My battery is dead or near zero volts, how do I recharge it?

The ETX-Series of batteries have over discharge protection and is designed to prevent a continuous active drain on the battery to the point of damaging the battery, such as leaving your key in the on position, master switch on your aircraft, or parasitic draw as examples. If your battery is reading 0V, or near 0V, then this protection might be activated. To determine the actual voltage of the battery, remove the negative battery cable and measure the voltage at the terminals with a voltmeter. If less than 8V, it will not accept a charge. Once a lithium battery is approximately 8V, it can be permanently damaged and the EarthX BMS is designed to not allow the recharging of the battery as this is no longer safe to do and can be dangerous and cause cell rupture. Never force a charge into the battery. This is not a battery defect, nor a failed battery, but instead the protection working as it is designed. The rate of discharge depends on how many amp hours the battery has (less Ah = faster discharge) and the ambient temperature (warmer = faster discharge). When the EarthX battery is about 95% drained, the BMS over discharge protection will disconnect the battery from the active drain so that you do not continue to discharge the battery to the point of damaging it. You know this has happened when you put a voltmeter on the battery installed in the vehicle and it reads close to 0V. We allow this much discharge of the battery to provide you the most energy possible if the drain is intentional, ie: your alternator fails in flight, and you are powering your electronics with the battery. The battery will continue to drain, at a much slower rate, with time as this is impossible to stop batteries from self-discharging. Even “brand new” batteries left in a box will drain and if not recharged and maintained, will be permanently damaged. It is very important to recharge the battery immediately if it has been drained. The longer the battery remains discharged will shorten the overall life span and increases the chance of permanent damage. Depending on the amp hour of the battery and the environmental temperature will dictate how much time can pass before it is permanently damaged. Example, the ETX12A is a 4Ah battery and should be recharged within a week whereas the ETX900 is a 15.6Ah battery and should be recharged within a month of finding it in this state.

How do I know when it is time to replace my (LFP) lithium battery?

All battery types lose power and capacity as they age. The rate of when this happens depends on the maintenance of the battery and how it has been used (or abused). If you notice your battery just doesn’t have the same “umph” as it used to, it might be time to replace it. In the cold this issue is more prominent. If you notice the battery is “swollen.” As the battery ages, gases can build up inside the battery and make the battery look bulging or swollen. The gases are not dangerous or have any safety issue, but the pressure can puff the case. If the battery is left in a discharged state and then very quickly charged, the cells can puff causing the case to look bulging. The battery will not hold a voltage above 13.28V for the 12V vehicle applications or 26.56V for 24V vehicle applications. The fault light is solid or flashing on the battery models that have the LED alert and is consistently on for days.

My LED light is flashing on my ETX680C/680, ETX900, or ETX1200, what does that mean?

Most of the time, it means you need to charge the battery as it is at a low charge level but it could mean several things. First thing you need to do it put a voltmeter on the battery, if the voltage is less than 13.28V, the LED light will flash to let you know to charge the battery. If the voltage is above 13.28V and flashing, then you could have a weak cell /a cell out of balance/or defective cell and you need to contact EarthX for a warranty coverage if it is less than 2 years old. The LED will also flash if the voltage is too high, above 14.6V. If the light is solid and remains on for more than 10 minutes, then it is an indication of a BMS electronics problem and contact EarthX. LED Light Voltage Possible Cause Recommended Action Slow Flashing (5s on/5s off) Less than 12.8V Battery over-discharged (due to faulty charging system) Charge battery. Once charged, the light will stop flashing. Slow Flashing (5s on/5s off) Less than 13.2V Weak or failing cell Charge battery. If voltage drops below 13.2V within a few days, discontinue use. Slow Flashing (5s on/5s off) (> 1 hour time period) 13.2V-14.6V Weak or failing cell Discontinue use. If in flight, this is not an immediate issue unless it is in conjunction with a charging system failure. Slow Flashing (5s on/5s off) Greater than 15.2V Over-charging (due to faulty charging system) If in flight, shutoff charging system immediately. Aircraft over-voltage protection is required if alternator charging system is greater than 20 amps (i.e. over voltage crowbar circuit) Slow Flashing (5s on/5s off) (< 30 min. time period) 13.2V – 14.6V Cell to cell charge levels are not balanced May come on briefly during periods of high current charging until the cells are automatically balanced. Try charging with a plugin charger, like an Optimate Lithium charger. Solid Light Any voltage BMS electronic issue Discontinue use. If in flight, this is not an immediate issue unless it is in conjunction with a charging system failure. Solid Light that turns off after 3 minutes Any voltage Short Circuit protection was activated Nothing needs to be done. Short Flashing (2s on/2s off) Any voltage High battery temperature (> 65°C / 150°F) Let battery cool down prior to cranking or charging.

I just installed my EarthX battery in my aircraft and started the engine and my charging amps was really high, is this normal?

Yes, this is normal. A lithium battery can and will accept a much higher charging current than an equal size lead acid battery. If your battery is not fully charged, your alternator can potentially output a current equal to or slightly above the alternator’s rating for a few minutes to top the battery off. Your fuse, breaker, or current limiting device should be sized approximately 20% above the alternator rating. Example, if you have a 40 amp alternator, use a fuse, breaker, current limiter set to 48 amps (or 50 amps).

What is the shelf life or life span of a battery?

All batteries have a life span, even if left in the box and never used. Time is a factor even if properly cared for, eventually, all batteries die. An EarthX battery is rated for up to 6 years if properly maintained, which means it is not left in a discharged state (below 13.28V); used in a properly functioning charging system; used with a proper charger; not shorted; and proper temperature ratings have been followed. All batteries will self discharge and depending on the amp hour of the battery, and its temperature it is stored in, the level of discharge and amount of time are variable. Always keep your lithium battery above 13.28V for longest life.

What is the difference between PCA and CCA?

Unlike Cold Cranking Ampere (CCA), the Pulse Cranking Ampere (PCA) rating does not have an “official” definition by the automotive industry. CCA tests are done at 0 deg F with a 30 second discharge time which is unrealistic for most motorsport vehicles. PCA is a measure of battery discharge amps for <10 seconds at 77 deg F (25 deg C). Our manual shows the CCA and PCA rating of each battery. The CCA rating is most important for snowmobiles due to the colder temperatures.

Can I hook an EarthX battery in parallel or series with a lead acid battery?

No, the voltages are not the same and you will over charge the lead acid battery and drain the lithium.

What maintenance is required?

Lithium batteries require no maintenance such as adding liquid, worrying about freezing in subzero temperature, or the heat of summer damaging them. Just be sure the terminal connections are tight and free of corrosion. If you have a vehicle that has a drain even if the key is off, (Harley’s definitely do) then you will need to charge them every 1-2 months of inactivity (depending on how much of a draw there is determines the length of time it can sit) by putting a charger until it shows fully charged. If at any point your battery is less than 13.28V, it is in a discharged state and needs to be charged. Any battery left in a discharged state can and will be damaged or life shortened.

The battery does not seem to charge or hold a charge, why?

If a battery does not seem to charge or perform as well as it once did, it may be for one or more of the following issues: There may be a problem with the charging system. While the charging system is in operation, it will begin putting out approximately 13.8 -14.6 volts. The vehicle electrical system may have a short circuit or current drain The terminals on the battery are not properly tightened There may be a problem with the battery itself so if you have verified that it is not a parasitic drain, and the battery is losing power within 1-7 days, then contact EarthX. Do not continue to attempt to charge or use a battery that will not hold a charge as it might indicated cell failure and continued use can cause cell rupture, smoke and even fire.

Can the battery be installed in any position?

Yes, lithium battery can be installed in any position for they are a dry cell technology.

How do I know if my battery charger is working?

The new fully automatic chargers on the market today need to be hooked up to a battery before they will output any voltage. This is primarily a safety feature that prevents spark when hooked up, and protects the charger against reverse polarity hookup. Some chargers need to see as much as 9V volts before they recognize that they are attached to a battery. Once the charger is hooked up, it should output 13.9-14.6 volts. If your charger does not do this, you may want to contact the manufacturer for further troubleshooting tips.

Is it safe to hook up the battery to a charger and walk away?

No. As with any battery being charged it is best not to do this in the event of a faulty charger. Follow these safety tip for charging ANY type of battery. Never leave the battery or the vehicle unattended when recharging it. When charging a battery, place it on a non-flammable, and remove any flammable items nearby. Unplug chargers from the battery or vehicle always after the battery reaches full charge. Disconnect chargers when not in use.

How often should I charge the battery?

Only when needed which is when the voltage reads below 13.28V. It depends on the battery model (the larger amp hour batteries will need less topping off than say the scooter battery) but if not in use or left in a vehicle, make sure you check the voltage and charge at least once a year. Due to lithium batteries extremely low self-discharge rate, less than 50% of its charge is lost over a 6 month period, so you may not have to charge your battery before the season starts! If the battery is 13.28V or higher, then all is good. If it is less than this, you need to charge it before engine start to ensure a long battery life.

Are lithium batteries safe?

Since inception in 2009, EarthX has designed their lithium batteries with a micro-processor-controlled battery management system (BMS) to provide safety and performance features for your battery. EarthX is not new to providing lithium iron phosphate batteries. Over the past 13 years, has become the most trusted and used lithium battery in the experimental aircraft market and by working closely with OEM’s and engine manufacturers a like, this BMS has been developed to be one of the most reliable in the industry. EarthX is not only the exclusive provider for the Indy Race Cars, but EarthX is also the first company in the world and in history to have an FAA TSO certified aircraft battery as a testament to the safety and quality of the batteries. Features of the BMS protection: Cell balancing Low voltage protection High voltage protection Excessive Cranking Protection (Heat) Short circuit protection In the Hundred series, an alert LED fault light to communicate an issue on battery itself or can be remotely monitored with a 12V LED In the Hundred series, the BMS board is redundant so there is no single point failure Battery design safety features: Proprietary battery case design with recessed terminals to protect from short circuiting Clam shell design with terminals down the center so polarity (installation) is never an issue Flame retardant plastic housing The state of the art ceramic cell separators to reduce the risk of thermal runaway by 400% over standard lithium cell separators. Performance design features: The widest operating temperature range available A rated cells that must meet stringent testing requirements True industry standards testing specifications

How long should I wait in between failed start attempts?

Cranking should be limited to 10 seconds within any 1 minute period. Most starter manufacturers also recommended less than 10 seconds of cranking in any 1 minute period.

How much do I tighten the screws for installation?

Tighten the screws to 35 in-lbs. If you don't have a torque wrench then use a screwdriver to tighten firmly (one handed). If you over torque the screws, you will damage the BMS board or loosen the nut.

How long will my battery last?

4-6 years is the average lifespan, however they can last longer depending on how they have been maintained, the quality of the charging system and the enviroment used in.

Why does my battery look puffy or swollen?

Many things can cause a puffy or swollen looking battery, which is caused by the buildup of gases inside the battery. This can be from age as gas will build up over time; being exposed to extreme temperatures; deeply discharging or overcharging of the battery. This is a good indicator that it is time for a new battery.

Will my aircraft lithium battery catch fire?

We understand the fear of a fire in an aircraft is real and justified. We also understand people fear that a lithium battery will spontaneously self-combust with no warning and reason and catch everything near it on fire too. We want to address this fear. The EarthX batteries are LFP chemistry, or lithium iron phosphate, the most abuse tolerant and requires a lot of energy to force them into thermal runaway. The term thermal runaway can mean different things and for a LFP battery, it does not mean a 3-foot-tall explosion of flames, it means it will produce a lot of smoke for about 10 minutes. (It should be noted the type of chemistry that does cause a large fire ball is the most used cell in the world, a Lithium Cobalt cell. This is found in your cell phone, your tablet, your laptop, etc. On a commercial flight, if you are traveling on a 737 with 204 person capacity, it would be typical to have around 300 of these batteries in the cabin with you as a reference point). To cause a thermal runaway with the EarthX battery, many things in your aircraft, and you as a pilot, would have failed. First, your regulator would have to fail. Then your over voltage protection on your aircraft would have to fail. Then you as a pilot would have to fail and not turn your charging system off (alternator off) as you see the voltage and amps climb, destroying all your electronics on your panel and popping fuses everywhere in the process. If you did nothing but continued to fly, and if the batteries protection failed too or you exceeded the protection limits (over 100V), it takes about 7 minutes of this type of runaway energy to cause a thermal runaway with the battery. The FAA TSO certified approved battery, the ETX900-TSO,and the ETX900-VNT, are in a fireproof containment system (internally) and is a sealed battery that is vented overboard, so even in this catastrophic state, the smoke is pushed overboard and it is not a battery safety issue and it does not cause anything near it to heat or catch on fire either. As far as the fear of spontaneous self-combustion, the battery must be part of a catalyst situation for it to go into thermal runaway. It will not simply “combust” with no reactor. The batteries have short circuit protection and a battery management system to prevent the use of the battery if it detects a fault. The Hundred series for aircraft also has a fault monitoring that would alert you if something was outside of normal with an LED light that will illuminate.

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Home / Shop Parts ... / ETX900-24

P/N: ETX900-24

Name: BATTERY SYSTEM, 28V, Experimental
Brand: EarthX Batteries
SKU: ETX900-24
Price: 899.0 USD
Availability: BackOrder

BATTERY SYSTEM, 28V, Experimental

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Condition	New
Manufacturer	EarthX Batteries
Dimensions	L: 6.5 x W: 5 x H: 7 in
Weight	8.9 lbs
Unit of Measure	Each
Retail Price	$1,123.75
Your Price	$899.00 Not Eligible for Free Shipping
Stock Status	Expected ship date is 09-14-2026.

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Experimental EarthX Batteries

Note - No hazmat fee charge, unless quantity results in shipment exceeding 300 Watt hrs. Fee for international shipments may apply.

ETX900-24 BATTERY SYSTEM
Voltage	26.4
Weight	8.9lbs (4.0kg)
Cold Crank Amps (CCA)	400
Peak Cranking Amps (PCA)	840
Amp Hour	15.6
Chemistry	Lithium Iron Phosphate (LiFePO4)
Case Size	U
Dimensions (LxWxH)	6.5" x 5.1" x 6.6"
1hr 1C rate	11.7Ah
Includes:	1x ETX900-24, 2x6mm screws, with washers and lock washers

**DOES NOT include LED fault light

Designed for piston engines up to 550ci . Max alternator output is 80 amps at 29V or 150 amps at 28.2V. If used for ONE turbine engine, you must have 2 batteries connected in parallel. Contact us prior to buying to verify the proper batteries needed for your TURBINE application.

This battery is fully protected by an integrated battery management system (BMS) that protects the cell’s from over discharge, over charge, short circuit, temperature, plus cell balancing to ensure charge levels are equal. Additionally, the ETX-Hundred Series aircraft batteries have redundant electronic circuits and battery fault indication. The fault indicator can be connected into your EFIS or wired to a 24volt LED light on your control panel to alert you to the state of charge and state of health of the battery. (Please see manual for details)

EarthX Batteries use Lithium Iron Phosphate chemistry to deliver powerful starting energy. This chemistry provides the highest, most robust performance and safest power on the market. All EarthX Batteries come standard with a BMS (battery management system) for performance, safety, and longevity.

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