battery charging basics

Is this 48w travel fridge a 120v dorm type fridge?
I have one in my TT and it draws about 80w at a 1:5 duty cycle at about 80f ambient. Also, the locked rotor draw at startup is significant. It was necessary for me to go to a 1000w inverter to handle the startup draw. I haven't done any exact daily amp hour measurements but I have my solar system at 235w module with 320 AH of capacity.
A possible better solution, if you wish to travel without a generator would be to find a cheap camp site that offers electrical and pull your power off the pedestal.
IMO, a single battery and 100w of solar is not going to cut it.

If you discharge one of those marine/starter batteries continually until it is discharged (probable in your use), it won;t last a month. If you want to have electric devices running every day, you'll need to have more battery capacity and if you want to charge those batteries with no generator, you'll need more solar output.

westend wrote:
Is this 48w travel fridge a 120v dorm type fridge?
I have one in my TT and it draws about 80w at a 1:5 duty cycle at about 80f ambient. Also, the locked rotor draw at startup is significant. It was necessary for me to go to a 1000w inverter to handle the startup draw. I haven't done any exact daily amp hour measurements but I have my solar system at 235w module with 320 AH of capacity.
A possible better solution, if you wish to travel without a generator would be to find a cheap camp site that offers electrical and pull your power off the pedestal.
IMO, a single battery and 100w of solar is not going to cut it.

If you discharge one of those marine/starter batteries continually until it is discharged (probable in your use), it won;t last a month. If you want to have electric devices running every day, you'll need to have more battery capacity and if you want to charge those batteries with no generator, you'll need more solar output.

really, not last a month! car batteries usually come with a 1 or 2 year warranty, what would happen if i take it back to sears or wallmart every month?

how successful is your solar setup, do you get enough sun to provide 235W for 8 hours a day?

i'll be going from CA to NY from March to September so i should hit most of the sunny months but i'm guessing most camp sites are pretty shaded by trees

so i've been looking at batteries

is seems starter batteries cost about $2/AH
http://www.walmart.com/ip/Schumacher-Electric-SB121000-Schumacher-Electric-12V-100AH-Battery/25955634

and marine about $5/AH
http://www.walmart.com/ip/EverStart-Maxx-Group-Size-29-Marine-Battery/20531539
this one is size 29 which as far as i can tell is about 20AH

so starter batteries look like most bang for the buck, especially if you can get wallmart to replace it free

Forget the starter batteries; there's a reason the marine/deep cycle cost more. The starter batteries will discharge quickly in your intended use. The plates are thinner intentionally to allow a large rush of instant power to start a vehicle. Deep cycle batteries have thicker plates for long sustained draw.

http://www.walmart.com/ip/Schumacher-Electric-SB121000-Schumacher-Electric-12V-100AH-Battery/25955634


Schumacher is very expensive at $2 per amp/hr

http://www.walmart.com/ip/EverStart-Maxx-Group-Size-29-Marine-Battery/20531539

This group 29 at 120 amp/hrs is less than half the price and definitely a better value. Get 2 :B

I would go larger than 100w and keep it portable for such a trip.

If you will be in So CA (Norco) here is a 140w panel, $140.


http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/p2668/Solar-Cynergy-140-Watt-12-Volt-Solar-Panel/product_info.html

Morningstar 10a controller $45

Get 100' of MC4 cable and cut in half. MC4 connectors to the panel and the cut ends to the controller. This will allow you to position the panel into the sun.

Just some random thoughts, best of luck.

I have a 12v (Edgestar) refrigerator I keep in the back of my van. I plug into a power outlet go to a Group 34 AGM (Sears Platinum) battery and then to the refrigerator. I unplug from the power outlet at night to prevent any drain on the vehicle battery.
If I wanted to charge a trailer battery during the day while I was roaming around, I would make a little battery holder to slip into the receiver hitch and fix a 7-way connector with just 12v and ground wires to clip to the battery posts.
Prior to all the electronics, I used to start the tow vehicle and swap out the batteries while the alternator kept the engine running.

I dunno, do you want to spend a few hours every week removing, returning, and re installing batteries?
Starter batteries are not the answer. Costco or Sam's club sell 6v Golf Cart batteries for $90 a pop. Hooking two of them up to get 12v will give you 220 AH of capacity and you won't need to remove and return them.

You'll need to do some research on solar power:Jack and Dan Meyer You will only get 5hr. of maximum solar harvest per day. The rest of the time will be productive but less so during the day.

When designing the solar charging system, the most important thing to define is your usage. Your RV will use power for alarms and circuit boards, lights, pumps, fans, and, if you use an electric fridge, that will be the biggest power user. A $700 12v. Danfoss compressor fridge may use an average of 48 W but a standard dorm fridge will use more. My new dorm fridge uses an average of 40 AH/day if I leave the door closed. A 12V starter battery will be discharged below 50% state of charge in a day just from the draw of the fridge.

Let's see, five deep discharge cycles

Battery goes bad

200 miles to nearest Wal-Mart (maybe a lot more than that)

Gasoline is free! oh what the heck go for the starter battery. Four or five otter get you through this... Wal-Mart is not going to warrant them until they utterly fail. Enjoy your ten minutes of light per night.

Back in the 70's I used to DAMAGE group 27 starter batteries with 2 70% discharge cycles. My VAT 40 confirmed the CCA would drop from 480 CCA to 400 or a bit less. Could not be recovered. Interstate batteries. So the advice about using thick plates batteries isn't a bunch of hyperbole.