Help with batttery system

[lkruper]

What I see is a trade off. It should cost much less for the 300 watt panel then 3 x 100 watt panels. Getting the 4th 100 watt panel would be adding more cost only to have that PWM CC not really use it.

I made the mistake of getting 2 x 80 and 2 x 90 watt panels for $2/watt and an inexpensive 30A PWM charge controller for a little less than $100. So for the total cost of my 340 watts of panels & CC and combiner box (due to 4 panels) it came to ~$880 and I only get about 225 watts of generation.

I could have gotten a 225watt panel for about $250 and a 30A MPPT CC for about $300. That would have gotten me the same charging wattage and save more than $300.

Thanks, I am starting to understand this. But how long will the charge controller last? In the lifetime of a solar installation, how often do the electronics need to be replaced? In 20+ years I am on my second refrigerator, third dishwasher, third hot water heater, third TV, 5th computer, etc.

[SunEagle]

OK, I am evolving, and not sure in the right way. My first conclusion was that to take a 300w 8 amp panel and use an MPPT controller to get enough amps to charge two Trojan 105s at 20 amps. I am assuming I understand correctly that an MPPT would take the 300w/8a output of the panel and convert to 12 volts/20+ amps for the battery. That satisfies the minimum C/12 for the batteries.

However now I have a hair-brained idea. Could I take four 12v 100w/5.5a panels instead and get an output of 20+ amps without the MPPT? Then use the simpler cheaper PWM controller? Since the MPPT is not only more expensive but more likely to fail during the 20+ years of the lifetime of the solar panels, would I be ahead and would that work?

What I see is a trade off. It should cost much less for the 300 watt panel then 3 x 100 watt panels. Getting the 4th 100 watt panel would be adding more cost only to have that PWM CC not really use it.

I made the mistake of getting 2 x 80 and 2 x 90 watt panels for $2/watt and an inexpensive 30A PWM charge controller for a little less than $100. So for the total cost of my 340 watts of panels & CC and combiner box (due to 4 panels) it came to ~$880 and I only get about 225 watts of generation.

I could have gotten a 225watt panel for about $250 and a 30A MPPT CC for about $300. That would have gotten me the same charging wattage and save more than $300.

[lkruper]

PWM less expensive and more reliable than MPPT in some situations?

...

There are two two types of controllers on the market of PWM and MPPT..

PWM Input Current = Output Current which is really horrible and antiquated technology. You have to use expensive battery panels with them and you still get robbed. A 100 watt panel has a Vmp of 18 volts and Imp of 5.5 amps (100 watts = 18 volts x 5.5 amps) So put that 100 watt battery panel to a 12 volt battery and you get 5.5 amps of charge current. Do the math. 12 volts x 5.5 amps = 66 watts. ..

OK, I am evolving, and not sure in the right way. My first conclusion was that to take a 300w 8 amp panel and use an MPPT controller to get enough amps to charge two Trojan 105s at 20 amps. I am assuming I understand correctly that an MPPT would take the 300w/8a output of the panel and convert to 12 volts/20+ amps for the battery. That satisfies the minimum C/12 for the batteries.

However now I have a hair-brained idea. Could I take four 12v 100w/5.5a panels instead and get an output of 20+ amps without the MPPT? Then use the simpler cheaper PWM controller? Since the MPPT is not only more expensive but more likely to fail during the 20+ years of the lifetime of the solar panels, would I be ahead and would that work?

[Mike90250]

Willy T. Stop it.

This thread is related to discussion about lkruper's system. Not some theoretical system of 2V cells. or 4/O wire you started to get into with another poster.

If you can add to lkruper's learning, fine. If not, stop confusing the issue, or get banned. If you question Sunkings advice, question it, but don't bring up imaginary stuff that is not on the OP's topic.

We can chat about facts based on engineering all day. Science has one good answer, and many less good answers, we pick the ones we can afford.

Sunking, factual corrections are fine, catching things mods miss is fine, 1st grade name calling stops

[lkruper]

Ok let's get you some useful information you are missing. It should help. There are two basic kinds of solar panels: 12 volt Battery Panels, and Grid Tied Panels.

Battery panels have 36 cells which makes them fairly low voltage with an Vmp of 18 volts. With only 36 cells limits ther power to about 160 watt maximum.. Lastly they are expensive costing $2 to $8 per watt. None of that is and good and is antiquated technology. Good news is you do not have Battery Panels.

Grid Tied Panels are higher voltage, up to 80 cells, and power ratings up to 250 watts per panel. Additionally they are much less expensive than battery panels wiht cost of less than $1/watt if you are a good patient shopper. Only catch is you must use a MPPT controller. However even with the higher cost of a MPPT controller is more than enough offset by using GT panels and way more efficient.

There are two two types of controllers on the market of PWM and MPPT..

PWM Input Current = Output Current which is really horrible and antiquated technology. You have to use expensive battery panels with them and you still get robbed. A 100 watt panel has a Vmp of 18 volts and Imp of 5.5 amps (100 watts = 18 volts x 5.5 amps) So put that 100 watt battery panel to a 12 volt battery and you get 5.5 amps of charge current. Do the math. 12 volts x 5.5 amps = 66 watts. Now time for Fun and Educational. You have a 300 watt GT panel with an Imp = 8 amps and a 12 volt battery. How much did you screw yourself with a PWM controller? How many 300 watt panels does it take to get 300 watts to the battery with a PWM controller? Told you it was Fun Learning

MPPT Output Current = Panel Wattage / Battery Voltag Now do the math. A 100 Watt panel gives you 100 watts / 12 volts = 8.34 amps. What does a 300 watt GT panel give you? There is another huge advantage using MPPT controller. It is the magic of higher more efficient voltage. You can use a 120 volt panel array to charge your 12 volt battery. Say 3 330 watt 40 volt panels with an Imp of 8.25 amps. No fuses, no combiners, really small inexpensive wire between panels and controller. Cheap cheap cheap and very efficient with less than 2% line losses. Going out of the controller at 900 watts input with 12 volt battery you get 80 amps of charge current. That take larger wire of course but it is real short.

It takes a 300 watt PWM system to equal a 200 watt MPPT system. A 300 watt PWM system with a cheap PWM controller is going to cost you around $600 to $700 just for the two 150 watt panel and controller Requires twice the wiring. An Equivalent 200 watt MPPT system $400 tops using a single panel and a 20 amp controller for a 12 volt battery and ccan be expanded to 800 watts at 48 volt battery.

Do I have your attention yet?

Good now time for more Educational Fun. i will keep it short this time. If you use FLA batteries, anything you take off grid if you run it full time is going to cost you at least 5 times more than buying power from the POCO for the rest of you rlife just in battery replacement cost. Use it infrequently like a cabin many times more. Emergency some 100 times more.

Want AGM? Good they cost twice as much and last half as long or roughly 400% more than FLA.

Good thing about Emergency Power Systems you do not need as large of batteries as you need to run off solar. You just use cheap POCO power and use cheap LPG or Diesel fuel to run the genny for extended outages. Use all that money you save for beer, kids, and retirement.

Lets see if I understand. Does the 20 amp MPPT controller take the 37v 8a output of the panel and convert it to 12v and 25a (20)?

[Sunking]

My plan is to implement a manual transfer switch first and use the generator. I should really never need more than that at the cabin. However I also might not want to listen to the generator all the time and if I was stuck due to some natural disaster I could run out of gas.

The other part of the equation is that I am also interested in some day converting a van to a camper and having supplemental electrical capability. I am attempting to choose hardware that could do double duty. This potential secondary usage also makes me want to consider AGM batteries instead of FLA and also select an AC/DC fridge/freezer that can be added to the conversion.

And finally, solar interests me. I would like to learn more about it, more than just reading can give me, as well as making a conversion van which is capable of boon docking.

Now I need to learn about Vmp and Imp.

One of the panels I selected because I think I can pick it up in person is a Renogy.

•300 Watt (Pmax)
•37.46 Volts (Vmp)
•8.01 A (Imp)
•46.12 V (Voc)
•8.56 A (Isc)
•System Voltage: 24 V

### edit ###
If I need 20 amps or C/12 for 2 T105s, can MPPT raise the 8.01 A high enough or do I need to go with AGMs?
#########

Ok let's get you some useful information you are missing. It should help. There are two basic kinds of solar panels: 12 volt Battery Panels, and Grid Tied Panels.

Battery panels have 36 cells which makes them fairly low voltage with an Vmp of 18 volts. With only 36 cells limits ther power to about 160 watt maximum.. Lastly they are expensive costing $2 to $8 per watt. None of that is and good and is antiquated technology. Good news is you do not have Battery Panels.

Grid Tied Panels are higher voltage, up to 80 cells, and power ratings up to 250 watts per panel. Additionally they are much less expensive than battery panels wiht cost of less than $1/watt if you are a good patient shopper. Only catch is you must use a MPPT controller. However even with the higher cost of a MPPT controller is more than enough offset by using GT panels and way more efficient.

There are two two types of controllers on the market of PWM and MPPT..

PWM Input Current = Output Current which is really horrible and antiquated technology. You have to use expensive battery panels with them and you still get robbed. A 100 watt panel has a Vmp of 18 volts and Imp of 5.5 amps (100 watts = 18 volts x 5.5 amps) So put that 100 watt battery panel to a 12 volt battery and you get 5.5 amps of charge current. Do the math. 12 volts x 5.5 amps = 66 watts. Now time for Fun and Educational. You have a 300 watt GT panel with an Imp = 8 amps and a 12 volt battery. How much did you screw yourself with a PWM controller? How many 300 watt panels does it take to get 300 watts to the battery with a PWM controller? Told you it was Fun Learning

MPPT Output Current = Panel Wattage / Battery Voltag Now do the math. A 100 Watt panel gives you 100 watts / 12 volts = 8.34 amps. What does a 300 watt GT panel give you? There is another huge advantage using MPPT controller. It is the magic of higher more efficient voltage. You can use a 120 volt panel array to charge your 12 volt battery. Say 3 330 watt 40 volt panels with an Imp of 8.25 amps. No fuses, no combiners, really small inexpensive wire between panels and controller. Cheap cheap cheap and very efficient with less than 2% line losses. Going out of the controller at 900 watts input with 12 volt battery you get 80 amps of charge current. That take larger wire of course but it is real short.

It takes a 300 watt PWM system to equal a 200 watt MPPT system. A 300 watt PWM system with a cheap PWM controller is going to cost you around $600 to $700 just for the two 150 watt panel and controller Requires twice the wiring. An Equivalent 200 watt MPPT system $400 tops using a single panel and a 20 amp controller for a 12 volt battery and ccan be expanded to 800 watts at 48 volt battery.

Do I have your attention yet?

Good now time for more Educational Fun. i will keep it short this time. If you use FLA batteries, anything you take off grid if you run it full time is going to cost you at least 5 times more than buying power from the POCO for the rest of you rlife just in battery replacement cost. Use it infrequently like a cabin many times more. Emergency some 100 times more.

Want AGM? Good they cost twice as much and last half as long or roughly 400% more than FLA.

Good thing about Emergency Power Systems you do not need as large of batteries as you need to run off solar. You just use cheap POCO power and use cheap LPG or Diesel fuel to run the genny for extended outages. Use all that money you save for beer, kids, and retirement.

[lkruper]

My plan is to implement a manual transfer switch first and use the generator. I should really never need more than that at the cabin. However I also might not want to listen to the generator all the time and if I was stuck due to some natural disaster I could run out of gas.

The other part of the equation is that I am also interested in some day converting a van to a camper and having supplemental electrical capability. I am attempting to choose hardware that could do double duty. This potential secondary usage also makes me want to consider AGM batteries instead of FLA and also select an AC/DC fridge/freezer that can be added to the conversion.

And finally, solar interests me. I would like to learn more about it, more than just reading can give me, as well as making a conversion van which is capable of boon docking.

Now I need to learn about Vmp and Imp.

One of the panels I selected because I think I can pick it up in person is a Renogy.

•300 Watt (Pmax)
•37.46 Volts (Vmp)
•8.01 A (Imp)
•46.12 V (Voc)
•8.56 A (Isc)
•System Voltage: 24 V

### edit ###
If I need 20 amps or C/12 for 2 T105s, can MPPT raise the 8.01 A high enough or do I need to go with AGMs?
#########

[Sunking]

Yes, but remember also that I am grid-tied... Also, I will have my 2kW generator to use to supplement.

OK that makes a difference, a big one. With a generator why do you even need solar? All you would need is a Standard AC powered Charger operating on commercial power. If power fails th battery is already online. Otherwise the charge supplies the power. If power fails run the generator once a day if needed to recharge the batteries.

Thank you for noting that the charge controller I selected is not sufficient. I will make a change to my shopping list to get a 20 amp PWM controller and 10 AWG wire.

Do I understand you correctly?

Maybe not. A better idea is a MPPT controller. What panel wattage are you using, and what is the Vmp and Imp of the panels.

Vmp = voltage at maximum power.
Imp = current at maximum power.

[lkruper]

If your cabin is Part Time use no problem discharging to 50% DOD. Part Time would be weekends and no more than 3 days before leaving at 50% DOD. Otherwise shoot for 20 to 30 %/day

But there is a catch, Batteries need a minimum charge current of C/12 and on a Trojan T-105 that is 225 AH 12 = 19 amps. That is a minimum panel wattage of 20 watts with a 20 amp MPPT controller, and 300 watt 12 volt battery panels with 20 amp PWM controller. FWIW minimum 10 AWG wire requirement at 20 amps.

A pair of Trojans T-105 have a total capacity of 2.7 Kwh, or 1.35 each.

Yes, but remember also that I am grid-tied. With two exceptions in the last four years the power was never out for more than an hour or so and no more than ten times in about 1 year (I checked my pc logs). If I am not at the cabin and the power goes out the batteries will not kick in. If I am there I will employ them and it is only if there is an extended outage that I will need solar. If for some reason the power is out for longer and it is an emergency I will be more than happy to have them expend their lives for my comfort.

Also, I will have my 2kW generator to use to supplement.

Thank you for noting that the charge controller I selected is not sufficient. I will make a change to my shopping list to get a 20 amp PWM controller and 10 AWG wire.

Do I understand you correctly?

[Mike90250]

Because you can, if your only pulling it 25-30 % it"s easy. 15% of the daily recharge is non MPPT anyway. 150 amps your talking about is way overkill. Thats why they build generators and 4/0 cable.

Willy T.
YOU brought up the first mention of 4/O cable

ya'all are now warned.

LKruper - with your lister gensets,
with the older diesels , you have to be cautious of "Wet Stacking" if you run less than 60% load. Newer gensets don't have that much of a problem lightly loaded.

Your ST heads, are they internally wired in parallel for 120VAC, or for 240VAC ? They are sensitive to load imbalance if wired for 240, and you only load one side, the windings really growl and groan. You may want to consider 2, 120VAC chargers, one on each leg of the generator, to keep loads balanced.
see http://www.utterpower.com/genhead.htm for the mod
http://cgg1.com/index_htm_files/ST%20Manual-42013.pdf for the manual

I run a CS-6 with a ST-5 head @ 240VAC and use it to both run loads and the integral charger in my inverter (XW-6048) which also does load balancing for me too. Because of loading limits, I limit my charging to 30A to prevent overloading my engine.
30A @ 60V =1800w plus my base loads, and I'm at 1,400' elevation.

[Mike90250]

Alright, ease up both of you. I now am going back over the thread, and will have to prune it.

Keep comments relevant to the OPs topic, or don't comment.

Moderator

[Sunking]

I am still in the planning stages. I have three 9a AGM UPS style batteries, a small NOCO battery charger, a small Costco 15w panel with controller, a cheap Harbor Freight 400/800 noisy inverter and a volt-ohmmeter to practice with.

I am still researching what will be deployed for actual usage. At this point on my spreadsheet I am calculating that two T105's will power my load at 50% DOD for one day. We don't live at the cabin full time and it is quite possible that in the event of some sort of outage or disaster we won't even be there, but if we are, I would like a bare minimum of devices. Heat, light and cooking are taken care of with fireplace, oil lanterns, battery lanterns and camp stoves along with a stockpile of canned goods and Mountain House freeze dried meals and 55gal emergency water barrel.


I was going to go with a 250-300w panel and a Morningstar 15 amp MPPT controller. If I brought the 12v inside the cabin by cable to an inverter I was considering the MorningStar SureSine 300W because there is no fan and there would be no noise. I will also need a battery charger and also do have a 2kW gas inverter generator.

By the time I get batteries and solar, I was going to power the fridge with DC during a power outage.

Suggestions/corrections are welcome. I am still learning.

### edit ###
I think I can get a good three hours+ from a southern exposure in the summer because of trees which is about 20 feet from the basement where the batteries could be stored. Another 20 feet to where the electricity would be used or 10 feet to my 110v panel for a manual transfer switch.

Not sure what you mean by "Panel Wattage and Vmp?" .. would that be DC panel?

###

If your cabin is Part Time use no problem discharging to 50% DOD. Part Time would be weekends and no more than 3 days before leaving at 50% DOD. Otherwise shoot for 20 to 30 %/day

But there is a catch, Batteries need a minimum charge current of C/12 and on a Trojan T-105 that is 225 AH 12 = 19 amps. That is a minimum panel wattage of 20 watts with a 20 amp MPPT controller, and 300 watt 12 volt battery panels with 20 amp PWM controller. FWIW minimum 10 AWG wire requirement at 20 amps.

A pair of Trojans T-105 have a total capacity of 2.7 Kwh, or 1.35 each.

[lkruper]

That does not require 4/0 , more like 12 AWG.

What size Inverter and battery do you have other than 12 volt?

Panel Wattage and Vmp?
Distance between Panel/Controller
Distance between Controller/Inverter
Battery capacity.
Invert er wattage or do you run DC direct?

I am still in the planning stages. I have three 9a AGM UPS style batteries, a small NOCO battery charger, a small Costco 15w panel with controller, a cheap Harbor Freight 400/800 noisy inverter and a volt-ohmmeter to practice with.

I am still researching what will be deployed for actual usage. At this point on my spreadsheet I am calculating that two T105's will power my load at 50% DOD for one day. We don't live at the cabin full time and it is quite possible that in the event of some sort of outage or disaster we won't even be there, but if we are, I would like a bare minimum of devices. Heat, light and cooking are taken care of with fireplace, oil lanterns, battery lanterns and camp stoves along with a stockpile of canned goods and Mountain House freeze dried meals and 55gal emergency water barrel.


I was going to go with a 250-300w panel and a Morningstar 15 amp MPPT controller. If I brought the 12v inside the cabin by cable to an inverter I was considering the MorningStar SureSine 300W because there is no fan and there would be no noise. I will also need a battery charger and also do have a 2kW gas inverter generator.

By the time I get batteries and solar, I was going to power the fridge with DC during a power outage.

Suggestions/corrections are welcome. I am still learning.

### edit ###
I think I can get a good three hours+ from a southern exposure in the summer because of trees which is about 20 feet from the basement where the batteries could be stored. Another 20 feet to where the electricity would be used or 10 feet to my 110v panel for a manual transfer switch.

Not sure what you mean by "Panel Wattage and Vmp?" .. would that be DC panel?

###

[Sunking]

Yes, 1304 Wh per day. I have cut down my "essential" devices to have powered during an outage to a DSL modem (6w) , Satellite dish (19w), low power TV (28w), DC fridge (28w 1/3 cycle), a few led lights, charging for IPAD, phone, etc.

That does not require 4/0 , more like 12 AWG.

What size Inverter and battery do you have other than 12 volt?

Panel Wattage and Vmp?
Distance between Panel/Controller
Distance between Controller/Inverter
Battery capacity.
Invert er wattage or do you run DC direct?

[lkruper]

That does not make any sense. Do you mean 110 Amp Hours per day?

Amps is a measure of current flowing at any specific moment. It has no time associated with it. Like watts, it is just measure of rate of power being used at any moment in time, it does not tell you how much energy you are using over a period of time which is Watt Hours.

If you are only using 110 Amp Hours per day at 12 volts, you are likely drawing very small currents. example 4.58 amps x 24 hours = 110 Amp Hours, and at 12 volts is only 55 watts x 24 hours = 1.3 Kwh per day. Well unless you are pulling 110 amps x 1 hour in a day.

Yes, 1304 Wh per day. I have cut down my "essential" devices to have powered during an outage to a DSL modem (6w) , Satellite dish (19w), low power TV (28w), DC fridge (28w 1/3 cycle), a few led lights, charging for IPAD, phone, etc.