@brassmonkey001, it's not quite as simple as that. The BatteryProtect is a one-way device only, which means that if you want to use it as a charge disconnect, you need to connect it in "reverse" - that is, with the charge sources connected to the "in" post and the battery connected to the "out" post; you may then configure it to disconnect in the event of high voltage.
To use it as a low-voltage load disconnect, you need to attach the battery to the "in" post and the loads to the "out" post. You cannot have a single BP serving both purposes. Current applied to the "out" post flowing to the "in" post will immediately and irreparably damage the BP, and can pose a very significant fire hazard.
It's also worth noting that to configure the BMV relay to trigger based on temperature, you will of course need either the BMV-702/712 temperature sensor connected to the shunt PCB or a Smart BatterySense on a VE.Smart Network with the BMV.
Please see the updated BatteryProtect user manual here: https://www.victronenergy.com/upload/documents/Manual-Battery-Protect-12V-24V-65-A-100-A--220-A-EN-NL-FR-DE-SE-SV-PT-TR-IT.pdf
@brassmonkey001, correct on the charge side; setting it up properly will be a lot easier if you have the Smart BatteryProtect, so I strongly advise you pay a little extra for that so you can just configure everything on your phone.
On the discharge side, yes, you can have another BP (preferably the Smart BP) connected to the POS terminal with "in" connected to battery and "out" connected to your loads and you can configure it to shut down your loads at your desired voltage. Again, I strongly recommend the Smart version because you can dial in the shutoff/restart voltages to 1/100th of a volt, rather than being limited to the factory presets.
One important thing: the two BPs have to be on separate lines... ie, your charging cutoff BP connects to your battery POS via one cable, the disharge cutoff BP connects to your battery POS via a separate cable; you can't have the two BPs on the same line because then you're back to running reverse current through them.
As for external control, you can of course configure it to turn on/off via an external relay, but it's a lot simpler to just get the Smart versions and then configure them to do whatever you want. Obviously the temperature trigger will need to be an external trigger source, but all your voltage triggers can be set via the device interface itself.
Right, so the "charge" BP will be externally triggered by your BMV; you'll set your BMV relay out to trigger based on temp (you set this in the app, connected to the BMV over bluetooth), and run the trigger wire down to the "charge" BP and into the remote switch pins. I think Victron even shows something very similar on the diagrams included with the new updated manual.
The "charge" BP won't be on a VE.Smart network at all because it's getting the trigger command via hardwire from the BMV. (this is the "external trigger source" I was referring to)
The "load" BP won't be networked either, you just set the voltage cutoff/restart points in the app and you're good to go.
You'll set up each device separately in the app, so they actually won't be "talking" to each other at all... one is doing one thing and the other is doing something else entirely, so they don't need to share information.
Well, that's always been a concern in the back of my mind, but the reality is that it's no different than if the battery BMS itself cut off charging due to temp/voltage, and that's a supported function, so... I tend to not worry about it. I've actually tried forcing an MPPT to fail by repeatedly disconnecting the battery while the MPPT was going full-bore and I've never been successful in causing a failure, so my takeaway is that while the instructions to always disconnect PV first serve a viable purpose and do protect against possible controller damage, I think the likelihood of it actually causing damage to the controller to disconnect the battery is effectively zero.
I've done that, but only with my DC-DC charger and MPPT. I have a basic BMS with no temp control so I run the 'allow to charge signal' through the 712 relay and have that configured for temp control. So when the 712 temp sensor is too cold, it shuts off charge by disconnecting the BP100 I have for the chargers (50 amp DC-DC and 300W of solar through a 100/50). For the AC charger, I have a multiplus, so I use the two wire assistant to turn off the charger. I wired in an optoisolator to the same allow to charge signal after the 712, so it can also shut off when it's too cold.
Always have a BMS, don't use the BMV low or high voltage alarms for lifepo4 as that doesn't account for individual cell voltages. I'm only use the BMV to make up for the shortcomings in temp control on my BMS.
Additional resources still need to be added for this topic
MPPT 150/60 up to 250/70 Manual
Victron BatteryProtect product page
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