Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

I guess you are using a Proxy, so we cannot tell where you are from... We try to give answers that are, at least, regionally aware (line voltage/frequency, the amount of sun per day by season, local to you hardware suggestions)... So, for now, the generic answers.

As Marc/Cariboocoot says, we can either design the system for the loads or design the system based on something you already have (solar panels, battery bank, etc.).

Since you are "camping", then I would assume no Grid Power is available for charging during multi-day use.

Your limit of 2x65 watt panels... That may be a lot of power for somebody truly camping--But for somebody setting up a remote office/lab, that is not very much power--So, your selection of what you want to operate is very critical to the success (or failure) of your off grid system choices.

First, how much power can you get. For an off grid system that is running a smallish AC inverter (say 300 watts or less, on only on when needed), the assumed hours of noon-time equivalent sun per day can run from 4 hours (~9 months of the year for many places without heavy marine layer) to ~5-6+ hours of sun per day for Summer. During winter, 2-3 hours of sun is common for places closer to the poles (tropics, there is very little change for winter/summer sun unless it is weather related). In some places, less than 2 hours--And you may go days or longer with almost no useful sun (dark cloudy weather)...

So, back to the estimates:

• 2* 65 watt panels * 0.52 off grid system efficiency * 4 hours of sun per day = 270 Watt*Hours per day

Yes--We are talking about ~50% in "losses" from solar array name plate ratings to useful AC power output...

Now--that 130 watt refrigerator--About 2 hours of available power per day:

• 270 Watt*Hours * 1/130 Watt load = 2.08 hours per day

So, there is your daily power budget--~270 WH per day (typically early spring/late fall in clear weather--probably more in summer).

Charging a battery bank... The typical rate of charge for a Lead Acid Battery bank is around 5% to 13% rate of charge:

• 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.05 rate of charge * 1/14.5 volts charging = 138 AH maximum battery @ 12 volts
• 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.10 rate of charge * 1/14.5 volts charging = 69 AH nominal battery @ 12 volts
• 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.13 rate of charge * 1/14.5 volts charging = 53 AH minimum battery @ 12 volts

The 5% rate of charge is minimum recommended--And works best for a system that charges during the day and discharges at night.

If you have a system that needs to produce power throughout the day, a 10% or higher rate of charge is better--Remember the loads during the day reduce charging current to the battery bank (which should be a minimum of 5% rate of charge).

Your next problem is that you can only draw so much power from a battery bank before it is damaged/collapses... For example, the recommended sustained discharge rate for flooded cell is ~C/8 (20 hour capacity rate discharged over ~8 hour time period). And you should not discharge more than ~50% at a time for longer battery life (and never discharge below ~20% state of charge or it can ruin the battery bank). Using the 69 AH nominal battery bank as an example:

• 69 AH * 1/8 hour discharge = ~8.6 amp discharge rate
• 8.6 amps * 12 volts * 0.85 eff efficient inverter = 88 Watt average load
• 69 AH * 0.50 recommended max discharge * 12 volt * 0.85 inverter eff = 352 Watt*Hour available storage

Note, a 20 Hour Rate battery will appear to have less AH capacity if discharged at a C/8 rate.

The maximum surge current from a Flooded Cell battery would be C/2.5:

• 69 AH * 1/2.5 discharge = 27.6 amps max surge (seconds to minutes)
• 27.6 Amps * 12 volts * 0.85 inverter eff = 281 Watts maximum surge

Now, AGM (and GEL) batteries have some different parameters--For example AGM/GEL can support much higher discharge rates--So, if you have loads that needed high surge current but low average power, AGMs may be an interesting solution...

Anyway, will stop here and see what questions you have.

-Bill

Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

Your car battery is probably on the order of 80 AH at 12 volts = 960 Watt*Hours...

A small generator running fairly efficiently will give you around 3,000 WH to near 6,000 WH per gallon of fuel.

So--car sized deep cycle battery contains ~1/5th the amount of energy as a gallon of gasoline.

Lead Acid (and really most any battery) does not store a lot of energy vs liquid fuels (gasoline, propane, diesel, etc.)... The advantage to a battery system is that it can be recharged with a solar array... To get ~5kWH from a solar array in decent sun (4 hours a day or more for 9+ months of the year):

5,000 WH * 1/0.52 end to end system efficiency * 1/4 hour minimum sun per day = 2,403 Watt Solar Array Minimum

So--if you want to have 5 days of emergency power @ 5 kWH of 120 VAC power per day (a pretty good sized amount of power)--You would need around 10x car sized deep cycle batteries + 2,403 Watts of solar array + AC Inverter + DC charge controller...

Or a Honda eu1000i (900 watt) or eu2000i (1,600 watt) generator + 5-7 gallons of gasoline.

Of course--The solar power system will continue to crank out power for 300+ days a year (excluding bad weather/deep winter). The genset would need another 1+ gallon of gasoline per day.

This all gets back to your needs/loads... Small off grid solar power systems will only power small loads. Solar power is good where you need 9+ months of off grid power. A fuel powered genset is good for a few days of outages or weekend/seasonal cabin (with possibly a small battery+solar system for a few lights, radio, cell phone charger, etc.).

Batteries start dieing the day they are made... They will last typically 3-7 years or so for golf cart type batteries in normal usage, or just sitting there in float charge... A generator will usually keep for a decade or more if properly stored. Gasoline/diesel will keep for ~1 year with fuel stabilizer (recycle to vehicle), propane will keep "forever".

I highly suggest you look at your needs/loads first... Then start looking for hardware that can meet those needs. Typically "kits" are not as cost effective as DIY--But kits do have their place too.

Just picking out random kits/hardware is probably not going to do much for you unless you are looking for something to charge your cell phone when camping...

-Bill