Multiplus 24/3000 and Daly 250 Smart BMS

interestingfellow

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Aug 5, 2020
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First post here, thank you for having me!

I'm trying to sort out the details of exactly how to hook up my camper for full off grid power.
I've read a bunch and consumed a bunch of videos and I'm still a bit confused about fine details.

I will be running a Daly 250 Smart BMS to manage an 8s Eve280 battery bank (hoping to make that 2s8p very soon)
I have Triron 4210N that I'm planning on 1400w or so for the roof

And this is all to support a Victron Multiplus 24/3000 that will be tied into the camper AC electrical system

The Multiplus is supposed to be max constant 125a draw, 300a peak
The Daly is supposed to be good for 125a supply, 250a peak (maybe more if one believes internet claims)

I'm looking at using a Class T 400a fuse between the batteries and the BMS for catastrophic failure protection
And then a 300 ANL between the Daly and the Victron. Does that sound right?

I also think I'm going to put a 60a fuse on the triron charging into the Daly, as well.
The multiplus can do charging when on shore power, which is just a convenient option (or if I have to use a generator) and I will be relying on the Triron to do most of my charging almost all of the time.

Am I getting anything wrong here?

I will diagram this out when I have a higher level of confidence in my proposed plan.

Thanks, y'all!
 

drifty325i

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What size wires and how long are they between the battery and the Victron?
 

interestingfellow

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Aug 5, 2020
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They will be less than 5ft
Probably less than 3 ft, tbh.

I am planning on 1/0, once I figure out the setup/wiring diagram.
 

interestingfellow

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Aug 5, 2020
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Multiplus calls for 300 and 50mm2 wire, which is real close to 1/0.

I had several folks in the diy solar forum fb group recomend going 400.

But even then, that's for a catastrophic failure so my trailer doesn't burn down. I'm okay with using a 300a fuse, I'm more concerned about the soundness of running the victron through the 250 Daly BMS.
 

interestingfellow

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It's also funny that you should say that 1/0 wire is too large for a 300 amp type T fuse... 90% of the 300a-400a holders I found were for 4 gauge wire!
 

interestingfellow

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So, 300a Class T between the BMS and the battery
and then what???/ 250 ANL between the Multiplus and the BMS?
 

pau1phi11ips

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Dec 17, 2019
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I'm using a Multiplus II 24/3000. I have a 8S 280Ah LiFePO4 battery with a 120A Daly BMS.

I'm still converting the van but I've built the battery. I was going to run everything through the BMS apart the Multiplus which will be connected straight to the battery, well the Shunt but you get the jist.

I'm going to use an assistant on the Multiplus to disable charging/discharging based on the BMS status.
 

DJSmiley

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Aug 13, 2020
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Wire thickness isn't the main issue usually for the fuse ratings.

While a (eg) 6AWG wire can handle 50-60A without problems considering the generated heat, it's generally not recommended due to voltage drop. Especially with a low-voltage system, 1V can already make a huge difference. On a 12V system that's almost a 10% loss.

This, along with startup currents for some loads, might cause the inverter to shutdown due to 'empty battery': The voltage drop caused by the inrush current will let it think the battery is flat. Thats the primary reason you're using those thick wires.

Shorter cable runs can be done with smaller wire gauges, while long runs require thicker wires to compensate for the loss. This is also the reason why some multiplus invertors have multiple connectors, so you can run wires in parallel.

It's also funny that you should say that 1/0 wire is too large for a 300 amp type T fuse... 90% of the 300a-400a holders I found were for 4 gauge wire!

4/0 wire = 120mm2.. That's a massive cable! I personally don't go over 70mm2 (2/0) wire since thats at least some way workable. Thick wires are a PITA to handle. I'd prefer running 2x 50mm2 over 1x 95mm2. Also, make sure you go for flexible wires, there are multiple classes of flexibility.
Especially in an environment with vibrations I'd prefer the more flexible ones, less stress on the cable lugs.

The bluesea holders eg handle up to 4/0 wire, M10 thread, so a very decent cable lug will fit.

For the 24/3000 Multiplus (I recently installed one) I used 50mm2 cables. The multiplus was placed close to the batteries (approx 1.5m - 4 ft) so no need to run thicker wires (also as indicated in Victrons manual)

Most important: Use proper crimping tools. Not the $15 hammer things, but use proper ones, especially if you're going to use high amps for longer times.
 

interestingfellow

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Aug 5, 2020
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Thank you!
So what fuse would you recommend between the Daly 250 and batteries?
And between the Daly 250 BMS and the Victron 24/3000?
Thank you again!
4/0 wire = 120mm2.. That's a massive cable!
Oh, no. Not 4/0 awg but "4" awg wire. As in 25mm2
 

pau1phi11ips

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Dec 17, 2019
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32
Thank you!
So what fuse would you recommend between the Daly 250 and batteries?
And between the Daly 250 BMS and the Victron 24/3000?
Thank you again!

Oh, no. Not 4/0 awg but "4" awg wire. As in 25mm2
I'm using 50mm² cable between the battery and the 24/3000, it's probably overkill but wanted to reduce the losses as much as possible. Would possibly be using the full 3000VA for short periods of time.
 
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