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Battery setup recommendation for short term cruising


Jay88
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Hi all,

After some advice IRT battery options for short term cruising focusing on keeping things simple and low pricing...

 

Currently have the narrowboat on the hardstand since Nov 19 (just before COVID kicked in) and will not be able to get her into the water until mid next year. When stored on the hardstand the batteries were 5-6 years old and pretty knackered (weren't holding a charge for long), so by about mid next year they be approaching 10 years old and I think completely shot. Our plan is to cruise for only 4-5 weeks per year for the next few years (return the boat to hardstand each time) so what are the best battery options (cheapest) to support this type of cruising, noting that in the medium term (about 5 years) we will cruise on the boat for 6 months at a go and when we start this option we're happy to get a heap of solar and brand new batteries accordingly.

 

So my thoughts were that we're probably best off getting maybe just 2-3 cheapo lead acids (maybe 80 GBP each?) for each cruising season and literally 'bining' them at the end of each season. Whilst at the hardstand I can't connect the boat to mains power to keep the batteries charged nor install a small solar panel (ie 60-80W) to keep them topped up because I imagine this system including installation (MPPT etc etc) will be few hundred quid. I'm trying to keep it as simple as possibly in the short term and I can easily buy and install 2-3 cheapo leisure batteries.

 

As a side note, the boat currently has 6 x leisure batteries but during our short cruising season I think (maybe..) 3 x 110AH leisure batteries should keep up with our electrical needs (won't be operating the freezer or dryer and washing machine only when engine is going...) and since we will most likely cruise most days, this will be a good opportunity fully recharge them each day (2 x 80AMP alternators with Sterling B-B charger). Also will probably need to buy a starter battery each season as well...

 

That said, at the end of the cruising season when we put the boat back on the hardstand for 10-11 months, I know the batteries will be 'flat' when we start our next cruising season, but if I simply recharge them what would the life expectancy be? ie will the 110AH battery now be a 80AH battery because we've it's been flat for a few months as it's capacity has been degraded? Is 80AH even close, higher or lower? Any experiences? It would be great to go down this path but I don't want to begin a new cruising season with batteries that may have significantly reduced capacity from the original 110Ah. Maybe buy 130AH batteries?

 

Anyway, if anyone has any further ideas or input, please let me know, or if I've missed any key info

 

Enjoy cruising the cut, can't wait to be back.

 

Cheers

 

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Why can't you install a solar panel for the winter? Is the boat under a roof?

A small solar panel on the boat roof should help keep the batteries charged when the boat is on hard standing. Such a set up would pay for itself if it let a set of batteries last even two summers, let alone more. If you don't like the aesthetics of solar panels on boat roofs, it could be held on with magnets, I'm assuming the roof is steel, and removed when you go cruising.

100W solar panel £62.

Dual battery PWM controller £26. Cheaoer ones are available. MPPT will give you more output from low in the sky winter sun.

Some wire and connectors. Total probably less than £100. Cheaper than two batteries.

 

Jen

Edited by Jen-in-Wellies
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I can install a solar sysytem but I'm trying to keep it as simple as possible...also I'm just not sure what the full cost would be for someone to install a small panel including wiring, mounting, MPPT etc etc system noting we will install a new large solar system (about 800-900W) in 5 years when we start cruising 6 months in each season. 

 

Maybe I should make some enquires and do some comparisons....any good recommendations?

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I agree with Jen. A solar panel and mppt controller will not cost a huge amount and will keep your batteries alive for several years. Fit a VSR so that domestic and start batteries are both charged from a single source.

I would also suggest you need only 1 or 2 domestic batteries initially, but provide space to fit more for the longer term.

And buy the cheapest lead acid batteries you can find. Expensive batteries can be destroyed as quickly as cheap batteries if not properly charged.

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6 minutes ago, Jay88 said:

I can install a solar sysytem but I'm trying to keep it as simple as possible...also I'm just not sure what the full cost would be for someone to install a small panel including wiring, mounting, MPPT etc etc system noting we will install a new large solar system (about 800-900W) in 5 years when we start cruising 6 months in each season. 

 

Maybe I should make some enquires and do some comparisons....any good recommendations?

Where are the batteries located? Under a cruiser/semi trad deck? Inside the cabin> A removable winter only panel could have the wire fed through a window, or through a deck drain, making installation very simple.

 

3 minutes ago, Jay88 said:

Thanks for the advice.

 

As the boat will be on hardstand and pretty much "unsupervised'' for 10-11 months, is there anything that can go wrong when left to it's own devices?

Not really. A small <=100W panel won't be producing much current winter, or summer and the controller will prevent it over charging even if it did.

 

Edited by Jen-in-Wellies
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2 hours ago, Jay88 said:

Hi all,

After some advice IRT battery options for short term cruising focusing on keeping things simple and low pricing...

 

Currently have the narrowboat on the hardstand since Nov 19 (just before COVID kicked in) and will not be able to get her into the water until mid next year. When stored on the hardstand the batteries were 5-6 years old and pretty knackered (weren't holding a charge for long), so by about mid next year they be approaching 10 years old and I think completely shot. Our plan is to cruise for only 4-5 weeks per year for the next few years (return the boat to hardstand each time) so what are the best battery options (cheapest) to support this type of cruising, noting that in the medium term (about 5 years) we will cruise on the boat for 6 months at a go and when we start this option we're happy to get a heap of solar and brand new batteries accordingly.

 

So my thoughts were that we're probably best off getting maybe just 2-3 cheapo lead acids (maybe 80 GBP each?) for each cruising season and literally 'bining' them at the end of each season. Whilst at the hardstand I can't connect the boat to mains power to keep the batteries charged nor install a small solar panel (ie 60-80W) to keep them topped up because I imagine this system including installation (MPPT etc etc) will be few hundred quid. I'm trying to keep it as simple as possibly in the short term and I can easily buy and install 2-3 cheapo leisure batteries.

 

As a side note, the boat currently has 6 x leisure batteries but during our short cruising season I think (maybe..) 3 x 110AH leisure batteries should keep up with our electrical needs (won't be operating the freezer or dryer and washing machine only when engine is going...) and since we will most likely cruise most days, this will be a good opportunity fully recharge them each day (2 x 80AMP alternators with Sterling B-B charger). Also will probably need to buy a starter battery each season as well...

 

That said, at the end of the cruising season when we put the boat back on the hardstand for 10-11 months, I know the batteries will be 'flat' when we start our next cruising season, but if I simply recharge them what would the life expectancy be? ie will the 110AH battery now be a 80AH battery because we've it's been flat for a few months as it's capacity has been degraded? Is 80AH even close, higher or lower? Any experiences? It would be great to go down this path but I don't want to begin a new cruising season with batteries that may have significantly reduced capacity from the original 110Ah. Maybe buy 130AH batteries?

 

Anyway, if anyone has any further ideas or input, please let me know, or if I've missed any key info

 

Enjoy cruising the cut, can't wait to be back.

 

Cheers

 

 

 

I agree that the £80 batteries are probably the best bet for now, until you learn to look after them. Unless you know how to, you will destroy expensive batteries as fast as cheap ones.

 

I also agree that a 40 watt plus panel and controller will pay dividends in longer battery life as long as it is in the sun during the winter.

 

Start batteries spend most of the time fully charged, so tend to last many years. Especially if you do as David Mack says and fit a VSR or stick a jump lead between both bank's positives for the winter period so the solar charges them.

 

I note that you give no information about how you intend to/are monitoring your batteries' state of charge. Without at least an accurate digital voltmeter and ammeter on the domestic bank, you could easily destroy a new set of batteries within a very few months. If you intend to buy or already have a battery monitor, tell us about it because they all tend to tell lies that encourage you to destroy your batteries.

 

I have found that phrases "like we will most likely cruise most days, this will be a good opportunity fully recharge them each day" and "batteries should keep up with our electrical needs" tend to be used by people who don't understand batteries  and their charging needs. Are you intending to cruise for 8 to 12 hours per day? If not there is an excellent chance that you will not be fully charging them so they will gradually sulphate. That is where solar helps in summer by continuing to charge  until dusk.

 

Please read and understand Battery Charging primer and ask about anything you do not understand.

 

Are you aware that the B2B will not provide 160Amps of charging, except for perhaps half an hour or so each morning? From then on the output will gradually drop so over 3 to 4 hours except an average of perhaps 50% of that and any further charging gradually reduces that to eventually (assuming 3 x 110Ah batteries) maybe 6 to 8 amps. This is why battery monitoring is important. If you have not bought the B2B yet, I would suggest that you don't. Spend the money on a decent battery monitor and fitting a VSR and solar. All you will lose with modern alternators is a period of slightly enhanced charge when the B2B runs a slightly higher charging voltage. The VSR will parallel the alternators.

 

Welcome to the confusing world of lead acid batteries!

 

 

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Why not just get a typical car-type 'trickle charge' solar panel - the type that uses 'suckers' in the windscreen, it'll keep your batteries topped up over winter (that's what it is designed for)

 

Around £20 on ebay is all you need.

 

Turn the suckers around, 'sucker it' onto the roof, run the cables down to the batteries, clip-on and jobs-a-good-un.

 

Edit to add :

 

A 10 watt version would probably put enough in to replace the self-discharge, but larger panels are available.

 

5 Watt 10W Solar Panel 12 Volt Trickle Battery Charger for Car Van Caravan Boat | eBay

 

A lead acid battery will discharge at about 4% per week, so a 100Ah battery will need about 4 (or 5) amps putting back in, if you have 3-batteries you need to be able to replace ~15Ah per week.

 

A 25 watt kit is available at £30.

 

Image 131 - 10 Watt 20 Watt 25W Solar Panel 12 Volt 10AH LiFePO4 Battery for Car RV Boat

Edited by Alan de Enfield
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2 minutes ago, Alan de Enfield said:

 

Why not just get a typical car-type 'trickle charge' solar panel - the type that uses 'suckers' in the windscreen, it'll keep your batteries topped up over winter (that's what it is designed for)

 

Around £20 on ebay is all you need.

 

Turn the suckers around, 'sucker it' onto the roof, run the cables down to the batteries, clip-on and jobs-a-good-un.

 

I very much doubt one of those would recharge  a partially discharged bank, even over the whole winter. Also, they are designed for a single 30 to 60Ah battery so may not keep up with the self discharge of a 330Ah bank. I am not saying it won't work, but I feel there is a good chance it won't.

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Many thanks for the replies so far. To answer some questions:

 

1. We are putting the boat on the hardstand as we feel it's safer out of the water for 11 months and we don't need to pay for licence fees over this period which equates to about 900 quid. Craning the boat in and out id about 150 quid each way

2. We can't take the batteries home as we live in a land far far away...in lockdown...

3. Monitoring batteries during cruising is via a Sterling Power Management Panel. I have a reasonable (ish..) knowledge of batteries so during cruising I will let the alternators do their thing to get the batteries back to fully charged whilst cruising. Worst case, if I don't quite get them back to 100% whilst cruising for 4-5 weeks, I'll definatley have them at 100% prior to hardstanding the boat

4. The B2B is alreay installed but not working...I didn't really have any intention to replace it but was looking at potentially getting a 200Ah(ish) alternator for our Izuzu 42 from Four Counties Marine when we start our 6 month cruising option, but I thinks that's another topic...just wanted some simple solutions for the short term cruising period first.

 

So it appears the general advice is to potentially go for a 50Wplus solar that should keep the batteries ''alive'' whilst we're away and help out with charging the batteries whilst cruising the 4-5 weeks. Is there anything I should be aware of so I can 'keep' some of the equipment for the solar install in 5 years (the 800-900w system)?ie go for a MPPT to support the bigger system?

 

Cheers!

Edited by Jay88
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23 minutes ago, Jay88 said:

Is there anything I should be aware of so I can 'keep' some of the equipment for the solar install in 5 years (the 800-900w system)?ie go for a MPPT to support the bigger system?

Make sure the wiring and any holes and cable glands in the roof/sides of the boat are sized for the bigger panels. This will save a lot of hassle and extra cost by not having to replace under sized wires when you go to more/bigger panels later. Use standard MC4 solar connectors to connect the panel to the wiring. If you have a small solar controller fitted, make sure there is space in the location to replace it with a larger MPPT one later. You can always sell the small controller and solar panel when you come to upgrade, but the wiring can stay if it is sized right and designed with upgrading in mind.

Jen

Edited by Jen-in-Wellies
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If you already know this I apologise.

 

Your battery monitor is, as I had feared, an amp hour counter. This applies to virtually all Amp hour counter type meters. Unless you have set them up properly, got an accurate battery capacity and then regularly truly fully charge and resynchronise them the % state of charge will almost certainly be over-estimate the true figure and that leads to an excessive depth of discharge, never fully recharging the batteries and thus sulphation and the need to replace earlier than you would if you had not relied upon the % charge reading.  The size of that lie tends to get larger and larger as time goes on.  

 

An individual lead acid battery will have a different rate of self discharge and also require a different amount of charging to other, and they all vary the amount of "extra" charging they need to get back to 100% charged according to temperature, age and technology. These meters try to compensate for that but using a fiddle factor on the measured Ah into the battery and over the years and across different makes this has been shown to be wrong more often than not. Always overestimating the state of charge. They also are typically set at the factory to resynchronise the selves at a tail current of around 6% of battery capacity. This is nowhere near fully charged, 1 to 2% is more realistic, so again they tend to overestimate the state of charge. Finally, as the batteries sulphate their capacity reduces, but the meter has no way of knowing this unless you tell it the new capacity.

 

Use tail current at 14.2 volts plus to determine when the batteries are fully charged. Go for 1 to 2%.

Use rested voltage to infer the state of charge.

The voltmeter, ammeter and Ah out of the battery will be accurate.

 

So fully charge to that tail current and zero the Ah out scale as soon as you stop the charging.

Next morning use the rested voltage (no electrical load) to infer the state of charge. So is the inferred state of charge is 50% and the Ah out reads 30 Ah the battery capacity is 60Ah.

Now you can input the new capacity, fully charge again by ail current and resynchronise the meter. Then reset the resynchronise value to a tail current to 1% or 2% of battery capacity.

Now your meter will be reasonably truthful for a month or two until you need to reset the battery capacity again. You will soon see how often you have to do that to retain tolerably accurate readings.

 

 

 

Edited by Tony Brooks
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Tony - Well at least the power management panel does tell me the leisure battery volt readings, better than nothing I suppose. It also doesn't proviede a % state of charge, just how many Amps have gone out (goota read the manual a bit more to get a better understanding...)

 

Jen - I'll take on board the comments IRT tips for the solar panel - all great points

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Just now, Jay88 said:

Tony - Well at least the power management panel does tell me the leisure battery volt readings, better than nothing I suppose. It also doesn't proviede a % state of charge, just how many Amps have gone out (goota read the manual a bit more to get a better understanding...)

 

Jen - I'll take on board the comments IRT tips for the solar panel - all great points

 

Not amps out. Amps is an instantaneous value, not cumulative over time, so it is Amp hours have gone out. Don't worry, it is  a very common mistake. Ah out will be accurate, it is Ah in and state of charge that are likely not to be.

 

It will show Amps flowing into or out of the batteries at the moment you look at it. This will also be accurate, and that is where to look for the current towards the end of charging. With 3 x 110Ah batteries, look for between 3 and 6 amps at 14.2 volts plus. Regrettably, the B2B will probably have gone into float long before that point, and the 13.6 to 13.8 volts it probably drops to is no good for using tail currant to assess when fully charged. I don't know if a B2B can be set to stay in absorption mode or can be easily disabled. I suspect it can't.

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6 hours ago, Jay88 said:

Thanks for the advice.

 

As the boat will be on hardstand and pretty much "unsupervised'' for 10-11 months, is there anything that can go wrong when left to it's own devices?

I would buy as cheap as possible and then remove and flog for a tenner when the boat goes on hard standing, next year buy a couple of new ones. I might even forgo a starter battery and just use the two domestics if I knew I wasn't going to hammer them to flat to start the engine each day

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3 hours ago, Jay88 said:

1. We are putting the boat on the hardstand as we feel it's safer out of the water for 11 months and we don't need to pay for licence fees over this period which equates to about 900 quid. Craning the boat in and out id about 150 quid each way

 

Every marina I have known charges for 'storage' , and depending on the size of the boat it can be from £10 per week to £50 per week. Have you confirmed with your proposed storage site that it is free of charge ?

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Strikes me it might be easier to just rent for the month you want to boat.

Or

Buy a boat and lease it to a hire company who will manage it and rent it out whilst you are away.

Or

Do as I do, 400+w of solar on the roof batteries always fully charged when I arrive even if I haven't been near the boat for six months.

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11 hours ago, Tony Brooks said:

Use tail current at 14.2 volts plus to determine when the batteries are fully charged. Go for 1 to 2%.

 

I have always thought that it was tail current at 14.6v to determine when the batteries are fully charged - have I got that wrong as well?!

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39 minutes ago, Col_T said:

 

I have always thought that it was tail current at 14.6v to determine when the batteries are fully charged - have I got that wrong as well?!

 

Lead acid batteries are never 'fully charged'. One can always squeeze a little bit more in.

 

Lithium on the other hand, should never be charged to 100% and held there for any significant time. 

 

 

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10 hours ago, Col_T said:

 

I have always thought that it was tail current at 14.6v to determine when the batteries are fully charged - have I got that wrong as well?!

No, any voltage above maybe 14.2 will do, it's only a rule of thumb and I suspect the majority of boat  alternators have a 14.2 to 14.4 volt regulator. It seems to me the 14.6 only became more common with the introduction of lead calcium batteries that will accept a slightly higher charging voltage before starting to gas. The vital thing is not to do it when a charger, solar, or B2B has gone into float. That will be far too low.

Edited by Tony Brooks
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