Wire size .

Re: Wire size .

You need to know the current supplied/required to calculate wire sizes... And, especially, for solar, you need to know how long the wires will be for each application (for example, solar panels 3 feet from the battery can be sized just on the amount of current to be safely carried. However, if the panels are 100' (200' of wire run) away, you will need to make the wire larger to prevent excessive voltage drop from robbing power or even preventing charging of your batteries).

V=I*R
P=I*V
P=I^2 * R
P=V^2 / R

So, if the system is 12 volts, then:

I = P / V = 70w+80w+85w / 12 volt = 19.58 amps

You can use this Excel spread sheet and enter your current, length, and temperature to get the minimum recommended wire gauge to use:

http://www.wind-sun.com/smf/index.php?topic=1477.0

You would do the same thing with your load... If it is a 500 watt inverter, the maximum current you would expect would be based on the lowest battery voltage before the inverter turns off (by the way, most inverters turn off right at the point they seriously damage your batteries by deep discharging them). Say, in this case it is 10.5 volts (for a 12 VDC inverter) and the inverter is 85% efficient:

I=P/V= (500 watts * 1/0.85) / 10.5 volts = 56 amps

Also, especially with batteries, you need a DC rated circuit breaker or fuse to prevent fires from short circuits. Generally, a fuse or breaker should be set at 125% - 150% of your maximum expected load (to prevent false tripping). Lead Acid storage batteries, even small ones, can supply an amazing amount of current and wiring/devices need to be protected from shorts.

By the way, you should also take the maximum currents calculated above and multiply them by 1.25 to to allow for a margin of safety.

If this is going to be installed in a home/business or other area, you should use the National Electric Code (NEC) or other applicable regulations for your area (NEC in the US overrides anything that the Excel spread sheet or posts on a website may tell you). It is very possible for fires to be caused by improperly wired/designed solar power systems and you want to make sure you are safe and you don't have problems with insurance (in case the worst happens).

-Bill

Re: Wire size .

I am not the charge controller expert here--but the TS family claims to have a 30 meter remote monitor kit, and a 10 meter remote battery temp sensor.

Keeping the TS-xx cool and dry is #1. Keeping it closer to the battery so that you keep the extra wires (remote temp and battery voltage sense leads short) is not a bad idea.

I don't think keeping a 14 volt and an 18 volt panel in parallel is going to hurt anything--just when the voltage gets above 14 volts, the 14 volt panel's contribution to the current will simply drop off as the 18 volt panel raises the voltage...

Depending on the real Vmp an Imp (maximum power) ratings for the panels--and the actual temperature of the panels and battery equalization voltage at your operating temperature (try to keep batteries close to 77F and solar panels coo)--you could do better by placing the two solar panels in series (assuming current ratings are roughly equal) and adding the voltages together to 32 vdc and putting it through a good MPPT controller. You will get maximum power and reach equalization voltage under all conditions (assuming you meet the controller's minimum/maximum parameters).

The bigger issue is that MPPT controllers consume more power than simple PWM type controllers, and usually don't make much sense on systems with much less than ~400 watts of solar panels (extra power needed to run the MPPT function eats up any extra power generated--one of those "details" that separate theory from reality).

And, really what you need to monitor is the state of charge of your battery bank. Measuring the current going in and leaving (plus battery voltage) tells you how the battery is being treated... And you can remote mount the battery monitor in the cabin--and can see how much battery power you have available at anytime (sort of like a battery "fuel quantity" gauge--battery voltage is much less accurate, especially under load/charging, at estimating battery state of charge).

Look at this area (battery meters and shunts) for some ideas. Probably more useful than monitoring the TS-xx meter itself.

-Bill

Re: Wire size .

If I understand the TS-xx product line correctly... They are not MPPT type controllers... Just PWM which cannot efficiently "transform" the voltage from series high voltage connected PV panels into lower voltage battery banks.

Basically, if you put you two 80 watt panels in series, you will only get 40 watts in charge to the battery using a PWM controller. So--you do not want to do this unless you have so much voltage drop that you don't get enough voltage at the battery terminals any other way.

The controller is rated to control 12, 24, 48 volt battery banks--but the optimum panel string voltage a few volts higher than the maximum equalize bank voltage... So a 12 volt bank should be, say 18 volts, and a 48 volt bank would be some 63 volts of solar panels.

I just re-read your post, and while the above is correct--you are probably thinking of rewiring you battery bank to 24 VDC, not just rewiring the solar panels themselves... So:

If you converted your bank to 24 volts, you 18+14 VDC panel is still very close to not making the maximum battery voltage required for equalization... You need to look at the highest temperatures of the panels (and therefore, their lowest voltage on hot days), and you battery bank's equalization requirements at their average temperature. For Trojan 24VDC bank, you will need 31 VDC to equalize at 80F... If the battery bank is warmer, you need to compensate:

[FONT=Verdana, Arial, Helvetica, sans-serif]Correct the charging voltage to compensate for temperatures above and below 80o F. (Add .028 volt per cell for every 10o below 80o F and subtract .028 volt per cell for every 10o above 80o F)[/FONT]

That is very close to the 18+14=32VDC volts of your panels. If those are STC (standard temperature and conditions) Vmp (voltage, maximum power) ratings for your panels--their true voltage will be less as STC ratings significantly over-rate solar panels (STC is way too cool of panel temperature for most people in warm climates). So, if you have the panel model numbers--or otherwise know their actual Vmp voltages--you will have to be very accurate because you are right on the edge of having enough voltage to equalize a 24 VDC bank.

Lastly, you probably don't want to use the DC/DC converters because that just adds more power loss do to the switching converter--unless this is your emergency backup system or you have more than enough power to loose another 20% to converter losses...

Hope I am making sense here and helping you.

-Bill