Needing advice

the_rog

First post, so please don't throw rotten tomatoes at me.

I have 135W worth of panels at my house charging a pair of 115AH marine batteries. The controller and panels came from horrible freight. The panels seem to be ok, but the controller is probably questionable at best. I've ordered a TriStar TS-45 controller to accommodate the additional wattage. I'm not trying to power the entire house. I'm not that naive. All I've done so far is to power a couple lights, alarm clocks, and most importantly my ham radio equipment. Powering the radio equipment was the only real goal, actually. I wanted to be able to operate in spite of a power grid failure. Everything seemed to be ok this summer. But with the sun's path being lower in the sky over the last couple of weeks, I'm not getting enough voltage to fully charge the batteries. I have the batteries periodically on an AC charger to top them off. I'm a marginal carpenter and an even worse welder. Is there a relatively simple way to rig up a tilt mechanism so that I can adjust the angle of the panels to get as much sun as possible?

One idea I had was to use C-channel along the top and bottom edges of the panels, and use all-thread to hold it all together to form one big panel. I envisioned the top C-channel being a couple inches longer than necessary on both sides to act as a pivot. Am I reinventing the wheel, or there something simpler I could do?

TIA

BB.

Re: Needing advice

TIA,

Which TS 45 controller are you think about--The MPPT or PWM?

Starting backwards--The Marine batteries may or may not give you good service. Next set, you might look at some true deep cycle storage batteries instead.

115 AH * 12 volts * 2 batteries? for 230 AH at 12 volts of storage capacity... Normally, we recommend around 5-13% rate of charge (20 Hour rate) as a good range for charging your battery bank (just rough rules of thumb):

• 230 AH * 0.05 = 11.5 Amps minimum
• 230 AH * 0.13 = 35.5 Amps minimum

Or, assuming your solar charge controller and panels are around 0.77 efficient (again, just numbers to start the conversation):

• 11.5 amps * 14.4 volts * 1/0.77 = 215 watts minimum of solar panels
• 35.5 amps * 14.4 volts * 1/0.77 = 645 watts maximum of solar panels

Lets guess that you are around north west Arkansas and get an average of 4-5.5 hours of sun per day (full, noon time equivalent with the array tilted to your latitude).

And that you want to use an AC inverter for 120 VAC power. The other all, end to end efficiency for an off-grid battery based 120 VAC solar PV system is around 0.52:

• 215 Watts of panels * 5 hours of sun per day * 0.52 derating =559 WH per day
• 645 Watts of panels * 5 hours of sun per day * 0.52 derating =1,677 WH per day

Anyway--Depending on what solar panels you have, and how many/.what mfg/model you are going to get--It may be difficult to mix your "old" and "new" panels together on a single charge controller (Vmp and Imp differences).

Of course, there are other losses--Inverters if operated 24 hours per day can take between 6-30 watts just because they are turned on.

For a 12 volt system, I would suggest you look at the Morning Star 300 watt 12 volt TSW inverter. It has "search mode" and does not draw a lot of power in standby (and it has a DC inhibit switch too)--A very nice unit.

I will stop here--You probably have some questions and corrections on my assumptions/guesses.

-Bill

Cariboocoot

Re: Needing advice

I don't have any tomatoes; the plants all froze and died. Including the killing frost July 1!

Problem #1: 135 Watts of panel isn't going to recharge 230 Amp hours of battery, no matter how well aimed. Rough calculations:

135 @ 80% efficiency = 108 / 14.2 Volts charging (assuming a "12 Volt" system) = 7.6 Amps. At most that would handle 152 Amp hours and it would really be more suitable for 1/2 that. This is a chronic "under-mixing" problem that shortens battery life. If you've been doing this for very long, they've probably already lost a significant amount of real capacity.

As for how much improvement you can expect from seasonal adjustment, that would depend on how close to the Equator you are. The further North, the more you gain. Check out the info at Macslab:
http://www.macslab.com/optsolar.html

As for how to make your mounts adjustable ... Without knowing what you've got now it's hard to say.

Basically you're "under paneled".

niel

Re: Needing advice

in addition to aiming better at the sun you should invest in the mppt model. the low vmp from those pvs may be part of your problem and to series/parallel the pvs may allow you to be functional with enough voltage while helping to overcome wire resistance losses. you may want to check into the wire resistance aspect by downloading the voltage drop calculator in the upper section of the forum under the FAQ's, Links, & Information Sources section.

the_rog

Re: Needing advice

I thought I was doing myself a favor adding the second battery. Apparently not. As I understand it, I'm better off with one battery until I can increase the number of panels? The TS-45 model on order is the PWM version. The batteries are marked both marine and deep cycle, type 31M if that means anything. I picked them up at the local Batteries Plus. You're correct, I'm in northwest Arkansas.

TIA simply means thanks in advance.

Charles

BB.

Re: Needing advice

Sorry about the TIA Charles--I took my guess. ;)

Much of our work here is helping people to balance their solar panels against battery capacity against loads... It is a big juggling act.

So, let us know what your expectations/requirements are... And what is fixed (battery size, money spent on solar panels, loads, etc.).

In general, everyone pretty much underestimates their loads and over estimates how much power an off-grid solar system can supply.

-Bill