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There are several different voltage vs state of charge charts on the web today, The colorful chart is
from the 12v side of life and is designed to be used when monitoring a battery under load (more useful
to the average RVer). The boring one is from the Trojan web site manual. It's your choice as to which
one is the most accurate.
For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 6 hrs,
preferably 24. NOTE:Correct the readings to 80° F: (Add .028 per cell for every 10°
above 80° F) (Subtract .028 per cell for every 10° below 80° F.)
Trojan Manual
Percentage
of charge | Specific Gravity
Corrected to 80°F | 6V | 12V | 24V | 36V | 48V |
| 100% | 1.277 | 6.37 | 12.73 | 25.46 | 38.20 | 50.93 |
| 90% | 1.258 | 6.31 | 12.62 | 25.24 | 37.85 | 50.47 |
| 80% | 1.238 | 6.25 | 12.50 | 25.00 | 37.49 | 49.99 |
| 70% | 1.217 | 6.19 | 12.37 | 24.74 | 37.12 | 49.49 |
| 60% | 1.195 | 6.12 | 12.24 | 24.48 | 36.72 | 48.96 |
| 50% | 1.172 | 6.05 | 12.10 | 24.20 | 36.31 | 48.41 |
| 40% | 1.148 | 5.98 | 11.96 | 23.92 | 35.87 | 47.83 |
| 30% | 1.124 | 5.91 | 11.81 | 23.63 | 35.44 | 47.26 |
| 20% | 1.098 | 5.83 | 11.66 | 23.32 | 34.97 | 46.63 |
| 10% | 1.073 | 5.75 | 11.51 | 23.02 | 34.52 | 46.03 |
The 12v Side of Life
| Voltage |
State of Charge |
| 12.6+ |
100% |
| 12.50 |
90% |
| 12.42 |
80% |
| 12.32 |
70% |
| 12.20 |
60% |
| 12.06 |
50% |
| 11.90 |
40% |
| 11.75 |
30% |
| 11.58 |
20% |
| 11.31 |
10% |
| 10.50 |
0% |
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