Anyone Know What These Wires Do?

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Anyone Know What These Wires Do?

July 11, 2021, 10:31:18 am

Greetings everyone!

Does anyone know where the two white wires connected to the 'BATT NEG' terminal go?

The diagram in the back of the owner's manual is helpful, and I have a decent grasp of the circuit, except for one of those white wires. I am pretty sure one of the white wires runs to the solar charge controller.

All this is for a backup lithium battery system, and I need to make sure I understand the entire electrical circuit.

Re: Anyone Know What These Wires Do?

Reply #1 – July 11, 2021, 01:41:25 pm

Does one white come off of the converter section?

Jon

Re: Anyone Know What These Wires Do?

Reply #2 – July 11, 2021, 02:25:24 pm

One goes to the converter and the other to a physical ground.
What is a "backup lithium battery system"? The wires pointed to are in most or all LDs.

Larry

Re: Anyone Know What These Wires Do?

Reply #3 – July 11, 2021, 04:05:13 pm

Thank you for the info.

I am using a couple of Tesla Model S battery modules as an emergency backup if shore power goes out. Risky operation - but with about five years of research under my belt, I'm ready to proceed.

The system has been operational for a little over a week now. It powers the coach with air conditioning for at least a few hours while the grid is down. I haven't had a chance to test exactly how long it can power the air conditioning, but it looks like 5-6 hours.

I had to separate the 12v circuit from the 120v circuit. Additionally, I needed to remove the 120v to 12v converter. Also, bypass the generator converter. So, no generator - but no need...I have plenty of power now. Additionally, I removed the alternator circuit from the 'OEM' house batteries, creating issues for the Tesla 24v battery inverter/charger while the truck was running.

Although the system is working now, it doesn't mean that it is correct. I think it is safe enough at this point, but it would be nice to get ahold of detailed wiring diagrams to verify a few things. I need to make sure the 12v circuit is separated from the 120v circuit, and no converter or charger is on the 120v circuit.

Re: Anyone Know What These Wires Do?

Reply #4 – July 11, 2021, 05:47:10 pm

Sound very interesting, let us know how well it works and more details, if possible.
The most detailed wiring schematic is the simple wiring diagram in the Owner's Manual.

Not having the generator connected or a converter installed leaves you vulnerable during extended power outages, what are your plans for these situations?
We look at our LD as our emergency home and escape pod, in case of fires and earthquakes.

Larry

Re: Anyone Know What These Wires Do?

Reply #5 – July 11, 2021, 07:38:31 pm

Quote from: jrsl1982 - July 11, 2021, 04:05:13 pm

I had to separate the 12v circuit from the 120v circuit. Additionally, I needed to remove the 120v to 12v converter. Also, bypass the generator converter. So, no generator - but no need...I have plenty of power now. Additionally, I removed the alternator circuit from the 'OEM' house batteries, creating issues for the Tesla 24v battery inverter/charger while the truck was running.

If your LD has the original wiring in place the 12V and 120V circuits are separate. The only connection between them is the house converter, which takes 120V to 12V. There is no separate "generator converter." The generator produces 120V and is connected to the house converter via the transfer switch . And of course the chassis alternator cannot charge a 24V battery system. I am really interested in how your project turns out. Keep us informed.

Charles

Re: Anyone Know What These Wires Do?

Reply #6 – July 12, 2021, 02:14:34 am

"no generator - but no need...I have plenty of power now."

So how do the Tesla modules get recharged when you're not driving and not plugged into shore power? Do you have a large solar array?

Re: Anyone Know What These Wires Do?

Reply #7 – July 12, 2021, 09:50:10 am

Currently I use the grid to charge the batteries, while the camper is hooked up to the grid.

I want to do AC coupled solar, but haven’t decided on what panels I am going to go with.

I think I’ll end up doing a YouTube video about how I have the system setup. It is interesting and too complicated to write about. Although, this wasn’t completely my idea. The folks over at evtv.me provided much of my education and parts.

Re: Anyone Know What These Wires Do?

Reply #8 – July 12, 2021, 11:58:43 am

Quote from: jrsl1982 - July 12, 2021, 09:50:10 am

I think I’ll end up doing a YouTube video about how I have the system setup. It is interesting and too complicated to write about. Although, this wasn’t completely my idea. The folks over at evtv.me provided much of my education and parts.

Too complicated to write about? We have electronic engineer members who just might understand.
This leaves us wondering what your project is about and how you expect it to work off-grid, which for many of us do most or all the time.
What's the benefit to the boondockers and dry campers, if any?
Will you be jumping from RV park to RV park, each time the battery needs recharging or looking for a Tesla charger?
I'm failing to see any advantage to this other than short-term, high power output...until the battery dies.

Big batteries are great...if you have a way to quickly recharge them.

Larry

Re: Anyone Know What These Wires Do?

Reply #9 – July 12, 2021, 11:59:05 pm

Okay, but recognize, I am an amateur. I am still learning. This is a hobby for me, so take what I am saying here with that in mind.

I am unsure what my project is about, but it already works off the grid and provides 10kw of power. I guess I did this because I am curious about solar power and the storage of energy. Plus, I want to run my TV, microwave, router, computer, and power outlets without running the generator.

This setup provides a decent amount of power compared to other battery options. When boondocking, I often find myself and electronics drained of energy with the AGM house batteries. With AGM, I have to be careful how much electricity I am using, as the two house batteries do not seem to last long enough to get through a few days of TV and computer usage. BattleBorn and some of the other lithium battery options are super expensive compared to used Telsa batteries. For the price of a 5kw Model S battery module, you can get a single 1kw Battleborn. That is a difference of 4kw. Also, let's face it, 10kw is the minimum for any off-grid power. The internet router, computer, and refrigerator alone use about 50watts. 20 hours and a 1kw battery become kaput. Let alone try to use the microwave or lights. 10kw battery will power those things for 200 hours. Not great, but not bad either. 10

Plus, there is no fun acquiring state-of-the-art technology that requires minimal installation or understanding of the chemistry to operate. That is where I get my kicks.

Anyways, when I start boondocking again in the winter, I'll know exactly how it benefits me, but now its role is a power backup in case the grid goes down. This way, I do not need to run the generator while still providing the same amount of power, albeit not for the same amount of time as the generator. The system kicks on immediately without any input from me when the grid goes down. If I am away from the camper in the summer and the grid goes down, there is no power interruption. Essential for my doggy.

Sure, automatic generator switches will crank the generator if a power loss is detected, but that still requires the use of the generator. Maintenance is expensive on a generator. I prefer not to spend time with gas, oil, or any combustible engine at this point. They are too messy, dirty, and to me, not worth it. Currently, my generator is not attached to any electrical circuit in the RV, as it is not compatible with the inverter/charger. The inverter/charger has become the focal point of my LD electrical system. This change to the electrical system enables AC coupling.

This concept uses grid-tied solar inverters to provide AC power off the panel, opposed to DC direct to the battery. AC power off the panels rather than DC power is beneficial for several reasons, including not having a single inverter invert the solar energy to AC power, rather multiple inverters doing the work. Results in more efficiency. A more important benefit is the ability to be grid-interactive, so if you need to hook up to the grid, it is plug and play. Any excess power generated by the panels that cant be used by the loads or put into the batteries gets fed back into the grid, regardless if there is a bi-directional meter or not.

In the future, I want to have a single power outlet from the generator, utterly separate from all other electrical systems. This way, when the batteries get drained, and I have no shore power...I have the generator option.

So, I start by replacing the generator with something more clean, quiet, and with less maintenance. Generator maintenance is costly and can be a big mess. I am very sick of using combustible engines for small applications, such as running an air conditioner or TV.

The inverter/charger charges the Model S batteries at a rate of 120amps- plenty fast enough for me.

Re: Anyone Know What These Wires Do?

Reply #10 – July 13, 2021, 09:59:46 am

Thanks for the explanation, Joe. I hope it doesn't seem as if we're grilling you; it's just that your planned usage is somewhat unclear.

"I start by replacing the generator with something more clean, quiet, and with less maintenance."

OK, but the two are not comparable. To use an internal-combustion analogy, you're replacing an engine with a fuel tank. A battery isn't a power source; it's just a way to store power that was generated elsewhere. The question is: where is the power coming from to recharge your 10 kW-hour battery bank? (That 10 kW-hour number assumes a used Tesla module still stores as much energy as a new one, which is open to question.) It's going to take a lot of solar panels and/or a long time to replenish such a large battery bank. What's the size of your planned solar array?

"let's face it, 10kw is the minimum for any off-grid power... 20 hours and a 1kw battery become kaput."

That's only true if you're not recharging it in the meantime, as these numbers seem to assume. But nobody I know lives that way. If you have an adequate solar array, then the issue of how much battery capacity you need boils down to 1) how much is needed overnight, and 2) how much is needed to get through a few cloudy days. From my full-timing experience and that of others here, 300-400 Ah of LiFePO4 batteries (3-4 kWh of usable power) plus 500-600 W of solar panels is plenty.

Re: Anyone Know What These Wires Do?

Reply #11 – July 13, 2021, 12:45:11 pm

Well, I'm baffled about how this system works in the real world.
To recharge the Tesla battery is going to take a trailer full of solar panels, not sure what other source of power is going to be used other than shore power.
Now Jeep is proposing installing battery chargers in the backwoods for electric Jeeps, maybe it will be a new source of RV power. Still wondering.

Larry

Re: Anyone Know What These Wires Do?

Reply #12 – July 13, 2021, 01:29:51 pm

I'm curious. Is this the Tesla S Lithium Ion Battery Module ? Where do you have these modules located? Are they connected in series or parallel? What BMS system are you using?

Charles

Re: Anyone Know What These Wires Do?

Reply #13 – July 13, 2021, 05:27:58 pm

Quote from: Charles & Donna - July 13, 2021, 01:29:51 pm

I'm curious. Is this the Tesla S Lithium Ion Battery Module ? Where do you have these modules located? Are they connected in series or parallel? What BMS system are you using?

That is the one...although very expensive on that website. Check eBay for better prices. I use the existing Tesla BMS on the module with the EVTV v2 monitor. My current setup is 2 batteries in parallel, 24v - located in the space above the truck cab. I plan to move somewhere else in the coach, but not sure where yet.

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