Nasa BM1 vs BM1 Compact Battery Monltor

[pvb]

Digital display, bar graph is based on Ah in battery.

Brian

I think you'll find that it isn't. Users report that the percentage "state of charge" can vary rapidly as loads are switched on and off. This wouldn't happen if it was based on an actual Ah count. But instead of arguing with me, why not ask Nasa on Monday?

 

[Kylora]

As ( some ) others have said. The only indication of battery capacity on the BM1 Compact is vertical bar graph showing % capacity. In my experience, this is based on battery voltage in the same way that you would do manually and can be 'cheated' depending on whether the battery is being charged or discharged.

The set up includes an entry for battery capacity, but this is only used for the charge / discharge time remaining.

It displays instantaneous amps in or out but doesn't count them to calculate an AHr figure.

Ash

Edit need to type more quickly - pvb has said the same thing

 

[Richard10002]

But it gives amp hour indication, but yes it does not give a digital one I agree.

Have not seen a spec that gives Ah accuracy ?

Brian

NASA suggest that the graphical %age capacity is accurate, but not how accurate. They say it is not only based on voltage, but also amphours in or out, which is why you can suggest that it "shows" AmpHours, but it doesnt have the facility to show an actual cumulative number for AmpHours .

My personally perception after about 4 years using the NASA BM2, is that not only is it wildly innaccurate, but the fact that you have to actually enter capacity manually means that it cant be accurate, unless you are lucky enough to enter capacity accurately. I found that over a period, with some trial and error, I could have a good stab at entering the capacity correctly, but this relied on having a reading of cumulative Amp Hours, which is what is missing from the Compact.

The full size models have 3 screens - the missing screen shows cumulative AmpHours as a number.

My Smartguage is showing 87% and my NASA BM2 is showing 70%... They cant both be right, and my perception over the 2 weeks the Smartguage has been fitted, is that the Smartguage is closest to correct.