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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3674
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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I am seeking advise on the best component matching for a small

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I am seeking advise on the best component matching for a small 12 Volt home solar powered system

Hello name is XXXXX XXXXX I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!


1) What loads do you wish to power using solar?


2) Will the loads be DC or AC? Also how many amps?


3) What equipment have you purchased so far? Panels, Charge Controller, Batteries, Inverter, etc? I will need quantities as well as the size of the component wattages, amp-hours, etc.


Let me know what you have Joel and we can take it from there........Thanks...........Kevin!

Customer: replied 3 years ago.

Hello Kevin Thank you below are the components I have purchased with their links to amazon if you need any further info. Will these components work together?


Solar Panel Cable 50 Ft - Mc4 Pv Extension- 10awg - 600vdc - Sunlight Resistant
Sold by Shop Akari

SunforceNNN-NN-NNNNWatt Pure Sine Wave Inverter


I bought 2 of these batteries

Schumacher SB 121000 '12V' 100Ah AGM Sealed Lead Acid Power Sport Battery


TRACER MPPT 3215RN Solar Charge Controller 30A 12V 24V EP


Battery Tender(NNN) NNN-NNNNDL-WH 12-Volt 4-Bank Battery Management System


Instapark® NEW All Black 150w Mono-crystalline Solar Panel, 150 Watt
Maximum Power Voltage: 18.12V; Open Circuit Voltage: 22V; Maximum Power Current: 8.28A

1) How many panels?
Customer: replied 3 years ago.

2 panels

Thanks for the replies Joel


1) All of the components look good except the battery tender. I assume that you will be using the battery tender to keep the batteries at full charge during the evening hours? If so, you only want to use the tender during the evening hours and never during the daylight. If using the tender simultaneously with the PV panels, possible to over-charge the batteries. To play it safe on the tender, I would recommend to plug the tender charger into a timer and only have it top-off the batteries during evening hours.


2) You will also need a roof mount or a pole mount to mount the panels. The mounts are always made of metal and need to be grounded using an Inter-system bonding device at your existing ground rod near your electrical meter socket. The equipment grounding conductor needs to be sized as 10 AWG Copper.


3) Code also requires a safety disconnect switch located on the exterior of the home prior to the cables being routed into the house. Since each panel is rated @ 8.28 amps, you could purchase an air conditioning disconnect switch (non-fusible type) 30 amp rated, 2 pole and weatherproof type that would be able to cut power from the PV's for any maintenance and/or safety reasons.


4) The 2 batteries will be installed in parallel for a 12 VDC output. You also need 2 plastic battery cases to protect the batteries.


5) Depending upon the distance from the PV's to the battery bank, you may want to consider increasing the cable size from 10 AWG to 8 AWG due to any voltage drop. I would need to know the approximate distance in order to calculate the voltage drop.


6) You will also require a combiner box or weatherproof junction box (NEMA 3R rated) for combining the PV cables on the exterior.


7) If you will be grid tied to your main electrical panel, let me know.




Hope this helps.........If you have any additional questions, let me know and I'll be glad to answer them for you.


Otherwise, don't forget to rate me before you log Off.


The next time you have an electrical question, you can also request for me at:




Customer: replied 3 years ago.

Thank you Kevin. The distance will be 25 ft from the panels to the charge controller. Also up to how many similar spec batteries can I add to this battery bank with the existing components I have for this system? And can I add different brand 12 V batteries? And if so do they also have to be exactly 100Ah or is it ok if they will be 12V 110Ah?

1) One additional code requirement I forgot to mention. If the PV cables will be passing thru the home prior to landing @ the exterior disconnect switch, the cables need to be routed in their own separate conduit and not shared with any AC high voltage conductors.


2) As an optional component......I would also recommend a lightening protector.


3) It is always recommended that batteries be the identical amp-hours and manufacturer. If the amp hours are different, there is a tendency for the weaker battery to bring down the stronger battery.


4) 25 feet distance is fine and that is not a problem then for the cable size


5) The quantities of batteries in the battery bank depend upon your daily connected loads and the amount of reserve amp-hours that you will require. You have 200 AH using 2 batteries. General rule of thumb is to have a 50% AH reserve on the batteries for up to 3 days with no sun. Therefore a 50% reserve would result in having (1) one battery @ 100 AH readily available over a 3 day period without sun light. Let me know how many connected amps and the amount of daily hour usage you will have and I can calculate that for you.


6) Joel......I need to log off of here for a few hours. Post any other questions or replies here and I will get back to you later this afternoon............Thanks.............Kevin!

Kevin and other Electrical Specialists are ready to help you

Hello Joel.............Thank you for the excellent service rating..........much appreciated!


If you have any other questions, just let me know.


Take care and have a great evening.............Thanks...............Kevin!

Customer: replied 3 years ago.

Hello Kevin just a quick question. You mentioned above that 10AWG wire will be fine for a 25 foot run. Is 10AWG still good for a 50 foot run from solar panels to charge controller?. And if not how long would it be good for, until I need to consider a 8AWG. Thank you again for all of your help, Joel

Good morning Joel,

1) The National Electrical Code recommends a maximum voltage drop (VD) of 3%. Using 10 AWG Copper at 18 volts and 16.5 amps, the VD maxes out at a 33 foot run (3%).

Using 10 AWG copper at a 25 foot run, the VD = 2.28% which is < than the maximum recommendation of 3%, therefore OK.

This is calculated based on the panels being installed in parallel with each other. For a parallel circuit the panel voltage remains the same (18 VDC), but the amperage is additive (8.28A + 8.28A) = 16.5A

2) Using 8 AWG copper at 18 volts and 16.5 amps, the VD maxes out at a 52 foot run (3%)

Hope this helps...........reply back with any questions..........Thanks..........Kevin!
Customer: replied 3 years ago.

Thank you that is very useful. Is there a website that shows all this and more for future reference. Thank you, Joel

No problem, glad to assist Joel

1) There are numerous web sites for a voltage drop (VD) calculator. I use the following for calculating DC voltage drops.

2) I also have a variety of National Electrical Code (NEC) and electrical theory books that I often use as well. Some of the calculations require looking up information in tables and then performing a manual calculation for combination series/parallel circuits. Just kinda depends what source has the required information. A good example of this is that some websites recommend a maximum of a 4% VD, where as the NEC recommends a maximum of a 3% VD.