Victron Inverters

[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.

[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]

I am not very good at the figures.

Then you need to listen to people who do know and have 30 years experience. Your system is grossly undersized based on the data you have provided.

[cortijo]

I am not very good at the figures

My batteries are 380ah 24 volts.
With no sun they would last about 1 day.
The cut off point is 23.8 volts.

I don't know how many DOD that is.

I don't understand all the theory I just observe what happens in practice.

[Sunking]

My batteries are 380ah 24 volts.
With no sun they would last about 1 day.

I imagine that would cost about 8000 euros and people say that batteries only last about 4 years.

4 to 5 years is true if you only discharge them 20% or less per day. If you discharge them more than 50% per day the way you do they only last a year.

Here are some stats for a popular L16 380 AH battery 0f Cycle Life vs Depth of Discharge.

20% DOD @ 3000 Cycles
30% DOD @ 2500 Cycles
50% DOD @ 1000 Cycles
80% DOD @ 400 Cycles This sounds like where you are at.

24 volts @ 380 AH is 9 Kwh. I suspect since you have a very large inverter you are drawing more than 19 amps which is where the 380 AH rating comes from. If you are drawing say 40 amps, the ereal capacity drops to about 250 AH due to Peukert Law. So that 24 volt 380 AH battery turns in 24 volts at 250 AH which is a total capacity of 6 Kwh and you use 5 Kwh every day.


Second big problem it sounds like you have is if you really use 5 Kwh per day, you do not have enough panel wattage to generate that much power each day. Assuming you use the top of the line MPPT 40 amp Charge controller you would have to have a 7.5 Sun Hour day. No place on earth gets that much sun light, not even Spain. Assuming you get a decent 4 Sun Hours in Winter months using an 80 Amp MPPT charge controller would take a 1900 watt solar panel to generate 5 Kwh of usable electricity per day. If you have a PWM CC much more panel wattage required.

Sorry but every thing you have given thus far indicates your solar system is grossly undersized incapable of doing what you want. At minimum you are looking at:

1600 Watt Solar Panel
24 volt 1050 AH battery
80 Amp MPPT Charge Controller.

[inetdog]

My batteries are 380ah 24 volts.
With no sun they would last about 1 day.

To last even 3 or 4 days with no sun would require a massive battery bank.

I imagine that would cost about 8000 euros and people say that batteries only last about 4 years.

When you say "last about one day", what Depth of Discharge (DOD) are you measuring that to?

A DOD of 50% will not do great damage to your batteries, but will provide a smaller number of cycles in their useful life than a 20% DOD would.
If you go as low as 80% DOD, your batteries will not last very long at all, probably less than one year.

You need to do the calculation comparing:
1. the cost of batteries using a small bank (50% DOD in one day) and replacing after 2 or 3 years (even less if you do not correct the LVCO setting), and
2. the cost of a larger battery bank (20% DOD in one day, giving you a 2 1/2 day reserve to 50%) which you will replace perhaps every 5 years, or potentially longer if you use true RE Deep Discharge batteries and give them good care.

Your bank should not be any smaller than that which gives 50% DOD in one night with typical sun, and which can be recharged by the panels the following day.

Whichever one gives you the lowest long term cost, and involves in initial cost that you can handle, will be the choice for you.

[cortijo]

My batteries are 380ah 24 volts.
With no sun they would last about 1 day.

Since I bought my new solar panels (6 X 190 watts) in March I have used a generator about 3 times and none of these times was really necessary.

The only time the system went down was when I bought the victron inverter with the silly default setting of not switching back on again once it has been switched off.

According to my efergy wireless power monitor I use an average of 5kwh per day.

I am happy with my system.

To last even 3 or 4 days with no sun would require a massive battery bank.

I imagine that would cost about 8000 euros and people say that batteries only last about 4 years.

When there is less sun I turn the temperature of the fridge up to 12C and also turn the freezer up.
I boil water for tea on the gas rather than in the kettle.

I don't think having a generator is a sign of a badly designed system as long as it is not used very often.

A small jam jar full of petrol put into a 900 watt generator will give me enough power for about 4 hours

If I had to choose I would rather have a generous amount of solar panels than a generous amount of batteries

this plan would have to include an occasional jam jar full of petrol.

A nice idea would be to grow some sunflower seeds and make some biodiesel for when the generator is needed.

Also don't forget that my solar panels have a theoretical max input of 1100 watts.
They generate about 130 watts even when it is raining.

[Sunking]

Iwould say the battery supply should be a size to last 3 days I think 5 days is just far to expensive for most people.
Mabe a diesel generator that turns on automatically after one day power outage is a better cost effective way . Its the way I would go.

That is not cost effective. Gen fuel is expensive.

[Sunny Solar]

Iwould say the battery supply should be a size to last 3 days I think 5 days is just far to expensive for most people.
Mabe a diesel generator that turns on automatically after one day power outage is a better cost effective way . Its the way I would go.

[Sunking]

I have about 1100 watts of solar panel generation power at full sun and about 130 watts on a cloudy day.
If I am not at home there is a enough power to keep the freezer going even on a cloudy day.

That tells us your system is improperly designed. The battery should have a minimum 5 day reserve capacity.

[cortijo]

I have about 1100 watts of solar panel generation power at full sun and about 130 watts on a cloudy day.
If I am not at home there is a enough power to keep the freezer going even on a cloudy day.
It may cut out early in the morning but as long as it comes on again it's OK.
I live in Andalucia Spain and it is never cloudy for very long.

The freezer goes down to minus 25 C so it can take maybe 12 hours of no power before it gets to 0C.
Having a minimum maximum thermometer in the freezer will let me know if the temperature got up to a dangerous level
(say over 5C)
Getting a freezer to go to a very low temperature is a way of storing energy.
Some of the modern fridges have an autonomy of 14 hours.
I did think about only running my freezer ONLY during the hours of daylight but my system is powerful enough to cope with a freezer running normally.

The real answer is to get a generator which starts automatically.
My generators don't have automatic ignition.
I think there are kits which convert them to automatic ignition.
This is a very interesting subject.

[Sunny Solar]

Victron products are in my opinion the best you can buy.But they do have somw quirks and different thinking to some other manufacturers. Beany boy has actually discovered one of them. Yes they srt the low voltage cut off very low. But their reasoning is whatever you are powering should be kept going until the batteries cannot provide the power needed. As Beanyboy noticed that if battery cut off high you lose all food in fridge/freezer. With off grid you cant have your cake and eat it too.
Victrons belief and its a valid one your battery pack should be big enough to outlast any period the batteries wont be recharged or you will have a generator that cuts in at some pre determined period before the batteries are seriously depleted.

[Beanyboy57]

I just bought a 24volt 2000 watt inverter from Victron Energy.

The default setting is that once the battery power goes lower than 19 volts it switches off.
The problem is that it does not switch on again when the power gets higher again.
It goes into a "lock"

I have already had to throw away food in my freezer.

I hope I am reading what you say correctly, but obviously I do not have all the information that you have about your system.
The Victron inverters have a red alarm light that will visually warn you when the battery voltage is getting low. If you are not there to see that alarm then you do have a problem. Also most battery monitors have visual and/or audible alarms. I have certainly learned that off-grid systems require constant maintenance and monitoring if you are to get the maximum life from your batteries and so the alarms must not be ignored.

If you decide to set the low voltage cut off at a higher voltage than the factory set 19v, say 22.8v, then the inverter will cut off to save your batteries but your food in the freezer will again be ruined. Also there may be times when the voltage drops quite low (under your new cut off point) for a very brief amount of time when starting up a household appliance, due to the size of the wiring in the inverter. Hence the low cut off point that Victron have set.
It seems to me that you need to ensure that you have enough 'power' to run your appliances for the time that they need to run. If you don't have enough power to run them, then obviously you need to increase your power reserve (battery bank) or reduce your demand. Having cut off devices and alarms are all useless if you are not there to attend to them within a reasonable amount of time.

[Sunking]

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

[cortijo]

I have just installed the drivers on an old XP machine and I have now connected to the inverter and hopefully I have stopped it going into lock.

The cut off voltage is actually 18.4 volts.
I agree this seems very low.

This exact subject is being talked about on another forum here

http://www.fieldlines.com/index.php?topic=143049.0

Do you think I should trust that Victron know what they are doing with the default setting or should I change it?