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Old 20-04-2015, 02:56   #31
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Re: Solar panels direct to batteries??

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Originally Posted by boat_alexandra View Post
It's actually very slightly more efficient than using a controller because the controller consumes power.
The PWM controllers have very low self consumption. Good MPPT controllers often have much higher self consumption, but make up for this by using voltage conversion to extract more power from the panel than is possible from direct connection.

The real test for efficiency is how much power you can squeeze into the battery during the short daylight hours. Here any controller is much more efficient than direct connection during the absorption and float stages. The controller allows the battery voltage to be kept at the maximum that can be accepted without overcharging.

Direct connection only allows for a very crude voltage control even if you monitor things carefully. Thus with direct connection the voltage at times will be too low, leaving the battery at a lower SOC, or too high. Neither is optimum. A controller will maintain the battery voltage at the highest level it can reasonably accept and will adjust this continuously.

The drawback of not using a controller is inconvenience and shortened battery life. For most people the cost of the controller will be more than re-paid in savings on battery costs. If your battery costs are zero I can understand that using a controller makes far less sense, but this situation does not apply to most people.
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Old 20-04-2015, 08:32   #32
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Re: Solar panels direct to batteries??

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Originally Posted by jkindredpdx View Post
I didn't see anyone mention isolating... Isn't that necessary to separate your banks?
Isolating separate battery banks is what the good old 1/2/off switch is for however most of us have multiple batteries hooked like thus 2 6 volt in series to make 12 volts and several of these sets in parallel to make the ah size we want/ need. The other is to have several 12volt batteries in parallel to do that.
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Old 20-04-2015, 09:03   #33
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Re: Solar panels direct to batteries??

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Originally Posted by noelex 77 View Post
The PWM controllers have very low self consumption. Good MPPT controllers often have much higher self consumption, but make up for this by using voltage conversion to extract more power from the panel than is possible from direct connection.

The real test for efficiency is how much power you can squeeze into the battery during the short daylight hours. Here any controller is much more efficient than direct connection during the absorption and float stages. The controller allows the battery voltage to be kept at the maximum that can be accepted without overcharging.

Direct connection only allows for a very crude voltage control even if you monitor things carefully. Thus with direct connection the voltage at times will be too low, leaving the battery at a lower SOC, or too high. Neither is optimum. A controller will maintain the battery voltage at the highest level it can reasonably accept and will adjust this continuously.

The drawback of not using a controller is inconvenience and shortened battery life. For most people the cost of the controller will be more than re-paid in savings on battery costs. If your battery costs are zero I can understand that using a controller makes far less sense, but this situation does not apply to most people.
That point can not be over-stressed. No human intervention can regulate voltage as effectively as a voltage regulator. Voltage also needs to be held high enough, for long enough, but not too high, to deliver a healthy absorption charge. If you are turning it off at 14.8V then letting it decay a bit, then turning it back on, this is not an efficient means of regulating the voltage and even a cheap water-proof shunting controller would do better than a human could. A PWM controller, in absorption or float, will turn on/off thousands of times for every human on/off thus holding voltage at the max safe level for the longest duration possible fighting off sulfation and preventing over charging and plate/grid erosion..

Having seen numerous expensive banks destroyed by controller-less solar I say go for it, so guys like me get to fix your system..
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