Phantastic, that a reverse emergency charging has been implemented and is available as a firmware update! Thank you, Victron.
As my use case is on a sailboat and in combination with a Cerbo GX (connected via VE.Direct), I wish that this function could also be accessed from the Cerbo (i.e. the Venus OS). I could even imagine to wire such an emergency reverse charge function with a button acting on a Cerbo input and a LED connected to a Cerbo output showing that it is active. It would be great if Victron could make such a setup possible - I do not like to rely on a smartphone connection.
And a second thought (which I guess is valid for boats and RVs): the classical configuration is that PV is charging the house battery all the time. When a boat/RV is not in use and not plugged to shore power, the house battery is full all the time - but the starter battery is not charged at all. If this reverse function could also be extended to charge the starter battery automatically after the house battery has reached a certain SOC, this would be awesome! In my case, the house battery is LiFePO4 (BMS controlled) and the starter battery is lead - so it should be possible to detect for example SOC of the house battery > 90% (or has reached the charging voltage end the BMS is asking for) to start reverse-charging the starter battery whenever PV power is available. Keeping the starter battery full would extend its lifetime.
Would other users find such a function useful as well?
As already mentioned in the other topics about the emergency charge feature:
It’s just the beginning and the feature will get more functionality over the next weeks/months.
This is the first of several reverse charging features planned for the Orion XS range.
I would expand the feature considerably. For installations in vehicles and holiday homes, you have to use lead-acid batteries if there is a risk of frost. To still be able to use LiFePO4 batteries when temperatures are suitable, a reverse function would be useful. Both ends of the charger would need to offer the same settings as solar charge controllers. This would mean the existing installation would remain virtually unchanged. You would simply connect the charger to the battery. To ensure the existing lead-acid battery continues to charge correctly, the Orion XS must only draw enough current from the system to avoid dropping below the absorption and float charging voltages. The current must therefore be continuously adjustable. The Orion XS also needs to know which charging stage is currently active. This could be communicated via VE.Smart Networking. If the same settings as those in the charge controllers are configured on the Orion, it can calculate the voltage at which charging will not affect the lead-acid battery. For example, this might be at voltages around 20 mV lower. From the start of the absorption phase, the Orion would then draw the current that the lead-acid battery cannot use and transfer its energy to the LiFePO4 battery. This amount of energy increases over time and is substantial. Otherwise, it would go to waste (the main disadvantage of lead-acid batteries). If it is the XS1400, batteries with different voltages can even be used. This would be very useful if you wanted to support a 24 V system with a 12 V LiFePO4 battery you brought along. When there are only short periods of sunshine, the lead-acid battery does not fully charge. The decreasing charging current extends the charging time beyond sunset. During this time, the LiFePO4 battery can continue charging the lead-acid battery for an adjustable period, until it switches to a storage voltage. If the lead-acid battery is under load, the Orion will try to maintain the calculated voltage. So the LiFePO4 battery will be discharged first. The Orion has to measure the current from the LiFePO4 battery anyway, so it could also serve as a battery monitor for it. A temperature sensor on the LiFePO4 battery would prevent charging at too low a temperature.