Energy Matters Forums

[jaahn]

H Graeme (Harry)
Re reading some of the past posts I note you did buy some meters. And do have a clamp/multi meter. I would put a meter shunt into the 12v supply for the inverter so you can read the power drawn by it in these situations.
1 standby. what current does it draw when nothing is running off it. Important to find out how much is wasted.
2 startup current for each of the fridge and the freezer. You will have to stand and watch that carefully.
3 running current for each of them seperately and together.
4 how long does each run/off cycle last for each of them.
% what the battery voltage drop is in each of these situations with no solar charging.
This will give you some data to estimate how many amp hrs you use running the fridge and freezer using the inverter. Then you will know if you have enough or not enough or maybe almost enough.
Have you looked at the nameplate wattage for the two units. Compare this to the DC input wattage to the inverter for an estimate of the efficiency.
Jaahn

[harrydiculous]

Thanks Jaahn. I've printed that out.

I might add that if I can make any contributions to this group it is:- DON'T USE 12 VOLT. It might be OK for Caravans & small systems but the cost of cables, methods of connection including an ability to solder and just the difficulty of running thicker cables causes nightmares.

[harrydiculous]

I felt that I needed to remove & check all the battery cables as well as adding some circuit breakers to the system before I took the system further into the house & the Freezers & Fridge. (The specs on the Freezer may be on the back of the unit. Removing it presents some problems due to location.. I can't find any online either. I can check on draw using a meter & a stripped outer extension lead of course & I'll do that.)

So, today I ran a quick test. It was at 12 O'Clock, the 960W of panels are at 33 deg at Noon and north facing. Full sun.

Power draw from the panels was about 360W & amps 9 - !0. Prior to test the batteries were showing 14.4 watts. During test with the Freezer, the Voltage dropped to 13.5 as shown on the Inverter & the MPPT Regulator.

I decided to give it more load by turning on a couple of pieces of equipment - 550W & 350 W x 240 Volt.

The voltage dropped quickly to 13 volts however, I did expect an increase in power from the panels as more current was drawn from the batteries. But there wasn't.

Is there a reason that this may not have happened?

Thanks.

Graeme

[jules]

Power draw from the panels was about 360W & amps 9 - !0. Prior to test the batteries were showing 14.4 watts. During test with the Freezer, the Voltage dropped to 13.5 as shown on the Inverter & the MPPT Regulator.

.........

The voltage dropped quickly to 13 volts however, I did expect an increase in power from the panels as more current was drawn from the batteries. But there wasn't.

Is there a reason that this may not have happened?

Thanks.

Graeme

Graeme, some of your figures are a little odd. Do you mean that the batteries were at 14.4 volts [not watts] before your test?

As far as power consumption of your fridge goes, it's almost impossible to figure out how much power it will use from its power rating. If this is helpful, I'm using a small fridge which is consuming about 23 amp hour @ 24V over 24 hrs at this time of year. The instantaneous draw is 4 amps at 24V or about 100W. If it ran constantly for 24hrs that would amount to 4amps X 24hr. = 96 amp hr., so it's running about 25% of the time. If you're saying that your freezer alone is drawing 360W, that's quite high, though if only has to operate for short periods to keep its cool, that might still be ok.

10 amps @ 12V doesn't equate to 360 W, so something is wrong there.

A drop to 13V from 14.4V is understandable with that load. Yes, the panels should feed more into the batteries when you've been discharging the system. They might not, if they're already working flat out on re-charging your batteries because they're low for one reason or another. You don't actually say how much power the panels are delivering before or after your load test. The voltage of the battery alone is not an indicator of the amount of power [in amp or watts] that is being transferred in or out.

If your batteries are reading 14.4V, that's a little high so maybe your MPPT regulator could be re-set, particularly if the 14.4V occurs when the batteries are fully charged [and not while they're charging].

Sorry, I don't think I've covered everything here but with the figures you've given a certain amount of guesswork is necessary.

Jules

[harrydiculous]

Thanks Jules. Yep, 14.4 Volts, not Watts. Bad proofreading there.

I'll go through it again tomorrow without the freezer. There's enough equipment in the shed and close at hand to qualify the useage.

Tah!

Graeme

[harrydiculous]

Current set up. (It's better organised than it looks than it looks)

https://flic.kr/p/2hyFjRs

Lets see how this comes out:-

[b]PV Test[/b]
No load Start 1.00 PM 22/10/2019
PV in EMF 40.16 Volts
Power 304 Watts
Current ?
Charge Controller EMF 14.2 Volts
Current ?
Inverter showing In EMF 14.3 Volts.
Inverter Current out 0.06 A
Start
PV in EMF 37.86 Volts
Power 343 Watts
Current 9.7 Amps
Charge Controller EMF 12.4 Volts
Current 27.8 Amps
Inverter Showing in EMF 12.5 Volts
Current out 5.8 Amps (@240 V)

After Test
PV in EMF 36.2 volts
Power 296 Watts
Current 9.9 Amps
Charge Controller EMF 13.6 Volts
Current 27.8 Amps
Inverter EMF 12.9 volts & rising.

Notes. The loads was provided by 4 x single Phase 4 pole 240 V 50 Hz motors Total 1770 Watts
The Motors were all free running. (No load)
960 Watt Panels. 3 x 2 in series. Orientation 33 deg.& north. Full sun

So, the question was, I thought that that there would be a greater current draw from the Panels when the ante was upped.

I'll have to come back in & edit

[jules]

Ok, under "pre start" you've got "power" is 304 W but ? for both the "currents" What do you mean by these terms?

Under "start" you've got "power" at 340W and two "currents" again. What is "power"? What is the first "current"? The second undefined "current" at 27.8 amp might be the input from your panels [?] and the last "current out" looks about right at 5.8 amp and 240V for the load

"after test" you've still got undefined "power" of 296 W, undefined "current" at 9.9 amp and another undefined "current" at 27.8 amp.

Do any of these figures equate directly with the power in amps or watts that your panels are delivering to the regulator/battery?


For a 960 W array, none of these figures equate with the sort of levels that could be expected.

Remember that there's not much difference in voltage between a resting fully charged battery, which might be 12.5V and a 50 % discharged battery which can be 12V or so [varies between different battery brands]

[harrydiculous]

Ok, under "pre start" you've got "power" is 304 W but ? for both the "currents" What do you mean by these terms?
I should have said, ":not noted." I thought later that I should have. This is the energy coming in from the panels. There was no load so I the power, I guess, was going into charging the batteries.

Under "start" you've got "power" at 340W and two "currents" again. What is "power"? What is the first "current"? The second undefined "current" at 27.8 amp might be the input from your panels [?] and the last "current out" looks about right at 5.8 amp and 240V for the load

This is the power coming from the panels. It changed from 304 W to 340 watts under the load. Yes, the 27.8 is the input from the panels. I realised then that I should have noted the ? in the start.

"after test" you've still got undefined "power" of 296 W, undefined "current" at 9.9 amp and another undefined "current" at 27.8 amp.

Do any of these figures equate directly with the power in amps or watts that your panels are delivering to the regulator/battery?
These are the changes that occured and indicated by the equipment. panels, Regulator,Inverter at each stage.


For a 960 W array, none of these figures equate with the sort of levels that could be expected.

Remember that there's not much difference in voltage between a resting fully charged battery, which might be 12.5V and a 50 % discharged battery which can be 12V or so [varies between different battery brands]

So, what I did was note the indicators of each piece of equipment at a) Rest, then b) under load & c) load removed.

I am capable of "doing the maths." So I should do that & understand where the discrepancies are.

But thanks, Jules. Sorry if it's been a bit confusing. I think it's a bit like riding a motorcycle. One needs to become part of the machine to "know" it. I do appreciate your effort.

[jaahn]

Hi Harry
It is hard to follow what is going on there and my head hurts now
But perhaps my comment might be this. The solar regulators have a simple little processor that looks at the various voltages of the solar and the battery and the load if it is connected there, and then looks at the "rules" every now and again and adjust things to whatever the rules say.
My experience is that cheaper regulators can be slow in catching up and better quality regulators can be quite a bit faster reacting to changes.
For instance Victron say this in support of their MPPT regulators; "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 partially clouded, and light intensity is constantly changing."
Jaahn

[jules]

Graeme, you didn't say how long you ran your load test for but if it was long enough to reduce the battery capacity to any significant extent, you should have seen a higher input current from your panels after the test if the sky was clear.

edit: While running the load test, the input from your panels should have gone up much higher than it did, so, you have a problem and it's not so much a matter of riding the bike as maintaining it, which is quite a different skill.