How do you calculate leisure battery needs please?

[OliveOyl]

My little boat is a 30 footer. She has no inverter/hook-up to mains, and I would like to toddle off soon and do some exploring She has.a new starter battery, and a bank of 3 leisure batteries which have been left for the best part of year, and I am about to accept that they have had it, (have topped up cells, put bataid tabs in - yes, have been told not to bother). Batteries charge  when engine running, and provide some power for a short time afterwards, but as predicted, then fail. Have had on slow charge and they read about 10.1 v after boat has been left for a couple of days (it was 4!).

Someone said they wondered if I needed three batteries for such a small boat, so  my question is - how do you calculate how many batteries you need, and of what capacity please?

The power is needed for the following:-

Lights

Computer

Water pump

Charging mobile phone

Hairdryer (not daily)

 

I have a 12v TV on boat - not currently working - but would liike to include it in my list of power needs for the future.

 

Any advice/guidance much appreciated.

 

[nicknorman]

Generally you want to avoid discharging batteries below 50% charged. Since batteries tend to lose capacity as they age, it might be sensible to start with the presumption to not go below say 70%. You have given us a clue to the daily power usage but the other key piece of information is how long you want the batteries to last between charges. One day? 2/3rds day (the other 1/3rd spent cruising), two days? Etc.

You also need to bear in mind that however big the batteries are, you need to be able to replace the charge taken out using the engine alternator or whatever. So for example there would be no point in having huge batteries to go with a large power demand, but no realistic means to put that energy back in again.

As to your power needs, you mention lights. LED or incandescent? You mention a computer. Is it a laptop, what sort of age and how many hours use a day? How many hours a day of TV? If you want to run a hairdryer you presumably have an inverter, if so what make/model or power output? Whilst the total energy used by a hairdryer isn't that much because it's not on for long (unless you have enormous hair!) the batteries have to be able to cope with the high peak demand.

Anyway, at first guess I'd say your 3 x 110AH batteries are about right. If you want me to "show my working" you'll have to answer all the questions above!

[rusty69]

You will find some useful info on Tonys excellent website:-

 

http://www.tb-training.co.uk/MarineE05.html#The power audit

 

Show Tony your own Power audit of Friday.He may award you a gold star!

Edited February 28, 2017 by rusty69

[ditchcrawler]

I had a new Tashiba  laptop at Christmas and its power consumption is much less than my old Acer, the charger is only half the size, the battery life 4 times as long and the time to charge about the same. This makes a big difference to me as it will now run all evening without a charge and charge easily during the days cruise.

I think the OP said no inverter so not sure how she will power the hair dryer.

[OliveOyl]

Oh Lord NN, I thought peeps would just reply things like, "you only need 2 x 110ah" or "you need 3 x 85ah" 

 

I'm pretty sure I don't have an inverter. Previous owner left me a mini 12v hairdryer which plugs into a lighter socket next to the bed,

Re hours of cruising - maybe cruise 3hrs, stop for lu ch, cruise 3/4/5/depending on where I want to get to? Evening of laptop (old Toshiba) bit of TV maybe an hour?

 

I have no idea what an incandescent light is  -I thought it only applied to fireworks  My lights are diddy recessed things (some of which have gone) and I have no idea how to get them out so I can go and buy replacements.

I don't know what ah my current batts are, will look next time I go to boat.

Thanks Rusty

[bizzard]

8 minutes ago, OliveOyl said:

Oh Lord NN, I thought peeps would just reply things like, "you only need 2 x 110ah" or "you need 3 x 85ah" 

 

I'm pretty sure I don't have an inverter. Previous owner left me a mini 12v hairdryer which plugs into a lighter socket next to the bed,

Re hours of cruising - maybe cruise 3hrs, stop for lu ch, cruise 3/4/5/depending on where I want to get to? Evening of laptop (old Toshiba) bit of TV maybe an hour?

 

I have no idea what an incandescent light is  -I thought it only applied to fireworks  My lights are diddy recessed things (some of which have gone) and I have no idea how to get them out so I can go and buy replacements.

I don't know what ah my current batts are, will look next time I go to boat.

Thanks Rusty

Your recessed lights are probably Halogen, can you see a single little bulb in it. If so they are probable held in with a circular wire clip. If so they are directly interchangeable LED light units which will fit. Check them out at ''Bedazzled'' website. If its an old Toshiba Satellite 300 laptop like mine it'll kill a small battery bank pretty quickly. I use a Lenovo notebook when I'm off the mains.

[nicknorman]

Ah, ok 12v hairdryer, makes things a little easier. An incandescent light bulb is the old type with a filament that got white hot, like the bulbs you had in your house until about 10 years ago. They use electricity to make 90% heat and 10% light - so are pretty inefficient! Each small boat-sized bulb uses 1 or 2 amps and so if you have several on, the power drain is significant. If you replace the bulbs with LED versions they use about 1/5th the power for the same amount of light.

old laptop, probably a fair bit of power.

So I'd still say 3 domestic batteries (around 110AH x 3) but if funds are tight you might get away with 2 if you change to LED and don't use the laptop too much. You could perhaps use the hairdryer whilst the engine is running to avoid using the batteries to power it.

How do you intend to monitor when your batteries need charging? If you just use the batteries until the lights go dim, they won't last long.

Edited February 28, 2017 by nicknorman

[Tony Brooks]

I can explain all this on Friday - and see if we can get a lamp out.

We can give you a guestimate but it is unlikely to take you use into account or your charging so there is every chance you will end up ruining even more batteries.

You need to decide on the worst case use for both discharging and charging. So that's probably discharge during dark winter months and is the battery charge is big enough to cover that when you are not moving then how long you cruise for on a short day - also the size of the alternator.

As an example I suspect that your son's batteries never receive enough charge. That probably means battery charge no high enough output - but we will see.

I have 330Ah worth of batteries running pretty much what you do plus an electric fridge. It used to be 220Ah. I monitor my batteries several times a day (I will explain how when I see you) and find that I have to run the engine - 70 amp alternator - every day (no mains charger) for several hours. However I do not live on it so when we are at home a 60watt solar panel has a chance to fully charge the batteries over a week or so.  There is now way I can say 220 Ah, 330Ah, or 440Ah is correct for you. I would be far more interested in ensuring your charging system can put back what you have taken out each day.

[Graham Davis]

Throw the 12v hairdrier away as one of the first things to do. They are useless and eat batteries.

[ditchcrawler]

33 minutes ago, Tony Brooks said:

I can explain all this on Friday - and see if we can get a lamp out.

We can give you a guestimate but it is unlikely to take you use into account or your charging so there is every chance you will end up ruining even more batteries.

You need to decide on the worst case use for both discharging and charging. So that's probably discharge during dark winter months and is the battery charge is big enough to cover that when you are not moving then how long you cruise for on a short day - also the size of the alternator.

As an example I suspect that your son's batteries never receive enough charge. That probably means battery charge no high enough output - but we will see.

I have 330Ah worth of batteries running pretty much what you do plus an electric fridge. It used to be 220Ah. I monitor my batteries several times a day (I will explain how when I see you) and find that I have to run the engine - 70 amp alternator - every day (no mains charger) for several hours. However I do not live on it so when we are at home a 60watt solar panel has a chance to fully charge the batteries over a week or so.  There is now way I can say 220 Ah, 330Ah, or 440Ah is correct for you. I would be far more interested in ensuring your charging system can put back what you have taken out each day.

Is this the same person you are seeing about her son, I am getting very confused.

[Tony Brooks]

2 minutes ago, ditchcrawler said:

Is this the same person you are seeing about her son, I am getting very confused.

Yes, at least I think so.

[bizzard]

My mum used to stand on a box holding her head over the gas stove to dry her hair. She never caught light. Folk used their noddle in those days. After a while my dad bought her a Pifco electric hair dryer which was so heavy he had to do it for her with both hands. When there was no one about to do it she would be back on the box hanging over the stove.

[WotEver]

7 minutes ago, ditchcrawler said:

Is this the same person you are seeing about her son, I am getting very confused.

Yes

[Naughty Cal]

10 minutes ago, Graham Davis said:

Throw the 12v hairdrier away as one of the first things to do. They are useless and eat batteries.

Agreed.

They are bloody useless anyway.

Let the hair dry naturally.

[mross]

9 minutes ago, Graham Davis said:

Throw the 12v hairdrier away as one of the first things to do. They are useless and eat batteries.

My 2,000W hairdryer uses about 14Ah in 5 minutes.  Hardly going to destroy batteries.  And 12V models use a lot less power.  

[Chewbacka]

17 minutes ago, mross said:

My 2,000W hairdryer uses about 14Ah in 5 minutes.  Hardly going to destroy batteries.  And 12V models use a lot less power.  

12v hairdryer uses a lot less power because it is not very hot and so will take forever to dry your hair.  My wife's view is they make a noise but don't do much else.

This could explain why a fair few boating 'people' have shortish hair - easy to naturally dry.

[OliveOyl]

To clarify.

I have a boat - 30ft - moored in Staffordshire, about which I asked for guidance today, on how much power I need from leisure batteries, as mine appear to be kn**ered.

Tony is very kindly going to meet me where the other boat is moored (NOT Staffordshire) later this week, and help me to identify why my son's single leisure battery is constantly dying, even though he seems to use virtually no power and has it on continuous charge as advised by previous owner/other boaters nearby.

 

As for the haridryer, yep, it seems to blow less warm air out that I can with pursed lips, so I have just had my hair cut quite short 

[OliveOyl]

Thanks Bizz

 

Just been on bedazzled web site, I think they are cabinet recessed, but how do you get them out???

 

I remember stopping at Bedazzled's stand when I went to Crick Boat Show as I thought perhaos I could pick up some spare bulbs, but they told me  bulbs won't have gone, it'll be the wiring.

[bizzard]

The heat from a 12v hairdryer can be enhanced by blowing it first past a hot water bottle on edge, filled with boiling hot water.

[bizzard]

2 minutes ago, OliveOyl said:

Thanks Bizz

 

Just been on bedazzled web site, I think they are cabinet recessed, but how do you get them out???

 

I remember stopping at Bedazzled's stand when I went to Crick Boat Show as I thought perhaos I could pick up some spare bulbs, but they told me  bulbs won't have gone, it'll be the wiring.

I thought they were in the ceiling not in a cabinet. In the ceiling with a metal bezzel surround. If so there should be a wee circular wire clip which can be squeezed with the finger tips to release the light unit, which should drop down on its wires.

[OliveOyl]

They are in the ceiling, I just thought cabinet lights was the name! (that's wot it said on bedazzled website).

 

I can't see anyway to get them out on my boat or my son's.

 

I think I will take pics so you know for definite which sort they are.

[bizzard]

6 minutes ago, OliveOyl said:

They are in the ceiling, I just thought cabinet lights was the name! (that's wot it said on bedazzled website).

 

I can't see anyway to get them out on my boat or my son's.

 

I think I will take pics so you know for definite which sort they are.

WWwwwwait a minute and I'll stick a pic on here of mine to see if its similar.

Edited February 28, 2017 by bizzard
Can you see the ends of the little clips

[system 4-50]

Scrap the hairdryer. Buy a pulpit, I think that is the correct term. Then go and see "Titanic". Remember to spread your arms wide and your hair will dry in no time. But you will need someone else to steer the boat, unless you are using the TW method. Don't do it when there is ice/fog on the water.

[OliveOyl]

Thanks Bizz

I think I need to go to my boat tomorrow as memory is a wonderfully infallible thing!

[rusty69]

4 minutes ago, OliveOyl said:

They are in the ceiling, I just thought cabinet lights was the name! (that's wot it said on bedazzled website).

 

I can't see anyway to get them out on my boat or my son's.

 

I think I will take pics so you know for definite which sort they are.

Suspect you prize the lens off and bulb, if two pronged style will pull out.