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  #11  
Old 09-21-2022, 11:53 AM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
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Quote:
Originally Posted by airguy View Post
Don't depend on the paperwork with the device - test it in your installation, for the way you will use it. That's the only way to be certain.
Exactly. Well said Greg.
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  #12  
Old 09-21-2022, 01:00 PM
dmattmul dmattmul is offline
 
Join Date: Dec 2015
Location: Spring Hill, FL
Posts: 489
Default Battery Life

Always a good idea to test batteries (Especially) an electrical dependent engine. I test mine annually to insure they are at least 80% before the battery light comes on. (Also monitor voltage) So far after 3 years going strong. Just FYI you can purchase a cheap mA totalizer on Amazon. I know this is a good test for lead acid and I assume Earth X batteries but does anyone have any experience of failure mode for a EarthX battery? IE could it test out to 90% and fail a month later? By fail I mean much less than 80%. With 2 batteries I am not so worried about this but good to know.
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RV-14A QB builds (2017), Lycoming 390 Thunderbolt arrived July 2019, Garmin avionics, Vertical Power, EFII-32 Ignition and Fuel, Whirlwind 300-72, Earth-X batteries, Beringer wheels and brakes, Parts became real airplane 8/15/2020. Started RV-10 Nov 2020. Empennage arrived (Built) Working on QB kits. Garmin avionics, Vertical Power, EFII-32 Ignition and Fuel, Whirlwind 3 blade HRT 378, Earth-X batteries, Beringer wheels and brakes, real airplane hopefully early-mid 2024. Paid subscriber
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  #13  
Old 09-21-2022, 06:20 PM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 971
Default EarthX Failure modes

Quote:
Originally Posted by dmattmul View Post
I know this is a good test for lead acid and I assume Earth X batteries but does anyone have any experience of failure mode for a EarthX battery? IE could it test out to 90% and fail a month later? By fail I mean much less than 80%. With 2 batteries I am not so worried about this but good to know.
I've had a few EarthX batteries; I have replaced two of them at about the 8 year point. The indicator for me on one was that I starting to get a fault (5s on/5s off) that came in with voltage above 13.5V system voltage. It came in for a few minutes, and then went away. The second time it came in, I contacted EarthX for advice. They recommended that if the light goes out within 30 minutes, the battery is doing a balancing of cells - but this also is an indicator that the battery is aging. Their manual indicates this is a replacement criteria if the fault stays in more than 30 minutes.

On my second battery, I noticed that my Optimate charger provided a red light during a post charge test. (side topic: I highly recommend the Optimate charger. I have the TM275 and find it is excellent for maintaining Lithium batteries.).

The red test light on the charger indicated that the battery was dropping below 12.8V within 30 minutes during the post charge test, where the Optimate performs a minor discharge test, then recharges and reverts to maintaining voltage. Noting that the battery was at 8 years age and that EarthX indicates a normal service life is about 6 years, I replaced my battery on that fault.

I expect that if properly maintained, including not allowing the battery to stay in a discharged state below 13.28V, you would expect a normal life with end of life indications being similar to mine. That doesn't discount that the sucker could short circuit and fail immediately, but I would expect that is extremely rare having a Battery Management System built in. It does highlight the importance of having a discrete output from the BMS to an EFIS, or an idiot light if you prefer; this is a definite advantage over a lead-acid battery in that it is providing performance indications above simple voltage. If a lead-acid battery sulfates or experiences cell-reversal, the immediate indication is a loss of voltage with little to no warning. The normal failure mode of Lithium-Ion battery designs is the reduction in ability to raise cell voltage, driven mostly by over or under voltage conditions and high temperature charging (which is mitigated by EarthX by having a BMS that limits charging current in reference to cell temperature).

I currently have two ETX900 batteries, one is 5 years old and one is 1 year old. The 5 yo battery recently provided 92% full capacity and the 1 yo was 100% based on the annual test criteria.

Also, a discharge test can be very simple, such setting up a measured load on the ground (such as running a fuel pump, all the lights and some avionics to get a fixed load, preferably above 80% rated capacity of the battery) with a a system ammeter, or use a clamp-on meter (from Amazon no less) - and then just marking the time until voltage drops to 11V, and then doing the math (see the test in my first post) to determine the remaining capacity.

More "free" advice, is that you should set your voltage regulator at 14.2V for the ideal setpoint on lithium batteries, which is lower than the 14.4-14.6VDC common with most L-A setups. Above 14.2 will reduce the life of the battery - less than 14.2 unnecessarily limits the system capacity.
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Last edited by rongawer : 09-21-2022 at 06:29 PM.
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  #14  
Old 09-21-2022, 07:02 PM
BillL's Avatar
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by rongawer View Post
<snip>I just purchased significant quantities from all three: BYD, Samsung and Tesla. <snip>
Ron, can you tell us what chemistry these batteries are and the specified float voltage range? Per cell is good for comparison.

Are these banks being typically managed to a mid DOD range?

If there are qualifying conditions of temperature and time (re float voltage) please so state.


Thanks.
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  #15  
Old 09-21-2022, 08:58 PM
rongawer rongawer is offline
 
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Location: Brentwood, CA
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Quote:
Originally Posted by BillL View Post
Ron, can you tell us what chemistry these batteries are and the specified float voltage range? Per cell is good for comparison.

Are these banks being typically managed to a mid DOD range?

If there are qualifying conditions of temperature and time (re float voltage) please so state.


Thanks.
Bill, I'm interested in what you intend to do with information I provide - it comes across as a question from a lawyer for cross-examination rather than a quest for information. You can find most of this information with Google as well, just search on "BESS".

However, noting that my answer has little to do with a battery for an RV, I'll answer... the chemistry varies by installation and intended purpose, however the most recent one I did is by BYD and lithium-Ion chemistry. I've attached a photo of what our 600+MWh of storage looks like, just achieved COD back in March. The output voltage from the inverter bank is just over 13,000VAC, which is then stepped up to 230kV for transmission.

We don't actually monitor "per cell" as there are literally 300M+ cells in this pictured system...although they're essentially massive packs made up of 3.7V cells that look very similar to an 18650 cell you might have a for a flashlight. I haven't cut open an EarthX battery, but I suspect their internal construction is similar, albeit made of LiFePO.

There are many qualifying conditions with this Battery Energy Storage System (BESS) and it is highly instrumented with cooling, inverters, and charging systems, along with several other auxiliary controls and monitoring interfaces. This particular installation is a 100% DOD/SOC (Depth of Discharge and State of Charge) installation that is capable of daily full cycles for 20+ years, with many parameters of temperature and charge, although most of it is covered by an NDA and is not shareable on this forum.
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  #16  
Old 09-21-2022, 10:21 PM
dmattmul dmattmul is offline
 
Join Date: Dec 2015
Location: Spring Hill, FL
Posts: 489
Default Battery Life

Ron, thanks. I set both for 14.2 using the B&C regulator.
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  #17  
Old 09-25-2022, 06:53 PM
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BillL BillL is offline
 
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Location: Central IL
Posts: 6,838
Default No lawyer question, just technical.

Thanks Ron, that is 7300 cycles for full charge discharge cycles, pretty impressive that they can do that. I suppose allowances have to be made for deterioration etc.

Based on the answer provided the application cycle gives a lot of insight into how these batteries are used. My experience was for mobile machinery where consistent power availability was important whether as full electric or hybrid, and near top SOC LiFePO would fall short of absorption and near zero SOC short of discharge power. Just a characteristic of the charge/discharge curves.

I suppose if one has full backup power capability then this is not needed and full range cycles are possible. In machinery it did not make sense to have full rated power for the prime mover and the energy storage just in case.

In regards to the float voltage, this application would have little time there or could drop the voltage as needed. Huge demands on silicon to buck/boost over the full range. Not at all the situation with a starting battery in a constant voltage system.

For readers the early, Prius hybrid only operated in a DOD range of about 5% to render long cycle life with a target in the mid SOC range. Lousy for a "plug in" hybrid.
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  #18  
Old 09-25-2022, 08:33 PM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
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They've definitely come along way with lithium based battery construction. Also price per kW is on track for about 16% reduction per year over the last 10 years from an industrial perspective. How that translates to a small retail battery is that most manufacturers are able to hold market pricing in spite of significant inflation rates. Case in-point is that EarthX ETX900 costs the same $449 today that it was in July 2017.

The design criteria is 10,000 full cycles, so yes, definitely a little extra in the bank for the life of the unit. However, unlike a mobile installation that might be weight or space limited, we can additional "packs" as needed to ensure 100% nameplate capacity over unit life.
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