I've recently added two extra ML33RTA 3.3kWh Growatt batteries to my setup, but since they've been in storage for a year, they show a "low voltage" error when connected. The manual states that they need to be "charged after storage" to a specific voltage of 55V at 16A for proper operation. However, when I connect them, my system just faults and shuts off instead of recharging from the grid like I expected. Can anyone provide some guidance on how to handle this situation?
3 Answers
Before connecting the new batteries, ensure they’re charged to match the voltage of your existing ones. If the new batteries are significantly lower, they can drain the charged ones quickly. Using a compatible 48V LFP charger is a great way to get them up to speed. Take your time to make sure the voltages align, or it can get messy!
You’ll want to use a lab power supply that can deliver 55V at 16A to charge the batteries manually. This is crucial since new batteries should match the voltage of your existing ones before connecting them to avoid a current surge. Without that balance, you might run into serious issues. Just make sure your power supply meets these requirements!
What do you mean by a "lab power supply"? Is that something I can find easily?
Make sure your existing batteries aren't charging while you’re trying to add the new ones. If all the batteries are within 20-80% charge, they should be close in voltage, preventing huge current spikes. Depending on your BMS setup, it might help limit the inrush current on connection. Just be careful with how you connect them. Let the batteries rest after charging before syncing them up!
But Growatt has BMS built-in; does that not help with the initial inrush?
Any recommendations for a good value 48V charger? I only need it for this one-time use.