We’ve recently bought a narrowboat with 2, 300ah LifePo4 lithium batteries and 1.8kw of solar panels. When we are not in the boat, I have turned off the 3KW Multiplus inverter and so there is only about 16w of DC being drawn, and batteries are sitting pretty much fully charged. We aren’t plugged into shore power, at least not during August and September. My MPPT app shows the absorption voltage set at 14.20V and the float voltage set to 13.50V. The smart shunt shows the charged Voltage set to 13.6V. I have 2 questions: 1. Am I right to leave the Inverter switched off and 2: Are the voltages for Absorption, float and charged Voltage set correctly? If I ask AI then I get advice that I should be changing these figures. I am new to this, trying hard to understand it and would welcome some advice. Cheers
Is this correct? Can only be answered by the manufacturer recommended values.
While lifepo4 is lifpo4, different brands have slight variations on the voltages.
All i can say is it is in the general ballpark for lithiums.
Thanks. If I recall, the AI none sense I read suggested that the float Voltage and charged voltage were incompatible…
Ha ha. Well to be fair it feeds of alot of bad advice on the internet.
For this one if you are synchronising to 100% ok then leave it for now.
Old addage of don’t fix what aint broke.
All of the kit is Victron, but I notice regularly that after a morning peak at 14.2v, then settling back to 13.5v, the Soc never shows 100%, it’s always 98% or there abouts. Previous owners suggested that this drift was normal and I should manually reset regularly. Key indicator being that the solar panels were only pulling in either nothing, or enough only to cover the drawdown, whilst the Soc was less than 100% - so at that point I should reset to 100% manually
Ok. Well some batteries float at 98%. But if never reaches the 100 that is different.
You should not have to manually sync it.
The mppt usually will only produce on a mobile system if the re bulk offset is reached which is often on default a little lower than float.
Victron kit for mppts have a preset for them, so you can’t get that wrong.
The shunt is guess can be adjusted. What are the other settings there? Can you post a screenshot?
This if you aren’t using it, makes sense. It noce that it can be switched off in the GX
Hope the pictures help! I did press the synchronise button a week or so ago, but it very quickly drifted off and wouldn’t show 100% after a 24 / 48 hours
Ok. A few comments.
15.4 AH consumed expressed as a percentage of 600AH is around 98%
15.4 ÷ 600 x 100 is 2.56% so 97.44% SOC ish. So that is close.
Peukert exponent: 1.05
Charged Voltage: 13.8V
Tail current: 4%
Charged detection time: 3m
Charge efficiency factor: 99%
Thanks. I haven’t digested the link, but scan reading quickly, then should I reduce the charged voltage to 13.2 or 13.3, so that it’s sits below the float voltage?
Sorry, misunderstood your comment….the settings you list are the settings I should adjust to?
Yes sorry, it was half baked answer. Those are the recommended settings on the shunt for victron lithiums, from the post linked
Much appreciated thanks
Just one final thought, during the winter months, I’m assuming that we’d be wise to plug in to shore power, even though there will still be very little battery draw, (unless I remotely switch on the webasto), so would these settings still” hold true for a plugged in set up?
They should not need to change at all unless you are still having synchronization issues. If all chargers have exactly the same settings, then it should be fine regardless of charge source. If not then we can revisit it all.
Very many thanks for your time
Having watched the video, then my charged voltage should be reduced to 14v, from 14.2, so that I’m 02% below….I think that’s what he’s saying?
