I am planning an upgrade on our boat’s house bank, changing from AGM to Victron LiFePO.
The new bank will have either 4 x 24v/200AH batteries or preferably 3 x 24v/300AH batteries of the new “NG” line resulting in a 24v/800 or 900AH bank.
I’ll use Lynx Distributors, a Lynx BMS and a Cerbo GX as well as our existing 24v/3000 Multiplus (v1 not II).
I have a few questions:
New Victron NG battery line vs Victron Smart Lithium Batteries: I’m aware of, and like the new features available on the NG line. But from a daily usage and performance as a house bank on a boat (DOD, charging time, etc) should I expect much difference from a battery from the existing Smart Lithium models? And…is it likely that the existing stock of Smart Lithium will go on closeout pricing soon since they are being replaced by the new NG line?
With an 800 to 900AH house bank I need more charging current than just the 70 amps the Multiplus can provide. (I don’t want to run our generator at anchor for too many house each day). Can I daisy-chain a new Multiplus II with my existing Multiplus (first generation) and have them communicate for smart charging as a team? Or…could I daisy chain my existing old Multiplus with one or more Phoenix smart chargers and have them all communicate?
According to Victron, within 3 years it would be acceptable and safe to expand my battery bank by adding an additional Victron battery of the same voltage (and chemisty obviously) and it could even be a different AH capacity. Any insight or comments on this aspect are welcomed.
Hello @Keith7WA . I wonder what type of vessel it is you have? You are describing a fairly big house bank so I wonder the size of the vessel and if you have done a DC current “budget” to know what your daily needs are? Also, does the vessel have any solar capacity and if not, would you consider adding that?
I wouldn’t expect much difference between lithium battery performance from the smart batteries to the NG batteries. I would expect better BMS communications so you have a better idea of the state of the battery.
You wouldnt “Daisy Chain” the multiplusses as that implies a series connection. You can run charging sources in parallel however no problem.
It is best to simply have a house bank made up of the same battery type and age. This allows each battery to contribute equally to the house bank. Older batteries may have slightly different characteristics than a newer battery so may not load share or charge equally to the other batteries. Having said that if more capacity is required, having different age batteries would be better than not having them at all.
Re: “Daisychain” - I should have been more clear. I know that when you connect 2 or more Multipluses in parallel you can multiply your charging capability. My understanding is that you designate one of the units as a ‘Master’ and the paralleled units will follow it’s lead for the charging profile. I understand this communication is achieved via VE.bus connection. My question is if the first gen Multiplus can do this communication with the second gen Multiplus-II? (Can the old guy communicate to the young guy?)
For more context:
We have a 60 foot trawler. The current AGM house bank is made up of 12 x 12v 200Ah batteries in series/parallel to make a 1,200Ah 24v house bank. (about 1,500 lbs!). We also have separate banks for bow thruster, stern thruster, main engine start and genset start. Those will all remain AGM as that is a more appropriate chemistry for brief high amperage but low depth of discharge use.
A reasonable DOD for our current AGM house bank is 50% which yields a usable 600Ah. With Lithiums I’m comfortable with a 75% DOD so an 800Ah bank will yield the equivalent usable 600Ah. (and yes you can certainly go deeper than 75% now and then!)
Our nominal draw at anchor overnight is 14-18 amps with intermittent, much higher, but brief draws during the day for things like using the microwave.
No current plans to add solar since we don’t really need it.
@Keith7WA it sounds like you have it well thought out for the 60 footer. You can run different charging sources in parallel if the charging current of the multiplus is not enough.
To keep it a bit brief:
1: No, the performance of the existing line Lithium Smart line will be virtually identical to the performance of the Lithium NG line in terms of daily usage - the primary benefit to the NG line comes in the different available capacities, mounting orientation, and potential to create a vast battery bank. Your bank is relatively modest, so not using the latter feature.
1a: Possibly, but that would not be for a considerable amount of time, after the NG batteries have ramped up in production and stock globally.
2: No. For MultiPlus or Quattro units to communicate with each other they need to be identical units. Depending on the age of your existing 24/3kVA Multi, though, you can very likely just get another one of those to put in parallel with your existing, or alternatively sell your existing on the used market and buy 2 new Multi-IIs.
3: No personal insight to that, nor assurance as to whether this will equally apply to the NG line as it apparently does to the Lithium Smart line. I’m not concerned about the age so much, as LFP that’s taken care of properly ages very slowly, but I personally question the wisdom of adding a new battery of a different capacity… but they do say it can be done!
As a note, please be aware that the NG line and the Lithium Smart line are not cross-compatible, so for instance one could not later add a Lithium NG battery to an existing Lithium Smart battery bank, and vice-versa.
I am getting conflicting info about the possibility of controlling two or more Multipluses via DVCC. Is it correct that they have to be identical hardware units (not just current firmware versions) in order to work? And either way can two units, in parallel, be controlled simultaneously via DVCC with the Cerbo GX?
Lastly, assuming they are all connected via the proper data cables, can the two Multipluses be in two different locations with somewhat different charging cable lengths? All of suitable gauge for the distance of course.
