# Propeller Calc vs Ionic Red Batteries

The clearest difference is review sentiment: Propeller Calc at 100% against Ionic Red Batteries's 50%. Ionic Red Batteries's advantage is rating (4.2 vs 3.0) and update cadence (every 2 months vs every 21 months). On price, ads, in-app purchases and monetization model there is nothing between them.

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

Ionic Red Batteries holds the better App Store score, 4.2 against 3.0. That said, the two scores are not equally well evidenced: Ionic Red Batteries has 5 ratings behind it against 1, so its average is the more settled of the two. Written reviews complicate that: 100% of Propeller Calc's written reviews are positive against 50% of Ionic Red Batteries's, so the app with the better star average is not the one people write more warmly about.

Propeller Calc ships an update every 21 months, Ionic Red Batteries every 2 months. The most recent releases landed on September 9, 2026 and July 5, 2026 respectively.

## The numbers

| Metric | Propeller Calc | Ionic Red Batteries |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.0 (1 ratings)](https://appshunter.io/ios/app/propeller-calc/id478119478/reviews) | **[4.2 (5 ratings)](https://appshunter.io/ios/app/ionic-red-batteries/id1485708837/reviews)** |
| Number of ratings | 1 | **5** |
| Positive reviews | **100.0% of reviews** | 50.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 21 months | **Every 2 months** |
| Monetization | Free | Free |
| Size | 3 MB | 3 MB |
| Requires iOS | 17.0 | **12.0** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Frode Rørvik](https://appshunter.io/developer/478119481) | [深圳市南霸科技有限公司](https://appshunter.io/developer/1485708836) |

## What reviewers say

### Propeller Calc

[App page](https://appshunter.io/ios/app/propeller-calc/id478119478)

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:** macOS Compatibility

**In-app purchases:** none


### Ionic Red Batteries

[App page](https://appshunter.io/ios/app/ionic-red-batteries/id1485708837)

Monitor your car, boat, or UTV's battery status remotely via Bluetooth. This app allows for instant battery condition checks and even remote emergency starting, all from your device.

**Highlights:** Remote battery monitoring, Instant battery status, Emergency jumpstart activation, Bluetooth connectivity, Battery condition analysis, Discharge and charge time calculation

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Propeller Calc free?

Propeller Calc is free to download, with no in-app purchases.

### Is Ionic Red Batteries free?

Ionic Red Batteries is free to download, with no in-app purchases.

### Which has better reviews, Propeller Calc or Ionic Red Batteries?

Ionic Red Batteries is rated higher. Propeller Calc averages 3.0 out of 5 from 1 ratings, while Ionic Red Batteries averages 4.2 from 5 ratings.

### Do Propeller Calc or Ionic Red Batteries have ads?

Neither Propeller Calc nor Ionic Red Batteries shows ads.

### Which is updated more often, Propeller Calc or Ionic Red Batteries?

Propeller Calc ships an update every 21 months, and Ionic Red Batteries every 2 months. Most recently, Propeller Calc was updated on September 9, 2026 and Ionic Red Batteries on July 5, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*