diy solar

diy solar

MPPT SoC Metric

wheresthesun

New Member
Joined
Jul 24, 2020
Messages
29
Noob alert.
I recently got an MPPT (Tracer AN 30A). I have a script running every minute that queries via the RS485 port. I log this info to a local database. I have been noticing that the Battery SoC decreases as soon as the sun disappears. At the moment is at about 63%. This is a brand new AGM 95Ahr battery. Am I missing something about how this should work or might there be something wrong?


You can see the last few hours below with the diminshing SoC.

+---------+-------+------+---------------------+
| voltage | temp | SoC | time |
+---------+-------+------+---------------------+
| 13.82 | 21.9 | 98 | 2020-08-14 18:36:01 |
| 13.82 | 21.89 | 98 | 2020-08-14 18:37:02 |
| 13.8 | 21.79 | 98 | 2020-08-14 18:38:01 |
| 13.8 | 21.89 | 98 | 2020-08-14 18:39:02 |
| 13.82 | 21.9 | 97 | 2020-08-14 18:40:01 |
| 13.8 | 21.92 | 98 | 2020-08-14 18:41:01 |
| 13.8 | 21.88 | 98 | 2020-08-14 18:42:02 |
| 13.78 | 21.88 | 97 | 2020-08-14 18:43:01 |
| 13.78 | 21.9 | 97 | 2020-08-14 18:44:02 |
| 13.78 | 21.88 | 97 | 2020-08-14 18:45:01 |
| 13.8 | 21.87 | 98 | 2020-08-14 18:46:02 |
| 13.79 | 21.92 | 97 | 2020-08-14 18:47:01 |
| 13.78 | 21.85 | 97 | 2020-08-14 18:48:02 |
| 13.79 | 21.87 | 97 | 2020-08-14 18:49:01 |
| 13.79 | 21.87 | 97 | 2020-08-14 18:50:02 |
| 13.76 | 21.84 | 97 | 2020-08-14 18:51:01 |
| 13.79 | 21.84 | 96 | 2020-08-14 18:52:02 |
| 13.78 | 21.82 | 98 | 2020-08-14 18:53:02 |
| 13.84 | 21.9 | 99 | 2020-08-14 18:54:01 |
| 13.91 | 21.88 | 100 | 2020-08-14 18:55:02 |
| 13.92 | 21.87 | 100 | 2020-08-14 18:56:01 |
| 13.92 | 21.86 | 100 | 2020-08-14 18:57:02 |
| 13.93 | 21.87 | 100 | 2020-08-14 18:58:01 |
| 13.92 | 21.85 | 100 | 2020-08-14 18:59:02 |
| 13.92 | 21.84 | 100 | 2020-08-14 19:00:01 |
| 13.9 | 21.81 | 100 | 2020-08-14 19:01:02 |
| 13.9 | 21.82 | 100 | 2020-08-14 19:02:01 |
| 13.89 | 21.85 | 100 | 2020-08-14 19:03:01 |
| 13.89 | 21.82 | 100 | 2020-08-14 19:04:02 |
| 13.88 | 21.77 | 100 | 2020-08-14 19:05:01 |
| 13.87 | 21.77 | 100 | 2020-08-14 19:06:02 |
| 13.88 | 21.75 | 100 | 2020-08-14 19:07:01 |
| 13.86 | 21.78 | 100 | 2020-08-14 19:08:02 |
| 13.88 | 21.76 | 100 | 2020-08-14 19:09:01 |
| 13.87 | 21.77 | 100 | 2020-08-14 19:10:02 |
| 13.87 | 21.76 | 100 | 2020-08-14 19:11:01 |
| 13.85 | 21.73 | 100 | 2020-08-14 19:12:02 |
| 13.84 | 21.72 | 99 | 2020-08-14 19:13:01 |
| 13.84 | 21.73 | 99 | 2020-08-14 19:14:01 |
| 13.83 | 21.7 | 99 | 2020-08-14 19:15:02 |
| 13.83 | 21.71 | 99 | 2020-08-14 19:16:01 |
| 13.83 | 21.67 | 99 | 2020-08-14 19:17:02 |
| 13.81 | 21.68 | 98 | 2020-08-14 19:18:01 |
| 13.82 | 21.6 | 98 | 2020-08-14 19:19:02 |
| 13.8 | 21.65 | 97 | 2020-08-14 19:20:01 |
| 13.8 | 21.63 | 97 | 2020-08-14 19:21:02 |
| 13.79 | 21.66 | 98 | 2020-08-14 19:22:01 |
| 13.79 | 21.62 | 97 | 2020-08-14 19:23:02 |
| 13.87 | 21.67 | 100 | 2020-08-14 19:24:02 |
| 13.91 | 21.65 | 100 | 2020-08-14 19:25:01 |
| 13.89 | 21.64 | 100 | 2020-08-14 19:26:02 |
| 13.86 | 21.62 | 100 | 2020-08-14 19:27:01 |
| 13.87 | 21.59 | 100 | 2020-08-14 19:28:02 |
| 13.86 | 21.57 | 100 | 2020-08-14 19:29:01 |
| 13.86 | 21.56 | 100 | 2020-08-14 19:30:02 |
| 13.86 | 21.56 | 99 | 2020-08-14 19:31:01 |
| 13.83 | 21.53 | 98 | 2020-08-14 19:32:02 |
| 13.83 | 21.51 | 98 | 2020-08-14 19:33:01 |
| 13.8 | 21.52 | 97 | 2020-08-14 19:34:02 |
| 13.81 | 21.51 | 98 | 2020-08-14 19:35:02 |
| 13.78 | 21.5 | 97 | 2020-08-14 19:36:01 |
| 13.79 | 21.48 | 97 | 2020-08-14 19:37:02 |
| 13.79 | 21.48 | 97 | 2020-08-14 19:38:01 |
| 13.78 | 21.48 | 97 | 2020-08-14 19:39:02 |
| 13.8 | 21.45 | 97 | 2020-08-14 19:40:01 |
| 13.79 | 21.43 | 97 | 2020-08-14 19:41:02 |
| 13.78 | 21.39 | 97 | 2020-08-14 19:42:01 |
| 13.79 | 21.38 | 97 | 2020-08-14 19:43:02 |
| 13.8 | 21.4 | 97 | 2020-08-14 19:44:01 |
| 13.8 | 21.4 | 97 | 2020-08-14 19:45:02 |
| 13.8 | 21.36 | 97 | 2020-08-14 19:46:02 |
| 13.79 | 21.37 | 97 | 2020-08-14 19:47:01 |
| 13.79 | 21.36 | 97 | 2020-08-14 19:48:02 |
| 13.8 | 21.34 | 97 | 2020-08-14 19:49:01 |
| 13.79 | 21.33 | 97 | 2020-08-14 19:50:02 |
| 13.79 | 21.32 | 97 | 2020-08-14 19:51:01 |
| 13.79 | 21.27 | 97 | 2020-08-14 19:52:02 |
| 13.79 | 21.29 | 97 | 2020-08-14 19:53:01 |
| 13.78 | 21.3 | 97 | 2020-08-14 19:54:02 |
| 13.79 | 21.27 | 97 | 2020-08-14 19:55:01 |
| 13.78 | 21.25 | 97 | 2020-08-14 19:56:01 |
| 13.81 | 21.26 | 98 | 2020-08-14 19:57:02 |
| 13.8 | 21.21 | 97 | 2020-08-14 19:58:01 |
| 13.8 | 21.23 | 97 | 2020-08-14 19:59:02 |
| 13.78 | 21.22 | 97 | 2020-08-14 20:00:01 |
| 13.79 | 21.2 | 96 | 2020-08-14 20:01:02 |
| 13.78 | 21.2 | 97 | 2020-08-14 20:02:01 |
| 13.8 | 21.17 | 97 | 2020-08-14 20:03:02 |
| 13.81 | 21.17 | 98 | 2020-08-14 20:04:01 |
| 13.78 | 21.14 | 97 | 2020-08-14 20:05:02 |
| 13.79 | 21.11 | 97 | 2020-08-14 20:06:02 |
| 13.78 | 21.12 | 97 | 2020-08-14 20:07:01 |
| 13.8 | 21.12 | 97 | 2020-08-14 20:08:02 |
| 13.81 | 21.12 | 97 | 2020-08-14 20:09:01 |
| 13.8 | 21.11 | 97 | 2020-08-14 20:10:02 |
| 13.8 | 21.09 | 96 | 2020-08-14 20:11:01 |
| 13.8 | 21.09 | 97 | 2020-08-14 20:12:02 |
| 13.78 | 21.07 | 96 | 2020-08-14 20:13:01 |
| 13.79 | 21.08 | 97 | 2020-08-14 20:14:02 |
| 13.79 | 21.06 | 97 | 2020-08-14 20:15:01 |
| 13.79 | 21.04 | 97 | 2020-08-14 20:16:01 |
| 13.8 | 21.01 | 97 | 2020-08-14 20:17:02 |
| 13.8 | 21.01 | 97 | 2020-08-14 20:18:01 |
| 13.8 | 21 | 97 | 2020-08-14 20:19:02 |
| 13.79 | 21 | 97 | 2020-08-14 20:20:01 |
| 13.8 | 20.95 | 97 | 2020-08-14 20:21:02 |
| 13.78 | 20.96 | 96 | 2020-08-14 20:22:01 |
| 13.75 | 20.94 | 95 | 2020-08-14 20:23:02 |
| 13.71 | 20.95 | 94 | 2020-08-14 20:24:01 |
| 13.61 | 20.94 | 90 | 2020-08-14 20:25:02 |
| 13.51 | 20.93 | 87 | 2020-08-14 20:26:02 |
| 13.36 | 20.88 | 81 | 2020-08-14 20:27:01 |
| 13.23 | 20.89 | 77 | 2020-08-14 20:28:02 |
| 13.13 | 20.83 | 74 | 2020-08-14 20:29:01 |
| 13.09 | 20.86 | 72 | 2020-08-14 20:30:02 |
| 13.06 | 20.82 | 71 | 2020-08-14 20:31:01 |
| 13.04 | 20.85 | 70 | 2020-08-14 20:32:02 |
| 13.02 | 20.84 | 69 | 2020-08-14 20:33:01 |
| 13 | 20.83 | 68 | 2020-08-14 20:34:02 |
| 13.01 | 20.83 | 69 | 2020-08-14 20:35:02 |
| 12.99 | 20.79 | 69 | 2020-08-14 20:36:01 |
| 12.98 | 20.82 | 68 | 2020-08-14 20:37:02 |
| 12.98 | 20.77 | 68 | 2020-08-14 20:38:01 |
| 12.99 | 20.79 | 68 | 2020-08-14 20:39:02 |
| 12.97 | 20.78 | 67 | 2020-08-14 20:40:01 |
| 12.99 | 20.72 | 67 | 2020-08-14 20:42:01 |
| 12.95 | 20.71 | 67 | 2020-08-14 20:44:01 |
| 12.95 | 20.69 | 67 | 2020-08-14 20:45:02 |
| 12.95 | 20.68 | 67 | 2020-08-14 20:46:02 |
| 12.92 | 20.66 | 66 | 2020-08-14 20:48:02 |
| 12.92 | 20.63 | 66 | 2020-08-14 20:49:01 |
| 12.94 | 20.59 | 66 | 2020-08-14 20:50:02 |
| 12.94 | 20.59 | 66 | 2020-08-14 20:51:02 |
| 12.91 | 20.57 | 65 | 2020-08-14 20:52:01 |
| 12.91 | 20.52 | 65 | 2020-08-14 20:53:02 |
| 12.91 | 20.48 | 65 | 2020-08-14 20:54:02 |
| 12.91 | 20.49 | 65 | 2020-08-14 20:55:01 |
| 12.91 | 20.47 | 65 | 2020-08-14 20:57:01 |
| 12.91 | 20.45 | 65 | 2020-08-14 20:59:02 |
| 12.91 | 20.42 | 65 | 2020-08-14 21:00:01 |
| 12.91 | 20.41 | 65 | 2020-08-14 21:01:02 |
| 12.91 | 20.4 | 65 | 2020-08-14 21:02:01 |
| 12.91 | 20.37 | 65 | 2020-08-14 21:03:02 |
| 12.91 | 20.37 | 65 | 2020-08-14 21:04:02 |
| 12.9 | 20.35 | 65 | 2020-08-14 21:05:01 |
| 12.9 | 20.34 | 65 | 2020-08-14 21:06:02 |
| 12.88 | 20.34 | 64 | 2020-08-14 21:07:02 |
| 12.88 | 20.31 | 64 | 2020-08-14 21:08:01 |
| 12.88 | 20.31 | 64 | 2020-08-14 21:09:02 |
| 12.88 | 20.28 | 64 | 2020-08-14 21:10:02 |
| 12.88 | 20.25 | 64 | 2020-08-14 21:11:01 |
| 12.88 | 20.25 | 64 | 2020-08-14 21:12:02 |
| 12.88 | 20.24 | 64 | 2020-08-14 21:13:01 |
| 12.88 | 20.24 | 64 | 2020-08-14 21:14:02 |
| 12.88 | 20.22 | 64 | 2020-08-14 21:15:02 |
| 12.88 | 20.2 | 64 | 2020-08-14 21:16:01 |
| 12.88 | 20.19 | 64 | 2020-08-14 21:18:02 |
| 12.88 | 20.15 | 64 | 2020-08-14 21:19:01 |
| 12.88 | 20.15 | 64 | 2020-08-14 21:20:02 |
| 12.88 | 20.12 | 64 | 2020-08-14 21:21:01 |
+---------+-------+------+---------------------+
 
Everything's fine based on those figures. Your AGM's fully charged resting voltage will be around 12.6 odd volts. What you are seeing is the slow drop from the float charge voltage (13.8V probably) down to the resting voltage. In terms of SOC resting voltage of 12.88 is 100% charged.

If you are relying on the controller's display of SOC that may rely on the unit measuring current in / out of the battery and charger's load output terminals, or one of a few other ways. You can ignore it really unless you have taken the time to set things up to allow the SCC to make sense of what the load side is up to.
 
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