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Old 06-12-2021, 05:45 PM   #1
Mini-Skoolie
 
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Scrutinize my Wiring Diagram!! (Newbie)

Hey all, been working really hard for 2 years on my bus conversion and I’m finally almost ready to hit the road!! I just need a quick check on my overall wiring concept. I also have a few basic questions regarding how this will all operate together.

————THE COMPONENTS:————

I am planning to have a 500AH 12v Battery bank composed of 4 6V Trojan T- 105 Batteries wired for 12v.

I will have two battery charging options. One will be a Sterling 120A B2B charger hooked between my starter batteries and house batteries which will be powered by a 500A alternator I recently installed on the bus.

As I understand it, the B2B hooks directly to each battery bank and has its own fuse, so it does not need to be hooked up to anything else.

The other charging option will be a Champion 3500 Running Watt Generator which has a 120V 30A shore power output. The generator will be run via that outlet to a 30A GoPower Automatic Transfer switch, and then to an Iota DLS75 12V 75A 4-stage battery charger, which will then be hooked to the battery bank.

The battery bank will be run to a 350A Fuse and then to an SL Euthion 3000w Inverter, which will be wired back to the ATS.

The ATS will of course then be wired to the 120V Breaker Box and the 120v outlets are hooked into the system from there.

The 100A 12 port DC fuse box will be wired from the battery bank with a 120A fuse.

I’ve attached a wiring diagram I found that matches my system fairly well, though I scribbled out the solar system, as I will not be using solar.

I feel fairly confident that this is a good setup for my needs, it just never hurts to have another pair of eyes scrutinize your concept.

—————-QUESTIONS:—————

1. How long will a 30A 120v shore power plug take to fully recharge my 500AH battery bank at 50% discharge?

2. Approximately how long will the 120A B2B take to do the same?

3. Is the 120A B2B too powerful for this setup, or is it irrelevant that it is a bit oversized?

4. Is the ATS correctly sized at 30A?


I’m also a bit confused about how the ATS operates.

Let’s say I have the generator running all day for about 6 hours, and there is a light AC load say about 800w at 10A.

The ATS detects generator power when it is on. It uses the generator power to power the load and then uses the remainder of the available power to re-charge the batteries if necessary, correct?


I appreciate any advice someone with more experience in the electrical field may have to offer! It’s been an interesting process for me thus far learning all I can. I’m very interested to hear what you all have to say.

Thanks!! I can’t wait to get on the road!!
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Old 06-21-2021, 09:54 AM   #2
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Quote:
Originally Posted by silvermachine View Post
1. How long will a 30A 120v shore power plug take to fully recharge my 500AH battery bank at 50% discharge?
500AH / 30A = 16 hours. 50% DoD, 8 hours.

Quote:
Originally Posted by silvermachine View Post
2. Approximately how long will the 120A B2B take to do the same?
500AH / 120A = A little over 4 hours. 50% DoD, a little over 2 hours.

Quote:
Originally Posted by silvermachine View Post
3. Is the 120A B2B too powerful for this setup, or is it irrelevant that it is a bit oversized?
120A / 500AH puts you at .25C. Look at your battery manufacturer's ratings for charge- but I'm pretty sure this is OK. Would make for a nice quick charge setup.

Quote:
Originally Posted by silvermachine View Post
4. Is the ATS correctly sized at 30A?
Since you're doing 120V service only (and not 240V), I think so, as it will match with a 30A RV inlet.

Quote:
Originally Posted by silvermachine View Post
I’m also a bit confused about how the ATS operates.
Okay, lets see here.

Quote:
Originally Posted by silvermachine View Post
Let’s say I have the generator running all day for about 6 hours, and there is a light AC load say about 800w at 10A.
Not sure I'd call that a "light AC load" if running continuous, that's like a small microwave. 800W will empty your batteries in a little over 3 hours.

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Originally Posted by silvermachine View Post
The ATS detects generator power when it is on. It uses the generator power to power the load and then uses the remainder of the available power to re-charge the batteries if necessary, correct?
Not quite. Your diagram is missing something- you currently have your "smart battery charger" connected to the ATS, I don't recommend making the split here... I think you should have a small DIN Rail breaker box before the ATS... one breaker should be 15A to power an outlet for the smart battery charger. Another breaker should be sized 30A, feeding both the 15A breaker to your charger and the ATS.

Also consider a surge protection device wired in just after the RV inlet.

How the ATS works... it takes two inputs, A and B. If A is present it passes A along to Output. If A is not present (you are not plugged in), B is passed along to output. There's usually a manual override of some kind. I assume A would be your RV shore inlet and B would be the inverter. Output would go to your 120V breaker box.

I cannot stress enough that without solar your battery runtimes will be _extremely_ limited. If you can afford anything north of 100W, do it, on a sunny day a modest set of panels can double or triple your runtime.
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Old 06-21-2021, 10:37 AM   #3
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I agree re: adding a bit of solar, but I would also strongly consider 24v to cut all your wire and fuse sizes in half and to have less voltage drop.

Not sure how that works with the alternator charging so it may not be worth it but if they make a 12vdc -> 24vdc charger I would look into it. It’s hard to describe how much better 24v is. We’re all conditioned to default to 12v but there’s almost no reason to consider it (unless that b2b charger concept doesn’t work with 24v)
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Old 06-21-2021, 10:41 AM   #4
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We’re all conditioned to default to 12v but there’s almost no reason to consider it (unless that b2b charger concept doesn’t work with 24v)
Depends on the system/use case. In this case I'd have to know more about the loads.


Certainly, a lot more people should be taking 24V seriously.
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Old 07-08-2021, 07:02 AM   #5
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Quote:
Originally Posted by kazetsukai View Post
Depends on the system/use case. In this case I'd have to know more about the loads.


Certainly, a lot more people should be taking 24V seriously.
Because of less loss?

Your points are insanely informative, btw.

Thank you for all you contribute.
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Old 07-08-2021, 10:18 AM   #6
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Because of less loss?
Less loss, cheaper components. 24V halves your amperage requirements all around, so for instance...

If you have 1200W of solar panels, a 12V system will need a solar charge controller capable of 100A. That's:
https://www.amazon.com/Victron-Smart.../dp/B07FCRZ3F6

Versus the same system, 1200W, with the same batteries rewired for 24V (assuming you can rewire them that way, like 12V batteries in pairs or 6V batteries in groups of four) you'd only need:
https://www.amazon.com/SmartSolar-MP.../dp/B073ZJ43L1

Which is less than half the cost for the same charging capabilities. Your inverter will also be more efficient only having to step down to 24V instead of 12V, you'll save money on smaller cabling, etc...'

12V makes sense up to a certain system size... smaller great. People with midsize should at least look at 24V, people with large systems ought to be looking at 48V.
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Old 07-08-2021, 11:02 AM   #7
Mini-Skoolie
 
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Quote:
Originally Posted by kazetsukai View Post
Less loss, cheaper components. 24V halves your amperage requirements all around, so for instance...

If you have 1200W of solar panels, a 12V system will need a solar charge controller capable of 100A. That's:
https://www.amazon.com/Victron-Smart.../dp/B07FCRZ3F6

Versus the same system, 1200W, with the same batteries rewired for 24V (assuming you can rewire them that way, like 12V batteries in pairs or 6V batteries in groups of four) you'd only need:
https://www.amazon.com/SmartSolar-MP.../dp/B073ZJ43L1

Which is less than half the cost for the same charging capabilities. Your inverter will also be more efficient only having to step down to 24V instead of 12V, you'll save money on smaller cabling, etc...'

12V makes sense up to a certain system size... smaller great. People with midsize should at least look at 24V, people with large systems ought to be looking at 48V.
Very good to know! Thank you for the detailed explanation!

I guess I should study the basics because I'm still not understanding. So, batteries in groups have to equal 24V to be ran as 24V and the total storage is dependent on the specific battery used?

Sorry to clutter this thread with something I should probably research or DM about.
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Old 07-08-2021, 11:04 AM   #8
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Very good to know! Thank you for the detailed explanation!

I guess I should study the basics because I'm still not understanding. So, batteries in groups have to equal 24V to be ran as 24V and the total storage is dependent on the specific battery used?

Sorry to clutter this thread with something I should probably research or DM about.
I don't quite understand your question. Feel free to PM me, we can even have a quick chat over the phone if you'd like.
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Old 07-08-2021, 11:06 AM   #9
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Different ways to wire four 12V batteries:
Click image for larger version

Name:	battery_configurations.jpg
Views:	6
Size:	113.9 KB
ID:	59219


All have the same energy capacity but different system voltages.
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Old 07-08-2021, 11:19 AM   #10
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I don't quite understand your question. Feel free to PM me, we can even have a quick chat over the phone if you'd like.
Absolutely will, thank you!

Quote:
Originally Posted by kazetsukai View Post
Different ways to wire four 12V batteries:
Attachment 59219


All have the same energy capacity but different system voltages.
Makes so much more sense now!
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