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Old 23-06-2018, 04:46   #1
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Do I need to replace my batteries?

I have been reading a lot about batteries on this forum and it is clearly a very complex subject - there are some quite different and sometimes contradictory points of view on how to get the best life from them and how long they should last. I am therefore not expecting simple answer, but I would appreciate and be grateful for some expert opinions.....

I have 4 Varta Professional 180Ah 930 180 100 batteries as my service bank. I also have one Varta Promotive 180Ah M16 680 109 100 as my engine starting battery. I don't know exactly how old the batteries are, I inherited them with the boat, but I have owned the boat for 3 years. I charge the batteries using shore power or my generator when the service bank voltage drops to 11.9v (I don't generally monitor the engine start battery voltage, but typically when the service bank drops to 11.9 it is higher at ~12.6v). I have a Mastervolt Mass 12/60 battery charger. When I charge on shore power I charge continuously. When I charge on the generator I charge for approx 1 hour in the morning and 1 hour in the evening or until the service bank voltage shows 13.5v.

Generally the only significant load on the service bank is the fridge and my understanding is that there is no load on the engine start battery other than starting the engine or generator.

On a couple of occasions recently I have started the engine in the morning then sailed all day. Although in the evening the service bank is showing 12.0/11.9v and the engine battery has been turned off all day, when I have tried to start the engine there has not been sufficient power to turn over the engine. Fortunately there has been enough power to start the generator so it has been necessary for me to start the generator and charge the batteries for a few minutes (5?) before I can start the engine.

My questions are several......
1. Am I discharging the batteries too much?
2. Am i not charging the batteries enough?
3. Are my batteries at the end of their useful life and do I need to replace them?
4. Is there anything I can do to increase their longevity now?
5. If they need replacement, what can i do to the new ones to maximise their life?

All advice and information grateful received, and preferably with the minimum of technical language, because as you may have gathered I don't have a huge understanding of this subject.
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Old 23-06-2018, 05:06   #2
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Re: Do I need to replace my batteries?

Well get ready to climb that learning curve, sure rules of thumb are fine, but to take care of an expensive bank really requires understanding **how to** follow them, measure volts and amps at the right locations, not just believe what the gear is telling you, adjusting from factory defaults.

It's not rocket science though, don't be intimidated.
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Old 23-06-2018, 05:10   #3
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Re: Do I need to replace my batteries?

The only way to accurately judge the bank's State of Health, without lab-rated gear costing thousands, is to determine residual AH capacity at a standard discharge rate usually 20-hours.

Search for

20 hour capacity test

here https://marinehowto.com/programming-a-battery-monitor/

You can of course pay a pro to do it for you.
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Old 23-06-2018, 05:10   #4
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Re: Do I need to replace my batteries?

Is the volt meter the only way you have to monitor the banks? you might consider a battery monitor. A couple of options are:

SmartGauge Electronics - Homepage

https://www.nasamarine.com/product-c...tery-monitors/

Both have been discussed at length on CF, so worth searching the forums.

The worrying bit is the engine start battery that can't start your engine even if it has been run earlier in the day. Firstly are you sure that the battery doesn't have any connection to the house bank that might be affecting it or any other loads which are draining the battery? Do you have a hydrometer to check the SG? and whilst your at it are the batteries topped up? Does the generator have its own battery btw? That said sounds like the engine start battery isn't gettinng enough charge or is knackered or both. You might ask yourself if you really need a 180AH battery to start the engine before buying a smaller more suitable replacement.

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Old 23-06-2018, 05:11   #5
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Re: Do I need to replace my batteries?

As far as proper care for maximizing longevity goes,

there's a pretty canonical post from top guru Maine Sail in this thread What count as a cycle (battery life)

and read key articles on electrickery at his marinehowto.com site.

When you come across terms you don't know, do some googling, then ask Qs here if you still need to clarify.
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Old 23-06-2018, 05:19   #6
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Re: Do I need to replace my batteries?

Quote:
Originally Posted by Paramotorgreg View Post
Generally the only significant load on the service bank is the fridge and my understanding is that there is no load on the engine start battery other than starting the engine or generator.

On a couple of occasions recently I have started the engine in the morning then sailed all day. Although in the evening the service bank is showing 12.0/11.9v and the engine battery has been turned off all day, when I have tried to start the engine there has not been sufficient power to turn over the engine. Fortunately there has been enough power to start the generator so it has been necessary for me to start the generator and charge the batteries for a few minutes (5?) before I can start the engine.

Some info that may help folks help you diagnose...

- confirm there's no connection between start battery and house bank (excepting multi-bank charger)

- if there's no connection, have you serviced (watered) the start battery periodically?

- have you checked specific gravity on the start battery?

Some of that is leading toward whether your engine alternator is working properly, or whether your start battery just needs some service, or whether it's toast

Probably useful to check all that ref your genset battery, too, assuming it's separate and assuming the generator charges that battery when in use.

This is also a start of a "divide and conquer" approach, maybe a way to separate problems and solve one at a time.

-Chris
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Old 23-06-2018, 10:35   #7
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Thumbs up Re: Do I need to replace my batteries?

Google how to revive your old battery. Clean with baking soda. Rejuvenate with Epsom salt. Will boost battery for another year or so.
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Old 23-06-2018, 10:49   #8
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Re: Do I need to replace my batteries?

At one point on my boat,please keep in mind new to me & no communication with seller because it was purchased through a dealer. On my way home across the Gulf of Mexico I was sailing under autopilot. At the end of the day I went to start the motor and it would not start but I knew that that battery was brand new as I had just replaced it before I left. Imagine my surprise when I learned that the autopilot was running off of the engine start battery! Just something to check to make sure that there is nothing else draining the start battery
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Old 23-06-2018, 10:53   #9
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Re: Do I need to replace my batteries?

Just guessing your engine start battery is not holding the charge and needs replaced. But make sure the posts are clean, sometimes an invisible "wet corrosion" is in there and blocks draw and charging. But you also need to make sure there is no draw on that start battery if you dont know your system well.
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Old 23-06-2018, 10:56   #10
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Re: Do I need to replace my batteries?

As has been previously noted, there's quite a bit to learn about battery monitoring, performance and longevity.

Some battery monitors track the amps going into and coming out of your batteries and thereby determine their state of charge. Ie, if you have a bank that can store 400 amp hours and the battery monitor measures 200 amp hours coming out, you'd be at 50% state of charge. If you pump 200 amp hours (plus a bit to account for inefficiencies), you're back to a fully charged battery bank.

Other monitors use some proprietary algorithms to determine your battery's state of charge using only the voltage (Sterling makes that one, Balmar sells it on this side of the pond). This monitor also give SOC as a percentage. If you get this type of monitor, you should also have an amp meter so you can tell what your charging sources (alternator, battery charger, solar, etc) are doing.

The numbers that you report in your post suggest that you have been under charging your house bank. Lead acid batteries have a maximum charge voltage of about 14.4 volts (it varies a little depending on type of battery, such as flooded vs gel vs AGM). Once the battery reaches 14.4 volts it's at about 80% SOC. A smart battery charger will start lowering its charge rate whilst maintaining 14.4 v (called the acceptance voltage) until the battery is fully charged, which is indicated by the rate of charge getting down to about 4% of capacity, or 16 amps in our example. Some battery chargers don't actually use the number of amps to determine the end of the absorption phase, but use a timer and guess. Once the batteries are fully charged, the charger should float the batteries at about 13.4 volts to maintain the charge but not over charge the batteries.

The fact that you are only charging your batteries until you get to 13 odd volts indicates that you are under charging them, which will kill 'em sooner rather than later.

Last but not least, the fact that your engine start battery won't crank the engine at the end of the day (unless you are inadvertently discharging it into a house load) strongly suggests that it is toast.

If 'in I were you, I'd replace the batteries, make sure I've got a three-stage battery charger that can be programmed for your house bank capacity and install an amp meter and some kind of SOC monitor (could be combined, of course).

Scott
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Old 23-06-2018, 11:32   #11
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Re: Do I need to replace my batteries?

There are at least two parameters missing in this discussion.

(1) How large is your engine. If I am reading your boat description (congratulations) it is a 50, which means to me that the engine could be larger and require many kilowatts of power to get it started if it doesn't start promptly. Many smaller vessels are powered by what is actually a lawn tractor motor that could probably be started with a 20 AH battery.

(2) A real battery charge needs to have the current and voltage monitored. The battery voltage will become higher BUT the battery is still not fully charged until the current decreases at the new voltage level.

So if the main engine battery was not fully charged after start-up it could be that the battery simply went back to it's undercharged state after sitting all day. There are probably static loads on the start-battery to discharge it some anyway.


I would do a hydrometer test while charging (assuming it is a wet battery and not sealed) until it is charged and then a load test to determine what its' capacity currently is. If your system can live with its' capacity you do not require a new battery.
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Old 23-06-2018, 13:04   #12
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Re: Do I need to replace my batteries?

First most replies are accurate here. There are plenty of web sites that talk thru this issue.

If you do not have a way to measure amps going into your batteries you need one. The charging process will show battery charger voltage around 14.4 with amps about 70-80 % if your chargers capacity.

In an hour or so ( assuming your batteries were at 50%) they should show 13.3 V and about 5-10 Amps going in.

Another thing....led acid and AGM batteries should be recharged when they hit 50% which in your case is 12.3V. Letting them go below 12 shortens their life considerably. ( see recycling curves supplied on these web sites)

If you have been routinely letting your batteries get to 11.9V Id really think about replacing but at the same time add a good battery monitor!
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Old 23-06-2018, 13:55   #13
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Re: Do I need to replace my batteries?

Since these batteries are (relatively) new to you, and since you did not mention your maintenance habits, I think the first, easiest and cheapest thing you should do is check the electrolyte level in all your batteries. A battery cannot take or hold a proper charge unless it is properly topped off. Just mho.
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Old 23-06-2018, 14:45   #14
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Re: Do I need to replace my batteries?

Steps:

1. Clean the tops of all batteries.
2. Remove and Clean the terminals of all batteries.
3.Check battery water levels (if serviceable). Top with distilled of de-ionized water only.
4. When batteries are discharged to 12.2 Vdc (with no significant load), apply charger.
5 The Smart charge voltage should start somewhat low (e.g 13,2 Vdc) and slowly increase to about 14.2 Vdc where I will stay for a long time.
6. At some point (Perhaps hours) the charger will go into float mode (~13.4 Vdc) and stay there indefinitely (unless a large load is applied).

If you have a battery hat has proper water level, clean terminals, and alternator charge voltage shows 13.2 Vdc for 8 hours of run time, there is no other load on it, and it wont stay charged and start the engine weeks later, replace the start battery.
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Old 23-06-2018, 15:00   #15
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Re: Do I need to replace my batteries?

It sounds to me as though you need to replace the engine starting battery. Usually these are not "Deep Cycle" and have heavy loads when in use--so they do not last as long.

Many years ago I was involved in telecommunications, and we used flooded cell batteries to power our telephone exchanges in the event of mains failure.

These batteries were routinely discharged by one tenth of their ampere-hour capacity, then re-charged. It is true they were stored in optimum conditions and were not subject to movement--and were similar to the types of cells used in submarine battery rooms of the day. They were made by Chloride as I recall--the same company that made EXIDE. I had a car battery by EXIDE that lasted ten years--but that battery was mounted under the vehicle not in the engine bay, and was topped op by distilled water as required, and charged by a generator and voltage regulator, not an alternator. A DC generator is a longer, deeper and softer charging method...

So--your house batteries may still be OK. It sounds as though you are not over-depleting them before recharging them--and that is what these deep cycle batteries prefer.

The Telephone Exchange batteries for the old Strowger types and Cross-bar types of exchanges were of the deep-cycle type, (there were two banks of them) and they lasted as long as twenty years before we replaced them, but they were hardly ever drained in earnest. Most power outages only lasted a few hours at most.
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