Batteries and living aboard

[nicknorman]

Here is a lot of interesting read on different battery and charging

 

http://www.solar-electric.com/deep-cycle-battery-faq.html

​

Some useful stuff, but also a bit of wrong/misleading stuff.

 

Going back to the subject of the OP it is interesting to note that this is yet another table of SoC vs rested voltage with slightly different numbers. It just goes to demonstrate my point about the vagaries of defining SoC and why an SoC gauge can't reasonably be awarded a high accuracy figure - there is no absolute reference to compare with.

 

Edit: sorry, just realised I've put this on thinking it was the Smartgauge accuracy thread. Doh!

Edited January 16, 2016 by nicknorman

[Graham.m]

Some useful stuff, but also a bit of wrong/misleading stuff.

 

Going back to the subject of the OP it is interesting to note that this is yet another table of SoC vs rested voltage with slightly different numbers. It just goes to demonstrate my point about the vagaries of defining SoC and why an SoC gauge can't reasonably be awarded a high accuracy figure - there is no absolute reference to compare with.

 

Edit: sorry, just realised I've put this on thinking it was the Smartgauge accuracy thread. Doh!

 

 

Interesting what would the wrong/misleading stuff be?

[George94]

The problem with batteries and charging regimes is that not even the experts can agree on everything, and in fact they not infrequently contradict themselves.

 

I have Lifeline AGM batteries. In the 2014 manual, it states that they can accept a charging current of 5C (five times capacity). The current website claims 2.5C for the same battery.

 

That's a 50% reduction. Had I been able to charge at 5C, I would have done, and I would now be feeling a little miffed.

[nicknorman]

Interesting what would the wrong/misleading stuff be?

What caught my eye was the various occurrences of battery internal resistance, and using it to explain Peukert and why batteries take less charge as they approach fully charged.

 

Internal resistance causes loss of power, not loss of current/charge.

 

Internal resistance does I believe increase at higher SoCs but the reason why charge current falls off is because there is an opposing emf from the reaction potential (bit like back emf in a motor), the chemical reaction is nearly finished, reaction is slowly taking place only deep within the plates, bubbles on the plates etc. If the internal resistance were so high that the current fell below 1% or whatever, it would be reasonable to assume that if one then short circuited the battery on would only get 1% current, which of course isn't the case. Resistance is a property unaffected by the direction of current flow, and in a battery approaching fully charged, clearly this isn't the predominant effect.

[Graham.m]

My technical knowledge of the details of this area are limited, but I have often wondered if it would be advantageous to effectively force the batteries to take more charge later in the cycle. And hence reflect the fact that if using a standalone petrol generator the compromise comes in a different place than if you where charging from the mains.

 

However, is that something which can be changed/adjusted on most chargers?

Mmmmm, whispergen...... lovely kit, but not cheap, and no longer available new to my knowlage.

 

 

Daniel

 

Think it was a badged VTE Paguro the 6kW http://www.advanceyacht.co.uk/paguro-6000-marine-generators

[by'eck]

 

Think it was a badged VTE Paguro the 6kW http://www.advanceyacht.co.uk/paguro-6000-marine-generators

 

Two totally different generators used the Whispergen name. The Mastervolt range was one and are essentially conventional design with a diesel engine direct driving typically a brushless alternator. The type I believe Daniel was referring to was from memory a vertical shaft external combustion (Sterling) engine running on diesel fuel which generated plenty of hot water and some low voltage DC current. Some further info here.

[Graham.m]

What caught my eye was the various occurrences of battery internal resistance, and using it to explain Peukert and why batteries take less charge as they approach fully charged.

 

Internal resistance causes loss of power, not loss of current/charge.

 

Internal resistance does I believe increase at higher SoCs but the reason why charge current falls off is because there is an opposing emf from the reaction potential (bit like back emf in a motor), the chemical reaction is nearly finished, reaction is slowly taking place only deep within the plates, bubbles on the plates etc. If the internal resistance were so high that the current fell below 1% or whatever, it would be reasonable to assume that if one then short circuited the battery on would only get 1% current, which of course isn't the case. Resistance is a property unaffected by the direction of current flow, and in a battery approaching fully charged, clearly this isn't the predominant effect.

 

Surely you are being over critical of a site that states, “The subject of batteries could take up many pages. All we have room for here is a basic overview of batteries commonly used with photovoltaic power systems”, the word used is basic, and surely you don’t expect them to be writing a book on batteries.

 

“Internal resistance causes loss of power, not loss of current/charge” Surely power has three components voltage and current (amps) and resistance (impedance)so how can you have a loss of power (watts) without a loss of current/charge/volts with a given impedance.

 

You talk about “…charge current falls off is because there is an opposing emf (volts) from the reaction potential…” Surely that is an increase in the impedance of the battery thus an increase in resistance against the voltage/current trying to enter the battery. Just like blowing up a bicycle tyre, when you start the air goes in easily as the amount of air introduce into the tyre increases the effort to push the pump increases because of the pressure (emf/voltage) of the air in the tyre and the resistance it exerts against the incoming pressure (voltage). As I can well remember the end of the pump gets hot (lost effort producing heat) power/charge lost. Or even just like two magnets N pole to N pole resisting each other and pushing apart.

 

So maybe as a simple explanation they have not done too badly, maybe not absolutely technically correct but they have got over the basic idea to their purchasers.

Edited January 16, 2016 by Graham.m

[nicknorman]

Graham, your post seems to be in large font so I'm not going to quote it.

 

Internal resistance causes a loss of power, not current. Power is made up of voltage and current. When passed through a resistor, voltage is dropped, current remains the same. This causes a loss of power but not of current or charge. The basis of a battery is a chemical reaction that moves electrons. Electrons moving creates current, current moving for a while, moves charge. Therefore internal resistance has no bearing on anything to do with loss of current or charge (AH) including the capacity of the battery in AH.

 

Regarding the second bit no I am trying to get away from a concept of resistance or impedance, both of which are not affected by polarity. Your analogy of the tyre is far better.

 

You may think me pedantic but then so do folk who complain when they are picked up for using amps, amphours, or amps/hour. I'll still do it though, as eventually it causes them huge confusion. If you are going to use analogies, make them ones that vaguely fit the principles such as your tyre one.

[Graham.m]

Graham, your post seems to be in large font so I'm not going to quote it.

 

Internal resistance causes a loss of power, not current. Power is made up of voltage and current. When passed through a resistor, voltage is dropped, current remains the same. This causes a loss of power but not of current or charge. The basis of a battery is a chemical reaction that moves electrons. Electrons moving creates current, current moving for a while, moves charge. Therefore internal resistance has no bearing on anything to do with loss of current or charge (AH) including the capacity of the battery in AH.

 

Regarding the second bit no I am trying to get away from a concept of resistance or impedance, both of which are not affected by polarity. Your analogy of the tyre is far better.

 

You may think me pedantic but then so do folk who complain when they are picked up for using amps, amphours, or amps/hour. I'll still do it though, as eventually it causes them huge confusion. If you are going to use analogies, make them ones that vaguely fit the principles such as your tyre one.

My post is in a font I can read

 

I think we are going to have to disagree with regard to the site. I did not set out to describe the finer points of emf/ internal resistance and impedance I set out to draw a picture that a layman might have a chance of understanding just as the site did. It is all very well to get hide bound by pure theory and expect the world to agree or understand. Sometime it is better to ignore the Ah instead of A; normally it is quite obvious and just demonstrates it in your actual reply rather castigating people for being wrong.

 

I think the site had done quite a good job, as I said earlier not technically theoretically perfect but sufficient to awaken its customers who probably are laypeople to the needs to consider certain things.

Edited January 17, 2016 by Graham.m

[Loafer]

 

Surely power has three components voltage and current (amps) and resistance (impedance)so how can you have a loss of power (watts) without a loss of current/charge/volts with a given impedance.

 

 

 

Power has two compoments, Volts and amps. A resistance will consume some power (I2R), normally dissipated as heat or motion. The current will remain the same through the circuit. Some volts will be 'lost' across the resistance. (=IR)

 

Or has summat changed lately?

[Paul C]

Huh? We did electricity basics in GCSE donkey's years ago, in a series circuit the same current flows through each bit of the circuit!!!

 

 

I₁ = I₂ = I₃

[Graham.m]

 

 

Huh? We did electricity basics in GCSE donkey's years ago, in a series circuit the same current flows through each bit of the circuit!!!

 

 

I₁ = I₂ = I₃

Yep, so where is the power loss. I carefully did not specify just left R as a constant:) and how does that affect the charge.

[nicknorman]

Yep, so where is the power loss. I carefully did not specify just left R as a constant:) and how does that affect the charge.

 

The power loss is caused by a reduction in the voltage. There is no effect on the charge in terms of loss of charge or battery capacity.

[sjc]

Power generation is given by current and voltage, whereas power consumption does depend on resistance - As Loafer demonstrated in post#85, manipulation of Ohm's law can make it a factor of whichever you prefer : ( I2R, or V2/R, or VI ( where V = voltage drop across the resistor ) ).

[Paul C]

 

 

Yep, so where is the power loss. I carefully did not specify just left R as a constant:) and how does that affect the charge.

 

Why did you leave R as a constant?

[George94]

My post is in a font I can read

 

I think we are going to have to disagree with regard to the site. I did not set out to describe the finer points of emf/ internal resistance and impedance I set out to draw a picture that a layman might have a chance of understanding just as the site did. It is all very well to get hide bound by pure theory and expect the world to agree or understand. Sometime it is better to ignore the Ah instead of A; normally it is quite obvious and just demonstrates it in your actual reply rather castigating people for being wrong.

 

I think the site had done quite a good job, as I said earlier not technically theoretically perfect but sufficient to awaken its customers who probably are laypeople to the needs to consider certain things.

 

But everybody else's posts are in a smaller font. How are you reading them?

 

I suggest that instead of making life difficult for everybody else, you instead buy some spectacles or tweak your browser settings so that you can read everything.

[peterboat]

 

Two totally different generators used the Whispergen name. The Mastervolt range was one and are essentially conventional design with a diesel engine direct driving typically a brushless alternator. The type I believe Daniel was referring to was from memory a vertical shaft external combustion (Sterling) engine running on diesel fuel which generated plenty of hot water and some low voltage DC current. Some further info here.

i have a whispergen the stirling engine one, very pleased with it, quiet, clean, hot central heating and it runs on diesel or kero 72 amps 12volts from my point of view its more than some low dc current. its also fairly cheap to run and easy to service.

My technical knowledge of the details of this area are limited, but I have often wondered if it would be advantageous to effectively force the batteries to take more charge later in the cycle. And hence reflect the fact that if using a standalone petrol generator the compromise comes in a different place than if you where charging from the mains.

 

However, is that something which can be changed/adjusted on most chargers?

Mmmmm, whispergen...... lovely kit, but not cheap, and no longer available new to my knowlage.

 

 

Daniel

you can still get the odd one from tipos marine in rotherham secondhand he did have some 24 volt models in late last year

[Graham.m]

 

But everybody else's posts are in a smaller font. How are you reading them?

 

I suggest that instead of making life difficult for everybody else, you instead buy some spectacles or tweak your browser settings so that you can read everything.

 

With great difficulty and there is no reason in terms of data transmission for them not to be larger.

It is a shame that the site does not appear to have what is a common facility for the user to select there own size of font for viewing

Put it simply

 

Take a 12V battery (Bat A) with 0 ohms effective internal resistance and a load of 0.06 Ohms. I would suggest that the current through the load will be 200A and the power dissipated in the load will be 2.4kW

 

Take the a 12V battery (Bat B ) with an effective internal resistance of 0.006 ohms and the load of 0.06 Ohms the current through the load will only be 181.81A and the voltage across the load will be 10.909V and the power dissipated will be 1.983kW approx while the total power through the battery and load is 2.1817kW approx So what has happened to the 0.1984 kW. I would suggest that has been dissipated in the battery as heat etc.

 

I suggest that if Bat A is charged with a 14V charger at a current of 200A and a power of 2.8kW, all the energy will be stored in the battery.

 

If we do the same with Bat B the internal resistance of 0.006 Ohms dissipates 0.24kW as heat etc. There is 1.2V across the internal resistance so the battery is seeing 12.8V for electrolysis or 2.56kW of the power is stored. Thus I suggest that because of the batteries internal resistance 0.24kW are turn into heat. Thus the energy stored in the battery is reduce from 2.8kW to 2.56kW or a loss because of the internal resistance of 8.57% of the energy put into the battery to charge it.

 

If the above continued for an hour Bat A would have store 2.8kWh or at say 12.5V 224Ahs while Bat B would have stored 2.56kWh or 204.8Ah.

 

Of course in real life it does not happen that simple because the battery is always changing because of the chemical reactions within it. However it does I suggest demonstrate what is euphemistically called a battery’s internal resistance effect simply on both discharge and charging.

Edited January 17, 2016 by Graham.m

[nicknorman]

You were doing well up to the penultimate para. Back-calculating the AH from the power was your downfall since you chose to use the same voltage and get different AH, whereas in fact the voltage is less and the AH the same for Bat B.

[Graham.m]

You were doing well up to the penultimate para. Back-calculating the AH from the power was your downfall since you chose to use the same voltage and get different AH, whereas in fact the voltage is less and the AH the same for Bat B.

 

I am sorry we are going to disagree about the penultimate paragraph, maybe my wording is bad. If a battery after charge has 2.8kWhs stored in it the Ahs stored is related surely to the voltage of the battery at the time of delivery. i.e. If a battery has 2.8kWh stored and it is standing at 12 volts the Ahs available in that battery are 233.3Ah If the voltage is 12.7V than it is 220.4Ahs

 

Batteries store power which is watts hours V x I x h

[by'eck]

i have a whispergen the stirling engine one, very pleased with it, quiet, clean, hot central heating and it runs on diesel or kero 72 amps 12volts from my point of view its more than some low dc current. its also fairly cheap to run and easy to service.

you can still get the odd one from tipos marine in rotherham secondhand he did have some 24 volt models in late last year

 

I met a Dutch round the world cruiser on a 55 foot motorsailer in Sardinia way back in 2001. He had fitted the first Whispergen sold in Europe. The deal was that if it needed repair anywhere in the world the dealer would fly out and fix it under warranty. He proudly demonstrated it to me. It was indeed very quiet although was not impressed with the minute or so of battery current required to spin it up. I remember thinking this could be more than a jump lead job if you had flat batteries. It also occurred to me that the amount of heat produced was way in excess of the electrical energy and consequently how suited it would be to hot climes, especially when my conventional generator (the other Whispergen) provided six times the electrical power for a lower outlay.

 

Sounds like its found its ideal location in a canal boat although at the high price and with such a small market, was doomed to failure.

[nicknorman]

I am sorry we are going to disagree about the penultimate paragraph, maybe my wording is bad. If a battery after charge has 2.8kWhs stored in it the Ahs stored is related surely to the voltage of the battery at the time of delivery. i.e. If a battery has 2.8kWh stored and it is standing at 12 volts the Ahs available in that battery are 233.3Ah If the voltage is 12.7V than it is 220.4Ahs

 

Batteries store power which is watts hours V x I x h

We're going to get accused of getting bogged down in trivia again but the bottom line is that internal resistance causes loss of power. It causes no loss of current or stored charge. Power can be dissipated. Current cannot be dissipated. If you can't grasp that there is no point in continuing. In fact there is no point in continuing.

[Graham.m]

We're going to get accused of getting bogged down in trivia again but the bottom line is that internal resistance causes loss of power. It causes no loss of current or stored charge. Power can be dissipated. Current cannot be dissipated. If you can't grasp that there is no point in continuing. In fact there is no point in continuing.

 

Trivia can be fun but not when you have to type it all out, it is better by a log fire with a glass of brandy. I think for the layman the important point is that because of the internal resistance of a battery, variable, there is a loss both charging and discharging.

[peterboat]

 

I met a Dutch round the world cruiser on a 55 foot motorsailer in Sardinia way back in 2001. He had fitted the first Whispergen sold in Europe. The deal was that if it needed repair anywhere in the world the dealer would fly out and fix it under warranty. He proudly demonstrated it to me. It was indeed very quiet although was not impressed with the minute or so of battery current required to spin it up. I remember thinking this could be more than a jump lead job if you had flat batteries. It also occurred to me that the amount of heat produced was way in excess of the electrical energy and consequently how suited it would be to hot climes, especially when my conventional generator (the other Whispergen) provided six times the electrical power for a lower outlay.

 

Sounds like its found its ideal location in a canal boat although at the high price and with such a small market, was doomed to failure.

in some yachts in cold climes they provide heat for the cabin as well. you can program in auto start, if the batteries get to a certain point it starts, which would protect you from flat batteries. also your whispergen had to then have a battery charger as well, the whispergen doesnt. the reason whispergen stopped producing wasnt poor sales it was an earthquake in new zealand that destroyed the factory. thy do make gas models in spain.

for mike this machine would be great, wakes up to charging batteries and warm boat comes in at night to charging batteries and warm boat [it works on a timer].

[Loafer]

 

I am sorry we are going to disagree about the penultimate paragraph, maybe my wording is bad. If a battery after charge has 2.8kWhs stored in it the Ahs stored is related surely to the voltage of the battery at the time of delivery. i.e. If a battery has 2.8kWh stored and it is standing at 12 volts the Ahs available in that battery are 233.3Ah If the voltage is 12.7V than it is 220.4Ahs

 

Batteries store power which is watts hours V x I x h

 

 

 

V x I x h is energy, not power. Batteries store energy, which is a measure of ability to do work. It is stored as chemical energy, and isn't converted to electrical energy until a circuit is made and electrons start to flow.

 

Well that's how I remember it from about 1975...

Edited January 17, 2016 by Loafer