Lithium battery, wiring help

[schenier]

Hello,

My fantastic husband is building our teardrop and I have fallen short in my task to attempt to figure out the electric side of things.

Our needs: Cpap machine, fan, one interior light, one outside light on each side of the teardrop, one light in the kitchen galley. Run a small ceramic heater for a few hours. I'm not blow drying my hair or bringing a blender. No radio, etc...

We don't plan on camping many places with shore power. Mostly 1-2 nights off grid and occasionally longer. I'd like to find a lithium ion battery system that would fit this bill, I'm thinking around 50Ah would be sufficient, am I way off? On that note, we will be using this teardrop for ski trips so heating is an issue I have been trying to think through. I don't think it will take too much as there will be 3 bodies inside. We live in New Mexico, but it does get quite cold in the mountains. Any advice on this front would be appreciated.

Id like to be able to charge the lithium battery (or batteries) while towing and also be able to plug into 110 if we are at a developed site. Solar is something I'd look into in the future, but with everything else on the build right now it may need to wait a few months.

I need a wiring diagram for someone who has never, ever done electric before. I can push the button on the GFI or flip a fuse, that's all. Please help me.

[Shadow Catcher]

OK plan on more than you think you need! More lights use LED, more outlets 12V and 120AC, cell phone chargers (can be 12V) laptop, what ever else. It is amazing how they gang up on you.Does your CPAP run on DC if not then you will need an inverter.
Anything using resistance heat is a no no, the small ceramic heaters draw a LOT of current. If you have 120AC it is another matter.

You will need a converter set for your Lithium battery my suggestion is a Progressive Dynamics https://www.progressivedyn.com/lithium_battery_charger.html

[schenier]

Looking into this a little more, I am thinking of using a little buddy heater and mounting a C02 detector in there as well and we will have the fan...Still freaks me out.

I'm thinking of going with the wiring diagram in this thread http://tnttt.com/viewtopic.php?t=1941&p ... c&start=90

If I am to understand this correctly, the master switch switches between shore power or battery. I am really confused about needing an inveter or converter from shore power going to 12v. Any tutorials on this? Is anyone able to provide links for the actual hardware for the converter (or inverter?), 40 Amp circuit breaker, and ground block? Also, why are there more switches on the shore power for the lights and fans?

The Cpap is currently powered thusly while camping: Husband stripped the wires and plugs them directly into a lithium power pack designed for jump starting a car, gets about 7 hours of use...Looking at this diagram I am thinking he would be able to get the 12V adapter for the machine and use it off the battery?

[schenier]

Shadow Catcher, thanks for the link for the converter, looking into it.

[MtnDon]

Maybe some definitions will help sort things....

Converter: the input power is 120 VAC and the output is DC, normally 12 VDC for our purposes. Some converters, like the PD are battery chargers as well as a power supply to produce 12 VDC from a 120 VAC connection.

Inverter: the input is 12 VDC (if the battery is a 12 volt) and the output is 120 VAC

[MtnDon]

The master switch as drawn in that wiring diagram is sort of redundant. One end connects to the + battery terminal and the other end to 9a) the converter / charger AND to a circuit breaker. Some circuit breakers can be used as a switch. Using a breaker like this from Midnight Solarwould eliminate the need for the switch. It comes in many sizes and can be simple to mount with a section of DIn rail. There are other brands available as well. marine dealers sell some. As drawn that master switch has nothing to do with selecting between shore power and battery. It is a disconnect between the battery + and the balance of the DC distribution system. Nothing to do with AC directly.

[MtnDon]

As pictured everything below the master switch is DC, not directly associated with shore power with the exception of the two outlets on the far right side. (marked 120n VAC). As drawn the only shore power is at the very top and right side and is connected with three colored (red, black,green) wires. BTW the choice of red, black and green for the 120 VAC is a poor one. The AC neutral should never be black as drawn. Never. That would get an electrician confused as neutral AC should be white or grey in the USA or Canada.

The PD converter/charger that was linked to would be a good choice for an LFP type of lithium battery. There are a couple major groups of lithium batteries and their voltages are different. With that PD unit you need an LFP, Lithium Ferrous Phosphate type not any of the other ones. All that is pointed out in the link. It is important. LFP are nice batteries though $$$. Have you selected any particular brand?

[MtnDon]

The Cpap is currently powered thusly while camping: Husband stripped the wires and plugs them directly into a lithium power pack designed for jump starting a car, gets about 7 hours of use...Looking at this diagram I am thinking he would be able to get the 12V adapter for the machine and use it off the battery?

So how many amp-hours is that power pack that gives 7 hours? That will help select a proper sized battery.

[schenier]

As pictured everything below the master switch is DC, not directly associated with shore power with the exception of the two outlets on the far right side. (marked 120n VAC). As drawn the only shore power is at the very top and right side and is connected with three colored (red, black,green) wires. BTW the choice of red, black and green for the 120 VAC is a poor one. The AC neutral should never be black as drawn. Never. That would get an electrician confused as neutral AC should be white or grey in the USA or Canada.

The PD converter/charger that was linked to would be a good choice for an LFP type of lithium battery. There are a couple major groups of lithium batteries and their voltages are different. With that PD unit you need an LFP, Lithium Ferrous Phosphate type not any of the other ones. All that is pointed out in the link. It is important. LFP are nice batteries though $$$. Have you selected any particular brand?

This is the battery I have been looking at http://elitepowersolutions.com/products ... ucts_id=90
The power pack we have currently is 10 Ah, so getting 40Ah should get us through 2 days/nights with the added load of lights and a fan.

After studying the diagram again I realized the error of my thought with the master switch.

[MtnDon]

Ok, that is the battery. Are you buying the BMS separately? Using LFP w/o cell balancers can be risky to cell longevity. It can be done but requires care.

[schenier]

Ok, that is the battery. Are you buying the BMS separately? Using LFP w/o cell balancers can be risky to cell longevity. It can be done but requires care.

Yes, the BMS is separate. Still going through all the literature on that.

[OverTheTopCargoTrailer]

http://elitepowersolutions.com/products/product_info.php?cPath=42&products_id=152

I would say buy their 60 AH battery.....
if you want bms....use 4 of the above items..at $8.95 each

Good luck

OTTCT

http://overthetopcargotrailer.blogspot.com/