Mounting EarthX under front seat

[Zzz]

Looking ahead at my electrical system, I'm planning to use the EarthX ETX36 battery to turn over an O-540. If you're not familiar, they are an innovative, small, lightweight battery using Lithium Iron Phosphate technology. They're small enough to fit under the seat, and I was wondering if anyone else has done the same thing, and if so could you post a photo of your installation?

http://earthxmotorsports.com/shop/etx36e/

Thanks,
Z

[N942VT]

Zane, those batteries are so light I would put it on the firewall to shorten up the wiring. They work better with short runs also.

[Zzz]

Zane, those batteries are so light I would put it on the firewall to shorten up the wiring. They work better with short runs also.

Yeah, just wondering how much firewall space I'll have. I'm okay with that if there's space. I agree, I'd rather not have to run the heavy gauge wire forward through the floor.

[Battson]

You could always use the inside of the firewall, if needs be?

I used the Oddessy PC680 and put that under the seat on the floor, but I don't have any photos at the moment, but I can get some in the weekend.

Thoughts on batteries, this was a problem for me...
I tried a pricey Li- battery to start with, with slightly lesser specs than the EarthX, and not quite as well rated to the PC680. By the numbers alone it should have worked, but I found out that one needs a significant overhead margin in real life.

It had a different power characteristic to the Oddessy. The initial PCA rating is one thing to consider, but it's the sustained response after the voltage has dropped to like 8V when the engine reaches the top of the first compression stroke on a cold morning - that's what actually tests the power character of the battery. That's when you need it to dig deep and really provide an extra whack of amperage to kick the prop back into motion!

The Oddessy's power characteristic is probably at the very lower limit of what'd I'd consider relying upon solo in the BC environment, even though they are considered a powerful, grunty battery for their size. For the first few trips I carried two batteries, just to be safe...

By comparison, the ETX36 is sold as a superior battery to the PC680, so should hopefully be up to the task. I really have no knowledge of them in any use-context.
I also note with interest that it's designed to fit inside the PC680 mounting bracket (slightly smaller), but the weight is similar to the battery I first set my hopes upon. Let me know how you like it!

[Zzz]

You could always use the inside of the firewall, if needs be?

I used the Oddessy PC680 and put that under the seat on the floor, but I don't have any photos at the moment, but I can get some in the weekend.

Thoughts on batteries, this was a problem for me...
I tried a pricey Li- battery to start with, with slightly lesser specs than the EarthX, and not quite as well rated to the PC680. By the numbers alone it should have worked, but I found out that one needs a significant overhead margin in real life.

It had a different power characteristic to the Oddessy. The initial PCA rating is one thing to consider, but it's the sustained response after the voltage has dropped to like 8V when the engine reaches the top of the first compression stroke on a cold morning - that's what actually tests the power character of the battery. That's when you need it to dig deep and really provide an extra whack of amperage to kick the prop back into motion!

The Oddessy's power characteristic is probably at the very lower limit of what'd I'd consider relying upon solo in the BC environment, even though they are considered a powerful, grunty battery for their size. For the first few trips I carried two batteries, just to be safe...

By comparison, the ETX36 is sold as a superior battery to the PC680, so should hopefully be up to the task. I really have no knowledge of them in any use-context.
I also note with interest that it's designed to fit inside the PC680 mounting bracket (slightly smaller), but the weight is similar to the battery I first set my hopes upon. Let me know how you like it!

I watched a video of a guy cranking over his IO-540 and he was registering 396 amps. The ETX36 is rated at 680, so that seems like a good margin?

I like the idea of interior firewall. That's what my friend Steve did on one of his Highlanders.

[jaredyates]

There has been a lot of discusstion on the aeroelectric email list lately about lithium batteries. Those threads should be available in their archives. As I recall, there were some less-than-intuitive results in real-world performance evaluations.

[Battson]

I watched a video of a guy cranking over his IO-540 and he was registering 396 amps. The ETX36 is rated at 680, so that seems like a good margin?

I like the idea of interior firewall. That's what my friend Steve did on one of his Highlanders.

That is what I thought too. It's the dynamic state performance which can kill it. Steady-state, that's probably at 12V. It's the instantaneous dynamic values which matter. By the numbers, the EarthX should be capable. The question is, will it really stand up in real life? I would be looking for someone else using one on a O-540 if you can.

Explanation:
Steady state, say the starter draws 400A. But suppose the capacitive nature of the starter system requires an inrush current of 500-600A, instantaneously when you first turn-key, then the voltage will collapse to maybe 8V for a moment, if the battery doesn't have the capacity or "size" to support the high instantaneous current demand.... Right about then, the engine stops turning just before TDC on the compression cylinder, this happens even with the Oddessy some times, thus the demand for current increases even more, for just a moment, but at 8V the battery now needs to supply about 600A continuously [P = I.V] before the compression problem arose, voltage cannot recover because of the current demand. Because the engine is still not turning at the starter's native speed, the starter tries to draw even more power, and the voltage collapses even further to 5V, but now the current cannot go up because the battery doesn't have anything left to give, so the whole thing grinds to a halt.

That's where the "grunt" or "size" of a larger battery can power through the low point by providing an electrical 'buffet of current' up to almost 700A for the starter to enjoy, and all the while not dropping voltage much below 8-10V. But it still takes a big toll on the battery. I might only get 3 full-power attempts at starting on a cold day.

On sub-zero mornings in the BC with a freezing cold battery, I like to turn the prop over by hand first, to break the oil seal and reduce compression slightly. Not good for the engine, but at least I'm not walking home! I also have someone standing by to hand-throw it past TDC if it stalls there.

[kestrel]

I'd be worried about cold weather performance. I've been eyeing the earthx batteries, but would probably spend the $$ for the bigger one if I get to the point of installing one. ....but right now skis look like more fun than batteries!

--
Bearhawk

[Zzz]

I'd be worried about cold weather performance. I've been eyeing the earthx batteries, but would probably spend the $$ for the bigger one if I get to the point of installing one. ....but right now skis look like more fun than batteries!

--
Bearhawk

We need some cold weather test reports.

[Battson]

There are some big weight savings on offer, I would definitely buy one if we knew they worked.

[marcusofcotton]

There is some history at the Supercub.org site:

http://www.supercub.org/forum/showthread.php?44024-Another-Light-Weight-Battery-Option&highlight=earthx+cold

There are more threads there on these batteries as well. Looks promising, but sounds like they may need to mature in their development yet.