[Question] PV System

[Ishmaelmo]

Hi all,

I have a PV system with two batteries connected in series to give 24V to a 1000W/24VDC inverter. A charger controller is available as well.

The problem is that, the batteries don't charge until full and hence dry out quickly. Is a new system, almost 2 months now in use.

We only connected two (24W each) lights and a fridge rated at 358kwh/year. I don't know much about PV power but the load seems small and as I understand, the panel must supply power during the day while batteries are charging and storing energy for night time use.

My picture is upside-down. Apology for that, tried to rotate it but didn't get it right.

[Justloadit]

The problem is that, the batteries don't charge until full and hence dry out quickly. Is a new system, almost 2 months now in use.

What do you mean - "dry out quickly?

What type/capacity/make of batteries are you using?
Are you connecting the PV panel directly to the batteries?
What do you mean a "Charger Controller is available"?
Are you using it or not?

a fridge rated at 358kwh/year

Where did you get this information?
Have you measured it?

[Ishmaelmo]

I forgot battery brand but will get info from home. Their capacity is 120AH if recall well.

Is a DIY system which came prepared with all components wired.

The KW of the fridge was found on the label of energy consumption.

[Ishmaelmo]

I'll post a picture of the system. Once took the pic after installation.

[Ishmaelmo]

Here is the picture. Is not visible enough. I ssuppose will have to send another one when on weekend when get home.

[SeanM]

Hi

With one solar panel you will only push out about 8 amps (specs given in picture), so a 120a/h battery at 12 amps charging will take 10 hours to charge, not sure how many panels you have sounds like one.

This is insufficient to charge your batteries but sufficient for your load which doesn't help as you need them mostly at night.

[Justloadit]

Even if you have more panels, Lead acid batteries have a maximum amount of charge amps, so the daily 6 hours of sunlight will not be sufficient. Also fully discharging lead acid batteries on a daily base will severely compromise battery lifespan. If you daily discharge down to 10.5V, you will only get about 30 to 40 cycles before the battery starts to loose capacity.

This is the reason that when using lead acid, that you double the capacity you require, in order to give a reasonable lifespan of 200 odd cycles before capacity starts to reduce. A safe figure is to reduce capacity down to 70% of capacity to get a few years of use out the battery. The problem that now arises is that you have to match the charger accordingly, and every couple of months you need to cycle your battery to de-sulfide the plates.

When you do the calcs, it is wise to rather go to lithium batteries from the start. It will be cheaper on the long run. Lithium can be regularly discharged to about 20% of capacity without compromising capacity. The other advantage is that you can charge lithium's under the right conditions in 2 hours. Very amicable to solar based system chargers.

[Ishmaelmo]

Hi

With one solar panel you will only push out about 8 amps (specs given in picture), so a 120a/h battery at 12 amps charging will take 10 hours to charge, not sure how many panels you have sounds like one.

This is insufficient to charge your batteries but sufficient for your load which doesn't help as you need them mostly at night.

Yes! You are right, is one panel. The batteries are 150ah, I just confirmed. It seems like we are trying to fill up a big water tank using a small hosepipe. It really makes sense.

I was thinking of connecting the batteries in parallel but that won't work because the voltage will be reduce, and the inverter requires 24V. The panel that I'm gonna now, will need to be connected in parallel with the other one to increase optimum current. Am I right?

[Ishmaelmo]

Even if you have more panels, Lead acid batteries have a maximum amount of charge amps, so the daily 6 hours of sunlight will not be sufficient. Also fully discharging lead acid batteries on a daily base will severely compromise battery lifespan. If you daily discharge down to 10.5V, you will only get about 30 to 40 cycles before the battery starts to loose capacity.

This is the reason that when using lead acid, that you double the capacity you require, in order to give a reasonable lifespan of 200 odd cycles before capacity starts to reduce. A safe figure is to reduce capacity down to 70% of capacity to get a few years of use out the battery. The problem that now arises is that you have to match the charger accordingly, and every couple of months you need to cycle your battery to de-sulfide the plates.

When you do the calcs, it is wise to rather go to lithium batteries from the start. It will be cheaper on the long run. Lithium can be regularly discharged to about 20% of capacity without compromising capacity. The other advantage is that you can charge lithium's under the right conditions in 2 hours. Very amicable to solar based system chargers.

I'm not certain about the charger if is matches correctly. We bought the system prepared. We only fitted the panel on the roof. I'll have to check if is lithium or lead acid, I never thought of the pros and cons of battery acid type.

As far as I can understand the comments so far, it seems like adding the panel might help us. This batteries are not fully charged or not charged at all. Before we add the fridge, the system was switching off around 04h00 in the morning, now it switches off early, say just after 00h00.

Consumption have increased, on the other hand, batteries not fully charged.