One of the most common questions for campervan and motorhome owners is: how long do I actually need to drive to charge my leisure battery? The answer depends on your DC-DC charger output, battery capacity, battery chemistry, and depth of discharge. This guide provides the formulas and lookup tables you need to estimate charge times for real-world scenarios.
The Basic Formula
The simplified formula for estimating charge time is:
Charge Time (hours) = (Battery Capacity × Depth of Discharge) ÷ (Charge Current × Efficiency Factor)
Where:
- Battery Capacity — the usable capacity in Ah (e.g., 100Ah)
- Depth of Discharge (DoD) — how much charge has been used, as a decimal (e.g., 50% = 0.50)
- Charge Current — the output of your DC-DC charger in amps (e.g., 30A)
- Efficiency Factor — accounts for energy losses in the charging process
Efficiency Factors
LiFePO4 lithium batteries have an efficiency factor of 0.95-0.98 and accept full charge current until nearly full. AGM and Gel batteries are less efficient (0.80-0.85) and critically, they dramatically reduce charge acceptance above 80% state of charge. During the absorption phase, current tapers from 30A down to 2-5A over several hours. This means charging a 100Ah AGM from 50% to 80% takes about 1 hour at 30A, but 80% to 100% takes an additional 3-4 hours. Lithium batteries do not have this limitation, making them far more practical for charging while driving.
Charge Time Lookup Tables
The tables below show estimated charge times for common configurations. Times are given in hours and minutes. For lead-acid batteries, times to 80% SOC are shown separately since the final 20% takes disproportionately long.
Victron Orion-Tr Smart 12/12-30 (30A Output)
100Ah LiFePO4 Battery
| Starting SOC | Energy Needed | Time to 95% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 25Ah | 0h 42m | 0h 55m |
| 50% (50% DoD) | 50Ah | 1h 35m | 1h 48m |
| 25% (75% DoD) | 75Ah | 2h 28m | 2h 41m |
200Ah LiFePO4 Battery
| Starting SOC | Energy Needed | Time to 95% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 50Ah | 1h 25m | 1h 50m |
| 50% (50% DoD) | 100Ah | 3h 10m | 3h 35m |
| 25% (75% DoD) | 150Ah | 4h 56m | 5h 21m |
100Ah AGM Battery
| Starting SOC | Energy Needed | Time to 80% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 25Ah | 0h 12m | 3h 30m |
| 50% (50% DoD) | 50Ah | 1h 12m | 4h 30m |
| 25% (75% DoD) | 75Ah | 2h 12m | 5h 30m |
200Ah AGM Battery
| Starting SOC | Energy Needed | Time to 80% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 50Ah | 0h 24m | 4h 45m |
| 50% (50% DoD) | 100Ah | 2h 24m | 6h 45m |
| 25% (75% DoD) | 150Ah | 4h 24m | 8h 45m |
Victron Orion XS 12/12-50 (50A Output)
100Ah LiFePO4 Battery
| Starting SOC | Energy Needed | Time to 95% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 25Ah | 0h 25m | 0h 33m |
| 50% (50% DoD) | 50Ah | 0h 57m | 1h 05m |
| 25% (75% DoD) | 75Ah | 1h 29m | 1h 37m |
200Ah LiFePO4 Battery
| Starting SOC | Energy Needed | Time to 95% SOC | Time to 100% SOC |
|---|---|---|---|
| 75% (25% DoD) | 50Ah | 0h 51m | 1h 06m |
| 50% (50% DoD) | 100Ah | 1h 54m | 2h 09m |
| 25% (75% DoD) | 150Ah | 2h 57m | 3h 12m |
Real-World Driving Examples
Here are some practical examples of what you can achieve during typical drives:
Short Trip: 1 Hour Drive
| Setup | Starting SOC | Approximate SOC After 1 Hour |
|---|---|---|
| Orion-Tr Smart 30A + 100Ah LiFePO4 | 50% | 79% |
| Orion-Tr Smart 30A + 200Ah LiFePO4 | 50% | 65% |
| Orion-Tr Smart 30A + 100Ah AGM | 50% | 74% |
| Orion XS 50A + 100Ah LiFePO4 | 50% | 98% |
| Orion XS 50A + 200Ah LiFePO4 | 50% | 74% |
Medium Trip: 2 Hour Drive
| Setup | Starting SOC | Approximate SOC After 2 Hours |
|---|---|---|
| Orion-Tr Smart 30A + 100Ah LiFePO4 | 50% | 100% (complete in ~1h 48m) |
| Orion-Tr Smart 30A + 200Ah LiFePO4 | 50% | 79% |
| Orion-Tr Smart 30A + 100Ah AGM | 50% | 80% (then absorption slows dramatically) |
| Orion XS 50A + 100Ah LiFePO4 | 50% | 100% (complete in ~1h 05m) |
| Orion XS 50A + 200Ah LiFePO4 | 50% | 98% |
Long Trip: 4 Hour Drive
| Setup | Starting SOC | Approximate SOC After 4 Hours |
|---|---|---|
| Orion-Tr Smart 30A + 200Ah LiFePO4 | 25% | 84% |
| Orion-Tr Smart 30A + 200Ah AGM | 25% | 80% (then absorption phase begins) |
| Orion XS 50A + 200Ah LiFePO4 | 25% | 100% (complete in ~3h 12m) |
| Orion XS 50A + 200Ah AGM | 25% | 80% (in ~2h 40m, then slow absorption) |
Parallel Chargers for Faster Charging
If a single 30A Orion-Tr Smart is not enough, you can wire up to three units in parallel for 60A or 90A total output. This is particularly useful with large lithium battery banks of 300Ah or more. The units coordinate via VE.Smart Networking over Bluetooth to share the load evenly.
Alternatively, a single Victron Orion XS 12/12-50 delivers 50A from one unit, which is often the simpler and more cost-effective solution compared to two Orion-Tr Smart units in parallel.
Important Caveats
- Alternator capacity matters. Most modern van alternators (150A+) handle the additional 30-50A load comfortably, but check yours can cope.
- Smart alternators may limit input. See our smart alternator guide for details.
- Cable sizing affects performance. Undersized cables create voltage drop, reducing power to the charger.
- Temperature derating. In hot engine bays, real-world charge times may be 10-20% longer than the tables suggest.
- These times assume continuous driving. Stop-start traffic will extend charge times.
For help choosing between DC-DC charger options, see our Victron Orion-Tr Smart vs Sterling B2B comparison.
