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karrlot 05-11-2016 11:01 PM

Help Determining Electrical Needs
I am still in the beginning stages of building. I am trying to determine what size converter/charger I will need. I may be putting the cart ahead of the horse, but I want to use the charger for my chassis batteries (which are dying but still have a little life left in them) for the time being. I would just as soon buy the charger now.

There are lots of calculators out there that will help me figure out what size batteries and chargers I will need based on the appliances I use, but my problem is I don't know what I will be using.

I have an 11 window/65 passenger bus. I will mostly be doing weekend camping without hookups. I will have a fridge/freezer (but that will run off of propane), a water pump, lights, a radio, ventilation fans.

I will not have a TV, but might want to include capacity for that just in case. I don't plan on having a microwave or hairdryer.

I do not plan on using a generator, but do want to leave the possibility of expanding to solar later on.

I am kind of stuck because I don't know how many lights I'll use, how much I will be using the water pump, etc.

Can you give me advice based on an estimate of what you use?

Robin97396 05-12-2016 10:21 AM

I estimate I'll be using about 10 kWh per day. I estimated 2.07 kWh per day for small items like lights, while the fridge draws 7.2 kWh per day, for a total of 9.27 kWh per day.
When setting up a power system, such as house batteries in my case, I double my estimate of power usage to 20 kWh's per day and set things up to handle that power requirement. Always better to err on the side of to much than to little.

family wagon 05-12-2016 01:56 PM

Robin, are you sure your fridge draws 7.2 kWh per day? It's been a while, but I thought I measured (with kill-a-watt) in the neighborhood of 2 kWh for mine which is "small household" size (about 15 cu ft probably). Seems like it ran at about 120 watts and close to 50% duty cycle over the full day.

Robin97396 05-12-2016 03:15 PM

I tend to err on the side of excess. I don't have a killowatt guage so I just used the wattage ratings on my appliances, or ratings off a chart, which may have been household ratings. When it comes to power I'd rather have to much than not enough, with finances as the limiting factor.

karrlot 05-12-2016 07:34 PM

Thanks! So that fridge runs oof of electric, or it runs off of propane but still uses that much electricity?

Does anyone else have estimates of what they use?

Robin97396 05-12-2016 07:46 PM

It all depends on your appliances. There are lots of charts online that you can look at for hours. What you decide you need to squeeze into your bus to make it livable for you is what you need to manage power for. Some people go pretty far with their builds and others like me are more the minimalist type. You build it for you.
If you buy a nice newer low power consumption fridge it will help you a lot on your energy costs. I'm using a $20 fridge that I bought used about 20 years ago. I'm going for the chest freezer/fridge setup.

turf 05-12-2016 08:21 PM

there are some good calculators online to help estimate appliances. i think they tend to run over as well.

when sizing a battery bank or your electric needs, over estimating can cost lots of money.

how many ampshours per day, how many days in between charging, 50% usable battery amphours....... it adds up

roach711 05-12-2016 10:16 PM

Replace all your incandescent light bulbs with LEDs and you'll drop your lighting wattage by about four fifths. One of our lights went from 11 watts with an incandescent bulb to 1 watt with an LED bulb.

tincaneasybakeoven 05-13-2016 12:41 AM

we did that in the house, complete led change over and saved 20.00 on the first months bill. the 3 month the sent out the inspectors to check if we were stealing power. we wern't a lot of toe digging in the dirt and um and ahing until i spilled the beans about led lights. i can run 1 but may be up to 5 total 60 watt eq. led (8 watts actual use) off of a 75 watt power inverter for auto computer charger (single 120 outlet) radio shack.

Azuleslight 05-13-2016 04:17 AM

So from the research ive done it depends. If you have a newer LED tv it could run on 70 watts active and 1-5 watts on standby. If your lights are all led, they would draw minimal power, the pump fans and radio will be minimal as well. As you plan to run the freezer off lp you could get away with 2 6v batteries that have about 250+amp hours easily. You never want to go below 50% power on batteries. From the research ive done it has negative effects if you do. The main thing i want to point out is to plan ahead. You DO NOT want to intermix battery banks or add new batteries to banks that are already in operation. The old batteries will damage the new batteries.

The best bet however is to grab a kill o watt measuring meter and with shore power measure out your usage and from there plan your bank and know your needs.

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