solar panel hooked directly to battery

MrWizard wrote:
'knock down' is not the right term

PWM means Pulse Width Modulation

the power is pulse on and off hundreds of time a second to maintain a set point voltage aka 14.?

the higher the battery voltage (state of charge) the shorter the on time of the pulse and the longer the OFF time between pulses

thats the simple basic straight forward explanation of the operation

Thanks for that explanation. So if I'm understanding correctly, the PWM may not be pulsing off much (or at all) when the battery voltage (and charge level) is very low. Interesting! I can see now why a direct charge (without controller) wouldn't be appreciably faster.

'knock down' is not the right term

PWM means Pulse Width Modulation

the power is pulse on and off hundreds of time a second to maintain a set point voltage aka 14.?

the higher the battery voltage (state of charge) the shorter the on time of the pulse and the longer the OFF time between pulses

thats the simple basic straight forward explanation of the operation

pianotuna wrote:
Hi,

The controller doesn't "knock down" the voltage when the battery is empty.

Well, I realize there are different controllers out there and they may work in different ways. But my Morningstar SG-4 has a stated PWM setpoint of 14.1V, so doesn't this mean that if the panel is sending higher voltage than 14.1, the SG-4 is reducing the voltage to 14.1? I'd read somewhere that MPPT controllers also reduce the voltage, but they somehow manage to send the same wattage and convert that extra voltage into more current (V*A=W so less volts means more Amps). And I thought I'd read a comment at one time that said a PWM controller loses (wastes?) this extra voltage when it steps the voltage down. This is partly why I was wondering if 17V can somehow push the charge into the battery faster than 14.1V would. Not that I'm planning to do it; like I said, it's academic... I'm curious to know how it works.

eb145 wrote:
If the battery is not fully charged, then connecting the panel directly to the battery will be fine for a while - until the battery voltage rises too high as stated earlier.

Ed

Ok, thanks.

If the battery is not fully charged, then connecting the panel directly to the battery will be fine for a while - until the battery voltage rises too high as stated earlier.

Ed

Hi,

The controller doesn't "knock down" the voltage when the battery is empty.

rexlion wrote:
Let me rephrase/refine my question. For a short time of charging a non-full (depleted) battery, would the direct connection at 16-17V charge the battery harmlessly, and would it charge more quickly than a panel with a controller that knocks the voltage down to about 14V?

yes,no

Let me rephrase/refine my question. For a short time of charging a non-full (depleted) battery, would the direct connection at 16-17V charge the battery harmlessly, and would it charge more quickly than a panel with a controller that knocks the voltage down to about 14V?

And we are going to keep testing you...you, rjxj!

LOL I read your post. Yes you could connect a panel directly to your battery IF you were monitoring the voltage and didn't go above about 14.8 for a wet or 14.4 for AGM. Was this a test? :)