Charging 12 volt Battery Bank

[Rodney123]

I have a 12 volt Battery Bank (24 T-105) Being charged by 16- 75watt, 20volt solar panels
Question= If I added 4- 240watt, 30volt (37volt open circuit) to the Bank would it be bad for the batteries?
What I'd really like to know is, are 30volt panels for 24volt systems or will they work on a 12volt system.
Thanks

[dkpro1]

charge

I have a 12 volt Battery Bank (24 T-105) Being charged by 16- 75watt, 20volt solar panels
Question= If I added 4- 240watt, 30volt (37volt open circuit) to the Bank would it be bad for the batteries?
What I'd really like to know is, are 30volt panels for 24volt systems or will they work on a 12volt system.
Thanks

They are for Grid sys. to use them on a 12 volt sys. you need a MTTP charge controler most can take at least a 150 volt input from aray down to 12volt battery

[inetdog]

They are for Grid sys. to use them on a 12 volt sys. you need a MTTP charge controler most can take at least a 150 volt input from aray down to 12volt battery

There is another, bigger, problem with what you have:
The 75 watt panels have an Imp of around 3.75 amps. The 240 panels have an Imp of 8 amps. Since both the current and the voltage are different, you will have a hard time combining them either in series or in parallel.

Probably your best bet would be to take 6 of your 75 watt panels and put them in series to get 120 volts. Make two series strings, using a total of 12 panels. Then take all four of your 240 watt panels and put them in series to make another string of 120 volts and put all of the strings in parallel. But that will leave 4 of your 75 watt panels left over.
You could also use five strings of 3 75 watt panels to get 60 volts and then make two strings of 2 240 watt panels for 60 volts and put all of those strings in parallel, leaving only one 75 watt panel left over. But that would require more and thicker wire.

In any case, you need an MPPT charge controller to make use of them with a 12 volt battery bank.

If you get an MPPT CC with two separate MPPT inputs, then you could run four strings of 4 75 watt panels to one input and one string of 4 240 watt panels to the other.

I did not take the trouble of calculating what the result would be if you made series strings in which you combined individual 240 watt panels (8 amps) with pairs of 75 watt panels (7.5 amps) but that might work better than leaving out some of the 75 watt panels.

[dkpro1]

easy

There is another, bigger, problem with what you have:
The 75 watt panels have an Imp of around 3.75 amps. The 240 panels have an Imp of 8 amps. Since both the current and the voltage are different, you will have a hard time combining them either in series or in parallel.

Probably your best bet would be to take 6 of your 75 watt panels and put them in series to get 120 volts. Make two series strings, using a total of 12 panels. Then take all four of your 240 watt panels and put them in series to make another string of 120 volts and put all of the strings in parallel. But that will leave 4 of your 75 watt panels left over.
You could also use five strings of 3 75 watt panels to get 60 volts and then make two strings of 2 240 watt panels for 60 volts and put all of those strings in parallel, leaving only one 75 watt panel left over. But that would require more and thicker wire.

In any case, you need an MPPT charge controller to make use of them with a 12 volt battery bank.

If you get an MPPT CC with two separate MPPT inputs, then you could run four strings of 4 75 watt panels to one input and one string of 4 240 watt panels to the other.

I did not take the trouble of calculating what the result would be if you made series strings in which you combined individual 240 watt panels (8 amps) with pairs of 75 watt panels (7.5 amps) but that might work better than leaving out some of the 75 watt panels.

Just use 2 charger controlrs mttp for your 30 volt and leave the other one alone it's done all the time ......

[Rodney123]

They are for Grid sys. to use them on a 12 volt sys. you need a MTTP charge controler most can take at least a 150 volt input from aray down to 12volt battery

deer dkpro1
I did some research on MPPT and one thing I found is that they are very expensive.
I hav'nt bought the 4- 240 watt panels yet until I find out if I can mix them. there a good deal, new at 90 cents a watt.
Anyway all my 16- 75 watt Panels are wired directly to the battery bank with no charge controller in between,I threw it out 20 years ago.
I also have 4- 12 volt 40amp battery chargers wired directly to the battery bank for cloudy days.
Once every 4 to 6 weeks I pump up to 14.9v to 15.1v to top the batteries off. I run the battery chargers in the middle of a sunny day along with full sun on the solar panels.thats the only way i can get 14-15v.
my question is will 240watt-30volts hurt the batteries?
Just some Background trivia. I've been running off the grid like this for 24 years. I replace the batteries about every 6 years. I use a 3000 watt pure sine wave inverter for the hi-teck side of the house (TV,computer, etc) and a 3000watt regular (square sine) on the kitchen-garage side of the house.
If you see any mistakes here (minor or major) please let me know.

[Sunking]

deer dkpro1
I did some research on MPPT and one thing I found is that they are very expensive.

Yes they are and worth every penney. Once you get above 200 to 300 panel watts MPPT is much less expensive.

It takes 1500 watts of panels with a PWM controller to do the same amount of work as a 1000 watt panel with a MPPT controller.

[Rodney123]

Chemical Battery Reconditioners

Does anyone have any comments (pro or con) on chemical battery reconditioners.
Do they work?
Are they bad for batteries.

I have a bank of 24 Trojens T-105 that i bought new 5 years 2 months ago. They are being charged by 48-75 watt Siemens solar panels hooked to 3 - 60 amp MPPT charge controllers in parallel. 16 Panels per controller. Any information or suggestions would be help full.
Thanks

[thastinger]

You have a 2 series, 12 parallel battery configuration which you have chronically undercharged from 1200W of panels for over 5 years...I'd say they had a pretty good run.

[Wy_White_Wolf]

Does anyone have any comments (pro or con) on chemical battery reconditioners.
Do they work?
Are they bad for batteries.

I have a bank of 24 Trojens T-105 that i bought new 5 years 2 months ago. They are being charged by 48-75 watt Siemens solar panels hooked to 3 - 60 amp MPPT charge controllers in parallel. 16 Panels per controller. Any information or suggestions would be help full.
Thanks

3 design problems.

1. 12 parrallel strings. Impossible to keep them balanced. You should design systems with as few parralleled strings as possible.

2. 1200watts of panels on charge controllers that can only handle 720w (60Amp * 12V) of array. Drop down to 9 panels per controller and get a couple more controllers. No need to add more panels as you have more then they can handle now.

3. 180 amps (max for 3 controllers) charging a 2700AH battery bank. Thats a rate of C/15 which is not high enough to properly charge them. Your rate needs to be between C/8 and C/12 with C/10 being about perfect. Adding 2 controllers as suggested above would put you at 250A of charging and would put you in that range (C/10.8).

I say you did good to get 5 years out of them with your design problems. That much power and storage is really screaming to be a 48v system and it would be wise to change to one if you are replacing the battery bank.

WWW

[paulcheung]

He better get rid of those two 12volt inverter and buy a 48 volt 3000watts pure shine wave inverter and rewire the batteries to 3 strings 48 volts bank, he only need to use ONE 60 amps MPPT charge controller to charge those batteries. life would be much easier.

[SunEagle]

3 design problems.

1. 12 parrallel strings. Impossible to keep them balanced. You should design systems with as few parralleled strings as possible.

2. 1200watts of panels on charge controllers that can only handle 720w (60Amp * 12V) of array. Drop down to 9 panels per controller and get a couple more controllers. No need to add more panels as you have more then they can handle now.

3. 180 amps (max for 3 controllers) charging a 2700AH battery bank. Thats a rate of C/15 which is not high enough to properly charge them. Your rate needs to be between C/8 and C/12 with C/10 being about perfect. Adding 2 controllers as suggested above would put you at 250A of charging and would put you in that range (C/10.8).

I say you did good to get 5 years out of them with your design problems. That much power and storage is really screaming to be a 48v system and it would be wise to change to one if you are replacing the battery bank.

WWW

I think the OP got some of us confused. He took a 2 year old thread where he had (at that time) 16 x 75w panels (1200watt total) charging a large 12volt battery system without any CC and he wanted to add some 240watt panels to the system.

The OP now has a system consisting of 48 x 75w panels (3600watt total) charging his 24 x Trojens T-105 battery system using 3 x 60amp MPPT Charge controllers with 16 x 75 watt panels each.

His question is will those chemical battery "conditioners" work on his 5 year old system.

Regardless of how he is now charging his batteries I would say I have not heard any good things about chemical battery conditioners. More than likely his battery system is at it's end and will need to be replaced.

[Sunking]

Has anyone noticed this is a 3 year old thread?

[thastinger]

Has anyone noticed this is a 3 year old thread?

I did but the OP is the one who resurrected it. I didn't know the timeline that suneagle posted though.

[Sunking]

Does anyone have any comments (pro or con) on chemical battery reconditioners.

Snake Oil. The box it comes in is worth more and more uses than the product inside.

[Rodney123]

Chemical Battery Reconditioners

He better get rid of those two 12volt inverter and buy a 48 volt 3000watts pure shine wave inverter and rewire the batteries to 3 strings 48 volts bank, he only need to use ONE 60 amps MPPT charge controller to charge those batteries. life would be much easier.

Thanks for the information and suggestions everyone.
Would someone explain what C/8 and C/12 with C/10 means.
Also I haven't heard anything about chemical Reconditioners yet. Getting one more year out of my batteries would be nice if at all possible.