I just completed an installation of four 200NG lithium batteries, Lynx BMS and distributors, CerboGX with display, and Quattro inverter/charger. All is well except charge voltage from the Quattro never drops below 13.7v. The display never shows “float”, it just hangs in “absorption” with the voltage never dropping below 13.7. In my previous installations (Lithium Smart batteries, non-NG), the voltage would eventually drop to 13.5 in float. I understand that the BMS is controlling it. My only concern is whether 13.7 is a level that will cause damage.
The Quattro will never show float, it is now under external control from the Lynx BMS.
I noticed the 13.7V with my NG install and have raised it with Victron. The Lynx BMS is conyrolling this. The manual states 13.5V. It is possible to limit this in the DVCC settings, limit charge voltage, but it will not allow absorption if you do this.
Thank you. I’m not bothered by it not showing “float”. Just didn’t want to be overcharging over a long period of time. Maybe they will make a correction/update in the future.
Thinking further about this, maybe the bms is stipulating a charge voltage that satisfies what it sees as correct for cell voltage rather than entire battery voltage, including any external connection deficiencies.
No, the battery is sending a CVL of 13.7V even when the battery is balanced and there is no current flow so no voltage drop.
Good point, no voltage drop involved.
I have just finished an install on a boat using 24v 300NG batteries, Lynx NG BMS, Cerbo GX and Multiplus 24/3000 inverter/charger. Everything seems to be working extremely well and I’m VERY impressed with the performance of these batteries so far!
My question is exactly the same. While the boat is at the slip, plugged in to shorepower and being charged/maintained under DVCC the charger never shows ‘Float’, always ‘Absorbtion’ (or idle) and holds the batteries at 27.4v. Just like you I am concerned that this voltage is too high for weeks-long storage and my understanding form the documentation is that the DVCC was supposed to allow the batteries to come down to, and stay at a float voltage of 27v after they were fully charged.
I currently just manually limit the voltage to 27v using the ‘limit charge voltage’ function, but I shouldn’t have to do this.
Peter, did you ever hear anything back from Victron on this issue?
Mine is a 12V install so trying to run at 13.7V, but I have added a Node-RED code so it runs at 14.0 / 13.5V. I will give them a prompt.
Thank you again!
Hi @schaefersc @Keith7WA @pwfarnell
The good news is that there is no unintended behaviour here from Victron’s perspective. Both 13.5V & 13.7V (and their 24/48 nominal equivilents) are acceptable and normal for the NG series.
The documentation is inconsistent with this, and is a bit confusing, but it’s going to stay like this for now.
We have ongoing refinement tests and research, and the current default operational settings of 13.7V for float with 0Amps charge, without drawing down on the batteries to hit a lower (like 13.5V) float voltage seem to be giving the best results.
We may return with more information, updated documentation and adjustments around these thresholds through the testing process.
If you override this some how with node red or otherwise to force 13.5V, also fine, but then please return to the defaults before seeking any kind of support for other issues.
Right now, both 13.7V and 13.5V are valid float voltage levels.
The float/absorption labelling is an outstanding issue, and hopefully resolved, but has no operational difference. The systems are charging as expected.
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Thank you Guy, that is surprising and important, but at least good news to know the system is functioning as intended!
On a related note, there is talk that for LiFePO batteries that are not being used for a long-ish period of time, like when a boat is in port for a month and connected to shore power, that floating them at a lower SOC, say 80% may have benefits for longevity of the batteries. Is this the case for the NG batteries and would you recommend this? Assuming of course you bring them to a proper 100% and equalized SOC before using them again.
As long as the cells are rebalanced before cycling, then I would say it does no harm and possibly some good to leave the cells ~80% for longer term storage.
Also, as an aside it’s common to discharge to 50% or less for transport so there is less stored energy in case of an accident.
But both of those are very generalised, as far as I know Victron hasn’t released any specific advice for these alternative situations and the NG battery. Perhaps over time there will be more guidance.
For now I would be comfortable using the batteries, settings and software as the engineers are intending.
Perfect - thank you Guy.
Thank you for all this information.