30 minutes ago, plonkster said:

Just don't start any new fires, 'mkay?

I'll try not to.... If I do I will try and fight it 

On 31/5/2017 at 4:58 PM, ebrsa said:

Hi @PeterGutti, There is no need for transferring money to my bank account but thank you for the kind offer. We are after all just trying to help one another and not duplicate the great amount of effort needed to optimise out systems.

The function of BMV parameter 2 is to determine when the batteries are charged and then switch the charger to the battery float voltage. Victron explained it as follows in an e-mail reply to a question from me. When you have a steady current such as a generator or the grid, one would set parameter 2 to the float voltage minus 0.2V to 0.3V. Three conditions have to be met for switching to float, the setting of parameter 2 and the tail current (parameter 3). Both these have to be valid for the charged detection time (parameter 4). When charging from solar it is possible that cloud cover for instance could result in a charge current equal to the tail current and a voltage equal to the setting of parameter 2, all for the detection time before the batteries have reached the fully charged voltage. Victron recommended that, when using solar panels, parameter 2 be set to the charged voltage minus 0.2V to 0.3V. This will ensure that the charged voltage is reached before the BMW switches the charger to float voltage. @Don refined his setting further by setting the tail current to a small value 0.5 x AH and he also increased the charged detection time to 50 minutes as far as I remember.

If I had your batteries, which seems to be really outstanding, I would be inclined to use the settings as described in the manual with the Victron recommendations for solar applied. After all according to the manual one could charge at 54V which is also the float voltage. The higher voltage of 56.4V will just optimise charging from solar panels.

As far as the USB to Serial device detected by lsusb, I wonder if it might perhaps be the Victron USB converter that is detected.

Hi @ebrsa. One last uncertainty:  During the day the batteries get charged up to the specified voltage (54V).  And than, after sunset, the voltage drops to 51V withing minutes.  

Is that a normal behaviour?  Or the barreries are weak?

Greeting, Peter 

 

1 hour ago, PeterGutti said:

Hi @ebrsa. One last uncertainty:  During the day the batteries get charged up to the specified voltage (54V).  And than, after sunset, the voltage drops to 51V withing minutes.  

Is that a normal behaviour?  Or the barreries are weak?

Greeting, Peter 

No that is absolutely normal. The difference is between a battery bank at float and no longer being charged.

Hi @PeterGutti, I don't expect that your very high quality batteries will fail very soon. As @Chris Hobson said, it is normal behaviour for the batteries. While your panels are charging, there is of course no load on the batteries to pull the voltage down. When the sun sets, load is placed on the batteries, resulting in the rapid initial voltage drop. If you removed the load for a while, the voltage will rise, probably to close to 54V. So I guess you will have some years to come before you need to worry about battery replacement. Enjoy sunny Spain while we shiver in the middle of winter with cold but little rain. Now that is something to worry about as our dam has only about 10% usuable water and summer is not too far away.

A 12V battery, when left at rest, should level out around 12.8V, or around 51V for a 48V bank. It is absolutely completely normal, in fact, it would be cause for concern if it didn't do that.

I've managed to get my batteries to level out at 26V (ie 13V per battery, 52V for a 48V bank), but that was after it spent an entire day on absorb (I was ironing out an imbalance) and the tail current dropped to less than 0.5% by the end. They were super-charged. By the next morning, they were back to the usual 25.something... ;-)

Oh yes! During the day the inverter delivers power to the loads by by-passing the batteries! At the same time the batteries get charged also.  After sun-set all loads have to be fed from the batteries. Therefore the voltage drops!  I'm learning slowly

Thank you all! Fantastic support here.