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Plaguemessiah
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# Posted: 16 Sep 2012 11:23
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Well I have been lingering around this awesome site for about a year now. With the help of these forums I have almost completed my 16 x 24 cabin in Bandera, Tx. I hired an electrician to install my solar system and went out yesterday to use it for the first time. I was greatly disappointed when I ran into a problem and I was hoping someone could help me. So heres the rundown and any feedback would be greatly appreciated. It is a 24 volt system. I have 4 290 watt panels in series each at 8 amps for a total of 32 amps they are run down to a combiner box then to my charge controller and down to my battery bank. The batteries are 6 volt in series to get the 24 volts and 233 amp hours of storage. The batteries are then run into my cotek 1500 watt inverter and then to my GE breaker box. I hope that is enough information to diagnose my problem. I plugged in an 18volt 2.2 amp Ryobi battery charger and a GE 12 amp mini fridge to my outlets and within 10 mins the energy shut off. I went to check everything and found that the power status light on the inverter was blinking red. I turned everything off and then powered it up again and got power however about 5 mins later the same thing occured. I called the solar electrcian and he is telling me that the battery bank is depleted. I feel that is impossible due to the fact that the system sat charging for over a week before I went and put the first load on it. The math alone tells me that a 14.2 amp load would not drain the batteries that quickly. Is the inverter broken? What can I do to diagnose the problem. I would appreciate any help ya'll can provide.
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Dillio187
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# Posted: 16 Sep 2012 17:01
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do you have a battery monitor? Something like the Trimetric 2025 would be highly recommended to monitor state of charge, plus you can verify for sure your batteries are charging.
You should also have a battery hydrometer. This allows you to check the specific gravity of the battery fluid, which also tells you state of charge.
Short of that, I would go over all of your battery, charger, and inverter connections and double check to make sure they are tight
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maine_island
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# Posted: 17 Sep 2012 07:25
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if you have four 290-watt panels in series and each can supply 8 amps at its rated voltage, then you will end up still with 8 amps (but at four times the voltage) charging the battery pack, because of the series connection. in a series connection, amps stay the same and voltage is additive. (on the other hand, in a parallel connection, volts stay the same and amps are additive.)
similarly, if each battery is 233 amp-hours, when connected in series the whole battery pack still has 233 amp-hours capacity.
you say you plugged in a 2.2 amp charger and a 12 amp mini fridge to the outlets of the inverter. i assume the amps you are quoting are NOT the amps they actually draw from the 120V outlet, but rather the equivalent amps they draw from the battery pack at 24 volts. for example, plugging in a 120 volt 60 watt light bulb into the outlet draws 0.5 amps from the outlet, but actually draws 2.5 amps from the 24 volt battery pack (assuming the inverter is 100% efficient.)
if you are drawing 14.2 amps from the battery pack for those two loads, you can never sustain that by charging the battery pack with only 8 amps when the sun is shining, not to mention when it is not shining. such a load will deplete the battery pack even when the sun is shining.
so it seems to me your solar panels are underpowered for the loads you intend to use. however i cannot explain the much shorter times you are quoting.
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241comp
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# Posted: 17 Sep 2012 08:44
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It definitely sounds to me like something is wrong with the setup - checking the batteries with a hydrometer (available from any auto-parts store) will tell you whether the solar panels are charging them properly. I would get a kill-a-watt (~$30) to determine how much electricity the charger and mini fridge are actually using. I would be extremely surprised if it is anything near 12a continuous (1440W) because my full-size refrigerator only consumes about 480W when it is running (which is only 1/3 of the time, equaling 160W average power consumption).
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Dillio187
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# Posted: 17 Sep 2012 08:45
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good catch maine_island, I just assumed the OP was using an MPPT charge controller to convert the higher voltage series current of the panels to 24V for charging. I guess we definitely need more info here.
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MtnDon
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# Posted: 17 Sep 2012 20:51
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As was mentioned, IF the charge controller is an MPPT type then as far that portion goes everything should work. If it is not an MPPT charge controller than there is a lot of waste built into that system. If it is an MPPT type with the panels in series be certain that the Voc, plus the cold weather safety factor of 1.25 x 1.25 is not more than what the controller can handle. In cases like this it is best to specify all the components by make and model number.
EG: If the panels are rated 290 volts and 8 amps is the rated current output that will put the Vmp at around 36 volts. Four in series means a output voltage of about 144. There are a lot of MPPT controllers that are close to their maximum input voltage at that number.
From the info provided it is ambiguous as to whether or not the draw figures (2.2 amp and 12 amp are measured in 120 volts or 24. Big difference there.
If those loads are at 24 volts that is a large amount of power to pull from what is really a small string of batteries.
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Plaguemessiah
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# Posted: 18 Sep 2012 00:48
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I appreciate the feed back from everyone. The charge controller is not the MPPT type. After speaking with the electrician he conneted the panels in parallel to maintain 24volts and the 4 6 volt batteries in series to get to the 24 volts. I hope this information helps to clarify the issue. Again thank you all so much for the feedback. This solar issue is the only think preventing me from moving into my cabin full time.
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Dillio187
Member
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# Posted: 18 Sep 2012 11:22 - Edited by: Dillio187
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here is the problem with that setup:
Your panels are most likely grid-tied panels with a VMP of around 30 volts. In a parallel configuration, they will not properly charge a 24 volt battery bank, especially if the panels are warm, which I bet they are in texas. The voltage on warm panels drops considerably. Can you please verify the specs on the back of your panels and report back here?
If the above is true, you really need to get an MPPT charge controller to properly charge your bank, and setup your panels in a series-parallel configuration. 2 strings of 2 panels, with a VMP of 60 volts. This will reduce line loss, and allow the MPPT charge controller to down-convert to the correct voltage to charge your 24 volt bank. I have a similar setup on my cabin, only my bank is 12V. You can see my setup in the Projects and Photos section.
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MtnDon
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# Posted: 18 Sep 2012 13:02 - Edited by: MtnDon
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Repeat; the best, most precise assistance needs all the info on all the components.
MPPT controllers are marvelous devices when used with series panels (within the limits as noted above). Our PV system still produces power, at reduced rates to be sure, late in the afternoon when the sun is hitting at quite an oblique angle. All because of the MPPT controller and a series module setup.
There are many factors to consider to get the best use out of the equipment on hand. Very important to know all the specs. Solar is not all that difficult, but even those with experience need to know all the specs.
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Plaguemessiah
Member
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# Posted: 18 Sep 2012 14:08
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Astroenergy 290 watt panel specs -
STC rated ouput 290wp
PTC rated output 261.1
rated voltage at STC 35.68 V
rated current at STC 8.15 Amps
Open circuit Voltage 44.90 V
Short circuit current 8.94 A
Module efficency 14.9%
Rated output 202.5 Wp
Rated voltage 32.51 V
Rated current 6.23 A
Open circuit voltage 41.20 V
Short circuit current 6.91 A
Morning Star 60 A
Rated solar load 60 A
System Voltage 12-48 V
Accuracy 12/24 <0.1% + 50m V
Min Voltage to operate 9V
Max Solar Voltage 125 V
Self consumption:
Controller <20mA
Meter 7.5 A
Batteries 6V Flooded lead acid Batteries
Amp hours 232
Cotek ST1500-124
rated power 1500 watts
Surge Power 3000 watts
Wave Form True Sine Wave
Frequency 50/60 selectable
Standard Receptacles Hardwire
No load current draw 0.75 A
Stand by current draw 0.15 A
Dc Voltage 24VDC
Voltage Range 21.0-30.0 VDC
Efficiency 91.0%
Fuse 20Ax5
Circuit breaker 16 Amps
Synchronous AC transfer YES
Transfer switch 25 Amps
Bat. Low alarm 22VDC
Bat. Low Shutdown 21.0VDC
Overload Shut off output voltage
Over voltage 30.6 VDC
Over Temp Shut off output voltage
Output Short Shut off output voltage
Bat Polarity By fuse open
Working Temp 0 +40 degrees C
I hope this is not overload on the specs but this is everything off of every component in my system. If anything else is needed please let me know.
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Dillio187
Member
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# Posted: 18 Sep 2012 14:45 - Edited by: Dillio187
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about what I expected. Your panels are rated at 32V, which doesn't leave much room for error to charge your bank at 29.2 or 29.4 volts, and won't provide enough voltage for a correct equalization charge.
I suspect your bank isn't getting fully charged. I would highly recommend a battery monitor as you can be 99.9% sure of what is going on with your system then. you're more than likely going to need to get an MPPT controller as well.
Do you have another charger for the bank? Something you can hook up to a generator? I would charge that bank up full pronto before you ruin the batteries.
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MtnDon
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# Posted: 18 Sep 2012 22:19
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That charge controller is not a good match. And the panels are not ideal either as Dillo pointed out.
The panels could be re-configured to two pairs in series with the series pairs then connected in parallel. IF you had an MPPT charge controller then there would be little wasted power and there would be high enough voltages available to give a proper charge as well as sufficient voltage to run an equalization cycle as needed.
IF the panels were connected in a series-parallel configuration with the Morningstar controller there would be a danger of exceeding the maximum voltage of the TS-60. To calculate the maximum likely voltage from the panels take the Voc (44.9 volts) If two panels are in series add the Voc (=90.8 volts. The n multiply that by 1.25 and then by 1.25 again. That comes to 140.3 volts, too much as the unit is rated at 125 volts. Those corrections are a NEC safety factor and a cold weather safety factor. (Voltage output climbs in cold weather. Highest voltage frequently occurs first thing in the morning as the sunlight lights up the cold panels. Our system has come to within 9 volts of the calculated maximum several times over the years. If you don't have very cold winter temperatures the safety factor can be reduced. But a high peak voltage can toast a charge controller.
Now the other questions are: (1) how much good sun do you have? Is it sufficient to charge the batteries in a single average day during the worst time of the year; usually winter in the northern hemisphere? And (2) do the batteries have sufficient capacity to operate everything you want to run without depleting the charge below 50%? It would be best for a single day of normal use to not draw the charge down more than 20 to 25% as that would then provide a safety factor of an extra day without sunshine.
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TomChum
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# Posted: 19 Sep 2012 01:39 - Edited by: TomChum
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Quoting: Plaguemessiah I have 4 290 watt panels
I have 2 85watt panels, and it's almost enough. You have 9 times the power that I have. I think I will add another 90W panel before winter.
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Plaguemessiah
Member
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# Posted: 19 Sep 2012 02:09
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The average amount of sun is 5.30 hours and a low in winter 4.65 as we have mild winters in south texas. I am trying to be ultra cautious of my consumption going in so I should be able to keep it at about 50% of battery capacity. I plan on running my larger appliances off of propane. I guess the best option will be to purchase an MPPT charge controller. I want to thank all of you for the feed back. I will post pictures soon of my 16x24 and hope to contribute in the future to these forums. All of you are awesome.
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creeky
Member
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# Posted: 19 Sep 2012 17:04
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I hope you don't mind if I chime in.
1) MPPT is the technology required for off grid. Your system will then easily charge your batteries. I think I'll get a unanimous on that one. yours too I see.
2) with 4 290v panels you should be charging a battery pack with 800 amp hours at 24v minimum. 232 is not enough. don't shoot the messenger. you have the panels, now you need the storage. I'd probably recommend 1200 amp hrs.
3) even tiny fridges are incredible energy hogs. with your new 800 amp hr battery pack you'll be able to use an electric fridge!
4) good luck
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Plaguemessiah
Member
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# Posted: 31 Dec 2012 11:22
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Hello all and thank you for all your help. I upgraded and got 2 more 290 watt panels and 4 more batteries w/ 232 amp hours apiece so a total of eight at 1160 amp hours on a 24v system. I bought a new midnight solar mppt charge controller and a 4000 watt magnum pure sine wave inverter.
It has been running my 42" tv, mini fridge, xbox360,laptop, 3 cfl lights,and my security camera system. I am running an Eccotemp tankless propane water heater, Propane range and a wall mounted propane space heater.
I have moved in full time with the family and now am completely offgrid. What a way to start the New Year!
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Moving Pictures
Member
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# Posted: 1 Jan 2013 19:14
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Sounds to me like your electrician didn't know much about charge controllers - and didn't spec an MPPT controller.
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