Help! Power Draining too Quickly from My Solar Setup

[easydna]

I recently started using a solar system in my home, but my experience hasn´t been great so far.

My initial setup was 200W X 8 panels, a 5,000W 48VDC inverter (Power Star) and four 12V X 100A batteries. This setup worked well initially, until I decided to make some more changes to extend the capacity of my system.

I added seven more panels (200W X 4 and 250W X 3) and four more 12V X 100A batteries. I also changed my controller (to the Flexmax 80 controller to support the new panels). Based on this setup, I have 3,150W solar panel setup and 8 12V X 100A batteries. When fully charged, the battery doesn't last 10 hours at an average usage of 300W.

I have done everything I can to troubleshoot. Initially thinking my battery was at fault, I returned the old batteries and got four new 12V X 205A Trojan batteries, but that didn't make a difference.

The batteries are new, and tests show they are okay. It seems obvious that the rate of discharge is high and abnormal, but nothing seems to be fixing this.

Can you please let me know what I should be troubleshooting?

[Mike90250]

power star inverter stand by losses.
or
improper setup of the charger

[SunEagle]

Unfortunately you have fallen into the trap of believing a solar / battery system can be easily and safely expanded. Both of those assumptions are false and I think you are now seeing the end result.

My assumption is that you have way too many batteries wired in parallel which has resulted in uneven charging and discharging. You may also have exceeded the wattage or dc voltage input to the charge controller by adding 7 (never good to use an odd number) of panels

[Sunking]

Why are you using 12 volt batteries?

Anyway if your batteries are fully charged, and 10 hours later are dead simple means your whole system is poorly designed, and using too much power.

Give you a clue. With 3150 watt sof solar into a 48 volt battery minimum size is 600 AH. You only have 200 AH of the wrong battery type.

[easydna]

power star inverter stand by losses.
or
improper setup of the charger

Thanks for the response. Is the inverter standby loss serious enough to make a setup that should last 36 or more hours last just 10 hours?

Can you please give tips or point to any resource on proper charger setup?

[easydna]

Unfortunately you have fallen into the trap of believing a solar / battery system can be easily and safely expanded. Both of those assumptions are false and I think you are now seeing the end result.

My assumption is that you have way too many batteries wired in parallel which has resulted in uneven charging and discharging. You may also have exceeded the wattage or dc voltage input to the charge controller by adding 7 (never good to use an odd number) of panels

I appreciate your feedback. You make valid points, but I believe I factored this in; please prove me wrong: When expanding my panel setup, I upgraded my controller. I was initially using a 30A PWM controller, but I upgraded to an 80A MPPT controller (Flexmax) before adding the extra panels. The most the controller has ever tracked at a point is around 46A, which is still below its maximum capacity. Perhaps I'm missing something?

When the new panels were added, all the panels were rewired; with the original setup, panels were connected in twos. With the addition of the seven panels, however -- since there are now 15 panels -- the panels were connected in threes. Is this a mistake?

[easydna]

Why are you using 12 volt batteries?

Anyway if your batteries are fully charged, and 10 hours later are dead simple means your whole system is poorly designed, and using too much power.

Thanks for replying, Sunking!

The installers brought the 12 volt batteries.

I also suspect the system is poorly designed, since tests show that the batteries are okay, but I'm clueless as to what is wrong. Is there a way I can figure out exactly what part of my system is causing the issues?

Give you a clue. With 3150 watt sof solar into a 48 volt battery minimum size is 600 AH. You only have 200 AH of the wrong battery type.

Can you please clarify? 4 Trojan batteries of 205 AH each should be 820 AH, no? I'm confused as to how this is 200 AH? Also, why is this the wrong battery type? Please enlighten me.

[SunEagle]

I appreciate your feedback. You make valid points, but I believe I factored this in; please prove me wrong: When expanding my panel setup, I upgraded my controller. I was initially using a 30A PWM controller, but I upgraded to an 80A MPPT controller (Flexmax) before adding the extra panels. The most the controller has ever tracked at a point is around 46A, which is still below its maximum capacity. Perhaps I'm missing something?

When the new panels were added, all the panels were rewired; with the original setup, panels were connected in twos. With the addition of the seven panels, however -- since there are now 15 panels -- the panels were connected in threes. Is this a mistake?

Even though you upgraded your CC to an 80a MPPT type you still are having issues charging those 8 batteries. My guess is that there is some type of unbalance in the charging / discharging due to multiple parallel wiring paths.

The other possibility is the way you might have wired the extras 7 panels or that 12 are 200 watt and 3 are 250. It could be the specification might be different enough not to get the expected output.

The other possibility is that your original 4 batteries were not in good health and now that you added 4 new ones they have lost life due to the old ones. Part of what I was saying about expanding a solar / battery system is that unless the old batteries are only a couple of months old and have rarely been used you can't add new to old. The new just degrade very quickly which reduces the total available output of the system which in turn can be over discharged.

[Sunking]

My initial setup was 200W X 8 panels, a 5,000W 48VDC inverter (Power Star) and four 12V X 100A batteries. This setup worked well initially, until I decided to make some more changes to extend the capacity of my system.

I added seven more panels (200W X 4 and 250W X 3) and four more 12V X 100A batteries. I also changed my controller (to the Flexmax 80 controller to support the new panels). Based on this setup, I have 3,150W solar panel setup and 8 12V X 100A batteries.

First Red Flag is your panel configuration with mixed wattage panels. You have 15 panels and that leaves you with a incompatible configuration option. There is no possible way to work with them. You can only use either the 12-200 watt panels or the 3-250 watt panels. Fist thing I would do is get rid of the 250 watt panels, and configure the 12 - 200 watt panels in 4 x 3, (4 parallel strings with 3 in series). Even better if the controller can handle the voltage is is 3 x 4 (3 parallel strings with 4 in series). That most like will fix most of your problems except too small of a battery.

[NorthRick]

Can you please clarify? 4 Trojan batteries of 205 AH each should be 820 AH, no? I'm confused as to how this is 200 AH? Also, why is this the wrong battery type? Please enlighten me.

If wired in parallel, you have 820 AH at 12v. Wired in series and you have 205 AH at 48v. Your battery bank is too small for the number of panels you have.

[Sunking]

Can you please clarify? 4 Trojan batteries of 205 AH each should be 820 AH, no? I'm confused as to how this is 200 AH? Also, why is this the wrong battery type? Please enlighten me.

Are these 205 AH Trojans 12 volt batteries wired in series for 48 volts?

If you answered YES, you only have 48 volts @ 205 AH. I already know you answered yes.

• Series circuits, Voltage and Power adds, Amps are equal or do not change. You wired your 4-12 volt 205 AH batteries in series to get 48 volts @ 205 AH.
• Parallel circuits, Amps and Power adds, but voltage does not change. To get 820 AH with your 12-volt 205 AH batteries would require 16 of them configured 4 x 4 or 4 parallel string with 4 in series on each string.

For any Flooded Lead Acid battery you want to limit max charge current to C/8 and no les than C/12. On a 205 AH battery that is 205 / 8 = 25 amps maximum and 17 amps minimum. That means the highest power you want to run on your batteries is 25 amps x 50 volts = 1250 watts. Being a Trojan you can get away with C/6 or 1700 watts for 35 amps @ 48 volt battery.

If you use your 12-200 watt panels is a total power of 2400 watts and into a 48 volt battery generates 48 amps of charge current. That tells you the minimum battery size if using Trojan is 300 AH and maximum is 600 AH maximum. To do that cannot be done with 12 volt batteries. You would need to use 6-volt batteries rated at 300 to 600 AH each battery with 8 in series. Something like a Trojan L-16-RE-B a 6 volt 370 AH battery x 8 of them.

I know that hurts, but that is your problems.

If you were my client here is what I would tell you:

"Loose the 250 watt panels, configure your 12-200 watt panels in 3 x 4, or 4 x 3, return your batteries and use 8 6-volt 370 to 600 AH batteries wired in series for 48 volts. Otherwise find someone else to do the work for you because I want no part or my name associated with what you have now. Sorry but that is the bottom line. Take it or leave it".

Edit Note:

Invest $10 in a Temperature Compensated Battery Hydrometer and learn how to use it. Doing so will save you thousands of dollars in battery cost.

Finally Trojan RE line is about as good as you can get. They are solid 5 year batteries with proper care and using a hydrometer. An decent alternative is US Battery US RE L16 XC a 6 volt 400 AH battery would make a perfect fit at 2400 watt panel.

FWIW IMO the Trojan Industrial Line is the best Renewable Energy battery money can buy. Not only my opinion, but the Industry as a whole. A solid 7 to 10 year battery with proper care, Can easily handle 3000 cycles at 50% DO. One of the very few batteries with a 8 year warranty

[Sunking]

OK now that we got your attention. let's get you a short term solution until you figure out a long term solution. Right now your batteries are holding you back and limit what you can do right now. You have a 48 volt 205 AH battery. Realistically at best can only give you 2.5 Kwh per day of usable power. So let's get you going and work with what you have already.

Take 6 of your 200 watt panels and configure them 2 x 3. That is 2 parallel strings of 3 panels in series. That will give you roughly a perfect match of panel power and easily supply you with 2.5 to 3 Kwh of usable battery power a day, or that 300 watt load for 10 hours.

Going forward you are going to have to get larger batteries, much larger batteries if you want to use all your panels. That means getting rid of the batteries you have now and replacing them. You can even use your 750 watt panels, but will require two charge controllers. So here are two options going forward,

Use your 12-200 watt panels with a minimum 50 Amp MPPT charge controller and a 48 volt battery no less than 400 AH and no larger than 600 AH. If you want, but I do not recommend it, you can buy 4 more of the 205 AH Trojans NOW and put them in parallel with the ones you have now. But you can make that work, but do not expect more than 2 years out of them.

If you want to use the 3-250 watt panels, you will need a second MPPT controller of at least 15 amps. Wire all three panels in series. So that 750 with your 2400 watt panels is 3150 watts. The minimum battery size is 500 AH and maximum is 750 AH.

[easydna]

First Red Flag is your panel configuration with mixed wattage panels. You have 15 panels and that leaves you with a incompatible configuration option. There is no possible way to work with them. You can only use either the 12-200 watt panels or the 3-250 watt panels. Fist thing I would do is get rid of the 250 watt panels, and configure the 12 - 200 watt panels in 4 x 3, (4 parallel strings with 3 in series). Even better if the controller can handle the voltage is is 3 x 4 (3 parallel strings with 4 in series). That most like will fix most of your problems except too small of a battery.

That's interesting; does the panel configuration (mixed wattage and all) impact the battery in anyway? Thanks so much for the suggestion re panel configuration. I'll definitely be giving that a try.

[easydna]

Even though you upgraded your CC to an 80a MPPT type you still are having issues charging those 8 batteries. My guess is that there is some type of unbalance in the charging / discharging due to multiple parallel wiring paths.

The other possibility is the way you might have wired the extras 7 panels or that 12 are 200 watt and 3 are 250. It could be the specification might be different enough not to get the expected output.

The other possibility is that your original 4 batteries were not in good health and now that you added 4 new ones they have lost life due to the old ones. Part of what I was saying about expanding a solar / battery system is that unless the old batteries are only a couple of months old and have rarely been used you can't add new to old. The new just degrade very quickly which reduces the total available output of the system which in turn can be over discharged.

Thanks for clarifying this. So, basically, the issue with my not getting the full battery capacity is that the batteries are not charging fully? I'm assuming the controller is not automatically regulating this, too?

I'll definitely be taking a look at the panel configuration. I had no idea that it could be an issue, so I'll be looking into this.

Regarding the battery, I discarded all the initial 8 batteries. Now, I use 4 completely new Trojan batteries; I got all 4 batteries at the same time.

[easydna]

If wired in parallel, you have 820 AH at 12v. Wired in series and you have 205 AH at 48v. Your battery bank is too small for the number of panels you have.

Thanks for clarifying that. I'm assuming that 820 AH at 12 v and 205 AH at 48v basically produce the same wattage? I mean, all things being equal, both setup should output an equal amount of power, right?

Regarding the battery bank, you mean 4 205AH batteries are too small for 3150W panel setup? Could this in any way lead to the power issues?