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Old 29-02-2016, 21:33   #1
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Understanding batteries on a boat

I dont know very much about batteries and electricity management. I've been trying to understand the setup on my boat but even after reading through manuals and resources online i still dont quite get it. What i'm about to ask will probably sound very silly but bear with me (no such thing as stupid questions right?)

I have four 6 Volt golf cart batteries and a Truecharge 40 Battery Charger. I'm connected on a shoreline and most of the time i keep my battery charger on, though even if its at full charge it always seems to be charging. The Truecharge is making a lot of noise, at first i thought it was because the batteries needed a bit of maintenance but they seem fine. Should I keep my battery charger on at all times?
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Old 29-02-2016, 22:23   #2
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Re: Understanding batteries on a boat

There are some recognised experts here that can help. I'm sure they will respond.

But let me ask,.....

Which mode on the charger are you using? I think bulk/absorb/float is correct for 24/7 operation.

How many banks do you have? All six in one? Or?

Are all the batteries the same age and relative condition?
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Old 29-02-2016, 22:38   #3
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Re: Understanding batteries on a boat

The Truecharge will try to hold the float voltage, which means that if you are taking any load at all from the batteries, even something as small as a light bulb, the charger is constantly turning on and off, and the fan is quite noisy.

I turn mine off in the evenings and at night. The battery capacity is quite ample to power everything overnight.
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Old 01-03-2016, 15:57   #4
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Re: Understanding batteries on a boat

You don't say how why you think the batteries are okay. Have you been away from the dock and the AC charger much? Or just turned off the charger/unplugged from shorepower and tried to get through a day and night just on batteries? Potential capacity is one thing, actual on older batteries can be much less.

You should start with some of the excellent primers on 12 volt DC boat systems. Other have posted the links. May be someone will get on and give those to you.
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Old 01-03-2016, 20:04   #5
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Re: Understanding batteries on a boat

Keeping the batteries at float voltage all the time (charger on) means the batteries will not have much of a chance to sulfonate. This helps keep the batteries healthy. However, with the charger on, if your batteries are standard wet cells, there is periodic maintenance to do. The more advanced chargers have a temperature sensor. The ideal float voltage will depend on the battery temperature. Load testing is a good way to test the health of your batteries.
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Old 01-03-2016, 20:16   #6
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Re: Understanding batteries on a boat

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Originally Posted by exMaggieDrum View Post
You should start with some of the excellent primers on 12 volt DC boat systems. Other have posted the links. May be someone will get on and give those to you.
You could start here:

Electrical Systems 101 Electrical Systems 101
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Old 01-03-2016, 20:39   #7
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Re: Understanding batteries on a boat

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Keeping the batteries at float voltage all the time (charger on) means the batteries will not have much of a chance to sulfonate. This helps keep the batteries healthy. However, with the charger on, if your batteries are standard wet cells, there is periodic maintenance to do. The more advanced chargers have a temperature sensor. The ideal float voltage will depend on the battery temperature. Load testing is a good way to test the health of your batteries.
The temperature sensor for the Truecharge is an optional extra, and I'd strongly recommend installing it. Since I did, my electrolyte usage dropped precipitously.
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Old 02-03-2016, 08:01   #8
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Re: Understanding batteries on a boat

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Originally Posted by SteveInMD View Post
Keeping the batteries at float voltage all the time (charger on) means the batteries will not have much of a chance to sulfonate. This helps keep the batteries healthy. However, with the charger on, if your batteries are standard wet cells, there is periodic maintenance to do. The more advanced chargers have a temperature sensor. The ideal float voltage will depend on the battery temperature. Load testing is a good way to test the health of your batteries.
Whether the batteries are sulfated depends on their history and since the batteries predate the OP's purchase, that is an unknown. Keeping them on a charger after they are sulfated will not repair that. Equilizing would help if that is the case but it will only help to a point.

Load testing with a carbon pile or capacitance tester will NOT tell you how good deep cycle batteries are. The only way to do that with any reliability is to do a draw down test over a few days following a strict protocol. Using the batteries off the charger is the next best thing but not scientific, but will tell you if there is enough there to use them for what you want to use them for.
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Old 02-03-2016, 08:33   #9
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Re: Understanding batteries on a boat

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Whether the batteries are sulfated depends on their history and since the batteries predate the OP's purchase, that is an unknown. Keeping them on a charger after they are sulfated will not repair that. Equilizing would help if that is the case but it will only help to a point.

Load testing with a carbon pile or capacitance tester will NOT tell you how good deep cycle batteries are. The only way to do that with any reliability is to do a draw down test over a few days following a strict protocol. Using the batteries off the charger is the next best thing but not scientific, but will tell you if there is enough there to use them for what you want to use them for.
Whoa... slow down a bit for you trash my advice. The general concept that maintaining float voltage will reduce the rate of sulfonation is totally correct. This addresses the OPs question about leaving the charger on all of the time or not. Batteries are complex. Given the questions I'm trying to keep the advice fairly simple to start out with. The question was not 'are my batteries sulfonated and if there how do I repair them?' It was simply should I leave my charger on all of the time. The answer is generally, yes.

Further, if the batteries fail a basic load test it certainly does give you information about their health. Yes, there are more involved tests.
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Old 02-03-2016, 08:34   #10
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Re: Understanding batteries on a boat

"a lot of noise" is somewhat vague. If the Truecharge uses large transformer, sometimes the metal plates in a transformer separate very slightly. It still works fine that way, but then they "buzz" as they vibrate against each other, as the AC cycle reverses constantly. So if what you hear is buzzing, it pays to check everything out but it may just be the transformer. (PITA to try fixing, expensive to replace, usually ignored.)
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Old 02-03-2016, 17:00   #11
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Re: Understanding batteries on a boat

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Whoa... slow down a bit for you trash my advice. The general concept that maintaining float voltage will reduce the rate of sulfonation is totally correct. This addresses the OPs question about leaving the charger on all of the time or not. Batteries are complex. Given the questions I'm trying to keep the advice fairly simple to start out with. The question was not 'are my batteries sulfonated and if there how do I repair them?' It was simply should I leave my charger on all of the time. The answer is generally, yes.

Further, if the batteries fail a basic load test it certainly does give you information about their health. Yes, there are more involved tests.
Steve, I wasn't trying to trash anybody's advice. And I am like you with my AGM's (and would do the same with any LA batteries), I keep the shorepower charger on all the time. Nothing wrong with that if the charger has adequate setpoints to prevent overcharging the batteries. Leaving them on the charger is good for them versus letting them sit and losing SOC daily just sitting there. That will lead to sulfating over time.

Battery testing has been a semi-controversial thing for deep cycle batteries for a long time. I have tested hundreds of batteries (as a marine electrical tech) and we tried all the gear that was/is available. The fact is that none of the gear available to this day will even give a remote clue to how much capacity a deep cycle battery has. If the battery is on its very last legs and has very little charge left then a tester may sorta kinda indicate that. Find with me if you have a different opinion. I have discussed it with Trojan and Lifeline several times and that is what they say too.

stopped doing deep cycle tests (where we could have made easy money) as we could not give the customers any useful information. And we didn't really know if a battery was really going to have much capacity so the some customers would come back in and complain that the battery we said was good would not keep them going overnight in some distant anchorage.

Perhaps we were wrong but that is what we did. But keeping the charger on is good so long as it is regulated reliably. Not good if it boils the batteries just sitting there, or keeps them at 12.5v for long periods.
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Old 02-03-2016, 17:01   #12
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Re: Understanding batteries on a boat

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Originally Posted by SteveInMD View Post
Whoa... slow down a bit for you trash my advice. The general concept that maintaining float voltage will reduce the rate of sulfonation is totally correct. This addresses the OPs question about leaving the charger on all of the time or not. Batteries are complex. Given the questions I'm trying to keep the advice fairly simple to start out with. The question was not 'are my batteries sulfonated and if there how do I repair them?' It was simply should I leave my charger on all of the time. The answer is generally, yes.

Further, if the batteries fail a basic load test it certainly does give you information about their health. Yes, there are more involved tests.
Steve, I wasn't trying to trash anybody's advice. And I am like you with my AGM's (and would do the same with any LA batteries), I keep the shorepower charger on all the time. Nothing wrong with that if the charger has adequate setpoints to prevent overcharging the batteries. Leaving them on the charger is good for them versus letting them sit and losing SOC daily just sitting there. That will lead to sulfating over time.

Battery testing has been a semi-controversial thing for deep cycle batteries for a long time. I have tested hundreds of batteries (as a marine electrical tech) and we tried all the gear that was/is available. The fact is that none of the gear available to this day will even give a remote clue to how much capacity a deep cycle battery has. If the battery is on its very last legs and has very little charge left then a tester may sorta kinda indicate that. Find with me if you have a different opinion. I have discussed it with Trojan and Lifeline several times and that is what they say too.

We stopped doing deep cycle tests (where we could have made easy money) as we could not give the customers any useful information. And we didn't really know if a battery was really going to have much capacity so the some customers would come back in and complain that the battery we said was good would not keep them going overnight in some distant anchorage.

Perhaps we were wrong but that is what we did. But keeping the charger on is good so long as it is regulated reliably. Not good if it boils the batteries just sitting there, or keeps them at 12.5v for long periods.
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Old 02-03-2016, 17:28   #13
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Re: Understanding batteries on a boat

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....
Battery testing has been a semi-controversial thing for deep cycle batteries for a long time. I have tested hundreds of batteries (as a marine electrical tech) and we tried all the gear that was/is available. The fact is that none of the gear available to this day will even give a remote clue to how much capacity a deep cycle battery has. If the battery is on its very last legs and has very little charge left then a tester may sorta kinda indicate that. Find with me if you have a different opinion........
Perhaps a bit off topic but still kind of related- I don't really understand why capacity testing is controversial. I do a bit of capacity testing at work and it seems clear to me that if done correctly, it tells me exactly what capacity the battery is still capable of.

For instance, I set a constant discharge rate and and end point voltage and connect a fully charged and rested battery to it. The tester monitors the time elasped and thus gives the actual battery capacity at that time and for the parameters stated. Put the same battery (recharged) into the boat and apply a similar load to it and will take the same time to discharge to the same point. The battery doesn't care if it connected to the boat load or the tester - surely?

For instance, sometime back, I accidently deeply discharged a aged 150AH AGM. After conditioning it, it tested still to be 100AH. I repeated the charging and capacity testing cycles a few times and the results stayed the same ~ 100AH. I remain convinced the battery retains this capacity although I'm sure it's cycle life is significantly reduced. No way of NDT that.
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Old 03-03-2016, 08:16   #14
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Re: Understanding batteries on a boat

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Perhaps a bit off topic but still kind of related- I don't really understand why capacity testing is controversial. I do a bit of capacity testing at work and it seems clear to me that if done correctly, it tells me exactly what capacity the battery is still capable of.

For instance, I set a constant discharge rate and and end point voltage and connect a fully charged and rested battery to it. The tester monitors the time elasped and thus gives the actual battery capacity at that time and for the parameters stated. Put the same battery (recharged) into the boat and apply a similar load to it and will take the same time to discharge to the same point. The battery doesn't care if it connected to the boat load or the tester - surely?

For instance, sometime back, I accidently deeply discharged a aged 150AH AGM. After conditioning it, it tested still to be 100AH. I repeated the charging and capacity testing cycles a few times and the results stayed the same ~ 100AH. I remain convinced the battery retains this capacity although I'm sure it's cycle life is significantly reduced. No way of NDT that.
Wotname - you have described how a deep cycle battery can be accurately tested for capacity. Agree completely. The problem comes from how much trouble it is to set up to measure that capacity. The test load has to be a known wattage and it has to be maintained over the length of the test period. The battery cannot be used for other purposes for that time and the load has to be at a 20 hour rate to arrive at the 20hr deep cycle capacity rating that comes with batteries. The battery has to be started at an absolutely full state and discharged down to a known voltage and then the time taken to get to that state gives the capacity. The battery cannot be on a charge and no load other than the test load. The setup and timing is way more than your average owner will undertake. It is very expensive to get a professional to do it as well due to the setup and monitoring requiring at least two visits to the boat.

So it is possible. But a carbon pile tester will not work nor will the very expensive capacitance testers nor will volt/amp meters nor will battery SOC monitors. So that is why I said what I did. If someone is able and willing to go through the process we both agree is acceptable, then yes they can get a pretty good capacity reading.
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Old 03-03-2016, 08:37   #15
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Re: Understanding batteries on a boat

I agree completely. Not only is reliable load testing time-consuming and a PITA, but it is EXPENSIVE as well.

Consider this:

1. a variable & preferably programmable electronic load device which presents the desired purely resistive and constant load to the battery under test;

2. calibration steps to be sure the voltage and amperage values are accurate over time; and

3. a means of disconnecting the load when the battery voltage reaches 10.5VDC.

Given the right programmable and automated equipment, such as the Array Load tester used by MaineSail, this CAN be done on a boat, but it's still a pain and is still expensive.

Unfortunately, there's no other reliable means to measure residual capacity of a battery or battery bank, though there are proxy indicators which with sufficient knowledge and experience MAY help in estimating battery health.

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