Battery charged less and less (solved)

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tom-g asked Aug 26, '19

Battery charged less and less (solved)

Hello, I have several solar panels and three different Victron Blue Solar chargers, a MultiPlus 12/3000, a BMV712 and CC GX installed. For the last several weeks I noticed that the Li Battery gets less and less charged, the charge cycle turns off at 93.5% by now. The charge slows down once the battery voltage on the BMV reaches 14.2V, though for the parameters enabled it should stop charging at 14.4V after three minutes.

I am looking for recommendations to charge the battery up to 99.5%, as it had worked like this for the last two years.

The only change in the installation is the addition of the CC GX and I replaced the MasterVolt inverter with a Victron MultiPlus 12/3000 (however, the unit is turned off most of the times), only the solar chargers are always on.

The system has worked very well so far, and I paid little attention. I also upgraded the firmware changes, as they became public. Since this is a gradual charge degradation, I wonder if any of the firmware changes causes this behavior.

battery charging

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Daniël Boekel (Victron Energy Staff) answered · Aug 30, 2019 at 10:16 AM

Hi @Tom G

A lithium (LiFePO4) battery is very much charged at 14.2 volts, so it seems the BMV is not properly configured.

If you can post your settings, others (or I) can help to configure it better.

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Answer 1 · 2019-08-30T12:32:47Z

tom-g answered · Aug 30, 2019 at 12:32 PM

Hello Daniel, thanks for getting back to me. It is a 540Ah Li battery on a boat, charged by either one or both of the engines, three separate solar chargers or the MultiPlus unit when I am in a marina. The charged voltage was set to 14.4V when we purchased the boat several years ago.

I have turned off the solar chargers and the battery charger / inverter, which leaves only the engine(s) to charge the battery. Which leaves the BMV as the only variable, here are the settings :

BMV 712 settings :

01 - 540Ah

02 - 14.4V

03 - 4%

04 - 3min

05 - 1.05

06 - 90% (I changed from 95%)

07 - 0.1A

08 - 3min

09 -

10 -

11 -

12 - Off

13 -

14 -

15 - 0

16 - 50%

17 - 90%

18 -

19 -

20 -

21 - 0V

22 -

23 -

24 -

25 - 0V

26 -

27 -

28 -

29 -

30 -

31 -

32 - On

33 -

34 - 20%

35 - 0V

36 -

37 -

38 -

39 -

40 -

41 -

42 - 0V

43 -

44 -

45 -

46 -

47 -

48 -

49 - 5

50 - Off

51 - 2

52 - On

53 - On

54 - On

55 - On

56 - On

57 - On

58 - On

59 -

60 -

61 = 4.01

62 -

63 -

64 - Off

65 - 500A

66 - 50mV

67 -

68 -

69 -

There are parameter 70 & 71 but no reference in the manual

Sent from my iPad

5

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Daniël Boekel (Victron Energy Staff) ♦♦ commented · Aug 30, 2019 at 05:16 PM

Hi @Tom G

01 - 540Ah - battery capacity

02 - 14.4V -

charged voltage - this is too high, a lithium battery is fully charged when at 13.8 volt (and no more amps flowing in) I'd set this to 13.8 volt

03 - 4%

tail current: this is the maximum charge current the battery has to accept at the 'charged voltage' for the SOC to reset back to 100%, 4% of 540Ah = 21A, I'd set it to 3% to begin.

04 - 3min

this is the time both the charged voltage, and the tail current must be met. As you have solar charging, I'd set this to 10 minutes, to prevent 'false positives' when the sun is low.

05 - 1.05

06 - 90% (I changed from 95%)

This I'd set to at least 95%, maybe even higher. this is the reason your SOC seems to get lower, because your battery is more efficient than 90% (Ah in/out)

Why did you change it to 90%?

What kind of batteries do you have? charging above 14 volts should not be needed, as this can reduce lifetime.

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klim8skeptic ♦ Daniël Boekel (Victron Energy Staff) ♦♦ commented · Aug 30, 2019 at 09:04 PM

Hi Daniel,

"this is the reason your SOC seems to get lower, because your battery is more efficient than 90% (Ah in/out)"

This sounds odd.

On a side note, I keep an eye on the BMV history, and my discharged/charged energy ratio is 95% (with the "charge efficiency factor" 99%). Is my 95% ratio figure of any practical use?

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tom-g Daniël Boekel (Victron Energy Staff) ♦♦ commented · Sep 02, 2019 at 07:49 AM

Hello Daniel,

your proposed settings did the trick, the battery charges again up to 100%. Even better than before, the charge cycle before seemed to hesitate to finish at 99.5-99.8%.

After changing the settings, the battery charge seemed to have 'jumped' from some 88% straight to 100% (I guess the correct charge parameters kicked in). Yesterday the batteries were gradually charged to 100%, with the amperage slowly tailing off as the SOC reached full charge.

We inherited the batteries when we bought our boat, supposedly Chinese Aircraft Li batteries. The voltage was always set to 14.4V, settings never rendered in two years. The only upgrade was from a BMV-700 to BMV-712 a few weeks ago. Something must have changed, 'not sure what.

I had edited the 'charge efficiency factor' to 90% to see if any changes occur, obviously in the wrong direction. Right now I am debating to bring it up to 99%.

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Daniël Boekel (Victron Energy Staff) ♦♦ tom-g commented · Sep 02, 2019 at 10:19 AM

Hi @Tom G

Please note that the BMV does not have anything todo with the charge parameters of the system, it only measures the State of Charge (SOC), and it can only do that when properly configured.

the charge parameters are configured in the chargers (PV charge controllers / inverters)

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tom-g Daniël Boekel (Victron Energy Staff) ♦♦ commented · Sep 02, 2019 at 02:48 PM

Good point. I checked the two SmartSolar Charger 100/30, the BlueSolar Charger 150/70 and the MultiPlus 12/300/120-16. All three solar chargers have the rotary switch set to LiFePo4 batteries and all variables are grayed out, not user selectable.

Kind of the same on the MultiPlus. The variables can be changed but once Li batteries are selected, all user settings are disabled to the default Li settings.

So if I change the Charge Efficiency Factor on the BMV-712 to >95%, the MultiPlus is still set at 95%.

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