Battery charge question

[MtB]

 

 

 

8 minutes ago, Boat afloat said:

an energy audit is to systematically test the batteries voltage with certain usage behaviour is it and see what's happening to the juice?

 

Broadly speaking, a power audit is simply a list of all the electrical stuff in your boat with the current draw it takes x the time it will be running for. More accurately called an energy audit. 

 

This tells you the amount of energy you will draw from your batts each day, and from that you can work out what batt capacity you need and also how to recharge them adequately. 

 

Start by reading Tony's website here: http://www.tb-training.co.uk/cover.html

 

Then read the "Battery Primer" on this site, linked earlier. 

[Tony Brooks]

5 minutes ago, Boat afloat said:

I still think 'something' is going on whether it's in excessive draw somewhere, poor recharging or tired batteries.

 

an energy audit is to systematically test the batteries voltage with certain usage behaviour is it and see what's happening to the juice?

 

1. I suggested it might be a cell or cells shorting internally but many years of experience tells me statements about what a boater thinks without evidence is pretty much worthless - especially when they think they might be having to find several hundred pounds for new batteries. You need to measure the charging voltage at about 1200 rpm after several hours cruising before we can do much more diagnosis.

 

2. The power audit. List every electrical item you have on board and how many amps it draws - you may have to convert from Watts. Amps = Watts /12V or 24V

 

Then beside each on list how long they will be in use per 24 hour period. Use a worst case scenario and include the amps the inverter uses just to work itself.

 

Multiply amps by time for each one and then total the results. You need a battery capacity of at least twice that.

 

Also remember you have to put that much plus another 1/3 to 1/2 again to get the batteries back to where they were before you discharged them.

 

You can NOT use the alternators rated output - use about half over three to four hours and any longer it keeps reducing.

You can NOT use the solar panels rated output. The most you will get is perhaps half across noon, less but risisng before and less but falling after noon.

 

[Boat afloat]

5 minutes ago, Tony Brooks said:

 

1. I suggested it might be a cell or cells shorting internally but many years of experience tells me statements about what a boater thinks without evidence is pretty much worthless - especially when they think they might be having to find several hundred pounds for new batteries. You need to measure the charging voltage at about 1200 rpm after several hours cruising before we can do much more diagnosis.

 

2. The power audit. List every electrical item you have on board and how many amps it draws - you may have to convert from Watts. Amps = Watts /12V or 24V

 

Then beside each on list how long they will be in use per 24 hour period. Use a worst case scenario and include the amps the inverter uses just to work itself.

 

Multiply amps by time for each one and then total the results. You need a battery capacity of at least twice that.

 

Also remember you have to put that much plus another 1/3 to 1/2 again to get the batteries back to where they were before you discharged them.

 

You can NOT use the alternators rated output - use about half over three to four hours and any longer it keeps reducing.

You can NOT use the solar panels rated output. The most you will get is perhaps half across noon, less but risisng before and less but falling after noon.

 

 

Thanks Tony that is super helpful. I'll get onto the audit but I do think we are super low on usage (not running the fridge, no TV, running battery operated lighting etc.

 

Our inverter does look pretty basic though so I am eying that up suspiciously.

 

Presumably if I simply turn off all electrics to the boat overnight and see what has happened to the batteries overnight that should give us a solid idea of their resting health?

 

I am going to get Amps and Volts straight in my head on this too...drill...drill...drill...

[Tony Brooks]

1 minute ago, Boat afloat said:

 

I am going to get Amps and Volts straight in my head on this too...drill...drill...drill...

 

It is all in the electrical notes on tb-training.co.uk.

 

My advice would be to go for an all day cruise and tell us what the voltage was at 1200 rpm just before you shut down. Then use some electricity as normal. Just before turning in or going home  disconnect ALL the negative cables at the batteries. Measure and note each battery voltage. The next morning or within  a few days remeasure all the voyages again before reconnecting. Both voltages should be within about 0.1 or less volts of each other and the more they differ the greater any internal short.

 

If you have a decent digital ammeter (NOT a multi-meter) monitoring the domestic charging current keep cruising or running the engine at 1200 rpm until it reads about 2% of battery capacity with the voltage above about 14.2 to 14.4 and not dropping  anymore over about an hour. Then the batteries will be as charged as you are likely to get them. Then see how the batteries perform overnight.

 

If the ends of the batteries are bowing out it is an indication that you have lost a lot of capacity to sulfation.

 

 

 

 

[MtB]

1 hour ago, Boat afloat said:

I am going to get Amps and Volts straight in my head on this too...drill...drill...drill...

 

One of the BEST ways to learn is to explain a subject to someone else. Try it on here. Give the board a two-sentence explanation of what a volt is, and what an amp is, according to your understanding so far.

 

Not a trick question, if you have a bash if there is anything wrong we can point you in the right direction.

 

 

[Bod]

3 hours ago, Boat afloat said:

Yes, to be fair the 13 point something volts reading is from the digital meter in the boat, which I think is pessimistic. I'll get a proper reading from the batteries themselves when running - good plan!!

 

Yes, the positive terminal of the 5th battery is bare. I've attached a picture of what I am trying to describe. I'm not with the boat to take pics unfortunately.

 

In terms of other points:

 

- the router is a 240v jobbie running through the inverter yes.

 

- when I say very little else running I really mean it. Unless it's something hidden in the boat, or the inverter is just drawing huge power I can't see what else is doing it.

 

- regards my comment about the batteries settling at 12.6v resting charge after a cruise that should be fine shouldn't it? Should I be expecting much more than that?

 

- the solar is set to cut off at 14.5V IIRC.

 

That's a great analogy - I'll remember that one.

 

What type of batteries do you have?

Sealed lead acid, no removable tops, or flooded lead acid where the tops are removable.

If removable, when was the water level last checked or topped up?

If the water level is low, or missing then trouble can be expected.

ONLY TOP UP with distilled or deionised water.  Tap water will wreck the battery.

 

Bod

[nicknorman]

5 hours ago, MtB said:

There have been a couple of threads recently where people have had their batts on long term float, then gone out for a cruise and found the previously satisfactory battery bank as good as useless. Its not supposed to happen this way but it looks to me as though batts on long term float sulfate up just like partially charged batts. 

We used to have lead acid on long term float in the marina. When we went out, for the first cycle or maybe 2, the capacity seemed pants. But they quickly recovered.

[MtB]

2 minutes ago, nicknorman said:

We used to have lead acid on long term float in the marina. When we went out, for the first cycle or maybe 2, the capacity seemed pants. But they quickly recovered.

 

 

Yes but your batteries were scared of you. The posters I'm on about are not experiencing improvements in performance after several cycles. 

[Tony Brooks]

57 minutes ago, nicknorman said:

We used to have lead acid on long term float in the marina. When we went out, for the first cycle or maybe 2, the capacity seemed pants. But they quickly recovered.

 

That is why I wonder if it is stratification because I can't think of anything else that fit it. I am happy to be proved wrong because we all learn.

[Naughty Cal]

6 hours ago, MtB said:

There have been a couple of threads recently where people have had their batts on long term float, then gone out for a cruise and found the previously satisfactory battery bank as good as useless. Its not supposed to happen this way but it looks to me as though batts on long term float sulfate up just like partially charged batts. 

We always found that the batteries on NC were a bit sluggish thefirst few times they were after being plugged in and the boat ashore not being used for the winter.

 

They seemed to recover again after a few cruises.

[David Mack]

Deleted as question has already been answered.

Edited April 16, 2022 by David Mack

[Boat afloat]

15 hours ago, MtB said:

 

One of the BEST ways to learn is to explain a subject to someone else. Try it on here. Give the board a two-sentence explanation of what a volt is, and what an amp is, according to your understanding so far.

 

Not a trick question, if you have a bash if there is anything wrong we can point you in the right direction.

 

 

OK - here goes then!!

 

voltage is a measure of pressure in an electrical system whereas amps is a measure of the amount of energy flowing through the system?

I need watts to feed the electrical items such as the router and make them work.

 

volts x amps = watts.

 

so, if the voltage drops I’ve got a system that isn’t powerful enough to push stored energy around the system, plus low wattage due to the above calculation? Is that (anything like)  right..?

[nicknorman]

Not quite. Amps is not a measure of energy, it is a measure if the flow rate of “stuff” (electrical charge). Using the water analogy, it is the mass ( or volumetric) flow rate of water. But some water flowing without much pressure (voltage) doesn’t carry much power. In order to extract power from flowing water you need to add some sort of restriction. If the pressure (voltage) is very low, the restriction simply causes the flow rate to drop to nearly zero - no significant amount of power can be extracted. But if the pressure is high, significant flow continues and power can be extracted from the flow. After the restriction of course the pressure of the flow is much reduced, and the reduction in pressure corresponds to the power extracted. Power = pressure x mass flow rate, or watts = volts x amps.

 

As you say, insufficient voltage means the charge isn’t pushed round the circuit hard enough. But also, insufficient charge voltage means the rather complex chemistry in the battery moves over time to a “bad state” whereby the battery acquires a technical state known as “knackered”.

Edited April 17, 2022 by nicknorman

[Tony Brooks]

I find it easier to think of amps as the number of electrons flowing past a point in the circuit in a given time, the quantity of electrons flowing. However the actual number is so huge it is meaningless to most people. The more electrons flowing the more work they can do, the greater the voltage the more electrons will be caused to flow in a given circuit.

[Tony1]

 

These analogies about flowing water are all very well, but sometimes its better to just bite the bullet and get the full technical detail on a topic.

Its about time the OP learned about the electrical pixies. 

The pixies live in wires and in batteries, and they make bulbs light up by illuminating thousands of tiny magic wands.

And of course, you get a better class of pixie in lithium batteries.

There's a lot more to it than this (obvs), but too much theoretical detail in one go might not be helpful.

 

 

[MtB]

2 hours ago, Boat afloat said:

Is that (anything like)  right..?

 

You are definitely on the right track, well done.

 

Nick started well but then managed to over-complicate it and Tony's model requires more imagination than the 'water' analogy Nick mentions.

 

I like the water analogy as a starting point but beware it breaks down once you get into the detail. In particular I think it's good to think of a water wheel extracting power from a river. A big water wheel will be capable of extracting more power as the height of the water falling through it is greater, and equivalent to voltage. The current (number of electrons passing a point) is the amount of water passing over the wheel. Gallons per minute, say, and equivalent to Amps.

 

The bigger the amount and the higher the fall, the more power you will get. Also, the more gallons per minute (Amps) flowing through it the more power. A wider water wheel in a bigger river will deliver more power than a thin water wheel fed by a little stream, even if the fall (voltage) is the same.

 

And yes Amps x Voltage = power in Watts. 

 

 

 

P.S. Tony's explanation is probably the most accurate but I notice he failed to mention the concept of 'magic smoke'. There is a skool of thought that electronic circuits are powered by magic smoke rather than electrons. We know this because if something goes wrong with the circuit and the magic smoke all comes out, it will stop working. Watch out for references to magic smoke in the electrical threads to se how widely accepted this hypothesis is! 

[Tony Brooks]

35 minutes ago, MtB said:

like the water analogy as a starting point but beware it breaks down once you get into the detail. In particular I think it's good to think of a water wheel extracting power from a river. A big water wheel will be capable of extracting more power as the height of the water falling through it is greater, and equivalent to voltage.

 

Boat Afloat - ignore this.

 

I think even that analogy breaks down depending upon if it is an undershot wheel or a breast/overshot wheel, the larger diameter wheel will produce more torque (and hence power when time is considered) because Torque = force tomes perpendicular distance so a larger diameter wheel produces more torque for a given water flow than a smaller one.

45 minutes ago, Tony1 said:

 

These analogies about flowing water are all very well, but sometimes its better to just bite the bullet and get the full technical detail on a topic.

Its about time the OP learned about the electrical pixies. 

The pixies live in wires and in batteries, and they make bulbs light up by illuminating thousands of tiny magic wands.

And of course, you get a better class of pixie in lithium batteries.

There's a lot more to it than this (obvs), but too much theoretical detail in one go might not be helpful.

 

 

 

Actually if you said the pixies were a bit like electrons that would be far closer to the truth than many other analogies.

[Tony1]

48 minutes ago, Tony Brooks said:

 

Actually if you said the pixies were a bit like electrons that would be far closer to the truth than many other analogies.

 

For many years I have pioneered the field of pixie studies, whilst mainstream science was banging on with all these unlikely yarns about electrons and volts.

It's very satisfying to see that the experts are now coming round to my point of view. 

 

It's all documented in my forthcoming self-published Amazon tutorial, 'Practical Marine Electrics- The Pixies and Me'

 

There are some people who will get squeamish about having to sacrifice a live gerbil at noon each day in order to keep the pixies working, but long experience has demonstrated that no other small mammal has such positive effects. 

 

Am I happy that I have to sacrifice small mammals to the pixies every day? 

Well ok. Yes I am. 

 

Edited April 17, 2022 by Tony1

[Jen-in-Wellies]

1 hour ago, Tony1 said:

 

These analogies about flowing water are all very well, but sometimes its better to just bite the bullet and get the full technical detail on a topic.

Its about time the OP learned about the electrical pixies. 

The pixies live in wires and in batteries, and they make bulbs light up by illuminating thousands of tiny magic wands.

And of course, you get a better class of pixie in lithium batteries.

There's a lot more to it than this (obvs), but too much theoretical detail in one go might not be helpful.

 

 

Completely wrong. It's all done by magic smoke. 😀

[MtB]

1 minute ago, Jen-in-Wellies said:

Completely wrong. It's all done by magic smoke. 😀

 

As already explained four posts previous, like!! 

 

 

[Tony1]

7 minutes ago, Jen-in-Wellies said:

Completely wrong. It's all done by magic smoke. 😀

 

The OP needs practical solutions and details, and you're giving him some childish nonsense about magic smoke?

I'm disappointed in you.

And so are the pixies.  

 

[Tony Brooks]

s

6 minutes ago, Tony1 said:

 

The OP needs practical solutions and details, and you're giving him some childish nonsense about magic smoke?

I'm disappointed in you.

And so are the pixies.  

 

 

perhaps they are thinking of magic smoke molecules as electrons

[Ronaldo47]

If your batteries have accessible filler caps, have a look at the plates.  Sulphated plates are slate-grey, charged plates are a dark chocolatey brown. If you have a shorted cell, the acid will often be muddy.  

 

My 1940's book on accumulator charging gives 10.8 V (1.8V per cell) as the lowest voltage to safely  discharge a 12V accumulator  before hard, and therefore difficult to reverse, crystalline lead sulphate is created, but it does depend on things like acid strength and how quickly recharge takes place. I guess that battery plate alloys may  have changed somewhat since the 1940's. 

 

 

[Arthur Marshall]

Even though I studied physics in the olden days, I can say that, having read bits of this thread, this is the first time in seventy odd years anyone has made me actually get at least a partial grip on the difference between volts and amps and what the hell they do.

I'm not entirely convinced by the pixies, but I'm keeping an open mind.

Edited April 17, 2022 by Arthur Marshall

[GUMPY]

Whatever happened to the Voles?

I thought it was all done with lots of Voles  running around.