Strange B2B behaviour/ power drain

[autorouter]

You have a Victron Orion XS DC-DC charger (B2B). In photo 0943 it says it is in the Bulk charge mode. Its input is 13.3V 50A from the alternator, which is the maximum amps for an Orion XS. The power (watts) taken from the alternator is 13.3 x 50.0 = 665W.

The B2B output is 13.8V 47.1A. The B2B pushes out the maximum amps that is capable of, as the battery voltage gradually rises. Here it has reached 13.8V. The power output (watts) from the B2B is 13.8 x 47.1 = 652W. You can see that there is a bit of power lost inside the B2B as it converts the voltage. 665W - 652W = 13W. As a percentage that's (13 / 665) x 100 = 2 percent, so very efficient.

The output voltage should gradually rise as the battery fills up. If it's lithium, when it reaches the 'absorption voltage' it's probably supposed to just stop charging. The voltage will remain at about the absorption voltage (14.1V), and the amps will drop to zero. So the snapshot of photo 0944 is correct.

The 'absorption voltage' and 'float voltage' are not relevant for lithium batteries, they are a relic from lead-acid battery charging profiles. For a lithium battery, the important quantity is the voltage that shows the battery is full, when the charger cuts off. If you had a charger that was designed only for lithium batteries, you would call that voltage the 'Cutoff Voltage'. But since the charger can do both lead-acid and lithium, they keep the old name of 'Absorption voltage'. Even though a lithium battery doesn't require an absorption stage, and doesn't require float charging.

 

[ChrisL]

Fogstar recommend 14.2v for charging with Victron equipment (used to be 14.1).
I have mine set at 14.25 as some people have had problems with them not getting to 100% at 14.2v.
Float voltage should be 13.5v as the battery won't take a charge at that voltage and you shouldn't float Lithium's.

In my case I started off at 14.2v but the B2B was not fully charging the battery, I then went to 14.25 and ultimately ended up at 14.3v before it worked as expected, also remember that the B2B doesn't get actual battery voltage from the shunt so 14.3v output is likely to be a bit less at the battery. In the case of the float voltage I have a CBE battery maintainer for the starter battery and that requires over 13.6v to work, so i'm hoping the extra 0.11v doesn't take too much off the life of the battery.

 

[StillGoing]

settings I thinkView attachment 1000533

Why don’t you use D+ to control the B2B? It’s much more reliable.

 

[Raul]

Why don’t you use D+ to control the B2B? It’s much more reliable.

If you got it? Yes that would be my preferred option as well, instead of the engine detection.

 

[Raul]

In my case I started off at 14.2v but the B2B was not fully charging the battery, I then went to 14.25 and ultimately ended up at 14.3v before it worked as expected, also remember that the B2B doesn't get actual battery voltage from the shunt so 14.3v output is likely to be a bit less at the battery. In the case of the float voltage I have a CBE battery maintainer for the starter battery and that requires over 13.6v to work, so i'm hoping the extra 0.11v doesn't take too much off the life of the battery.

My solar chargers are set at 14.05v with 13.5v float. Anything above this you will try to squeeze another 2-3Ah into a 300-500Ah battery. Why? My thinking is, I you have a pretty good large capacity, don't try to push in the last 3-4Ah into the battery, and keep it pinned at high voltage for too long.
Just a thought.

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[ChrisL]

Why don’t you use D+ to control the B2B? It’s much more reliable.

If you're considering using the D+ to trigger the B2B then this video by RogerIvy should help.