i have 120V of battery home system how many SW315 panels should I use

The most common system voltages in battery based PV systems is going to be 12, 24 or 48 volt.  The output of the battery based inverter can be 120 or 120/240V.  The quantity of modules that are needed is going to be determined based on the battery bank capacity.  The battery bank capacity is determined by the loads that are going to be fed by the system and includes that maximum depth of discharge of the battery and how many days of autonomy you might want to have.

Take a read through this article.  It might help to guide you in determining your system size and how many modules you will require in your system based on your calculations.

 

hi Adam

Good article thanks for the reply.

My system is a 1937 jacobs rewound to 120v the 60s

and in use by me from 1980.

120v 450ah battery system is a given. My house is half 120vdc and 6kw

homemade 120v inverter gives 120ac and 220ac

So now that iam 68yrs old my wife has decided iam too old to climb the tower

if the wind is blowing hence Solar to keep the batteries happy while I

wate for a calm day to climb and do whatever.

So my question is how many SW315s do i need ?

spec says power point is 36v x4=144v .....x3=108v

but voltage goes higher with reduced current ...

Iam new to solar

thanks

gilligan

Hi Gilligan, Sounds like a great system you have. Unfortunately you will need a battery charge controller to go between the PV modules and the battery. The charge controller does two jobs, it makes sure the PV modules are operating at their peak output (this is known as MPPT control), and it charges the batteries without overcharging them. The problem is that you are going to have trouble finding a battery charger for a PV system that will charge a 120V battery bank. The industry standard is 48V for residential battery banks. It sounds to me like you are considering just connecting enough modules together to get the voltage you want and connecting them directly to the battery bank. I would not recommend that on a system this size. It won't work well and will probably end up damaging the battery bank, the wind charger and the PV modules. So step one would be to find an MPPT battery charger that will work with your battery bank. If you can't find one then you can't go forward with your project. If you do find one then step two would be for you to choose the number of PV modules based on the battery bank size and your energy usage. Good luck, Marvin

Thank you Marvin for your reply

the wind gen has a series diode to stop back flow

my system has a automatic load dump resistor to keep voltage from getting too high(140v)

Hopfully the modules will be ok running direct to battries 105-143v

now step 2: how many modules? and what type ..need around 1kw

thanks

michael