Victron Inverters

[cortijo]

I have been following this thread with interest as I am now a firm believer that any power system must be designed using the laws of physics and a lot of help from the experts but as we all know what happens in reality when humans are involved is that changes are made and theory is severely tested, also temperature plays a large part in the life of batteries as well as maintenance.
It seems like you are getting good value out of your current setup so far apart from the incident with the Victron inverter. I also have the same inverter but I made sure that my battery bank never goes more than 25% DOD (75% full) so I have never had to test out the low voltage cut off. My system is just for lighting and power tools.
I would be interested to know what brand of batteries you are using and how you have them connected together. Also where you have placed your connections from the CC and Inverter (could you upload a pic?). Also when you measure your batteries are you relying totally on your energy meter to measure the voltage or do you use a quality hydrometer to measure each cell after they have had time to settle?
Cheers
Jon

I have 2 CCs
They both measure the voltage.
The inverter also measures the voltage.
The CC's have more or less the same reading but the Victron inverter reading is higher.

I must get a hydrometer and learn how to use it.

I am planning to have a section on my solar set up on my blog with photos.
The batteries ccs and inverter are all close together in one room.

One of the problems with system design is that a big decision is the choice of batteries.
If properly treated the batteries may last 5 years.
But in 5 years their use may change.

This is my case:
When I bought my batteries my mountain house was only used for weekends.
I like it so much up here that I now spend a lot of time here. From March - November this year I have been here permanently, 100% off grid.

The choice of batteries was made by an installer.
At this time I did not understand anything about batteries or solar systems so I had to go along with what my "expert" thought best.
It probably was the right amount of battery for my usage at the time.

The big difference between my conception of a good system and other people on this thread and also books I have read is that other people believe that
the batteries should be able to withstand 5 days of no sun whereas I would be happy with 1 day.

Maybe the reason I believe this is because I live in Andalucia Spain which has a very high amount of sunlight hours and 3 days without sun happens very infrequently. Also if there is no sun it is possible to quickly minimise electricity use to a minimum.
Just 1 or 2 laptops and a 6 watt router so maybe 90 watts.
The generator I have is the smallest you can buy.
It has a 450 or 900 watt setting.
On the 450 watt setting it will go for a lot of hours for maybe 3 euros.
Even on a cloudy day the panels take in 150 watts.

These are the reasons why my batteries are still OK.

In my opinion, in solar systems, in life in general and in the words of Mr Micawber (a Charles Dickens character)
You are OK if your income is more that your outgoing.

Mr Micawber
"Annual income twenty pounds, annual expenditure nineteen pounds nineteen and six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery."

In the case of a solar system you have to take some inefficiency into the equation.

With a solar system:
If your big expenditure happens at times of maximum income and at times when there is no income the expenditure is low and you have enough flexibility to vary the expenditure then you are more likely to be happy with the system.

Here is some more info on my system.

The CC s are PWM

I have a 24 volt system
I have 12 of the following batteries

Classic 5 OPzS 380 2v Solar Liquid Cell
Voltage: 2V
Capacity: 380Ah @ c120

I mainly chose to have a 1200 watt system because SUNKING (from this forum) said I would need 1200 watts charging power for my batteries.

(I hope that SUNKING knows what he is talking about because I have trusted his figures.)

See post

http://www.solarpaneltalk.com/showth...4185#post44185

I now have 2 charge controllers.
One with 250 watts of panels the other has 950 watts.

[Beanyboy57]

I have 2 CCs


In my opinion, in solar systems, in life in general and in the words of Mr Micawber (a Charles Dickens character)
You are OK if your income is more that your outgoing.

I remember Mr Micawber very well (I think it was Bob Hoskins played that character in the BBC play), he had some good advice for all of us about spending more than we earn, but those guys that sell credit cards would try to discredit him hahaha.
I live in Perth WA, I think we are in one of the sunniest places on the planet, I think over the last 30 years I can count on one hand when it rained for more than one day, we have a huge desalination plant here to supply us with enough fresh water. I have a friend in France who said that she would be out in the sun everyday if she was here, but you know, when you are here, you want to hide from the sun as much as possible!!! We have the highest rate of skin cancer in the world here. It's probably similar to where you are as far as the amount of sunlight goes.

Although there is an insolation chart for Perth, I can hardly believe that is is accurate given how much sunlight we get each day and how little cloud cover we get. That's why I think that we must use our own (well researched) judgement coupled with the advice of the experts when we are planning an off-grid solar powered system. I think any 'expert' will give you the worst case scenario so that when you plan you have the best plan possible, just like a doctor will give you the worst case assessment so that you listen to the advice he or she offers.

[Sunking]

The CC s are PWM


I now have 2 charge controllers.
One with 250 watts of panels the other has 950 watts.

You need 1 MPPT unless you have different size panels. Just replacing the CC will boost your daily harvest some 20 to 30 % without adding a single panel.

[Sunking]

This is my case:
When I bought my batteries my mountain house was only used for weekends.
I like it so much up here that I now spend a lot of time here. From March - November this year I have been here permanently, 100% off grid.

The choice of batteries was made by an installer.
At this time I did not understand anything about batteries or solar systems so I had to go along with what my "expert" thought best.
It probably was the right amount of battery for my usage at the time.

YOu have outgrown your system

The big difference between my conception of a good system and other people on this thread and also books I have read is that other people believe that
the batteries should be able to withstand 5 days of no sun whereas I would be happy with 1 day.

Here is the part you do not understand yet. You never ever want to discharge your battery more than 50%. If the batteries are sized for 5 day reserve capacity only gives you 2.5 days for cloudy spell. At that poin tyou have to shut down or start running the generator. For the generator needs to be sized to provide a C/8 charge rate for FLA batteries to minimize fuel burn and minimize charge efficiency. So if you were to say have a 24 volt 380 AH battery, you are looking at about a 2 Kva genset and a 24 volt 50 amp charger.

If your batteries are as you claim 24 volts @ 380 AH gives you a total capacity of 24 x 380 = 9.1 Kwh of reserve capacity at a 20 hour discharge rate (19 amps). As I have tried to say before I will bet you money you discharge at a higher rate that 19 amps. That being the case you have to derate the batteries which means they are actually less than 9.1 Kwh.

You claim you are using 4.5 to 5 Kwh each day and I believe you. That means you are discharging your batteries more than 50% each day. Your battery voltages are indicating you are doing just that.

[Beanyboy57]

I have a 24 volt system
I have 12 of the following batteries

Classic 5 OPzS 380 2v Solar Liquid Cell
Voltage: 2V
Capacity: 380Ah @ c120

I just checked out your battery specs...Long life flooded tubular plate batteries
Design life: >20 years at 20ºC, >10 years at 30ºC, >5 years at 40ºC.
Cycling expectancy of up to 1500 cycles at 80% depth of discharge.
Manufactured according to DIN 40736, EN 60896 and IEC 896-1.

Low maintenance
Under normal operating conditions and 20ºC, distilled water has to be added every 2 – 3 years.
It seems like you have great batteries that will serve you well if you look after them. I am envious...hahaha

[cortijo]

For the generator needs to be sized to provide a C/8 charge rate for FLA batteries to minimize fuel burn and minimize charge efficiency. So if you were to say have a 24 volt 380 AH battery, you are looking at about a 2 Kva genset and a 24 volt 50 amp charger.

I have a tudor battery charger I think it is rated at 30amps (I am not at home at the moment)

I have 2 generators:
One is about 2500 watts the other is 450 or 900 (dual).

The charger has an indicator panel on the front which I think refers to BULK - ABSORPTION - FLOAT.

In reality what actually happens when I use the charger is the following:

At the start, the charger charges at around 23amps
Then after about 5 minutes it goes down to around 17amps
After about an hour it will be charging at about 12amps.
The lowest I have ever see is 9 amps.

It makes no difference if I am using the 450 900 or 2500 watt generator. (except the 450 one does not like 23amps)

I have always considered that the Tudor battery charger was a good make and it avoids overcharging even if a lot more power is available.
I always use the 450 or 900 watt generator because it seems that using the 2500 watt generator is just a waste.
Once the charging rate is down to below 12 amps the 450 watts the generator is very happy to power the house and charge the batteries at the same time.

I need a tutorial that explains what C/8 means.
How many amps would C/8 be in this case?

You say that I need a 50 amp charger but my 30 amp charger never uses it's full charging capacity.
I don't understand?

[cortijo]

<quote>YOu have outgrown your system</quote>

So in your opinion I have just about enough panels but maybe half the amount of battery capacity I need.

What is the solution?

Can I buy more batteries to solve the problem?
Obviously I don't want to throw away my existing batteries because they still have a lot of life left.

Can I combine old batteries with new ones somehow?

[Sunking]

I need a tutorial that explains what C/8 means.
How many amps would C/8 be in this case?

It is very easy.

C= the rated battery capacity in Amp Hours at the 20 hour rate. 8 is the 8 hour discharge rate. Now it is just simple factoring out what we need. Amps = AH / H. So your battery is 380 AH right?

So C/8 = 380/8=47.5
C/10 = 380/10 = 38

380 AH / 8 Hours = 47.5 amps. So to charge your battery in the shortest amount of time which is 8 hours you would need a 50 amp charger.

[Sunking]

In reality what actually happens when I use the charger is the following:

At the start, the charger charges at around 23amps
Then after about 5 minutes it goes down to around 17amps
After about an hour it will be charging at about 12amps.
The lowest I have ever see is 9 amps.

This tells me you have never gotten your batteries fully charged. During the Charge process the current starts high like you have noticed. Then it tapers down to 0 amps some hours later, then switches to FLOAT which will also be 0 amps assuming you have no load on the batteries.

[cortijo]

It is very easy.

C= the rated battery capacity in Amp Hours at the 20 hour rate. 8 is the 8 hour discharge rate. Now it is just simple factoring out what we need. Amps = AH / H. So your battery is 380 AH right?

So C/8 = 380/8=47.5
C/10 = 380/10 = 38

380 AH / 8 Hours = 47.5 amps. So to charge your battery in the shortest amount of time which is 8 hours you would need a 50 amp charger.

If I have a 30 amp charger that only wants to charge at less than 17 amps.
Why would I want to get a charger of 50 amps when it is not even using the capacity of my 30amp charger?

[cortijo]

This tells me you have never gotten your batteries fully charged.

I would wait for the sun to properly charge the batteries. If I am using the battery charger it is just to stop the batteries getting too low. I wouldn't waste the petrol on using the charger to fully charge them.

[cortijo]

<quote>YOu have outgrown your system</quote>

So in your opinion I have just about enough panels but maybe half the amount of battery capacity I need.

What is the solution?

Can I buy more batteries to solve the problem?
Obviously I don't want to throw away my existing batteries because they still have a lot of life left.

Can I combine old batteries with new ones somehow?

It looks like I can get 650 AH for about 2500 euros.
How can I combine them with the 380Ah batteries I already have to get the system I ought to have?

[Sunking]

It looks like I can get 650 AH for about 2500 euros.
How can I combine them with the 380Ah batteries I already have to get the system I ought to have?

Very simple. Donate your batteries to a Fisherman as a Boat Anchor.

[Beanyboy57]

C Rate

I need a tutorial that explains what C/8 means.
How many amps would C/8 be in this case?

You say that I need a 50 amp charger but my 30 amp charger never uses it's full charging capacity.
I don't understand?

In the late 1700s, Charles-Augustin de Coulomb ruled that a battery that receives a charge current of one ampere (1A) passes one coulomb (1C) of charge every second. In 10 seconds, 10 coulombs pass into the battery, and so on. On discharge, the process reverses. Today, the battery industry uses C-rate to scale the charge and discharge current of a battery.

Most portable batteries are rated at 1C, meaning that a 1,000mAh battery that is discharged at 1C rate should under ideal conditions provide a current of 1,000mA for one hour. The same battery discharging at 0.5C would provide 500mA for two hours, and at 2C, the 1,000mAh battery would deliver 2,000mA for 30 minutes. 1C is also known as a one-hour discharge; a 0.5C is a two-hour, and a 2C is a half-hour discharge.

[inetdog]

In the late 1700s, Charles-Augustin de Coulomb ruled that a battery that receives a charge current of one ampere (1A) passes one coulomb (1C) of charge every second. In 10 seconds, 10 coulombs pass into the battery, and so on. On discharge, the process reverses. Today, the battery industry uses C-rate to scale the charge and discharge current of a battery.

Most portable batteries are rated at 1C, meaning that a 1,000mAh battery that is discharged at 1C rate should under ideal conditions provide a current of 1,000mA for one hour. The same battery discharging at 0.5C would provide 500mA for two hours, and at 2C, the 1,000mAh battery would deliver 2,000mA for 30 minutes. 1C is also known as a one-hour discharge; a 0.5C is a two-hour, and a 2C is a half-hour discharge.

Interesting collection of factoids.
1. The Coulomb reference seems totally irrelevant.
2. The 1C symbol you use in the first sentence is more commonly written as C with a subscript 1, or for the graphically challenged typists, C1. The symbol 1C commonly refers to the current which corresponds to the C rate, but does not tell us what time period (one hour, twenty hours, one hundred hours) was used to determine C in the first place. Peukert's Law as applied to Lead Acid batteries tells us that the C1, C20 and C100 figures will be very different. You then switch to using the same symbol to represent current in the second part of the paragraph.
3. I do not agree that most portable batteries are rated based on C1. The more common, AFAIK, is C20, and some batteries are rated by their manufacturer using C100, which tends to make them look better. . Starting/cranking batteries are rated in Reserve Minutes, which is more closely related to the C1 rate. But anybody who uses a starting/cranking battery for PV is making a large mistake.