Battery Monitoring budget alternative


I have been looking for a good way to monitor the single battery in my 100 series LC and after quick research on google, I came to the conclusion that getting a quality one that accurately shows SoC and amp-hours consumed is going to be more expensive than expected. Then I came across this small startup company making a Bluetooth monitor, but I don't have enough knowledge in this domain to know where this product is lacking - other than not having a display. A display isn't too important to me given that I normally check on the battery when in camp, doing this in bed away from the vehicle on my phone seems very convenient.

Here is a summary of the features, lifted from the website:
  • Remotely monitor two DC voltages, current, power, energy (Wh), battery charge, (Ah) and temperature
  • Measure voltage up to 60V and current up to 60A using the internal current shunt
  • Sense up to 160mV of voltage drop across an external current shunt, allowing 300-600A currents to be measured
  • Monitor battery state of charge (in %)
  • Control a power relay or SSR (Solid State Relay)
  • Low / high voltage disconnect & over-current disconnect
  • Battery isolator for multiple battery systems
  • Remote ON/OFF switch and timer functions
  • Password lock function
  • Low (8mA) self consumption
  • Easily configurable

I have heard of the Victron BMV series being the best one available and allows programming of Peukert constants etc to suit the battery type. This Thornwave product appears to be high-quality and made by someone who knows what they're doing (I may be wrong), plus it is being actively developed and has had regular firmware updates to add functionality. Can anyone who's knowledgeable about this subject please take a look and share your thoughts?

PS - I have no affiliation with this or any other company.
When I first read that I read it as it would measure two voltages and two currents. It measures two voltages and one current. Internal shunt to 60 amps and will handle external shunts.
Not too bad except most will want or need at least two. The app is a little generic. Someone could write a new app and dress it up a bit with some graphic scales and do some calcs to furnish remaining run time at present amp draw.

Recommended books for Overlanding


Even $300 BMs only count AH and guess SoC for one bank.

You should never have more than one House bank.

Starter should not need monitoring.


60A limit (likely 45-50A continuous, depends on temperature)

Is too low for bigger systems.

Remember, **total** amps from all concurrent loads **or charging** needs to be well under that spec.


Thanks @john61ct. There is a provision to use up to a 600A external shunt. The large metal screw terminals are provided for that purpose.

Here are the FCC teardown photos:

  • Like
Reactions: WVI


Allows an external shunt, great, 500A and even 1000 are available.

You will lose resolution on measuring low current rates, but it lets you calibrate if you have access to a known good ammeter, great.

It doesn't let you tune Peukert, but defaults look OK.

No charge efficiency setting?

Won't be as accurate as a Victron but I'm sure helpful, long as you frequently reset at 100% SoC.

SmartGauge is best for lead SoC, very easy, but also expensive.


This seems like a decent and cheaper alternative to the Victron BMV units and I looked at it before going with Victron. If I had more time and less budget I would consider it. However I went with Victron for two reasons:
1. The Victron BMV units work with the Victron ecosystem - so if you are considering a solar system or inverter, you get all the information in one place.
2. Victron is not a start up - you take a significant risk going with a startup. Maybe the developer gets bored and moves on or like most startups the company folds in the next year or so, leaving no one to support/develop to app and keep it working with OS updates.


Same outfit tried to Kickstarter a little portable MPPT SC a while ago.

Never got into actual production AFAIK, but their PR/marketing/social media efforts were very competent.

The generic straight-from-China competitors do not have any Peukert accommodation, and only a little cheaper, so I'd certainly give it a try.

At that price no great loss if it dies after a year or two.


I have a friend using this system (w/ external shunt) and he is happy with it. Developer seems responsive to input about app ideas also.