[3889]
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I believe that my batteries will only achieve about 80% charge off a standard alternator. Is this limit the same when trickle charging off a small solar panel or shorepower; is a smart charger the only way to maximise charge?
Achieving 100% battery charge.
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Pye_End
Well-Known Member
Yep. Smartcharger of some description. Can buy gadgets to put on your alternator circuit to fool the system into doing the same job, if you use your diesel enough, or buy a 4 stage 240v charger.
Not sure about changing with solar. It gives a fairly high voltage but unless you have a fair amount of them it may not top a battery all the way up. Don't know if you can get a 'smart' box for solar/wind etc. I am sure somebody will be along shortly to confirm/deny this!
Not sure about changing with solar. It gives a fairly high voltage but unless you have a fair amount of them it may not top a battery all the way up. Don't know if you can get a 'smart' box for solar/wind etc. I am sure somebody will be along shortly to confirm/deny this!
VicS
Well-Known Member
The no load voltage from a solar panel is high enough, without a regulator, to fully charge a battery. Obviously that depends on the battery size and the panel size but a 5watt panel fully charges a 45 Ah battery. I imagine though that if the panel output is controlled with a regulator, which you would have with larger panels, then it probably will not. No such thing as a "smart regulator" for solar panels afaik. The answer perhaps is to have a small enough panel not to require a regulator in addition to a larger regulated one.
dulcibella
Well-Known Member
Nothing in the real world manages 100% of theoretical performance. A smart charger should get you to 90%
alan
Well-Known Member
Just for information:
This company makes (acording to them) a solar regulator that: Boosts, Equalizes and Float charges. As it's German, and not cheap, then it should be good!
www.stecasolar.com
Alan.
This company makes (acording to them) a solar regulator that: Boosts, Equalizes and Float charges. As it's German, and not cheap, then it should be good!
www.stecasolar.com
Alan.
andy_wilson
Well-Known Member
The alternator will do a bit better than that on a long run, they charge at up to 14V. It's just that the last 10% takes an age at that charging voltage.
I have a 20W solar panel connected directly to each battery. The panel is placed in the cockpit when the boat is unused, so recieves very limited direct sun, and they are a bit dirty too when I return to the boat.
Battery voltages are always over 13V when tested (one is better than the other as my wife gave it death last summer).
I have a 20W solar panel connected directly to each battery. The panel is placed in the cockpit when the boat is unused, so recieves very limited direct sun, and they are a bit dirty too when I return to the boat.
Battery voltages are always over 13V when tested (one is better than the other as my wife gave it death last summer).
rogerthebodger
Well-Known Member
this solar regulator claims 4 stage (Bulk/PWM/Boost/Float) type
William_H
Well-Known Member
you are probably overly worried about fully charging your battery however...
Any charger which is not regulated will fully charge a battery however depending on the current of the charger it may also overcharge the battery.
So as stated a solar panle will just keep on pumping current into the battery regardless of charge level. If this current is small then no problem but it will fill the battery right up.
A small plug pack type transformer rectifier giving around 15 volts no load will also do the same thing without killing the battery. You may bneed to fit a resistor to limit the current however otherwise a fat battery could melt the transformer. don't use the modern switch mode type plug pack power supply as they try too hard to amintain a regulated voltage. You want the transformer type which tries to produce a higher voltage but sags a lot with current drain.
Another approach is to use an old unregulated battery charger on shore power. Fit a resistor so that current is limited. ie 3 ohm resistor will drop 3 volts at 1 amp or better a 10 ohm resistor will drop 2 volts at 1/5 amp. The dropping of the voltage will I guess limit your charge current to 1/5 amp which most battery banks can handle long term in overcharge without damage. make sure resistor is rated at several watts. olewiill
Any charger which is not regulated will fully charge a battery however depending on the current of the charger it may also overcharge the battery.
So as stated a solar panle will just keep on pumping current into the battery regardless of charge level. If this current is small then no problem but it will fill the battery right up.
A small plug pack type transformer rectifier giving around 15 volts no load will also do the same thing without killing the battery. You may bneed to fit a resistor to limit the current however otherwise a fat battery could melt the transformer. don't use the modern switch mode type plug pack power supply as they try too hard to amintain a regulated voltage. You want the transformer type which tries to produce a higher voltage but sags a lot with current drain.
Another approach is to use an old unregulated battery charger on shore power. Fit a resistor so that current is limited. ie 3 ohm resistor will drop 3 volts at 1 amp or better a 10 ohm resistor will drop 2 volts at 1/5 amp. The dropping of the voltage will I guess limit your charge current to 1/5 amp which most battery banks can handle long term in overcharge without damage. make sure resistor is rated at several watts. olewiill
MichaelHomsany
Active Member
Hi,
Virtually any charge source greater than the nominal battery voltage will fully charge your battery, the issue is how long it will take.
Reference the piccie at www.bebi-electronics.com/current_voltage_curve.gif . The
C/something figure is the charge current, expressed as a % of the capacity of the battery. IE, a 200 a/h battery, C/10=20 amps
Although the voltages shown on the curve are for a single cell, you can multiply x6 for a 12 volt battery.
When a battery charges, the 'bulk' phase is the steep part of the curve (from the left). The limitation is really the amount of current the source can supply and what the batteries will really accept.
At a pre-set point (usually around 14.2-14.4), the regulator begins to voltage limit. (the heavier horizontal line). As the charge level in the battery increases, the current will decrease, moving you slowly from the (for example) the C/5 to C/10, etc. This is usually called the 'acceptance' phase.
The issue is just how long all of this takes. From above, (and making the maths simple), if you charge at a rate of C/5, it will take 5 hours to charge, C/10, 10 hours, etc.
What some of the smart chargers do is at a pre-set point, they switch into a current-limit mode and let voltage go to whatever it wants to be to speed up the full charge process. This is often called an 'equalization charge' .
Finally, the end of charge is recognized (often) by the slight dip in voltage.
The short of all of this is that it is much more input energy efficient to do most of your charging with your alternator, then let a lower current source, such as a solar panel, 'top up' the balance.
The other advantage is that you will limit out-gassing ('boiling') of the electrolyte by reducing the section of the curve that goes vertical.
Hope this helps. The whole subject is really as clear as mud, and really isn't a solvable problem over the long term.
(And we don't sell charge regulators, either!)
Best regards,
Michael
Virtually any charge source greater than the nominal battery voltage will fully charge your battery, the issue is how long it will take.
Reference the piccie at www.bebi-electronics.com/current_voltage_curve.gif . The
C/something figure is the charge current, expressed as a % of the capacity of the battery. IE, a 200 a/h battery, C/10=20 amps
Although the voltages shown on the curve are for a single cell, you can multiply x6 for a 12 volt battery.
When a battery charges, the 'bulk' phase is the steep part of the curve (from the left). The limitation is really the amount of current the source can supply and what the batteries will really accept.
At a pre-set point (usually around 14.2-14.4), the regulator begins to voltage limit. (the heavier horizontal line). As the charge level in the battery increases, the current will decrease, moving you slowly from the (for example) the C/5 to C/10, etc. This is usually called the 'acceptance' phase.
The issue is just how long all of this takes. From above, (and making the maths simple), if you charge at a rate of C/5, it will take 5 hours to charge, C/10, 10 hours, etc.
What some of the smart chargers do is at a pre-set point, they switch into a current-limit mode and let voltage go to whatever it wants to be to speed up the full charge process. This is often called an 'equalization charge' .
Finally, the end of charge is recognized (often) by the slight dip in voltage.
The short of all of this is that it is much more input energy efficient to do most of your charging with your alternator, then let a lower current source, such as a solar panel, 'top up' the balance.
The other advantage is that you will limit out-gassing ('boiling') of the electrolyte by reducing the section of the curve that goes vertical.
Hope this helps. The whole subject is really as clear as mud, and really isn't a solvable problem over the long term.
(And we don't sell charge regulators, either!)
Best regards,
Michael
