Jumping a car with an RV battery? - Page 1
Forum section: electronics / general

author: antman_430
author_rank: Newbie
timestamp: June 25, 2021, 06:31:05 pm
content: So my father was a commercial electrician through the 1970’s-2000’s in New York City and always had unique solutions to electrical problems around the house. Sadly, he passed away well before I got my degree in physics and would’ve been able to better appreciate/understand what he was doing. There was one time in particular that leaves me stumped to this day and I was hoping someone could help me put together the pieces to make sense of it.I was about 10 years old and our truck battery died while a friend was letting us stay in their log cabin. It was pretty remote, so nobody else was around with a car, but the friend had a small pop-up camper in their driveway with its own battery. I’m not sure what other tools my dad had available to him beyond a set of jumper cables and basic workshop tools. We also would’ve had the log cabin that was being powered by the electrical grid, but I don’t particularly remember my father going into the house itself while try to do this. It’s definitely possible that he did though, so I don’t necessarily want to write that off as a possibility.Obviously this isn’t enough information for you to reconstruct what exactly he *may* have done to jump this battery, so I guess the better question is: Given these supplies (rv battery and jumper cables), how would you go about jumping this car battery? And, in the case that these supplies are insufficient, what additional supplies would you need (short of another running car) to actually jump the battery?Thanks!

author: Manul
author_rank: Super Contributor
timestamp: June 25, 2021, 10:11:23 pm
content: Quote from: antman_430 on June 25, 2021, 06:31:05 pmQuote from: antman_430 on June 25, 2021, 06:31:05 pmSo was there another battery available? If yes, then where is the mystery? Your father just connected it to the dead one using cables. If conditions are good (warm weather, engine healthy), the battery does not need to be fully charged or very powerful to start a car. I guess he just waited a minute or two for car battery to charge a little and the car started.

author: ledtester
author_rank: Super Contributor
timestamp: June 25, 2021, 11:37:21 pm
content: Electroboom -Jump Start a Car with AA Batterieshttps://youtu.be/I0utNemFsl8Another successful start...vuaeco -Can you jump start a car with AA 1.5V alkaline batteries?https://youtu.be/WSP_SoLoIYg?t=8m27sHis first attempt to start a V6 engine was unsuccessful, but he was able to start a smaller engine.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: June 26, 2021, 03:13:30 am
content: Quote from: antman_430 on June 25, 2021, 06:31:05 pmHi Antman_430, welcome to the forum. The RV battery was used to jump the car, given your evidence. In good conditions and with a good engine, the needed boost to start an engine can be minimal. However, under bad conditions, it may not have worked. Murphy was on holiday that day.I once started a vehicle with a dead battery using a welder. The welder is capable of outputting many amps, however, the working voltage was 36 volts, but was dropped over the welding rod, therefore did not damage anything. This was back in the 1970s, so there were no electronics to fry. This is not recommended on newer vehicles.With a degree in physics, depending on your specialty, this is a simple problem. However, if you did not study electrical theory at all and have no experience, this can be perplexing. A vehicle in good condition and a battery that is run down enough to not turn the engine over is a problem because the starter motor can pull up to 200 amps to rotate the engine on a larger engine, such as a V8 diesel, but on the other hand, on a 4 cylinder gas engine can pull as little as 50 amps. If the engine is in good shape and starts easy, the engine does not have to turn but small amount to start.Hope this helps...

author: bdunham7
author_rank: Super Contributor
timestamp: June 26, 2021, 03:26:03 am
content: A typical RV or marine battery isn't all that different from a car battery, although they are optimized for deep discharge and starting/rapid charging respectively. If they are physically similar, you could interchange them and probably not notice any difference for a while. Provided the RV battery was a standard 12V deep discharge, or 2 6V deep discharge in series--the two most common setups--jumping a car would be done the same as if you were using another vehicle.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 28, 2021, 02:47:36 am
content: Quote from: antman_430 on June 25, 2021, 06:31:05 pmI guess when you say "truck" you don't mean a hulking great Mack, but more like a "pickup truck" (what we would call a "ute" in Oz) or light flat tray truck.I make this point, because big trucks use 24v electrical systems so would be incompatible with a normal 12v RV battery, but the other, smaller, ones use 12v systems.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 28, 2021, 03:08:58 am
content: Some RVs, most notably ones with air conditioning, use 24V to get the current down to a more manageable level. Nowadays, some RVs even use 48V batteries. Those can still jump start 12V vehicles by tapping off a portion of the batteries, at the cost of getting them a little out of balance.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 28, 2021, 03:17:39 am
content: Quote from: NiHaoMike on June 28, 2021, 03:08:58 amIt is a bit hard translating from US pickup truck owner talk, as so many call a pickup a "truck", whereas anAustralian would definitely distinguish the two.My initial response was maybe the reverse to what happened, if RVs use 24 or 48v batteries.

author: james_s
author_rank: Super Contributor
timestamp: June 28, 2021, 03:50:37 am
content: The vast majority of RVs, at least old RVs use 12V. I think it's safe to say that the trailer had a 12V deep cycle house battery and this was used to jumpstart the truck. This is all pretty straightforward, a deep cycle battery would not last long being used frequently to start a truck but it will certainly work. I've jump started a car with a small 12V SLA battery, virtually any lead-acid battery can deliver an enormous current although it will greatly reduce the life of those not designed to tolerate it.

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 28, 2021, 03:54:58 am
content: Campers usually contain a 12 volt lead acid battery to power the lights, propane furnace, etc. Simple matter of yanking it out, lugging it over to the dead vehicle and hooking up the jumper cables. Even if it was a deep cycle type and not dual purpose or a car battery (cheaper as there's less lead in them) there'd likely be enough current to do the job if the truck battery wasn't totally dead, especially in summer.Sometimes you see something similar done at garages, a sort of super jump pack made from an especially large salvaged car/truck battery strapped to a hand truck, with a pair of heavy gauge jumper cables hanging off it.