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jimbo47 avatar image
jimbo47 asked

New Install Wiring Questions: Multiplus 3K, Cerbo GX, Lynx Shunt Can

I have a new 12v system I’m installing consisting of 6x100Ah Battle born batteries, a Multiplus 3000 Inverter/Charger, Lynx Distribution system with 1000Amp shunt can, and a Cerbo GX. I have some question on the wiring below.


The batteries will be connected into two Lynx distribution panels connected together. They will be connected into ports 2-7. I will connect the positive on port 1 (with 400A fuse) and negative port 8 to carry the load to a 400A single pole on/off switch and the Shunt can left side leads.


That run of 4|0 AWG (107 mm2) will be about 4-5ft for each cable from the Lynx to the shunt. Each battery will connect in with 2|0 AWG (67.4 mm2) 24” or so (all equal length).



On the right side of the shunt can will be two more lynx distributors to feed the system. One of these runs will go to the multiplus.



I plan to connect the Multiplus to the Cerbo GX over the VE.Bus port (RJ45). I will connect the shunt to the VE.Can port using RJ45 and one terminator on the other port of each device.



A few questions on the other sensors/wires:


Is it possible for Cerbo GX to be powered via VE.Direct (Power over Ethernet) rather than use the included fused connection?


I have the temp sense wire that came with the inverter, and I see the instructions about creating a v-sense 18AWG cable in the forum, but I am confused about where to connect these in and to which device(s).


The shunt can will determine the voltage on the input from the battery bank at the left side terminals but there is more cable to account for (5 feet of 4|0 AWG plus the runs to the batteries). I could wire the v-sense on the port 1 and port 8 +/- sides of the battery bank lynx setup which I think would be the place to measure.


What about the temp sense, and should the temp sense be connected to the shunt can and it will inform the rest of the devices about the data? Otherwise I would be looking at running t-sense to the shunt and the multiples separate.


Regarding the RJ10 cables to connect the shunt to the lynx distributors, should these be connected within each location in my setup ie connect the shunt and load side distributors together, and then connect the two lynx that are together in the battery bank to each other, but not all together?


Please advise on the best way to set this up. Thank you kindly for any information provided.



cerbo gxmultiplus ve.busVE.Can
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keithbrown avatar image keithbrown commented ·
2 feet of 00 AWG from each battery to Lynx bus is FINE. Don't forget to put fuses as close as possible to the battery positive terminal. If you are using a Lynx shunt as Victron recommends, it should be directly attached to your battery Lynx bus bars. That's how Lynx is supposed to work. Everything in and out should be on the opposite side of the shunt. I suppose this should include your Cerbo GX power.


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2 Answers
Alexandra avatar image
Alexandra answered ·

@jimbo47

The cerbo must be powered with the provided fused cable. Preferably from the shunt, the connection is shown in the manual.

The temperature sense wire for the Inverter can be installed in the t sense terminals see the appendix A in the manual for your inverter. Or it can connect to the cerbo to the temperature inputs. The lynx manual also links you to the Quattro sensor so is compatible to plug in there as well.

I would choose a bigger diameter DC cabling. A 12v system needs the bigger stuff to compensate for voltage drop over length and under load.

3000w at full chat will draw 250A continuous. But longer lengths means that in reality will be mich higher due to voltage drop and resistance. I have 95mm² (300Amp rated) on mine and its run is just over 3.5m to the furthest battery. You will avoid problems that way. Not so much from battery to shunt but between it all and up to the inverter.

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jimbo47 avatar image
jimbo47 answered ·

@Alexandra


Thank you very much for the response. I have updated the OP to reflect the cabling, I intended to show 0000 AWG (107 sq. mm) from Battery bank to Shunt, and to connect the multiplus into the system. I would run each battery connected via 00 AWG (67.4 sq. mm) cable fused at 200A (six in parallel connection).


I appreciate the info about the power connection for Cerbo, I reviewed the shunt manual and it looks like I should connect the power to the Distributor on the right side of the shunt can.


Regarding the t-sense wire I see it connected from the shunt can directly to one of the “center” batteries in the bank, negative terminal. I will plan to do this.


Is there any benefit to wiring it differently or additional t-sense wires to the inverter and/or cerbo GX versus it getting this information from the shunt can?


Would v-sense wires be positioned on the battery bank side lynx distributor (+/- connection to shunt are on opposite ends)?


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Alexandra avatar image Alexandra ♦ commented ·
@jimbo47

Are you gapping the batteries at all? Or making one solid mass? The t sense is usually in the centre of the bank. With lithium there is not much temperature compensation in charging (just the low temp charhing concern), it was nore critical in lead acid based systems as it affected voltage targets.

Which component it reports through just changes the way it is recorded and how it is displayed on the VRM, which widget you use on the Advanced tab as far as I can see. It usually would be choosen on ease of wiring.

The V sense would need to be in a position where it measure the overall bank voltage as close as you can to the bank. So however that works out in your setup.

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jimbo47 avatar image jimbo47 Alexandra ♦ commented ·

@Alexandra

The battery bank will consist of six 100Ah batteries connected to two lynx distributors. I plan to connect the six batteries in the "middle", terminals 2 to 7. The positive and negative will connect with 67.4 sq mm cable (00 AWG) probably 24" per cable (all will be identical length). The bank will be connected to the shunt can via 107 sq mm (0000 AWG) about 1.5m for positive and the same negative (the positive will have the on/off switch inline - the fuse will be built into the shunt can as well as another 400amp fuse in the lynx distributor to connect the positive terminal to the positive buss bar. The positive and negative ends connected to the battery bank will be on opposite ends of the battery bank lynx distributor (terminal 1 and 8) and this is where it makes sense to connect the V-sense wires to capture the full bank voltage as close to the bank as possible.


Thank you again for all of the great information!


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jimbo47 avatar image jimbo47 jimbo47 commented ·
Note: I plan to fuse each individual battery with 200Amp fuses, while the positive terminal going to the shunt will be fused with 400amp like the shunt/system itself.
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