I have a car inverter 1000W 12VDC to 230VAC, I wonder whether if I use a 9Ah 12V battery of Apache bike? Because I needed battery to power up a diy UPS from inverter that I wanted to build for my wireless ISP network. Here is the answer No, it’s not safe or practical.
Here’s why:
1. Power & Current Requirements
Inverter Rating: 1000W @ 230V AC
DC Input Requirement:
Power (W) = Voltage (V) × Current (A)
Current Draw = 1000W / 12V ≈ 83A (theoretical, but real-world inefficiencies increase this).
Peak Surge Current: Some inverters draw 2-3x more on startup (~160-250A).
Battery Specs (Apache 12V 9Ah):
Max Safe Discharge Current: Typically ~10-20A (varies by battery chemistry).
Capacity: Only 9Ah (very low for a 1000W load).
Problem:
The battery cannot supply 83A continuously—it will overheat, fail, or even catch fire.
Even if it worked, runtime would be minutes before deep discharge damage.
2. Runtime Calculation
Formula: Runtime (h) = Battery Ah / Load Current (A)
For 1000W @ 12V:
83A draw → Runtime = 9Ah / 83A ≈ 0.1 hours (6 minutes) (theoretical, but real-world inefficiencies reduce this further).
Practical Example:
If running a 300W laptop + light, current draw ≈ 25A → ~20 mins max (still pushing battery limits).
3. Risks of Using a Small Battery
✅ Overheating & Damage – The battery will overheat, reducing lifespan or leaking acid.
✅ Voltage Drop & Inverter Shutdown – High current causes voltage to sag, triggering low-voltage cutoff.
✅ Fire Hazard – Excessive current can melt wires or cause a thermal runaway (especially with lead-acid).
4. What Battery Do You Need?
For a 1000W inverter, you need:
Minimum: 12V 100Ah Deep Cycle Battery (supports ~80A continuous safely).
Better Option: 12V 200Ah LiFePO4 (lighter, longer lifespan, safer).
For Short Bursts (e.g., 300W): 12V 50Ah (but not for long).
5. Alternatives for Your Apache Bike Battery
If you only need small loads (e.g., phone charger, LED lights):
Use a 150W-300W inverter (max 25A draw).
Example:
150W Inverter → 12.5A → Runtime ≈ 40 mins (still not ideal but safer).
Final Verdict
❌ Do NOT use a 12V 9Ah bike battery with a 1000W inverter—it’s dangerous and impractical.
✅ Use a 100Ah+ battery for 1000W loads, or downgrade the inverter if using a small battery.
I wrote about battery capacity estimation for the diy UPS but in that calculation I used 100W.
