Overkill electric

[Joe917]

Fire problem.
I have just looked at this again.
I assumed the fuses on the bus bar were fusung the cables fed from the bus bar. Now it appears those fuses are on the cables coming from the battery, correct?
The cables need to be fused where they leave the battery and where they leave the bar. If you only had one wire from the battery connected to one or more cables the same gauge you would only have to fuse at the battery(until you connect to smaller wires).
Which brings us to the stud with what appears to be a large supply cable connected to a number of smaller wires with no fusing.

 

[taliv]

This is still pretty close to accurate.

there are two sets of bus bars. One main one 600a with 100a fuses to each battery. And another that connects all the chargers. There is a breaker on the charger bus that goes to each charger. The second pic shows what is essentially my distribution for loads. Those are the two poles or studs you see in the pic. All wires connected to the positive stud have a fuse. However the ones you see go just out of the pic to the right to a fuse box that was riveted at the factory through the wall so I chose not to try to relocate it.

 

[Joe917]

Your fuses need to protect the wire. the fuses at the bus bar on the battery cables are at the wrong end of the wire, they need to be at the battery terminals.
You are supplying two cables capable of 100 Amps each to a bus bar supplying two cables also capable of 100 amps each BUT that is 200 Amps in possibly going out on only one 100 Amp conductor. This is where you also need to fuse the wires leaving the bus bar. Where are the fuses on the stud?
Fuses need to be at the start of the positive run to protect the wire from shorting, a fuse at the end of the run does nothing.
Any time you go to a smaller wire you need to fuse again or fuse the entire circuit protecting the smallest wire.

 

[taliv]

That’s what I thought too but then others said you fuse on the bus bar when you have multiple batteries. And the victron reference design fuses on the bar instead of the battery terminals.

 

[taliv]

so, i'm awaiting the delivery (hopefully tuesday) of the victron smartshunt 500a which will give me some idea how much juice i have left. hopefully.

but i took the trailer out this weekend and a bit of hiking on the AT. I brought the girlfriend to give the trailer an electrical workout.

my electric budget was
40AH / day for the fridge/freezer x 2 days = 80AH
and we brought the 1500w keurig and had 4 cups of coffee and tea, which i conservatively estimated at 10Ah each = 40Ah
and the 1000w hair dryer for 15 min or so was around 20Ah
plus misc LED lights and charging phones which was maybe another 2Ah as we really weren't on them much at all

so i figured i was somewhere around 142AH of consumption for the weekend, conservatively.
We were camping in a narrow field between two hills with extremely tall trees, so we probably only had about 40 deg sky, but my crappy panel managed to peak at 100w and put a total of 330Wh back into the batteries according to the victron mppt, which i believe is about 25Ah

so net, 117 Ah down. When I got home, I plugged the victron ip67 in and 4 hours and change later, it completed the bulk phase having put 104.5 Ah in, and several hours later, the absorption phase had stuffed another 3.6 Ah in, so around 108Ah, just 8% shy of my estimate of 117Ah.
I am probably not that good at estimating but i assume the bulk of the error was my coffee estimate was based on 5 min run time and i haven't actually timed it but it's probably half that.


anyways, a question:
i drew the diagram above before someone here explained the smart shunt goes on the negative side. again, this is a pic of the negative bus, where i currently have 2 batteries and will install the 3rd one shortly. the batteries connect to the left 2, and soon 3 posts.
there are two wires on the right post. one goes to all the loads and the other to all the chargers.
so my question is, when i install the smartshunt, I assume i will make a jumper that goes from the right post to the "battery minus" post of the shunt, and then the two cables in the pic will move to the "system" post of the shunt? doing this really only exposes the shunt to the net current flow in or out of the battery, right? wouldn't it be more interesting to measure the current on the charging cable (always flowing from charger to batteries) and load cable (always flowing from batteries to loads) individually in order to get a better view?

put another way, this shunt is really a "battery monitor" rather than a "system monitor" because it only shows what's going in and out of the battery, not how much load i'm really using or how much i'm really charging. in this config, if some charger is charging at 10a and some load is drawing 4a, the shunt is going to see a net of 6a flowing into the battery, which will make it seem like it's just not charging as fast as it could. or if the load jumps to 12a, then it will see a net of 2a flowing out and it will look like it's not charging at all, when in fact the charger is still pumping 10a into the system.
obviously, the battery's perspective is most useful. but is there some way to measure or calculate the actual load and charging currents?
i'd think that would be possible to measure the charging currents coming from the victron chargers which participate in the v network and calculate the load based on subtracting what the shunt sees.

 

[Joe917]

You need to tie your battery negs together, then shunt, then neg bus. You need battery information more than charging source info.

 

[Alloy]

That’s what I thought too but then others said you fuse on the bus bar when you have multiple batteries. And the victron reference design fuses on the bar instead of the battery terminals.

Fusing closest to the battery is best but the fuses will still prorect the wire unless the wire is cut/worn along the length.

 

[Joe917]

Fusing closest to the battery is best but the fuses will still prorect the wire unless the wire is cut/worn along the length.

Fusing needs to protect from overload AND shorting. Only fusing at the start of the positive run protects the circuit from a short.

 

[taliv]

Pretty happy with the 3x160w panels doing what they’re supposed to on a cloudy day. Can’t ask for much more than 29.90 amps out of a device rated to 30 amps.

 

[dreadlocks]

Can’t ask for much more than 29.90 amps out of a device rated to 30 amps.

How about 30A?

 

[taliv]

Dang it! Maybe I should shine a flashlight on it. Give it that extra .1
(If it said 30.00a) I’d assume it was lying to me and not actually measuring it)
seriously thanks a ton for steering me towards victron and answering a lot of questions