Road trip with solar panel between roof rack...

17052 Views 15 Replies 9 Participants Last post by MorganBrogan, Oct 31, 2014

eluo

Discussion Starter · Mar 7, 2013

Hello Forum! I'm planning a 8000+ miles cost to cost and back road trip this August. It is going to be Me, Wife and 2 preteen kids. I'm going to camp most of the nights and though about how I can make this trip as comfortable and convenient as I can for them. I had several ideas that came across my mind. One of them include mounting a 250 watt solar panel between the roof rack of my 04. I searched around the internet and didn't find any Sienna owner posting about mods with solar panel so I'm starting one here.

Why solar panel??? I was thinking that I can run a chest freezer and bring frozen food to the camp sites. I'm not sure if I will proceed. If I do, I will only need to get a few parts and the rest, I already have.

Parts:

250 watt solar panel - ~$400 Amazon
Solar MPPT Charge controller - ~$100 Amazon
12v Batteries - I have 4, 12v, 75ah but 2 is probably sufficient for my needs
Inverter - I have a Xantrex 1000W sine inverter
Cables - I have 50' roll of 4 gauge cable.
Chest Freezer - I have a 5 cf Kenmore. It may take up too much space. Considering the following smaller ones
- Danby 3.6 cf - ~$200
- Avanti 2.1 cf - ~$200
- Whynter 65 Quart - ~$500
- ARB 63 Quart (splurge ~$900)
Small Microwave - ~$100
Fan-Tastic Vent - Not sure of the cost and not sure if I want to punch a hole on the roof of my Sienna.

So my question to you Forum is, will this work? One issues that I can think of is charging the battery in the heat when parked under the sun. That is why I consider the vent fan. But I'm not sure if I can install that vent fan on the roof of the Sienna.

My other option is to wire the inverted to car's battery and run the chest freezer when driving. My concern is that there will be periods of time where I won't drive much for 2 to 3 days. Will stuff stay frozen in a unpowered chest freezer for 3 days in a sun heated car?

My other, other option is to run off 2 (or 4) of the 75 ah batteries that I have and charge those battery when driving. But is it safe to run a chest freezer off batteries in the heat of a closed car (probably up to ~115°f)?

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assc

· #7 · Mar 11, 2013

What kind of ridiculous unit is "amp-hour/day"? Use watts and make things much easier to understand.

I assume that usage is at 12 volts? If so, then 36.7 amp-hour/day * 12 V = 18.35 watts, which obviously is not a problem for a 250w solar panel, even if you can only run it part of the day (I think derating to 1/3 is reasonable).

And your second number of 78 amp-hour/day works out to 39 watts, which is also reasonable.

What is not reasonable is thinking that a chest freezer will work - at all - in the oven that is an enclosed car in summer. A car in summer can easily hit 140 degrees, and 180 is not unheard of. I doubt the freezer will work at temperatures like that.

To run your 78 amp-hour/day freezer, you'll need a battery with an RC of 125 http://www.wolframalpha.com/input/?i=78+amp-hour%2Fday+%2F+(25+A+*+1+minute)+*+16+Hour

I would double the RC to avoid draining the battery all the way, and make sure to use a deep cycle one. Also, avoid making yourself crazy, and use only a single battery and keep in mind that you won't be able to use the solar panel every day, so maybe triple it.

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assc

· #9 · Mar 12, 2013

eluo said:
0.87 amps per hour

BTW, It's not amps per hour (that doesn't mean anything useful). The power draw is simply 0.87 Amps. No per hour. An Amp is a continuous unit of measure. Watts is the same way. It's not Watts per hour, it's just Watts. 0.87 A at 12 V is 10.44 Watts.

If you multiply Watts and time, you get units like KwH - this is TOTAL energy, and does not specify draw, but how much energy exists in total - you can use that energy fast or slow KhW does not say.

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