the information is coming from now. I thought it was just another internet myth.
psneeld
Guru
Many boaters struggle with batt switches in general...the thingies at the end of them are a total mystery...
Baggiolini
Senior Member
Thanks everyone for this great thread. Very relevant for me right now!
BruceK
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The Exide table is much like the one in Ed Sherman`s book.
I use voltage as a basic indicator of need to investigate.
If unsealed, do a hydrometer test.
Skidgear, You looked after them, even equalizing regularly, 5-6 years service is your reward, I think they are just getting old.
I use voltage as a basic indicator of need to investigate.
If unsealed, do a hydrometer test.
Skidgear, You looked after them, even equalizing regularly, 5-6 years service is your reward, I think they are just getting old.
Budds Outlet
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This is a great discussion. Very informative.
Moonstruck
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I had been using the voltage scale as a guide to state of charge. That I found is all it is----a guide. Since installing a state of charge meter, I have found that house batteries are seldom without load. When they are under load they will read less voltage than when resting. I think you will find that at times your batteries are reading lower then bounce back when a big load is removed. The SOC meter counts amps in and amps out to give a true state of charge. A really great tool worth the money and trouble to install.
FF
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A Volt mater will give notice of a problem , but each cell must be tested by specific gravity (with a temp gauge) to actually know what is going on.
All wet batts die slowly thru internal losses.
A new batt will loose 1/2% a day , an old batt perhaps 3% per day.
After 6 years these are definiatly OLD and after a hydrometer check I would look at the charge voltage , sounds like it could be low also.
Beware if the boat is old and has a "converter " which was designed to hold up the voltage with AC power in port and not require frequent watering.
A real battery charger will recharge your batts , the "converter " style may take a week or more.
All wet batts die slowly thru internal losses.
A new batt will loose 1/2% a day , an old batt perhaps 3% per day.
After 6 years these are definiatly OLD and after a hydrometer check I would look at the charge voltage , sounds like it could be low also.
Beware if the boat is old and has a "converter " which was designed to hold up the voltage with AC power in port and not require frequent watering.
A real battery charger will recharge your batts , the "converter " style may take a week or more.
ksanders
Moderator Emeritus
OK, so how about some practical, meaningful , easy to do real world flooded lead acid battery checking you can do on your boat.
This is going to sound over simplified to some, but alas things do not need to be overly complicated to be useful.
Its easy.
Oh, and if you have the inclination, install a battery monitor. I use the Xantrex Link units and love them. Would not have a boat without one.
This is going to sound over simplified to some, but alas things do not need to be overly complicated to be useful.
Its easy.
- With the shore power on, assuming it has been on and your batteries are charged, read the voltage. It should be something around 13.25 to 13.5 volts. If its much lower your batteries are not getting a full charge. If its too much higher, your batteries are getting overcharged.
- Turn off your shore power. Leave things running just like if you were on the hook.
- Wait a few hours.
- Assuming you have 6 volt batteries, measure each of them with a voltmeter.
- Compare those numbers with each other. If they are much different, then you have a problem. Time for a replacement.
- Turn back on your battery charger.
- After a few minutes feel for heat. Just touch each connection, and the top of each battery.
- If a connection feels warmer than others, take it apart, clean and re-assemble.
- If a battery feels warm, then you have a problem. Replace it
Oh, and if you have the inclination, install a battery monitor. I use the Xantrex Link units and love them. Would not have a boat without one.
Wxx3
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Remote monitoring
Thanks Kevin,
Your posts are always interesting and informative.
I just recently added a Victron BMV 600 battery monitor for my house bank (980 amp hours). Love it.
Also, I would love to be able to monitor the boat remotely, but have no wifi or internet connection on boat. I have to use my verizon hotspot for wireless for my computer.
Any suggestions? It would have to run through a cell phone??
Thanks Kevin,
Your posts are always interesting and informative.
I just recently added a Victron BMV 600 battery monitor for my house bank (980 amp hours). Love it.
Also, I would love to be able to monitor the boat remotely, but have no wifi or internet connection on boat. I have to use my verizon hotspot for wireless for my computer.
Any suggestions? It would have to run through a cell phone??
ksanders
Moderator Emeritus
Thanks Kevin,
Your posts are always interesting and informative.
I just recently added a Victron BMV 600 battery monitor for my house bank (980 amp hours). Love it.
Also, I would love to be able to monitor the boat remotely, but have no wifi or internet connection on boat. I have to use my verizon hotspot for wireless for my computer.
Any suggestions? It would have to run through a cell phone??
980 amp hour bank??? Cool! what batteries are you running?
We are running L16HC batteries at 420AH per cell for a total of 840 AH of capacity.
For remote monitoring you could use a mifi usb modem plugged into a cradlepoint router www.cradlepoint.com
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Wxx3
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4 8-Ds AGM for House and bow thruster
Grp 27 for starter
Grp 24 (I think) for Gen
PO had two banks of 2 each 8-Ds for house and starter. I didn't like that setup as it had the dual disadvantages of being able to totally drain start batteries and at same time, run the house batteries lower than good for them.
Now I can go about 24 hours on hook, with no gen.
My goal is to not have to use gen, and if I do, it means it's time to move on.
Also have changed all interior, anchor and spreader lights to LEDs and will change running lights also.
Richard
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sunchaser
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For most of us, the cheapest and most reliable source of power we have is a well maintained genset. For us power boaters, I've never understood the fascination for spending 1000 of dollars on the latest (iffy and unreliable at times) technoloy and gizmos for solar, wind, Li batteris etc. A nice simple inverter/charger, adequate sized house bank and good genset is pretty hard to beat providing safety and comfort for thousands of boaters in the past, present and future.
BruceK
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Add some solar, you`ll need quite a lot with your battery capacity, and you may be moving less.Now I can go about 24 hours on hook, with no gen.
My goal is to not have to use gen, and if I do, it means it's time to move on.
Wxx3
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While I have a gen set, for me it's simply a matter of intrinsic value.
1. I can't see the point of running an auxiliary engine, when my main engine can move me from A to B and charge batteries for virtually nothing.
2. For us, a big reason to have a boat, is to get off the grid and do so in the least intrusive manner.
Ricahrd
1. I can't see the point of running an auxiliary engine, when my main engine can move me from A to B and charge batteries for virtually nothing.
2. For us, a big reason to have a boat, is to get off the grid and do so in the least intrusive manner.
Ricahrd
ksanders
Moderator Emeritus
4 8-Ds AGM for House and bow thruster
Grp 27 for starter
Grp 24 (I think) for Gen
PO had two banks of 2 each 8-Ds for house and starter. I didn't like that setup as it had the dual disadvantages of being able to totally drain start batteries and at same time, run the house batteries lower than good for them.
Now I can go about 24 hours on hook, with no gen.
My goal is to not have to use gen, and if I do, it means it's time to move on.
Also have changed all interior, anchor and spreader lights to LEDs and will change running lights also.
Richard
Very nice!
Wer wentwi th LEDs as well. Bought 70 of them on ebay and have maybe 5 left over. The difference in our current draw is incredible.
FF
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For us, a big reason to have a boat, is to get off the grid and do so in the least intrusive manner.
The usual choice then is not a noisemaker or a ton of lead .
A propane reefer , range and HW heater does the job in silence , silent endurance measured in weeks or months , not hours.
The usual choice then is not a noisemaker or a ton of lead .
A propane reefer , range and HW heater does the job in silence , silent endurance measured in weeks or months , not hours.
ksanders
Moderator Emeritus
Very well said.
For our boat the 840 AH bank is just about right. Our generator at 9KW is just the right size and very quiet.
Right now I am sitting on the boat, in the salon, having a cup of coffee and the generator is running. I can hear it in the background, but it is very quiet. My Iphone app shows the sound level at 62db.
We have a high capacity alternator on one of the engines, and consider it, the generator, the house bank, and the 3KW inverter/charger all to be parts of a logicaly laid out power system.
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