Help! Power Draining too Quickly from My Solar Setup

[easydna]

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.

First, I'd like to say that I appreciate your depth of attention to answering my question... including telling me specifically what to do. Thank you!

I'm a bit confused; so 12v at 820A is more efficient than 48v at 205A?

Regarding the batteries, so you basically recommend one 48v battery? It cannot be less than 48v if I get you correctly? Which Trojan model will you recommend?

Thanks for the suggestions re the panel configuration. I'll work on that.

[easydna]

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

Yes, the batteries were wired in series for 48 volts.

Regarding the max charge, so basically what you're saying is that -- based on my current setup -- I'm giving the batteries way more charge than they need? The solution to this is to get better batteries or reduce the panels?

Wow, that hurts indeed. Getting more batteries at this stage is going to be a bit out of budget; so, essentially, getting 8 6v 370AH battery will solve this problem? If I do this, will it make any difference if I add more panels -- say 200w x 3 (or 6) panels -- hurt, or will it be too much for the batteries?

Thanks for your tip re Temperature Compensated Battery Hydrometer! Will get that

[SunEagle]

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?

Batteries can only be charged at certain rates. Too fast or too slow will hurt them. If you have a 48v 205Ah battery system and have 3150watt using an MPPT charger you could have almost 65amps (3150w / 48v = 65.6 amps) which may be a lot for a 205Ah battery.

removed my question based on previous info.

[Sunking]

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.

I do not know how you have the panels configured. But quite likely you are getting less than 1000 watts from 3150 you think you have.

With 15 panels if you ignored the incompatibility there is only one configuration you could possible use of 5 strings with 3 in series. With a 48 volt system requires you to use at least 3 panels in series to get the minimum voltage of 70 volts required to charge a 48 volt battery. Judging by your lack of knowledge I bet you wired them all in parallel which would mean it would not even work.

[Mike90250]

Inverters have standby / idle losses. Cheap inverters have high losses and low inefficiencies. Good, expensive ones, do not. (they still have losses, and my losses are more than some people would have on their system, but that is my choice) Power Star inverters are completely unknown to me, and I suspect they are not efficient.

Your Charge Controller manual will have information on how to configure it to work with your specific battery bank, You may need an adapter or something to connect for re-programming.

[Sunking]

FLA batteries have minimum and maximum charge rate. Minimum is C/12, max is C8. A 205 AH battery minimum is 17 amps and maximum is 25 amps. 20 amps is perfect. At 48 volts minimum panel wattage = 17 amps x 48 volts = 800 watts and maximum is 25 amps x 48 volts = 1200 watts.

However that does not even answer the questions you need to know the answer to. A 48 volt 2000 AH battery can only give you 2 Kwh per day maximum usable We have no clue what you require or your location to determine panel wattage.

Now some math fun:

12 volts x 200 AH = 2400 wat hours. You have four 12 volt 200 AH bateries. So spin the numbers

12 vots x 800 AH = 9600 watt hours, or all 4 in parallel
24 volts x 400 AH = 9600 watt hours, or 2 x 4
48 volts x 200 AH = 9600 watt hours, or all 4 in series.

Does not matter how you spin the numbers, you have 9600 watt hours of battery capacity. That means about 2000 watt hours per day usable. Is that enough for you?. I don't know, and I don't think you know either. You guessed at everything else and got it wrong.

Your system worked, then you changed it, and it quit working. Logical conclusion says you messed up.

[easydna]

I do not know how you have the panels configured. But quite likely you are getting less than 1000 watts from 3150 you think you have.

With 15 panels if you ignored the incompatibility there is only one configuration you could possible use of 5 strings with 3 in series. With a 48 volt system requires you to use at least 3 panels in series to get the minimum voltage of 70 volts required to charge a 48 volt battery. Judging by your lack of knowledge I bet you wired them all in parallel which would mean it would not even work.

Actually, I didn't wire them; the installation was done my a professional installer. They aren't doing things to my satisfaction, hence my coming over here. And this forum has been more helpful than I anticipated. Thanks everybody!

I also believe I'm getting more than 1,000 watts from the 3,150; I've gotten as much as 45 amps -- and I usually get around 36 amps of charge -- on the average day. I think this ends up being around 1,800 - 2,300+ depending on the kind of sun that's out.

[easydna]

Inverters have standby / idle losses. Cheap inverters have high losses and low inefficiencies. Good, expensive ones, do not. (they still have losses, and my losses are more than some people would have on their system, but that is my choice) Power Star inverters are completely unknown to me, and I suspect they are not efficient.

Your Charge Controller manual will have information on how to configure it to work with your specific battery bank, You may need an adapter or something to connect for re-programming.

Thank you. Yes, I saw the correct settings in the charge controller and configured that; now I guess, with the other changes suggested, I just to monitor and see how things go.

[Sunking]

I usually get around 36 amps of charge .

36 x 50 = 1800 watts.