Marstek Venus 3 na 3 maanden: goedkope topdeal of frustratie?

Product reviewed

Marstek (Marstach) Venus 3 home battery, reviewed after ~3 months of use.

Key features mentioned

• Firmware upgrade that improved operation significantly.
• App connection/measurement behavior (goes “neatly to zero” after charging/usage).
• Capacity / usable energy: about 3.6 kWh usable (vs advertised 5 kWh).
• Discharge limit: cannot discharge fully to 0%.
• Battery temperature: no active fan; max observed temperature ≤ 35°C.
• Integration/API for “HOM(e)” (home automation / Home Assistant implied): an API is available, but data is unreliable/slow.

Pros (positives)

• Startup/connection issues resolved after a firmware update.
• No more connection problems; the battery is described as reliable, and measurements/behavior improved.
• Energy value: €1,200 is described as a very good deal for the usable kWh received.
• Thermals: battery temperature stayed around 35°C or below, so cooling design wasn’t a practical problem.
• Support appears able to resolve issues eventually (though not quickly).

Cons (downsides)

• App still buggy:
  • User is occasionally logged out.
  • After logging back in, the main screen may not show subsequent screens/data properly.
• Support response time is very slow:
  • Roughly 6–8 weeks to get a response after multiple questions.
  • Not ideal for serious problems.
• Capacity/usable energy discrepancy:
  • Usable output is about 3.6 kWh, while advertised/expected 5 kWh is not reached (attributed to charging/discharging losses).
• Cannot discharge to 0%:
  • Battery cannot be fully drained to 0% (noted as a “point of attention”).
• Home automation integration / API limitations:
  • Incorrect data returned via integration/API.
  • Cloud is slow.
  • Reviewer wishes for an official supported app.

User experience notes

• Initially, the battery had reliability issues (lost connection, not responding to measurements).
• After the firmware update, the experience became “perfectly” stable.
• Ongoing friction mainly comes from:
  • App logging out / display bugs
  • Slow support
  • Integration inaccuracies and slow cloud

Comparisons / benchmarks mentioned

• Efficiency/performance comparison:
  • Charged about 240 kWh, discharged about 200 kWh → return ≈ 82%.
  • Reviewer states this is comparable to other batteries.
• Capacity disappointment is indirectly compared to the communicated/expected 5 kWh figure.

Unique points checklist (all distinct issues/claims)

1. Firmware update fixed connection/measurement issues.
2. After the update, the battery runs reliably/stably with no more connection problems.
3. App still logs out occasionally and may not show subsequent screens/data correctly.
4. Support response took ~6–8 weeks after multiple follow-ups.
5. Usable capacity is about 3.6 kWh, not the expected 5 kWh.
6. Charging/discharging losses explain the capacity difference.
7. Battery cannot be discharged completely to 0%.
8. Observed energy return: ~82% (about 200 kWh discharged from ~240 kWh charged).
9. No fan cooling; temperature observed did not exceed 35°C.
10. “HOM” integration/API is not good: incorrect data and slow cloud.
11. Desire for an official supported Home Assistant/app from the manufacturer.
12. Overall price/value: about €1,200 is considered a strong deal.

Speakers / different views

• Single reviewer voice throughout (no separate speakers indicated).

Overall verdict / recommendation

Recommended with caveats. After a firmware update, the main reliability problem is fixed, and the price-to-kWh value is strong. However, expect app bugs, slow support, usable capacity below advertised expectations, no full 0% discharge, and weak/incorrect home automation integration (plus slow cloud).