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unyalli · 08-13-2017, 07:15 PM

I had a 225 amp hour battery bank that was fully charged. Are you with me?

I hooked up an advanced 200 watt solar charging system to this battery Bank and saw nothing happened. I was dismayed. Electrical engineers will understand why this happened for the rest of us...

Why was my solar system not pushing power into these batteries?

As a solar controller I have 200 Watts of solar power available to me. I cannot DRAW this 200 watts of power from these panels if I don't have somewhere for it to go. If my battery Bank is demanding 200 watts or more from me I now have a place to dump this power and will draw this power from my solar array. Power is not pushed it is pulled.

unyalli · 08-13-2017, 07:34 PM

Correct

vsheetz · 08-13-2017, 07:38 PM

The batteries are fully charged. You expected the PV system to charge the batteries even more than fully charged? Not going to happen...

unyalli · 08-13-2017, 07:40 PM

Precisely!

ByeTheWay · 08-13-2017, 07:40 PM

200 watts may seem like a lot. I started with 150 watts and thought I had all I needed. 200 watts under perfect conditions will yield 16.6666 amps. (Watts to amps (A) conversion calculator) You won't see much from your solar monitor unless your batteries are in Bulk stage. Your solar monitor which works off a shunt should tell you what is going into the battery bank at any given time. Until you get a bigger battery bank, the rest is just wasted.

Mr_D · 08-13-2017, 07:50 PM

I have 4 - 100 watt panels, that's about right to keep the batteries up and keep the home refer going and nothing else.

computerguy · 08-15-2017, 09:13 AM

Quote:

Originally Posted by unyalli

...advanced 200 watt solar charging system ...

What components did you have installed?
What did you expect to happen?
Prior responses are correct. More information will give you better information if you still need it.

Mudsock · 08-16-2017, 07:58 AM

Electrical engineers don't think about power being pushed or pulled. They think about it being dissipated. Power is not stored; energy is stored.

Engineers think about CURRENT flow in multiple loops with mesh analysis or multiple VOLTAGES at nodes separated by circuit elements with nodal analysis. Systems of equations are written using Ohm's and Kirchhoff's law. Linear algebra is used to solve the system of equations. That is circuit analysis.

In order for current to flow into the battery, the instantaneous voltage at the output of the controller (node A) must be greater than the terminal voltage of the battery (node B.) There is a circuit element, that limits the current between these two nodes. The circuit element may be nothing more than a wire resistance (R) measured in Ohms. The current into the battery (I) is equal to (Va-Vb)/R.

In a more than trivial circuit, there will be more than two nodes and branches. Similar simple equations are written for each current path between two nodes. It is very simple once understood. All the equations must be solved simultaneously. With nodal analysis, the system is solved to determine the nodal voltages. With large circuits, a computer program is often used. SPICE is the most well known. A VERY good free version (LTSpice) is available at the Linear Technology website. Sample circuits are provided to enable learning.

Even with a fully charged battery, there will be current flow into it if the voltage at the output of the charger is greater than the terminal voltage of the battery. Trickle charge, or float charge, involves a very small current driven by a small voltage difference between nodes. The small float charge is used to offset the battery's self discharge to keep the battery fully charged. If excessive voltage exists at the controller output, water will be boiled off. Overcharging a fully charged battery is not uncommon. Without a constant small current into a fully charged battery, it will not stay FULLY charged. That is due to self discharge.

The solar system does not push power. It feeds current which is driven by voltage difference. Voltage is electromotive force. The unit of force is the Volt. The unit of power is the Watt. The unit of current is the Ampere. Power is equal to volts times amps. Energy is power over a period of time. Energy can be stored. Battery capacity is rated in Ampere Hours (AH). The energy a battery can supply is power over a period of time, or battery Voltage times current in Amps multiplied by hours.

There is a drawing that visually explains Ohm's Law. A small guy named Volts pushes a guy named Amps through a tube. A guy pushing down on and compressing the tube is named Ohms. V= I x R. That applies in electrical circuits and in garden hoses. Water pressure is equivalent to Volts. Water flow is equivalent to current and friction is equivalent to resistance. A larger hose is directly equivalent to a larger diameter wire. That drawing well explains the law. Google Ohm's Law drawing.