Construction Trailer setup

[JWilder]

Hello to all

Newbie here and was looking for some information. Setting up a construction trailer that will run off a 20 KVA generator for approx 12 hours day, need solar/battery backup to run my security system 0.9 Amps / wireless router 0.8 Amps/ and small fridge 1.5 amps all are 120v. when generator is not on and for the weekends. I have tried calling several solar place here in Southern CA where the jbsite is but everyone wants to sell me a 5K system. Do I need something this extreme? Could someone please put together a list of items that I would need so I could put this together myself. Any help would be greatly appreciated

Thanks
JW

[Mike90250]

Hello to all

Newbie here and was looking for some information. Setting up a construction trailer that will run off a 20 KVA generator for approx 12 hours day, need solar/battery backup to run my security system 0.9 Amps / wireless router 0.8 Amps/ and small fridge 1.5 amps all are 120v. when generator is not on and for the weekends. I have tried calling several solar place here in Southern CA where the jbsite is but everyone wants to sell me a 5K system. Do I need something this extreme? Could someone please put together a list of items that I would need so I could put this together myself. Any help would be greatly appreciated

Thanks
JW

The fridge is the deal killer. The really good energy star fridges consume about 1Kwh of power a day. That leads to a large battery bank, and a large array to charge it.
I'll assume the security gear, is also 120VAC specs

.8 +.9 = 1.7A x 120V = 204watts x 24hr = 4,896 watt hours

Running "little stuff" 24/7 adds up !

I'll assume (for So Cal) you can get 5 hours sun in the winter, and you will need 3 days of autonomy for a long weekend.
3 days =14,688wh Battery should be at least 2x that size, since wintertime, we get cloudy weekends. A 29,376wh battery @ 48V = 612A L16 size, 6V batteries are about 400Ah, and might be a place to start. A cloudy 3 day weekend will take them down to 80% discharge. Should last you at least 2 years, longer if good weather on weekends.

Your solar array would need to provide 10% of battery capacity to keep batteries charged, and prevent electrolyte stratification. That's about 60A @ 55V (3.3Kw) of PV needed to keep them happy. The array will power the gear on the weekend, while it's recharging the batteries!

You could skip the solar, and just use the generator to recharge the batteries.

Add a 48V inverter, 48V charger, and you are set ! Solar, you would need a charge controller too.

You can trim battery bank size back even further, reduce the array a bit, but your security will go down after 2 dark days

(This looks like a huge system, but it needs to be, if you need security 24/7)

Someone check my math, I'm recovering from a cold, and not at 100%

[JWilder]

Construction Trailer

Mike

Thanks for the help. OK no fridge for sure. So to start I will just use the generator to charge the batteries no solar to save $$. If charging with battery charger do I need to double the WH's for storage? How many batteries would I need? What voltage would be the best 6/12/24/48 for longer storage or does it matter? I would rather stay with 12 or 24 V to minimize charger/inverter cost. Can you recommend a good 24 volt charge/inverter?

Once again thanks for your help

John

[Mike90250]

You need to use 48V. This will need a pretty large battery bank to get through the 2 day weekends

Regardless of the power source, you need a charger, solar or generator & charger, still need 10% of the battery bank capacity in charger. Going with 400AH batteries, you need a 48V 40A charger, likely at 240VAC.

Suggestion:
XW6048 inverter/charger Has generator input for sloppy voltage/freq acceptance, 100A charger, and 6KW 240/120VAC outputs. And automatic transfer switch.
It's overkill, but all wired into 1 package. Only a few $ more than it's smaller brother the 4048.
Compare it to buying all the parts (inverter, charger, misc pieces) separate and wiring it together.