Weird charging behaviour from my solar charge controller

[23rdTheorem]

I have a 50A Firestar PWM drawing solar energy from a 550W PV panel and charging a 12v 200Ah gel battery. I'm experiencing a terrible charging rate. On a clear day, the charge controller is only charging the battery at 12-13V and no more than 9A but when I check the PV voltage with a multimeter I'm getting 48V. Is this normal or could there perhaps be something wrong with the charge controller settings?

Charge controller:

 

[TheChamp]

That's why it's called a PWM, it's inefficiency is a feature, not a bug.

 

[leon.davibe]

A pwm charge controller draws the panel voltage down to battery voltage

So lets say the panel is a 72/144 cell 50v panel with a vmp of 44v then it will produce its max power at 44v x 12.5A = 550w (estimating its values)

So dragged down to battery voltage the most it would ever produce is 12v x 12.5A = 150w

If the battery is closer to full you will get more watts

So at 14v x 12.5A= 175w

I assume the 9A is because angle isn't perfect this time of year

With a pwm controller you actually want a panel with a voltage closer to battery voltage to get more of the watts you pay for

 

[leon.davibe]

It may however perform better than the correct panel would have performed early morning and late afternoon

As we normally get less than peak at those times anyway

ie it may get up to its peak output sooner and stay there for longer ,having a table-mountain type production curve with the voltage clipping peak production

 

[23rdTheorem]

A pwm charge controller draws the panel voltage down to battery voltage

So lets say the panel is a 72/144 cell 50v panel with a vmp of 44v then it will produce its max power at 44v x 12.5A = 550w (estimating its values)

So dragged down to battery voltage the most it would ever produce is 12v x 12.5A = 150w

If the battery is closer to full you will get more watts

So at 14v x 12.5A= 175w

I assume the 9A is because angle isn't perfect this time of year

With a pwm controller you actually want a panel with a voltage closer to battery voltage to get more of the watts you pay for

Thank you so much for your detailed response. I knew about the charge controller stepping down PV voltage to battery voltage but I had no idea that the current was maintained Do you by any chance think getting a MPPT would improve the charging rate because currently, my 12v/200Ah battery is basically unusable

 

[Speedster]

Thank you so much for your detailed response. I knew about the charge controller stepping down PV voltage to battery voltage but I had no idea that the current was maintained Do you by any chance think getting a MPPT would improve the charging rate because currently, my 12v/200Ah battery is basically unusable

Not easier just to get a different panel?

 

[wingnut771]

Thank you so much for your detailed response. I knew about the charge controller stepping down PV voltage to battery voltage but I had no idea that the current was maintained Do you by any chance think getting a MPPT would improve the charging rate because currently, my 12v/200Ah battery is basically unusable

Yes, an mppt will fix everything.

 

[wingnut771]

Not easier just to get a different panel?

Link?

 

[Speedster]

Link?

Seems I was wrong. MPPT is cheaper than I thought.

Victron BlueSolar MPPT 75/15 Retail Solar Charge Controller

Ultra-Fast Maximum Power Point Tracking By constantly monitoring the voltage and current output of your solar (PV) panels, MPPT technology ensures that every drop of available power is rinsed out of your panels, and harvested for storage. The advantage of this is most noticeable when the sky is...

www.livestainable.co.za

 

[wingnut771]

Seems I was wrong. MPPT is cheaper than I thought.

Victron BlueSolar MPPT 75/15 Retail Solar Charge Controller

Ultra-Fast Maximum Power Point Tracking By constantly monitoring the voltage and current output of your solar (PV) panels, MPPT technology ensures that every drop of available power is rinsed out of your panels, and harvested for storage. The advantage of this is most noticeable when the sky is...

www.livestainable.co.za

Need a bigger one though for 550W. This is limited to 220W on 12V. Better to go for non-victron.

 

[wingnut771]

Just need to find one with the right starting voltage.

 

[wingnut771]

Something like this?

MPPT 12/24v DC 40A Solar Charge Controller + Bluetooth

MPPT 12/24v DC 40A Solar Charge Controller + Bluetooth 12V /24V Automatic System Recognition. Embedding Imported Advanced Microchips - Higher Monitoring Accuracy & Better Battery Protection.Advanced MPPT Technology With up to 99% high tracking efficiency, and Lithium-reawakening function.4 Deep...

solarwarehousesa.com

 

[leon.davibe]

Yea on the mppt just important to remember now the amps is battery charging amps so a 550w would max out at 45A on 12v and lower amps as the voltage go up

Now naturally the panel won't always push out its tested max as that is at 25c tested so in real world conditions you would likely get just under 500w and on cold days more

So the 40A will clip on those days and on hot days be just about able to handle the outeput

The lower voltage systems push up the amps so the items get pricey quick

On pwm controller you would look for around 30 cell panels if you wanna weigh up the options

 

[leon.davibe]

not going over 40A good idea since 0.2c is recomended for gel
so the 40A is perfect max