Fridge to battery?

[Blue~Go]

I want to expand on something, but in case you have already read the above post, I'll put it here instead of editing.

Okay, so now we can ignore (but just leave in place) the negative jumpers from the brown box to the frame. They aren't really carrying any of your chassis-grouded Chinook loads back to the battery bank.

So now let's look at the positive path, which includes the super long skinny wire (8AWG) that goes on a circuitous path from the brown box fuses to the battery positive.

The full path goes like this:

-- House battery positive post
-- Long skinny (red) main feed wire to brown box
-- Longer, skinnier mult-colored wires leading to the loads (lights, water pump, etc.)
-- Skinny white wires approximately equivalent to the above mult-colored wires from the loads back down to the frame in the rear
-- Through the frame
-- Through the ~3' long jumper from frame to negative battery post.

So already here we can see that the positive and negative "halves" of the chassis-grounded circuits are not exactly even. The negative legs have a slight advantage because the frame is like a really fat wire. So in effect, as-wired, the positive run is longer and "thinner" and has more voltage drop. Hence it's reasonable to grab the low-hanging fruit and disconnect the long, skinny, red feed wire from battery positive to brown box and replace it with a shorter/fatter red wire (say 6AWG running along the side wall under the couch in loom). It's impossible to say if things are exactly balanced because how do you calculate the frame and all those chassis ground connnections*? But that's okay, you can still thwack off a big chunk of voltage drop. Just make sure that your new jumper from battery neg (or shunt neg) to frame is larger. No need to try to calculate it down to the nearest amp --- just make it something like 2AWG or so. (Mine is 1/0 but that is because it is also carrying the "negative" of my self-jump-start/alternator wire, so it needs to be fused to 250a and smaller wire won't do that.)

OTOH, you could also reason that, since/if you are removing the charging amps from that long, skinny wire, you could leave it as-is. Just know that when you add a proper fuse to the main battery positive(s), you always need to fuse for the "weakest" wire. So in this case, 8AWG with the original wire. And it will still have more voltage drop than you'd like most likely (of course this depends on how many and which loads you are running concurrently).

*Speaking of which, it would be a good idea to slide under the Chinook and check on/clean/tighten those chassis grounds (shown in the previous post in the colored boxes). They live a hard life out there, and a "bad ground" has caused many a mystery problem in electrical systems.

This is one reason that if I'm adding something completely new, I tend to run a positive/negative pair right back to my busses (through appropriate fuse), and don't heap on more chassis grounds.

[Rhythmtone]

This is all amazingly helpful info, thank you.

I'm trying to decide but as I think about it, I'm starting to lean back towards the charger/inverter option - because if you recall, I wanted a TV in the front, on battery, in addition to electrical upgrades.

I'm considering a Victron Multiplus 12/800/35 and being done with it - it's not as smart at IP22 it seems, maybe I can add shunts or BMS, and it has temperature sense ports, etc.

The unit would live under the sink or nearby - I'm not sure if I want to run 2 sets of AC back and fourth (let's say it lives by the LDV, which has the least space, or in the battery drawer, which has the longest AC runs x2. I could do under the couch in the middle or whatever but it kind of makes sense to put it at one end to the other - I might just do under the sink, as designed, and run 4AWG, as it is sized for, behind the couch and down into the original battery drawer, as was originally planned.

This doesn't upgrade up my DC too much, but solves the inverter project as well in one swoop, and also gives me a whole house inverter setup - and which I don't need, but it makes sense to tap into the AC at the breakers, rather than running a separate inverter.

Let me know what you think - I COULD move it close or into the battery drawer, but it's a lot more wires to run.

If you have the best idea of where to tap in for my DC panel, that would also be appreciated. Just share the posts on the charger battery connection?

Thanks

[Blue~Go]

I'm trying to decide but as I think about it, I'm starting to lean back towards the charger/inverter option - because if you recall, I wanted a TV in the front, on battery, in addition to electrical upgrades.

I'm considering a Victron Multiplus 12/800/35 and being done with it - it's not as smart at IP22 it seems, maybe I can add shunts or BMS, and it has temperature sense ports, etc.

I haven't installed a Multiplus but according to the documentation it does not participate in a Smart Network (presuming that's what you mean by not being as "smart.") I suppose that's because at that stage of the game (more advanced/complicated/$$ system) they expect you to have a Cerbo GX (and not simply rely on the Victron Connect app/bluetooth/Smart Network as you can with the MPPT/BMV/IP22 type setup) and then the Cerbo GX does the comms. At least this is how I read it.

Of course Cerbo GX has some advantages: Cool optional touch screen, access to VRM Portal (so you can monitor and communicate over the web vs. needing to be within range of bluetooth) etc. But it's a level up for sure, cost and complication-wise.

The unit would live under the sink or nearby - I'm not sure if I want to run 2 sets of AC back and fourth (let's say it lives by the LDV, which has the least space, or in the battery drawer, which has the longest AC runs x2. I could do under the couch in the middle or whatever but it kind of makes sense to put it at one end to the other - I might just do under the sink, as designed, and run 4AWG, as it is sized for, behind the couch and down into the original battery drawer, as was originally planned.

That's going to be a bit of a thing. Let's do some calcs for if you put it basically under the sink. I don't think this is going to be practical, but let's run through it. The Multiplus 12/800/35 has a peak power draw of 1600w, so one would typically wire with that possibility in mind. They likely ask for around a 160 amp fuse, so that would mean at least 1AWG wire. You can get 1AWG but likely you would just go ahead and use 1/0 for a little cushion and because it's more common. With 1AWG you could fuse to 171 amps max. 2AWG is too small because its ampacity is 147 amps. This is presuming you use 105ºC rated wire and it is not bundled with more than two other wires. This probably won't be the deciding factor though, so let's have a look at Voltage Drop.

I see they recommend 25mm cable, which is a bit larger than 4AWG (but not as large as 2AWG). But I think we'll find that the voltage drop if putting inverter under sink is too much anyway so it's all a moot point. Number one priority for an Inverter is typically to put it RIGHT NEXT TO the batteries (or very close). Likely that means though that the terminals will not accept larger than 4AWG, so you would need to wire to power posts right next to the inverter, then "downshift" to 4AWG cable into the inverter. Slight hassle But do note they list that as for a maximum of a 5 meter run, and that's about 16'. You would have nearly twice that at around 30' So you'd need much larger cables.

On to voltage drop:

1600 watts at say 11.5 volts is roughly 140 amps. Let's say you put the inverter charger under the sink. Now your DC wire run will be around 15' one-way/30' round trip (to the batteries). So let's look at 140 amps.

That's 10% voltage drop which is way too high to even consider. I would shoot for 2% or less. That would mean 4/0AWG cable. 4/0 is very expensive and huge (I know, because that's what I used for the wires from my 60 amp charger (under the sink) to my battery bank (under the couch) to keep voltage drop reasonable. You are talking a much larger amp load and a much longer distance.

In reality, I would say this is not viable. The inverter would need to go closer to the batteries. Or move the batteries closer to the inverter (say under the couch, though you will still likely want very large wires as I used for my 60 amp charger (which I mounted on the plywood wall that separates the shower from the kitchen, basically above the box that the shore power cable lives in). Even with batteries under the couch that was like a 9' run by the time all was said and done.

Basically, you always want to make it so the inverter/charger is as close to the batteries (but not above them) as possible. Like REALLY close. Or use a smaller inverter and smaller charger, so the loads are not as high and the distance doesn't kill you as much. Smaller inverters tend to have a smaller tare load too (i.e. load just from them being on).

This doesn't upgrade up my DC too much, but solves the inverter project as well in one swoop, and also gives me a whole house inverter setup - and which I don't need, but it makes sense to tap into the AC at the breakers, rather than running a separate inverter.

Of course either way (separate charger and inverter or inverter/charger) you will be tapping into AC at the breakers, because even a stand-alone shore charger would be wired to the "charger" AC breaker. I'm not so sure I'd go for an Inverter/charger combo in your situation. At least I have not heard you mention any use case that really takes advantage of the extra inverter charger features. (Power assist, larger AC loads, etc.)

If you have the best idea of where to tap in for my DC panel, that would also be appreciated. Just share the posts on the charger battery connection?

Tap into the DC panel for which thing? I ask because I don't think there is a specific DC charger connection on the brown box. Probably why Chinook just used the one long skiiiiiiny 8AWG for charging AND loads. Anyway, your charging will be going to the house batteries, not the brown box.

eg, if you used an IP22, you would tap into the AC connection at the AC charger breaker, then the DC wires would go right from the charger to your positive fused bus/negative house battery bus. So no DC connection at brown box or DC panel. Or am I misunderstanding your question?

[Rhythmtone]

Thanks for the reply,
By "Smart" I meant a in a general way, I understand that that was not super clear haha. As in, a charger (or combo) that is fully programmable, with temperature sensing, and CAN just be basically managed with Bluetooth/app control. From what I've read and been told the Multiplus could do this with a smart shunt (for the batteries) and a VE smart dongle (for control) - if you want to get fancy then it's the 712 for battery monitoring and their "digital multi control panel" for control/monitoring of the charger - difference being phone/Bluetooth/app management method instead of surface panels, but again, same functionality, as far as management and control, as IP22 and similar setups, as I understand it.

I see your point again about the wire runs - as I understand it, the charger/inverter would have input from the shore power (via breaker) but also AC output to the rest of the house AC outlets (and breakers) - but I guess that I have not fully looked at the wiring topology of doing this - I am only visualizing it based on other designs.

Let's say I put this inverter charger by the LVD -solves DC length and gauge problem, as we talked about in a previous post. As I understand it, that would be 2 sets of AC wire runs to/from the brown box to achieve what I described above (input/output) - if this won't work, then another alternative is just put a standalone outlet in the over cab panel that receives AC from the Multiplus - and forget running the entire house from the inverter. The cost is very similar, so it's just the topology and where/how to run the AC wiring that I'm still thinking about.

For the DC question, I just meant where to hook up for the house DC panel, but I think that answer will become more clear as the build comes together, haha.

Thanks again,
Dave