(4) 300w solar panels MPPT controller and 24v battery bank from golf cart batteries

[BLOWN93LX]

NO
You are working with a 24V battery ? When you go with voltages more than 2x battery voltage, you start to incur losses in the charge controller voltage conversion
If it was I, I would wire panels 2x2 (2series, 2 parallel strings) into the controller via 1 breaker (for test and maintenance)
1200w @ 26V = about 45a of charging.

I'm running 160V pf PV into my Classic 200 and it's as hot as a firecracker with a 48V battery. But I had no more space in the underground conduit for fatter wire, so I HAD to go higher voltage. Knowing what I do now, I would suffer the loss in the wire, rather than heating the snot out of my controller (higher temps = earlier failures)

<<So, I'd wire 2 in series, and then parallel 2 of the series strings, giving you close to a 66v array @ 18A to run to the charge controller. You can wire 2 strings n parallel without needing fuses or <<breakers. It's nice to have a breaker on the PV and Battery sides of the Charge controller, for ease of shutting it down.
<<Most reliable MPPT controllers will self-limit to operate in a safe region even if overpaneled

Thanks for the info, Mike. I was assuming it was better to run my panels in series, running the open voltage to the max. In an earlier reply, you mentioned configuring the panels to produce 66v. I didn't realize it was best to double the battery bank voltage, which yes, is 24v ....

I can actually save some money buying a lower cost controller if I don't need 160+ volts from wiring the panels in series...

[Mike90250]

OK I have come to my senses. After remembering the road noise from the crap tires I bought for my wife's car that saved me $100, I've decided to pay more up front for this charge controller.

How about this Midnite 200v 79a for $550.

Being able to wire my 4 panels in series @ 160v open circuit will benefit me, eh? This controller should be over kill, but after finding a 10 year old unit sell on ebay for over $200, I assume its a good choice to make.....

NO
You are working with a 24V battery ? When you go with voltages more than 2x battery voltage, you start to incur losses in the charge controller voltage conversion
If it was I, I would wire panels 2x2 (2series, 2 parallel strings) into the controller via 1 breaker (for test and maintenance)
1200w @ 26V = about 45a of charging.

I'm running 160V pf PV into my Classic 200 and it's as hot as a firecracker with a 48V battery. But I had no more space in the underground conduit for fatter wire, so I HAD to go higher voltage. Knowing what I do now, I would suffer the loss in the wire, rather than heating the snot out of my controller (higher temps = earlier failures)

[Dousman]

I am setting up a very similar system, only significant difference being I have 6 panels as opposed to 4. Wondering if you got an answer on whether wiring in series was the best option.

[Mike90250]

breakers & fuses are placed as close as practical to the origin of power. The batteries would be the item to place the breaker/fuse closest to. There are even some fuses designed to bolt onto the battery terminal, and then your cables connect to it.

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

single or dual fuse,

https://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A

[dc/ac]

(I'm not a pro or even very experienced so do take this with a healthy grain of salt)

2 battery banks @ 24 volts made up of (4) 6 volts 220 amp hour golf cart batteries each allows approximately 25 amps per battery bank charging power.

As far as the controller is concerned, that is one battery at 220AH.

How do I determine what gauge wire to use to connect the batteries together?

One that can handle 50 amps at a short distance.

Where should I place a breaker / breakers?

Above my comfort level to reply.

Am I missing anything else, before I get too far into the installation.

In regard to your installation, having the panels flexible without the frame - what kind of racking system? If they are a roof, say a split seem roof, you "might" be able to get away with a lot less infrastructure than a ground mounted system for example.

I'm interested to see how these panels work for you.

[Wy_White_Wolf]

It will match the battery bank.

WWW

[BLOWN93LX]

So (4) 300 watt panels producing 1200 watts divided by 24 volts is 50 amps. 2 battery banks @ 24 volts made up of (4) 6 volts 220 amp hour golf cart batteries each allows approximately 25 amps per battery bank charging power.

How do I determine what gauge wire to use to connect the batteries together?

Where should I place a breaker / breakers?

Am I missing anything else, before I get too far into the installation.

[BLOWN93LX]

OK I have come to my senses. After remembering the road noise from the crap tires I bought for my wife's car that saved me $100, I've decided to pay more up front for this charge controller.

How about this Midnite 200v 79a for $550.

Being able to wire my 4 panels in series @ 160v open circuit will benefit me, eh? This controller should be over kill, but after finding a 10 year old unit sell on ebay for over $200, I assume its a good choice to make.

Just a reminder, here are my panel specs

• STC DC Watts Maximum Power Pmax: 300 W
• Module Efficiency: 18.4%
• Maximum Power Voltage Vmp (V): 33.67V
• Maximum Power Current Imp (A): 8.96A
• Open Circuit Voltage Voc (V): 40.0V
• Short Circuit Current Isc (A): 9.35A
• Maximum system voltage: 600V UL, 1000V IEC
• Maximum reverse current: 20A
• Power Tolerance 0 +3 watts
• Cells per module: 60
• Glass: Low iron tempered with Anti-Reflective Coating
• Dimensions: 65.95 x 39.4 x .29 inches (33mm)
• Weight: 39.7 lbs

Classic 200
The Classic 200 MPPT Charge Controller has Arc Fault, Ground Fault, free web monitoring, a graphics panel and Solar, Hydro and Wind Modes. The Classic 200 has a maximum output current of 79 amps, an operating voltage of 200 volts and works with 12 to 72 volt battery systems. The FREE MidNite Solar Local Application enables you to monitor your Classics over your local network or the Internet. As with the whole Classic Line, the Classic 200 has MidNite’s exclusiveHyperVOC which extends VOC limits when needed.

[SunEagle]

You only need a combiner box if you need to wire you panel in parallel strings to you CC. I have a combiner box that can parallel 5 panels to my PWM CC. If you purchase an MPPT CC that is rated 50 amps or more you do not need a combiner box because you can wire the 4 panels in series to that CC.

[Mike90250]

Generally, a battery system can be "over paneled" a little bit. The MAJOR mfg's (Midnight, Morningstar, Xantrex, Outback) all will fold back current, to keep the controller in a safe range.
In the morning, the sun comes up, and the controller starts a slow charge on the batteries, by 10AM with better sun orientation, the panels could really be pushing power, but with the batteries partially charged by this time, they seldom take the full current the panels could put out. And the panels normally run 80% of spec, because they heat up and "fade" a bit.
The LOAD terminals are located ANYWHERE the mfg wants to put them, you cannot rely on them being the 2 righthand terminals. And AFIK, they are always at battery voltage

[BLOWN93LX]

Usually the output voltage of the CC "load" terminals would be the same as the battery voltage. Also some CC have load terminals may only have very small "loads" and can easily be burned out.

While that tracer CC is ok you really need something that is rated a little more then 40Amps with 1200 watts of panels you will be exceeding the max wattage of 1040w for a 24voltage battery system.

Note. edited my post due to math error pointed out by little harbor.

I think someone mentioned in an earlier post only expecting 80% = 960 watt best case ?

[BLOWN93LX]

Can anyone help me to understand whether there is value in placing a combiner box between the solar panels and the charge controller? Ideally I would place it as close to the panels as possible? Or is it over kill and some simple breakers which are much less expensive will accomplish the same thing?

[SunEagle]

4 in series =160 Voc., or 3?

Yeah. My mistake 4 in series would be 160VDC and exceed most MPPT CC. Sorry about my math mistake. I will make the change in my post.

[littleharbor]

4 in series =160 Voc., or 3?

[SunEagle]

Quick question: On an MPPT controller, if the battery bank is 24v, what will the DC light output be? Will it still be 12 volt? Or will the light output terminals match the battery bank?

Usually the output voltage of the CC "load" terminals would be the same as the battery voltage. Also some CC have load terminals may only have very small "loads" and can easily be burned out.

While that tracer CC is ok you really need something that is rated a little more then 40Amps with 1200 watts of panels you will be exceeding the max wattage of 1040w for a 24voltage battery system.

Note. edited my post due to math error pointed out by little harbor.