What do you think of our DIY wiring diagram? (Did we get the wire/fuse ratings right?)

sawmonandnatalie

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Hi all,

Thank you for all your help so far in this wonderful forum. Here is the latest diagram that we have with wire lengths and ratings as well as fuse/breaker ratings included:

Wire LocationMax Length (ft)Wire Gauge (AWG)Fuse/Breaker Rating (Amp)
Solar Panels to Combiner Box18.56-
Combiner Box to MPPT8620
MPPT to (+) Bus Bar8650
(+) Bus Bar to Battery2-42/0150
(+) Bus Bar to DC Fuse Box82/0150
(+) Bus Bar to Inverter82/0150
(+) Bus Bar to Alternator152/040
(+) Bus Bar to Converter Charger82/060
Inverter to ATS2710/3-
Converter Charger to ATS2710/3-

Are there any corrections that need to be made in our selection of wires or fuses?

Components Used:
  • 4 x 100 W, 12V Mono Solar Panels by Renogy (RNG-100D-SS)
  • EPEVER MPPT Solar Charge Control (Tracer4215BN)
  • 4 x EVE 3.2V 280AH Grade A Lifepo4 Battery Cells (link)
  • Smart BMS 4S cells 12V 120A (link)
  • 500A Smart Shunt by Victron (link)
  • Blue Sea Systems On/Off Switch (350A, max 48 VDC, 9003E)
  • Blue Sea Systems DC Fuse Block (5026)
  • 2200 W, 12V Pure Sine Inverter (Giandel: PS-2200KSC)
  • 30 A Automatic Transfer Switch (Go Power TS-30)
  • 45A 12V Charger/Converter (Progressive Dynamics, PD9145ALV)

The diagram is also attached in PDF format.

We haven't purchased the cables yet. But we are planning to use TEMCo Industrial for single wires and Ancor for 10/3 AWG.
 

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mikefitz

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Surprised at no comments yet. What a great diagram.

A few comments, the inverter at 2000 watt rating and 4000 watt peak, could take 160A or 323A peak if used at full capacity. (the current will be slightly higher due to losses and inverter efficiency, inverter efficiency at say 90% plus a bit for feed loses, takes the 2000 watt current requirement to 180 amps).

The BMS is good for 120 amps continuous that suggests a maximum load on the inverter of around 1500 watts before the BMS shuts down on current overload. ( the solar added current will help somewhat given some solar input).

I would increase the class T fuse value to a much higher value, say 300 amps.

There may be a problem with the inrush current into the inverter at first connection shutting down the BMS. If this an issue use a filimant bulb in series with the positive supply to pre charger the input capacitors in the inverter. I am using the same BMS that you are considering and have had no problem.

If you need to operate the inverter at full rated power you will need a higher rated BMS, ( or two in parallel). Or as an alternative wire direct to the battery, bypassing the BMS,


Auto transfer switch, this area needs consideration, you dont want the inverter feeding the battery charger.
Depending on local regulations or personal requirement you may need to add protective systems for over current and electric shock for the AC circuits.

General comments,

Unless you have already obtained the solar controller, consider the Victron Smart 100/30, its much easier to program than alternatives, has a long warranty and performs well. The app also gives useful info as the present and the last 30 days solar performance.

The BMS in the link can be obtained for Overkill ( with options like cable upgrade),
or from,

Mike
 

smoothJoey

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16 feet round trip is getting long for the inverter wire.
You only need 6 awg for the fuse box and you probably don't need the fuse box as you already have the combined ac/dc distribution panel.
Suggest you get and inverter/charger to replace the inverter, ac charger and transfer switch.
You don't need 2/0 for the ac charger 6 awg will do fine.
You should have a dc2dc charger between the alternator and the house system.

150 amp fuse is way to small for the inverter.
2200 ac watts / .85 conversion factor / 12 volts = ~215 dc amps
~215 dc amps / .8 fuse headroom = ~269 fuse amps

All your fuses should be / .8 above the max expected current
and the wires should be able to handle $fuse_amps

The biggest thing is to get a ul-458 listed inverter charger which btw includes an automatic transfer switch.

Nice drawing.
 
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sawmonandnatalie

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North Vancouver, Canada
Thank you @smoothJoey and @mikefitz for your comments.

You two are both right about the fuse rating for the fuse in between the (+) bus bar and the inverter. In our initial draft of the diagram, we had a bigger fuse size (Here is another thread regarding those choices). When we noticed that we had already purchased a 4S 12V 120A BMS, we decided to be protective of the BMS and have some fuses that have a smaller rating. After we made this second diagram and researched more about the specs of our BMS, we found this post on the forum pointing that our BMS has 30 MOSFETs (HY4903B6). Based on the datasheet each MOSFET can handle 1116 A of impulsed drain current (I think this is related to short circuit situations) at 25ºC. And depending on the temperature it can handle 222 A - 314 A of continuous drain current (just need to make sure there is a good heatsink available). So maybe a momentary surge current from the inverter would not damage the BMS. Also, another reason why we chose this BMS was that the max recommended charge/discharge rate for our cells is 0.5C (280A / 2 = 140A, max 140A per hour) Also, we are planning to not use the inverter heavily with our current setup. We also contacted Giandel, the inverter manufacturer, on Amazon and they suggested using a 200 A fuse (link to the Q/A). Based on your suggestion should we change this part of the diagram to:

(+) bus bar --- 250A fuse --- (2/0 AWG) --- 200A Circuit Breaker --- (2/0 AWG) ------------ 2200 W, 12 V Inverter

In the video you shared, @mikefitz , by @Will Prowse , he suggests not pushing MOSFET type BMSs more than half of the current rating. So in our case with the 120A BMS, that would be 60A. That's another thing to keep in mind for us, to have our continuous discharge currents less than 60A.

In the first draft, we also had a bigger class T fuse protecting the main line / positive terminal of the battery pack. We had a 350A class T fuse and we went ahead and purchased one. So we have a class T 350A fuse in hand if we decide to use it. Should we incorporate the 350A fuse there, or would you say to go and get a 300A one for this leg of the diagram?

(+) Battery Terminal --- (2/0 AWG) --- 300A or 350A class T fuse ? --- (2/0 AWG) --- (+) bus bar

Also, is the 150A fuse between the DC fuse box and the (+) bus bar ok?

(+) bus bar --- 150A fuse --- (2/0 AWG) --- DC Fuse Block

There may be a problem with the inrush current into the inverter at first connection shutting down the BMS. If this an issue use a filimant bulb in series with the positive supply to pre charger the input capacitors in the inverter. I am using the same BMS that you are considering and have had no problem.
We just learned about this inrush current with inverters and noticed folks suggesting to put a bulb or a resistor when first connecting the inverter. We need to learn more about this. Thank you for mentioning it.


Auto transfer switch, this area needs consideration, you dont want the inverter feeding the battery charger.
Depending on local regulations or personal requirement you may need to add protective systems for over current and electric shock for the AC circuits.
That is true. We knew about this problem and thought that the auto transfer switch that we selected only supplies current to the charger from the shore and not from the inverter lines. We have the Go Power TS-30 ATS. This unit might be a rebranded Progressive Dynamics ATS. We found this diagram for our ATS:

61sT0PesJPL.jpg
How would we check to see if this ATS does not allow a loop from battery > invertor > ATS > charger > battery?
Also, what kind of protective systems do we need to have to meet the local regulations for over-current and electric shock from the AC circuits?

We have already purchased the MPPT charge controller. We went with EPEVER MPPT Solar Charge Control (Tracer4215BN) since it can be highly customized (in its settings) based on other people's recommendations.

And also have already purchased the 4S 12V 120A BMS from aliexpress. It came with three 10 AWG wires soldered on each side.


16 feet round trip is getting long for the inverter wire.
You only need 6 awg for the fuse box and you probably don't need the fuse box as you already have the combined ac/dc distribution panel.
Suggest you get and inverter/charger to replace the inverter, ac charger and transfer switch.
You don't need 2/0 for the ac charger 6 awg will do fine.
You should have a dc2dc charger between the alternator and the house system.
We roughly put in the measurements for the wire lengths and over-speced the wire gauges to be on the safe side. It is kind of hard to know how far the devices/components are from each other before putting them all together. The inverter probably going to end up way closer to the positive bus bar and the battery pack.

Based on the wire length, max capacity of the DC Fuse block (100A) and 1%-3% voltage drop, we calculated that we needed to use 1/0-4/0 cable between the (+) bus bar and the DC fuse block. Again, it's probably over-speced. The RV AC/DC panel is only connected to a few AC power outlets and water pump, interior lights (and 2 more things). But there is no more room to add more fuses for more DC appliances such as USB chargers, ... .

The inverter/chargers that we came across with, for example, the ones from Victron, seemed out of our budget. That's why we didn't go with them. Do you have suggestions for cheaper ones that still are of good quality?

Yes, we have over-speced for the ac charger cable as well. Based on the calculations we did and the range of wire gauges that we ended up with for each section of the diagram, it made more sense to pick mostly 6 AWG and 2/0 AWG cables and order in bulk.

You are absolutely right for placing a DC2DC charger between the alternator and the house system. We are still contemplating if we should hook up the solar battery pack to the alternator. We are worried we might end up burning the alternator. Would you recommend using the alternator as another power source for the battery pack? If we do decide to go this route, we would probably get the Orion-Tr Smart DC-DC Charger 12 | 12 - 30.

Also, we have another conversation going about our diagram on reddit. If you are interested, here is the link:
https://www.reddit.com/r/SolarDIY/comments/mcff9f
 

smoothJoey

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Sorry the new drawing is too small for my eyesight.
As for the bms see the math in my previous post.
You would need to run 2 of the overkill in parrallel or control the inverter via an ssr or use a contactor.
 

smoothJoey

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I haven't any experience with this inverter/charger but I'm intrigued.
If I was you I would contact support and see if it switches the neutral/ground bond.
 

Whinny

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Xantrex freedom has neutral/ground bonding when inverting, so does their Prosine and Prowatt.
 
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smoothJoey

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Xantrex freedom has neutral/ground bonding when inverting, so does their Prosine and Prowatt.
And un-bonded when mains power is available?
Sounds like you have experience with them.
What is your opinion of them generally?
 

mikefitz

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So in our case with the 120A BMS, that would be 60A. That's another thing to keep in mind for us, to have our continuous discharge currents less than 60A.
Donnt worry with this BMS. I have tested at 110 amps continuous for 2 hours, there is no significant rise in the BMS temperature, slightly warm to touch.
So maybe a momentary surge current from the inverter would not damage the BMS.
It should not damage but the BMS may cut out due to over current. Its possible to program the over current and the time delay before it acts. There is also a resistor shunt on the BMS circuit board ( multiple low value surface mount) to consider.

Mike
 

smoothJoey

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Donnt worry with this BMS. I have tested at 110 amps continuous for 2 hours, there is no significant rise in the BMS temperature, slightly warm to touch.
See my math above its a 2200 watt inverter at 12 volts.
It should not damage but the BMS may cut out due to over current. Its possible to program the over current and the time delay before it acts. There is also a resistor shunt on the BMS circuit board ( multiple low value surface mount) to consider.

Mike
Disconnecting under significant amperage is quite a lot of stress on a fet based bms.
As is running them approaching capacity.
I have a high opinion of the Overkill offerings but heat stress reduces the life of a bms as does disconnecting under load.
 

jwelter99

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Xantrex is good stuff. Standard equipment on Leisure Travel Vans and most of the new Winnebago Sprinter based vans. I prefer Victron but if already own Xantrax no reason to replace it.

Agree on a B2B between alternator and house battery bus. I like the Sterling BB1260 but others available.
 

Raj174

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The fuse in the inverter line is there to protect the 2/0 (THHN) wire which has an ampacity of 190 amps in conduit and 265 amps in free air. I recommend the fuse be rated just under either of these values based on the use of conduit or not. To put it another way. If the fuse amp rating is greater than that of the 2/0 wire, the wire will melt before the fuse blows.
 
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smoothJoey

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The fuse in the inverter line is there to protect the 2/0 (THHN) wire which has an ampacity of 190 amps in conduit and 265 amps in free air. I recommend the fuse be rated just under either of these values based on the use of conduit or not. To put it another way. If the fuse amp rating is greater than that of the 2/0 wire, the wire will melt before the fuse blows.
THHN is rated for 105C for use as machine tool wire.
Its my understanding that means it good for up to 330 amps.
Did someone specify THHN?
 

Raj174

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THHN is rated for 105C for use as machine tool wire.
Its my understanding that means it good for up to 330 amps.
Did someone specify THHN?
I'm not familiar with that rating, I got the ratings I posted from ampacity charts that show THHN rated at 90°C. I used THHN because it's common. If the op used another type of wire, then the fuse rating needs to be adjusted for that wire type. The point is, the wire determines the fuse size, not the equipment.
 

time2roll

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I would stay a bit tight with a Class T. This is somewhat of a slow blow fuse that can pass 150% for 8 minutes and 200% rating for a full minute. I would be at 200 amps, 225 max.

ClassT_Fuse.jpg


https://www.bluesea.com/products/5117/Class_T_Fuse_-_225_Amp
 

sawmonandnatalie

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Thank you all for your replies. We educated ourselves a bit more about all these subjects especially neutral/ground bonding.

Based on our research and also some questions on Amazon product pages (ATS Question, Inverter Question), looks like our Go Power TS-30 ATS does not automatically bond the neutral/ground lines coming from the inverter when connected to an inverter and unbond when connected to the shore. And also possibly the inverter has the ground/neutral unbonded. Reading this post, the solution might be using a custom plug hooked to the inverter with the ground and neutral connected. We just need to make sure there is no other ground to neutral bond in the AC side of the offshore system, then use this plug. Also, unplug when hooked up to shore power. Are there any other precautions we should look into for the AC side of the system?

Thank you @smoothJoey for the inverter/charger suggestion. We will keep that in mind for future projects.

@Raj174 , like @smoothJoey mentioned, the 2/0 welding cables that we are planning to use are rated for 105ºC with the max amp of 325A (product page).

Maybe for the (+) battery terminal fuse, it might be more appropriate to use a 250A fuse that would?

(+) Battery Terminal --- (2/0 AWG) --- 250A class T fuse ? --- (2/0 AWG) --- (+) bus bar

Any higher surge current which might take a minute or so (500A) based on the diagram @time2roll shared will be covered by the BMS over-current protection. And in that case, it might be best to replace the wires in this leg with a 4/0 cable.

So, how do you all feel about these fuse ratings and cable sizes:

(+) Battery Terminal --- (4/0 AWG) --- 250A class T fuse ? --- (4/0 AWG) --- (+) bus bar
(+) bus bar --- 250A fuse
--- (2/0 AWG) --- 200A Circuit Breaker --- (2/0 AWG) ------------ 2200 W, 12 V Inverter
(+) bus bar --- 150A fuse
--- (2/0 AWG) --- DC Fuse Block

@smoothJoey , we have included the diagram in PDF format with the first post in this thread. You can download the PDF and zoom in on different sections to see everything clearly.
 

elpulpo

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What did you do this diagram with? Great job on it, I'm still trying to figure out the best way to get all of the information into my diagrams and keep it legible. Do you think the 2/0 AWG wire is a bit much for this system? At under 15 Feet 2AWG should be good for 120A, and 1AWG for 150A. I noticed a lot of the diagrams use 2/0 AWG going to the inverter as well and coming off the batteries but for a small system like mine seems like overkill. Maybe the difference is I'm running 24V and expecting loads under 2000W.
 

Stepandwolf

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Sorry the new drawing is too small for my eyesight.
As for the bms see the math in my previous post.
You would need to run 2 of the overkill in parrallel or control the inverter via an ssr or use a contactor.
FYI, if you click on the picture, it takes you to the source picture on Reddit, and if you click on that picture, you will be given a high res picture. This link might take you directly schematic
 

iquibalamenpau

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Hi, what a fantastic sawmonandnatalie diagram,
I couldn't resist copying your information to create my own design. I have very little knowledge of electronics and your diagram has been very helpful to represent mine in a simpler way.

I hope that somebody could give me a recommendation on my design, fuse rate and wire size. I’m open to any recommendations and adjustments.

Thanks to everyone

Wire LocationMax Length (meters)Wire, mm2Fuse/Breaker Rating (Amp)
Solar Panels to MPPT510 - 16 ???20
MPPT to (+) Bus Bar0.5640
(+) Bus Bar to Second Battery0.525100
(+) Bus Bar to DC Fuse Box0.525100
(+) Bus Bar to Alternator0.525100
(+) Bus Bar to Orion DC-DC0.510 ?45 ?
Orion to main car Battery6.535 ?60
(+) Bus Bar to Inverter0.535150
Inverter to loads 22052.5-


Components Used:
  • 1 x 370 W, 24 v, Mono Solar Panels by Jinko ( Link )
  • Smart Solar 100|30 MPPT by Victron ( link )
  • Orion tr DC-DC 30A Isolated by Victron ( link )
  • 4 x REPT 3.2 280 AH Lifepo4 Battery cells ( link )
  • Smart BMS 4S cells 12V 120A (link)
  • 300 A Shunt by Mictuning ( link + link shunt )
  • 1000 W, 12V, Pure Sine Inverter ( link )
  • Main switch 300A ( link )
  • Auto midi Fuses (50A to 100A) (Link)
I am living in Europe and I am using this table to guide me in the current withstand in amperes of the cables



Doubts:

1- I am going to use the Inverter to power 2 laptops and a 50L fridge (which opens three times a day). Is it necessary to increase the 25mm2 cables and the 100A fuses?

2- In the MPPT Smart Solar manual, it indicates that it is optional to connect the ground (chassis), is it recommended?

3- Can I connect the negatives (-) of both batteries through the chassis ? Instead of two negative cables from the Orion DC-DC to each battery.

4- Do the negatives (-) have to be connected to the chassis in a lifepo4 system?

5- Should I fuse the positive (+) cable of the main battery to Orion tr?


See the diagram attached in pdf
 

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