I’m planning on upgrading our travel trailer camper by removing the existing converter but still using the existing AC and DC distribution panels and not much else. I will also be replacing the existing 100watt solar panel and PWM controller. I will not be charging from the tow vehicle at all. I’m looking for a sanity check if I missed something. The wire runs from battery to lynx, multiplus to lynx, and MPPT to lynx are all very short (1-3 feet) and the only longer runs are to the existing AC and DC distribution panels of about 15 feet. Thanks for any feedback! Here is my design:
Updated the drawing to add in proper grounds, changed the lynx power ins to a Class T power in and a Distributor to both add and simplify fusing, and defined the solar panels better after some feedback.
Updated again to add in some small bus bars to branch off from the lynx distributor to handle smaller DC loads and not have to add in another lynx. This also gave me a place to connect in the cerbo for power.
Whats the reason for this? Generally using series strings is beneficial.
Whats the reason for using two shunts instead of just one? Also the batteries have their BMS so depending on what they provide on information not even one shunt would be necessary, and it looks like some communication wire is drawn between batteries and cerbo.
Theres no earthing/groudin drawn, usually you would ground devices to the ehicle frame.
If the generator is permanently installed you could consider using a Quattro instead of an MP and use the ACin2 for the generator
I wrote that wrong, they will be in series/parallel (2x2) to run at 36V to lower the current so I didn’t have to try to run too high a gauge and to leverage some of the existing wiring from the panels (so either 10 or 12 gauge whatever they come with into 2 connectors and then 6/2 the rest of the way to the MPPT. Also from what I understand there is a bit of a tradeoff in series vs parallel (light conditions (or shade) on each panel having a bigger impact on series for instance) and doing series/parallel gets some of the best of both worlds while minimizing the downsides of each.
Most of what I’ve read says to use the shunts for SoC instead of relying on the BMS (though no idea how much of that is just marketing speak). I have two shunts so I can monitor each battery uniquely. I also already had these reclaimed from a different project so figured might as well use them.
The batteries I’m using are supported by the Cerbo and have CAN ports to connect to it. I believe you can daisy change from battery to battery to the Cerbo but I’m trying to keep each battery in its own little world with no dependency on the other being there.
I’ll add in the ground wire so I don’t forget when it comes time to actually wire it all.
The generator is just a little portable dual fuel unit (propane/gas) I keep in the two vehicle. I’ll only pull it out and use it if necessary when not on shore power and not getting enough charge from solar (so hopefully mostly a last resort).
I’m also still reading up on what I need to do to keep the batteries balanced.
Fuses protect the WIRING not the device so fusing the lines between the Lynx and the MPPT and DC load panel should be at the Lynx end. Consider the Lynx Out for these connections since they have space for fuses.
Stock GX devices (Cerbo in this case) assume only one shunt for the battery bank. There are third party extensions like Battery Aggregator that will combine info from multiple batteries but I do not know if the extensions work with multiple SmartShunts.
All devices, not just the Multi need chassis ground connections. Typically, the DC negative has a single ground connection somewhere and should be close to the main distribution (Lynx in this case). MPPT also needs a chassis ground connection. Solar panel frames also. DC and AC grounds should be connected at a single point somewhere.
Consider a SmartShunt for the DC loads. The GX device will calculate a DC load value but it can be incorrect especially with varying power levels in the system.
Thanks for your input! I updated my Diagram at the top (I’ll keep replacing it so once it is all happy it can serve as a reference.
I changed out the two Lynx Power In with a Lynx Class T Power in (and moved the Class T fuses out of dedicated blocks and into it) with only the batteries into it and the other to a Lynx Distributor with Mega Fuses for the connections to the MPii, MPPT and existing DC distribution panel.
I added in 2 additional bus bars to handle some of the lower load DC. I still have a mega fuse going to the largest one on it. It gave me place to connect the cerbo for power since I was out of lynx lugs. This also give me some spots if I want to connect in some pwm fans with their own small fuses inline like the cerbo has. If I ever needed to add in anything higher load I’d put in another single megafuse block off of there (or consolidate into another lynx distributor but that is unlikely to be needed).
On the Cerbo I’m planning to use the battery agregator script to combine the shunts into an aggregate for the display but still be able to get the data for either battery alone.
I added in a ground bus and connected the Lynx Distributor, the MPii chassis, the MPPT chassis, and the solar panel frames to it and then the bus to the camper chassis ground. Technically the actual physical connection of the frames will use the existing ground connection on the top of the camper (it came pre wired with a 100watt panel and a cheap PWM and I’m replacing both with new panels and the MPPT) but logically it is the same as it all ends up connecting to the camper chassis ground so representing it that way is ok.
The MPii does the AC ground through it’s chassis ground I believe? So this brings the AC and DC to a common ground point.
I thought about a shunt for the DC loads but they are not very big and pretty constant, I’m more concerned about inverter load for AC when not using any shore power (grid or generator). I don’t plan to run AirCon (not that crazy) but there is a micro, a water kettle, a CPAP, charging random things that I can’t get a DC plug for (or silly expensive but man does it suck to convert DC to AC just to convert it back to DC!).
Great feedback! especially the grounding and rethinking the Lynxes.
