fmeili1
Solar Addict
In general, I have a few issues or fear future problems or have some disadvantages when using the AIOs grid connection that I would like to eliminate with the double-conversion. I want to list most of them as a summary:
Current issues while using AIO's grid support:
Possible problems in the future while using AIO's grid support:
For sure there are also disadvantages with double-conversion which I'm aware of and I'll live with them:
Current issues while using AIO's grid support:
- At the moment, when the AIOs will be connected to the grid (not the moment when the AIO goes to bypass), the fault F60 (Power feedback protection) occur sometimes. If this happens, I have to reset the whole system with all 6 AIOs. It happens more likely if the load is low and PV production is ongoing. I've implemented complex smart home rules to minimize the risk, but it's anyway not nice.
- The switching time, if grid is attached and the AIOs going to/from bypass (I only use SBU mode), is short - but it's long enough that my small UPS' in the house are clicking. Sometimes my pool pump will stop/restart when the AIOs are switching from/to bypass. I think for long term usage, my appliances won't like this.
- update: I've forgotten to mention the following scenario, which produces a complete crash (all AIOs going to fault mode):
- All units are switched on and system is running in bypass
- Switch off some units to save idle consumption over night (system still in bypass)
- As soon as one of the AIO which were in "off" state is switched back to "on" (while the working ones are still in bypass)... boom! All AIOs in fault mode and ALL GFCI's breakers and many GFCI receptacles tripped in the house... luckily no damage on appliances nor on the AIOs... but really bad behavior.
- The grid battery charging can only be used if the AIOs are in bypass mode. When running in inverter mode, no grid charging is possible (inverter and grid charger using the same H-bridge - it's either/or). It's only a small disadvantage, but it's not longer the case when using double-conversion.
- The grid charging efficiency of the AIOs is not great.
- The max grid charging current could only be controlled in pre-defined steps which does not always fit the needs.
Possible problems in the future while using AIO's grid support:
- I know at least one person who also uses the EG4-6500EX (also 6 in parallel) where his POCO showed him that his system feeds back into the grid (see this message). He also always using SBU mode - usually in SBU a backfeed should never happen - but it does (even only for small amounts and maybe only in the situation when bypass is switched on or off - but it's not really clear until now). I don't want to risk problems with my POCO about back feeding in the future.
- I'm pretty sure the bypass relays will wear out quickly when they are often switching under high load conditions (which I have often).
For sure there are also disadvantages with double-conversion which I'm aware of and I'll live with them:
- The house could not draw more than the max. online-conversion power over longer times (depending on battery SOC). In other words, if the batteries are completely empty, the max house load could not be over 16kW because the chargers are "only able to deliver 16kW compared to the possible 39kW when the AIO's grid support would be used (6x 6500W). It's very unlikely that this happens and I will live with this (and I'm not willing to build a 39kW DIY-chargeverter
)
- Additional costs.
- update: It's not possible to enable/disable battery charging or enable/disable driving the house load separately. Because the rectifiers just feeding the busbars, it does automatically both. Maybe it's possible to play a bit with the rectifiers voltage to do "more or less charging", but it's not really controllable.
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