Solar and Batteries is 400ah 2 x 200ah deep cylcle agm's enough

[TheEntertainer]

Hi All,

On our property we have the following running. So is it correct to say the 3kw relates to a 250ah draw per day if we have 2 x 200ah batteries. The solar system consist of 5 x 60watt panels and 2 x 180 watt panels on the roof so not easy to change the angle, they also sit in gum tree shade for 40% in summer and 60% in winter, the max I have seen on the epever is a 17a push into the sells




per hour
hours
Total


Inverter
30
24
720


GSM booster
6
24
144


Lights
40
6
240


Respirator
40
10
400


Fridge
50
24
1200


Charging
50
6
300




watts
3004




kw
3.004



Given that we only push in about a 100a via the solar on a good day we should be ok for 3 days approx.

just a general comment on how you would set your system up and if perhaps my calculations are off.

thanks

J

[windsock]

Need to understand a bit more about your energy storage.

What is your system nominal voltage? You say only two batteries so it can be either 12 or 24 volts.

What is the individual battery voltage and how are they connected? Series or parallel?

Your energy demand table indicates an electricity use of 3 kWh/d.

Do you know what the inverter efficiency is?

[TheEntertainer]

Hi mate,

thanks for the reply:

2 x 12v x 200ah AGM deep cycles in parallel - nominal 12v

Manufacturers specs for the Giandel 2000w pure sign wave inverter



[*=left]Surge Power: 4400W
[*=left]Continuous power : 2200W
[*=left]DC input : 12V
[*=left]Input voltage range : 9.5-16V DC (rated power 12VDC)
[*=left]Input over-voltage shutdown : 16VDC±0.5V
[*=left]Input under-voltage shutdown : 9.5VDC±0.5V
[*=left]Input under-voltage alarm : 9.8VDC±0.3V
[*=left]Dimensions : L 430mm W 240mm H 90mm
[*=left]Output voltage : 240V AC±10%
[*=left]Output frequency ： 50Hz
[*=left]Output wave form ： Pure sine wave ( THD ≤ 3%)
[*=left]Efficiency ： 90 %
[*=left]Over temperature protection ： 65±5℃
[*=left]Over-load protection ： 2200-2500W
[*=left]USB Output : 5 VDC Max 2.4A

[TheEntertainer]

As for the fridge, it's a bar fridge rated at 50watt's, that would only be when it's running, perhaps 20-30% of the time and for an hour after it's been stocked.

[NavyDiver]

Hi All,

On our property we have the following running. So is it correct to say the 3kw relates to a 250ah draw per day if we have 2 x 200ah batteries. The solar system consist of 5 x 60watt panels and 2 x 180 watt panels on the roof so not easy to change the angle, they also sit in gum tree shade for 40% in summer and 60% in winter, the max I have seen on the epever is a 17a push into the sells




per hour
hours
Total


Inverter
30
24
720


GSM booster
6
24
144


Lights
40
6
240


Respirator
40
10
400


Fridge
50
24
1200


Charging
50
6
300




watts
3004




kw
3.004



Given that we only push in about a 100a via the solar on a good day we should be ok for 3 days approx.

just a general comment on how you would set your system up and if perhaps my calculations are off.

thanks

J

I am not an expert! One comment on your numbers and systems stability. My work U.P.S. set up was fantastic with about 5000w load and a little more peak. Yet failed at times. At my place it was our kettle 2500 watts and Microwave..... Via a Goodwe 5kwh ES hybrid inverter.

A few other little items possibly a hair drier just might make your peak load a issue if not very careful.

[TheEntertainer]

Hi,

Luckily no one ever takes a hair dryer out to the property, my fil did have a 600w water pressure pump, we have replace this with an IBC up the hill and only now use it to pump water up now and again and we use the gennie to do so.

revised calculation, the fridge does not run all the time:



per hour
hours
Total


Inverter
30
24
720


GSM booster
6
24
144


Lights
40
6
240


Respirator
40
10
400


Fridge
50
5
250


Charging
50
6
300




watts
2054




kw
2.054

[Blknight.aus]

urm, you're very marginal.

I'm assuming that the situation is you're only out there every other weekend and when you're no there everything is off so the batteries can top up during the week/fortnight?

[TheEntertainer]

Spot on, max would be 3 days there and 3 days home. Skipping some week all up. So by the time we or my father in law returns they should be fully charged.

[windsock]

Just some quick back of the envelope estimations and observations based on the info at hand... for what it is worth... I hope it assists the planning but as with all this type of advice online, caveat emptor. [biggrin]


we should be ok for 3 days approx.

I am assuming you mean 3 days of energy stored in the batteries? This is the usual interpretation of a question like this. That is, the number of days of autonomy assuming solar doesn't provide for you e.g a storm for three days etc.


2 x 12v x 200ah AGM deep cycles in parallel - nominal 12v

Manufacturers specs for the Giandel 2000w pure sign wave inverter



[*=left]Surge Power: 4400W
[*=left]Continuous power : 2200W
[*=left]Efficiency ： 90 %



From this information we can calculate the amount of energy you can draw from the batteries you have indicated.

12V x 400Ah = 4800Wh or 4.8kWh of energy storage in the batteries - total. Assuming you don't run them down below 50% depth of discharge, 2.4kWh of energy available at a depth of discharge of 50%.




revised calculation, the fridge does not run all the time:



Watts
hours
Total


Inverter
30
24
720


GSM booster
6
24
144


Lights
40
6
240


Respirator
40
10
400


Fridge
50
5
250


Charging
50
6
300




Watt hours
2054




kWh
2.054




Corrections to the table in red. Watts is a capital W. It is named after James Watt and so is capitalised in the unit W, Wh and kWh.

OK, here a third of your load disappeared from the previous table so is now 2.1 kWh/d and not the 3 kWh/d as it was previously. This will make a big difference.

Some comments on the load. Not sure why your inverter draws 30 Watts. Is that the standby loading? It is your biggest energy user in that list. I would disconnect it if I wasn't using it at that power rating. You have some very low power loads such that if everything was on at the same time would be 216 Watts. So unless you absolutely need a 2kW rating (2000 Watts) you could also look at getting a smaller inverter and try to reduce that standby load to a few Watts only.

Anyway...

If you had 2.4 kWh of electricity in storage based on a 50% depth of discharge (DoD) and you lost 10% due to inverter efficiency loses (i.e if you wanted 2.1 kWh out you would need 2.3 kWh in there as you'd lose 10% to get the 2.1 kWh) you would really have just over a day of energy in the battery bank you indicate.

To get to 3 days autonomy you'd need to reduce your already small loads or add more of the same batteries to your system or get batteries with a bigger Ah capacity.

Don't forget to consider the impact of the depth of discharge percentage has on your overall battery sizing capacity calculations.

[JDNSW]

Speaking with the experience of living on stand alone for twenty-five years.

I was on a system that had 1.2kw nominal panels on trackers, with 24x2vx1100Ah deep cycle batteries, and two 2kVA (6kVA for five minutes) inverters. This proved 'adequate' for years, but I used the backup generator a lot, and battery life suffered.

Following a lightning strike a few years ago, this was replaced (under insurance) by 5.5kw nominal fixed panels (they are a lot cheaper than they were in 1994), same batteries and a single 7kVA inverter. The only time the backup generator has been started since was to check that it was wired in correctly. And my power use has increased - electric kettle, toaster, electric blankets, stopped worrying about power use as much.

The key is the amount of panels. Even under cloudy skies these provide significant power, meaning less load on the batteries, and fully charge the batteries with a much shorter period of sunlight than previously.

In my view, you do not have enough panels, but I would also think you need more battery capacity - discharging below 50% is a recipe for short battery life.

[Blknight.aus]

for what you're planning, your nominal reserve capacity on the batteries should meet the nominal power draw for 3 days with no solar support.

your solar system should then provide not less than 50% of the reserve capacity of the batteries.

get 2 inverters, a small one for small loads and a larger one for larger loads, the small ones have less standby power draw and the larger ones are more efficient when loaded with something near the limit of the smaller one. it also gives you some redundancy.

With you're current setup you're good for about a day and a half.

(all on back of the napkin maths against how I would normally setup a similar system that did not have the ability to be externally charged by a vehicle, genny or other charging means.)

if you've got access to running water its surprisingly easy to pinch 100w or so out of the stream.

[TheEntertainer]

Then we have the issue of buying 2 x 2--ah 12v batteries.

Is an AGM battery and AGM battery: I don't know...?

2 of the below would give an extra 200ah total 600ah

12V 300AH Deep Cycle AGM Battery Sealed Portable Solar Power - iPower (https://ipower.energy/collections/4x-battries/products/12v-300ah-deep-cycle-agm-battery-sealed-portable-solar-power)

or 2 of the below for a total of 400ah

Giantz 200Ah Deep Cycle Battery 12V AGM Marine Sealed Power Portable Box Solar Caravan Camping | Buy Electrical Hardware - 9355720058154 (https://www.mydeal.com.au/giantz-200ah-deep-cycle-battery-12v-agm-marine-sealed-power-portable-box-solar-caravan-camping-1895156?gclid=CjwKCAjwjuqDBhAGEiwAdX2cjwdXtYmAw_W0 C6gHnUrryWFfqrIOhyzE1r9OiqzfQV2BvaQQfXacgBoCjZ4QAv D_BwE)

[trout1105]

Then we have the issue of buying 2 x 2--ah 12v batteries.

Is an AGM battery and AGM battery: I don't know...?

2 of the below would give an extra 200ah total 600ah

12V 300AH Deep Cycle AGM Battery Sealed Portable Solar Power - iPower (https://ipower.energy/collections/4x-battries/products/12v-300ah-deep-cycle-agm-battery-sealed-portable-solar-power)

or 2 of the below for a total of 400ah

Giantz 200Ah Deep Cycle Battery 12V AGM Marine Sealed Power Portable Box Solar Caravan Camping | Buy Electrical Hardware - 9355720058154 (https://www.mydeal.com.au/giantz-200ah-deep-cycle-battery-12v-agm-marine-sealed-power-portable-box-solar-caravan-camping-1895156?gclid=CjwKCAjwjuqDBhAGEiwAdX2cjwdXtYmAw_W0 C6gHnUrryWFfqrIOhyzE1r9OiqzfQV2BvaQQfXacgBoCjZ4QAv D_BwE)

It is my understanding that you can only safely use 50% of you AGM batteries capacity otherwise you will destroy them So 400AH = 200AH useable capacity and 600AH = 300AH useable capacity.
If you need 400AH available then you will need 800AH of batteries.

[TheEntertainer]

thought I did not post the prev one

[windsock]

Cannot recommend or advise on either of those batteries as I have neither experience with them nor can I find any specifications, data or literature on them. This latter point makes me suspect the quality of them. Usually you get some data on performance, charging requirements, voltage vs state of charge etc... from a manufacturer.

Others on here may have experience with them.

I also think you need to look for an inverter with a much reduced standby load. That inverter load of 30 Watts is the biggest load and is not necessary when you look at the specs of other inverters. As I indicated earlier, I have seen smaller inverters with standby loads of around 5 to 6 Watts. Some even have a mode that flicks in and out of standby every 2 seconds and can draw around 1 to 2 Watts. When it senses a load it powers up. See the small victron inverters for example.

[prelude]

Regarding the battery choice. I have no experience with this battery as of yet but I am eying them for purchase myself; the victron lead carbon AGM https://www.victronenergy.com/upload/documents/Datasheet-Lead-carbon-battery-EN.pdf

The carbon allows the battery to survive partial state of charge a lot more often/longer and it can be more deeply discharged as well. There is test data provided at the bottom of the PDF.

Cheers,
-P

[DiscoMick]

Have you considered, if you haven't already, fitting LED lights to cut your consumption? We are progressively replacing our lights with LEDs, which are great.
Microwaves and kettles are big drains. It is possible to buy 12 volt kettles. Maybe you could also convert some lights to 12 volt LEDs.
Some friends had a rural property on stand- alone solar power a while back and, I can't remember the size of their AGM battery bank, but it was larger than yours.
Another friend bought a second-hand yacht wind generator and hooked it up for some extra charge, particularly at night.

Good luck with it.

[TheEntertainer]

Hi,

The batteries only run the lights and respirator.

We are going to buy some LiFePo4 135ah hours, and they are not that expensive any more, a tad more than AGM's but you can DOD them to 90% (max). It also means we don't net such a large inverter, might drop down to 800watt. I've been using my 400watt but it seems to work hard and it's expensive to run the fan.

cheers

J

[W&KO]

Hi,

The batteries only run the lights and respirator.

We are going to buy some LiFePo4 135ah hours, and they are not that expensive any more, a tad more than AGM's but you can DOD them to 90% (max). It also means we don't net such a large inverter, might drop down to 800watt. I've been using my 400watt but it seems to work hard and it's expensive to run the fan.

cheers

J

I’m not sure I understand the link between upgrading to Lithium reduces the size of the inverter.