asked
Battery Protect settings
What is the difference between Li-ion mode and Normal? Is it simply different voltage parameters or is there more to it? In Li-ion mode, it says Shut down at 10v and Restart at 13v. I feel that might be a little low for comfort and quite a wide range, can I put it on Normal mode and set my own limits e.g. 11v shutdown and 12v restart? Or is it best set to Li-ion mode? I am using LiFePO4 batteries.
Li-ion mode is really meant to be used in conjuction with an external BMS and the remote port of the battery protect. With Li-ion mode, when the remote is disconnect (BMS tells it to disconnect), it will immediately disconnect. The under voltage thresholds and alarm output of the battery protect are inactive in this mode.
If you have a drop in replacement lifepo4 like a battleborn then a battery protect needs to be programmed in another mode. With that said with these other modes, the load disconnect delay is 90 seconds so depending on the load, your BMS might kick in before the BP does.
As always, DO NOT connect a BP to an inverter, inverter/charger or in any manner in which current can flow in both directions. See the updated manual here:
https://www.victronenergy.com/upload/documents/Manual-Smart-Battery-Protect-12V-24V-65-A-100-A--220-A-EN-NL-FR-SV-DE-PT-ES-IT-TR.pdf
More specifically:
3. The SBP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden, and will damage the device. If you wish to use the SBP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT.
4. The short circuit protection of the SBP will be activated if you try to directly connect loads with capacitors on their input (eg inverters). For that use case, please use the SBP to control the remote on/off switch on the inverter, instead of disconnecting the higher power DC line.
Thanks @nebulight , I am using Valence U27-12XP batteries which don't have a suitable BMS that will provide the trigger to tell the SBP to disconnect, so I am relying on the Smart BMV-712 to provide that trigger when the voltage drops. I am not using an inverter, so that's not an issue. I have connected the positive of the battery to the "In" pole of the SBP and the "Out" pole to the loads. So I can set the SBP to one of the modes other than Li-ion? E.g. to disconnect at 11v and reconnect at 12v as I mentioned above? My ultimate intention is to use a pair of SBPs to effectively do the job of a BMS - one to disconnect at low voltages to prevent the batteries being drained too low, and another SBP that will regulate charge going into the batteries and disconnect at low or high temperatures or overcharge the batteries. This will be connected with the charging sources (Solar, Shore power charger and a DC 2 DC charger to be added at a later date) to the "In" pole, and the battery positive connected to the "Out" pole. I believe I need to connect a wire between the BMV relay output to the SBP relay input to achieve this.
You are never going to replace the functionality of the BMS with a BMV since that only accounts for over all voltage and not individual cell voltages. And since there is only one relay you can't control both charge and discharge BPs with just a BMV. For your discharge, you can wire up a fused 12v wire from your battery to the COM port of the BMV. Then on the NC output, take that and wire it to the H port on your BP and set it up in Li-Ion Mode and it will shut off your loads based on voltage, state of charge or temp (if you have a temp sensor on your 712).
However if you are going to go through this, you may as well just use a smart battery protect with a custom shutdown voltage and restart voltage on the load side (check it out in the demo library if you don't already have a smart battery protect). You could then use the above method for your charge side to control your chargers with a second BP. This way you can add a temp sensor to your BMV to prevent chargers from charging during below freezing temps. Just make sure the DC-DC charger you end up with doesn't charge your starting battery when full as that will damage the battery protect as current cant' flow in both directions.
Again, this won't replace a BMS and won't prevent you from damaging your battery if you have a cell imbalance. I know the Valence batteries are cheap when buying used, but for that matter you could probably buy raw cells and make your own battery with a proper BMS.
Thanks @nebulight The Valence batteries have a simple internal BMS which takes care of balancing cells, it just doesn't have the capability to shut down in the event of over/under voltage or temperature. It is more of a Battery Monitoring System rather than a Battery Management System. I was under the impression that the BMV would tell the SBP to disconnect the batteries from the load when it saw the voltage drop to a set level via the Bluetooth network?
That would be a nice feature, but bluetooth on the SBP only does programming and monitoring from Victron Connect. It doesn't talk to other Victron gear. And honestly for this use case, I wouldn't want to rely on bluetooth. I'd prefer a hard wired connection for something to protect the lifepo4 battery.
My above suggestion should work for your setup. Stand alone BP with custom voltage programmed in for your discharge side and a BP that is controlled by your BMV relay for the charge side. Trigger the relay to disconnect at temp OR voltage.
