Comparison

Propeller Calc vs Epoch Li

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Propeller Calc

This utility calculates propeller performance metrics like pitch, gear ratio, RPM, slip, and speed. Input any four values, and the app computes the fifth, helping users understand the relationship between propeller design and boat performance.

Highlights
  • Calculate pitch, gear ratio, RPM, slip, and speed
  • Enter any four variables to find the fifth
  • Understand propeller slip and its impact
  • Supports iPhone and iPad
  • Free to use
Features
Read full description

This calculator can determine pitch, gear ratio, RPM, propeller slip and speed parameters. Enter any four variables, and it will calculate the fifth. Use the toggle switch to choose which field to calculate. Pitch is the theoretical forward movement for one complete turn of the propeller. Every inch of the boat in contact with the water induces drag. Therefore, the distance travelled differs since the propeller is "slipping" behind the theoretical distance it should travel with each rotation. The difference between theory and reality is called slip. Depending on your application, slip typically ranges between 5% and 20%. A lower number is only sometimes what you are after. Slip of a prop changes with operating conditions and is not a direct measure of efficiency. Please consult professionals for guidance. Happy powerboating

About

Epoch Li

Monitor your lithium-ion battery system in real-time via Bluetooth. View voltage, current, power, and internal resistance. Receive alerts for temperature, short circuits, and voltage deviations to extend battery life and enhance stability.

Highlights
  • Real-time voltage, current, power, and internal resistance display
  • Individual battery voltage and alarm status monitoring
  • Cell comparison and balancing display
  • Temperature and critical parameter warnings
  • Record of all warnings and protection events
Features
Read full description

Make sure you have the latest app version. Turn on your Bluetooth. Tap the icon to open the App. It will search for all Epoch batteries within the range of your Bluetooth device and provide a list. If all the batteries are not listed, move closer to the battery location and refresh the screen. Choose the battery you want to look at. The Epoch intelligent battery management system and the active equalizer are connected via Bluetooth to monitor the battery status, collect, store and process information during battery operation in real time, exchange information with external devices, and solve the safety, usability and usage of the lithium battery system The key issue of life is to extend the service life of the battery to a certain extent, and to enhance the stability of the battery pack to a certain extent. 1. Display real-time voltage, current, power, internal resistance and other parameter values, and display them in the form of instrument panels and numbers; 2. Display the real-time voltage and alarm status of all single batteries. If the reported parameters trigger the alarm value or protection value, an alarm will be prompted; 3. Each data comparison of the battery cell, the voltage difference. Maximum voltage cell Minimum voltage cell. And the display of cell balance 4. Cell temperature warning. Real-time alarm for over temperature, short circuit, over voltage, under voltage 5. Record the warnings that occur at each moment. 6. Record all battery protection times. Best Regards !

Screenshots

Propeller Calc2 screens
Epoch Li4 screens

Verdict

The call

The clearest difference is review sentiment: Propeller Calc at 100% against Epoch Li's 29%. Propeller Calc also leads on rating (3.0 vs 2.6). Epoch Li's advantage is update cadence (every 3 weeks vs every 21 months) and ratings volume (70 vs 1). On price, ads, in-app purchases and monetization model there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Propeller Calc holds the better App Store score, 3.0 against 2.6. That said, the two scores are not equally well evidenced: Epoch Li has 70 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 100% of Propeller Calc's written reviews are positive against 29% of Epoch Li's.

UpkeepUpdate frequency

Propeller Calc ships an update every 21 months, Epoch Li every 3 weeks. The most recent releases landed on November 1, 2026 and November 3, 2026 respectively.

Scorecard5 real differences · 5 level
Propeller Calc versus Epoch Li: the parameters behind the verdict, then further details
ParameterPropeller CalcEpoch Li
PriceFreeFree
Rating3.0 (1 ratings) — better2.6 (70 ratings)
Positive reviews100.0% of reviews — better29.2% of reviews
Number of ratings170 — better
Update frequencyEvery 21 monthsEvery 3 weeks — better
AdsNoNo
In-app purchasesNoNo
MonetizationFreeFree
DevicesiPhone, iPadiPhone, iPod
Requires iOS17.013.0 — better
Further details — not scored
Size3 MB35 MB
Age rating4+17+
DeveloperFrode RørvikEDG Sales International LLC

Customer experience

Propeller Calc

All ratings1 ratings
Positive0.0%
Neutral100.0%
Negative0.0%
Written reviews1 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Epoch Li

All ratings70 ratings
Positive35.7%
Neutral5.7%
Negative58.6%
Written reviews48 reviews
Positive29.2%
Neutral10.4%
Negative60.4%

Bugs and requests

Propeller Calc

Not enough reviews yet to summarise bugs or requests.

Epoch Li

Reported bugs

14 issues
  • Bluetooth does not auto-connect
  • Bluetooth signal frequently drops
  • App crashes frequently
  • App disconnects when minimized or switching apps
  • App does not remember previously connected devices
Show 9 more
  • App shows incorrect battery charge levels
  • App history tab is useless
  • App is not documented, data is unclear
  • App shows 0% or no data after recent updates
  • App does not always reflect true battery charge
  • App cannot see information from multiple batteries in series
  • App has backward animations and sloppy UI
  • App requires password for advanced settings without providing it
  • App disconnects and will not re-connect until app is killed and reopened

Requested features

10 requests
  • Filter Bluetooth devices by MAC address prefix
  • Implement BLE non-exclusive connection
  • Bring back old app features (time to charge/discharge)
  • Document app data and features
  • Provide password for advanced settings
Show 5 more
  • Allow saving of battery connections/names
  • Release old app as a separate option
  • Improve Bluetooth connection stability and range
  • Fix incorrect battery charge readings
  • Display data for multiple batteries in series correctly

In-app purchases

None

Propeller Calc

No in-app purchases

None

Epoch Li

No in-app purchases

Questions

Is Propeller Calc free?
Propeller Calc is free to download, with no in-app purchases.
Is Epoch Li free?
Epoch Li is free to download, with no in-app purchases.
Which has better reviews, Propeller Calc or Epoch Li?
Propeller Calc is rated higher. Propeller Calc averages 3.0 out of 5 from 1 ratings, while Epoch Li averages 2.6 from 70 ratings.
Do Propeller Calc or Epoch Li have ads?
Neither Propeller Calc nor Epoch Li shows ads.
Which is updated more often, Propeller Calc or Epoch Li?
Propeller Calc ships an update every 21 months, and Epoch Li every 3 weeks. Most recently, Propeller Calc was updated on November 1, 2026 and Epoch Li on November 3, 2026.

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