# a newbie question regarding 3 solar panels and charger controller

Registered Users Posts: 4
Hello,

I have a triplite 3636 power backup and was used with the area power lines.

these days we are not able to get electricity from power lines so I bought 3 100W solar panels to charge the batteries.
when I use the multimeter I found that the voltage is not 36v (56v sometimes), is this OK?

I read that an MPPT controller is required to control the charging operation, but most of the controllers I found was noted it is 12/24 V only while it mention that it is for systems upto 48v, please advice

sorry this is my first time regarding solar systems so I think my question might be a bit less explaining.

regards

Maz

36 volt battery bank, the UPS specifications says.

56 volts is awfully high charging voltage, roughly equal to 18.7 volts on a 12 volt battery. Depending on the type of battery:

Flooded Cell -- 14.7 volts typical absorb voltage set point--Perhaps 15 to 16 volts for Equalization (something like 1 hour per month typical)
AGM -- 14.4 volts typical absorb. No equalization
GEL -- 14.2 volts typical absorb. No equalization

Float charging is usually somewhere around 13.6 volts or so.

Multiply those numbers by 3x for 36 volt battery bank:

Flooded Cell -- 44.1 volts typical absorb voltage set point--Perhaps 45 to 48 volts for Equalization (something like 1 hour per month typical)
AGM -- 43.2 volts typical absorb. No equalization
GEL -- 42.6 volts typical absorb. No equalization
Float -- 40.8 volts (roughly)

All the above is at room temperature. If the batteries are very warm, the charging voltage should be reduced a bit. If the battery bank is very cold, then charging voltages are increased.

36 volt battery banks are not a common voltage for solar charge controllers--You will have to find a controller that is programmable for a 36 volt battery bank (12/24/48 volt banks are common for solar).

What type of batteries do you have and how many Amp*Hours is the battery bank? AGM and GEL batteries do very poorly when over charged. Flooded cell do better because you can add distilled water when needed--But still not good to over charge them either.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 62 ✭✭✭✭
36V to 56V, is that voltage of the panel?

Seems like you've those panels connected in series.

If you're using MPPT charge controller (cc), it's okay, since the cc will take those 36V-56V and adjust it to proper voltage of your batteries (set batteries voltage of cc first, some cc detect automatically).

You're not stuck to MPPT, PWM charge controller will do fine, but MPPT surely perform better to get the max of your panels.
After obtain the cc, you can set charging voltage to proper point.

Simply connect cc to panels and batteries, set right voltage of the cc according to your batteries voltage (12/24/36/48 ), set proper charging voltage of batteries (flooded/AGM/etc.) and you're good to go. CC will control the charging process and take care of your batteries.
Mulia is correct... I should have asked if you are measuring 56 volts at the solar panels or the battery bank.

If you are measuring the solar panels--Voc is roughly 21 volts (voltage open circuit) so three panels in series would be roughly 63 volts Voc--Perfectly normal.

How the panels actually operate depends on the charge controller. There are PWM (pulse width modulated) types (lower cost, simple on/off type switching). And MPPT type (Maximum Power Point Tracking) which are sophisticated DC to DC switching power supplies. There are advantages and disadvantages to both types of controllers--For smaller systems, PWM is usually less expensive. For larger systems, it is generally easier to wire up MPPT type systems (you can run higher Vmp-array voltages and use smaller diameter copper cable from the array to the charge controller).

Have you purchased a solar charge controller yet?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4
Thanks [USER="512"]BB.[/USER] and [USER="15424"]mulia[/USER]

Yes, I measured the volt at the panels side (not connected VOC) , I'll check it (connected to batteries only) tomorrow while the sun is up :cool:

I have the panels connected in series to get it connected to the batteries (100AH normal car batteries - flooded I guess).

regarding the CC, I have no idea what type I should purchase, thats why I asked here cos I am a bit confused

thanks again for your kind replies
Where are you located? Germany?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4
BB. wrote: »
Where are you located? Germany?

-Bill

No, Yemen

I just go through Sat internet as the area is not yet covered by adsl
If you are looking to spend a lot of money--There are a lot of 36 volt charge controllers of the MPPT type (expensive--typically \$300 to \$600 or more). They are highly programmable (anything from 12 to 48 volt, or sometimes higher voltage, battery banks)..

For less expensive PWM--I am not sure of any (I am not in the solar business). There are ones from China like this one:

http://www.dealsong.com/item/2008894618.html

I have no idea of the website or if the controller itself is any good.... Just an example of what to look for.

Perhaps somebody here can give you some pointers to good vendors/product.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 62 ✭✭✭✭
maznos wrote: »
Yes, I measured the volt at the panels side (not connected VOC) , I'll check it (connected to batteries only) tomorrow while the sun is up :cool:

I have the panels connected in series to get it connected to the batteries (100AH normal car batteries - flooded I guess).

regarding the CC, I have no idea what type I should purchase, thats why I asked here cos I am a bit confused

If you just want to have it as backup (as it now), you can go with PWM controller, really cheap compared to MPPT, I've both, but the I don't use the PWM yet, it's for backup.
But if you want to build system to supply household demand/almost non stop and want to expand your array/panels, you better go with MPPT.

If you want good brand PWM, perhaps Morningstar is a good choice (seems to be), although they have bad customer support by email, took almost 9 months to reply my email.
Cheap PWMs are so many on market, here in my country, people tends to use EpSolar brand, it's China brand.

Btw, make sure you DIDN'T connect the panels directly to the batteries without charge controller, the high voltage produced by those panels will critically damage your batteries..
• Registered Users Posts: 4
Hello my friends
BB. wrote: »
If you are looking to spend a lot of money--There are a lot of 36 volt charge controllers of the MPPT type (expensive--typically \$300 to \$600 or more). They are highly programmable (anything from 12 to 48 volt, or sometimes higher voltage, battery banks)..

For less expensive PWM--I am not sure of any (I am not in the solar business). There are ones from China like this one:

http://www.dealsong.com/item/2008894618.html

I have no idea of the website or if the controller itself is any good.... Just an example of what to look for.

Perhaps somebody here can give you some pointers to good vendors/product.

-Bill

I just found this one: http://www.aliexpress.com/item/10A-36V-48V-60V-wincong-sl03-4810a-solar-Charge-Controllers-LCD-Li-Li-ion-lithium-LiFePO4/2001632804.html

what do you think?

mulia wrote: »

If you just want to have it as backup (as it now), you can go with PWM controller, really cheap compared to MPPT, I've both, but the I don't use the PWM yet, it's for backup.
But if you want to build system to supply household demand/almost non stop and want to expand your array/panels, you better go with MPPT.

If you want good brand PWM, perhaps Morningstar is a good choice (seems to be), although they have bad customer support by email, took almost 9 months to reply my email.
Cheap PWMs are so many on market, here in my country, people tends to use EpSolar brand, it's China brand.

Btw, make sure you DIDN'T connect the panels directly to the batteries without charge controller, the high voltage produced by those panels will critically damage your batteries..

BTW, we were using the triplite 3636 as backup but now there is no power lines at all, my idea is to charge using solar panels.

I have tested the panels while connected to batteries and the reading was 37-38v 5.5A (100W panels), what do you thinks?
and what about making the batteries charge from solar all day long as we drain the batteries all night long? this is only untill I get the PWM I found

Regards
• Solar Expert Posts: 62 ✭✭✭✭
That's surely really cheap PWM charge controller with quite lots of features. Just can't verify its quality and durability.

The cc max current is 10A which is acceptable to your case (3 100W panels in series usually Isc 6A-ish)

CC max voltage is <100 which still acceptable to yours (Voc total 69ish)

Are you connecting those 3 panels in series to your batteries directly? With your 3 panels in series, it can produce about 60V, you shouldn't connect it directly to batteries.

Worse, without cc, at the night, when your panels produce no power, it will "sucks" power from your batteries, unless you've some blocking diode installed.

37-38V 5.5A, where did the number came from? 1 100W panel usually producing about Voc=22Vish and about 5A at 25C-27C.

That's okay if you just want to use the batteries all night without using it at daytime while. But, if you can transfer most your nighttime load to daytime, it'll be much better since your panels charge the batteries when sun is shining and you can use "excess" power that your batteries can't absorb anymore (in case your power usage is less than or almost equal to power produced by your panels).

I wonder how large is capacity of the battery bank, can't find its capacity on website.
maznos wrote: »

I have no idea... All I can say is it is cheap enough to try--Assuming they can mail it to you and accept your payment.
BTW, we were using the triplite 3636 as backup but now there is no power lines at all, my idea is to charge using solar panels.

I have tested the panels while connected to batteries and the reading was 37-38v 5.5A (100W panels), what do you thinks?
and what about making the batteries charge from solar all day long as we drain the batteries all night long?

UPS systems are not always the most efficient--They can take quite a bit of energy to just "turn on" even without loads (20-30 watts is not uncommon). Also, an inverter that is that large takes a relatively large battery bank to run at full power... Using our typical rules of thumb for a full time off grid home/business, a 3.6 kWatt 36 volt inverter would need around a 480 AH @ 36 volt battery bank.

And to charge a flooded cell lead acid battery bank, you would need a 5% to 13% rate of charge (another rule of thumb):
• 480 AH * 44.1 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,375 Watt array minimum (weekend/seasonal use)
• 480 AH * 44.1 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 2,749 Watt array nominal (full time off grid)
• 480 AH * 44.1 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 3,574 Watt array "cost effective" maximum array
You can use the Solar Electric Handbook to estimate how much sun you will receive, but assuming you get lots of sun, say 5 hours a day average minimum then a 10% size array would generate:
• 2,749 Watt array * 0.52 typical system efficiency * 5.0 hours of sun (average minimum) per day = 7,147 Watt*Hours per day
Say you have a 600 Watt load, the system can supply:
• 7,147 Watt*Hours per day / 600 Watt load = 11.9 hours of operation per day
Anyway--From what you can see, if you design a system that can support your 3.6 kWatt inverter--This is not a small system, and you are looking at a pretty large solar array (more than large enough to justify a MPPT type solar charge controller). And this is not a cheap system... All to supply an approximately 600 Watt AC load for ~12 hours per day.

300 Watts of solar panel will be just enough solar to keep the batteries "floating" (in storage, not really drawing much power). Unless you plan on using a generator set for charging daily.

Is this anything close to what you where expecting and to fund?

Solar power is expensive. And I like to design the system for your loads rather than around some piece of hardware. In general, you would be much happier to design the system for your loads. It is rare that hardware you already have (in this case a UPS) will meet your needs well.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Yes, you can directly connect the 300 watts of solar panels to your battery bank. As long as you monitor the batteries to make sure they do not over charge.

Also, it does depend on the Amp*Hour size of your battery bank... A 500 AH @ 36 volt battery bank would take ~5 amps as a "float charge" and not be very hard on the battery bank even if you left it connected.

However, if you had a 100 AH battery band, then 5 amps would need to be watched pretty closely to ensure you do not over charge/"boil" the battery bank.

Note that car type batteries are not designed for deep cycling... If you take them much below 85% state of charge, they will not last very long (weeks/months) before they wear out.

I really think you are not going to be very happy with the approach you are taking right now. I understand that you have to make do with what you have access to.... But this is not going to turn out well.

I would highly suggest you look at the load you want and then design (on paper) a system to support those loads... Then look at what hardware/batteries/etc. are available to support those loads.

And those loads should be very energy efficient (smallest loads you can use to do the job). Solar power is expensive.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset