low output from charge controller

[almac]

using this cc.. http://www.australianwindandsolar.com/MP3735_Manual.pdf

the input to the batteries is often low, for example, panel output would be 32v x 15amps = 480w. the output to the batteries would be 29v x 5amps = 145w . the batteries are at 75%. they are 250ah at 24v,what could be the problem? when i connect the dc charger via the gen the batteries will take 40amps + at 14.4v. arranged in a 12v 500ah config of course.

[Mike90250]

hmmm. I can't tell if you are running 12V or 24V. You may have a "counterfeit" controller, that "says" MPPT, but it is not actually, most folks can't tell the difference, but you may have caught them at it.

When the controller is outputting low amps, try turning on a substantial load, and see if the controller produces more power as the battery voltage sags. It may be that the bulk stage of the charge is done, and you are in Absorb.

[inetdog]

hmmm. I can't tell if you are running 12V or 24V. You may have a "counterfeit" controller, that "says" MPPT, but it is not actually, most folks can't tell the difference, but you may have caught them at it.

When the controller is outputting low amps, try turning on a substantial load, and see if the controller produces more power as the battery voltage sags. It may be that the bulk stage of the charge is done, and you are in Absorb.

And perhaps with the Absorb voltage set too low?

[almac]

hmmm. I can't tell if you are running 12V or 24V. You may have a "counterfeit" controller, that "says" MPPT, but it is not actually, most folks can't tell the difference, but you may have caught them at it.

When the controller is outputting low amps, try turning on a substantial load, and see if the controller produces more power as the battery voltage sags. It may be that the bulk stage of the charge is done, and you are in Absorb.

thanks for the reply, im running 24v with the CC. battery bank is 250ah 24v. the CC has a "bulk" charge stage and a "float" stage. no absorb stage, if it has an absorb stage it doesnt tell you its in absorb. it just says "bulk". the low output is in the "bulk" stage. if i run a load on the batteries it does sometimes kick up the output to closer what the panel input is. so if the panels are putting out 15amp and i place a load on the batteries , the cc might put out 14amps for a short time. , i figured out its not a MPPT a while ago. it never comes anywhere near to putting out the wattage it receives from the panels.

[thastinger]

Seems you should reconfigure your panels to provide higher voltage at less amps. Most CC operate most efficient with a voltage at least twice the battery bank. Your CC will have an efficiency curve posted on a website somewhere.
What you describe with the battery charging is normal, the part where the amps trail off when the battery is close to charged up anyways, whether you have the proper voltages programmed into the CC you haven't said.

[Sunking]

panel output would be 32v x 15amps = 480w. the output to the batteries would be 29v x 5amps = 145w .

Impossible violates the Laws of Physics. It is impossible to have 480 watts Into the controller and only 145 watts outs. Your measurements have to be either wrong, making it up, or your controller is a Hot Plate made for cooking.

Now 480 in and 460 out is a real number meaning your controller is 95% efficient and burning 20 watts of waste heat, but if you really had 480 in and only 145 out your controller would be on fire burning off 335 watts. You have to be doing something wrong or leaving something out.

[Mike90250]

Impossible violates the Laws of Physics. It is impossible to have 480 watts Into the controller and only 145 watts outs. Your measurements have to be either wrong, making it up, or your controller is a Hot Plate made for cooking.

Now 480 in and 460 out is a real number meaning your controller is 95% efficient and burning 20 watts of waste heat, but if you really had 480 in and only 145 out your controller would be on fire burning off 335 watts. You have to be doing something wrong or leaving something out.

He's likely saying "I have 480 watts of panels and 145watts of charging".

[Sunking]

He's likely saying "I have 480 watts of panels and 145watts of charging".

Perhaps I can only take him at his word when he said:

panel output would be 32v x 15amps = 480w

If that is true and he has a PWM controller then he would see 31 volts @ 15 amps on the output. If MPPT them would be 16.5 amps at 29 volts.

Now if he assumed he had 32 volts @ 15 amps on the input, and measured with 29 volts at 5 amps, he made an error because he did not measure the input. Thus why I say it is impossible and he had to make an error.

Most likely he just assumed 485 watts. At 29 volts tells me he is already passed 100% SOC and in over charge or EQ. You know what I know Mike, Power does not vanish, the equations have to = 0. Otherwise you believe in Santa Clause, Free Energy, and Perpetual Motion.

[almac]

Perhaps I can only take him at his word when he said:



If that is true and he has a PWM controller then he would see 31 volts @ 15 amps on the output. If MPPT them would be 16.5 amps at 29 volts.

Now if he assumed he had 32 volts @ 15 amps on the input, and measured with 29 volts at 5 amps, he made an error because he did not measure the input. Thus why I say it is impossible and he had to make an error.

Most likely he just assumed 485 watts. At 29 volts tells me he is already passed 100% SOC and in over charge or EQ. You know what I know Mike, Power does not vanish, the equations have to = 0. Otherwise you believe in Santa Clause, Free Energy, and Perpetual Motion.

thanks for the replies, now i will get rid of the assumptions. i measured the input from the panels at the end of the cable to the CC. 15amps at 32v = 480w. my panels are 3 x 250w panels =750w. its winter here often cloudy so when i took the readings it was a panel INPUT of 32v at 15amps =480w. the CC was providing 5amps at 28.8v =about 145w , the hydrometer readings on my 24v 250ah battery bank put them at 75%. SG 1.225. when i put the batteries on the dc charger off the gen, takes full charge 40amps on a 14.4v charge with the batteries reconfiged for 12v 500ah

[Sunking]

thanks for the replies, now i will get rid of the assumptions. i measured the input from the panels at the end of the cable to the CC. 15amps at 32v = 480w. my panels are 3 x 250w panels =750w. its winter here often cloudy so when i took the readings it was a panel INPUT of 32v at 15amps =480w. the CC was providing 5amps at 28.8v =about 145w

OK so what is RED HOT and GLOWING in the dark?

Power cannot vanish, where is it going?

[almac]

Impossible violates the Laws of Physics. It is impossible to have 480 watts Into the controller and only 145 watts outs. Your measurements have to be either wrong, making it up, or your controller is a Hot Plate made for cooking.

Now 480 in and 460 out is a real number meaning your controller is 95% efficient and burning 20 watts of waste heat, but if you really had 480 in and only 145 out your controller would be on fire burning off 335 watts. You have to be doing something wrong or leaving something out.

if this is the case with all CCs what do they do with the energy when the batteries are full??

[inetdog]

if this is the case with all CCs what do they do with the energy when the batteries are full??

Very very simple: They do not take it from the panels in the first place!
A solar panel will be perfectly content to sit in full sun with an open circuit, not producing any electricity and just getting a little hotter over its entire area from the absorbed solar radiation. Or it will happily produce half of the Imp number at a voltage somewhat above Vmp. The load would then get about half the available panel power, and an MPPT CC would feed most of that to the battery, in form of higher current at the lower battery voltage.
It is the combination of high terminal voltage at the input of the CC and low battery voltage at the output of the CC with the same current on both sides that tells you that the CC is dissipating the missing power somewhere.

[almac]

OK so what is RED HOT and GLOWING in the dark?

Power cannot vanish, where is it going?

where does it go when the batteries are full?

[almac]

Very very simple: They do not take it from the panels in the first place!
A solar panel will be perfectly content to sit in full sun with an open circuit, not producing any electricity and just getting a little hotter over its entire area from the absorbed solar radiation. Or it will happily produce half of the Imp number at a voltage somewhat above Vmp. The load would then get about half the available panel power, and an MPPT CC would feed most of that to the battery, in form of higher current at the lower battery voltage.
It is the combination of high terminal voltage at the input of the CC and low battery voltage at the output of the CC with the same current on both sides that tells you that the CC is dissipating the missing power somewhere.

in my case the input voltage from the panels is 32v, the output voltage to the batteries is 28.8v. not much difference. its the current that is much less. 15amps in 5 amps out, maybe my CC is not taking that spare 10amps. i took the reading on the cable out of the solar panels b4 the cc

[Sunking]

in my case the input voltage from the panels is 32v, the output voltage to the batteries is 28.8v. not much difference. its the current that is much less. 15 amps in 5 amps out, maybe my CC is not taking that spare 10amps. i took the reading on the cable out of the solar panels b4 the cc

Where is it going? Again power does not vanish. Where that power is going is generating a whole lot of heat, enough it would burn up your controller unless you put a pot of water on it to boil and keep cool.

I still suspect operator error, because if you really had 480 watts going in, and only 145 going out, that missing 335 watts would cause your controller to burst into flames in a very short period of time being burnt off as waste heat. 335 watts of resestive heat = a 1150 BTU burner about the size of a small camp stove burning alcohol to make a pot of coffee.