Lithium batteries

[ykachuro]

I am sorry if I pour more gas onto this fire, but i had to make a couple of points to further note regarding lithium batteries (these are often obscured by the marketing fluff put out by the manufacturers)
— the lithium batteries’ amps/hr capacity rating does not reflect their actual capacity (unlike that of lead acid batteries). It is what they call the lead acid battery equivalent. The actual capacity is somewhere around 30% of the rating. So, when a lithium battery is rated at 21 amps/hr capacity, in reality it may hold only around 7 amps/hr. A battery with a built in BMS might shut itself off even before it’s full reserve capacity is used up. This is important to understand, especially if an airplane is power depended.
— there are no commonly accepted/recognized “safety standards” applicable to batteries to which EarthX battery is allegedly conforming. At least not more so than other lithium battery manufacturers. I’ve come to my own conclusion that the EarthX battery BMS makes it less safe than a battery without a built in BMS. Please read the discussion on VAF i referenced earlier and draw your own conclusions. As far as I am concerned, the main problem is that when EarthX takes itself out in case of an overwoltage event, all the energy that would’ve been absorbed by a battery has to now go somewhere else — the resulting voltage spike wil more likely kill other electrical components that may or may not be properly protected. In addition to that, once the voltage exceeds 60volts or thereabout, EarthX BMS fails and the battery becomes suseptible to this high voltage with all the reaulting consequences. This is of course is not relevant if the system is properly designed and has a crowbar OV protection. But in this case, why pay 2-3 times more for a battery with a built in BMS? The other issue is the overdischarge protection — like I said earlier, I’d rather the battery give it to me all it has when I call on it to do so, even if it means it kills itself in the process. Shorai, EarthX and other powersport lithium batteries all use the same chemistry).

[JimParker256]

Thanks to everyone for all of the replies and info. It gave me a lot to think about. In the end, I am going to go with the Odyssey battery mounted on the inside of the firewall rather than the lithium. I'm just not comfortable with the limitations of the lithium.

Your'e the builder, and it it 100% your decision. You need to be comfortable with whatever you're installing.

But I have to admit that I'm truly at a loss to understand any real "limitations" of the EarthX battery. They are lighter, smallet, retain their charge indefinitely when not in use, and use virtually identical charging profiles as lead-acid (flooded cell or AGM). The only drawback is purchase cost, which may well be nullified because of their much higher recharge cycle life.

Yes, if abused (discharged to an extremely low level - well beyond anything that would constitute "normal usage") it will shut itself down, but only after giving far more amp-hours of service than the comparable lead-acid or AGM battery, both of which will happily discharge themselves to the point where they can no longer be recharged by any means.
There are lots of stories on the web about accidentally leaving the master switch turned on, only to return to a completely dead and useless aircraft battery. That cannot happen with the EarthX LiFePo batteries due to their built-in management system. To me, that is one of the biggest advantages of the EarthX over anything else on the market.

Of course, if your airplane needs more weight toward the nose, a nice, old-fashioned lead-acid battery on the firewall may well be your solution...

Here's the exact link to the Kitplanes article I referenced earlier in this thread: http://www.kitplanes.com/issues/34_12/b ... 972-1.html)

Please note: My comments are specifically directed at the EarthX LiFePo batteries, and not the Shorai or other "powersports" lithium technology batteries that may or may not be the same LiFePo chemistry, or if so, may not be designed to the same safety standards.

[jamesmil]

Rick, the mounting flange of the box is trimmed to match the tubing so the box is resting on the tubing as well as bolted to the angle on the engine side of the firewall. Those angles are also riveted to the tubing at the bottom as well as the firewall along with Hysol 9460 epoxy

[at7000ft]

Jimmy

Is the bottom of that battery box resting on the 'V' of the fuselage cage square tubing? Or just hanging on the stainless firewall?

Rick H

[jamesmil]

Hi all, I think I have finally found out how to post pictures so I’m keeping my fingers crossed that this works.
This is a file of firewall forward pictures that also shows the battery mounted inside on the firewall.https://photos.app.goo.gl/CtHaadJEDeW3G7iv8

[fwellman@att.net]

Thanks to everyone for all of the replies and info. It gave me a lot to think about. In the end, I am going to go with the Odyssey battery mounted on the inside of the firewall rather than the lithium. I'm just not comfortable with the limitations of the lithium.

[at7000ft]

.....

Here is a link to my firewall forward photos:

https://drive.google.com/drive/folders/ ... sp=sharing

Thanks for the FWF photos Brian, just what I was looking for. And nice work.

Rick H

[at7000ft]

At the risk of sounding like a smart—- I like to use the KISS method as much as possible on things, the odyssey is a totally sealed conventional battery that uses standard chargers and charging systems and has proven to be trouble free , I have used them in airplanes and race cars with good service. Also the B/C 8 amp alt, comes with the regulator and crowbar.
Again not trying to stir up any confusion just throwing in my 2 cents worth which the last time I checked it was worth 2 cents

Agree, have used the Odyssey 680 in my current plane for the last 5 1/2 years not problems, using a simple OTS trickle charger.

Rick H

[ykachuro]

Thank you, sir!

[rv10builder]

The insulating material I used was leftover from a friend's Cherokee project. It was an STC kit that was too pricey to purchase outright for us experimenters, but he gladly provided me enough remnants for this purpose. While its intended purpose is for cockpit insulation, I may swap out the material at some point for the material that Spruce sells under the name of "THERMO-GUARD FR". I've used that to insulate the cowling around the exhaust area and quite happy with the results.

The brass strap is a simple means to provide a reliable airframe ground. It's held in place by two rivets and can be easily drilled/removed in the event the battery must come out. That being said, battery removal requires magneto removal due to the space constraint. The battery box sold by EarthX provides for battery retention.

The battery I chose was the 680C, with the C representing "compact", and I bought both battery and box at SNF saving a few dollars. As for grounding straps, I had intended to make only one but ended up with two in an effort to supply the braid equivalent 4 gauge return (supply and return must both be adequate). Save yourself the trouble and just buy a single pre-made from B&C Specialty.

Here is a link to my firewall forward photos:

https://drive.google.com/drive/folders/ ... sp=sharing