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Old 07-09-2018, 03:29 PM
WA85 WA85 is offline
Join Date: Apr 2010
Location: Madison, AL
Posts: 125
Default Earth X Battery Installation - A few observations

I installed an Earth X ETX 680 battery in place of my existing PC-680 on my TV-8 and here a few observations that may of help to the next person doing this.

1. The ETX 680 will fit in the Vans firewall mounted, 4 sided, PC-680 sized battery box, however it sort of bulges the sides of the battery box and it is a "press fit". You have to press the ETX680 into the center of the box for it seat all the way in...which allows for equal bulging of the box on both sides. It is a snug fit! The battery bold down bar will also work, however the terminals on the ETX 680 are centered on the battery whereas the terminals on the PC-680 are bias to one side (fwd or aft depending on which way it was mounted). You can get terminal adapters from Earth X to move the terminals to the side.

2. If you install the fault warning light, it may not come on at all during your first test runs...which is normal, no light is a good thing. Sometimes we tend to expect to see some kind of indication, but in my case, no light meant no worries. You can easily test the light by disconnecting wire lead from the battery fault wire and grounding the wire lead that goes to the fault light.

3. On start up, the first thing that got my attention was the amount of charging amps that my Skyview was showing...50 to 55 amps for about 5-10 seconds and then it dropped down quickly to 5-10 amps. This initially concerned me because that means my 60 amp current limiter is being stressed to near max on every start up. I contacted Kathy at EarthX and she point out the following - "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 alternatorís 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 50amps)."

In my case my 60 amp alternator needs to have a current limiter of approx 72 amps. The closest current limiter I can find is 80 amps, which appears to be the best solution.
So if you are putting in an Earth X battery, check before hand if your wiring and current limiter / fuse can handle the full alternator output....because the battery will pull all those amps, in may case 50-55 amps out of a 60 amp alternator.

4. The Earth X battery does have significantly more energy to the starter and it definitely cranks the engine over with gusto...I found that it starts my engine quicker, especially hot starts.

5. Overall, installation of the ETX battery is a pretty easy conversion from the PC-680. The fault light was a pain install since I had to dive under the panel of my RV-8 to run the wire. The current limiter issue is fixable by getting a higher amp item. If needed, a PC-680 can be dropped back in with little to no "un-conversion".
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Old 07-09-2018, 03:52 PM
airguy's Avatar
airguy airguy is offline
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 4,469

I commonly see charge rates in the 45 amp range after start as well with my ETX900, and lasting 30 seconds to a minute then tailing off rapidly. Recently I took my plane in for pitot/static and transponder cert, and some 430W configuration issues - all in all the master and whole panel was lit up for about 45 minutes with no ground power attached. When it was done I cranked up normally and it spun the engine quite happily - you would never know the battery was partially discharged. That time the charge rate didn't drop below 30 amps until I was well out of the traffic pattern.

I'm quite impressed with the lithium battery's ability to deliver full or near-full cranking voltage at a partial discharge, much better than lead-acid.
Greg Niehues - PPSEL, IFR, Repairman Cert.
Garden City, TX VAF 2019 dues paid
N16GN flying 380hrs and counting! Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
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Old 07-09-2018, 05:45 PM
Mich48041 Mich48041 is offline
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,764

A 60 amp ANL current limiter will conduct well over 60 amps indefinitely without blowing. See the chart on the DATASHEET.
Joe Gores
RV-12 Flying
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Old 07-09-2018, 08:15 PM
F1 Rocket F1 Rocket is offline
Join Date: May 2008
Location: Melboring, FL
Posts: 38

I recently replaced the PC925 in my Rocket with an EarthX ETX 900. Almost 22 lbs less weight and spins the 540 nicely
F1 Rocket #25
N14ZM "Dreamer"
Melboring, FL
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