Numpty question re recently purchased deep cycle batteries.

[Mistroma]

As a marine electrician you really ought to know that Ah doesn't tell you energy capacity without knowing the voltage. Thank goodness there's an engineer on hand to help you out


Without knowing total capacity of the battery, the monitor can display a running tally of net current flow.

I'm not familiar with the NASA BM1, but I assure you, it is just measuring net current across the shunt and applying Peukert's equation to it with a temperature adjustment. It doesn't need to know the overall capacity in order to do any of this. The only things it can't do without knowing the total capacity are display the % SOC and the time to empty. If it won't show the tally of net current flow without knowing the nominal capacity, that's a limitation of the display itself rather than the information being unavailable to the unit.

The BM1 does display %SOC and that's exactly why you tell it the nominal capacity initially. It can then give some idea about SOC even when battery is in use and voltage can vary a lot. All guesswork in reality but I imagine it makes some attempt to correct capacity to some extent over time. Probably not very well of course. I imagine Paul will give you chapter & verse as he'll have installed a few.

I don't use a BM1 myself as my boat has a Smartgauge + Bluetooth device logging Ah/Wh in & out + solar & wind regs. with similar capability. BM1 is a bit redundant for me and I have never used one.

 

[geem]

Deleted ?

 

[roaringgirl]

[Inappropriate quoted content removed]

You obviously know the BM1 well and are able to offer more specific advice than me on it.

You don't seem to be disagreeing with me any more about the relationship between Ah, volts and energy capacity, is that because you're now in agreement?

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[Beneteau381]

You obviously know the BM1 well and are able to offer more specific advice than me on it.

You don't seem to be disagreeing with me any more about the relationship between Ah, volts and energy capacity, is that because you're now in agreement?

You've called me an idiot above, this breaks the forum rules. Remove it please.

Hang on, you agreed with Paul in your first post "Presumably, you used 2 of them in series to make 12V, so you have 232Ah @12V (nominal)."
So why the argumentative pseudo engineering stance?

 

[Poey50]

Amp hours are dependent on voltage.

Watt hours are dependent on voltage. That's a good measure of capacity if the nominal voltage of a system isn't specified. If the voltage is already known then it is conventional to use amp hours for capacity.