Do I understand correctly that the overvoltage protection of EarthX batteries works only until the voltage becomes really overly excessive? And that a crowbar OVP is required in any case, just like with any other battery?
If that's the case, what does it make an EarthX "aviation" battery any more "airworthy" than any other lithium battery from one of the major brands (for example, Shorai) with comparable Ah and CCA ratings? In many cases, you could get a "motorcycle/powersport" lithium battery with similar ratings for significantly less $ and it would even weight less than the "aviation" battery.
Thank you for the questions. No, you are not correct about the overvoltage protection on the EarthX. The over voltage protection begins at 16V and can continue to protect up to a voltage of >60V. In the EarthX manual this protection is explained in detail.
The crowbar protection is required for alternator/generators that are greater than 20 amps max (non pad mount alternators). This means that if you have a Rotax 912, 914, 915 or 582 engines, you do not need to install an additional crowbar protection as they are 18Ah max output. But if you have a Lycoming IO-360, 60 amp alternator, you do need to make sure that you have over voltage protection. This over voltage protection will also protect all the expensive electrical equipment in your plane too!
You ask, what makes the EarthX aviation battery more ?airworthy? than the common motorcycle line brands on the market, which is a great question. The EarthX aircraft batteries are tested to RTCA DO-347 and RTCA DO-160 FAA standards for lithium batteries used in aircrafts (these are the requirements for a certified battery). There is only one other lithium brand out there that test to this standard and that is True Blue. The ETX680C, ETX680, ETX900 and ETX1200 currently in production and soon the ETX900-VNT have a completely different battery management system than the motorcycle batteries EarthX builds with built in redundancy. This is explained in detail in the manual. They also have LED fault light monitoring which is a means of communications to the pilot to the state of health and state of charge of the battery. What is most important about this is the detection of a defective cell. You do not want to use a defective lithium battery. Note: this is what happened with Boeing, they had a manufacturing defect in some of the cells. If you have no issues with your charging system, but you use a defective lithium battery, you can cause a cell rupture. The difference in price from our motorcycle line to our aircraft one with the same performance spec?s is $30 more for these additional design/safety features. We did not want price to be the reason for someone to choose a motorcycle battery over the aircraft version which does costs more to build.
And for your last question, why not use a motorcycle/powersport brand like Shorai because it is cheaper? As you mentioned Shorai, we will focus on them but the same reason will hold true for many of the lithium batteries on the market too. Please read their manuals for specifics on each brand.
First, Shorai itself specifically states on their website to not use their batteries in aircraft and there is no liability or warranty coverage if you do. Second, the EarthX aircraft batteries are designed for aircraft charging systems and are tested to very high quality safety standards set forth by the FAA (RTCA DO-347, RTCA DO-160). Shorai does not do this. Third, Shorai does not offer batteries with enough capacity for aircraft. Their largest sized battery would be a significant decrease in capacity from what aircraft currently use which is a very important consideration in that if your alternator/generator has failed during flight and you are on battery power only, you don?t just pull over in a plane. Fourth, Shorai has no manual listed that has sizing, performance or design limitation for their batteries. It is not enough to match a lead acid or another lithium battery based solely on cranking amps as you also have to consider charging; you must know the maximum charge current the battery is designed to accept. We have a detailed explanation of this on the website. Fifth, Shorai has no protection built in, they have cells in a plastic case. There is no over discharge protection, no over charge protection, no heat protection, no short circuit protection and no cell balancing technology. EarthX has all of this. And lastly, Shorai has no means to alert you to a cell defect such as the LED fault light indicator that the EarthX does. The importance of this was listed previously in this post.
These are the reasons why aircraft manufacturers do not use the ?motorcycle/powersport? lithium batteries you mentioned or even some of the lithium batteries that are being marketed to the aircraft market. This is also the reasons why the experimental engine companies do not use them. They are not the same and they are cheaper for a reason.