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Can I wire AC-DC Charger to bus bar instead of direct to battery?

TommyinMiami

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Apr 2, 2022
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Hi guys, brand new here, long-time lurker. I am building a DIY gen and had a quick question. I am trying to keep my install cabinet as clean and simple as possible.

I am wiring up an AC-DC 10amp NOCO charger to the system for when the unit is in storage. Can I wire this directly to the fused pos and neg bus bars instead of wiring it directly to the battery terminals with inline fuses?

It's only a 10amp charger, 15Amp fuse. Nothing will be used when this is charging. No panels attached, no loads, nothing to confuse the charger.
Thank you for any help, advice, or suggestions

Usage: Only as battery backup for hurricanes (Miami), no grid tie-in, Prepper purposes, occasional use working on the boat and needing AC tools.
Everything is tinned copper because I live next to the ocean and will occasionally use it on the boat.

System:
Cabinet - Bottom half of Home Depot Husky Rolling Tool Chest after draws removed
GoWise 3,000/6,000 Watt Pure Sine Inverter (300A MEGA fuse)
Renogy 40Amp Charge Controller (40A & 30A ATC fuses)
Renogy 40Amp DC-DC Charger (50A & 60A ANL fuses)
2 direct pos neg attachment points to connect to car alternator to DC-DC charger for emergency backup charging
Renogy Battery Monitor and 500Amp Shunt
Renogy Bluetooth module
45A Anderson Power pole hookup, 1 30A Power Pole connection
6 waterproof AC outlets
1 High Amp AC outlet
1 500A Total System On/Off disconnect switch (for everything except inverter)
1 125A Blue Sea Marine 12 circuit fuse pannel with neg bus
2 ACguys variable power, 120mm cooling fans
1 ACguys Thermostat fan controller
1 NOCO LiFePo4 10Amp AC-DC Charger (15A ATC fuses)
1 NOCO AC passthrough connector to attach AC power to NOCO AC-DC charger
6 USB Chargers 3 USB-C Chargers, 2 12-volt outlet connections
4 soft white 3,000k 12 volt lights to provide ambient room lighting
4 100watt 12v Rich Solar panels
1 Weize 100Ah 12v LiFePo4 battery (planning to add 3 more in the future to have 400Ah total.
2/0 Battery to inverter wires 24" length and 2/0 Battery to Battery wires. 12" length
and Finally, 1 12v rope lighting inside the cabinet for "cool factor" and I guess to see components while working on them.

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Nothing will be used when this is charging. No panels attached, no loads, nothing to confuse the charger.
That should work just fine as long as there isn't something else we need to know about between the bus bar and the battery.
Even using your system, drawing power from the bus bars should not be a problem if your wiring is adequate. There is nothing unusual about what you propose.
 
What size wire do you have between the batteries and the inverter? You need 4/0AWG to handle the 300A load you could have with a 3000W inverter on a 12V system. The wire in the picture looks too small to be 4/0AWG. And since you need a 400A fuse to go with that wire, make sure your bus bars are rated for at least 450A or more.
 
What size wire do you have between the batteries and the inverter? You need 4/0AWG to handle the 300A load you could have with a 3000W inverter on a 12V system. The wire in the picture looks too small to be 4/0AWG. And since you need a 400A fuse to go with that wire, make sure your bus bars are rated for at least 450A or more.
Haha good eye. Yes the wire dangling from the inverter is the crap wire it came with. Its just there now for measuring purposes. These are the wires I am using. I got 2/0 because I have no plan to every actually use 3,000 watts. I only got this 3,000 watt inverter because some reviews said that the inverter alarm would go off on the 2,000 watt version at only 1,500 watts so I bought the 3k to ensure no issues with start up amps of a fridge. 2/0 was the max size my crimper could crimp. If you think I still should go to 4/0 ga then I guess I could just crimp them at West Marine though, they have a 4/0 crimper there. (Blue tape is just holding the connectors on temp until I crimp them)
 

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I got 2/0 because I have no plan to every actually use 3,000 watts.
It's not ideal to wire for what you think you will use versus what is actually available. You might forget it's only wired for 2000W instead of 3000W. Or maybe someone else tries to use it and doesn't know.

If you keep the 2/0AWG then I would use a 250A fuse. This way if you attempt to use the full 3000W (or anything over 2000W) then the fuse will properly protect the wire.

Why not double up on the 2/0 wires? Run 2 of them that is.
If it's wired with 2 pairs of 2/0AWG wires then each individual wire needs its own fuse. Don't use one 400A fuse, use two 200A fuses, one on each of the two positive wires.
 
Unless there is a special issue I recommend all major components be connected to the bus.
My fuse block/bus bar is a blue sea systems 125A marine bus. It says on the package max recommended max fuse is 30A.

Could I Have the wires coming from my 40A Solar Charge Controller go to the bus instead of the Shunt off the battery. It is a 40A fuse needed, and doing my calculation for max peak amps its 5.4 Amps per panel and I have 4 with no plans of adding any more so giving me 21.6Amps. Controller manual says to have 30A fuse between controller and Solar and 40A fuse between controller and Battery. Does a controller increase the Amps? Is that why they want 10A higher on the battery side?
Since I'm using less than the max rating of my controller could I wire the controller to the bus also like you said?
Would I keep the 40A fuse and just go 10 over what the bus recommends or just use a 30 since I'm only at 21.6, or go 35 as a compromise lol? The 21.6A is only midday peak sun on a cloudless day when the stars all align also, so would be rare if I got the max on all the panels that they state (but just my guess) The bus has 12 circuits and I'm only using 3 and all for very low Amp stuff. Am nowhere near the 125 A max of the bus. I wouldn't be using the AC-DC charger either on that bus at the same time as the Solar, or the LED lights
.
 
If the max controller potential current is 21 amps.... a 30 amp fuse is fine. Nothing wrong with using all systems at the same time.
 
It's not ideal to wire for what you think you will use versus what is actually available. You might forget it's only wired for 2000W instead of 3000W. Or maybe someone else tries to use it and doesn't know.

If you keep the 2/0AWG then I would use a 250A fuse. This way if you attempt to use the full 3000W (or anything over 2000W) then the fuse will properly protect the wire.


If it's wired with 2 pairs of 2/0AWG wires then each individual wire needs its own fuse. Don't use one 400A fuse, use two 200A fuses, one on each of the two positive wires.
Ah, gotcha. I was putting in a 300A Mega. I have a pack of 250's though. I will swap it out and put in the 250A until I replace the 2/0 wires for 4/0. Thank you for those suggestions.
I tested the inverter when I got it with an 1800 watt blowdryer to make sure I didn't have the same issue as other people posted about the inverter tripping at half the rated amperage, I needed the fan to kick on also to determine which fan was intake and which was exhaust, and it worked BUT those wires got real hot after about 60 seconds of use. I wonder how many people use the supplied wires and burn their car or house to the ground!

I was crossed between the GoWise inverter, the Reliable Electric, and the Giandel inverter. I picked the GoWise because no-load draw was 0.6A and on the other 2 it was higher, around 2.1A if I recall. BUT I have read from others that the GoWise rate their inverters just a little higher than actual real life, but this was fine for my use case as I don't plan on exceeding even 2,000watts.

I have a big system On/Off switch. My plan is to run the bus and all components through there on the way to the battery. Is that OK? I was going to also run the inverter through there as well, but read that is not advised, to just simply leave it switched off. I take it the inverters are not really meant to be disconnected and reconnected through a switch often?
 
Thank you guys so much for the help. You have really helped me to better understand everything and keep it safer too.

My last question is how do you know when you need a fuse on both the positive AND negative wire?
I always thought you only needed a fuse on the + wire, but my NOCO AC-DC charger has a fuse on both the + and -, and the wires coming in from the anderson connection also have a fuse on the + and the -. Is that always needed, or is it an extra redundant safety mechanism? Do I need another Mega fuse to attach on the negative wire from the Battery to the Inverter? I only have a 250A fuse on the positive wire now. I am quite confused and unsure when it's needed to include them on the negative wire also.
 
Normal DC circuits only need to be fused on the positive. I've never seen anyone ever fuse both positive and negative for an inverter's battery connections.

Apparently the NEC requires both be fused on PV wires though I can't recall what the exact reason for this is.
 
I always thought you only needed a fuse on the + wire, but my NOCO AC-DC charger has a fuse on both the + and -, and the wires coming in from the anderson connection also have a fuse on the + and the -.
Could be just a backup safety measure or also for systems with + ground where the return path may not just be through the opposite wire.
2/0 wire would be plenty for your inverter or even thinner and double up latter if a problem.
 
Normal DC circuits only need to be fused on the positive. I've never seen anyone ever fuse both positive and negative for an inverter's battery connections.

Apparently the NEC requires both be fused on PV wires though I can't recall what the exact reason for this is.
Not both fused.
Just both on disconnect.
If a disconnect is used. (Although not required)
 
UPDATE:
Hey guys, well I screwed myself. Could this be the reason why both leads had a fuse? So hidden inside the cable coming from the NOCO charge are 2 super tiny maybe 26ga wires. I cut the wire and now I'm stuck at a standpoint. NOCO won't answer what they are for. They say proprietary. I thought a temp sensor or a current sensor but they don't really go to anything I can see. Also, NOCO says If I dont use their ring terminals it voids the warranty. I could care less about a warranty but now I'm second guessing connecting directly to a bus and not using their terminals, that is if I should even still chance using this, I'll attach some photos. Not much info on google which is extremely surprising being this is the #1 selling battery charger. NOCO is of absolutely ZERO help also. There has to be someone that has taken this apart and figured out what's in there.
 

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My first inclination is voltage sensing wires. I see the cut cable... is that from the NOCO DC side? What does the other side look like?

I would tend to open the terminals and see what connects.
 
So hidden inside the cable coming from the NOCO charge are 2 super tiny maybe 26ga wires.
Most likely the temperature sensing leads. From the add...."Temperature Compensation For Accurate Recharging"....
May need to reconnect otherwise the compensation will be either high or low depending how they work.

Edit: From the photos should be easy enough. Probably no need to reconnect the power leads. You can still use your own terminals but connect the original ones containing only the sensor wires to the terminals as well. If you need to extend the 26ga use thicker wire.
 
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UPDATE:

So I cut and shortened both the AC and the DC end of the cables. On the DC end, I went with the assumption that it was a temp sensor and not a voltage or resistance sensor since it stops where the Black plastic NOCO thing is. So I assume that its in there whatever it is. it was 28 ga wires so it was a little annoying to splice back together but I did and it works fine I just charged 2 batteries with it. I was tempted to just leave it cut off since I only charge LiFePo4 batteries and no lead acid or AGM, it I believe for Lithium the temp sensors are not used, but I didn't want to chance it in case it knows I cut it off and then refuses to charge or does any funky business. I'm charging a battery now but later I will put a heat gun to that black part to see if it does anything while charging, I doubt it will on lithium. I don't have an acid battery to test it out with though.

So for future reference, if someone is googling this exact thing I hope this helps:

If you want to cut or shorten the wire from a NOCO charger don't bother contacting NOCO they will tell you the line, "You can only cut the wires that are after the inline fuses and you must reattach their connectors after you lengthen the cables." and that "NOCO chargers have a proprietary technology that uses 2 tiny wires inside their cables." and "Any cutting of the wires voids the warranty" Basically all trash and I was disappointed at their response. I don't think it's uncommon to want to change the length on an onboard (non-alligator clamp) charger.

Since they added the "temperature sensing technology" on their latest "Genious" chargers and only now do they have these wires, I think their new game-changing proprietary technology is just a plain ol temp sensor. Don't be fooled by their product photo showing a photo of a battery when they mention temperature sensing. This sensor is like 3ft away from the terminal ends that attach to the battery. It could only sense the heat from the wires or the ambient temperature NOT the temp of the battery.

YES, you can shorten or lengthen the cable. NO, you don't need to reuse their ring connectors, use whatever you want (the more surface area the better obviously). Keep the inline fuses though. Just be prepared to spend 30-45 mins splicing that cable, those 2 wires are very tiny and are too small for most splicers. I used a razor blade to separate the wires and my thumbnail to remove the jacket from the tiny wire. I put them in 24 ga heat shrink butt connectors (the silvery-white ones). and an extra-long 3:1 heat shrink cover to ensure it won't pull out.
Hope this helps the next person who is going through this same issue now. NOCO if you ever stumble upon this post... You suck! :)
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I hope everything worked out with your repair on the NOCO.
I want to address the battery connections.
First my definitions;
BusBar ; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs
Or, BusBar; https://www.bluesea.com/products/2107/PowerBar_600A_BusBar_-_Eight_3_8in-16_Studs__
Fuse Block; https://www.bluesea.com/products/5025/ST_Blade_Fuse_Block_-_6_Circuits_with_Negative_Bus_and_Cover
Cable ; Marine Grade Battery Cables. Made in the USA. Flexible tin plated copper stranding type 3, UL1426 BC5-W2 meets USCG and ABYC.

If you intend to have a 12 volt 3000W inverter? If the distance is close you may getaway with 2/0 cable. Check the voltage drop.
If VD ok, Then; Each Battery Positive -> 300 amp Class-T fuse -> 2/0 awg cable -> +BusBar1 ->200 amp MRBF -> 2 awg cable -> Fuse Block -> ST blade fuse sized to protect the wire -> wire for NOCO charger.
+BusBar1 -> 250 amp MRBF -> 2/0 cable -> 3000W inverter.
If you need 4/0 cable, up size the Class-T fuse and the MRBF inverter fuse and cables.
Always fuse to the ampacity of the wire.
Rule number one; Fuses protect wires.
Always wire for the maximum amperage of the device.
 
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