Over the weekend I fitted the nasa marine
BM-1 battery monitor
to the house bank (2x100amp). It works as I expected when I am using the battery
, drawing 0.4amp with just one light on and shooting up to about 5.0 when all lights, instruments and fridge are on. When I ran the motor
, the voltage increased up to around 14v and it was showing a charge of something like 10amps.
However when I turn on the shore power charger
, the voltage head
up towards 14v which is fine, but the amps "discharge" jump up around 10amp, rather than showing a "charge".
I'm not sure if I have ballsed something up with the install. Whilst all the cables
for the positive dissapear into the engine
bay to cause confusion as to how it is wired up (I assume the link between the two positive tterminals go via the power switched), the negative has just two cables
, one joining the two negative terminals and the other dissapears off to the engine
bay. I connected the shunt to the latter, which I think is correct.
I did make a mistake when I powered up as I had the shore charger
on when the instructions say to not charge to start with. I could imagine that this mistake may screw up the BM-1's estimate of capacity, but it does not make sense otherwise. The fact that it seemed to work correctly when the shore charger was off and the motor
on make me think that I connected it up correctly.
I do wonder if it is possible that the battery charger is wired up in a funny
way to cause this, but I really do not have a clue.
I did go into the "engineering" menu to set it to 200amp and when everything is off, no current
draw is shown.
I did notice that when the shore charger is on, the charge would go to 100 or even 105% bt when I turn the charger off it fairly quickly drops to close to 50% but then settles there.
Any clues, because I am lost
(and now 1200nm from the boat)???