[RV8R]

I'm guessing that the other 250A breaker before the 2000W inverter is also probably useless. I didn't realize there was the 125A max output on the batteries, I missed that detail.

I suppose if I ever add another 170AH battery, they would come in play...

If you want to design your electrical for future possible upgrades; size the wire for future use & size the (breaker or fuse) lower for the 125A max & then in the future you only need to swap out the (breaker or fuse)

 

[GaryBIS]

Gary, I may return this 80A breaker in lieu of this method. Just one question as to why you chose a 100A fuse on the battery? Isn't the default stock alternator in the PM at 70A? I thought 80A would be enough, no?

Hi,

I think 80 amp would probably be fine.

On my setup, the this wire has protection at both ends (house battery on one end and van battery on the other end - no B2B, just an isolator between the two bats). I used the larger 100 amp fuse on the van battery end and an 80 amp breaker on the house battery end so that if the line experienced an over current, the 80 amp breaker would open, and its easy to reset the this breaker than to replace the fuse on the van battery, which would be a bit of a pain to replace. My wire run is #6, so a 100 amp fuse is OK. Part of using the smaller breaker on the house battery side was that if the charging current went substantially over 80 amps it would alert me by blowing - I don't want it to go that high. In reality, the charging current does not go above 40 amps for my golf cart FLA batteries.

Gary

 

[van_dammit]

Part of using the smaller breaker on the house battery side was that if the charging current went substantially over 80 amps it would alert me by blowing

Thanks for the explanation, that clears up my confusion. Im thinking I could do the same here since I do still have my 80A breaker, put it on the battery side as well to trip off any overcharge. Would that work in my scenario? with the 80A fuse + 80A breaker, or would the fuse blow before the breaker?

 

[larry barello]

The fuse will likely blow before the breaker, but, don't overthink this. I have the same DCC50 and I have never seen more than 40A draw. YMMV. Even if it did supply 50A to the house battery, it would only draw a tad more than 50A from the starter. I, personally, think there is no need for the breaker at the DCC50 side of the wire, but it is sure convenient to be able to disconnect the service battery when working on the wiring.

 

[GaryBIS]

Thanks for the explanation, that clears up my confusion. Im thinking I could do the same here since I do still have my 80A breaker, put it on the battery side as well to trip off any overcharge. Would that work in my scenario? with the 80A fuse + 80A breaker, or would the fuse blow before the breaker?

Hi,
I'm not sure - both fuses and breakers are designed to have different amounts of overload they are designed to tolerate for different times (eg slow blow fuses vs fast blow fuses). You might be able to dive into the characteristics of the fuse and breaker you use to get the breaker to go first?

If you want to have the breaker on the house battery blow first, there is nothing wrong with using a higher amperage for the van battery fuse as long as its not higher than the ABYC ampacity rating for the wire. Looks like #8 is good for 80 amps and #6 for 120 amps for 105C insulated wire.

I'm not sure its worth getting too wrapped around the axle on the amperage ratings - I once saw a #14 wire with a dead short to ground trip a 200 amp breaker! And, it was so fast, the insulation on the #14 wire was not even burned or melted. I'm not saying exactly how this happened But, always good to stay with the code, and the ABYC is (I think) a good one to use for RVs.

edit: corrected mistake in paragraph 2.

Gary

 

[van_dammit]

Last revision:

• replaced the 250A fuses and breakers for a 125A fuse and 120A breaker to the inverter (125A Max output of the 170AH battery)
• removed the extra water pump, I'll use a portable water pump with the cigarette outlet 12V, gives me an extra wire for lights or CO2 monitor
• added an 80A fuse on the starter battery to DCDC, kept the 80A breaker to turn off that battery connection if needed
• downgraded to 320W solar, 2x160W Newpowa (smallest I can find to save room on the roof)
• 50A breaker from the solar to isolate solar

If i need more power, i would consider buying another 170AH battery and up the fuses/breakers to 250A

 

[larry barello]

I was looking at the specification sheet for the battery you have. BATT-LFP-12-170.pdf (renogy.com) It is impressive. If you believe their life cycle charts the battery can deliver ~8 mwh cycling 30% DOD! (3 mwh @100% DOD) The battery also has an impressive short circuit specification. Looks bullet proof.

I'll point out my pet OCD issue. The wiring diagram has three control elements in the high current inverter loop. A post fuse, a disconnect and the breaker. That is a lot of connections (each one costs power and voltage drop) and all functions can be served by one breaker replacing the disconnect switch.

Other than that, a super clean design.

 

[GaryBIS]

...
I'll point out my pet OCD issue. The wiring diagram has three control elements in the high current inverter loop. A post fuse, a disconnect and the breaker. That is a lot of connections (each one costs power and voltage drop) and all functions can be served by one breaker replacing the disconnect switch.

Other than that, a super clean design.

This seems like a good point to me -- as long as you are using the same wire gauge in the run from the battery to busbar as for the run from busbar to inverter, the post fuse protects both runs.
I personally would prefer the post fuse and switch to a single breaker - logic being that it is two components instead of one, but both are likely to be more reliable than the single breaker. But, that's probably my OCD

Gary

 

[larry barello]

I totally get your concern regarding the reliability of the breaker. Quality breakers I looked at are rated for only about 100 cycles. I presume those cycles are over-current events. I guess, one tries to design the system so tripping is an infrequent event.

I struggled with crummy breakers and finally replaced it with a disconnect and fuse - and purchased spares. Now that I have quality breakers (from my testing) I intend to put the breaker back in. I just need to get a "round tuit".

 

[van_dammit]

I was looking at the specification sheet for the battery you have. BATT-LFP-12-170.pdf (renogy.com) It is impressive. If you believe their life cycle charts the battery can deliver ~8 mwh cycling 30% DOD! (3 mwh @100% DOD) The battery also has an impressive short circuit specification. Looks bullet proof.

I'll point out my pet OCD issue. The wiring diagram has three control elements in the high current inverter loop. A post fuse, a disconnect and the breaker. That is a lot of connections (each one costs power and voltage drop) and all functions can be served by one breaker replacing the disconnect switch.

Other than that, a super clean design.

I see, I could just eliminate that 120A breaker between the Inverter and the Positive Busbar. That 2/0 awg wire would be a short run ~1ft. That would save me some much needed space.

Yes the 125A post fuse wire would be the same size wire, 2/0 awg, so it seems like it would be protected to the Inverter. Last thing I want is a voltage drop to the Inverter, I just wanted to err on the safe side.

Thanks for the pointers on this, I've learned a bunch!

 

[free2roam]

Hello, I see from your diagram that you are using a 125 amp fuse mounted to the terminal of your 170 amp Renogy battery which uses a M12 bolt and requires a 1/2" ring terminal, have you found a fuse that will fit? I have been looking with no luck!

 

[van_dammit]

Hello, I see from your diagram that you are using a 125 amp fuse mounted to the terminal of your 170 amp Renogy battery which uses a M12 bolt and requires a 1/2" ring terminal, have you found a fuse that will fit? I have been looking with no luck!

Yes, this is the odd thing about those Renogy 170AH batteries is that the terminals are 1/2 inch. I just bought the Blue Sea terminal fuse and drilled out the hole to 1/2" using a drill press and step bit and now it fits fine.

 

[free2roam]

Yes, this is the odd thing about those Renogy 170AH batteries is that the terminals are 1/2 inch. I just bought the Blue Sea terminal fuse and drilled out the hole to 1/2" using a drill press and step bit and now it fits fine.
[/QUOTE]
Thanks for the information, one more problem solved!