I need some advice re: my idea for a super simple electrical system. I have a Transit Connect. I’ve built a platform bed with storage underneath yada yada yada. My girlfriend and I plan to travel around the Western US in the van off and on, probably spending at most one month at a time traveling/living in the van.
Electrical needs. We would like to power:
a single 30 ft strand of led christmas lights
a small fan to help with ventilation at night
it would be cool to be able to charge up a laptop occasionally so we’d be able to watch movies a few times a week while on the road.
That’s it! We really don’t need much in the way of electricity. SO my question is!: Can I simply buy a quality deep cycle battery of some sort, charge it up on my trickle charger at home, then bring it with us and simply run the sucker dry during the trip? Any reason this won’t work? Most trips in the van will be long weekends, a fair amount will be a week or two weeks, and occasionally we will travel for a whole month. I assume I will need an inverter as well. Is this a great idea or a terrible idea? Why?
This likely won’t work, maybe for a day or two dependent on the size of the battery. If the battery is non lithium you can only pull 50% capacity before you damage it and for lithium I’m under the impression you shouldn’t go below 20%.
For instance a maxxair fan pulls about ~1amp on setting 5/10. This would draw down a 100hr battery in 50 hours due to only having a usable capacity of 50%. A laptop is ~4amps and your usb won’t charge that without it being one of the new usb ports and even then they only provide 2.1 amps, so you are just keeping up with what you are using most time.
I would look at a ipad or tablet for tv as they are less power hungry and generally last longer on a charge. At least ours does. You could always just add an isolaetor for the longer trips if you will be driving or you could look into a solar briefcase which should be plug and play for charging.
There is no sense in buying a quality battery just to treat it like poop. The price on those add up really quickly and replacing a single one is probably more expensive than adding an isolator from the start. If it’s a lithium it would be more expensive than just adding the solar itself.
Get an AGM battery and mount it as close as possible to the front of the van and run heavy-duty cables (4 to 6 gauge at least - might be able to cannibalize a set of jumper cables), positive and negative (install a fuse at both ends close to the batteries) between the van starter battery and AGM. Install a quick disconnect such as an Anderson 100 amp connector in a place where it’s convenient to disconnect it when you’re camped (so you don’t run down the starter battery while camped), or you can get a battery disconnect switch. Don’t forget to disconnect it when the van isn’t running, and don’t forget to connect it when you’re driving. The battery will charge while you drive (as long as you don’t forget to connect it). A fancy option to automatically connect and disconnect is install a battery isolator.
Here’s a wire gauge chart. Don’t forget to place heavy duty fuses inline with the positive lead at both ends, near both batteries. The fuses should never be higher rated than the wire that you use, for example if the wire can carry 50 amps, don’t use 100 amp fuses because the wire will get hot and possibly start a fire before the fuses blow. Depending on what you get, charging the AGM from the alternator can draw 100 amps or more, so build it accordingly.
@Axel - Where do you get the numbers for an AGM pulling a possible 100 amps from the alternator? Everything I’ve read says the current (amps) is 30% of the total output. So for a 100ah battery that’s 30amps, if I am doing the math right? What is interesting, is even lithiums are not recommended to be charged at more that 30% to extend battery life. I pulled this from here so I could be interpreting it wrong. Perhaps that is recommended.
My battery doctor isolator, sometimes when my batteries are severely drained will throw an overcharge current light and I need to essentially reset it to charge the batteries. There is little info in the manual as to what that is, but I gather that maybe it is trying to pull too big of a charge and the battery doctor shuts down to prevent that. e.g. it’s rated for 150amps but sees 190amps?
How do you know the battery bank is only 100 amps - could be more. And the recommendation for heavy gauge wire is sound in terms of minimizing voltage drop between the alternator/starter battery and house battery. If the wire gage is too small the AGM won’t get a full charge due to voltage drop.
Sorry, what I meant was the way I understand it unless you have a lithium battery, anything else could only pull in 20-30 amps at most. Unless you’re toting around a 400ah AGM, then you’d never be near 100amps.
My question was if I was wrong on the 30%?
Your recommendation on wire gauge is sound. I put in #2 marine grade wire for mine. I would say not get an AGM though, unless the starter battery is also an AGM. Mixing battery types as I understand it is also not the best thing to do.
