Power Input and Output of Fuse Block -

[trevor.aaron]

Hi all, I'm fairly certain this is a stupid question, but I can't find an answer online....

Question: will it work to have a Fuse Block connect all the power output and input, and then have a single negative and positive connection to my battery bank? Will the fuse block be able to allow the battery to accept power input from solar as well as power output from the inverter? Or am I thinking about this the complete wrong way, and if total power draw from the inverter is greater than any power input the electrons from Solar AND Battery flow to the inverter? I feel like this is a grade school question....

Additional Question on Battery Monitor: I want to install a Victron BMV 712. Will it work to install the smart shunt on the negative line from Battery Bank to Fuse Block? From what I can read, this will work but figured I'd ask here in case anyone has experience with this.

Setup: Two 100Ah LiFeP04 batteries, short 2 AWG cables from the battery bank to the Fuse Block. Fuse Block has everything plugged into it, both input and output, such as solar input (from a Victron MPPT controller), DC to DC charger input (also from a Victron DC Charger controller), and a few outputs including an inverter. The Fuse Block is a Blue Sea Systems SafetyHub, and accepts a few low amp blade fuse, and it accepts a few high amp fuses.

 

[rmaddy]

I think it would help if you posted a wiring diagram of what you are proposing. It doesn't sound quite right but a drawing will make it easier to be sure what you are proposing and to provide feedback.

 

[trevor.aaron]

Sure thing, here's my diagram. Thanks in advance for your help!

 

[John Frum]

SCC system side fuse should be 40 amps
The cutoff switch on the pv side of the scc needs to be rated for the panel voltage. Many are only rated for 48 volts.
4 awg is too small for a 2000 watt inverter
2000 ac watts / .85 conversion factor / 12 volts low cutoff = 196.078431373 dc amps
196.078431373 dc amps / .8 fuse headroom = 245.098039216 fuse amps
suggest 1/0 or bigger with 250 amp fuse

The battery wires should be 1/0 or bigger
should be a 250 amp fuse between the battery and the cutoff switch

 

[John Frum]

The shore power ac2dc charger should be connected to a fused position on the busbar.
Looks your safety block won't have enough positions though.

 

[John Frum]

Hi all, I'm fairly certain this is a stupid question, but I can't find an answer online....

Question: will it work to have a Fuse Block connect all the power output and input, and then have a single negative and positive connection to my battery bank? Will the fuse block be able to allow the battery to accept power input from solar as well as power output from the inverter? Or am I thinking about this the complete wrong way, and if total power draw from the inverter is greater than any power input the electrons from Solar AND Battery flow to the inverter? I feel like this is a grade school question....

If I understand what you are saying above.
Yes, its the orthodox design pattern.

Additional Question on Battery Monitor: I want to install a Victron BMV 712. Will it work to install the smart shunt on the negative line from Battery Bank to Fuse Block? From what I can read, this will work but figured I'd ask here in case anyone has experience with this.

Yes the shunt goes between the negative terminal of the battery and the rest of the system so that it can account for all current in and out of the battery.
In your drawing the ac2dc charger bypasses the shunt.

Setup: Two 100Ah LiFeP04 batteries, short 2 AWG cables from the battery bank to the Fuse Block. Fuse Block has everything plugged into it, both input and output, such as solar input (from a Victron MPPT controller), DC to DC charger input (also from a Victron DC Charger controller), and a few outputs including an inverter. The Fuse Block is a Blue Sea Systems SafetyHub, and accepts a few low amp blade fuse, and it accepts a few high amp fuses.

I think you are going to be at least one fused position short.

 

[John Frum]

You show 2 batteries with 1 bms.
That is probably not want you mean, confirm?

 

[trevor.aaron]

Thanks for all the help and advice on this! I should have mentioned, this is for a small camper van. We're installing under the seat and are not planning on running very long cable (the longest cables are going to be from Solar Panels to the SCC, and DC to DC Charger into the DC Charge Controller, everything else is about 5 feet long or less (until I plug an extension cord into my inverter to power a laptop or other appliance...)

SCC Fuse (From Charge Controller to Fuse Block) - should be 40Amps, not 30 - 30amps ought to be safe though, yeah? All in all I'll probably take your suggestion, will change this thank you!
PV Cutoff Switch, Rated for Panel Voltage - you are right, the switch I bought is rated for 48v, not 12v. What is the implication of not getting the right voltage switch here? Do you have a recommendation for one to get?
4AWG Wiring to Inverter - 4AWG wiring came with the Renogy unit so I figured that ought to be safe. Looking at the wiring charts I should be able to safely draw 100Amps about 5 feet through 4AWG wire. With our current planned devices, the only time I'll draw more than 100Amps at a single time is if we run a hot water kettle (125A) which still should be safe since we'll be running less than 5ft of cable. Let me know if I'm missing an element here.
Battery Cable - 2AWG should be safe given the length of everything? Everyone I've chatted with says that gauge should be fine for what we're doing.
Fusing Between Cutoff Switch and Battery - Can you elaborate on this one a bit, I should have a fuse for the battery bank into the battery cutoff switch that leads into the fuse box? My understanding (probably wrong) is that if every device had it's own fuse, that should be sufficient because those devices are what is pushing/pulling power into the battery bank
Shore Power Should be Connected to a Fuse - I did not know this... will get a fuse and connect it into my fuse block. I have 4 "Bigger" ports (can handle 30A to 200A) and 6 "Smaller" ports (can handle 1A to 30A). Connecting these directly to the battery terminals is a problem in case there's a short circuit in the Victron shore power unit itself?
AC2DC Charger Bypassing Shunt - Noted! Will connect that to the fuse block which should fix that problem. Thank you!
One Fused Position Short - Can you elaborate on that a bit?
2 Batteries with 1 BMS - Yes this is what I wanted. Maybe I only need one positive wire connected to one of the positive terminals? I thought the BMS would be capable of handling a battery bank.

Thank you for your help and advice on this!

 

[mikefitz]

The batteries and the BMS need clarification, what batteries are they , are they Victron lithium smart?

Mike

 

[John Frum]

Thanks for all the help and advice on this! I should have mentioned, this is for a small camper van. We're installing under the seat and are not planning on running very long cable (the longest cables are going to be from Solar Panels to the SCC, and DC to DC Charger into the DC Charge Controller, everything else is about 5 feet long or less (until I plug an extension cord into my inverter to power a laptop or other appliance...)

SCC Fuse (From Charge Controller to Fuse Block) - should be 40Amps, not 30 - 30amps ought to be safe though, yeah? All in all I'll probably take your suggestion, will change this thank you!

Its best practice to add a bit of headroom to avoid nuisance trips.
30 service amps / .8 fuse headroom = 37.5 fuse amps which rounds up to 40 amps.

PV Cutoff Switch, Rated for Panel Voltage - you are right, the switch I bought is rated for 48v, not 12v. What is the implication of not getting the right voltage switch here? Do you have a recommendation for one to get?

For efficiency panels are usually configured in series to increase the circuit voltage and therefore decrease voltage drop.
What are the voltage specs for the panels?
If the switch is not rated for the circuit voltage it may not extinguish an arc on disconnect.

4AWG Wiring to Inverter - 4AWG wiring came with the Renogy unit so I figured that ought to be safe. Looking at the wiring charts I should be able to safely draw 100Amps about 5 feet through 4AWG wire. With our current planned devices, the only time I'll draw more than 100Amps at a single time is if we run a hot water kettle (125A) which still should be safe since we'll be running less than 5ft of cable. Let me know if I'm missing an element here.

4 awg wire with 105c rated inslulation is only good for 160 amps.
This is well undersized for the max continuous rating of your inverter let alone fuse headroom.
If it was me I would do 2/0 awg along the critical path.
It is my policy to always design for max continuous rating for high frequency inverters.
For low frequency inverters the requirements are even higher.

Battery Cable - 2AWG should be safe given the length of everything? Everyone I've chatted with says that gauge should be fine for what we're doing.

I disagree and I've shown you the numbers and links to back my assertions.

Fusing Between Cutoff Switch and Battery - Can you elaborate on this one a bit, I should have a fuse for the battery bank into the battery cutoff switch that leads into the fuse box? My understanding (probably wrong) is that if every device had it's own fuse, that should be sufficient because those devices are what is pushing/pulling power into the battery bank

There should be a means of over current protection as close to the battery positive terminal as possible.
This minimizes the chance of a short upstream of the fuse which would be a disaster.
A general axiom is there should be fuse at each change in wire size.
Also ensure that the arc interuppt capacity of the fuse is sufficient for lifpepo4 batteries.

Shore Power Should be Connected to a Fuse - I did not know this... will get a fuse and connect it into my fuse block. I have 4 "Bigger" ports (can handle 30A to 200A) and 6 "Smaller" ports (can handle 1A to 30A). Connecting these directly to the battery terminals is a problem in case there's a short circuit in the Victron shore power unit itself?

The applicable axiom here is each charge source needs to be fused as close to origin as possible.
There are some exceptions to this rule for panels but I'm not really a panel guy.

AC2DC Charger Bypassing Shunt - Noted! Will connect that to the fuse block which should fix that problem. Thank you!
One Fused Position Short - Can you elaborate on that a bit?

Your ac2dc charger should be connected to a midi fused position on your fuse block.
Since you have 4 you should be ok.

2 Batteries with 1 BMS - Yes this is what I wanted. Maybe I only need one positive wire connected to one of the positive terminals? I thought the BMS would be capable of handling a battery bank.

Thank you for your help and advice on this!

You want a 1 to 1 ratio of bms to battery.
Is this a diy battery made from cells?
If yes, you could make a 2p4s battery.
Have you sourced a bms that can handle 200+ amps continuous?

 

[trevor.aaron]

Thanks again all, really appreciate your help on this.

Batteries - two of these (Amazon Link, Expert Power 12v 100Ah Lithium LiFePO4 Deep Cycle Rechargeable Battery)
BMS - One of these (Amazon Link, Victron Energy BMV-712 Smart Battery Monitor)

SCC Fuse - Noted! Thanks for the clarification, this is very helpful.

PV Cutoff Switch - I'm wiring in parallel so we keep everything at 12V. Here are the voltage specs for the panel (Renogy website link). This is very interesting and something I didn't know or consider. If my switch is rated 48V (Switch link on Amazon for reference) will it not work with my 12V solar setup?

Inverter Wiring - Noted! So I should plan to wire a lot more than my current power requirements, in case someone comes along and plugs something in I had never intended. I'll take that back and consider getting larger gauge wiring per your recommendations.

Battery Cable - Noted! Thank you!

Battery Monitor - Does the 1 to 1 ratio of BMS to Battery hold true even for a battery bank wired in parallel?

 

[John Frum]

I just noticed that you have the ground bond off of the battery.
If you have a fault in any equipment with a ground lug you will bypass your shunt and your bms.

 

[John Frum]

Thanks again all, really appreciate your help on this.

Batteries - two of these (Amazon Link, Expert Power 12v 100Ah Lithium LiFePO4 Deep Cycle Rechargeable Battery)
BMS - One of these (Amazon Link, Victron Energy BMV-712 Smart Battery Monitor)

Those batteries have built-in BMSs
The BMV-712 is a battery monitor not a BMS.

PV Cutoff Switch - I'm wiring in parallel so we keep everything at 12V. Here are the voltage specs for the panel (Renogy website link). This is very interesting and something I didn't know or consider. If my switch is rated 48V (Switch link on Amazon for reference) will it not work with my 12V solar setup?

Unless you are mitigating shade problems you should put your panels in series.
I'm not a panel guy but I do know that much.

Battery Monitor - Does the 1 to 1 ratio of BMS to Battery hold true even for a battery bank wired in parallel?

Battery Monitor != BMS.

 

[chrisski]

What is the specific fuse box you plan on I using? That is a brpad selection. I‘d recommend a Class T fuse for inverter and battery. Has to do with a fuse blowing and the lithium battery having enough arc to shoot across the blown fuse. It’s also probably what your owners manual for your inverter says

 

[John Frum]

Overlooked your question about switches.
As long as the switch voltage exceeds the max voltage expected on the wire you are good.

 

[John Frum]

You should bump up the wire gage between the solar charge controller and the fuse block to 8 awg minimum.

 

[trevor.aaron]

Thank you all! This is very helpful. I did not know the two were not the same (BMS and battery monitor).

Battery Monitor Setup - Knowing that each battery has a BMS, along with the BMV-712 - will my existing setup work just fine (i.e. shunt installed and the Victron BMV power cable wired to the positive battery terminal)?

PV Panel Cutoff Switch - Awesome, thanks. Glad to have a second pair of eyes on this, appreciate it. I'm wiring these in parallel for exactly that reason, mitigate shade problems since we'll be moving around quite a bit and can't perfectly predict where shade will be when we park.

Ground off of the battery - Interesting and noted! Thank you! Where would you recommend I ground off of in that case? I'm happy to move the ground, just wasn't sure where exactly to place it

@chrisski the specific fuse box is the Blue Sea Systems Safety Hub 150. If I end up having to add additional fuses outside of the SafetyHub fuse block, how would I go about connecting everything together (i.e. battery bank, Fuse Block, and additional fuses outside of the fuse block)?

 

[John Frum]

Thank you all! This is very helpful. I did not know the two were not the same (BMS and battery monitor).

Battery Monitor Setup - Knowing that each battery has a BMS, along with the BMV-712 - will my existing setup work just fine (i.e. shunt installed and the Victron BMV power cable wired to the positive battery terminal)?

That will work but if it was me I would connect the positive lead to one of the blade fused positions on the fuse block.
Assuming you have one free.

PV Panel Cutoff Switch - Awesome, thanks. Glad to have a second pair of eyes on this, appreciate it. I'm wiring these in parallel for exactly that reason, mitigate shade problems since we'll be moving around quite a bit and can't perfectly predict where shade will be when we park.

Ground off of the battery - Interesting and noted! Thank you! Where would you recommend I ground off of in that case? I'm happy to move the ground, just wasn't sure where exactly to place it

I suggest you use a separate busbar for the negative side of the circuit.
Ground off of that.

@chrisski the specific fuse box is the Blue Sea Systems Safety Hub 150. If I end up having to add additional fuses outside of the SafetyHub fuse block, how would I go about connecting everything together (i.e. battery bank, Fuse Block, and additional fuses outside of the fuse block)?

If you need more high current circuits that the 150 can support I suggest you switch to higher capacity fused busbar like this.

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder, 7 Stud Assembly with Bolts and Bus Bars, 400A is in stock and ready to ship. Order today!

www.waytekwire.com

 

[chrisski]

@chrisski the specific fuse box is the Blue Sea Systems Safety Hub 150. If I end up having to add additional fuses outside of the SafetyHub fuse block, how would I go about connecting everything together (i.e. battery bank, Fuse Block, and additional fuses outside of the fuse block)?

I guess what I’m trying to say is your High Amperage fuse is the AM fuse which The AIC is 5000 amps at 12 volts and 2000 amps at 32 volts. What that means is your battery fuse blow and then arc across and keep going as if the fuse was not there. A lithium battery can make 10,000 amps on a short. The only thing I have found to interrupt that amount of current is a Class T Fuse. A 200 amp clad T fuse will run you about $70, and a mount will run you about $50.

I currently am doing a lithium upgrade and am using lead acid. So, I have my positive cable the next thing attached is a 200 amp ANL fuse holder with a fuse, then a 350 amp battery on off switch, and then the busbar.

When I up grade to lithium, I will replace the ANL Fuse holder and fuse with a class T fuse and fuse holder.

So, connect the Battery fuse the first thing after the battery.

Lots of people don’t use Class T fuses, but for the reasons I explained they are much safer, and probably what is required for lithium’s by code If you were building this system in a house.

 

[Just John]

PV Cutoff Switch - I'm wiring in parallel so we keep everything at 12V. Here are the voltage specs for the panel (Renogy website link). This is very interesting and something I didn't know or consider. If my switch is rated 48V (Switch link on Amazon for reference) will it not work with my 12V solar setup?

You should really reconsider the flexible solar panel, or plan on replacing them every year or two.