# voltage

Solar Expert Posts: 125 ✭✭✭✭✭
Im going to start building some panels and store it in 12vdc deep cycle batteries. I have been reading much about the charging part. could I use 16 volts instead of the norm 18 volts and still charge batteries?I know if you have to run a long distance you need voltage,I also know about hooking cells up in series and par. I was just wondering about making the panel with 16vdc instead of 18.tks.
John

• Banned Posts: 17,615 ✭✭
Re: voltage

"12 Volt" batteries actually charge at 14.2-14.4. If equalization is in the plans, then the target is 15 Volts.

As far as the panels are concerned, it's the Vmp that must be above the charge Voltage in order for it to work. And system losses have to be accounted for. Normally a "12 Volt" panel has a Vmp of 17.5 or so. If your panels can manage 16 Vmp, they should work on a 12 Volt system.
• Solar Expert Posts: 1,280 ✭✭✭
Re: voltage

You need to take the cell's -2 mV/deg C temp coefficient into account. It's about -0.34% per degC.

When in summer sun, the cells can get pretty hot, like 50-60 degs C is not uncommon. That takes a 36 cell stack down from about 18v to 15.7 vdc. Then you have wire and controller voltage drop from that number.
• Solar Expert Posts: 125 ✭✭✭✭✭
voltage of panel

confused a little on charging a 12vdc deep cycle battery. When their in a car the alt, will charge it up to 15vdc. isn't 14 volt norm. Many panels are made with 36/72 cells,and 18vdc. I was thinking or making panels with 32 cells each.that would be 16vdc.That should charge the battery right? I want to make exp. 4 panels, each with 32cells, take the first 2 and put them in series and the the last 2 in parallel. Then connect the par. to the 2 in series.that would give me 32vdc x 7.6amp .Each cell puts out 3.6 amp's.----But if 16 volts would work,I would then like to put them 3 in parallel.
I know if you have to run the wire a long distance then you need voltage.
Any input would be nice. reason for small panels is that I have alot of glass that size.
tks
John
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage of panel

Sorry for the double question, I found my other post about the 16vdc. So it looks like I'll have or should bring it up to 18vdc to make everything happy.[loss of voltage from components]
Re: voltage

Its OK, I have moved all the voltage posts into your first thread...

There are two types of charge controllers... The "simple" and "inexpensive" type is a PWM--Basically just a computer controlled On/Off switch. Need to charge the battery, switch is on. Need less current, flip switch on and off many times a second (PWM=Pulse Width Modulation)... More ON than OFF, more current. More OFF than ON, less current.

The other is MPPT type (Maximum Power Point Tracking)... Basically a digital converter that can take high voltage/low current and step it down to low voltage/high current used by the battery bank (sort of like the DC version of an AC step down transformer).

MPPT charge controllers are typically used on larger systems (more than ~400 watts) and systems that need to have the panels some distance from the array to the battery shack/charge controller... You can send the current at ~100 volts and the charge controller will step it down to 48/24/12 VDC. So you can send the energy farther distance/on smaller (cheaper) wiring.

You could choose to put your 3x panels in series and run on an MPPT charge controller... Or install your 3x panels in parallel and run them on either a PWM or MPPT charge controller.

For small systems (typically under 200 watts), usually PWM controllers are used (cheap and efficient). MPPT is only used when their special features are needed (or, perhaps, the panels are installed in conditions that go way below freezing weather).

Car alternators do typically charge between 13.8 to 14.2 volts (at 77F). But they are not "great" for charging deep cycle batteries (takes a long time to charge, standard alternators overheat and reduce output after 5-15 minutes, do not support equalization of battery, etc.). They are intended to charge batteries that are drawn down to 80% state of charge (20% discharge) and quickly recharge that amount. A car battery deep cycled will generally not last very long.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,341 ✭✭✭
Re: voltage

Speaking of alternators...

The other day, the alternator on my camper van was squealing and the belt looked okay and tight enough, so I thought it might be a bearing in the alternator so I broke out the wrenches and pulled it.

When I checked on a replacement, I found that the '76 E-250 van (mine) specs a 40a alt normally, and a 60a if it has a/c (mine does). When I pulled mine - lo and behold - it's a 100a unit.

Checking further, I found that the E-350 specs a 60a normally, and a 100a with a/c.

As near I can figure, when they converted this Club Wagon window van into a motorhome (professional conversion) they swapped in an E-350 alternator and the associated bit of wiring harness (has a plug instead of the loop and post connection of the E-250).

Neat.

Turned out to be the belt after all.
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

I was reading about the mppn charge controllers and found this one http://www.ecodirect.com/Blue-Sky-50L-Front-Display-p/blue-sky-50l-front-display.htm.
Anyone ever use it? For the first one to try it dosen't cost too much. I have two peices of glass and it looks like I could fit 110 cells 3x6 on it.11 cells vertical and 10 horizontal. Most say 36 cells in series. So 3 sets of 36 tied in parallel .Now what is the best for the 20 other cells? The 3x6 cells put out 3.8 amps and 1.8 watts. Could I take like 4 grops of 5 cells and use those to make more amps?Each group would be about 15 amps. and wire them in parallel.????? Or will the amps be automatically be taken from the cells.
tks
Johnny
Im always thinking that a panel with only 3.8 amps is not much power at all.Seeing that each cell can produce 3.8 amps. with only 5 cells you can get 15 amps
I know ,ohms law.lol
Re: voltage
conntaxman wrote: »
I was reading about the mppn charge controllers and found this one http://www.ecodirect.com/Blue-Sky-50L-Front-Display-p/blue-sky-50l-front-display.htm.
Anyone ever use it? For the first one to try it doesn't cost too much.
Which model do you think you are looking at? What you have linked to is a \$107 remote display--not a complete solar charge controller (which is around another \$400 for the charge controller--If I understand what you are asking about).
I have two pieces of glass and it looks like I could fit 110 cells 3x6 on it.11 cells vertical and 10 horizontal. Most say 36 cells in series. So 3 sets of 36 tied in parallel .Now what is the best for the 20 other cells? The 3x6 cells put out 3.8 amps and 1.8 watts. Could I take like 4 groups of 5 cells and use those to make more amps?Each group would be about 15 amps. and wire them in parallel.????? Or will the amps be automatically be taken from the cells.
tks
Johnny
Im always thinking that a panel with only 3.8 amps is not much power at all.Seeing that each cell can produce 3.8 amps. with only 5 cells you can get 15 amps
I know ,ohms law.lol
Actually, we are looking at the equation for power:
• Power = Volts * Amps
And even though each cell is 3.8 amps, they are only 0.5 volts each... It takes a lot of solar cells and copper to wire all of them into series so you can get ~18 volts out of ~36 cells at X.X amps.

Not an insignificant project.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

Hi BB. I just went to the link and it says that it "includes " the display." well anyway I was asking about the extra ,i think 20 cells that I could fit on the glass. I will be putting 1 string of 3 sets of 36 solar cells in par. to get the 18vdc with 10.8amp. Now i was trying to figure out the best and most efficent way to use the extra 20 cells that I could fit on the glass.I think more amp's would be better but don't know.I know volts x amps =wattage.
tks all for the input.
Johnny
• Solar Expert Posts: 175 ✭✭✭✭✭
Re: voltage
confused a little on charging a 12vdc deep cycle battery.

Everyone talks about voltage but what charges the battery is current. It takes voltage to push current through a battery's resistance.

The resistance of a battery changes as it charges.

Your charging source has to have enough voltage to get a reasonable current through the battery to be effective. Too high a voltage means a current that will cause heating and possibly damage the battery. Too low a voltage means it will take a longer time to recharge the battery. Those considerations are where voltages for the stages of charging come from.

When the battery is discharged, it is easy to get current through it and you don't need much of a driving voltage. The tricky part is getting the full and complete charge you need for best battery life. That takes time and sufficient voltage to squeeze current into a nearly full battery.
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

Hi Bryanl the solar controller that is an MPPN and I think that takes care of getting the right voltage and amp's to the batteries. Im just now wondering how or what is the best way to use the room for the 20 extra cells that I can use in the panel.I was thinking of running the 36 cells that will be in seires and conect that in parel. to the extra 4 cells to get the extra 3.8 amps. with the 36 cells i'll have 4 rows of 9. this would make it 4 rows of 10 cells.
tks
Johnny
bryanl wrote: »
Everyone talks about voltage but what charges the battery is current. It takes voltage to push current through a battery's resistance.

The resistance of a battery changes as it charges.

Your charging source has to have enough voltage to get a reasonable current through the battery to be effective. Too high a voltage means a current that will cause heating and possibly damage the battery. Too low a voltage means it will take a longer time to recharge the battery. Those considerations are where voltages for the stages of charging come from.

When the battery is discharged, it is easy to get current through it and you don't need much of a driving voltage. The tricky part is getting the full and complete charge you need for best battery life. That takes time and sufficient voltage to squeeze current into a nearly full battery.
Re: voltage

CTM,

I am not sure what a MPPN controller is--Probably what we usually call a MPPT charge controller (Maximum Power Point Tracking).

A MPPT type charge controller is (usually) a digitally controlled Buck Mode down converter.

The solar panel input the the MPPT charge controller is usually Vbatt-charging+2volts minimum input voltage...

So, for a 12 volt battery which is charged around 14.5 volts would mean that the Vmp-minimum of your solar array should be around 16.5 volts minimum.

There are other issues... Equalizing a flooded cell storage batteries is around 15.0-15.5 volts, and Vmp falls as the panels get hot... In summer, it is not unusual for a Vmp-hot to be 0.80xVmp-stc... So, having a Vmp>~17.0 volts is not a bad idea.

For MPPT controllers, they can efficiently down convert (~95% efficiency) from "high voltage/low current" of the Vmp-array to "low voltage/high current" for the battery bank or Vbatt-charging.

Now--there is a wide variety of MPPT charge controllers, some with Vpanel-max of 150 VDC, and others down to the ~30 volt range...

So--In general, for your case, you should try for Vmp as high as practical--given the exact brand/model of charge controller you are thinking of using.

For some controllers, the optimum Vmp may be roughly Vmp-array~2xVbatt-charging... But, for most controllers, it is not a huge efficiency hit/improvement either way.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

This question is about a suntracker diagram.I thought i knew all/most of the symboles for schematics,but i guess not.Could someone tell me what ,it looks like a coil next to the " in4004 drive west" thats a diode, but next to it on the right hand side.could be a relay,but all i see would be 2 contacts.Oh also i just looked, i see that it is feed with 12vdc and i do see the Ground symboles at the bottom, but what are the 9V at the top on the Left hand side mean?? were do they connect?Here is the link of both.
blow up picture
tks
John
Look very easy to build and not too many parts.Also maybe someone else could use this.
• Solar Expert Posts: 1,341 ✭✭✭
Re: voltage

That link is for the display only - the charger itself is a different link. Also, it's a 24v/48v charger, not a 12v charger.

A low-priced MPPT charge controller that can do 12v is here:

http://store.solar-electric.com/mosumpsochco.html
Re: voltage

Those are just global symbols on the schematic. All GND connect together and all +9v connect together, etc.

Of there was a connector page, they would terminate at the connector.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

BB. am i correct with this, the 9v connections that I was talking about in this link
That is what the Supply voltage is for the cir. and on the right hand side the 12 volt is feeding the motor through the relays also I see the coils for the relays. About 20 years ago i think that the drew the relay different. I should of seen that.about the 9 volt part.
I looked up the 2 symb. that are at the top Left were it says 9v. they look like a V and the other that looks like it is going into it looks like a V with a line kinda like -> but it is facing up. Now are those a PLUG? -> >- But why would he put a plug their.
TKS
John
Re: voltage

You are correct, that is a 7809 3-Terminal Regulator... XX volts in, 9 volts out.

Everywhere you see a +9V label--you can assume that they are all connected together. It is a short hand for schematic capture packages (common connections like +5V, GND, etc. just named labels instead of schematic drawn connections).

The -->>-- are just indicating Plugged or Off-Board components (limit switches, actuator motors, etc.).

Note that where wires connect, there is a filled in bubble. Where they just cross (no connection), there is no bubble.

If you are familiar with industry standards for relay/actuator symbols--they will not be seen on PCB schematics... You will find that electrical engineers make up their own symbol for devices that represent the part / function in their mind (most schematic capture programs do not come with very many pre-loaded components--the engineers have to draw their own).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

BB. hello again.and tks for the reply.
I just want to make sure what I am thinking of.So when I build this i won't see too much smoke.lol Up in the left top were we were talking about. That means from the 9+ that i could connect a wire right to the LED's and then right to VR1 pot. """or I could put in 3 PLUG's /SWITCH at these connections --> <--- or it be just a stright line and that would do away with the plugs or switches. Hope im thinking right.
tks again
Johnny
Re: voltage

Yes and, possibly, no...

Yes--You have correctly described what you are seeing.

Possibly no because of a typical design mistake... I have not looked up what components they are using but looking at PC2, there is a 1kohm ballast resistor.

PC1 is connected to a 10kohm pot... It is adjustable--so one would expect the resistance to be somewhere between 0 and 10 kohms... The problem is Zero Ohms... You would have to check the specifications for PC1 to see if it can take a 9volt bias without burning up (I have no idea without doing the research myself--I have to go in a bit--so no time right now).

Normally, a person would place (for example) a 500 ohm resistor in series with the PC1 so that its resistance would now adjust between 500 ohms and 10.5 kOhms.

Just one of things to watch out for.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

BB. you sure know alot about cir. I can only build from them,I cant make one because I dont know how to figure out what everything dose ,I mean, I know what things do, res,cap,diodes, relays,etc. But how to put them all together. I looked at the other link [parts list] and all it says is a "10k pot"But your right about the voltage when its turned down to 0. ha ha ha I know what I'll buy 2 of them so when one turns into smoke ,i have the 2nd one two replace it. ha ha ha .
Johnny
sure are a nice bunch of guys on this board.
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

BB.
I was just reading alot of post in the different sections, and ha your smart.congraulations. I will be asking another question about inverters, 120/220 pertaining to main panels. To think of it ,for a gird tie in, you would have to run a 220 inverter, How else would you connect . I dont think that you can just tie in on ONE SIDE of the panel. nooooo.
Dam this is a good site. And alot of nice people.
Re: voltage

You can actually drive 120 volt grid tied inverter on a120/240 vac split phase circuit as found in North America just fine.

Normally people are looking for more than 1,500 watts of solar panels. And the lesser current because of the higher voltage. But if you balance pairs of inverters across the HOT/NEUTRAL/HOT leads.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

would anyone know about how many amp's the 2mm tabbing wire is rated for /VS regular round wire???
Johnny
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

This wire size is for the tabbing. Would this copper wire size [ 24 ] be good enought to use when tabbing 36 cells together in series?It says 3.5 amp
.Thanks John
.
AWG gauge / Dia.inch/ Max .amp for chassis wiring / Max.amp for power trans

24
0.0201
3.5
0.577
• Banned Posts: 17,615 ✭✭
Re: voltage
conntaxman wrote: »
would anyone know about how many amp's the 2mm tabbing wire is rated for /VS regular round wire???
Johnny

"Tabbing"? As in "making your own solar panels"?
Oooh I see a red flag! In as much as your original post has to do with grid-tie inverters. Guess what? You can not use homemade solar panels on a legal grid-tie install. And no one here will advise you to do otherwise.
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

cari.... your JUMPING to conclutions. I'm asking different questions. ok If you seen my last question, could you answer it. I asked if #24 wire could be used to tab 36 solar cells together. it will carry 3.5 amps.
and another thing , I was going to run these panels to batteries and then run to SEPERATE plugs in the house off an inverter.
If I were going to tie to the grid, I would have a different meter installed, I called about that all ready,
Johnny
• Solar Expert Posts: 8,569 ✭✭✭✭✭
Re: voltage

Nearly all sources will say that #24 wire is too small for 3.5 A.

You might get a way with using a 1" piece here and there, but for any run, its too small
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

• Solar Expert Posts: 125 ✭✭✭✭✭
Re: voltage

mike... what do you mean quote"You might get a way with using a 1" piece here and there," 1" your mean Wide? the buss wire on the cell is Only 2mm wide.
Re: voltage

Part of the current limit of a wire is how much cooling / heat transfer there is... If you have short pieces attached to heat sinks (solder to solar cells) and covered (and making contact) with glass--As well as the surface area of a flat wire is much larger than a round conductor. You may get away with less copper cross section for equal current capability. Of course, the operating temperature of a solar panel in full sun on a hot day is rated around 85C... So there is less margin to dissipate the heat without causing local damange.

With round wire/cable, it is covered with plastic insulation and may be in conduit--the ability of the heat to "leave" the wire is drastically reduced. So, the actual current rating (and safe current capabilities) will be less when compared with NEC tables.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 8,569 ✭✭✭✭✭
Re: voltage
conntaxman wrote: »
mike... what do you mean quote"You might get a way with using a 1" piece here and there," 1" your mean Wide? the buss wire on the cell is Only 2mm wide.

I mean a 1" long piece of #24 insulated wire, used as a jumper between something. A long wire would heat up, and loose voltage for more than an inch or so, at 3.5A.
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,