Controller question please

Re: Controller question please

Battery= 12.4
AMPS= 24.8
watts= 210

Power = 12.4 volts * 24.8 amps = 307.6 watts

Which does not equal 210 watts... So, I am not quite sure what that means... Many charge controllers are only giving estimates of power output (10% to even 30% level of inaccuracies)--But they do math well.

In any case, if the battery is at 12.4 volts while receiving 25 amps--it is seriously discharged and needs a lot of recharging.

A typically battery charge controller can only tell you what its output power levels are (approximation). It is up to you to control the loads. Typically, you want to charge the batteries during the day (little in the way of loads) for power use at night.

Of course, you can use power during the day too--but you need to size the array/battery bank/loads such that you have sufficient power to fully recharge your battery bank on a sunny day (or two).

"Deficit Charging" a battery bank (never fully recharging) will knock years off of your battery bank's life.

Monitoring Specific Gravity with a hydrometer is a minimum requirement to ensure your bank is healthy. Installing a battery monitor can make life much easier.

-Bill

-Bill

Re: Controller question please

VanDeusen wrote: »

RIGHT now as I type the correct readings are:

battery 12.7

amps 10.5

watts 118

• Power = Volts * Amps = 12.7v * 10.5 amps = 133 watts

At least that is closer to 118 watts...

Power is what is going into your battery. You can also call it "amps" going into your battery since you know it is around 12 volts.

As a rough approximation, Lead Acid Batteries can be almost 100% "efficient" when you look at Amps and Amp*Hours...

I.e., if you take 10 amps for 2 hours out of the battery bank you have taken out 20AH (10amp*2hours=20Amp*Hours).

And, it will take ~20 AH to recharge it (say 5amps*4hours=20AH).

However, power wise, a battery bank is closer to 80% efficient. You draw power out at a lower voltage and recharge it at a higher voltage:

• 10 amps * 2 hours * 12.5 volts = 250 Watt*Hours supplied
• 5 amps * 4 hours * 14.5 volts = 290 Watt*Hours to recharge
• 250 wh / 290 wh = 0.86 = 86% efficient battery bank (rest went into heat/electrolysis--making hydrogen gas).

SO when I see these numbers what about the amps and watts do I need to be paying attention too? are the batteries being charged with 10.5 which is equivalent to 118watts?

Just trying to understand the readings.

Most people talk about battery bank capacity in Amp*Hours instead of Watt*Hours or KWH... Since your battery bank does not change voltage (i.e., a 12 volt bank)--You can look at Amps*Hours (current and time) to keep track of your battery bank's state of charge...

Otherwise, just multiply all of your readings by 12 volts--and start thinking in terms of Watt*Hours...

Either is correct--however when dealing with power sources (solar panels, generators, etc.) we tend to work in Watts / Watt*Hours to account for the losses in "processing" power...

For an off-grid solar system, from the Panel Rated Wattage through charge controller, battery bank, inverter, etc... We are looking at 52% efficiency or less... So, on a system level, the losses are real and need to be accounted for.

-Bill

Re: Controller question please

Good question--I honestly do not know what happens if the sun goes down before the controller finishes equalization.

My guess is that the controller will wait for XX days until it tries again. It cannot continue to equalize the next day because you probably took power out of the battery bank overnight and the controller needs to recharge the bank to 100% first before it can actually start an equalization cycle.

Battery manufacturers have different recommendations on how often to equalize... From every 3 weeks to ever 3-6 months between cycles.

For a flooded cell battery bank, you should equalize when the Specific Gravity between cells varies by more than 0.030 points.

Equalization does not really "regenerate" a battery to like new condition... What it does is "balance the cells" so that all cells are back to 100% state of charge when equalization is done. Over time, sometimes a few cells self discharge/etc. and their state of charge falls lower than the rest of the cells in the bank (you may have 5 cells at 100% state of charge and 1 cell at 80% state of charge in a 12 volt battery). That one cell now behaves as if it is not fully charged and will begin to sulfate sooner--and die sooner--if not brought back into 100% charge/balance with the rest of the cells.

Equalization actually overcharges the 5 cells (which are already at 100% state of charge) to bring up the one low cell to 100% too (in this example).

Equalization is actually very hard on a battery bank. Uses distilled water, can cause plate erosion, and positive grid corrosion (because of the "over charging"). You only want to equalize when equalization is needed. You do not want to equalize often and a lot just because--it will help kill the battery cells/bank eventually.

-Bill

Re: Controller question please

No, I would not recommend equalizing more often than once per month.

Since you have flooded cell batteries--you should get a hydrometer and measure/log all of the specific gravity readings. That will tell you when equalization is really needed--and how much you need to equalize (check the low cells every 1/2 hour--when the SG stops rising-then stop equalization).

Equalizing past the "stop rising SG point" is only damaging the battery bank.

-Bill