While I completely agree that OV protection is best built into the plane's electrical system for a variety of reasons, I thought that disconnecting the battery from the bus in such a case was one of the things the BMS was supposed to do.

That muddies the water. OV protection for installed equipment is a completely separate issue, and would apply no matter the battery chemistry.

To EarthX:
Saying that a solid state battery management system can't respond quickly enough to handle a noisy charging system, and blaming the charging system, just makes no sense to me, from an engineering perspective. If the company is uninterested in making the BMS capable of handling the transients, just say so & publish the excursions that it *can* tolerate. As others have pointed out, *any* charging system can have failure modes that will likely cause similar voltage/noise excursions to the Rotax. If the BMS isn't designed to handle those excursions, then the same problems can occur with a Lyc, Cont, etc, and the battery cannot be considered a 'drop in' replacement for a lead-acid battery, as your marketing implies, even if it doesn't state it explicitly.

Please don't misunderstand the seemingly negative posts you're seeing. I for one would love to have the weight savings, and want the product to be successful. But your operational limits and many statements you've made here over the last few months don't give me a warm & fuzzy feeling that you understand your own product. Another example is your limit to charging system size. I'd love to hear a rational explanation for this, since if flies in the face of any practical application I've ever heard of. Ex: a 12v 5w lamp doesn't care if it's powered from 8 AA cells, or a farm tractor battery capable of supplying 600 cold cranking amps. It just takes what it needs & leaves the rest. Why is your BMS any different?

Charlie

Appear melted? Tell us more. The electrolyte will dissolve a plastic battery case? What is it?

There are pluses and minuses with any solution. Clearly there are some big pluses with LiFePO batteries, light weigh, lower internal resistance and maybe life span. There are minuses; high cost, cold weather use, over discharge and overcharging/voltage spikes intolerance. The BMS helps mitigate some of these disadvantages, but not all. I?m not sure technically how the BMS could protect the LiFePO cells and at the same time filter out the voltage spikes. To do that would require clamping down on the voltage spikes likely generating a lot of heat that would need to be dissipated. Where the lead battery with is weight and mass is better suited to filter and dissipate that heat. I would not want the BMS to open the connection to the cells to protect the battery allowing the voltage spikes to travel through the plane?s electrical system with no filtering effect. Not all planes have OV protection, but I do think you should have it when using a LiFePO battery for sure. I personally feel EarthX has developed a very good solution installed correctly and when used in the type of environments most of fly in.

Pylon Mount Battery- Jettisonable
 

I can see it now, Dan's RV 8 with a jettison-able pylon mounted earth X that looks like a sidewinder or some low drag area rule tube like a T-38 wing tip tank:D

Naaa. All I'll need is a VPX, an extra EFIS screen, and a battery management checklist so I'll know what to do when lights flash.

Sheesh. I have a light for battery management. Once a year I open the hellhole and shine a flashlight on the battery. Here's my checklist:

Is it still there? Yes__ No __

Ok, done for another year ;)