Thursday, September 28, 2023

Lithium Battery Conversion

Our Lead-acid batteries were pretty anemic from the day we got them.  After 2 years of sitting uncharged during Covid, they were essentially scrap.  The plan had always been to install Lithium batteries on the next replacement cycle, which is now. 

In the beginning, Lithium seemed buggy and I didn't want to be an early adopter of a completely new technology and be stuck without electricity in far remote locations.  

There always seems to be a new and better technology just around the corner but how long do you wait?  LiFePO4 batteries have been in use for 20 years.  With all the advances and a huge amount of data from installed units, I felt the time had come to take the plunge.     

Prices have come down so much that the batteries themselves are now less expensive than Lead.  An expensive part of the conversion is the new infrastructure needed to manage the batteries.  This includes new wiring, Battery Management, Displays, and Charging.  The initial investment in infrastructure will always be of use in any future battery installation on the boat.

When starting this project, I was warned about how much misinformation was floating around the internet.  There sure was, and still is.  My best go-to resource was the Nordkyn Engineering series of articles.  Soggy Paws has also done a nice how-to with top notch information.

There are numerous advantages to Lithium over Lead-acid batteries and that is uncontroversial so I will let you search for things like weight, capacity, ampacity, and longevity on your own.

A big question that always comes up is "what about fires". 

Lithium batteries have a history of fires but those batteries, like the ones in cellphones and e-bikes, are Lithium Ion, not Lithium Iron.  LiFePO4 batteries and related chemistries have an extremely good safety record if installed and maintained correctly.  

It is important to understand that a good Lithium system is just just Plug-n-Play.  However, there are many bad Plug-n-Play installations out there that are giving Lithium a bad reputation.

Below is a dramatic video showing Thermal Runaway of a GBS 12V 240Ah bank that was initially managed with an Orion BMS.  This event happened one night back in March just in our boatyard in Malaysia.  Fortunately they got the battery off the boat before any damage was done.

In the video, there is only one cell that went into Thermal Runaway.  This was from a charging overvoltage, an electrical issue.   However, it would have spread thermally to the other three cells if the bank had not been separated.  

A Lithium Battery fire is essentially a chemical fire that requires no oxygen to burn and therefore can not be smothered.  Normal fire extinguishers won't work since they attempt to remove oxygen from the combustion and that's not what's going on here.  I think the best way to deal with a fire like this is to throw it overboard to get it cooled down.

The design of this system was solid but the owner really didn't understand the limitations of Battery Management and Cell Balancing.  He treated it like a regular battery and tried to charge it with a car charger.  That did not turn out well.

I have helped quite a few cruisers with their Lithium installations along with getting tours of existing systems.  I tried to take the best of everything when doing my design.  The next group of posts will hopefully put the practical and theory together for those following the more challenging path of a Lithium Battery conversion.