Hi everybody,
I have 2 SmartSolar MPPTs to charge my AGM batteries on my sailing boat, and monitor with a Smartshunt. I observed that when I am sailing for longer periods, after a couple of days, the batteries are not charged higher than 95% eventhough there is a lot of sun (or even engine with alternator charging), after a couple of weeks not more than 90%, and after some months not more than 85%. When I connect to shore power, after a couple of days they would be back at 100% and we start the same procedure all over. Does anybody have an eyplanation for this, and even better, a fix? 
Cheers,
Nikolas
There is a FAQ thread that is useful, it sounds like you need your solar controller or SmartShunt settings updating so it synchronises. If you have no joy after reading these then post us a screenshot of your settings.
It could also be a wiring issue per second FAQ, but that is less likely.
Hi! Wow, thanks so much, I think the first FAQ is on the right track. However, as I am very new to this topic, I would be super happy if you could corss-check with me, as my idea now is to re-aarange the tail current (see pictures attached):
What do you think?
Thank you soo much!!
At the moment I suggest you reduce Peukert exponent to 1.15, this is a better value for AGM.
Can you make a plot of voltage and current and tell me what absorption voltage you have on your solar controller. The voltage is the thing to get right first. My expectation is the solar is not getting the voltage high enough. Also, what voltage does the alternator charge at.
Leave the tail current alone at the moment as you need the voltage right first. 4% should make it easy to synchronise, once optimised you could reduce this to 2% later on.
Finally, it may be the case that you ate genuinely under charging your batteries.
Ok, lets hope for the best.
As we only have little sun atm (currently in Brazil), i will make the plot hopefully in the next days. Attached is a plot when starting my engine. The alternator is new, should charge well above 14.4V..
So the voltage of the battery goes up to the maximum voltage, but the SOC doesnt..
Ok, your voltage on that plot only goes up to 14.3V and the charged voltage setting in the SmartShunt is 14.4V. Therefore, the SmartShunt will never reset to 100% from the alternator. You need to reduce the charged voltage on the SmartShunt to 14.2V then it should reset to 100%. If it does this then the next step is to consider trying 2% tail current and making sure it still rests at 2%. You probably have a similar voltage problem with the sola controller not getting above 14.4V.
Great, will do so. Thanks so much!
This is the setting for the MPPT100/50
As I understand, I should reduce the Absorption voltage probably, right?
I used to run my AGMs at 14.4V in the UK, running AGMs at too high a voltage in hot climates can cause issues so try 14.4V.
Ok will do.
Now that I have changed the voltage on tje smart shunt to 14.2, it seems the alternator only very slowly remains charging at low currents already below 80% SOC (see pictures). I am quite confused.
Changing the SmartShunt voltage should not affect the alternator performance at all, it should go up to 14.3V as in your other charts.
I think you have something very odd happening with your system and it is hard to diagnose this remotely with limited information, check that you have no loose connections anywhere or problems with voltage loss. Do you have a multimeter, if so check the voltage at the alternator output and at the batteries.
Allright, doesn‘t sound like a 5 minute job unfortunately. I will get into this and give feedback when I know more. Thanks for all your help though, highly appreciated! 
Now this happened after connecting to shore power. Charging to 100% like in a minute. so it is not the battries EoL but control issue?
Because the Shunt detected a high voltage and a low current at the same time which is what resets it automatically to 100%, these are the signs of a full battery. This normally happens when the SOC drifts because the settings are not optimised and you do not get the 100% reset very often, the SOC drifts further and further even though you are getting close to 100% full, the triggers for reset to 100% are not quite met. You think the batteries are partially discharged but the are in fact quite close to full. then when you get the shorepower which is a more reliable source of power than alternator or solar, it gets the reset. The trick is to get the settings optimised so it does not drift as much (Peukert to 1.15 as noted above) and then to get the charged voltage and tail current set so they trigger with the alternator or solar.
The charge efficiency factor, on my high quality AGMs I have a value of 98 or 99%, this may reduce you drift. Keep the 4% tail current and make sure that the charged voltage on the SmarShunt is lower than alternator and solar achieve.
Woar, thanks so much for this very thorough explanation. That makes sense and is very good news, i guess, as it does not imply new investment 
i will reset accorsing to your suggestions and keep you posted. Thanks a lot! 
Hi pw farnell,
Hoping for your kind support again.
When disconnecting my batteries from shore power yesterday, and after the sun dissapeared, the voltage and SOC dropped very quickly while only a minor load was connected, or at least not a hige one (see picture). Is this still about the settings being set incorrectly or some physical problems?
At the beginning, the voltage dropped from 13.3 to 12.5 within less than 45 minutes, and the SOC followed. It seems unusual to me, at least I have not experienced this behavior during the past year..
Once charging stops then the battery voltage will rapidly drop to 12.7V, the charger is holding it at 13.3. Note that the slope of the SOC changed part way through and the voltage increased when this happened. If the load on the batteries was low then you would not see this effect so much on the voltage, the batteries should have stayed up at 12.7 to 12.8V. It looks like you did have a load on the system even if you did not think so.
If you plot the current going through the SmartShunt you should see something. You batteries lost about 17% of charge, so 400Ah means a loss of 68Ah over 16 hours, that is an average of 4.25A, which could easily be something like lights left on or other small user.
Possibly a short circuit, but a failed alternator can also allow current to flow backwards. Check for warm cables / warm equipment.
Ok I did the same calculation but the idea about a short circuit is new, thanks a lot. I will follow this and keep you posted, thanks a lot - once again!
I was helping someone recently on a boat that was having problem and they found an external search light was on.