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Daily battery charging


Jstupot

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Solar is really very good these days but winter is always difficult, I would have a bit of solar no matter what else I had just for keeping the batts. charged if I went away for a week or two. Also a Beta 43 (I've got one as well) is mighty overkill just for turning an alternator, I would look for a separate generator, even a cheap and cheerful e bay 'bargain' to save wearing out the Beta. Get a long lead line, put the genny a long way from other people and yourselves and job done.

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Whilst two to four hours engine running MIGHT be sufficient to get enough electricity back into the battery to last the night it is very unlikely that it will fully charge it. With just the alternator you will need to run for at least 8 hours at least once a week and much of that time you will be pitting very little charge into your battery. If you do not fully charge regularly the batteries will gradually sulphate and that means they will lose capacity. Liveaboards who do not fully charge their batteries regularly can wreck a set in weeks.

 

This is why significant solar is so good. In the middle of summer you may not have to run the engine. In winter you can do the four hours charge and for the rest of daylight the solar will help to get the batteries fully charged. having said that in the depths of winter the solar contribution is likely to be small.

 

I agree with the ammeter and voltmeter comment as the bare minimum of battery monitoring you will need but you MUST learn how to use them to make fairly accurate inferences about the state of charge. A Smartguage just makes deciding when to start charging easier. There is much for you to learn here if you want to maximise your battery life but we can advise on that later when you have digested this lot.

 

There is no point in running the engine on idle until the later stages of charging. An ammeter will allow you to run at whatever revs are needed to keep the alternator output as high as it will go. This speed will gradually reduce as the charging progresses. In the early stages of charging the alternator load on the engine may well be higher than the load when canal cruising and keeping a diesel under load is always good.

 

The alternator will be charging once the "ignition" warning lamp goes out. This may need a bit of a rev but as long as it stays out some charge will be produced.

 

There is much you have not told us about your boat like how many alternators and their rated output. Also the battery bank size in Ah. You probably do not know this but you really need to find out. I guess you have two alternators and three x 110Ah batteries but it is only a guess.

 

Finally I do not like people assuming that I and others who reply seriously will take the mickey, even if the way a question is presented invites some smart replies. You will note someone else has also said as much. If you upset people I assume that you would not expect much help.

He means it, just weeks. You need to get it under control ASAP or you may be buying new batteries very soon.

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He means it, just weeks. You need to get it under control ASAP or you may be buying new batteries very soon.

 

 

From what the OP said I get the impression he thinks charging 'little and often' is the way to keep the batteries fully charged.

 

"We are really not sure how often we should charge the batteries on a daily basis with general living aboard in mind...."

 

Charging the batteries daily isn't really a Good Idea as charging is not linear. The last 15% of charge takes 50% of the time. Better in my opinion to run them down to about 50% over about a week, then give them one long charge to bring them back up to 100% on say, Saturday. This will take about 8 hours with a suitably-sized charger.

 

More or bigger batteries may be needed to last a week between charges in mid winter. In spring/summer/autumn solar may well be enough.

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From what the OP said I get the impression he thinks charging 'little and often' is the way to keep the batteries fully charged.

 

"We are really not sure how often we should charge the batteries on a daily basis with general living aboard in mind...."

 

Charging the batteries daily isn't really a Good Idea as charging is not linear. The last 15% of charge takes 50% of the time. Better in my opinion to run them down to about 50% over about a week, then give them one long charge to bring them back up to 100% on say, Saturday. This will take about 8 hours with a suitably-sized charger.

 

More or bigger batteries may be needed to last a week between charges in mid winter. In spring/summer/autumn solar may well be enough.

That may be fine for your batteries Mike, but possibly running them down to 50% on other peoples boats will take less than a week.

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Tony has given good advice.

Generally speaking batteries do better with shallow discharges than deep ones, so I prefer daily charging rather than leaving it longer.

Solar panels are a good way of finishing off charging but for the next 4 months they won't achieve much. Today mine were running at 5% capacity. If you do go solar fit as much capacity as you can afford or fit. If you go that route it may be best to start a new thread.

 

Top Cat

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I'd be interested in reading some more on solar as for my weekends n holidays use there would seem to be real benefits.

Its certainly worth having. Lots of threads on here (use the search). The cost of solar has dropped over the last few years. Even when your not on your holiday/weekends your batteries will be on charge (assuming some light)

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You should discover that cruising is essential! a weekend away cruising should charge the batteries then two hours a day should delay the discharge a little.

 

You will need to buy and fit a Smartgauge and charge the batteries fully a couple of times before it gives a reasonable reading.

 

The fridge will use enough electricity to kill your batteries easily so as soon as the local temperature goes down to less than 10C you could turn the fridge off and keep food in a cool place.

 

Batteries are a consumable! They will last three months with a moderate charge regime, two years if you care for them but they can be killed in a week if left flat.

 

Find the nearest place to recharge overnight from a shoreline, find a generator charger and find and fit solar ASAP. 200w of solar is good for an electrofrugal life in summer. 1000w is much better. You will get about 10% of rated power off solar in the darker four months of the year. A mooring with a shoreline will provide all the comforts of home and is probably well worth the money.

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From what the OP said I get the impression he thinks charging 'little and often' is the way to keep the batteries fully charged.

 

"We are really not sure how often we should charge the batteries on a daily basis with general living aboard in mind...."

 

Charging the batteries daily isn't really a Good Idea as charging is not linear. The last 15% of charge takes 50% of the time. Better in my opinion to run them down to about 50% over about a week, then give them one long charge to bring them back up to 100% on say, Saturday. This will take about 8 hours with a suitably-sized charger.

 

More or bigger batteries may be needed to last a week between charges in mid winter. In spring/summer/autumn solar may well be enough.

 

 

I know exactly why you say this but it is very much dependant on each individual boater's needs. Admittedly the OP has not listed a massive discharge load but I am far from sure this is the case. I do not recall seeing any fridge listed. It could well turn out that having put sufficient battery capacity in it would take longer than 8 hours to recharge once a week. I think daily charging to (say) 80% and weekly charging to 100% is probably the best compromise that will work for the majority of boaters..

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Whilst I totally respect what others are saying, there are lots of variables.

The less you use, the less you need to replace.

I have 12volt fridge, water ppumps, led lights; then laptop, dab radio, boombox, & phones which get charged while engine runs.

My engine runs for a couple of hours every other day, always on tickover. The alternator is big. 240amp. Longish 5 or 6 hour cruise at least once a week, mostly on tickover (big engine)

Batteries (4 x 110ah when new) are now 3 years old.

No problems yet, and I've saved a fortune in diesel compared to some on here.

These days, batteries are cheaper than diesel; silence is golden

If you had a larger energy use & 70amp alternator, you'd need to charge longer & more often.

Just my experience.

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I know exactly why you say this but it is very much dependant on each individual boater's needs. Admittedly the OP has not listed a massive discharge load but I am far from sure this is the case. I do not recall seeing any fridge listed. It could well turn out that having put sufficient battery capacity in it would take longer than 8 hours to recharge once a week. I think daily charging to (say) 80% and weekly charging to 100% is probably the best compromise that will work for the majority of boaters..

In his op he said he had a fridge.

 

Neil

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I disagree with the last bit. An ammeter is moderately useful for determining when a battery is fully charged but a voltmeter is as good as useless. My recommendation is to get a SmartGauge which monitors SoC admirably. You'll need to know when to start charging as well as when stop, and only a SmartGauge can tell you this with any accuracy. An ammeter is handy if funds allow, but by no means essential. If you get both then the SG is best for telling you when you need to charge (i.e. state of charge approaching 50%) and the ammeter tells you most accurately when the charging is finished (tail current falling to about 2% of nominal battery capacity, and stopped falling for 30 minutes).

 

Search this forum for "SmartGauge" for endless threads about what they do and how good they are.

 

Mike surely you know the smartgauge is inaccurate in telling when the batteries are charged to 100% SoC, its charging accuracy is 10%, that basically means that when the smartgauge says the battery is 100% charged it could be only 90% charged. As I believe you have experienced the thing that does the greatest damage to a battery is undercharging it, which results in sulphation of the battery plates and a gradual dropping of the batteries capacity leading to a shortening of the battery's life. A voltmeter used judiciously is capable of telling when to charge a battery. However neither a smartgauge nor a voltmeter is capable of accurately telling one when a battery is 100% charged, that important point to reduce the build up of sulphation. The only thing I know that is capable of doing that within the pocket of the average boater is a good shunt run ammeter being used to measure the tail current and making sure that that current has fallen and steadied at 1% or less than capacity.

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Not sure what you mean by the ammeter route but an ammeter will tell you the amps going into or out of the battery.

 

When charging the amps will be high at first and gradually become lower (voltage does the opposite) when the amps are at 1 to 2% of battery capacity the batteries are 'fully' charged.

 

Now because batteries age it is not always possible to get down to 1 or 2% so when the reading (amps) is low and has not got any lower for a bout an hour the batteries are 'fully' charged.

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If money is available, a Smartguage and a NASA BM1, (or BM2), are probably the ideal combination... about £230 would cover it, and you would probably save that in battery costs over the years.

 

The Smartguage tells you battery state of charge, (IMHO relatively accurate below about 80%, which is what you need to know to decide when to start charging), and the NASA will tell you, amongst other things, instantaneous Amps being drawn by the batteries when charging, in order to identify when the current is low enough to assume the batteries are full, (tail current).

 

A simple ammeter will also tell you current at any time, but the NASA tells you lots more, like Volts, instantaneous Amps being used, nett cumulative Amp Hours used or input, (good for an audit).

 

For example... I have 4 x Trojan T105 batteries giving a nominal 450Ah bank, (I think it's now less than this, and probably around 400-420Ah).

 

Typically, I get to the boat Wednesday evening and the batteries are full, (from Sunday charging and a bit of solar for 3 days). The Smartguage shows 100%, and I zero the NASA cumulative Ah reading.

 

By Saturday evening I've usually used about 220Ah, Smartguage shows about 50% State of Charge, and I fire up the generator to charge the batteries for a couple of hours via an 80A inverter charger. This usually puts about 150Ah back into the batteries.

 

On Sunday, about 5 or 6 hours of charging is needed to see the current fall to about 4A, (roughly 1% of capacity), and it's safe to assume the batteries are full again before I turn everything off and go home.

 

I usually find that I have put about 40Ah back into the batteries than I have used over the long weekend, which must equate to the heat generated during charging.

 

During charging, the Smartguage shows 100% long before the tail current is 2% of capacity, so is clearly not accurate when charging.

 

Hope that makes sense, and is helpful.

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From what the OP said I get the impression he thinks charging 'little and often' is the way to keep the batteries fully charged.

 

"We are really not sure how often we should charge the batteries on a daily basis with general living aboard in mind...."

 

Charging the batteries daily isn't really a Good Idea as charging is not linear. The last 15% of charge takes 50% of the time. Better in my opinion to run them down to about 50% over about a week, then give them one long charge to bring them back up to 100% on say, Saturday. This will take about 8 hours with a suitably-sized charger.

 

More or bigger batteries may be needed to last a week between charges in mid winter. In spring/summer/autumn solar may well be enough.

 

 

 

A voltmeter used judiciously is capable of telling when to charge a battery.

 

 

 

I'm deeply concerned! I've lost power from my one leisure battery and hoping I haven't killed it. I've only been using a couple of led lights and water pump, all quite sparingly so thought that running the engine in neutral every couple of days for an hour should keep them charged. I've been doing this "blind" though as I haven't had a way of monitoring. However the lights went out this morning.

I bought one of these today: http://www.maplin.co.uk/p/maplin-general-purpose-analoguemultimeter-uz82d mainly because my budget is almost non-existent right now. Is this going to help me get some idea of the trouble I'm in?

or should I exchange it for one of these?: http://www.maplin.co.uk/p/battery-and-alternator-checker-fu00a

I will read all the info on how to maintain the batteries but my main issue is to get the lights back on by tomorrow evening

It sounds like running in neutral is not the answer or am I confused?

 

Edited by hackenbush
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I don't think the smartgauge is accurate(!), but it is the most accurate simple SOC indicator available that can simply be read. Other forms of indicator and meter readings can be taken but all need some calculation or experience to determine SOC.

 

I'd also suggest that many people don't get close to 100% SOC for their charging regime.

 

If you can charge by diesel in the morning then perhaps a solar panel will allow the final charge to progress at a slow rate over noon, when some power is usually available even in the winter.

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Mike surely you know the smartgauge is inaccurate in telling when the batteries are charged to 100% SoC, its charging accuracy is 10%, that basically means that when the smartgauge says the battery is 100% charged it could be only 90% charged. As I believe you have experienced the thing that does the greatest damage to a battery is undercharging it, which results in sulphation of the battery plates and a gradual dropping of the batteries capacity leading to a shortening of the battery's life. A voltmeter used judiciously is capable of telling when to charge a battery. However neither a smartgauge nor a voltmeter is capable of accurately telling one when a battery is 100% charged, that important point to reduce the build up of sulphation. The only thing I know that is capable of doing that within the pocket of the average boater is a good shunt run ammeter being used to measure the tail current and making sure that that current has fallen and steadied at 1% or less than capacity.

 

 

I actually said much the same as that in the post of mine you quoted!

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I'm deeply concerned! I've lost power from my one leisure battery and hoping I haven't killed it. I've only been using a couple of led lights and water pump, all quite sparingly so thought that running the engine in neutral every couple of days for an hour should keep them charged. I've been doing this "blind" though as I haven't had a way of monitoring. However the lights went out this morning.

I bought one of these today: http://www.maplin.co.uk/p/maplin-general-purpose-analoguemultimeter-uz82d mainly because my budget is almost non-existent right now. Is this going to help me get some idea of the trouble I'm in?

or should I exchange it for one of these?: http://www.maplin.co.uk/p/battery-and-alternator-checker-fu00a

I will read all the info on how to maintain the batteries but my main issue is to get the lights back on by tomorrow evening

It sounds like running in neutral is not the answer or am I confused?

 

There is no "one size fits all" answer.

Assuming you don't have some fault with your system, then you've used more than you've replaced and that's that.

You might have very moderate usage (sounds like it) but maybe have a very small alternator, which could take ages to put the charge back.

Your battery might be well old & passed it.

You could easily have a fault in your system.

You need a multimeter & enough knowledge to know how & where to use it.

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Richard gives good advice, I would just add that the Victron BVM 600 does a very similar job to the NASA unit. I'm not saying its better but having the choice of two might make getting one easier.

Top Cat

I agree, but the NASA's big display of volts and amps at the same time, readable from across the cabin, makes it better for me.

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