Connect parallel and series the batteries at the same time
mulia
Solar Expert Posts: 62 ✭✭✭✭
Hi,
I'm new to solar system and learn lots from internet.
I bought 5 solar panel with Vpm 18V and lpm 5.58A recently and they're on the way.
I also bought a PWM morningstar PS-30M charge controller (this one my mistake, it won't be able 5 panels when it's full bright) and a 12V Xantrex 1000W Inverter.
Next week, I planned to buy 2 12V 200AH flooded batteries for this system.
Since I've bought a 12V inverter, I won't be able to configure my system to be a 24V system with PWM CC.
So I planned to serial and parallel the batteries at the same time and with the same terminal.
I've seen lots parallel and serial combination on internet but haven't seen (perhaps yet) this type of connection.
Can anyone please help me, take a look to the wiring and help me to determine if this combination will succeed and working properly or it will bring explosion or short circuit? (ah btw, I'll ensure all of them fused properly)
Attachment not found.
Thank you in advance.
I'm new to solar system and learn lots from internet.
I bought 5 solar panel with Vpm 18V and lpm 5.58A recently and they're on the way.
I also bought a PWM morningstar PS-30M charge controller (this one my mistake, it won't be able 5 panels when it's full bright) and a 12V Xantrex 1000W Inverter.
Next week, I planned to buy 2 12V 200AH flooded batteries for this system.
Since I've bought a 12V inverter, I won't be able to configure my system to be a 24V system with PWM CC.
So I planned to serial and parallel the batteries at the same time and with the same terminal.
I've seen lots parallel and serial combination on internet but haven't seen (perhaps yet) this type of connection.
Can anyone please help me, take a look to the wiring and help me to determine if this combination will succeed and working properly or it will bring explosion or short circuit? (ah btw, I'll ensure all of them fused properly)
Attachment not found.
Thank you in advance.
Comments
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Re: Connect parallel and series the batteries at the same time
You've just created a dead short on battery on battery #2!
The cables are filling the air with smoke and the battery is about to explode.
How is it a short circuit? You've got a cable going from Batt #2 +, to batt #1 neg, and also a cable from Batt #2 Neg, also going to batt #1 Neg. BINGO! Short circuited battery #2.
Sorry, you can't have your cake and eat it too.
OH, and now that I have that out of the way - - welcome to the forum -
Re: Connect parallel and series the batteries at the same time
Arghhh..... why that part don't come to my mind when drawing this connection diagram...
I started to feel depressed...
I took a mistake by first designing this system to 12V but later learn that 24V much more efficient in wiring and I can keep using my 30A CC without buying new higher A CC by doubling the V of Panel, not the A.
But unfortunately, I've bought a 12V inverter and that's big mistake, since it's expensive to buy another inverter (I live in Asia, bought the inverter through e**y from US, ship cost and import duty knocked me down)
Will anyone please suggest me how to draw that 12V power for the inverter without buying any new CC or inverter?
@ waynefromnscanada: thanks for the greeting....
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Re: Connect parallel and series the batteries at the same time
Nothing wrong, it will handle all 5 panels at 12 volts(10 at 24volts) in a PWM charge controller(CC) the amperage 'passes through' so 5(panels) x 5.58 VMP = <30amps(rating of the CC)I bought 5 solar panel with Vpm 18V and lpm 5.58A recently and they're on the way.
I also bought a PWM morningstar PS-30M charge controller (this one my mistake, it won't be able 5 panels when it's full bright)
This is an odd size in the US where are you located?Next week, I planned to buy 2 12V 200AH flooded batteries for this system.
Correct, you can only do parallel OR series with 2 batteries, unless you plan to switch them back and forth while charging vs while using. Other wise as Wayne said dead short, smoke, heat...Since I've bought a 12V inverter, I won't be able to configure my system to be a 24V system with PWM CC.
So I planned to serial and parallel the batteries at the same time and with the same terminal.
I've seen lots parallel and serial combination on internet but haven't seen (perhaps yet) this type of connection.
You can just hook them up parallel, and charge as a single 12 volt battery bank and use as a 12 volt battery bank...Can anyone please help me, take a look to the wiring and help me to determine if this combination will succeed and working properly or it will bring explosion or short circuit? (ah btw, I'll ensure all of them fused properly)Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same time
You would loose more power trying to hook up just 4 panels to charge 24 volts than 5 panels for a 12 volt array.
You should hook up your batteries like this, so there is equal resistance for both, this will aid in equal charging;
Attachment not found.Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same timeNothing wrong, it will handle all 5 panels at 12 volts(10 at 24volts) in a PWM charge controller(CC) the amperage 'passes through' so 5(panels) x 5.58 VMP = <30amps(rating of the CC)
I recalculated my system requirement and I found out that I need more panels soon, it means that my CC won't be able to handle expansion in near future. That's why I learn to build it as 24V so I can use more panels with the same CC.This is an odd size in the US where are you located?
I live in Indonesia. That's size of flooded battery of trusted Japan brand I can found.Correct, you can only do parallel OR series with 2 batteries, unless you plan to switch them back and forth while charging vs while using. Other wise as Wayne said dead short, smoke, heat...
I can't do that since this will be off-grid system so the batteries will be charged and used at the same time.
How about doing it with more than 2 batteries? I can add more batteries in order to quality the diagram to meet 12V output for the inverter.You can just hook them up parallel, and charge as a single 12 volt battery bank and use as a 12 volt battery bank...
Yes, it will be fine if to keep with 12V, unfortunately, it's hard when I need to upgrade it to 24V system. -
Re: Connect parallel and series the batteries at the same timeYou would loose more power trying to hook up just 4 panels to charge 24 volts than 5 panels for a 12 volt array.
You should hook up your batteries like this, so there is equal resistance for both, this will aid in equal charging;
Attachment not found.
With this wiring, I'll get 12V and 400AH, it's fine. But I won't take advantage from efficiency gained by 24V system (less gauge wire, more panel with small A CC).
Hmm... should I just stick with my 12V plan system and buy new CC for future panels? -
Re: Connect parallel and series the batteries at the same timeWith this wiring, I'll get 12V and 400AH, it's fine. But I won't take advantage from efficiency gained by 24V system (less gauge wire, more panel with small A CC).
Hmm... should I just stick with my 12V plan system and buy new CC for future panels?
It is difficult to say... If your solar array is close to the charge controller/battery bank--Then your cable does not have to be too large of diameter (more copper, more money).
You did not say what wattage inverter you are using... Roughly 1,200 Watts is about the maximum I would want to draw from a 12 volt battery bank (~100 Amps nominal)--That is a lot of current.
for a 400 AH @ 12 volt battery bank, a C/5 discharge is about the largest Inverter I would ever suggest connecting to that size bank:
12 volts * 400 AH * 1/5 hour discharge = ~960 Watts "useful" maximum inverter for flooded cell lead acid battery bank
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: Connect parallel and series the batteries at the same time
Your charge controller will handle 30 amps, so at 24 volts it will handle 10 panels as you described (5.58 amps 18 vmp).
24 volt is more efficient system wide, wiring and tare wattage per amp for inverter and charge controller. With out knowing what you need, it's hard to say if you need to change CC. If a system based on around a 1000 watt array will handle your needs, you may be fine with a 24 volt battery bank and your current CC.
If you want to setup a 24 volt system now, you can only use 4 of the panels you currently have, since they will have to be connected 2 in series, to reach charging voltage for a 24 volt system (35-6 VMP). So with what you have now, I suggested leaving it as a 12 volt system. If a this size battery bank 2 - 200amp 2 volt batteries, will meet your storage needs, it could be changed later to 24 volt with the same available power.
Normally, it is advised that you decide what your needs are, and design a system around it. If you would like to start over and tell us what your power needs are, perhaps we could help you design a system to meet your needs.Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same timeIt is difficult to say... If your solar array is close to the charge controller/battery bank--Then your cable does not have to be too large of diameter (more copper, more money).
You did not say what wattage inverter you are using... Roughly 1,200 Watts is about the maximum I would want to draw from a 12 volt battery bank (~100 Amps nominal)--That is a lot of current.
for a 400 AH @ 12 volt battery bank, a C/5 discharge is about the largest Inverter I would ever suggest connecting to that size bank:
12 volts * 400 AH * 1/5 hour discharge = ~960 Watts "useful" maximum inverter for flooded cell lead acid battery bank
-Bill
I use 1000Watt inverter. Although I will only use about 800watt for maximal usages.
I still wondering if my 500watt panel will be able to cover my 800watt daily need with 5 hours full sunlight with 400AH batteries? without any winter.
I'm still working out for the best position, but I'll keep those expensive panels away from neighbor children, they love to mischief.
For the cable, I've ordered a roll of 50meters 2x4mm NYY cable, I'll use conduit to protect them from direct sunlight. I hope it will be fine since it should be able to hold more than 50A current.Your charge controller will handle 30 amps, so at 24 volts it will handle 10 panels as you described (5.58 amps 18 vmp).
24 volt is more efficient system wide, wiring and tare wattage per amp for inverter and charge controller. With out knowing what you need, it's hard to say if you need to change CC. If a system based on around a 1000 watt array will handle your needs, you may be fine with a 24 volt battery bank and your current CC.
If you want to setup a 24 volt system now, you can only use 4 of the panels you currently have, since they will have to be connected 2 in series, to reach charging voltage for a 24 volt system (35-6 VMP). So with what you have now, I suggested leaving it as a 12 volt system. If a this size battery bank 2 - 200amp 2 volt batteries, will meet your storage needs, it could be changed later to 24 volt with the same available power.
Normally, it is advised that you decide what your needs are, and design a system around it. If you would like to start over and tell us what your power needs are, perhaps we could help you design a system to meet your needs.
Exactly, that's what encourage me to start over my system that haven't even built yet. I did stupid mistake for hurriedly buy panel, 30A CC and 12V inverter before learning that 24 is much more better and cost efficient than 12V.
Currently, 2 issues brought to surface at the moment
1) I will need to buy new CC to add more panels, but I can keep the same CC if move to 24V.
2) I already bought 12V inverter which can't be used with 24V system.
Basically I need to use around 800watt power per day for well pump, refrigerator, tv and lighting. I'm afraid 400AH won't meet my requirement.
I'll appreciate any suggestion the best way to work out with devices I already bought. Since buying goods from abroad is really expensive in shipping and import duty while all stores in local sell only low quality products (don't expect Xantrex, SMA, SolarEdge, Studer or any good brand readily available). -
Re: Connect parallel and series the batteries at the same time
Do yourself a favour: bite the bullet and buy the 24 Volt inverter. The well pump and refrigerator are large loads that will make less demand on the batteries @ 24 Volts than @ 12 Volts.
You will need an even number of those panels for 24 Volt configuration in order to have an array Vmp high enough. Six of those 100 Watt panels may not be sufficient, however; you should have eight (four parallel strings of two in series, with fuse or breaker on each string). At six panels the charge rate would be 16.5 Amps or 8%. Eight panels will give you 22 Amps or 11%.
200 Amp hours @ 24 Volts is a fair amount of power. You should have up to 2kW hours AC available there. Depending on how much you can 'draw direct' from the array (i.e. use during daylight hours) it may work. My own system is slightly larger and runs refrigeration and water pump as well as other items, but with careful load management. -
Re: Connect parallel and series the batteries at the same timeCariboocoot wrote: »Do yourself a favour: bite the bullet and buy the 24 Volt inverter. The well pump and refrigerator are large loads that will make less demand on the batteries @ 24 Volts than @ 12 Volts.
You will need an even number of those panels for 24 Volt configuration in order to have an array Vmp high enough. Six of those 100 Watt panels may not be sufficient, however; you should have eight (four parallel strings of two in series, with fuse or breaker on each string). At six panels the charge rate would be 16.5 Amps or 8%. Eight panels will give you 22 Amps or 11%.
200 Amp hours @ 24 Volts is a fair amount of power. You should have up to 2kW hours AC available there. Depending on how much you can 'draw direct' from the array (i.e. use during daylight hours) it may work. My own system is slightly larger and runs refrigeration and water pump as well as other items, but with careful load management.
I bought the inverter from eBay, since he hasn't ship it yet, I'll try to contact him if he will let me to change it(I didn't find 24V version in his store) or cancelled it (very hard, small chance he will let me to cancelled the item).
Okay, regarding the panel, I'll for sure add more panels, how about adding 245W panel rather than more 100W? Will it be better?
Need to sleep now, almost midnight here. Thank you for everyone for your attention and helps, I really appreciated it.
Will reply tomorrow.. -
Re: Connect parallel and series the batteries at the same timeOkay, regarding the panel, I'll for sure add more panels, how about adding 245W panel rather than more 100W? Will it be better?
This is unlikely to work. A 245 Watt panel will probably be "GT style"; i.e. have a Vmp around 30. That is too low for a 24 Volt system, too high for a 12 Volt system, and not compatible with the 100 Watt panels you already have.
It could supply some current during Bulk stage when the batteries are lower than the panel's Vmp, but it is not a good match. -
Re: Connect parallel and series the batteries at the same timeCariboocoot wrote: »This is unlikely to work. A 245 Watt panel will probably be "GT style"; i.e. have a Vmp around 30. That is too low for a 24 Volt system, too high for a 12 Volt system, and not compatible with the 100 Watt panels you already have.
It could supply some current during Bulk stage when the batteries are lower than the panel's Vmp, but it is not a good match.
Indeed, it's around 30.
Attachment not found.
If it's not compatible with my 100W panel nor for 24V system
, then for what voltage system it's intended for?Cariboocoot wrote: »That is too low for a 24 Volt system
But 30V, it's too high for 12V too...*confused
How about 135W panel?
It's rated 7.35A and 17.35V. -
Re: Connect parallel and series the batteries at the same timeIndeed, it's around 30.
Attachment not found.
If it's not compatible with my 100W panel nor for 24V system , then for what voltage system it's intended for?
But 30V, it's too high for 12V too...*confused
How about 135W panel?
It's rated 7.35A and 17.35V.
This is why they are called "GT style" panels: 30-ish Vmp works fine on Grid-Tie systems which have no batteries. Twelve in a string gives a Vmp around 360 which is the usual operating Voltage for a GT inverter.
Standard battery system panels will have a Vmp in the 17-18 range or around 2X that for "true" 24 Volt panels. This gives the right amount of Voltage above charging level to allow for typical losses due to panel heating and wiring without seriously affecting power. -
Re: Connect parallel and series the batteries at the same time
It is intended for grid tied system, when there are several panels in series and used with a MPPT type charge controller.
You can get an MPPT type charge controller which will allow it to be used for battery based system, but the controller cost a good bit more than PWM type.
Your not looking for the wattage of the panel, rather a panel with similar VMP to the panels you currently have. @17.5 vmp for 12 volt charging and @35 vmp for 24 volt charging... and , like batteries, you can run 2 17.5 vmp panels in a string to get 35 vmp.Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same timeCariboocoot wrote: »This is why they are called "GT style" panels: 30-ish Vmp works fine on Grid-Tie systems which have no batteries. Twelve in a string gives a Vmp around 360 which is the usual operating Voltage for a GT inverter.
Standard battery system panels will have a Vmp in the 17-18 range or around 2X that for "true" 24 Volt panels. This gives the right amount of Voltage above charging level to allow for typical losses due to panel heating and wiring without seriously affecting power.
Oh, I got it.
So the right panel to charge 24V battery system is about 35-36Vmp?
Which is my 100W in series to produce that 35-36Vmp.
Unfortunately we have blackout everyday in this corrupt bureaucracy country so grid-tie system won't fit, and also our monopolized utility company don't have meter to support grid-tie system.It is intended for grid tied system, when there are several panels in series and used with a MPPT type charge controller.
You can get an MPPT type charge controller which will allow it to be used for battery based system, but the controller cost a good bit more than PWM type.
Your not looking for the wattage of the panel, rather a panel with similar VMP to the panels you currently have. @17.5 vmp for 12 volt charging and @35 vmp for 24 volt charging... and , like batteries, you can run 2 17.5 vmp panels in a string to get 35 vmp.
Hmm.. unfortunately for me, already bought a PWM controller, because most article I read, PWM will extend life of battery better than MPPT although MPPT could harvest sunlight better.
Excellent, once I got my 24V inverter, and those panels arrived, I'll arranged 4 of them to series and parallel to earn 35vmp and arranged the battery to 24V.
Can anyone please recommend a good 24V inverter off grid?
I got replied from the seller that he don't have a 24V version of that Xantrex and agreed to refund me and cancel the transaction.
At the moment, I will need a 24V inverter off-grid from trusted brand but not to drain my budget, sorry, solar system really cost much for people from third world country.
I will use around 800Watt power daily. So it's okay for the inverter around 1000W.
And btw, I hope you can also recommend me good website to buy it from with international shipping available.
Most of stores I searched, sell inverter with overpriced price, worse, don't ship outside US (for US site), and won't ship outside Aus (for Aus site). -
Re: Connect parallel and series the batteries at the same timeHmm.. unfortunately for me, already bought a PWM controller, because most article I read, PWM will extend life of battery better than MPPT although MPPT could harvest sunlight better.
I don't know where you read that but it isn't true. The major difference between the two types is the MPPT's ability to down-convert higher Voltage. In terms of regulating that Voltage they both work the same way; by rapidly switching the panel connection on and off.Can anyone please recommend a good 24V inverter off grid?
Budget and availability play a big role in that. You ca spend a few thousand or a few hundred. The difference will be the size and features.I got replied from the seller that he don't have a 24V version of that Xantrex and agreed to refund me and cancel the transaction.
Well that is good. Nothing worse than being stuck with a piece of equipment that doesn't suit.At the moment, I will need a 24V inverter off-grid from trusted brand but not to drain my budget, sorry, solar system really cost much for people from third world country.
I will use around 800Watt power daily. So it's okay for the inverter around 1000W.
Now let's talk terminology.
You may use a maximum of 800 Watts at any given time, necessitating a 1000 Watt inverter.
The amount of power you use is in Watt hours and has little bearing on the inverter choice other than being a factor in Voltage.And btw, I hope you can also recommend me good website to buy it from with international shipping available.
Most of stores I searched, sell inverter with overpriced price, worse, don't ship outside US (for US site), and won't ship outside Aus (for Aus site).
Our host NAWS http://www.solar-electric.com/ says they ship to "about 40 other countries". I don't know which one you're in but it may make quite a difference. Some of the forum members are in other countries as well and may have experience that could help you out.
BTW the country you are in will make a difference on inverter choice as well, as not all countries use the same power standard. Some (like Japan) have two different standards in the same country. -
Re: Connect parallel and series the batteries at the same time
Some vendors do claim that PWM controllers are better--They send "pulsed power" to the battery bank like a Desulfator.
Desulfators, by themselves are a very hot button topic. Lots of claims, but not too much proof that they work as well as claimed.
In general, no reason to buy a PWM controller over a MPPT controller except that PWM controllers are less costly and simpler (less to go wrong). And can be less "electrically noisy" than MPPT controllers. For example, some MorningStar models have a switch that change from standard PWM operation (cycling 100's to 1,000's of times a second "on/off") to on/off every few seconds. Less radio and audio interference--Intended for powering telephone power systems with solar.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: Connect parallel and series the batteries at the same time
Hmm.. unfortunately for me, already bought a PWM controller, because most article I read, PWM will extend life of battery better than MPPT although MPPT could harvest sunlight better.
My previous set of L-16 batteries lasted 12 years I think it was. The first couple of years they were regulated by a "home made" shunt regulator. The next roughly 5 years it was commercial PWM, and the final 6 years they were fed from a MX-60 MPPT controller.
Hummmm - - maybe if I had stuck with PWM they'd still be going ? Just joking of course.
To be honest, after using both, I'd never go back to PWM, the MPPT is far superior for my situation. And no, I never did use a "desulphator" and certainly won't now.
12 years is a ripe old age for everyday L-16 batteries, excellent really, especially considering the average life of the batteries I had was 5 to 7 years and they had been abused several times through error and ignorance on my part. They were in reality, my "learning" batteries. And yes, I'm still learning and there's no end in sight in that regard. -
Re: Connect parallel and series the batteries at the same timewaynefromnscanada wrote: »My previous set of L-16 batteries lasted 12 years I think it was. The first couple of years they were regulated by a "home made" shunt regulator. The next roughly 5 years it was commercial PWM, and the final 6 years they were fed from a MX-60 MPPT controller.
Hummmm - - maybe if I had stuck with PWM they'd still be going ? Just joking of course.
To be honest, after using both, I'd never go back to PWM, the MPPT is far superior for my situation. And no, I never did use a "desulphator" and certainly won't now.
12 years is a ripe old age for everyday L-16 batteries, excellent really, especially considering the average life of the batteries I had was 5 to 7 years and they had been abused several times through error and ignorance on my part. They were in reality, my "learning" batteries. And yes, I'm still learning and there's no end in sight in that regard.
That's really amazing long life for a battery. I do think that it's really depends on quality of the battery.
I don't think such good battery still exist these days..
If it's so very superior.... hmm.. I'll use MPPT once my system unable to fit with my 30A CC.Some vendors do claim that PWM controllers are better--They send "pulsed power" to the battery bank like a Desulfator.
Desulfators, by themselves are a very hot button topic. Lots of claims, but not too much proof that they work as well as claimed.
In general, no reason to buy a PWM controller over a MPPT controller except that PWM controllers are less costly and simpler (less to go wrong). And can be less "electrically noisy" than MPPT controllers. For example, some MorningStar models have a switch that change from standard PWM operation (cycling 100's to 1,000's of times a second "on/off") to on/off every few seconds. Less radio and audio interference--Intended for powering telephone power systems with solar.
-Bill
True, it's what I read from when browse around to decide to take MPPT or PWM.
So is PWM is really bad thing?
I saw lots of people are moving to MPPT these days, is it really needed to move to MPPT?
Since MPPT and PWM disparity price are getting smaller and smaller.Cariboocoot wrote: »I don't know where you read that but it isn't true. The major difference between the two types is the MPPT's ability to down-convert higher Voltage. In terms of regulating that Voltage they both work the same way; by rapidly switching the panel connection on and off.
They could be wrong off course.
Attachment not found.
I think I'll take MPPT next time for a better efficiency.Cariboocoot wrote: »Budget and availability play a big role in that. You ca spend a few thousand or a few hundred. The difference will be the size and features.
I've just decided to inquiry about 24Vdc 230VAC Xantrex Inverter 1000W, it cost less than $1k with shipping. What I'm not so happy about them is that they use cooling fan. I'm afraid when the cooling fan died, I'll need to ship the unit overseas just to change the fan and that's not cost efficient (nor funny). What do you think about that?Cariboocoot wrote: »Now let's talk terminology.
You may use a maximum of 800 Watts at any given time, necessitating a 1000 Watt inverter.
The amount of power you use is in Watt hours and has little bearing on the inverter choice other than being a factor in Voltage.
Hmm.. I didn't get it. Will the Xantrex 1000W fulfill my need?
I'm still confused with how the inverter work when the load is not full.
If the inverter keep drawing load from battery to produce stable 1000W, I'm afraid my battery won't be able to fulfill it.
But, if the inverter only take necessary load, say I'm using 300W device at the moment, then the inverter only draw current from battery enough to supply that 300W load, then I'll have more reserved power than I need if I manage the load closely. Maybe you can help me with this? -
Re: Connect parallel and series the batteries at the same time
A 1000 Watt inverter can supply loads up to a total of 1000 Watts. Watts is a rate, not a quantity. Therefor you do not use 800 Watts in a day, but you may use 800 Watts at a time. Watts over hours is Watt hours: a quantity. Use 800 Watts for half an hour and you've consumed 400 Watt hours.
So an inverter is sized to handle all the loads you might want to run at once: 100 Watts for lights + 50 Watts for computer + 120 Watts for refrigerator (et cetera) totaling 270 Watts (or whatever). This must include start-up surges too: a refrigerator may run at 120 Watts but needs 1kW or possibly more just to start the compressor. If the inverter can not supply that start surge (along with concurrent loads) it will fault and shut down.
When not fully loaded an inverter supplies whatever power is required, as well as consuming its own power needs. So if the inverter uses 20 Watts and the load is 20 Watts the total coming from the batteries is 40 Watts. When supplying its full power, say 2000 Watts, it will still use 20 Watts to run the inverter. Total: 2020 Watts.
Just to make it a bit more complicated there is a conversion loss specific to the inverter. So 100 Watts of AC load may actually take 117 Watts from the battery due to the conversion loss - not including the inverters power needs. Thus 100 Watts ends up pulling 137 Watts from the battery. Exactly how much depends on the particular inverter; some have higher self-consumption, some lower. Some have better conversion efficiency than others.
But wait, there's more! Power Factor can come into play with induction loads like AC motors. This little bit of ugliness causes the current maximum to be drawn at a point other than the Voltage maximum, making the demand on the inverter higher than it would appear to be. The safest way around this is to not load inverters to their maximum rated output (which is really in Volt Amps: Watts with the Power Factor applied).
On the battery output things are not cut-and-dried either, because a battery's real at-the-moment capacity depends on the rate at which current is being drawn. Higher current = lower capacity. The 20 Hour ratings we use to compare sizes and determine charging are based on a steady current draw as Voltage falls off over time. This doesn't happen in the real world; only in testing labs. In the real world the loads are in Watts and as the Voltage drops because the battery is discharging the current rate goes up to meet the Watt demand, effectively reducing the real capacity moment by moment. You can go crazy trying to comprehend this. So we fall back on averages and fudge factors to make it work. One of the factors is the maximum discharge current a battery can take, which sets a limit for how large a load it can handle at a given moment. For flooded cells this is usually about 25% of the 20 hour capacity. Higher discharge rate can cause too much Voltage sag and the inverter may 'see' low Voltage and shut down.
Confused enough?
BTW it is normal for inverters to have cooling fans. Almost all of them do. A few of the smaller ones do not. -
Re: Connect parallel and series the batteries at the same timeTrue, it's what I read from when browse around to decide to take MPPT or PWM.
So is PWM is really bad thing?
I saw lots of people are moving to MPPT these days, is it really needed to move to MPPT?
Since MPPT and PWM disparity price are getting smaller and smaller.
Roughly, for systems smaller than 400 Watts of solar panels--PWM and "12 volt" solar panels are generally more cost effective.
For systems >800 watts of solar panels--Genarally MPPT contorllers+GT type solar panels (Vmp typically in the 30-40 volt range or so) are more cost effective and easier to wire out systems (Vmp-array higher, smaller gauge wire from array to charge controller+battery shed required).
Also MPPT controllers tend to have more bells and whistles (Internet Webserver, more charging options, data logs, upgradable software, remote battery temperature sensors, integration with other controllers/components, etc.).
Do a paper design of several system configurations/options and see what works best for your needs.I've just decided to inquiry about 24Vdc 230VAC Xantrex Inverter 1000W, it cost less than $1k with shipping. What I'm not so happy about them is that they use cooling fan. I'm afraid when the cooling fan died, I'll need to ship the unit overseas just to change the fan and that's not cost efficient (nor funny). What do you think about that?
I am not happy with cooling fans either... Draws in dust/bugs/humidity. Fans do fail. On the other hand, makes for cheaper/more compact AC inverter/charge controllers.Hmm.. I didn't get it. Will the Xantrex 1000W fulfill my need?
Depends on your loads... Generally, smaller AC inverters are fine until you have some "serious" loads--Typically AC Refrigerators and Well pumps. It is not unusual for an AC Induction Motor to draw 5x its average load (120 watt refrigerator draws >600 VA starting). In general, a 1,200-1,500 Watt AC inverter (true sine wave recommended for various reasons--although more costly) is about the minimum that most people will find satisfactory (start/run a modern US Energy Star full size refrigerator).I'm still confused with how the inverter work when the load is not full.
The inverter has electronics and some sort of transformer on the output. It takes power to just turn the stuff on even of there are no loads (6 watts is typical for smaller inverter--Say 300 to 600 Watts). 10-20-40 Watts is not unusual as you go 1,000-4,000+ Watts.
MSW inverters typically have about 1/2 the "idle" losses vs TSW inverters... But motors (and some other items like transformers and some power supplies) run hotter on MSW inverters--Induction motors can draw as much as 20% more power (waste heat, hotter motors) on MSW (modified square wave) inverters.If the inverter keep drawing load from battery to produce stable 1000W, I'm afraid my battery won't be able to fulfill it.
But, if the inverter only take necessary load, say I'm using 300W device at the moment, then the inverter only draw current from battery enough to supply that 300W load, then I'll have more reserved power than I need if I manage the load closely. Maybe you can help me with this?
Yep--If you run a 300 Watt TSW inverter 24 hours per day an run your load 5 hours per day at 150 Watts (making up numbers) for DC loads:
24 hours * 6 watts Tare losses = 144 WH per day
5 hours * 150 Watts AC load * 1/0.85 inverter eff = 882 WH per day
=============================================
Total = 1,026 Watt*Hours of DC battery bus load
The larger your AC inverter and less power/time you draw power for your loads--The more losses--And the larger solar array+battery bank needed to support those loads.
There are other ways to address the problems too... One is an inverter with "Search Mode"... The inverter turns on ~once per second for 1 cycle of 60 Hz 120 VAC power. Allows the inverter to draw much less power--And if the AC power draw is >~6watts, the inverter turns on full and runs the loads.
This can work well for loads that turn on and off. But no help for things that require AC power 24x7 (Energy Star refrigerators typically have a defrost timer, running networks, computers, etc.).
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: Connect parallel and series the batteries at the same timeRoughly, for systems smaller than 400 Watts of solar panels--PWM and "12 volt" solar panels are generally more cost effective.
-Bill
You know what, Bill? This is getting to be "no longer true" with the changes in prices.
When you can buy GT style panels for <$1 per Watt and a MidNite Kid for <$300, then compare that to the cost of 'standard' panels at around $2 per Watt ... the 'tipping point' has moved even lower now.
Example:
Two 140 Watt Kyoceras $275 each (total $550) output 15 Amps on a SunSaver 20 Amp PWM for $84: $634
One 280 Watt Solarworld $335 output 18 Amps on a MidNite Kid 30 Amp MPPT for $285: $620
Of course there are other factors, but from a price-per-Watt perspective we've gone down 100 Watts in where MPPT is economically feasible! -
Re: Connect parallel and series the batteries at the same time
Until you add the Remote Meter and Remote Battery Temperature Sensor (really needed for the small MorningStar MPPT controller):
Morningstar RM-1 Remote Digital Meter For SunSaver-Duo, MPPT-15A and SureSine-300 Inverter $77
Morningstar Controller Remote Temperature Probe $28
Another $100...
Also, shipping of single solar panels is expensive... And the freight options for ~140 Watt and smaller panels are greater (UPS, Bus, etc.) vs the large format panels that need to ship by truck (usually).
Why costing of multiple systems/options + shipping and handling to your door step.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: Connect parallel and series the batteries at the same time
Well the BTS for the Kid is another $20.
But panel shipping would be the big issue for cost.
If you can pick up at the store/outlet you will save a lot no matter which way you go.
When you up the size to what would work best for a pair of GC2's you get this:
Two 190 Watt Topoint @ $218 + Kid @ $285 = $721 (24 Amps output)
Or
Three 140 Watt Kyoceras @ $275 + ProStar 30 @ $121 = $946 (23.7 Amps output)
At that point the shipping and accessories become minor influences because you're saving over $200 with the MPPT design.
It pays to look at a few design options and shop around for prices. -
Re: Connect parallel and series the batteries at the same timeCariboocoot wrote: »You know what, Bill? This is getting to be "no longer true" with the changes in prices.
When you can buy GT style panels for <$1 per Watt and a MidNite Kid for <$300, then compare that to the cost of 'standard' panels at around $2 per Watt ... the 'tipping point' has moved even lower now....
but from a price-per-Watt perspective we've gone down 100 Watts in where MPPT is economically feasible!
I agree that "The Kid" is a game changer, mostly in it's low power usage, I use to recommend the Midnite classic for most any 1000Kw system, but it's heavy power usage, makes it pretty much a no go for 12 volt systems.
Also, though the field is thinning, there are some 12 volt panels available at closer to the $1 a watt price and with larger panels going back to 72 cells, 24v PWM systems might be viable. I know using nearly 2Kwh a day running 2 charge controllers, makes multiple cloudy days a bit harder to take.Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same time... I know using nearly 2Kwh a day running 2 charge controllers, makes multiple cloudy days a bit harder to take.
WOW, I'm an idiot, I measured this this morning, and they were drawing about 5 watts, for some reason I thought I had measured 35watts in the past. I apologize for this blunder...Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites, Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects. -
Re: Connect parallel and series the batteries at the same timeWOW, I'm an idiot, I measured this this morning, and they were drawing about 5 watts, for some reason I thought I had measured 35watts in the past. I apologize for this blunder...
News Flash! The only folks who don't make the occasional blunder are those who sit on their arse and do nothing.
And it's those who THINK they're without fault who are quickest to jump on those who may have so blundered.
So to clarify, is it the pair of Classic Lites that consume a total of 5 watts, or do they EACH consume 5 watts?
I've never measured consumption of my Classic, so just wondering.
Thanks.
Wayne -
Re: Connect parallel and series the batteries at the same timeCariboocoot wrote: »A 1000 Watt inverter can supply loads up to a total of 1000 Watts. Watts is a rate, not a quantity. Therefor you do not use 800 Watts in a day, but you may use 800 Watts at a time. Watts over hours is Watt hours: a quantity. Use 800 Watts for half an hour and you've consumed 400 Watt hours.
So an inverter is sized to handle all the loads you might want to run at once: 100 Watts for lights + 50 Watts for computer + 120 Watts for refrigerator (et cetera) totaling 270 Watts (or whatever). This must include start-up surges too: a refrigerator may run at 120 Watts but needs 1kW or possibly more just to start the compressor. If the inverter can not supply that start surge (along with concurrent loads) it will fault and shut down.
When not fully loaded an inverter supplies whatever power is required, as well as consuming its own power needs. So if the inverter uses 20 Watts and the load is 20 Watts the total coming from the batteries is 40 Watts. When supplying its full power, say 2000 Watts, it will still use 20 Watts to run the inverter. Total: 2020 Watts.
Just to make it a bit more complicated there is a conversion loss specific to the inverter. So 100 Watts of AC load may actually take 117 Watts from the battery due to the conversion loss - not including the inverters power needs. Thus 100 Watts ends up pulling 137 Watts from the battery. Exactly how much depends on the particular inverter; some have higher self-consumption, some lower. Some have better conversion efficiency than others.
But wait, there's more! Power Factor can come into play with induction loads like AC motors. This little bit of ugliness causes the current maximum to be drawn at a point other than the Voltage maximum, making the demand on the inverter higher than it would appear to be. The safest way around this is to not load inverters to their maximum rated output (which is really in Volt Amps: Watts with the Power Factor applied).
On the battery output things are not cut-and-dried either, because a battery's real at-the-moment capacity depends on the rate at which current is being drawn. Higher current = lower capacity. The 20 Hour ratings we use to compare sizes and determine charging are based on a steady current draw as Voltage falls off over time. This doesn't happen in the real world; only in testing labs. In the real world the loads are in Watts and as the Voltage drops because the battery is discharging the current rate goes up to meet the Watt demand, effectively reducing the real capacity moment by moment. You can go crazy trying to comprehend this. So we fall back on averages and fudge factors to make it work. One of the factors is the maximum discharge current a battery can take, which sets a limit for how large a load it can handle at a given moment. For flooded cells this is usually about 25% of the 20 hour capacity. Higher discharge rate can cause too much Voltage sag and the inverter may 'see' low Voltage and shut down.
Confused enough?
BTW it is normal for inverters to have cooling fans. Almost all of them do. A few of the smaller ones do not.
Ah... this is really excellent explanation for me to understand about the inverter much better. Thank you for sharing.
So I reckon it's okay(according your explanation regarding inverter) using >1200W inverter for 800Watt/hour load. Even my loads are becoming less and less by switching most of energy saving U Shaped lamp to LED Lamp, for those 26W U shaped lamp, after they broke, I change it to 5W/10W LED lamp and they did have same lumens provided. I'm very happy to be able to reduce my energy usage, although the LED is bit expensive (yes, they live longer).
Oh yes, I'll need to take more care (manage the load) for the fridge and well pump starting current.Roughly, for systems smaller than 400 Watts of solar panels--PWM and "12 volt" solar panels are generally more cost effective.
For systems >800 watts of solar panels--Genarally MPPT contorllers+GT type solar panels (Vmp typically in the 30-40 volt range or so) are more cost effective and easier to wire out systems (Vmp-array higher, smaller gauge wire from array to charge controller+battery shed required).
Also MPPT controllers tend to have more bells and whistles (Internet Webserver, more charging options, data logs, upgradable software, remote battery temperature sensors, integration with other controllers/components, etc.).
Do a paper design of several system configurations/options and see what works best for your needs.
I am not happy with cooling fans either... Draws in dust/bugs/humidity. Fans do fail. On the other hand, makes for cheaper/more compact AC inverter/charge controllers.
Depends on your loads... Generally, smaller AC inverters are fine until you have some "serious" loads--Typically AC Refrigerators and Well pumps. It is not unusual for an AC Induction Motor to draw 5x its average load (120 watt refrigerator draws >600 VA starting). In general, a 1,200-1,500 Watt AC inverter (true sine wave recommended for various reasons--although more costly) is about the minimum that most people will find satisfactory (start/run a modern US Energy Star full size refrigerator).
The inverter has electronics and some sort of transformer on the output. It takes power to just turn the stuff on even of there are no loads (6 watts is typical for smaller inverter--Say 300 to 600 Watts). 10-20-40 Watts is not unusual as you go 1,000-4,000+ Watts.
MSW inverters typically have about 1/2 the "idle" losses vs TSW inverters... But motors (and some other items like transformers and some power supplies) run hotter on MSW inverters--Induction motors can draw as much as 20% more power (waste heat, hotter motors) on MSW (modified square wave) inverters.
Yep--If you run a 300 Watt TSW inverter 24 hours per day an run your load 5 hours per day at 150 Watts (making up numbers) for DC loads:
24 hours * 6 watts Tare losses = 144 WH per day
5 hours * 150 Watts AC load * 1/0.85 inverter eff = 882 WH per day
=============================================
Total = 1,026 Watt*Hours of DC battery bus load
The larger your AC inverter and less power/time you draw power for your loads--The more losses--And the larger solar array+battery bank needed to support those loads.
There are other ways to address the problems too... One is an inverter with "Search Mode"... The inverter turns on ~once per second for 1 cycle of 60 Hz 120 VAC power. Allows the inverter to draw much less power--And if the AC power draw is >~6watts, the inverter turns on full and runs the loads.
This can work well for loads that turn on and off. But no help for things that require AC power 24x7 (Energy Star refrigerators typically have a defrost timer, running networks, computers, etc.).
-Bill
Bill, thank you for the help explaining comparison between the MPPT and PWM, and the inverter.
Hmm......
After reading this.... I think I'll make sure to move to MPPT in the near future.
I will also try to find an inverter with higher capacity that fit my budget.
I'll for sure need to learn much more and consult the system that I intend to build, with expert in Solar Electric Forum rather than just compare it with articles written on internet.
For the inverter, I've always admired TSW rather than MSW since it's much more smooth wave for devices and will ensure those things last longer, although the price much more expensive.
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