Hey everyone, I'm relatively new to this solar power setup and have a few questions about using my 2kW, 24V hybrid inverter. I understand that lead acid batteries can degrade faster if they're used beyond the C10 discharge rate. For my setup, that means pulling 84 amps when I'm running the inverter at full load (2000W / 24V). I have two 150Ah lead acid batteries in series, which means they're providing the current for that load. Since the C10 discharge rate for these batteries would be 15A, I'm worried about the implications of drawing so much power continuously.
Additionally, I believe the inverter charges the batteries while also using battery power to produce AC output, which seems like it could lead to some serious battery wear due to the high current draw. Am I right about this? Should I be worried about the batteries dying young if I run the inverter full tilt for long periods, say around two hours? What's the maximum safe draw from these batteries without damaging them? If my fears are accurate, what can I do to ensure these batteries last me 6-7 years? Just as a side note, I don't have access to lithium batteries in my area.
3 Answers
That’s a good question! When you’re talking about C10, just remember that you actually mean C/10, which shouldn’t be a problem for your batteries. Although your usable capacity may drop below the rated C/20 level, it's not likely to damage them right away. Just a heads up — though you can’t charge and discharge simultaneously, if your inverter is pulling 84 amps and your charge controller is pushing out 20 amps, your batteries are really discharging at 64 amps. Lead acid batteries do take a lot of current without immediately breaking down, but they’ll drop their output voltage as you push them harder. Your inverter should shut down before causing any damage! If you want longevity, you might want to consider moving to industrial batteries that can be topped up with water over time.
You’re right to be cautious! 15A from a 150Ah battery is really not much at all. Lead acid batteries can handle high currents pretty well, even sustained pulls above 1C occasionally won’t hurt them. The key factors are maintaining a state of charge above 50%, and making sure you fully recharge them whenever you can. You definitely want to minimize the time spent in low charge states since that can lead to sulfation damage over time.
Thanks for the detailed response! Can you also help me with setting the parameters of my inverter? My OEM allows me to update those settings.
You’re pulling 84A from a 150Ah bank, which is nearly at the C1 rating, meaning you could essentially run your inverter for about an hour before bringing your batteries close to depletion. If you want them to last the 6-7 years you’re hoping for, aim for a maximum daily depth of discharge of around 25% for flooded lead acid batteries. Sealed types like AGM won’t fare as well, and you might get slightly better results if you have OPzV types. So, you might want to either add more batteries for longer runtime without stressing the system, consider a smaller inverter if you don't need the heavy load, or lower your expectations on battery life if you keep pushing it like this.
Thanks for the detailed response! Can you also help me with setting the parameters of my inverter? My OEM allows me to update those settings.
Thanks for the detailed response! Can you also help me with setting the parameters of my inverter? My OEM allows me to update those settings.