Our Zenith 750 STOL is stored outside all winter (in Anchorage), and to our surprise we discovered one of our EarthX 680c batteries had been left on.  After bringing the battery home, and letting it warm up overnight, the battery was 7.3V. That’s a very deep discharge for any battery, and we expected it to be shot.

I spoke with Kathy, at EarthX, to see if she would drop ship us a new battery? She would of course, but recommended we first see if it is salvageable by using our Optimate lithium charger. This charger has a diagnosis mode that will also indicate if the battery is savable.  After around 12 hours of the Optimate doing its thing, we let the battery rest for two hours before checking its voltage. Voltage was 13.78V. I checked voltage again 24 hours later and it is 13.74V.

Kathy suggests we check voltage again in another 24 hours, but it's looking like a good battery.  She also shared that the batteries useful life has likely decreased, which we expected. Time will tell.

EarthX provides a great product and service.

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Doesn't that battery have the onboard Battery Management System?  If so, sounds like it protected the battery - as I understand it, it cuts off the discharging/decreasing voltage before it can damage the battery, allowing it to be rescued by the Optimate charger.  Good to hear of another positive customer service report - that's always been my experience!  :>)



Yes, it has a built-in BMS that disconnects the battery, and it worked.  The deeper discharge way below the BMS disconnect is from just sitting for over several months in an already discharged condition.  We periodically checked the tie-downs, but had no reason to look inside the aircraft.  

By the way, the other battery still had 13.4V.

I have also inadvertently left the battery on for an extended period and it recovered perfectly after charging. I have been very pleased with my 2 year old EarthX 680C batteries.

Glenn Davis


Earthx AND Kathy rock. You can always get a direct and quick answer from them on their batteries. I had a lot of questions and concerns before I put this in my plane and they were great about responding. 

Kathy has single handedly won over the VERY pick Vans RV crowd. There are some seriously knowledgeable people in that large group and she responds to every post there on Earthx.  

Add me to the list of EarthX owners who’ve left the battery on inadvertently but the BMS shut it down at around 11.8 volts, and with the proper charger it came right back and has been performing solidly ever since. I’m very satisfied with this battery, love the size and weight advantages and now the BMS.

I just checked the voltage again and it's resting at 13.7 volts.  We'll put the batteries back in the aircraft at the earliest opportunity, and if this battery fails prematurely, I will revisit this site and post an update.   For now, I'm very impressed the battery has seemingly recovered after being so deeply discharged.

Thanks for posting actual field experience, especially from AK. I' have the EarthX also in my Rotax powered 750, and it's reassuring to hear experiences such as yours. I've left mine on also, and it came back and works fine.

Thanks again, 


Your welcome

Time to give an update on that previously discharged EarthX Battery.  I'm happy to report it has performed flawlessly all summer, with no noticeable difference to the other battery.  


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