Solar charger controller question??

12 Posts
Oct 22, 2010 05:42 pm
Solar charger controller question??

Hi Guys,

I have 840watts off solar panels, and 25 12v 72a/h deep cycle batteries, and I'm wandering if my solars will be capable of charging all those batteries and if so what charge controller should I use?  Thanks in advance.
46 Posts
Oct 24, 2010 05:12 pm
Re: Solar charger controller question??

840w of solar sounds like just about enough to charge most any battery bank. the big question is how are you going to wire them all up? or maybe more importantly, what will you be using the power for? just a little power in your shed or maybe a car port for your rv? then you may want to stick with a 12v system. something for the home? then perhaps a 24v or 48v system would be better.
you have a lot of batteries all at the smaller end of amp capacity. you would probably be better running a 48v system to avoid paralleling too many strings (on both the battery end as well as the module end).
you will need to calculate what voltage you will be running at, then what the amperage will be, then what charge controller will be able to handle what you're pushing.
more info would be helpfull in answering more specifically.
what exactly are the modules? vmp? imp? -m
12 Posts
Oct 25, 2010 08:58 am
Re: Solar charger controller question??

I was gonna try to use them as my power back up for my house, since there's 25 of them, i think that's enough for a back up. Also 24volt power inverter is something i was thinking of using, not sure if i should go with pure sine or just modified. I have few upses so i guess i dont really need pure sine.  Let me know.  thanks
12 Posts
Oct 26, 2010 11:30 am
Re: Solar charger controller question??

Here are the specs for my panels:

Power (W)      210 Watts
Open Circuit Voltage (V)    22.80 Voc
Short Circuit Current (A)    12.11 Isc
Maximum Power Voltage (V)    18.30 Vmp
Maximum Power Current (A)    11.48 Imp
46 Posts
Oct 26, 2010 11:49 pm
Re: Solar charger controller question??

hey marcin, looks like you have 4, 12v nominal modules (evergreen perhaps?). this makes 12, 24, or 48v system relatively straight forward. 25 batteries is not an even number, so something will have to happen there.
mppt charge controller will be the best charger available to you, but you have many cheaper alternatives. the mppt controller can potentially yield up to 30% more "juice", but if this is only temporary or emerangcy power then a pwm controller is a very viable option. i have a c40 and have had no problems with it. i got the optional display so i can see a little bit of whats going on. morningstar also has a huge selection at a reasonable price. i have never used their products hut have heard good things. i think displays are always good, unless you plan on having some other monitoring device ( like a trimetric battery monitoring). nice to know what is happening (or was happening).
try to pick an inverter or two that you like before you decide on a charge controller. some inverters have charge control features, others will affect your choice of charge controller (24v inverter with a charge controller that does not have a 24v option, etc...).
12 Posts
Oct 28, 2010 09:07 pm
Re: Solar charger controller question??

I purchased Morningstar MPPT 60A, and will probably configure them in 24v setup since this is how they are connected right now to my grid tie inverter.  Thanks for all your suggestions
220 Posts
Oct 28, 2010 11:01 pm
Re: Solar charger controller question??

 hi marcin,

 isn't this stuff fun! sounds like you have some nice equipment there.

 i believe you should look into running your pv modules as one string of four in series with a 91voc and 72vmp with a corrected voc of well under the max allowable..(theres no place cold enough to go over).

 no worries with the wire run at that voltage and 11.5 imp.(~18.9 isc corrected) we should be good to go with a very reasonable wire size. (with the bonus of no pv combiner needed)

 we still have issues with all those parallel strings of batteries though. i would not even attempt to parallel them at the battery level and would go straight for a busbar setup.

it's all good fun!
cheers, dave

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