Update: This popular front page deal is available again for slightly less with a new promo code.
BOOKOO via Amazon has for
Prime Members:
20,000mAh BooKoo A9 2000A Car Battery Jumper w/ QC 3.0 + 18W Power Delivery for $36.79 - $14.72 w/ promo code
TYLQ6GNL at checkout = $22.07 -->
Now $21.89.
Shipping is free.
Thanks to Deal Editor
iconian for sharing this deal.
Product Details:
- 74Wh portable lithium car battery jump starter can safely jump start a low volt,drain or dead car battery in seconds with this 2000A car starter, rated for gasoline engines up to 8.0L and diesel engines up to 6.5L.
- 3 LED lights modes: Flash Light, Strobe Light, and SOS Light
- 20000 mAh large capacity battery backup can start dead battery over 30 times
- IP66 Water Resistant
- USB-C Input
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Top Comments
Based on extensive testing, most of these devices only deliver about one-third of their advertised capacity. In reality, you're likely getting around 12,000 to 16,000mAh of usable energy.
High amp ratings like "1500A peak" are common, but they don't tell the full story unless:
- The boost circuit is well-designed,
- The battery cells can sustain high discharge current,
- The wiring and connectors are thick and efficient.
My 3.0L German diesel engine requires approximately 800 amps for 3 seconds during startup.
Power Calculation: 12V × 800A × (3 sec / 3600 sec) ≈ 8 Wh
So, a single crank uses about 8 watt-hours. If your jump starter is rated at 30Wh, you'll get maybe 2–3 cranks total, especially after accounting for energy lost during voltage conversion.
- Cheaper units lose 20–25% energy in the process.
- High-quality brands like NOCO typically lose 15–20%.
How to Accurately Test a Jump Starter:
1. Charge the jump starter to 100%. Use a USB power meter to ensure it's no longer drawing current.
2. Discharge it completely and record the watt-hours (Discharge Wh).
3. Calculate actual capacity in mAh: Real Capacity (mAh) = Discharge Wh ÷ 3.7V
4. Charge the device back to 100% and record the input watt-hours (Input Wh).
5. Calculate energy loss: Loss Wh = (Input Wh - Discharge Wh)
6. Calculate efficiency: Efficiency % = 100 - (Loss Wh ÷ Input Wh × 100)
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Same OP. Are they the same?
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Same OP. Are they the same?
Scatach 011 3000A Car Battery Jump Starter,12V Jump Starter Battery Pack (up to 9.0L Gasoline and 7.0L Diesel Engine), Portable Jump Box with 3 Modes Flashlight and Jumper Cable
https://www.amazon.com/dp/B0CGCRH...title
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