Yes, I know, this has been thrashed more than the Roman slaves. But, as with everything, in time, things change, and rather than resuscitate a 200 year old thread that is probably way out of date, I thought it better to start a new one as I know I am not the only one on these forums who struggles to understand the ins and outs of the electrical system on our vans. I know there are several people here who DO understand this subject, and as such, do not mind passing on their knowledge, which we all thank you for. So enough of the apologies, and I do apologise for the length of this post (please bear with me) here is the dilemma:
In my motorhome I have 2 95ah agm leisure batteries. I have a 235w Vechline solar panel with a Victron MPPT 100/20 48v controller. An NE325 40A dc-dc and an NE287 17A charger in the system. I now want to change the batteries to lithium so I can use my appliances more freely without worrying about running out of 12v power. The appliances I use are: Bergstrom open air air conditioner, rated at 1.200w, an air fryer rated at 1.400w and an expresso coffee maker rated at 1.340 - 1.600w. I normally only stay off grid for 4 days max and usually there is enough sunshine to recuperate the batteries in 3 hours. However, I am going to drive to Northern Ireland from Cádiz in March and I presume there might not be too much sun to achieve this and albeit I will not be using the air conditioning, I still want to be sure to have enough power on stop overs. So what capacity batteries would I need? and will the 235w solar panel be enough?
I sent this to ChatGpt and this is the answer. Do you experts agree with this?
462+400+300+200=1,362Wh (rounded to 1.4 kWh).
To sustain 4 days without solar:
1.4kWh/day×4days=5.6kWh.
For lithium battery capacity:
5,600 Wh0.9≈6,200 Wh\frac{5,600 \, \text{Wh}}{0.9} \approx 6,200 \, \text{Wh}0.95,600Wh≈6,200Wh (6.2kWh, or ~520Ah @ 12V).
480 W×2 hours=960 Wh480 \, \text{W} \times 2 \, \text{hours} = 960 \, \text{Wh}480W×2hours=960Wh.
Thank you for your patience guys 'n girls.
In my motorhome I have 2 95ah agm leisure batteries. I have a 235w Vechline solar panel with a Victron MPPT 100/20 48v controller. An NE325 40A dc-dc and an NE287 17A charger in the system. I now want to change the batteries to lithium so I can use my appliances more freely without worrying about running out of 12v power. The appliances I use are: Bergstrom open air air conditioner, rated at 1.200w, an air fryer rated at 1.400w and an expresso coffee maker rated at 1.340 - 1.600w. I normally only stay off grid for 4 days max and usually there is enough sunshine to recuperate the batteries in 3 hours. However, I am going to drive to Northern Ireland from Cádiz in March and I presume there might not be too much sun to achieve this and albeit I will not be using the air conditioning, I still want to be sure to have enough power on stop overs. So what capacity batteries would I need? and will the 235w solar panel be enough?
I sent this to ChatGpt and this is the answer. Do you experts agree with this?
Energy Consumption:
1. Air Fryer
- Estimated daily usage: ~20 minutes (0.33 hours).
- Daily consumption:
1,400W×0.33hours=462Wh.
2. Espresso Coffee Maker
- Estimated daily usage: ~15 minutes (0.25 hours).
- Daily consumption:
1,600W×0.25hours=400Wh.
3. Lighting, Electronics, and General 12V Use
- Typical daily consumption: ~300Wh.
4. Heating (if needed in March)
- If you use a small 12V heater or fan for ~2 hours at 100W:
100W×2hours=200Wh.
462+400+300+200=1,362Wh (rounded to 1.4 kWh).
Battery Sizing:
Lithium batteries can safely discharge ~90% of their capacity.To sustain 4 days without solar:
1.4kWh/day×4days=5.6kWh.
For lithium battery capacity:
5,600 Wh0.9≈6,200 Wh\frac{5,600 \, \text{Wh}}{0.9} \approx 6,200 \, \text{Wh}0.95,600Wh≈6,200Wh (6.2kWh, or ~520Ah @ 12V).
Recommendation
- A 6kWh (500Ah @ 12V)lithium battery bank is ideal.
- This would give you enough buffer for cloudy weather or higher-than-expected usage.
Solar Panel Performance
Your 235W panel can generate ~1.2 kWh/day under good sunlight conditions (assuming 5 effective sun hours). In March, across northern Europe, sun hours drop to ~2-3 hours/day, yielding ~500-700Wh/day.- Conclusion: The solar panel alone is insufficient for your daily usage in March. It can supplement charging but will not cover everything.
Alternator Charging
Your NE325 40A DC-DC charger will deliver ~480W (40A × 12V) to the batteries when driving. In 2 hours of driving:480 W×2 hours=960 Wh480 \, \text{W} \times 2 \, \text{hours} = 960 \, \text{Wh}480W×2hours=960Wh.
- If you drive every day or every other day, the alternator can recharge a significant portion of your daily consumption.
Final Recommendations
- Battery Capacity:
- Install 500Ah of lithium batteries (e.g., two 12V 250Ah batteries in parallel).
- Ensure your system includes a lithium-compatible charger and DC-DC converter settings.
- Solar Panel:
- Your current 235W panel is fine for summer or sunny days but may struggle in March. Consider adding a second panel to increase capacity to ~400-500W.
- Alternator Charging:
- Leverage the NE325 for top-ups during driving days. Ensure it’s configured correctly for lithium batteries.
- Battery Monitoring:
- Use a Victron SmartShunt or similar monitor to keep track of battery state-of-charge.
Thank you for your patience guys 'n girls.
How did you cope? Anyway, throw in 2 x 280Ah or 2 x 300Ah as you may have the room in your AC. I have doubts about the lithium profile in the NE charger (I think you could get away with the GEL profile).
