Low amps

Nuff

Hello everybody.
I live in Corfu, Greece and last year I installed a PV ststem as follows.

Two 190watt MC 12volt panels wired in series ie 190w and 24v
Connected with 4mm cable to controller 6metres away

One MPPT charge controller set to 175A/H 24v

4 x 6v 175A/H batteries wired in series ie 24v 175A?H
Connected via an rcd to the inverter 2metres away

One APC 1500 UPS
Output power capacity 1500 VA
Output power capacity 980 watts
Max Configurable Power 1500 VA
Max Configurable Power 980 watts
Nominal output voltage 230V

The load is always low so that aside for now asmy issue I believe is current/amps.
If I connect a generator to the batteries they charge well and hold their charge.
However using the PV array the batteries go flat quickly.
Charge controller reading for this week on mostly sunny days at around 10am before use were as follows.

Day Saturday Sunday Monday Tuesday Wednesday Thursday
Input V from solar 90v 84v 86v 80v 87v 83v
Input current from solar 0.8A 0.6A 1.6A 0.6A 0.9A 1.0A
KW input from solar 0.7Kw 0.04Kw 0.13Kw 0.04Kw 0.07Kw 0.07kw
Total KWH 329 330 330 330 331 331
Battery voltage 24.8v 25.0v 25.4v 23.8v 25.1v 23.4v
Current supplied to battery 1.4A 0.7A 4.0A 0.6A 1.7A 1.5

Can anyone tell me why the PV array isn't charging the batteries sufficently ?

Thanks,
Steve

BB.

Re: Low amps

Can you tell us more about the solar panels?

Two 190watt MC 12volt panels wired in series ie 190w and 24v

Specifically, the Vmp and Imp (voltage and current maximum power) at least.

Also, about the charge controller.

And, if you have a volt meter, can you measure the voltage at the battery bank and the output of the solar charge controller? It sounds like the solar charge controller "thinks" the battery bank is mostly fully charged.

-Bill

Cariboocoot

Re: Low amps

The input/output current from the panels is extremely low. I would expect to see 12 Amps from 380 Watts on an MPPT controller.

First suspect would be a bad connection on the panel wiring (assuming the panels are oriented properly and not shaded).
Second suspect would be a defective charge controller. This can be checked by bypassing the controller completely and seeing if the output current goes up (you need a DC clamp-on Ammeter to check this). What is the brand/model?
The Voltages from the panels look more like Voc than Vmp; as if the panels aren't getting connected to the batteries. Possibly a bad connection between the controller and batteries, or even the batteries are bad and simply won't respond to charging. Have you charged them from an alternate source? Are these flooded cells that you can check the specific gravity on?

westbranch

Re: Low amps

To ad a question or 2 to 'Coots list:
Is the path from the generator using the same connection to the batteries as the charge controller, that is do you use a common bus bar or are there 2 sets of connections 1 for CC and 1 for GEn?
have you checked all connections

Sound like there is something wrong between the PV's and CC for the input to be almost nonexistent...

Nuff

Re: Low amps

Bill,
Thanks for responding.

The solar panels are Risen 190S-M
http://www.risenenergy.com/PV_10.htm


The MPPT charge controller is this..
http://www.ebay.co.uk/itm/max-60a-1500w-output-mppt-solar-charge-controller-regulator-12v-24v-36v-48v-LCD-/140602461807?pt=AU_Solar&hash=item20bc8f4e6f
I have an analogue multimeter which reads as follows.
From PV to CC. Ohms 14
From PV to CC. DC Vma 70
From PV to CC. ACV 14
From PV to CC. AC10V 2.4

From CC to batt Ohms 50
From CC to batt Vma 20
From CC to batt ACV 4
From CC to batt AC10V 1.8

It's overcast today but I had the batteries on charge all day yesterday from the mains at a friends home and they all reached 6.2v to 6.3v and 25v total. They have been in place over night and today and are now back down to 24,2v.

Nuff

Re: Low amps

Thanks for your reply Cariboocoot,
There has been very little sun for days now but low amps has been evident even in strong sunshine so not sure about shade effect.
Incidentally should all PV be disconnected at night or in shade ? The controller does have reverse flow protection.

I will take a close look at the connections on the back of the panels.

The charge controller is here http://www.ebay.co.uk/itm/max-60a-1500w-output-mppt-solar-charge-controller-regulator-12v-24v-36v-48v-LCD-/140602461807?pt=AU_Solar&hash=item20bc8f4e6f

A friend is going to come around with a DC clamp and check the output having bypassed the controller so I'll feed back on the above later.

The specific gravity on the four 6v batteries was as follows.
117
118
113

119
114
118

120
121
120

114
115
115

Some cells are admitedly low but they have still held a charge when charged from the mains.

Steve

Nuff

Re: Low amps

Westbranch,
Thanks for your reply.
The battery and all controller connections are good but I will take a look at the PV connections too.
I have always charged the batteries via a different path from the controller to battery path. I connect a charger to the battery bank and plug directly into the generator.
To check the path I could use the CC path to the batteries or maybe replace the wiring completely from the PV to the controller and from the controller to the batteries ?
When my friend finally arrives with his clamp on connecter I will check the controller.

BB.

Re: Low amps

The only reading I want right now is DC Volts (AC volts is not useful, and I am not sure what DC Vma means--Appears to be milli amperes, do not measure amps with meter right now--It will be damaged if connected incorrectly to your circuit and mAmp scale is too low. Also do not use Ohms setting with a powered circuit, can damage meter).

It looks like your panels are rated Vmp~36.6 volts (voltage maximum power) and you have two panels in series (Vmp-array~73.2 volts?) and how many panels total?

Your array voltage should be somewhere around 70-90 VDC (volts direct current). Around 70 volts if the panels are "loaded" by the MPPT controller and around 90 volts if the MPPT controller is not taking any power.

Day Saturday Sunday Monday Tuesday Wednesday Thursday
Input V from solar 90v 84v 86v 80v 87v 83v
Input current from solar 0.8A 0.6A 1.6A 0.6A 0.9A 1.0A
KW input from solar 0.7Kw 0.04Kw 0.13Kw 0.04Kw 0.07Kw 0.07kw
Total KWH 329 330 330 330 331 331
Battery voltage 24.8v 25.0v 25.4v 23.8v 25.1v 23.4v
Current supplied to battery 1.4A 0.7A 4.0A 0.6A 1.7A 1.5

The solar voltages near 90 VDC would indicate that the MPPT Charge controller is not loading the solar array.

The battery voltage, if when the sun is up and there are no loads, indicate not very much charging current.

While the battery is "charging" what is the exact voltage at the battery bank terminal (i.e., 24.8 volts) and the exact voltage on the Battery Output Terminals of the Charge controller (i.e., 25.1 volts or 29.0 volts, etc.)?

If you have too much voltage drop from the charge controller to the battery bank, the charge controller can get confused and not output very much current to the battery bank.

How long are the cables from the charge controller to the battery bank and what diameter is the wire?

You want to get the battery bank fully charged quickly... The more days the bank sits at less than ~75% State of Charge, the quicker the batteries will sulfate (go bad).

Do you have a back up AC Battery Charger and Utility or Generator power to recharge the bank?

-Bill

Cariboocoot

Re: Low amps

It's overcast today but I had the batteries on charge all day yesterday from the mains at a friends home and they all reached 6.2v to 6.3v and 25v total. They have been in place over night and today and are now back down to 24,2v.

This is another, albeit separate, problem; 25 Volts is too low for a 24 Volt system. The batteries should be brought up over 28 Volts and held there until the Specific Gravity has a chance to rise to proper levels.

If you are not getting charging performance from your PV you must get proper charging from some other source otherwise your batteries will soon be ruined.

Nuff

Re: Low amps

Thanks for your time Bill.
Analogue readings
PV to CC on 250DCV scale are 75VDC
CC to Batt on 50DCV scale are 23v
At the battery on 50DCV scale are 23V

CC readings
Input from solar scrolls up and down 61v to 87v
Input from solar 0.9A
Input power fron solar 0.06kw
Batt voltage 23v
Current supplied to batt 0.7A

I'm taking the batteries away for charging direct from the mains again as you suggest although they have lasted without the inverter low voltage alert kicking in over last three days.
Thanks again,
Steve

BB.

Re: Low amps

Sounds like issues with the charge controller... Either the controller is not programmed correctly (charging set-point should be around 29 volts DC, float voltage around 27 volts) or it is not working.

Does the charge controller say what it is doing (bulk, absorb, float, etc..)? Assuming the battery voltage at the controller is equal to the voltage at the battery bank (very little voltage drop on wiring from controller to battery bank), then the controller is simply not working correctly.

How long is the wire from the solar array to the charge controller, what diameter wire, and how many solar panels do you have?

At 23 volts, your batteries are near fully discharged... Lead acid batteries that sit below ~75% state of charge for days/weeks/months will "sulphate" and fail within a few months or a year. They need to get fully recharged to ~90-100% state of charge now to avoid further damage. Do you have a hydrometer so you can measure specific gravity?

Otherwise, poor electrical connections (dirty connections, using "battery clips", too long of wiring/too small of diameter of wiring, etc.) can also cause similar problems--But so far, your readings seem to be OK (related to wiring issues) between the battery and the charge controller.

You could still be having wiring issues between the solar array and the charge controller. "Input from solar scrolls up and down 61v to 87v" seems to be a problem. If the Vmp-array is dropping to 61 volts and you are not seeing more current, bad wiring connections or a damaged solar panel/array could also cause this.

Is the array in full sun and pointing to the sun around 12 noon? Solar panels do not work hardly at all if there is any shading on the panel (tree leaves, nearby pipe vents, power lines over head, in deep shade, etc.).

-Bill

Cariboocoot

Re: Low amps

As I said in Post #3, bypass the controller and see if the array pushes any current to the batteries.