We have a battery setup on our boat with a large 600Ah 48V lithium battery bank, and we're testing out the Wakespeed WS3000 bidirectional 12V<-->48V dc-dc converter as the bridge between the high voltage house bank and the 12V system for the alternators/normal house loads. We also have 2040 watts of solar panels (3S4P of the 170 watt sunpower panels), running through a Victron 150/70 MPPT charge converter, with output connected to the 48V house bank.
When sitting on anchor/motor not running/WS3000 disabled, and the battery low enough (52.6V or so), everything works normally. MPPT hunts around for a while, and eventually settles on a good current load, and we get great returns (1600+ watts from a 2040 watt bank, perfectly horizontal on the roof of a boat on a wispy cloudy day, I'll take it!). However, when the batteries are close to full (>90% soc), when the engines are running, the WS3000 starts taking excess current from the 12V side and sends it up to the 48V bank, and whenever this is active, the voltage gets up to 53.0V or above, and the MPPT converter very quickly freaks out and, while still in Bulk mode, ends up at 0.1-0.2A of charging, with the solar side voltage at basically the open circuit voltage (~96V in this case). If I power cycle the MPPT, it settles into that same state again. If the resting voltage is 53.0V or so, no matter what the WS3000 is doing (can even be turned off), the MPPT ends up in the same state. So it basically feels like it can’t charge above 53V or so
During this charge process, the absorb is set to 56V (for both the WS3000 and the MPPT), and the float is set to 55.2V. I've tried playing with everything I can think of in the settings for the MPPT, including going both lower and higher for absorb and float settings to try to trick it. Any ideas what to change next? Is this a broken MPPT unit that needs replacing?
