batteries

[Justin]

Just thought i would throw this question out there to test the consensus!

 

What is the best method of finding out what the state of charge the batteries are in. I have seen the all singing all dancing sterling management panel £200, is their a cheaper way of knoing when my four 135 amp batts are running low?

 

thanks for the advice

 

Justin

[ChrisPy]

Just thought i would throw this question out there to test the consensus!

 

What is the best method of finding out what the state of charge the batteries are in. I have seen the all singing all dancing sterling management panel £200, is their a cheaper way of knoing when my four 135 amp batts are running low?

 

thanks for the advice

 

Justin

20618[/snapback]

the answer to your question as stated is simple - the state of charge is best identified accurately by a hydrometer, or remotely and less accurately by a voltmeter when off load. Cheap and simple.

 

if you need to know more than just the state of charge you are getting into controversial debating ground - black boxes of tricks and as many viewpoints as there are experts - watch this space.

Edited May 25, 2005 by chris polley

[gringogordo]

the answer to your question as stated is simple - the state of charge is best identified accurately by a hygrometer, or remotely and less accurately by a voltmeter when off load.  Cheap and simple.

 

if you need more than just the state of charge you are getting into controversial debating ground - black boxes of tricks end as many viewpoints as there are experts - watch this space. 

20621[/snapback]

 

I don't really know about the expensive alternatives but my simple voltmeter has provided me with as much information as I've ever needed. The only thing that I would like (but wouldn't be prepared to pay much for!) is a device which tells me (in a more straightforward fashion than the 3 lights on my sterling charger) how well the batteries are being charged during charging and how close they are to being fully charged during the charging process. But like this is a nice to have that I would accept as a gift (!) but probably not pay for.

 

Cheers,

 

Ben.

[bottle]

Gringogordo

 

You are looking for an Amp metre.

 

Try auto (car) shops used to be sold as add ons or even boot sales/ scap yards.

Not fitted to modern cars but most classics have them.

Look on E-Bay you never know.

Then come back here and someone will know how to fit it.

[gringogordo]

I don't really know about the expensive alternatives but my simple voltmeter has provided me with as much information as I've ever needed.  The only thing that I would like (but wouldn't be prepared to pay much for!) is a device which tells me (in a more straightforward fashion than the 3 lights on my sterling charger) how well the batteries are being charged during charging and how close they are to being fully charged during the charging process.  But like this is a nice to have that I would accept as a gift (!) but probably not pay for.

 

Cheers,

 

Ben.

20628[/snapback]

 

Cheers,

 

I'll look around.

 

Ben.

[John Orentas]

In practise there is no foolproof way of testing the charge state of your batteries, Chris mentioned a hydrometer but to be honest I have found even these can give contradictory readings and anyway they are messy things to use.

 

The so called battery management contraptions give you some indication of the level of charge but they seem to do it with some tricky arithmetic, comparing what has gone in with what has gone out.

 

A voltmeter on it's own is useless unless the battery is nearly flat, a 1/4 charged battery will have the same output voltage as a fully charged one. The tiny difference there is, is likely to be swamped by other variations.

 

Those battery testers you might see in garages will only tell you that the battery does not have any dud cells and that it is not at the end of it's life (or it may be just flat).

 

The answer is to monitor your charging system with a voltmeter and an ammeter, learn how long it takes to replenish after a particular usage. When the charge current drops back close to zero the batteries are fully charged.

[gringogordo]

Apologies (just looked at this topic again) - my previous post was a reply to bottle rather than a self congratulatory post!

 

Cheers,

 

Ben.

[Paul Evans]

What is the best method of finding out what the state of charge the batteries are in. I have seen the all singing all dancing sterling management panel £200, is their a cheaper way of knowing when my four 135 amp batts are running low?

20618[/snapback]

The cheapest way of finding out your batteries are flat is to wake up on a dark morning to find the lights don't work, the radio won't turn on and the ice box has defrosted all over the galley floor. Sob, sob!

[DHutch]

We noramaly mesure the voltage every morning, after the batterys have been off load overnight.

- This reading is then logged each day in order to track any anonmalouse usage.

- Hopefully the alternator is keeping up with the light usage at night.

 

 

Daniel

[John Orentas]

We noramaly mesure the voltage every morning, after the batterys have been off load overnight.

- This reading is then logged each day in order to track any anonmalouse usage.

- Hopefully the alternator is keeping up with the light usage at night.

Daniel

20906[/snapback]

 

 

Daniel.

 

Why on earth do you log the voltages of the batteries every morning, what information can you possibly expect to acquire from that. For a year now I have been banging on about how meaningless off load battery voltages are.

 

If you disagree with my physics please let me know, I would then at least know that someone is casting an eye over some of the contributions I make.

Edited May 27, 2005 by John Orentas

[weeble]

Daniel.

 

Why on earth do you log the voltages of the batteries every morning, what information can you possibly expect to acquire from that.  For a year now I have been banging on about how meaningless off load battery voltages are.

 

If you disagree with my physics please let me know, I would then at least know that someone is casting an eye over some of the contributions I make.

20922[/snapback]

 

I agree with your physics John. It will do very little other than point out a shorted cell. It's a bit like using a tyre pressure gauge to detect a blow-out.

 

Cheers.... mike

[Alan Saunders]

Daniel.

 

Why on earth do you log the voltages of the batteries every morning, what information can you possibly expect to acquire from that.  For a year now I have been banging on about how meaningless off load battery voltages are.

 

If you disagree with my physics please let me know, I would then at least know that someone is casting an eye over some of the contributions I make.

20922[/snapback]

John, I cannot find your physics posts, could we have a link please.

 

Are we to expect threats of legal action from Sterling? Summing current and allowing for charging efficiency is hardly 'tricky arithmetic'. I am confident that their product does exactly what they claim.

 

I cannot agree that the float voltage of a lead-acid battery is the same at 25% as it is at 100% charge. Daniel is doing the right thing; by logging the readings he will be able to detect a trend.

 

Ignore John, ignore me, test the theory yourself! Get a meter capable of measuring 20v DC with one or two decimals (Maplin had one on offer for £4.99 recently). Attach the meter directly to the battery. Log the voltage over a period of time and note the appliances in use at the time. Decide on the levels at which you will recharge the battery e.g. 11.8v with no load 11.4v with a few lights and the TV on. Charge the batteries until the voltage stops increasing. If there are tears in the morning increase the voltage levels at which you recharge. Ideally you will recharge long before the batteries are exhausted. If this doesn't work for you, let us know.

 

Alan

[Richard Bustens]

John i think Dan is in a slightly different position to most of us, as if i remember correctly he has no charging facilities other than a alternator driven from the prop shaft and i suspect he does not want to strike up the steam engine to charge batteries.

So for him to keep a check on the state of the batteries is essential, but i would have thought it would have been better to have some means of determine the AH that went into the batteries and the same that went out so he could see what is left, rather than the voltage in the batteries, as it will still say 12v when under half full or empty depending on your oppinions.....

Edited May 27, 2005 by Richard Bustens

[maffi mushkila]

Gringogordo

 

You are looking for an Amp metre.

 

Why would anyone want a 3,25 ft amp?

[Richard Bustens]

What are you on. Maffi?

[bottle]

He's having a 'spat' cause he can't get to Crick

[DHutch]

Why on earth do you log the voltages of the batteries every morning,

For a year now I have been banging on about how meaningless off load battery voltages are.

 

Well, its not great, but it does give an indication, im sure we should get a clever little box to moniter the flow of current in and out of the battery, and then do some fancy sumns to work out how much it thinks its go in it, but we dont.

- We dont use electricty much anyway, the only things we have to run off the batterys is lighting, the water pump, a car radio, and the mobile phone charger. that latter two run though a 12v regulator, so will work untill the battery is 99% flat, and we can (an have) done without the lights before now.

 

 

Daniel

[gringogordo]

What does the 3.25 refer to ?

 

Anyway I'm interested in the volt meter question. I have a voltmeter display (green, yellow, red) which I look at now and again and although I agree that for the first half of the life of one charge it remains in the same place, after that it gradually goes down giving me an indication of how urgently I need to charge the batteries. It also reminds me to fill the cells if I haven't checked for a while as the needle doesn'r go so far 'up the green' if they are getting low. Its not clever but it works in a day to day way.

 

I kind of accept the physics of what you say John (I'm no expert but I diod the weekend course in Reading a while ago) but as my practical experience seems to differ I'm wondoring what is going on. Is

it that you are more thorough and don't let the batteries get low enough to register a difference in voltage ? Or maybe that 'the rest of you' (sorry sounds a bit abusive put like that, it's not meant to!) are looking for something a bit more precise than this general rule of thumb? Or have I just been caught out as being a fool once again?

 

Cheers,

 

Ben.

[John Orentas]

Ben.

 

I suspect that your indicator with the pretty colours is there to show the charge voltage going into the batteries, however when there is no charging it will show the battery voltage.

You will have observed that when the pointer begins to move down-wards the batteries will already be 95% discharged making measurement somewhat academic.

[bottle]

What does the 3.25 refer to ?

 

 

20942[/snapback]

 

It's completely irrelevant, just Maffi playing with words/measurement. i.e 1 metre= approx:3.25 feet.

 

Any form of metering will give an indication of what is happening with your batteries, you just need to be aware, that it is only an indication.

 

It's like most things experience of your own setup comes with time.

[Justin]

Ok

 

Thanks for all the replies. I think i will get an ammmeter and voltmeter and then go to Reading for the electrics course.

 

Cheers

 

Justin

[bottle]

Ok

 

Thanks for all the replies. I think i will get an ammmeter and voltmeter and then go to Reading for the electrics course.

 

Cheers

 

Justin

20964[/snapback]

 

 

Justin

 

I would do it the other way round, you might be able to find a less expensive supply of the items you need.

[John Orentas]

Justin

 

Have a look at the Clamp Meter thread, that would be by far the most usefull gadget you could have.

[Justin]

Thanks John

 

looks useful, i want something permanently mounted inside though so i get an idea of when i need to recharge, so although it sounds crude i think i will get an ammeter and voltmeter

 

cheers

 

Justin

 

Justin

 

Have a look at the Clamp Meter thread, that would be by far the most usefull gadget you could have.

21036[/snapback]

[John Orentas]

Thanks John

 

looks useful, i want something permanently mounted inside though so i get an idea of when i need to recharge, so although it sounds crude i think i will get an ammeter and voltmeter

 

cheers

 

Justin

21100[/snapback]

 

Not crude at all, in fact I have exactly that in my boat. An industrial volt meter, 78mm square 0 - 20 volts.

 

Similar pattern Ammeter +60 0 -60 amps centre reading with remote shunt.

 

They are not as expensive as you may think.