Living offgrid with small solar system(s)

[Muhendis]

Well Gary A you certainly did the right thing getting a spare inverter. China does not have a reputation for quality control so you have done well with them lasting for three years.

two of my Chineses inverters lasted 9½ years and still work, one had a minor problem and was repaired for 700 Baht. but having a spare is a good idea, in my case having five spares is a good idea too.

China bashing isn't one of my favourite pastimes as i was always quite happy with the price/performance ratio. mileages may differ of course.

I agree price/performance ratio is not a problem and I didn't intentionally start China bashing. Many good things come out of China which work according to spec. but I can't help noticing shoddy workmanship from time to time which would not get past quality control in Germany or Holland. It is this shortfall that will cause product failure from time to time.

[George Harmony]

About lithium vs lead acid. This is a way to do a (price) comparison.

[Gary A]

About lithium vs lead acid. This is a way to do a (price) comparison.

That's not a good comparison. I'd be surprised if the Trojan battery did as well as shown. A 100 percent discharge will kill even a deep cycle quickly.

[IMHO]

About lithium vs lead acid. This is a way to do a (price) comparison.

I agree with Gary A - any proper comparison needs to take into account actual DOD's you'd use for each battery cell type.

[George Harmony]

Something else. I came accross this when i was searching for a dc pump. A rechargeable tv of an acceptable size for the living or bed room. For those who can hang themselves when they have to miss an important football match hehehehe.

What kind of rechargeable products do i now have:

Laptop, tablet, hp's, lamps, fan and some stand alone cctv cams. Those products are handy cause you can use it also ac with an adaptor. When connected to a power source and it runs hopefully the buildin battery will also be charged.

So, whats next?? Rechargeable microwave, fridge, wellpump or even small aircon...????

Who knows what the future can bring. For those who are not use of power outages i inform you thay 2 days ago in my area was a power outage from 7 morning till 22.00 evening. Day before also total 8 hours. Today 2 hours till now.

A rechargeable wellpump is perhaps good for such area. Many houses had problems with their water supply.

Ofcourse if you have an offgrid system is it no problem.

[Muhendis]

About lithium vs lead acid. This is a way to do a (price) comparison.

I agree with Gary A - any proper comparison needs to take into account actual DOD's you'd use for each battery cell type.

FLA 200Ah at 30% DOD available capacity 60Ah cycles 500 Price 6800 Baht Price per cycle 13.6 Baht

LiFePO4 65Ah at 90% DOD available capacity 58.5Ah cycles 2000 Price 24,000 Baht Price per cycle 12 Baht

The LiFePO4 is american http://www.batteryspace.com/lifepo4-26650-rechargable-battery-12-8v-65ah-832wh---replace-sla-battery-with-lighter-weight-and-higher-capacity---un38-3-passed-dgr.aspx

The FLA is Thai from NC Batteries

The cycle numbers I have chosen are, as far as I can tell, the sort of figures that are generally accepted and there are probably far less expensive LiFePO4's to be got from China.

This is not a competition to brag about how many cycles you might get from your own personal experience but can be taken as a fair guide to the difference in cost between FLA and LiFePO4

[Gary A]

Maybe someone can correct me if I am wrong. I view a cycle as each time I use 50 percent of my batteries charge and recharge it. That means to me that after three years of constant use, I already have a thousand cycles. I expect my batteries to go at least three more years and hopefully longer.

[Naam]

Well Gary A you certainly did the right thing getting a spare inverter. China does not have a reputation for quality control so you have done well with them lasting for three years.

two of my Chineses inverters lasted 9½ years and still work, one had a minor problem and was repaired for 700 Baht. but having a spare is a good idea, in my case having five spares is a good idea too.

China bashing isn't one of my favourite pastimes as i was always quite happy with the price/performance ratio. mileages may differ of course.

I agree price/performance ratio is not a problem and I didn't intentionally start China bashing. Many good things come out of China which work according to spec. but I can't help noticing shoddy workmanship from time to time which would not get past quality control in Germany or Holland. It is this shortfall that will cause product failure from time to time.

of course Chinese workmanship cannot be compared with that from Europe, especially not Germany or Holland. but the price/quality factor must be included in the equation.

i will not spend 28,000 Baht to replace my Hayward pool pump if it conks off but use a Chinese made pump (same specifications) for 3,600 Baht (my present pump used for garden irrigation).

my two Mitsubishi pumps for house water supply are each 13,000 Baht. they will be replaced by Chinese pumps costing each 2,200 Bht.

[George Harmony]

@Gary,

Is it then after 3 years more not 1000 cycles 100% discharge?????

Edited April 21, 2016 by George Harmony

[Gary A]

@Gary,

Is it then after 3 years more not 1000 cycles 100% discharge?????

Since the batteries are used every day and usually discharged near 50 percent, then recharged, every day is a cycle. I expect the batteries to last at least 2,000 cycles, hopefully more. I would never allow my batteries to go flat. In fact my inverter would shut off because of low voltage. Before that my charge controller would be blinking a red warning light.

[George Harmony]

Think many entrepeneurs will invest in the developping of better batteries, especially when other countries will follow the Dutch. 2025 ban on sales of fuel cars

https://www.theguardian.com/technology/2016/apr/18/netherlands-parliament-electric-car-petrol-diesel-ban-by-2025

Good you r not living in holland @naam with your oldtimers .......

[Gary A]

@Gary,

Is it then after 3 years more not 1000 cycles 100% discharge?????

Since the batteries are used every day and usually discharged near 50 percent, then recharged, every day is a cycle. I expect the batteries to last at least 2,000 cycles, hopefully more. I would never allow my batteries to go flat. In fact my inverter would shut off because of low voltage. Before that my charge controller would be blinking a red warning light.

I just had a look at my charge controller manual. It gives the red light warning at 12.0 volts and shuts down at 11.1 volts. I watch my volt meter and if it gets down to 12.1 volts, I shut down. Here's my small house system.

Edited April 21, 2016 by Gary A

[George Harmony]

I understand @Gary. I mean for comparison like above sheet i posted. Is it whay they ment by 100% 2x50% discharge. So, in your case 1000 cycles in expected 6 years. If for example you only use daily 20% of the capacity the battery will problaly last longer. What is a cycle then??

Edited April 21, 2016 by George Harmony

[Gary A]

I understand @Gary. I mean for comparison like above sheet i posted. Is it whay they ment by 100% 2x50% discharge. So, in your case 1000 cycles in expected 6 years. If for example you only use daily 20% of the capacity the battery will problaly last longer. What is a cycle then??

The way I use my batteries is one day equals one cycle. Since I have been using them for three years already, the way I calculate, that would be about a thousand cycles figuring about 330 days a year. I'm not home 365 days a year. Yes, if they are discharged less than 50 percent, the life would be longer. What battery calculations for solar systems overlook is that the panels have, or should have the capacity to carry the entire load and fully charge the batteries at the same time. The batteries take the full load only when the sun goes down. If you are using the batteries like a UPS, the batteries stay fully charged all the time unless there is a power failure. Regular car batteries would last a long time. Yes, it is complicated so everyone needs to have his own method of calculating cycles. Using batteries like a UPS would have VERY few cycles.

I started out with one panel and one battery. When I learned how everything worked, I just kept adding on until I got to where I wanted to be. The best way to learn solar is by doing. I even have a little feed the grid system. That's really easy, no charge controller or batteries needed. The grid tie inverter does it all.

[Naam]

Since the batteries are used every day and usually discharged near 50 percent

how do you calculate the discharge percentage Gary?

is there a given fixed rule like "voltage x = discharge %" or is it calculated / estimated because you know your demand?

[IMHO]

Since the batteries are used every day and usually discharged near 50 percent

how do you calculate the discharge percentage Gary?

is there a given fixed rule like "voltage x = discharge %" or is it calculated / estimated because you know your demand?

The state of charge of lead acid can be determined pretty accurately by it's no-load voltage. Under load it becomes a lot more tricky though.

Edited April 22, 2016 by IMHO

[Naam]

Since the batteries are used every day and usually discharged near 50 percent

how do you calculate the discharge percentage Gary?

is there a given fixed rule like "voltage x = discharge %" or is it calculated / estimated because you know your demand?

The state of charge of lead acid can be determined pretty accurately by it's no-load voltage. Under load it becomes a lot more tricky though.

interesting! now tell me how to determine please

[Gary A]

Maybe not the most accurate but I depend on a voltage meter connected directly to the battery bank. When the batteries are under load and the voltage meter shows 12.1 volts, I shut the system down. After shut down, the voltage normally goes back up to around 12.3 volts or a little higher. That means I am well in the zone that will give me safe long battery life. The voltage dropping to 12.1 volts under load rarely happens because my little system is oversize for my modest needs. If we have little or no sun for a few days, I have the option of hooking up my automatic charger or connecting into the main grid. Today it is overcast but at 10:00 AM my batteries are very nearly fully charged even while running my computer room. I am running my desktop computer, printer, a fan and a hepa air purifier. The air purifier is needed to keep my wife from complaining about my cigarette smoke. There is really no logical reason to get really technical. I just do what works. Rarely I do forget to to keep an eye on the voltage meter but even at that, the charge controller warns me at 12.0 volts. After shut down the voltage comes back up to maybe 12.2 volts so no damage is done. I have only seen the low voltage warning a few times so I know that it works properly.

Added - I have a little Fluke clamp type multi meter that is handy. I can check the DC amps and the AC amps as well as the voltages just to make sure everything is working properly. I am always a little surprised at how efficient my cheap Chinese inverter is. My Fluke multi meter only goes to one decimal point so it is not very precise, but close enough.

My panels put out 30 volts and coming from the charge controller going to the batteries right now is 13.5 volts and 22 amps. That's less than half of the 600 watt panel rating but still enough to run everything and still charge the batteries.

Edited April 22, 2016 by Gary A

[Muhendis]

About lithium vs lead acid. This is a way to do a (price) comparison.

I agree with Gary A - any proper comparison needs to take into account actual DOD's you'd use for each battery cell type.

FLA 200Ah at 30% DOD available capacity 60Ah cycles 500 Price 6800 Baht Price per cycle 13.6 Baht

LiFePO4 65Ah at 90% DOD available capacity 58.5Ah cycles 2000 Price 24,000 Baht Price per cycle 12 Baht

The LiFePO4 is american http://www.batteryspace.com/lifepo4-26650-rechargable-battery-12-8v-65ah-832wh---replace-sla-battery-with-lighter-weight-and-higher-capacity---un38-3-passed-dgr.aspx

The FLA is Thai from NC Batteries

The cycle numbers I have chosen are, as far as I can tell, the sort of figures that are generally accepted and there are probably far less expensive LiFePO4's to be got from China.

This is not a competition to brag about how many cycles you might get from your own personal experience but can be taken as a fair guide to the difference in cost between FLA and LiFePO4

The figures are for the minimum life expectancy. I also would expect to get more than the minimum from my batteries. It's good to know batteries are getting plenty of TLC from forum members.

[Muhendis]

Since the batteries are used every day and usually discharged near 50 percent

how do you calculate the discharge percentage Gary?

is there a given fixed rule like "voltage x = discharge %" or is it calculated / estimated because you know your demand?

The state of charge of lead acid can be determined pretty accurately by it's no-load voltage. Under load it becomes a lot more tricky though.

interesting! now tell me how to determine please

The only way to check state of charge/discharge is by using a hydrometer or coulomb counter or a refractometer. Aw bum. That's three ways

[George Harmony]

Perhaps this is usefull info

For lead acid, the end-of-discharge is typically 1.75V/cell, for NiCd/NiMH 1.0V/cell and for Li-ion 3.0V/cell. If a 1Ah battery provides 1A for one hour, an analyzer displaying the results in percentage of the nominal rating will show 100 percent. If the discharge lasts 30 minutes before reaching the end-of-discharge cut-off voltage, then the battery has a capacity of 50 percent. A new battery is sometimes overrated and can produce more than 100 percent capacity; others are underrated and never reach 100 percent, even after priming.

[IMHO]

No load voltage measurements for a 12V nominal lead acid are"

100% : 12.7V

90% : 12.5V

80% : 12.42V

70% : 12.32V

60% : 12.2V

50% : 12.06V

40% : 11.9V

30% : 11.75V

20% : 11.58V

10% : 11/31V

In order to calculate the DOD with a load present, you would need to understand the load itself, the internal resistance of the battery, and the resistance of all connectors and cables. Apply some Ohms law and you'd then be able to work it out.

[Naam]

i am thankful for all answers from 4 learned and experienced gentlemen

but i still have a question. when there is a full powercut or on one specific phase only where the demand on the inverter is highest, the voltage drops to 24.5 under no load all systems show a steady 27.1 no matter whether inverter is on or switched off. any comments?

we are expecting tomorrow a powercut on all 3 phases lasting 4 hours and i will be initially walking around wearing a thick bathrobe and a furcap (if i find one) because when i go to bed tonight because ~200,000 btu/h will be cooling the main area till power is off.

i will be busy measuring voltage of battery banks under various conditions and will report.

[Gary A]

As I said, I'm not into the high tech precision methods. Using a hydrometer is not possible with sealed batteries. Reading the voltage is easy and gives me enough information. I think the most important thing is not to discharge your batteries more than 50 percent even if that means buying an extra battery or two.

I'm happy to wait a while until Tesla gets the prices down for the li-ion batteries. That will happen, I'm sure.

[Gary A]

i am thankful for all answers from 4 learned and experienced gentlemen

but i still have a question. when there is a full powercut or on one specific phase only where the demand on the inverter is highest, the voltage drops to 24.5 under no load all systems show a steady 27.1 no matter whether inverter is on or switched off. any comments?

we are expecting tomorrow a powercut on all 3 phases lasting 4 hours and i will be initially walking around wearing a thick bathrobe and a furcap (if i find one) because when i go to bed tonight because ~200,000 btu/h will be cooling the main area till power is off.

i will be busy measuring voltage of battery banks under various conditions and will report.

Maybe you should buy some rubber adult diapers and a big container of ice. You could keep dropping ice cubes in you pants. That should keep you cool.

I have no idea what a hydrometer will tell you when the batteries are under load. The only time I have used a hydrometer is when I was checking for a dead cell. I don't even have one now. Watching the voltage is my way of preventing over discharging. When the load is removed the voltage will come back up quite a bit so there is a comfortable safety factor.

[George Harmony]

when there is a full powercut or on one specific phase only where the demand on the inverter is highest, the voltage drops to 24.5 under no load all systems show a steady 27.1 no matter whether inverter is on or switched off. any comments?

No matter if the inverter is on or off and no charging???? Do you have a 10watt inverter? Hehehehehe

[George Harmony]

@gary,

How do you charge ongrid? Do you use an ac battery charger or an adaptor to your solar chargecontroller?

[Muhendis]

As I said, I'm not into the high tech precision methods. Using a hydrometer is not possible with sealed batteries. Reading the voltage is easy and gives me enough information. I think the most important thing is not to discharge your batteries more than 50 percent even if that means buying an extra battery or two.

I'm happy to wait a while until Tesla gets the prices down for the li-ion batteries. That will happen, I'm sure.

OK so checking the specific gravity would be a trifle tricky with sealed batteries. That leaves you with coulomb counting.

For that you need this.........http://www.ebay.com/bhp/battery-charge-meter

[Gary A]

@gary,

How do you charge ongrid? Do you use an ac battery charger or an adaptor to your solar chargecontroller?

I just plug a standard charger in to an AC wall socket. When the batteries are up to about 12.6 volts, I unhook it.

[George Harmony]

I started out with one panel and one battery. When I learned how everything worked, I just kept adding on until I got to where I wanted to be.

Thats very good @gary. How is your experience with adding a battery to your existing battery bank. A new battery added to an existing (older) battery bank.