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leftcoastman35 avatar image
leftcoastman35 asked

VE.BUS BMS charge and load disconnect issues and possible solutions

I have installed and operated a mostly Victron Lithium system on my sailboat for a little over a year now. The system components are described at the bottom of the post. Apologies in advance as I am not an engineer. From the beginning, I have had trouble getting two problems solved, both related to the Ve.Bus BMS:


(1) Load disconnect - I tried to use the Victron BP220 but it melted within a week. The boat draws far more current than the BP220 can handle and moreover, the original wiring is such that it would take me many many many hours to separate the "power supply" wires from the "control circuit" wires.

I have been searching for a possible solution, but Victron does not provide a bi-stable relay that can handle the currents required by my boat's electrical system.

I have located the Blue Sea ML Solenoid (500 amps continuous) and would like some input on whether it's the right product and if so, ways to wire it correctly.

https://www.bluesea.com/products/7703/ML_Solenoid_-_24V_DC_500A

Instructions are below

http://assets.bluesea.com/files/resources/instructions/990180170.pdf

My understanding is that it's a bi-stable relay that includes a switch that applies +ve momentarily to one terminal to close the solenoid and +ve to a different terminal to open the solenoid.

The VE.Bus BMS load disconnect, however, is normally high (roughly supply voltage minus 1v) and goes open circuit (zero volts) when load needs to be disconnected.

Is there a way to integrate the Blue Sea relay into my system? Or is there a Victron product out there to enable load disconnect that I didn't see?

(2) Charge disconnect - The VE.BMS Charge Disconnect wire is controlling the Bluesolar MPPT 150/35 and the Skylla-i 24/80 (3) using the appropriate Victron wires. This appears to work properly so that if I unplug the Charge Disconnect wire from the VE.BMS, charging instantly stops on both the Bluesolar and the Skylla.

We also need this Charge Disconnect (CD) to control the Mastervolt Alpha Pro II, the regulator for our Mastervolt Alpha 24/110 alternator. The Mastervolt Alpha Pro II charge controller has a “reg-on” wire that switches the controller on if there is “high” voltage and switches it off if there is open circuit. Normally, in a standard installation that does not include any Victron components, a relay controlled by the engine ignition circuit connects/disconnects the reg-on wire to battery positive. Knowing that the current limit on the Charge Disconnect wire is 10 mA, we used a Hella 24v 10/20A relay instead of connecting the CD wire directly to the Mastervolt Alpha Pro II. A multimeter indicates that the Hella relay draws 7mA. However, the Charge Disconnect does not seem to provide enough current to power the relay, even when Bluesolar and Skylla are disconnected from the circuit. When we try to power the relay with the Charge Disconnect wire, the voltage on the CD wire drops to a little over 3 volts (it’s normally around 26.3v). I believe this indicates the Ve.BUS BMS isn't providing enough current to trigger the Hella relay. I even tried a 12v relay - didn't work.

We do not have the negative wire attached to the VE-BMS per Victron recommendations to prevent ground loops and we have connected, via RJ-45 to the Quattro.

Can I use a Victron Cyrix Li-CT to connect/disconnect this Mastervolt Reg-On wire? In other words, can I wire the VE.Bus BMS charge disconnect wire to terminal 85 on the Cyrix Li-CT and terminal 30 to the Lifepo4 batteries and the Mastervolt Reg-On wire to terminal 87?

Instructions for the Alpha Pro II, relevant page is 12

https://productimageserver.com/literature/ownersManual/69993OM.pdf



_______________

Currently the system on my sailboat includes the following components:

Batteries: SIX Victron Smart 12.8v/150ah batteries, serial to create 24v and parallel to create 450ah.

BMS: VE.Bus BMS

Inverter/Charger: Quattro 24/5000/120

Battery Monitor: BMV-712

Solar Charger: BlueSolar MPPT 150/35
Second Charger: Skylla-i 24/80 (3)
Alternator: Mastervolt Alpha 24/110 alternator with Alpha Pro II charge controller

Here are all the connections:

- Quattro is connected to the VE.Bus BMS using a RJ45 cable
- BlueSolar MPPT 150/35 is to the VE.Bus BMS using a VE.Direct non inverting remote on-off cable (ASS030550300)
- Skylla remote on/off input is connected to the VE.Bus BMS (‘charge disconnect’ output) with a Skylla-i remote on-off cable (ASS030550400)
- Mastervolt Alpha Pro II charge controller has a “reg-on” wire that switches the controller on if there is “high” voltage and switches it off if there is open circuit.
Lithium BatteryBMS
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2 Answers
Gary Pacey avatar image
Gary Pacey answered ·

Could you please provide details of the vessel loads connected to the BP 220? There are alternate means to control high current loads such as bow thrusters, windlass and sheet winches.

The BP would be used to control loads connected to the house panel which I would expect to be under 50-amps. For say an anchor windlass, a house panel circuit breaker would supply power to the windlass up/down control circuit and power to the windlass solenoid would come directly from battery positive via a fuse or circuit breaker. If the BP shuts off the power, then the windlass solenoid can not operate.

The same strategy is used sheet winches, thrusters and so on.

As for the Mastervolt regulator, have the ignition circuit power a relay (to the coil) when the engine is running. Feed the Charge Disconnect signal to the regulator via the relay contacts. You will need to check the regulator spec to ensure that the control signal is low power.

Please confirm the loads that you are trying to control that are causing the BP to "melt".

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leftcoastman35 avatar image leftcoastman35 commented ·

Gary, that is a possible solution. Earlier the marine electrician connected ALL loads through the BP-220. Even with a 600 amp peak load capacity, the BP-220 melted the moment I tried to operate the Opacmare passerelle. That motor is below 3000 watts, I believe.


Now I just need to trace the wires from the main battery switch to the 24v house panel. I don't like the fact that a low voltage load disconnect would cut off my bilge pump, but you can't win them all.


Regarding the charge disconnect, an additional complication is that the engine/ignition is 12v and the house batteries are 24v. With the Mastervolt regulator, the "reg-on" wire is the voltage sense wire, so it needs to go to the lifepo4 battery. The Ve-bus BMS charge disconnect signal is battery voltage minus 1v, so that wouldn't work.


What is was trying to do is have the relay powered/controlled by the charge disconnect wire from the Victron VE.BUS BMS. When the Ve.bus BMS is saying that all is ok, it will energize the relay and the Mastervolt regulator's reg-on wire will be connected to the Lifepo4 batteries. When the ve.bus BMS wants to stop charging, the charge disconnect wire goes open circuit, the Mastervolt reg-on wire is disconnected from the lifepo4 batteries and the alternator regulator is turned off, stopping charging.


The problem is that the ve-bus BMS charge disconnect should be able to handle 10mA and the relay only requires 7mA as measured by a multimeter, but the relay doesn't engage as it should. So I'm looking for a lower current requirement relay.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @leftcoastman35

for disconnecting big loads, this relay is easier to use:

https://www.bluesea.com/products/7717/ML-RBS_Remote_Battery_Switch_with_Manual_Control_Auto-Release_-_24V

as you've noticed, you'll need an external relay to control the 'big relay'

for Charge Disconnect, you could use an optocoupler like this one:

https://www.wago.com/global/relay-and-optocoupler-modules/optocoupler-module/p/859-744

you could drive a bigger multi-contact relay with the optocoupler to connect all the chargers.

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leftcoastman35 avatar image leftcoastman35 commented ·

Thanks Daniel. For the load disconnect, I will try Gary's solution below of using the BP-220 to control loads connected to the 24v house panel. Since the house panel powers mostly low current devices (pumps, lights, fridges) and also powers the control circuits for the higher current devices (such as bow thruster/winches/passerelle), if I can completely cut power to the 24v panel, it will effectively load disconnect the whole boat without having to pass the full current of those high current devices.


For charge disconnect, so you're saying the Cyrix LI-CT would not work? It seems I can have the charge disconnect wire control this device. The "Li-on battery + " terminal would be connected to the lifepo4 battery bank and the "Battery +" terminal would be connected to the reg-on wire for the Mastervolt Alpha Pro II. When charge disconnect is high, the lifepo4 bank would be connected to the Mastervolt reg-on wire and the alternator would function normally. When charge disconnect is low, the lifepo4 bank would be disconnected from the Mastervolt reg-on wire and the alternator would stop charging.


The Mastervolt alpha pro ii reg-on wire is also the voltage sense wire for the the alternator regulator, so the voltage drop imposed by the octocoupler you specified would not work.

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