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The temp. compensation of battery for "cycling" mode and "float" mode are different.
For example, Exide AGM EP series specify 5.3 mv/C/cell vs 3.3 mv/Cell/C respectively. (32 mv/C vs 19.2 mv/C for 12V battery).
In the "Expert" mode of VictronConnect App, there is "only" one temp. comp value possible (for "Cycling" mode?).
I think it is important issue to clarify. Thank you!
Marin
Hi again!
I have installed recently SmartSolar 100/30 device on my boat.
I like the BT connected application. I would add a particular phase description (bulk, absorption, flat) on history graph for every point selected with cursor....otherwise, it is nice.
At first glance, it appears that the temp. compensation is reversed, i.e. charging voltage drops with temp. lower than 25C. But I will check next time I come.
However, the main problem I see is a battery overcharging!
The marine batteries are expensive. Thereby, I would like to share my opinion regarding device's setup in order to avoid a couple of years of battery's life only.
In my particular case, there are EXIDE EP900 batteries installed.
There is a clear max. the voltage that the battery can withstand without gassing, regardless of temperature and that is 14.7 V!
The lowest charging voltage regardless of temperature is 13.2 V!
PERIOD!
In addition, 14.6 V is even explicitly written on the EP900 as max. applied voltage.
I would add that is the same for the FLOAT voltage of 13.8 V max.
Btw, the AGM battery is very sensitive to overcharging i.e. gassing, caused by high applied voltage for a long time.
Now, take a look at chart bellow, considering recommended Uabs=14.4V and Ufloat=13.8V.
BAGI_SE_Victron_TC_14v4_13v8.pdf
It is obvious that already at 18C, there is a critical voltage applied (with 30 mV/C comp.) and at 15C considering 19.8 mv/C temp. compensation.
Considering the float voltage is even worse. It is hard to understand that Victron device could apply almost max. allowed voltage to a battery in Float state (14.55V at 0C).
If you put another initial conditions: Uabs=14.1V and Ufloat=13.5V it is quite better as you can see on chart bellow.
BAGI_SE_Victron_TC_14v1_13v5.pdf
However, even there, at 8C and with cycle temp. comp. parameter of 30 mV/C, the applied voltage becomes too high.
I would like to point out that "SmartSolar" MPPT devices do not have the ability to set limits in the charging profile (UmaxAbsorption and UmaxFloat), leading to premature battery(expensive) failure.
It means that a buying SmartSense device does not help you at all!!
Without the ability to set limits in the battery charging profile, buying a SmartSense device would be a waste of money.
So, the solution I chose was to use lower initial parameters (Uabs=14.1 V, Ufloat=13.5V, Tempcomp=Floatcomp=19.8 mV/C).
In conclusion, I would say that even turning off the temperature compensation and setting the appropriate initial conditions is better than overcharging the battery with "recommended" values.
I hope the people in charge at Victron will fix the existing firmware as it could be harming your batteries.
Regards.
How are you going to use your batteries.
1. If you are going to use them in a system like a UPS or back up power that will spend most of its time at float charge and full with occasional use then use the float value.
2. If you are going to use the batteries in sn energy storsge from solar or boat or RV where they get charged each day and then discharged overnight use the cycling value.
Only you know how the batteries will be used.
Hi,
Thanks for your kind answer.
However, in solar system installed on the boat, there are both cases present.
During a time being on the boat, the cycling mode is used by nature and opposite in case of absence when there is no discharging, consequently being most of the time during a day in float mode.
In my opinion, there in menu of expert mode, should’nt be only one value but two of them: cycling-absorption value and float value as well.
On top of that, the system should use them accordingly corelated to the current state of charger.
Otherwise, at low temperature and cycling temp. comp. value, the battery will be overcharged and at high temperature with float value as well.
Regards.
There's no way an MPPT can know how you will use the system.
The effect of temp compensation depends a lot on your local temperature ranges.
One option would be to set the float value for winter when you're going to use the boat less, if at all. And set the cycle value for summer. It's a simple and quick job with Victron Connect.
Solar will give very little charge during winter in many areas, anyway.
Hi,
Thanks a lot!
I have 400W solar panel on top of roof of the boat and yes, use it all year around.
However, there are ,sometime, weeks of not using it and I am not the only one.
This scenario is very common in nautical environment.
Additionaly, in Croatia is quite sunny during a winter too, producing a lot of energy, used mainly for Webasto heating and refrigerator.
Your hint is good but somewhat annoying in terms of setup changing.
Might be a good solution to change temp. comp. value automatically from "cycling" to "float" when battery temperature drops bellow 15C or so....
What do you think?
Regards
