Hiya Booster. I never thought to ask why Victron has a seemingly high cut in voltage. My portable panels are wired in 2S2P for a nominal 24 volt setup so really not a concern for us.
I'm currently using AGM batteries with preferred absorption of 14.4-15v and 13.5-13.8 float.
The Victron has what they call "adaptive" float charging. It senses the charged stat of the batteries at start up and decides how long to float charge that day. A gimmick? I dunno but it seems to have worked well for tje 2+ years we've had it. The adaptive is user switchable, it can be turned off for a timed absorb.
There is also a tail current settingthat I think overides both of the above. I have ours set at 3 amps for 200+AH. The reason for the plus is that Weize uses a 10 hour rating for measuring AHs instead of the "standard" 20 hour rate. The 3 amp tail current would seem to be a good guess what with a .6 to .7 amp parasitic load. I have the absorption set at 14.6 and float at 13.6
The rebulk setting on the Victron(100/30 smart solar) follows the float voltage setting. I have this set at 13.4(a .2v drop) as I don't think that I want to wait on bulk charging if needed. The magic in the controller does get it to absorb then float quite quickly in a rebulk situation.
It should be noted that the AGM batteries are a new install that replaced maintenance free L/A batteries that were still performing well with at least 90% of capacity(measured). We have not boondocked with them as yet but will be next month.
I replaced them early 'cuz I scored the Weize group 31 batteries for $149 at Amazon as batteries seem to have jumped hard in price lately. The group 31 "deep cycle" L/A batteries seem to have gone up to about $150 to 160 recently, hence the purchase of the $149 Weize batteries that are now $165.
Great details, it is always good to get the whole story in on shot and not piecemeal and/or inconsistent.
If the Victron has a tail amp setting, does it also have access to a shunt to see the actual amps at the battery. I ask because the first charger we had with tail amp settings was a Blue Sea that was a really good charger in general, but the tail amps were measured within the charger so any coach loads or any current going the the starter battery though the separator got counted. Those are variable loads so make it kind not a great feature to have tail amps.
I am not familiar with those batteries so will need to see what I can find on them. It is very possible they won't list the recommended tail amps as most of the time you have to contact manufacturers to get it. Lifeline is the exception to that and actually push the use of tail amp controlled charging. The most common tail amp settings I have seen or heard about are in the .5-1.0% of ah rating of the batteries. TPPL will have as low as .1%. Lifeline specs .5% but there batteries, especially when new will actually go much lower than that to .2% but it takes a long time beyond the already long (about 8-10 hours from 50% with a 80-100amps of charging available) so the .5 is probably a bit better to prevent excessive dry out. An interesting thing is too look at the float current when it goes to float after a full charge to tail amps. It will go negative first as the surface charge that is between the float voltage and absorption voltage comes off. Then our batteries, which are set at 2.0amps tail amps for our 440ah bank, show around .3amps at float at 13.1v where I like to float it long term to limit dryout. Over the next 48 hours that float amp reading slowly drops to about .05amps so I would say it did fill the batteries a bit more, I think. Many times if the van is in winter layup, I will then unplug it and let it sit a 4-6 weeks, then discharge it to 20% and recharge to full just to give some rest time and reactivation regularly. I have no clue if this better or worse than staying plugged in but it just makes sense to me.
If you are a data, and how does this work(?), junkie like I am you might want to put the charger into tail amp charging control if it is on a shunt and set the tail current very low to see how low it goes before it stops changing over some time. On ours if it went 4 hours without changing that is where I stopped, but 2 would probably be fine and maybe even better. Then move the tail amp setting above what you saw for amps above and watch the amps which will likely go negative and then positive. Let it run a while in float to see if it drops over time and where it ends. For comparison just run down the batteries a ways and set it to the settings you are using currently and run the same last part of the above test. It will automatically go to float at some time and just where the float voltage stabilizes quickly after going positive and how long it takes to hit the lowest float voltage. Compare the two tests and you should be able to tell if your current settings are good for your brand of batteries and charge voltages. The Lifeline chart in their tech manual shows 10hr rate gives about 7% less ah capacity rating than at 20hr rate. Yours are probably similar so you can adjust your rating to 20 hr for comparison the more common 20 hour rating for things like capacity, tail amps, run time, etc. In real world use our average (which is what counts) rate is closer to the 100 hour rate.
If you have shore charger that can also do tail amp controlled charging it really helps in being able to determine what to do with solar settings as you want to be certain that the solar is getting to float a bit before the shore charger does. The reason is if the solar is not tripped to float already by the tail amps when the shore goes to float the solar will keep charging until it trips on tail amps. Even if set to same setting this can happen as they may look at the time at the amps before tripping differently or slightly different calculations methods. If it still charging when other sources go off, and the conditions are right as described above, it can get the in between float and absorption voltage that it can stay in for way longer than full batteries should seen.
You are higher in both float and absorption voltage than I run and also could easily be a bit high on tail amps also. Tail amps do change with voltage by a bit so that can be a bit of oddness, and even lifeline doesn't specifically call out the suggested tail amps voltage point within their range. I stay at very bottom of the ranges for both float and absorption at 13.1v and 14.2v and use the recommended .5%C tail amps. It takes only a minimal amount of extra time to get a full charge at the low end absorption compared to high end and when you are talking about 8*10 hours anyway it is never an issue. The solar is set a .1v lower for absorption and 12.8v for float with the tail amps set .3amps higher. Alternator is set at 14.3v and 13.1v and I can force to float when I want while drive or shut off the coach charging from the alternator by looking at the amps on the ammeter I have in the cockpit.
I think the big deal, and which certainly is related to this thread is that getting all the parts to work well together and not do bad things is the hard part of it all and solar is probably hardest on to deal with because the output is so incredibly variable that it is hard have it always to do the right thing. It may be even more important with lithium as having it run all day locked in at near full charge voltage could be a bad thing on full batteries and getting it to always turn on to full voltage when needed might be a bit harder because of the low voltage drop with discharge % that lithium has.
Hopefully the OP will get a controller that reacts well to his other components or is at least on the conservative side. The overcharging issue is the reason, I am sure, that many solar controllers limit absorption voltage charging to a low time frame like 4 hours total per day.
