Batteries and power system????

[fabius]

Hi folks,

I think this is my first post. I normally trawl through the forum archive for the answers to my questions (teadious but worthwhile) but in this case there is too much opinion, options and technobable for me to make any comfortable decisions.

 

I have a 60x12 widebeam on order and i'll be fitting it out from sailaway myself. The one thing i'm really having trouble making progress on is the power system. At the moment i'm in the planning stage but have a good idea what i'll be doing with the rest of the boat systems but the power and batteries is just causing me confusion.

 

As I said the boat is 60x12 widebeam and it will be used as a live aboard with little or no shore power available. There will be two people living on board and there will be the usual drain on the power from domestic items, lights, fridge, pumps. tv. laptop etc. nothing out of the ordinary. I'm planning on having 12v and 240v keeping the built in systems 12v to save on the inverter and the 240v for everything else. The principle i have followed generally with the rest of the boat system plans has been no waste.I've done this in the layout, heating and cooking systems, toilet(compost) and would like to do it with the power too. As such i would like to be able to charge off the main engine when it's running, the genny when it's not, shorepower where available and solar and wind panals would be nice in the future but i have no idea whats involved in this.What I have so far is...

 

I have a lot of electrician friends to help assemble any system i decide upon, but they are the kind who scratch their heads when you mention batteries.

 

I have a 2.5kw petrol(not ideal i know) generator with 12v and 240v feeds.

 

The engine will be a Beta 75 with the regular altenator for the starter battery.

 

The budget is limited(very) and I'd like to make use of the genny i already have if that is practical i'm aware of the safety implications of petrol

 

The questions i suppose are..

What sort of batteries do i need and how many for a live aboard where we won't be listening to the genny all the time. We won't be regular cruisers.

 

is it possible to have multipule sources feeding the batteries at once. If so how many and are there restrictions.

 

Are there blueprints/ plans anywhere online for a system like this, the electrictian friends seem quite keen on these.

 

Finally, how much and where??

 

 

If you've read this far,

Thank you very much.

Fabius.

 

p.s. please keep the tech talk to a minimum or explain it if you have to thanks again.

[WotEver]

Before anyone can really answer this question you'll have to do some kind of - at least minimal - power audit. To know how to supply your power we must first know how much power you'll require.

 

A power audit doesn't have to be complicated, but it is somewhat tedious. You have to consider your lifestyle, and when and where you'd like to switch lights on, and for how long. How you'll heat the water for a cuppa (presumably gas, but you may have other ideas). Whether you'll have a refrigerator, a TV, radio and so forth.

 

So for every piece of electrical equipment you intend to have on the boat you need to know roughly how much power it will require, then estimate how long it will be switched on. Refrigerators tend to be estimated at half their working power, so a 5A draw would be estimated at 2.5A, but everything else depends on you. For instance, you might wish to have 20 lamps lit every night for 6 hours, or you might be happy with a single oil lamp - see how much difference that would make to your power requierements?

 

Yes, there are charge controllers that can have multiple sources, but the ground work must be done first, before we can go much further.

 

Tony

[churchward]

From the standpoint of multiple charging sources you may want to consider the smartgauge/smartbank set-up. Look here for info. Simple to install too.

 

http://www.smartgauge.co.uk/

 

There is also a wealth of knowledge shared in the technical pages and articles on that site worth looking at.

 

I agree with Wotever's point about power audit too.

Edited February 4, 2010 by churchward

[Robbo]

I have a 2.5kw petrol(not ideal i know) generator with 12v and 240v feeds.

 

If this can't be built in safely to the boat, so you don't need to towpath it everytime you use it, I would seriously look at replacing for a diesel generator, if you can't afford now make the presumption you'll want one and leave space for it.

[fabius]

ok power audit it is then.... how?

 

I understand the principle of estimating useage over time but this is where i get lost. What info do i use, 1w led for 1 hr = ????. then there's the 5amp fridge on all day = ???. Do i work in amps, ahr, watts etc. Do i just get the information from the product i want to use or are there general rates for say a t.v.

 

Cooking will be Gas

Heating will be oil.

Lighting will be led

the fridge and the t.v. i would imagine will be the biggest draws. the laptop i'm sure could be charged in work.

 

Also a friend told me that the bigger the battery bank the longer it will last because it will not drain as easily thus reducing the number of deep cycles it is likely to go through. Is there any truth in this?

 

thanks again guys

[paulcatchpole]

As such i would like to be able to charge off the main engine when it's running, the genny when it's not, shorepower where available and solar and wind panals would be nice in the future but i have no idea whats involved in this.What I have so far is...

...

I have a 2.5kw petrol(not ideal i know) generator with 12v and 240v feeds.

 

For avoidance of confusion, I wonder if you're intending the generator's 12v feed to charge the main battery banks.

 

If so, they're usually limited to a few amps at best and hence won't be man enough for the job. It'll need a mains charger running from the generator's 230v output.

 

PC

[fabius]

If this can't be built in safely to the boat, so you don't need to towpath it everytime you use it, I would seriously look at replacing for a diesel generator, if you can't afford now make the presumption you'll want one and leave space for it.

 

 

Thank's for the post. I'm not mad on tow pathing it (it's very heavy) and it's not very nice to do either so i was thinking of mounting it internal and pulling the fuel tank off and placing it externally. I'm not new to boats and have some smarts about me as to the likely if not inevitable outcomes when petrol becomes a regular feature in your life but for the moment the petrol one is what i have and i'd like to use it if possible.

 

I'm aware the petrol one is not a long term solution but this leads me to the question, Internal diesel genny or altinator off the main engine??? noise, reliability, cost, efficiency???

 

If i was to towpath the petrol should it be ran in through the shore power at 240v or should it go direct to the charger at 12v???? or do you need two shore power one 12v and one 240v??

 

 

Sooooo Mannny Questions

 

For avoidance of confusion, I wonder if you're intending the generator's 12v feed to charge the main battery banks.

 

If so, they're usually limited to a few amps at best and hence won't be man enough for the job. It'll need a mains charger running from the generator's 230v output.

 

PC

So does this mean the genny would be best served feeding in through the shore power at 230v.??? It's a regular stand alone genny you'd find on any building site, the 12v connectors on it are quite small all right. Is this likely to effect the efficiency much??

[paulcatchpole]

So does this mean the genny would be best served feeding in through the shore power at 230v.??? It's a regular stand alone genny you'd find on any building site, the 12v connectors on it are quite small all right. Is this likely to effect the efficiency much??

 

Aye, that's what most do - plug a large mains charger into a socket onboard the boat (or FCU or whatever takes your fancy) then when on shoreline, the shoreline cable plugs into the boat's external inlet - or when using the generator, plug it in in the same place.

 

Obviously if you build the generator into the boat, you may end up making different connection arrangements.

 

PC

[ditchcrawler]

ok power audit it is then.... how?

 

I understand the principle of estimating useage over time but this is where i get lost. What info do i use, 1w led for 1 hr = ????. then there's the 5amp fridge on all day = ???. Do i work in amps, ahr, watts etc. Do i just get the information from the product i want to use or are there general rates for say a t.v.

 

Cooking will be Gas

Heating will be oil.

Lighting will be led

the fridge and the t.v. i would imagine will be the biggest draws. the laptop i'm sure could be charged in work.

 

Also a friend told me that the bigger the battery bank the longer it will last because it will not drain as easily thus reducing the number of deep cycles it is likely to go through. Is there any truth in this?

 

thanks again guys

Having a read at http://www.tb-training.co.uk/index.htm may help as well

[WotEver]

ok power audit it is then.... how?

 

I understand the principle of estimating useage over time but this is where i get lost. What info do i use, 1w led for 1 hr = ????. then there's the 5amp fridge on all day = ???. Do i work in amps, ahr, watts etc. Do i just get the information from the product i want to use or are there general rates for say a t.v.

Ditchcrawler has already given you the link to Tony's site, but I appreciate that's a LOT of reading, much of which might be beyond you, judging from what you've already said. The page that specifically describes a power audit is here. (Edit to say it's about half-way down that page. Scroll until you see the 'Power Audit' heading.) Every TV, every Fridge etc are different, so you need to take a look at the plate on the back of the equipment (or read the specs online), for let's say the TV to see what the draw for YOUR TV will be.

 

Also a friend told me that the bigger the battery bank the longer it will last because it will not drain as easily thus reducing the number of deep cycles it is likely to go through. Is there any truth in this?

Absolutely. The bigger the battery bank, the more power it can deliver, that's simple and obvious. However, what may not be so obvious is that the bigger the battery bank the longer it takes to recharge, and the bigger the recharge source needs to be. Whatever power you pull from a battery has to be replaced, and due to inefficiencies you replace more than you take out, plus it takes MUCH, MUCH longer to recharge than most folk initially expect it to.

 

If you really want to install a petrol genny then make sure you read and re-read the BSS requirements. Having petrol on board is a nasty idea.

 

And as others have said, the 12V output from the genny is not suitable for charging your battery bank.

 

Tony

Edited February 5, 2010 by WotEver

[steelaway]

ok power audit it is then.... how?

 

I understand the principle of estimating useage over time but this is where i get lost. What info do i use, 1w led for 1 hr = ????. then there's the 5amp fridge on all day = ???. Do i work in amps, ahr, watts etc. Do i just get the information from the product i want to use or are there general rates for say a t.v.

 

Cooking will be Gas

Heating will be oil.

Lighting will be led

the fridge and the t.v. i would imagine will be the biggest draws. the laptop i'm sure could be charged in work.

 

Also a friend told me that the bigger the battery bank the longer it will last because it will not drain as easily thus reducing the number of deep cycles it is likely to go through. Is there any truth in this?

 

thanks again guys

 

 

Hi

 

Do you intend having a washing mashine/dishwasher on your boat.

With a selection of equipment you can have it all but it will cost.

 

IMHO.

Every day

Run engine for one hour to heat water and charge the battery's

Every other day

Engine mounted 240v generator. Run engine for two hours to charge battery's / heat water/ run washing machine.

You will need a 2kw inverter and at least 750A battery bank.

To minimise engine running you could install a wind generator and/or solar panels to charge battery's.

To use a 240V petrol generator you will need a minimum 30-40A battery charger to have any significant charge to the battery's.

It will probably cost more to charge the battery's in petrol than it would in diesel, if you are not using the 240v -

Without the added benefits of high charging rates and hot water in running your boat engine.

I would also consider down sizeing the engine, There would be very rare situations where you could need 75HP.

 

Alex

[deletedaccount]

If you've only got a 50amp or so charger then the generator will take twice as long to charge your batteries as a decent sized alternator, burning expensive petrol as it goes. You'd need to ruin it for two-four hours a day or so.

Edited February 5, 2010 by deletedaccount

[blackrose]

Thank's for the post. I'm not mad on tow pathing it (it's very heavy) and it's not very nice to do either so i was thinking of mounting it internal and pulling the fuel tank off and placing it externally. I'm not new to boats and have some smarts about me as to the likely if not inevitable outcomes when petrol becomes a regular feature in your life but for the moment the petrol one is what i have and i'd like to use it if possible.

 

Forget it. You can't install a petrol generator even with the tank mounted externally. It's unsafe and will not pass the BSS, not to mention the fact that if it's air-cooled then it will probably overheat in any enclosed space.

 

You can certainly use your current generator, but don't try to install it as a fixed system.

 

The best generator options are either a portable petrol generator like the popular Honda EU20i used with proper safety precautions, or a proper built in diesel generator. Unfortunately the latter are hideously expensive.

Edited February 5, 2010 by blackrose

[blackrose]

If you've only got a 50amp or so charger then the generator will take twice as long to charge your batteries as a decent sized alternator, burning expensive petrol as it goes. You'd need to ruin it for two-four hours a day or so.

 

On the other hand, one has to weigh this against running up all those extra and unnecessary hours on your expensive engine.

 

I agree a 50 amp charger is a bit on the low side (depending on the size of the battery bank). I run a 70 amp charger from my petrol generator to charge 405 a/h bank and I prefer this as it's much quieter and produces fewer vibrations on the boat than my engine.

[fabius]

thanks everyone for the contributions.

 

Here is where i am so far.... with the power generation al least.

 

1.The petrol genny, used externally only, fed through the shoreline in 240v in principle will charge the batteries provided that the ampage on the charger is high enough. With lower amp charger this will not be practical because it will have to run for far too long each day and will cost a fortune in petrol. Correct???

 

2.Of the other options an internal diesel genny is very expensive initially but cheaper to run and safer??? correct?/

 

3.An altenator is a cheaper option but puts wear and tear on the main engine which is very expensive to replace but charges the batteries when under way.

 

More questions so...

I'm getting the idea that you are better spreading your eggs through a few baskets. Would i be best to continue with the external genny idea (with high enough charger ampage of course) and also get the mountings for an altenator installed so i can put it in when the cash is to hand? I could later (when the petrol one dies, or the petrol price kills me) add a diesel genny internally to the mix but for the moment cash is not in abundance. Does this seem like a reasonable way forward?? If so....How big should the altinator be?? Does it depend on the size of the engine?

[fabius]

I would also consider down sizeing the engine, There would be very rare situations where you could need 75HP.

 

Alex

 

I went with a 75hp upgrade from a 55hp (or something in that region because i'll be using it on rivers too and was worried that it will not make any headway up stream??? I could be way off as my backround is in marine craft and I don't have a huge amount of experience of displacement craft at that. 60x12 wide beam, I don't want to be screwing the engine the whole time to get anywhere.

[Lady Muck]

I've always thought that you should always have more than one way to do things on a boat - to have the choice between genny and engine to charge the batteries is a good thing IMO.

[smileypete]

More questions so...

I'm getting the idea that you are better spreading your eggs through a few baskets. Would i be best to continue with the external genny idea (with high enough charger ampage of course) and also get the mountings for an altenator installed so i can put it in when the cash is to hand? I could later (when the petrol one dies, or the petrol price kills me) add a diesel genny internally to the mix but for the moment cash is not in abundance. Does this seem like a reasonable way forward?? If so....How big should the altinator be?? Does it depend on the size of the engine?

I'd provide battery mountings and cabling that can be used for different types of batteries, and each type in different numbers.

 

Eg 12V 110Ah leisure, or 12V 135Ah leisure, or 6V 225Ah semi traction in pairs.

 

Then one of the above in numbers of 2 or 4 or 6 or 8.

 

cheers,

Pete.

[steelaway]

I went with a 75hp upgrade from a 55hp (or something in that region because i'll be using it on rivers too and was worried that it will not make any headway up stream??? I could be way off as my backround is in marine craft and I don't have a huge amount of experience of displacement craft at that. 60x12 wide beam, I don't want to be screwing the engine the whole time to get anywhere.

 

 

Hi

 

I think that 55hp will be more than enough, even on rivers.

Going down stream on a river will not require anything like 75hp or even upsteam on most rivers and you wouldn't want to go against any tides.

Having 75hp on a canal will damage the engine more than giving it a good thrashing from time time on a river.

I could be wrong and even accounting for the extra weight - wide beams always seem to glide along better the narrowbeams

You can have a 240v generator fitted to your new engine when you buy it - £4,000?

Most modern engines now come with two 12v alternators amounting to 150a on average.

 

Alex

[fabius]

Hi

 

I think that 55hp will be more than enough, even on rivers.

Going down stream on a river will not require anything like 75hp or even upsteam on most rivers and you wouldn't want to go against any tides.

Having 75hp on a canal will damage the engine more than giving it a good thrashing from time time on a river.

I could be wrong and even accounting for the extra weight - wide beams always seem to glide along better the narrowbeams

You can have a 240v generator fitted to your new engine when you buy it - £4,000?

Most modern engines now come with two 12v alternators amounting to 150a on average.

 

Alex

It needs another look so. I'd be happy to keep the £1500 for the upgrade in my pocket. It would go a long way towards other costs and the smaller engine would be cheaper to run.

 

Any other opinions on the engine size??? Beta 55 or 75 on 60x12 widebeam keeping in mind it will have to be good for rivers and lakes.

 

Anyone know if there are two alternators on Beta engines as Steelaway was saying. Would these be sufficient to charge a large bank??

[Nickhlx]

Our recent ( year old) Beta 43 came with a 175 amp and a 45 amp alternator - the VE panel has shown an initial charge of over 200 amps when started from the low state of charge of 60% (!) I am very satisfied with that although the alternator belt does squeal a touch at low revs but by 1500 rpm its sounding OK.

 

[ Note to myself ... get a spare alternator drive belt !! ]

 

Nick

[fabius]

Ditchcrawler has already given you the link to Tony's site, but I appreciate that's a LOT of reading, much of which might be beyond you, judging from what you've already said. The page that specifically describes a power audit is here. (Edit to say it's about half-way down that page. Scroll until you see the 'Power Audit' heading.) Every TV, every Fridge etc are different, so you need to take a look at the plate on the back of the equipment (or read the specs online), for let's say the TV to see what the draw for YOUR TV will be.

 

 

Absolutely. The bigger the battery bank, the more power it can deliver, that's simple and obvious. However, what may not be so obvious is that the bigger the battery bank the longer it takes to recharge, and the bigger the recharge source needs to be. Whatever power you pull from a battery has to be replaced, and due to inefficiencies you replace more than you take out, plus it takes MUCH, MUCH longer to recharge than most folk initially expect it to.

 

If you really want to install a petrol genny then make sure you read and re-read the BSS requirements. Having petrol on board is a nasty idea.

 

And as others have said, the 12V output from the genny is not suitable for charging your battery bank.

 

Tony

 

Beyond me??? Well I never !!!!

 

just kidding, actually i've just read the entire thing and the mud is beginning to clear and it's revealing more questions than answers. I have enough of it in though to start this power audit. Just one more question that the site doesn't explain(or i missed it). Whats the relationship between amps and watts?? Specifically i mean if bulbs are in watts why is the fridge in amps and how do i account for this.

 

Cheers

 

P.S. actually let me predict my next question and ask you to give me the formula for working it out too.... Maybe an example too.. Or would that be pushing it..

[Justme]

Thats easy.

 

Watts is volts times amps.

 

So 12.8v at 6 amps = 76.8 watts

 

Now run that for an hour & its 76.8wh or 6ah

 

ah tend to ignore the volts but as we use (when discharging) a narrow range from 12.2 to 12.8 its not that important.

 

When charging the range increases to 12.2 to 14.6 ish so will make more difference.

 

We really should work in watts for every thing but we dont.

[Roger Gunkel]

It needs another look so. I'd be happy to keep the £1500 for the upgrade in my pocket. It would go a long way towards other costs and the smaller engine would be cheaper to run.

 

Any other opinions on the engine size??? Beta 55 or 75 on 60x12 widebeam keeping in mind it will have to be good for rivers and lakes.

 

A diesel engine needs to be pushed reasonably hard for maximum efficiency and economy. On the inland waterways where most of the water is still or slow moving, you would probably find that 10hp would push it along quite happily and at amazing low fuel consumption. However, as your boat will have a lot of mass, I'm not suggesting you go to 10hp, it will need more power for emergency stopping or pushing through a faster flowing current on occasions. There are formulae for working it all out based on displacement, waterline length etc, but it needs someone with more knowledge than me to help with that. As most cruising will be done at very low revs, perhaps 1000-1200 rpm, 75hp would be a waste of money, power and efficiency IMHO. If you are only going to be on faster waters occasionally, even 45hp might well be sufficient, as it would be very happy to be pushed hard if needed. I would certainly try to get someone to do the maths for you.

 

I understand where you are coming from with a salty water background, as there is a need to push through fast tidal flows, large waves etc. I think the norm is for 50% above the expected required maximum power, as a safety margin. I was reading an interesting article a few moths ago about a seagoing boat with a hybrid system. The boat was about 45ft, with a 10hp equivalent electric drive which gave a reasonable cruising speed under calm conditions and for harbour work. It was in tandem with a 75hp diesel, which was used when conditions needed it or a higher speed was required. It also had a high output alternator for charging the batteries.

 

Roger

[fabius]

Thats easy.

 

Watts is volts times amps.

 

So 12.8v at 6 amps = 76.8 watts

 

Now run that for an hour & its 76.8wh or 6ah

 

ah tend to ignore the volts but as we use (when discharging) a narrow range from 12.2 to 12.8 its not that important.

 

When charging the range increases to 12.2 to 14.6 ish so will make more difference.

 

We really should work in watts for every thing but we dont.

 

So if i'm factoring in 240v items does that mean that the amp's would be 20 times(ish) less than if they were 12 v.

 

i.e........... a 12.8v item at 6amps = 76.8 watts

 

the exact same same item 240v would be 240v x 0.32amps =76,8watts. ???? (Plus whatever power is lost in the inverter)

 

 

THE MUD IS CLEARING...Here was me beginning to think that you somehow got something for nothing using 12v... Bloody Newton and his stupid laws!