Nach Fírmwupdate auf v1.29. speisst der MPPTRS450-100-TR keine überschüßigen PV-Ertrag mehr ins Netz

Ever since the Victron MPPT RS 450/100 got nudged onto a newer firmware, my Pylontech stack has basically decided it's on a go-slow the moment it hits 98% — excess solar just vanishes into the ether rather than being exported or even dumped into the EV charger like it used to.

Three years of rock-solid behaviour, then one firmware update and suddenly the thing's throttling PV output as if the batteries are made of tissue paper. 🤦

From what I can piece together, it seems like the MPPT is now being far too cautious about the BMS charge ceiling signals from the Pylontechs — essentially treating "nearly full" as "absolutely full, shut everything down." Whether that's intentional Victron nannying or just a bug, I genuinely can't tell.

A few things worth checking if you're in the same boat:

• DVCC settings in VenusOS — particularly SVS and SCS — worth toggling to see if it changes behaviour
• Check your Pylontech firmware too, apparently some older US2000 units started sending slightly different charge limit values
• The Victron Community forum has a thread building up on this but no official fix yet

Curious whether anyone here running a similar setup — especially if you're also trying to push surplus into an EV charger rather than waste it — has found a workaround that doesn't involve rolling back firmware and living in fear of auto-updates forever.

Anyone else's cabin or static getting robbed of free electrons by an overzealous MPPT? 🔆

WillowWalker | 847 posts

@KentCruiser Sounds like the new firmware tightened up the absorption/float transition behaviour. Worth checking your DVCC settings in VenusOS — specifically whether "SVS" (Shared Voltage Sense) is still properly enabled after the update. Sometimes updates can quietly reset those parameters.

Also, what firmware is your Pylontech BMS reporting? If the RS450 and BMS aren't handshaking correctly on the CAN bus, the charger will throttle aggressively well before actual full charge, which matches what you're describing.

Try pulling the VRM logs and looking at the "Charge Current Limit" channel — if it's being dragged down to near zero around 98%, the BMS is telling the MPPT to back off rather than it being a firmware bug as such. Pylontech support have been decent in my experience if you need to dig deeper.

DailySolar | 1,203 posts

@KentCruiser Classic symptom of the DVCC + BMS-controlled charging interaction post-v1.29. Your Pylontech is sending a CVL (Charge Voltage Limit) signal via CAN-bus that the updated firmware now actually respects more strictly than before — so when cells approach full, the MPPT backs off hard rather than hunting for excess headroom.

Check your Venus OS DVCC settings: specifically whether "Limit charge current" is being dynamically commanded by the BMS. You'll likely want to verify your Max charge voltage in the Pylontech BMS parameters matches what's appearing in VRM.

The "excess vanishing" bit is key — are you seeing the MPPT throttle output or is it actually clipping? Two very different problems. If your grid feed-in stops simultaneously, that points toward a SVS/SCS misconfiguration rather than purely absorption behaviour.

What Venus OS version are you running alongside it?

ExTrucker73 | 312 posts

@KentCruiser worth checking your ESS assistant settings in VE.Configure — specifically the "feed-in excess solar charger power" tick box. After v1.29 that sometimes resets itself, especially if DVCC is active.

Also, what's your Min SOC set to in the ESS menu? If it's crept up toward 95-98% somehow, the system won't see enough headroom to justify grid feed-in.

Had something vaguely similar on my motorhome rig (different scale entirely, just a Fogstar 200Ah), where a firmware nudge quietly changed how the MPPT handed off control to the CCGX. Not identical but same flavour of problem.

Check the VRM portal logs for that period — the "solar yield" vs "grid feed-in" graphs will show exactly where the power's going missing. Usually tells the story within seconds.

Wez1961 | 2,104 posts

@KentCruiser had almost identical grief with my RS450/100 after v1.29 dropped. Worth checking your DVCC shared voltage sense is actually enabled in VEConfig — firmware update wiped mine back to defaults silently.

Also look at your Pylontech's reported max_charge_current via the BMS. At 98% SOC it'll be throttling hard. The RS450 now respects that more aggressively than before.

One thing @ExTrucker73 and @DailySolar haven't mentioned — check your grid feed-in limit under ESS → "Feed excess DC-coupled PV into grid." If that toggle got reset, surplus just... disappears exactly as you're describing. Caught me out for nearly a week before I spotted it.

LochChild | 847 posts

@KentCruiser one thing nobody's mentioned yet — check your minimum SOC setting in the ESS menu on the GX device. After v1.29 there was a subtle change in how the RS 450 interprets the "keep batteries charged" logic when BMS CV phase kicks in.

Had something similar on my static caravan setup. Pylontechs were sitting fat and happy but the MPPT was throttling back hard. Turned out my Min SOC was set oddly and the system was essentially fighting itself.

Also worth a look at the charge voltage setpoint coming through from the BMS — if the Pylontech is pushing a lower CV than the MPPT expects, it'll just back off rather than feed excess anywhere useful.

VRM portal should show the MPPT state clearly if you've got a Cerbo or similar hooked up.