When Does Charging Voltage Start To Matter?

[Maine Sail]

Originally Posted by cwyckham

I always thought it was "chock" full.

You would be right... Always good to have a spell checker!

[senormechanico]

Misspelling "VOILA" has always been my pet peeve.
French, used to call attention, to express satisfaction or approval, or to suggest an appearance as if by magic.

Voilà - Definition and More from the Free Merriam-Webster Dictionary

"WaLa" is not a word.

Now back to your regular programming.

[cwyckham]

Originally Posted by Maine Sail

You would be right... Always good to have a spell checker!

Is a rate day that I can correct Maine Sail!

In this case, though, google says some Americans use Chuck full.

My personal favorite is kiwis who say that something is "chockers"

[hellosailor]

"what happens with voltage? "
When the supply voltage from the panels exceeds battery voltage, the batteries charge. And at night when the battery voltage exceeds that produced by the panels, the voltage flows back into the panels, heats them, and drains the batteries. Unless you have a blocking diode in the circuit.

Panel voltage under "no load" will always be much greater than when an actual load is hooked up, so static measurements with a typical high impedance (no load) multimeter can be deceiving unless there's a whole circuit with load hooked up.
With a typical "12" volt panel, the no-load voltage may reach 17-22 volts but with a hungry battery hooked up, that will usually drop to under 14.4 volts and if the panel's amperage is small compared to the battery capacity (like a 10W panel and a Group24 battery) no controller is needed in most situations. The problem is that the specifics of the battery, the loads, the panel output, all determine whether it is safe or not.
So unless you want to run the numbers and check up on things for a couple of weeks to be sure of them, a controller of some kind is a generally good idea.

Key words: "It depends."

The more power and voltage that the panels make, and the longer they may have to overcharge an unattended battery, the more risk. Did I mention "It depends" ?

[Maine Sail]

Originally Posted by cwyckham

Is a rate day that I can correct Maine Sail!

In this case, though, google says some Americans use Chuck full.

My personal favorite is kiwis who say that something is "chockers"

I think you meant rare day...

[cwyckham]

Originally Posted by Maine Sail

I think you meant rare day...

LOL. Yes sir, I did! Touché.

[sailinglegend]

Originally Posted by rebel heart

...What's the actual material impact of introducing something like a 30v potential with a low amperage?......what happens with voltage?

Nobody has really answered the 30v question. Two 12 panels in series will produce 30+ volts open circuit. Applying this voltage to a 12 volt battery is not a good idea. As others have said batteries take the current they want, but sitting with anything above 15 volts across them for a long time will cook them.

A friend in our marina connected his 12 volt solar panels to his NEW 4 X 6v Trojans in a 12 volt bank. BUT he connected the solar across one of the 6v batteries and when that cooked he did the same across one of the 6v batteries in the second pair of Trojans!!!!!!

It never ceases to amaze me what some people do.

[noelex 77]

Originally Posted by sailinglegend

Nobody has really answered the 30v question.

The voltage is not very relevant. With the limited current output of the wind/water generator that RH mentions ( less than an amp) the battery voltage (and the source voltage) will be much lower than 30v when connected to to a large battery bank.

There is very little danger of damage to the batteries given the parameters mentioned, but removing the wind/water generator would be a good idea for times when there is zero load on the batteries for a long period of time, such as when the boat is in storage, especially if other charge sources are connected such as solar, or a battery charger even if these are regulated. The self discharge may not be enough to prevent mild overcharging in these conditions.

A simple on/off switch is often not suitable to stop the output as the generator will speed up to damaging levels when the electrical load is removed. Locking the blades (or turning it at right angles to the wind) is a better idea, but these steps should very rarely be needed with such a small output in relation to battery bank size. When using the boat normally no regulation should be necessary.

[folivier]

Originally Posted by senormechanico

Misspelling "VOILA" has always been my pet peeve.
French, used to call attention, to express satisfaction or approval, or to suggest an appearance as if by magic.

Voilà - Definition and More from the Free Merriam-Webster Dictionary

"WaLa" is not a word.

Now back to your regular programming.

And neither is viola, or guage, or congradulations......

[goboatingnow]

Originally Posted by hellosailor

"what happens with voltage? "
When the supply voltage from the panels exceeds battery voltage, the batteries charge. And at night when the battery voltage exceeds that produced by the panels, the voltage flows back into the panels, heats them, and drains the batteries. Unless you have a blocking diode in the circuit.

Panel voltage under "no load" will always be much greater than when an actual load is hooked up, so static measurements with a typical high impedance (no load) multimeter can be deceiving unless there's a whole circuit with load hooked up.
With a typical "12" volt panel, the no-load voltage may reach 17-22 volts but with a hungry battery hooked up, that will usually drop to under 14.4 volts and if the panel's amperage is small compared to the battery capacity (like a 10W panel and a Group24 battery) no controller is needed in most situations. The problem is that the specifics of the battery, the loads, the panel output, all determine whether it is safe or not.
So unless you want to run the numbers and check up on things for a couple of weeks to be sure of them, a controller of some kind is a generally good idea.

Key words: "It depends."

The more power and voltage that the panels make, and the longer they may have to overcharge an unattended battery, the more risk. Did I mention "It depends" ?

Just remember unlike batteries which are voltage sources , panels are primarily current sources. In a pv panel the output voltage is a function primarily of current flow. In a voltage source the current is a function of voltage. So a pv panel is a high impedance source and a battery is a low one ( all relative )

A pv panel there're is not like say a small main battery charger even if people talk like they are.

Dave

[sailinglegend]

Originally Posted by noelex 77

The voltage is not very relevant....

The point I should have made more clearly is that it is voltage that kills batteries not current.

Too little voltage - disconnecting panels at 14v - will undercharge them, and too much voltage, 15+v for too long - will overcharge them.

Undercharging is the main reasons batteries get murdered.

[noelex 77]

Originally Posted by sailinglegend

The point I should have made more clearly is that it is voltage that kills batteries not current.

True, but it's battery voltage, not the open circuit voltage of the source.

A source capable of less than one amp will not raise the voltage of 500 AHr battery bank to 15+ V when the boat is being used normally, despite being capable of producing a very damaging 30+ V when connected to much smaller battery. The low charge current relative to the battery size is the dominant factor.

Originally Posted by sailinglegend

Undercharging is the main reasons batteries get murdered.

[Maine Sail]

Originally Posted by sailinglegend

The point I should have made more clearly is that it is voltage that kills batteries not current.

Too little voltage - disconnecting panels at 14v - will undercharge them, and too much voltage, 15+v for too long - will overcharge them.

Undercharging is the main reasons batteries get murdered.

That is correct, but, you need current to get battery terminal voltage up. A 1A source will need to get the battery bank to pretty much chock-full (got it right that time) before it can get the voltage to creep above 14.4V.

Without current, in the described situation, you won't have dangerous voltages and it will not be until the battery has been fully, fully charged that the voltage could even begin to creep up..

Can this happen if left unattended and charging continuously at 1A? Yes, it could depending upon the bank size, but with a small 1A hydrogenerator leaving it "unattended" is not really an option like it is with solar, and you will have other loads on while sailing thus nullifying any real charging to 100% SOC where voltage creep would occur......

[Opie91]

Originally Posted by rebel heart

I've been toying around with some small wind and water generator stuff. And by small I'm talking peak ~1amp @30 volts kind of stuff. Cheap motors, easy to work with, if they break you're out $20 and an afternoon.

Any pics of this $20 wind generator?

[Celestialsailor]

I imagine you will have to use a diode, so it does not act as a motor.