how many panels to a 40 amp mppt controller

[Leehamrick]

Hi,
I have 4 of these panels and I would like to know how many I can use with a Tracer 40 amp mppt controller?
They will be wired in Parallel and the batteries are also wired in parallel. 12 volts

[inetdog]

Hi,
I have 4 of these panels and I would like to know how many I can use with a Tracer 40 amp mppt controller?
They will be wired in Parallel and the batteries are also wired in parallel. 12 volts

245W times four is about 980 watts.
980W divided by 12 is 81A. That is more than 40A. So two panels max. Most PWM CCs do not allow you to have too high an input power from the panel array. Most MPPT CCs can simply ignore the extra power, but it will do you no good.

You would be better off with a 24V battery system, where you could use all four panels with the single 40A CC.

Putting multiple 12V batteries in parallel to get the capacity you need is also a bad idea. Increase the system voltage first, then go to lower voltage batteries (2, 4, 6 or 8V) to make up one string at the right capacity.

[Leehamrick]

245W times four is about 980 watts.
980W divided by 12 is 81A. That is more than 40A. So two panels max. Most PWM CCs do not allow you to have too high an input power from the panel array. Most MPPT CCs can simply ignore the extra power, but it will do you no good.

You would be better off with a 24V battery system, where you could use all four panels with the single 40A CC.

Putting multiple 12V batteries in parallel to get the capacity you need is also a bad idea. Increase the system voltage first, then go to lower voltage batteries (2, 4, 6 or 8V) to make up one string at the right capacity.

OK ,,,,If I set the batteries as a 24 volt system I could use a 4 panels on one 40 amp controller?
would it be ok to have the panels wired in parallel? Or will the panels need to be wired in series
as well?

[Sunking]

Answer your own question. 40 amp MPPT has a limit of

500 watts at 12 volt
1000 watts @ 24 volt
2000 watts @ 48 volt

[Silver_Is_Money]

Answer your own question. 40 amp MPPT has a limit of

500 watts at 12 volt
1000 watts @ 24 volt
2000 watts @ 48 volt

From brand to brand of charge controller, is there any amount (even if only a small degree) of wiggle room in the above?

[inetdog]

From brand to brand of charge controller, is there any amount (even if only a small degree) of wiggle room in the above?

Most MPPT controllers allow a panel wattage up to 150% of that corresponding to the rated output of the CC. Others have no limit at all.
A PWM CC will usually explicitly limit the input power (in this case the Imp and Isc) to not more than 10% above the CC output current rating.
Even when it is allowed, the higher panel wattage will usually not produce any higher output from the CC.

[Leehamrick]

OK then if my batteries are set up as series to 24 volts then the panels should be OK wired in parallel.

I have a 12 volt inverter and a few 12 accessories. How would I go about hook them up?
If I hooked the inverter to one of the batteries would I be pulling power from all the batteries or just one?

[inetdog]

I have a 12 volt inverter and a few 12 accessories. How would I go about hook them up?
If I hooked the inverter to one of the batteries would I be pulling power from all the batteries or just one?

You can't, at least not with more equipment. If you attach to one battery the string will be unbalanced.
There are special converters that attach to both batteries in a 24V string and produce one 12V output, but they might be more expensive than getting a 24V inverter.

[Sunking]

You can only use 2 panels if you insist on 12 volts. For your panel wattage really screams 24 and even 48 volts.

[Mike90250]

OK then if my batteries are set up as series to 24 volts then the panels should be OK wired in parallel.

I have a 12 volt inverter and a few 12 accessories. How would I go about hook them up?
If I hooked the inverter to one of the batteries would I be pulling power from all the batteries or just one?

Uh oh.

You can either have a 12V system (over 80 amps) or a 24V system (close to 40 amps) But you can't mix voltages in a system- it's either ALL 12V gear, or ALL 24V gear.

More than 2 panels in parallel, you need fuses/combiner box for each panel

You could get around that with a combination of 2 panels in series, and then parallel the 2 series strings. Gives you a 80V array at 17A,

[inetdog]

Without making any recommendation whatsoever, here is one example of the kind of product needed to drive 12V loads from a 24V battery string:

http://www.vanner.com/manuals/80-80CAN.pdf

The limited current will necessarily limit your inverter output compared to one of the correct voltage for the battery string.

[Leehamrick]

OK thanks guys for all the information and input I got plenty to digest now

[almac]

Uh oh.

You can either have a 12V system (over 80 amps) or a 24V system (close to 40 amps) But you can't mix voltages in a system- it's either ALL 12V gear, or ALL 24V gear.

More than 2 panels in parallel, you need fuses/combiner box for each panel

You could get around that with a combination of 2 panels in series, and then parallel the 2 series strings. Gives you a 80V array at 17A,

i have 3 panels in parallel with no fuses or combiner box? whats that anyway. i just have 4 x y cables to do the 3 panels in parallel

i use 12v and 24v gear. have 12v dc chargers, 12 inverter, 24v inverters, 24v solar setup. when i need to charge off the gen i switch the cables around from series to parallel, if its raining for a couple of days leave it in parallel and use the 12 inverter. use 100amp alligator clips on everything for easy reconfiguration

[Mike90250]

Well, if you enjoy rewiring the system, and the losses and risks from using gator clips, you can continue as is, and just make a good home video for your heirs, for when it all goes up in smoke.

Combiner boxes are designed to securely hold fuses or breakers, and contain the wire splices, to prevent good panels from starting a fire if a panel goes bad.

Harvesting 328 watts in a 12v configuration gives less power than harvesting the same 328 watts in a 24V configuration, because of copper losses, internal contact resistance in the connectors, and the mismatch of your panel voltage to battery voltage when using the 12V PWM controller

MPPT controller gives you Watts In = Watts Out (with just a few % of losses internally)

PWM controller gives you a lot more losses (Sunking has the math nailed down)

Your panels are 31v @ 8 amps (roughly) for about 248 watts BUT your BATTERY charges at about 14V, at the same 8 amps,
so you only get 112 watts into the battery . That's HALF your panel wattage just gone and wasted.

[almac]

Your panels are 31v @ 8 amps (roughly) for about 248 watts BUT your BATTERY charges at about 14V, at the same 8 amps,
so you only get 112 watts into the battery . That's HALF your panel wattage just gone and wasted.

thats Leehamrick... not me