battery charging from my generator

[goboatingnow]

Originally Posted by FlyingCloud1937

Hi Mark,

Amp Hour Law of charging is not Rick's thesis, it's been about since 1920, and almost every proper charger try's it's best to emulate it. In the battery industry it is considered "Best Practice"

Try this link it's a combined editorial for how to set up an On-board Power System. To get the most efficient system you can.

Everything installed to a boat is a compromise of some sort. But understanding how it all works together allows the owner/designer to achieve the best compromise.

Lloyd

I'm not sure to is as its conflicts with a lot of battery specs. Most manufacturers specifiy C/5 or C/10 as the best practice in recharge currents. This would be well exceed by the AMp Hour law.

Dave

[s/v Jedi]

Originally Posted by goboatingnow

I'm not sure to is as its conflicts with a lot of battery specs. Most manufacturers specifiy C/5 or C/10 as the best practice in recharge currents. This would be well exceed by the AMp Hour law.

Dave

Good old LA won't accept much over C/5 anyway.

[btrayfors]

Originally Posted by s/v Jedi

Good old LA won't accept much over C/5 anyway.

Depends on the type of "LA". Flooded, AGM, Gels are ALL lead-acid batteries.

Flooded batteries at 50% SOC may accept about 25% of their CA rating (C/4).

Gels will accept more.

AGMs will accept about 120% of their CA rating (C/0.8) when 50% discharged. When more deeply discharged they'll accept as much as 500-600% of their CA rating (C/0.17).

I, too, find the "AMPhour charging regime" to be a bit optimistic about how much amperage batteries will accept.

In any case, as I've said repeatedly and continue to emphasize, the batteries themselves will determine how much amperage they're going to accept (a function of their internal resistance at any given state of charge), so long as the voltage is held constant.

And, yes, for non-believers.....chargers DO in fact control their voltage output in the absorption, float, and equalization stages. How do they do this? Zener diode circuits, or their equivalent, allow chargers to limit their output voltage to any desired level.

Bill

[s/v Jedi]

Originally Posted by btrayfors

Depends on the type of "LA". Flooded, AGM, Gels are ALL lead-acid batteries.

Flooded batteries at 50% SOC may accept about 25% of their CA rating (C/4).

Gels will accept more.

AGMs will accept about 120% of their CA rating (C/0.8) when 50% discharged. When more deeply discharged they'll accept 500-600% of their CA rating (C/0.17).

I, too, find the "AMPhour charging regime" to be a bit optimistic about how much amperage batteries will accept.

In any case, as I've said repeatedly and continue to emphasize, the batteries themselves will determine how much amperage they're going to accept (a function of their internal resistance at any given state of charge), so long as the voltage is held constant.

And, yes, for non-believers.....chargers DO in fact control their voltage output in the absorption, float, and equalization stages. How do they do this? Zener diode circuits, or their equivalent, allow chargers to limit their output voltage to any desired level.

Bill

Yep, flooded equals "good old"

I do believe there are some PWM chargers like Mark described, there's one cheap one that many like, I forgot the name, but many do voltage regulation for all but bulk phase yes.

[btrayfors]

A simple demonstration of battery charge acceptance.

Take a bench power supply which has control over both voltage and amperage. The very common Astron VS-35M is an example.



This is one of several adjustable power supplies in my shop which allow you control over both voltage and amperage (current).

OK, let's hook this puppy up to, say, an AGM battery.

We'll start with zero amperage setting and with a 12 VDC voltage setting.

Turn it on. Volts go up to 12.0, because that's what we've chosen on the dial. Amps (current) remain at zero....again, because that's what we've chosen.

Now, slowly increase the amps dial, and watch the ammeter. It begins to rise until.....it stops at, say, 12 amps. Even if we turn the amps dial up all the way to 35, meaning the power supply is ready to provide up to 35 amps, the battery only accepts 12 amps.

If we leave the amps dial up at 35 amps and very slowly increase the volts dial while watching the amps dial, we'll see the amps begin to creep up higher. We'd want to be careful not to increase the volts dial beyond what is a good voltage for charging this battery, otherwise damage could be done to the battery over time.

Lesson: With the voltage held constant, amperage will be determined by the battery's ability to accept charging current at its present state of charge. Period.

Bill

[btrayfors]

Originally Posted by s/v Jedi

Yep, flooded equals "good old"

I do believe there are some PWM chargers like Mark described, there's one cheap one that many like, I forgot the name, but many do voltage regulation for all but bulk phase yes.

Most "smart chargers" do voltage regulation for all but the bulk phase. I think the ones you're referring to are the Iota line of chargers.....very good chargers for the money. I've got two of them and they've been flawless for 6-7 years now. Have installed a bunch of them in client's boats, too.

Bill

[s/v Jedi]

Originally Posted by btrayfors

Most "smart chargers" do voltage regulation for all but the bulk phase. I think the ones you're referring to are the Iota line of chargers.....very good chargers for the money. I've got two of them and they've been flawless for 6-7 years now. Have installed a bunch of them in client's boats, too.

Bill

Yep Iota, they are PWM IIRC.

[colemj]

Originally Posted by btrayfors

Lesson: With the voltage held constant, amperage will be determined by the battery's ability to accept charging current at its present state of charge. Period.

Bill,

I have not been debating that - it is simply Ohm's law.

What I have argued is the concept that battery chargers do not control current. Yes, they control the voltage a battery is allowed to use to draw current, but that voltage regulation is actually a regulation of the current supplied to the battery by the charger.

Switch mode regulators are used on many common chargers. The IOTA is one. In fact, almost all smaller, lighter chargers use this method (I won't mention the "X" word). You have already conceded that switch mode regulators operate by controlling the current/time profile, so at least half the chargers out there are now agreed to control current (period).

Even your zener example uses current regulation to control the battery voltage. That zener is connected between the base of a FET and the battery, with a variable resistance between the zener and the collector on the FET. Run that, and you will see that the feedback mechanism to keep the FET base at a specific voltage is the collector-emitter current.

Larger, heavier transformer based chargers may regulate the way you suggest, but they require heavy heatsinks to do so and dissipate a lot of power in that heat.

Your power supply example is not a good one because it operates differently than a charger, but it actually proves my point - how do you think the regulation is occurring in that power supply? What do you see if you set the voltage to 15V and the amperage to 0V? What happens when you set the amperage constant and increase the voltage? That supply is not acting independently in both its controlling modes.

Mark

[FlyingCloud1937]

Originally Posted by colemj

Bill,

I have not been debating that - it is simply Ohm's law.

What I have argued is the concept that battery chargers do not control current. Yes, they control the voltage a battery is allowed to use to draw current, but that voltage regulation is actually a regulation of the current supplied to the battery by the charger.

Switch mode regulators are used on many common chargers. The IOTA is one. In fact, almost all smaller, lighter chargers use this method (I won't mention the "X" word). You have already conceded that switch mode regulators operate by controlling the current/time profile, so at least half the chargers out there are now agreed to control current (period).

Even your zener example uses current regulation to control the battery voltage. That zener is connected between the base of a FET and the battery, with a variable resistance between the zener and the collector on the FET. Run that, and you will see that the feedback mechanism to keep the FET base at a specific voltage is the collector-emitter current.

Larger, heavier transformer based chargers may regulate the way you suggest, but they require heavy heatsinks to do so and dissipate a lot of power in that heat.

Your power supply example is not a good one because it operates differently than a charger, but it actually proves my point - how do you think the regulation is occurring in that power supply? What do you see if you set the voltage to 15V and the amperage to 0V? What happens when you set the amperage constant and increase the voltage? That supply is not acting independently in both its controlling modes.

Mark

Mark,

You are in the Wrong Head...

Of course Chargers Control the Amount of Current flowing into the battery.

Yes, a battery will accept current as long as the charge voltage is at least .3 volts higher then the actual terminal voltage of the battery at the moment.

But that does not mean that the battery will accept the charge current... What really happens is... It dissipates all of the charge current that it can not accept into heat... This along with the the elevated voltage is what causes batteries to "Make Water".

It's really not just water, it's the moisture that you find on top of the bats and the undersides of the covers, it's very corrosive.

Lloyd

[goboatingnow]

I haven't the finger time to start a course on ' regulation' . But there are some over simplistic description s going on here.


A power supply or a charger regulates voltage. It does not regulate current ( see below ) , why , if the load is fixed ( at a given point in time ) then regulating voltage causes a fixed current. Raising the voltage causes more current , lowering it causes less. If the load demands more or less current , that's merely power transfer. ( in effect the load impedance changes)

So in a charger connected to a battery , once the charger is operating within its limits , current IS solely determined by the battery at a given voltage. The charger does not " regulate " current , it is a voltage source ( see float mode explanation for current foldback)

The Zener FET example is a pure voltage control loop by the way.

Now to current control, ( like in the power supply example ) there are two types of current control , crowbar and fold back. Crowbar is typically used for short circuit protection , fold back is a process whereby the voltage is reduced to regulate the amount of current , ohms laws doing the rest. Note again voltage is controlled. This is similar to a constant current source , the output voltage of such a source varies between 0 and infinity in order to keep the exact current flowing in the load.

A voltage source being current varying between 0 and infinity to keep a fixed voltage. A charger or a power supply ( there is no difference ) is a voltage source , albeit an imperfect one , as its has an appreciable output impedance , whereas are fact a perfect voltage source has 0 output impedance ( a perfect current source has infinite output impedance )


The PSU example with the adjustable voltage and current , is lying to you. The voltage meter is reading the voltage BEFORE the current fold back control stage. The actual output voltage is being controlled when you adjust the current control to ensure the current you requested is only being delivered to the load. ( if you think about it if the load is a fixed impedance then to control current you MUST control voltage.

You cannot actually build a power supply that in effect provides an independent control of current and voltage at the load terminals, otherwise you'd be breaking ohms law

So in charging lead acid , the charger attempts voltage regulation ( I say attempts , because the load is also a voltage source ) , think about it as two voltage sources each in series with its own output impedance

For the charger to raise its output voltage , it must supply current , it can only raise its output voltage as a proportion of the its output impedance and the battery's impedance , its impedance is proportionally higher then the battery ( the usual case) then the limit of its voltage , " raising" is a function of the current it can supply , hence in bulk mode , the charger cannot raise the terminal voltage as the load impedance ( battery) is to low , so all it does is maximum power transfer.

As the battery impedance rises , the charger can attempt voltage regulation ,again the current that flows is PURELY a function of the battery impedance at that point in time for that voltage.

In float mode, since the charger can't sink current ( well few do ) , is does not have the ability to ' drag ' the battery voltage anywhere. All it can is reduce its output voltage within the confines of the proportions of the two equivalent impedances which causes a drop in charger current ( ie the charger reduces itself to a puny charger ) and the battery voltage , essentially of its own accord drops lower to the float voltage.

In this regard the charger is implementing current fold back. ( in this case it is effectively regulating current as it no longer controls voltage , the battery is doing that ) , as I said you can't independently regulate current AND voltage

Note the iota chargers are switched mode power supplies. , as are virtually all chargers on the market , that doesn't mean they use PWM charging methods ( I've not seen a charger that does, outside solar )switchers are just another means of regulating DC voltages. The output of such chargers are pure DC ( well and a little switcher ripple!) people seem to mix up this stuff

Note that switched mode is based on magnetic coupling , and POWER transference , which is what the duty cycle does. ( its not current per time per say )changing the duty cycle of a switched mode power supply causes more or less energy to be transferred between the input and output stages. In essence making it a bigger or smaller voltage source. Linear regulators on the other hand get rid of the excess power through heat ,

Why you guys want to know this is beyond me though

Ps if you get the difference between current and voltage sources , you will realise why you can happily short circuit a solar panel and not a big battery !!! ( yet both are power sources )

Dave

[roetter]

I believe one more condition should be considered with respect to the questions of "when is the battery full or 80% full or whatever number?"

The size of the charger with respect to the capacity of LA batteries.

Say you have 1000 Ah 12V LA batteries sitting at 50% SOC. The chargers are set to 14.6V absorption voltage.

Case 1: 500A charger - C/2: the charge voltage will be at 14.6V immediately and the charge current will be constantly going down. We are in absorption mode from the first second. Result - the batteries are still at 50% of charge even though the charger already went into absorption mode.

Case 2: 10A charger - C/100: the charge voltage will be somewhere near 13V and very very slowly rise. A few days later we reach 14.6V the batteries will be near 99% full.

However, once the large 500A charger will have dropped to 10 A ( if not timed out of absorption) the batteries would be at the same SOC " near 99%" full.

So there could be a good relationship of rate of charge (C/n) at a given voltage and SOC for LA batteries. I guess these number would vary a little bit depending on brand, state of sulfation, etc. but could be helpful for users of generators.

A table could look like this:
For a charge voltage 14.6V
SOC
C/20 80%
C/40. 85%
C/60. 90%
C/80. 95%
( These are fictitious numbers only!)

Any body care to try to do some research?

[sailinglegend]

Originally Posted by Don L

When my solar controller goes into absorption around noon on a sunny day at 14.6V the batteries are accepting around 3-4 amps (460 AH bank) and my 290W panel is only putting out around 7 amps.....

The definition of fully charged is usually 0.5% of your battery capacity - that should be 2.3 amps if your actual capacity is really still 460Ah - they could be very much lower if old. So your battery is taking more charging current than if it were full - BUT - is it just taking all the solar controller can give it. You only have 7 amps coming from the panel - the rest is going on boat loads.

Try a simple test next time at noon as soon as you hit absorption and turn on the main engine to charge the batteries - just for a few minutes at a sensible revs, and see if a much higher current will go into the batteries. If it goes up significantly because the alternator has the power to generate more amps than the solar - then the batteries are nowhere need 100% charged.

[goboatingnow]

Originally Posted by roetter

I believe one more condition should be considered with respect to the questions of "when is the battery full or 80% full or whatever number?"

The size of the charger with respect to the capacity of LA batteries.

Say you have 1000 Ah 12V LA batteries sitting at 50% SOC. The chargers are set to 14.6V absorption voltage.

Case 1: 500A charger - C/2: the charge voltage will be at 14.6V immediately and the charge current will be constantly going down. We are in absorption mode from the first second. Result - the batteries are still at 50% of charge even though the charger already went into absorption mode.

Case 2: 10A charger - C/100: the charge voltage will be somewhere near 13V and very very slowly rise. A few days later we reach 14.6V the batteries will be near 99% full.

However, once the large 500A charger will have dropped to 10 A ( if not timed out of absorption) the batteries would be at the same SOC " near 99%" full.

So there could be a good relationship of rate of charge (C/n) at a given voltage and SOC for LA batteries. I guess these number would vary a little bit depending on brand, state of sulfation, etc. but could be helpful for users of generators.

A table could look like this:
For a charge voltage 14.6V
SOC
C/20 80%
C/40. 85%
C/60. 90%
C/80. 95%
( These are fictitious numbers only!)

Any body care to try to do some research?

This is not correct. The voltage will rise quickly to absorption levels IS because large amounts of current will have been pumped into the battery by the huge charger. ( leaving aside possible damage )

Equally just because the charger ' reaches ' absorption doesn't mean the big charger suddenly stops supplying current , as discussed endlessly , the battery determines the current flow.

So the big charger will bring the batteries ( and the SoC ) out of bulk far quicker then the smaller one and both will take the same time ( approx) in absorption.

Dave

[Exile]

As a practical vs. theoretical matter for us non-techies in the crowd, am I safe reaching the following conclusions based on what I've read thus far?

1. Charger size only influences the rate/speed of bulk phase charging, i.e. up to approx. 80%;

2. Regardless of whether the battery or the charger is making the decision, the amt. of current/amps the battery will accept is dependent on the amt. of resistance in the battery;

3. As long as the voltage from the charger exceeds the battery voltage at any given time, current/amps will flow into the battery, but only at a rate and in an amount that is controlled by the battery;

4. The primary benefit of a smart charger's ability to increase voltage during the absorption phase is to overcome the battery's internal resistance at a faster rate. (I think back here on the helpful water pressure analogy I read awhile back from MaineSail I think); and,

5. The danger of too high of a voltage at any phase of charging a battery is that the battery may transfer the current it cannot accept into heat, and this may result in gassing off or worse.

The good news is that there's no chance of my being pendantic. Tell me where I got it wrong -- best to look stupid once than to stay quiet and remain stupid forever.

[colemj]

Dave,

In a switch mode supply, how is voltage regulation achieved? My understanding from working with them is that the "on" part of the duty cycle puts energy into a transformer winding. The "off" part transfers that energy (current) into the load (battery in this case).

Voltage regulation is achieved by varying the duty cycle (switching frequency), hence the current stored in the coil (and thusly transferred to the battery).

My whole point is that regulators DO use current control. Given the work by Mr. Ohm, I can't see how they do not.

Yes, I agreed at the start that the battery only accepts the current it can (following Ohm's law). However, that is a strange way of looking at it in my book because the battery is externally forced into a voltage "box" that does not allow it to draw more current.

And that "box" is formed by controlling the current inside the charging source. Even though it is manifested as a voltage to the battery.

Hence, chargers do a lot of current manipulation to keep a battery at a point where it will only accept the current the charger is manipulating. Where am I going wrong with this?

As an aside, I don't think anyone is controlling voltage by zener stacks like Bill suggests (particularly at these currents) - which is why I brought up the zener-FET example that I think is more likely. So how does the zener-FET voltage control work without controlling the current through the collector-emitter? The voltage feedback control is the voltage on the base (gate) of the FET, isn't it? And isn't that from the load (battery)?

Mark