The 2% criteria relates to max current at initial charge and you know as the battery charges the voltage differential deminishes thus reducing current flow at full charge to little or no current. Chief
Solar panels
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MS: Obviously the 2% criteria relates to max current at initial charge and you know as the battery charges the voltage differential deminishes thus reducing current flow at full charge to little or no current. All the info above only substantuates the fact that reaching full charge relegates the DC differential to equal and only repeats what I said in the first place, only with much verbage. You can argue all you want but I know what documents to read and believe, so enough of this! My info is correct when not misconstrued. Chief
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The only way current diminishes is with with CC-CV (constant-current to constant-voltage) charging (eg: a solar controller or voltage regulated trickle charger)...
CC, like many older "trickle chargers" just continues to push the same current and battery voltage will increase until the battery is destroyed.
If you watch the solar over-charge video you will see that the 220Ah bank is pushed in excess of 15V while the solar panel is putting out its max constant current it can produce for the irradiance it is getting. If you continue to supply CC to a battery the voltage has to go up. As voltage goes up the current that can flow into the battery also increase until we hit a point where the voltage stops climbing. The problem is this is a current that is MUCH, MUCH lower than folks incorrectly assume it is...
Take a bench top power supply, connect it to a 100Ah battery, and set it to 2A. Now set the voltage at 30V and let us know what happens to the battery voltage... You've now created a 2A constant-current charge source with no voltage regulation..(wink)
MS: You make to many conditions on your examples. Equal E to Equal E application between 2 sources presents no I! Much presentation online does not necessarily make you correct. All solar panels do not need controllers!
Chief, Elect. Eng.
Chief, Elect. Eng.
Nothing is being misconstrued and you can even witness everything I am saying on video.
You simply don't appear to understand the difference between CC (constant current) and CC-CV (constant-current to constant-voltage) charging and what "over-charging" a battery means in terms of voltage. Once a battery is full it needs drop to a float voltage or have charging terminated.
Having no solar controller is CONSTANT CURRENT charging and can eventually over charge the battery even batteries MUCH larger than most folks assume..
"Deka/ East Penn:
Use only “voltage-regulated” or “voltage-limited” chargers.
Standard constant current or taper current chargers must not be
used."
Unregulated solar is "constant current".
This should help..
MS: Your video doesn't work right now. Answer this simple question: does current flow between 2 equal voltages? Chief
I never said anywhere that "all solar panels" require solar controllers. What I have continually said is that any panel worth buying, that is capable of actually charging the battery, (in a meaningful time frame) will require a solar controller if it is to be left UNATTENDED for periods of time.
Constant current charging can destroy batteries so PLEASE be very careful with no regulation.
Fixed the video link.
No it will not because voltage is your "pressure", as you well know. Unfortunately your question is not really relevant to this conversation so I don't get the point.
Unless you have a 12.73V solar panel (a fully charged rested voltage flooded battery) you do not have equal voltages and current will flow into the battery.
With a 12V (nominal) unregulated solar panel, that can produce an open circuit voltage of 17-19V, it will produce a constant current to the battery (based on the level of irradiance & wattage of course) .
None of this is damaging until the battery becomes "full". Once the battery is chock-full the excess current (the battery needs less current than the PV is delivering) will force the voltage to climb well in excess of the float voltage required by the battery, thus shortening its life or destroying it all together.
UNATTENDED is the key here! Long timeframes UNATTENDED is even better! I have controllers on my larger systems and use good battery chargers, so need no counciling. I used to teach this stuff! I am asserting concept, but have used large solar panels in the past without controllers but never unattended. I further use a DC powered Igloo cooler hooked directly to a 75 watt panel (no battery) and it has run faithfully for over 10 years! Chief, IE
just to clarify something about the way a solar panel works.. If you look at solar panel V vs I curves, you will see nearly a constant current from short circuit out to nearly the maximum power point voltage which is always significantly higher than battery voltage. In constant sunlight, a solar panel will look like a nearly constant current source. Take a panel and short it, you can measure some current level. Put the same panel on a six volt battery, you will measure nearly the same current. Or a 12 volt battery, still nearly the same current..
Im not what the point of this question is
Im not what the point of this question is
but it doesnt really apply to a solar panel directly connected to a panel. At a constant light level and temp, the panel will put nearly the same current into the battery regardless of the voltage of the battery. For a typical 12 volt panel, the current will never diminish even when the battery voltage gets up over 15 or 16 volts.
The 17 to 19 volts panel output is what drives most people crazy! They erronously percieve that same voltage is present when the panels are hooked to their battery bank. Realizing load concept for most people does not happen. I am done with this as we have done it before and results the same. Chief
What happens at night time with an unregulated solar panel? Will current flow form batteries to panel?
A typical boat battery would likely never attain max panel voltage because as we increase voltage the battery accepts more current, even a full battery, but this is very bad for the battery.. We can't over look what the video is showing.
220Ah Lifeline AGM Battery Bank -
*Charged to full with charge controller and 12W solar panel
*Solar controller removed and 12W panel left unregulated
*Battery voltage is now pushed to 15.1V with .72A of current flowing into it
*Once full this battery is experiencing excessive levels of daily over charging even with a 12W panel.
*Battery voltage should be regulated to 13.4V for this battery once current has dropped to 0.5% at 14.4V.
The reason the voltage stoped at approx 15.1V on this 220Ah bank is because with .72A, at that SOC, 15.1V is creating that much current acceptance. Voltage is pressure and as we increase it more current can flow into the battery. In this case MUCH, MUCH more than should be. If we raised the current to 1A (a 15W panel) voltage would go higher.
125Ah Flooded Battery
*Charged to full with charge controller and 12W solar panel
*Solar controller removed and 12W panel left unregulated
*Battery voltage is now pushed to 15.48V with .71A of current flowing into it
*Battery experiencing excessive levels of daily over charging.
*Battery voltage should be regulated to 13.6V for this battery. The switch from absorption voltage to float is to occur when charge current at absorption voltage ceases to drop by more than 0.1A in one hour. This tends to be at about 0.4% Ah capacity in tail current where the absorption to float transition needs to occur. In other words when the battery is accepting 0.32A at 14.6V it needs to be dropped to float voltage. The 12W panel was capable of continually driving upwards of .72A into the battery and this is why voltage hit 15.48V. Pushing the battery to 15.48V is an equalizing voltage essentially every day for 3-5 hours.
Equalize your batteries every day for 3-4 hours and see how they hold up...(grin)
The reason the voltage stopped at approx 15.48V on this 125Ah bank is because with .71A, at that SOC, 15.48V is allowing .71A of current acceptance. Voltage is pressure and as we increase voltage more current can flow into the battery. In this case MUCH, MUCH more current than there should be at 100% SOC. If we raised the current to 1A (a 15W panel) voltage would go even higher.
Unless it has a diode it can back feed. Many small panels these days, sub 20W, have a diode this 12W panel in the video does.
FWIW This one is my most recent unregulated solar overcharge..
A customer of mine who has a large power vessel also has a small center console he uses for Striper fishing. While I was working on his big boat he was lamenting that he can't seem to keep batteries in his center console for more than a season.
I told him I would stop by the next time I was in the anchorage and this is what I found. This was a 10W panel plugged directly into a 12V outlet under the center console, which then fed directly to the battery.
The day I swung by to check on his boat, it was about 10:15 am and a hazy but overcast day. Below was his battery voltage at 10:15 in the morning.... D'oh..
The battery could not pass a CCA test. When I checked in with the owner he had not used the boat for about 6 days when this photo was taken.
The battery was replaced, again, but this time a small & inexpensive PWM controller was installed. I used a Morningstar Sunsaver SS-6-12V, for about $38.00, and problem solved. The cost of this controller was less than half what he had been paying for each battery his unregulated solar panel had destroyed.
If you boat is left unattended, for periods of time, with no loads, then you will want a solar controller if your panel is actually capable of any meaningful charging of the battery. A Morningstar Sunsaver SS-6-12V will cost you about $38.00 - $42.00 or about 1/3 to 1/2 the cost of a destroyed battery..
There certainly are Cheaper Chinese controllers that will cost you less but I have seen too many of these fail and some have even caught fire. Morningstar however builds very good quality controllers and stands behind them.
A customer of mine who has a large power vessel also has a small center console he uses for Striper fishing. While I was working on his big boat he was lamenting that he can't seem to keep batteries in his center console for more than a season.
I told him I would stop by the next time I was in the anchorage and this is what I found. This was a 10W panel plugged directly into a 12V outlet under the center console, which then fed directly to the battery.
The day I swung by to check on his boat, it was about 10:15 am and a hazy but overcast day. Below was his battery voltage at 10:15 in the morning.... D'oh..
The battery could not pass a CCA test. When I checked in with the owner he had not used the boat for about 6 days when this photo was taken.
The battery was replaced, again, but this time a small & inexpensive PWM controller was installed. I used a Morningstar Sunsaver SS-6-12V, for about $38.00, and problem solved. The cost of this controller was less than half what he had been paying for each battery his unregulated solar panel had destroyed.
If you boat is left unattended, for periods of time, with no loads, then you will want a solar controller if your panel is actually capable of any meaningful charging of the battery. A Morningstar Sunsaver SS-6-12V will cost you about $38.00 - $42.00 or about 1/3 to 1/2 the cost of a destroyed battery..
There certainly are Cheaper Chinese controllers that will cost you less but I have seen too many of these fail and some have even caught fire. Morningstar however builds very good quality controllers and stands behind them.
Just a little more about the diode and night current from a solar panel.
If you connect a battery directly up to a solar panel with the correct polarity, the night current can be about 5% of the full day current. The night current discharges the battery (link if your curious where the 5% number came from http://electronics.stackexchange.co...des-short-circuit-or-source-of-power-dissipat ) 5% is significant especially in the winter when nights are longer. Night leakage is something to worry about.
I have only owned Genasun and Mornignstar controllers (both PWM and MPPT) but these have the function to isolate the panel at night built in to the circuit function. You dont need a diode if you use one of these controllers and I cant say for sure but its likely hard to find a controller that doesn't have the night isolation built in. Another reason to just use a controller, you dont need to worry about that diode.
If you have a small panel with the diode already built in, this does not affect the power to the battery if you use a PWM type controller.
However, if you have a MPPT controller (like the Genason), you are better off with a panel that does NOT have a diode built in. The reason is that when the panel is running, that diode will be forward biased which results in a voltage drop (could be .35 to .75 volts depending on the type diode). The diode has a voltage drop the MPPT controller now can NOT take advantage of and you will get maybe 2.5 to 4% more current to the battery using a panel that does not have a diode vs one that does.
If you connect a battery directly up to a solar panel with the correct polarity, the night current can be about 5% of the full day current. The night current discharges the battery (link if your curious where the 5% number came from http://electronics.stackexchange.co...des-short-circuit-or-source-of-power-dissipat ) 5% is significant especially in the winter when nights are longer. Night leakage is something to worry about.
I have only owned Genasun and Mornignstar controllers (both PWM and MPPT) but these have the function to isolate the panel at night built in to the circuit function. You dont need a diode if you use one of these controllers and I cant say for sure but its likely hard to find a controller that doesn't have the night isolation built in. Another reason to just use a controller, you dont need to worry about that diode.
If you have a small panel with the diode already built in, this does not affect the power to the battery if you use a PWM type controller.
However, if you have a MPPT controller (like the Genason), you are better off with a panel that does NOT have a diode built in. The reason is that when the panel is running, that diode will be forward biased which results in a voltage drop (could be .35 to .75 volts depending on the type diode). The diode has a voltage drop the MPPT controller now can NOT take advantage of and you will get maybe 2.5 to 4% more current to the battery using a panel that does not have a diode vs one that does.
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Turned over very slowly. Have successfully started engine using batt 1, then batt 2, then back to 1 several times.