Ok first off the OP was looking for a cheap safe alternative. A second battery ,generator or solar panels I don't consider cheap. I was suggesting a cheap alternative to maintaining a charge in his battery to get him through his 4 day trip. Jumper cables are cheaper than batteries, heaters, generator etc. I wasn't suggesting they could completely charge his battery just maintain a reasonable charge. My TV is quieter than alot of generators I hear running at camp grounds ( not everyone spends the money for the quiet ones) and probably doesn't spew out any more carbon monoxide. Also the exhaust pipes is pointed away from the camper. I consider it safer then having a heater not vented to the outside in the PUP.