Wiring diagram for converted bus.

Here's a proposed wiring diagram for a bus I've converted to an RV. Only thing I'm not really sure about is whether to put circuit breakers between solar panels and charge controller. I already have 4 of the batteries installed and am using them. Two more batteries to be picked up the end of the month. All solar is purchased awaiting install.


Not included in this diagram is the heated pad circuit for keeping the batteries warm and wiring for the latching contactor that will unhook batteries in case of heat fail. Latching contactor also has a switch in cabin to manually unhook batteries for everything. Start battery is included because the inverter/charger has an extra circuit to maintain the start battery.

You may want to put the strings of panels into a combiner box, which puts each string on a fuse/circuit breaker. When you parallel combine panels or strings of panels, if one panel or string develops an issue, it can be back fed by the combined current of all the other panels/strings...that much current can be greater than the wire and panel can handle, creating a fire hazard.
Also, the negative wire from the solar charge controller has to go to the other side of the shunt, or the solar charge current won't be measured by the battery gauge.
I'd also put the 150 amp fuses at the battery end of the connection cables, that way those connection cables are protected by the fuse as well.
The start battery has no fusing for it's wiring, that can be a fire hazard.

Hi there,

First of all, you indeed can use a 3-string combiner box, like this (https://www.solacity.com/product/midnite-solar-mnpv3/) with 3 x 15 Amp DC breakers. It helps when you need to replace or just turn off the PV side ( it is unsafe to unplug the panels if they are under the load!). Second, the shunt should be as is. It measures - battery voltage, current, power, ampere-hours consumed and state of charge, and also remaining time at the current rate of discharge (taken from the product manual -Victron BMV - 700 series) and it doesn't measure a charging current. The charge controller itself can communicate with the app installed on a cell phone. Last, between the panels and the charge controller you can use a 10AWG wire, 2 AWG is overkill, between the charge controller and the battery bank you can leave as is.

Vlad-Solacity said:

Second, the shunt should be as is. It measures - battery voltage, current, power, ampere-hours consumed and state of charge, and also remaining time at the current rate of discharge (taken from the product manual -Victron BMV - 700 series) and it doesn't measure a charging current.

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This is wrong. To properly measure battery state of charge, ALL currents going into or out of the battery must go through the shunt to be measured, this includes the solar charging current.

PHoganDive said:

This is wrong. To properly measure battery state of charge, ALL currents going into or out of the battery must go through the shunt to be measured, this includes the solar charging current.

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Yes, you are right! Disregard my comment regarding the shunt!
Thanks

PHoganDive said:

Also, the negative wire from the solar charge controller has to go to the other side of the shunt, or the solar charge current won't be measured by the battery gauge.

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Yea, I missed that, thanks for pointing it out.

PHoganDive said:

I'd also put the 150 amp fuses at the battery end of the connection cables, that way those connection cables are protected by the fuse as well.

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That's probably right, however, I've never seen that configuration in anything I've ever worked on. Heavy truck, bus or automotive. Probably because it's just too hard to do to mount the fuses near or on the battery terminal. Generally there is some sort of fuse box with a cable running from the battery to said fuse box. I guess, at some point, you just have to trust your capability to make proper cables.

Vlad-Solacity said:

It measures - battery voltage, current, power, ampere-hours consumed and state of charge, and also remaining time at the current rate of discharge (taken from the product manual -Victron BMV - 700 series) and it doesn't measure a charging current.

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They do measure charging current. Without the solar controller, just hooked to the alternator as shown in the diagram, mine shows negative amps when engine is not running and positive amps when it is. I'm pretty sure PHoganDive is right on that one. I'll diagram to that.