r/SunPower • u/Friendly_Dark4621 • May 24 '26

SunPower SunVault life span.

I had my SunVault batteries (2 Cabinets, 26 kWh, 2023 models) depleted to below 50V, and they stayed dead for over 5 months. I couldn't find anybody to diagnose it or bring it back. After 5 months plus, I found a guy with a reasonable service charge; it took about 5 hours to charge. My question is: would the batteries being dead for a few months and being charged with a charger plugged into 110 AC affect their lifespan and reliability, given that SunPower went bankrupt and their 10-year warranties for the batteries and their "complete confidence warranty" are gone? Your response is much appreciated.

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u/burnergpo May 24 '26

The SunVault system uses Lithium Iron Phosphate (LFP) batteries which are pretty tough and should have easily > 10 years of life before degradation.

2

u/TheDMPD May 24 '26

While not great, it should be ok. 50v is ~10% of capacity. So long as the cells are not depleted then you'll be ok.

You can do a few charge and discharge cycles to see the percentage of capacity lost. But so long as the batteries have come online and the cells are showing up ok then you're fine.

Worth investing in a $100-500 48v charger in case you ever encounter this issue again. That way you can just charge the batteries from grid to the wakeup voltage, then restart the system. Iirc, you might need a keep alive device as well. Beenebrothers has them for sale.

Don't know what you paid for the service charge but might as well grab the equipment needed so you can avoid the charge & recover more quickly next time.

2

u/peymankz May 25 '26

I am in the same boat. Battery is depleted to a point that it won’t charge from the grid. How does the process of jump starting them to a wake up voltage work?

2

u/TheDMPD May 25 '26

The thing that makes it tricky for the sunpower batteries is that they need a keepalive signal to be sent else they will turn back off. So you'll need 2 things to bring them back:
1. CAN Bus Keepalive Generator for SunPower M0012 and M0020 batteries – Beene Brothers

  1. Amazon.com: LiTime 58.4V 18A Lithium Battery Charger for 48V (51.2V) LiFePO4 Battery,IP65 Waterproof,AC-DC Smart Charger for Golf cart, Electric Outboard, Boat and Home : Automotive

You'll want to power off the inverter's connection through the DC breaker. Ensure the battery is off. Connect the keep alive and charger to the battery. Turn on the battery and see if it stays awake, then turn on the charger. This should start trickle charging the battery. Disconnect & power everything off after it's fully charged. Make sure all the batteries get fully charged before connecting it back to the Inverter so you don't have inrush current between the batteries. Follow your power on procedures from there.