Victron Inverters

[cortijo]

Here are the facts:

I have a 24 volt battery bank.
It consists of 12 - 2volt cells - On each cell it says 380 AH


I have 6 x 190 watt panels
Plus 2 x 125 watt panels.

In July I used 103 kwh
August 152 kwh
Sept 140 kwh

During this time I was using an atersa 750 watt inverter (not MPPT)
The cut off voltage is 23.8

This is according to the efergy energy monitor.

The generator was not used at any time in July, August and September.
A 600 watt pool pump was used for about 4 hours per day almost all days.

Maybe I got the amp hours of the battery wrong.

Does this still sound a very undersized system?

[Sunking]

It means you use an average of 4.25 Kwh/day, and yes you are undersized. Come Late November, December, and January you should begin to realize that.

[Sunny Solar]

That is not cost effective. Gen fuel is expensive.

That would depend on many variables.
His present system is inadequate to really provide a below 50% battery discharge each day under ideal conditions.

He claims he never used a generator at all in July August September,.But I think he should have run it sometimes.

The cost of expanding the batteries and panels x5 is going to be very high and so is the battery replacement every 4 years or so.
If he doubled his present batteries and panels he may only need to infrequently need to run the generator and only for short periods,to make up the solar shortfall.

All the above would need to be first calculated out for cost and then see what is cost effective .Replacing the new expanded batteries each 4 years may be a more expensive exercise. It can all only be calculated out if all the costs of fuel and items are worked out in that country.,

Example :battery prices for a given brand name..in many countries are at least 50% higher than USA.

[Beanyboy57]

All the above would need to be first calculated out for cost and then see what is cost effective .Replacing the new expanded batteries each 4 years may be a more expensive exercise. It can all only be calculated out if all the costs of fuel and items are worked out in that country.,

Example :battery prices for a given brand name..in many countries are at least 50% higher than USA.

Sorry, this is not quite on the topic of the thread but I am interested in what other's pay.
A Century/Yuasa T105 6V 225 ahr battery (almost exact copy of the Trojan) $190 Australian. How does that compare to other countries?
30amp MPPT programmable CC with temperature control around $230 (Chinese brand)

[Sunking]

Sorry, this is not quite on the topic of the thread but I am interested in what other's pay.
A Century/Yuasa T105 6V 225 ahr battery (almost exact copy of the Trojan) $190 Australian. How does that compare to other countries?

In the USA and live in a large city or near one and shop around you can get an authentic Trojan T105 for around $115 to $130 USD. I think that converts to $110 to $125 AUD.

[Sunny Solar]

In the USA and live in a large city or near one and shop around you can get an authentic Trojan T105 for around $115 to $130 USD. I think that converts to $110 to $125 AUD.

The Trojan T105 is available here in AUS at Brisbane $226. This is my point before you can be certain about cost efectiveness you need to know the cost of the item in the country its going to be bought in.
A good quality 30a MPPT controller here will set you back close to $300 but a very good 30a PWM one will cost $130.

[cortijo]

I have great respect for all the experts here.
I chose the amount of new solar panels based on what I was advised here.

My experiences based on reality don't tie up with the figures.

In the summer I kept a 70m3 swimming pool clean.
Had an average of 8 people staying here.
Kept all their clothes clean (using a cold water automatic washing machine)
Had 3 or 4 laptops connected to internet.

I never used a generator one and that is not a lie.
The system I had before was very underpowered.

Last December I only had 250 watts of solar panel power.
Most evenings I put the generator on for a hour or so.
This must have cost me about 12 euros over the month.

This December with my new panels I expect to be very comfortable and only use a bit of generator power in case of bad weather.

You have to take into account that in the winter there is no swimming pool pump
The freezer can be outside at 4C ambiente temp rather than 30C ambient temp.
The lower temperature of the panels give a better performance.

There seems to be a lot of difference between what theoretically should happen and what is actually happening.

Maybe it is because I got used to the previous underpowered system.
All my lights are LED tubes or LEDs.
The high load items are only put on between 12 noon and 4pm.
The rest of the time I only use about 120 watts.
I only consider that the batteries have to get me through the night.

My batteries are now 3 years old and seem to be in good condition.
When I have to replace them I will get bigger ones if I have enogh money
but I am happy with my current system.

Why is there so much difference between theory and practice?
Maybe it is due to attitude and adaptation.

If it looks a bit cloudy I will not run the pool pump.
If there is lots of sun and I go away for the weekend I would put the freezer down to minus 35C.

When you do your calculations you have to take into account how attentive the house user is in optimising the available sun with the amount used. Maybe that can explain the difference.

It seems to me that it is much more efficient to use the sun directly rather than storing the energy and using it later.

Also there is the major difference in opinion.

I don't agree that it is worth the expense of getting a massive battery bank that will give power during 4 or 5 days of no sun.

I would rather spend money on an automatic start generator or even a wind turbine.

[Vern Faulkner]

Ever hear of the term "false" economy? What these guys are telling you, in blunt terms, is that if you don't add more batteries, the draw you're putting on your existing batteries will kill them, dead, in a staggeringly short period of time.

So would you rather replace your current insufficient batteries at, say, a few hundred Euros per year, or would you rather spend a thousand Euros now, and amortize that over five years, to then have a biogger bank of batteries, still working functionally, five years from now, and not have to worry about damp burgers because the freezer died again? Same cost output, far different end results.

[russ]

Also - Unless you have one of the rare locations with constant and adequate wind to make a turbine useful it would be a waste of time.

The cheap turbines sold all around are really nothing more than boat anchors waiting to be used - good ones are expensive and have to be on a tall tower.

[cortijo]

Ever hear of the term "false" economy? What these guys are telling you, in blunt terms, is that if you don't add more batteries, the draw you're putting on your existing batteries will kill them, dead, in a staggeringly short period of time.

So would you rather replace your current insufficient batteries at, say, a few hundred Euros per year, or would you rather spend a thousand Euros now, and amortize that over five years, to then have a biogger bank of batteries, still working functionally, five years from now, and not have to worry about damp burgers because the freezer died again? Same cost output, far different end results.

At about 1 hour before sundown my batteries normally show about 27C
Half an hour after sundown they normally show around 24.6 which as far as I know means fully charged.

By the next morning they are around 24.1

Then the sun gets going again.

So my batteries don't get very low.

On a day of no sun the inverter will cut out at 23.8 so the batteries don't get too low.

The inverter cuts out like this about once a month maybe.

I don't think I am thrashing my batteries.

They are 3 years old.

If I get another 2 years out of them I will be happy.

I did go down to 18.6 Volts once when I bought the victron inverter because of their ridiculous (in my opinion) default setting.
Sunking said that my batteries would be toast that low but they seem OK.
That was the only reason the freezer warmed up.
I went away for 5 days and the inverter cut me off and did not come on again.

I have been told by everyone that it is not a good idea to mix new batteries with old ones so I will wait for my current batteries to die before getting new ones.
If I am perfectly happy with my system why would I buy new batteries?

[Sunny Solar]

Cortijo ,,Yes it is not good to mix new batteries with a bank of old ones.

Really the bottom line here is if you are happy with the system as it is, Dont change it.. If it appears to be functioning well enough to satisfy you then thats it.

I did previously say why I think Victron set the cut off so low.No matter where its set it wont please everyone.

[Sunking]

By the next morning they are around 24.1

Which means you are discharging your batteries 75% DOD leaving you with only 25% capacity remaining. .

[cortijo]

Which means you are discharging your batteries 75% DOD leaving you with only 25% capacity remaining. .

Thank you for all the replies to my questions:

Sunking: In an earlier post on this thread you said that 23.8 Volts would be @ 60% DOD

I just said that the batteries went down to 24.1 and now you say that 24.1 is 75% DOD

To me that does not make sense.

23.8 Volts is the emergency cut off point (it almost never gets this low)
24.1 seems to me a fairly safe low point.

The figure of 75% DOD would mean that I would get about 600 cycles.
According to the info you supplied.

20% DOD @ 3000 Cycles
30% DOD @ 2500 Cycles
50% DOD @ 1000 Cycles
80% DOD @ 400 Cycles

My batteries are over 3 years old and have done about 1200 cycles.
So they should have gone dead about 18 months ago???

Can DOD be expressed as a voltage?
Is there a formula to change DOD to a voltage?

So that you could say for example 20% DOD of a 24 volt battery is X volts.



Lots of other things don't make sense.

Victron energy seem happy to sell an inverter which out of the box would could trash a battery bank on the first night.
There is nothing in the documentation which says that the default cut off point is so low.
One post pointed out that this is because they want to keep the energy flowing in case it is mission critical.
I would say that not trashing a battery bank which could cost $10 000 is mission critical.
After spending 900 euros I think it would be more reasonable to include a usb port in the actual product rather than having to
spend an extra 65 euros on buying a dongle which will convert an ethernet plug into a usb cable. (what a crazy idea)
In this day an age when a wifi enabled kindle costs 79 euros a 900 euro inverter ought to have wifi.


QUOTE:

There are two schools of thought.

1. Is to disable any Low Voltage Disconnect. This is usually done for Mission Critical applications where the cost of destroying batteries from completely discharging them is not a concern.

2. Use the LVD feature and set it to 50% Depth of Discharge to preserve and save the batteries. When used the LVD and LVR voltages must be chosen. Here are my recomendations.

LVD = 23.8 Volts @ 60% DOD
LVR = 26 volts

[Sunking]

Here is a table from a well respected Battery Manufacture .
Trojan Battery

[Beanyboy57]

down to 18.6 Volts once when I bought the victron inverter because of their ridiculous (in my opinion) default setting.
Sunking said that my batteries would be toast that low but they seem OK.
That was the only reason the freezer warmed up.
I went away for 5 days and the inverter cut me off and did not come on again.

I have been told by everyone that it is not a good idea to mix new batteries with old ones so I will wait for my current batteries to die before getting new ones.
If I am perfectly happy with my system why would I buy new batteries?

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