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Weight Reduction Program

rv6ejguy

Well Known Member
My 6A has always been a bit heavier than I'd like so I decided since the AGM batteries were now marginal on resting voltage and passing the annual load tests, it was time to move them out and move some lithium batteries in. I also wanted to ditch the vacuum pump and 2 vacuum gyros. With annual time here, it seemed like a good time to do this work.



Vacuum pump was driven off the left camshaft.



Two Shorai 18 AH batteries will replace the PC680 main and Powersonic 18 AH backup battery.



Vacuum pump hardware out of the plane.

After weighing what's coming out and going back in, looks like I'll shed over 29 pounds total, mostly from the batteries. The 680 weighs 14 pounds, the backup, 12.2, the Shorais only 2.2 each.
 
I found the Shorai batteries on fortnine.ca site. Is that where you got them from? How did you decide on that model number, since there are so many to choose from?

Phil
 
I found the Shorai batteries on fortnine.ca site. Is that where you got them from? How did you decide on that model number, since there are so many to choose from?

Phil

I bought mine from the local Shorai dealer, Sport Cycle. I searched the Shorai website first to find the AH rating and post configuration I wanted to match what I had in the plane already to make hookup as straightforward as possible.

I'll have to use some spacers to bring the front battery up to a similar level as the PC680 and some lateral spacers for the rear backup battery to keep it snug in the old box. The backup battery resides just aft of the baggage bay bulkhead. It feeds only the essential bus through a 30 amp fuse, 10 gauge wire and heavy duty toggle switch- not used for starting.
 
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I finally had some time to work on the plane today and got both batteries installed.

Took a couple hours to design and build a tray to raise the battery up to the same level as the old PC680 to meet all the battery cables and have the base fit snugly against the existing captures.





I used the old hold down hardware.



The backup battery aft of the baggage bay was much easier. I just used shorter bolts for the hold down strap and took up the extra space in the tray with the special HD foam that Shorai provides with their batteries. Not so pretty but quick and functional.

Hard to get over how light these things are compared to the AGMs I removed! Will recalculate the W&B and see where I'm at.

On to the panel upgrades next and finishing the rest of the inspections for the annual.
 
Hey Ross. Is there anything other than price that steered you toward the Shorai batteries and away from brand “x”? I take it that there is no BMS system in these batteries and that is obviously not a concern for you. Do you have any insight ma to share on that matter?
 
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Hey Ross. Is there anything other than price that steered you toward the Shorai batteries and away from brand “x”? I take it that there is no BMS system in these batteries and that is obviously not a concern for you. Do you have any insight ma to share on that matter?

There is no BMS in the Shorai batteries. Given the sensitivity of this topic here, I'd prefer not to comment further other than to say I carefully evaluated user feedback on both brands and talked to Dave Anders after he installed twin Shorais in his RV. I suggest everyone do their own research and choose which they think is best for them. Price was not a consideration in my case but these are less expensive than the other brand.

I will be installing an OV warning buzzer to compliment my current under voltage warning system. I can isolate the alternator from the primary battery and the backup is not connected to the alternator at all.
 
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Any special charging consideration with the Shorai 18 AH batteries?

They do state you can charge with conventional chargers at low rates but you should also monitor voltage. Traditional alternator/ regulators are fine too but they are some cautions on charge rates and it's not a good idea to start out with a depleted battery and go flying.

I may buy a Shorai wall charger which is specifically designed for them to avoid having to monitor voltage while charging.

I'm eager to see how these turn the engine over, hopefully be doing a compression check next week and running again soon after.
 
I've been using 2 Deltron Lithium batteries in my Lancair for years, they have been trouble free. I keep them on a Deltron Lithium charger. They work great and weigh almost nothing.
 
Alt. current limit?

Make sure to have a device to disconnect the Alt. output if the alt. regulator faults and produces max output and causes thermal runaway of the battery.
 
Keep in mind that once installed in a aircraft the warranty on a shoria battery is void and the manufacturer will not provide any support.
 
Keep in mind that once installed in a aircraft the warranty on a shoria battery is void and the manufacturer will not provide any support.

Not recommended for aircraft (neither are PC680s BTW) but I know a couple people who got warranty on their's after leaving the master on. I do think in most cases, you won't be covered. That being said, few people seem to report any problems. They appear to be very durable from many reports I've read. This was my main reason for choosing the brand.
 
Buttoning up the airplane after the annual and mods. Total weight loss was 29 pounds. I don't notice any difference in how the engine turns over compared to fresh PC680s but this engine is only 134 cubic inches so doesn't draw much starter current compared to a Lyc.

Empty C of G changed half an inch.

As a sidenote, compression was up a bit on all cylinders which is good. It seems to like a diet of 92 mogas a lot more than 100LL which always caused a slow loss of compression each year.
 
I was up for a test flight of sorts today, running some charging and voltage tests with the primary and backup batteries. Looking at run voltages with the alternator switched off. I'd be confident in getting at least 1 hour of total engine run time off the 2 batteries with minimal electrics on if the alternator took a dump.

Once fully charged, the engine does turn over a bit faster with these batteries compared to a fresh PC680.

I didn't notice any better climb performance with the 30 pounds less weight but I have 30 pounds more useful load now with the elimination of the vacuum system and AGM batteries.
 
Battery Update

With the cooler weather here now, I was curious as to how the Shorai battery would crank the engine. My hangar in the winter sits around 6-8C most of the time, so not really cold.

The Shorai still cranks the engine over very well at these temperatures. I fly every 3-4 weeks on average and don't put a charger on these batteries at all. Self discharge rate seems very low when I check voltage before startup.

So far, very happy with these batteries.
 

I'd recommend sleeving that crossbar with something non-conductive... A large piece of heat-shrink tubing, or spiral wrap with electrical tape or self-fusing silicone tape. You've got a good space between each terminal and the bar, but when you start working around them with screwdriver (or nutdriver) and the bolts themselves, you'll be getting dangerously close to a short...
 
I'd recommend sleeving that crossbar with something non-conductive... A large piece of heat-shrink tubing, or spiral wrap with electrical tape or self-fusing silicone tape. You've got a good space between each terminal and the bar, but when you start working around them with screwdriver (or nutdriver) and the bolts themselves, you'll be getting dangerously close to a short...

I remove the negative if I'm working back there. Haven't shorted a battery in about 40 years.
 
Ross;
Are you using anything special for a voltage regulator? I believe lithium would do OK up to 80% charge with a normal VR for lead acid, but the last 20% I am not so sure.

I do see they make VR's to charge lithium batteries, but haven't looked into them yet. But I might.
 
Ross;
Are you using anything special for a voltage regulator? I believe lithium would do OK up to 80% charge with a normal VR for lead acid, but the last 20% I am not so sure.

I do see they make VR's to charge lithium batteries, but haven't looked into them yet. But I might.

Shorai says std VRs are generally fine and their literature has recommended voltage ranges which fall about in the middle of where mine sits at.

As with almost all Lithium batteries, they do caution against slamming a bunch of amps into a highly discharged one. Fortunately with EFI, about 9 blades gets me started every time which doesn't draw much juice out of it.

I know a few people running these batteries for a while now and none have mentioned a special VR.
 
I bought one of those for my motorcycle. Yes, very light compared to AGM batts. However, I thought I saw that they need at least 14v to achieve full charge. I think that's what I've seen in their literature.
I never wanted to have a higher risk of a thermal runaway to save a hand full of pounds. I each his own.
Be safe
Rich
 
I am planning on an airplane version of the LI battery for my primary start battery, but don't really see the need for the same for a backup. I was going to use the biggest LI jump pack (32ah) that I could find to use as an emergency jump pack, but mount it and wire it up to also function as a backup battery. It would only be charged with ships power if I was using it as a backup battery. Other than that I would charge it separately, on the ground.

To jump start someone else, or myself, I would need to run jumper cables.
 
Ross,
I am going to look into it a bit more. I know that too much amperage at the start of the charge cycle is a problem. I think even Brand X states a maximum rating for the alternator for each size battery. Maybe that is how they limit the max current, without some kind of external current limiter.

I will look into it some more. One more thing to learn.
 
I bought one of those for my motorcycle. Yes, very light compared to AGM batts. However, I thought I saw that they need at least 14v to achieve full charge. I think that's what I've seen in their literature.
I never wanted to have a higher risk of a thermal runaway to save a hand full of pounds. I each his own.
Be safe
Rich

Most alternators charge at 14.2-14.4V. Hundreds of thousands of motorcycles, ATVs and watercraft have been using Shorai lithium batteries now for something over a decade with standard charging systems. Doesn't seem to be an issue.
 
Shorai's site is here: https://shoraipower.com

They say 13.6 to 14.4 volts is ok for charging however, fully charged, they are at 14.4. They say to trickle charge if below 13.1V. You probably shouldn't attempt to start with it below 13.2V.

At temps below 0F, they suggest leaving on a load of 3-4 amps for 4-5 minutes before attempting cranking to internally warm the battery for best performance. This may also be important for battery life once the alternator starts charging. They have some cautions about charging a very cold battery below 0F.

As always, there are advantages and disadvantages to almost any choice you make.
 
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I was up for a test flight of sorts today, running some charging and voltage tests with the primary and backup batteries. Looking at run voltages with the alternator switched off. I'd be confident in getting at least 1 hour of total engine run time off the 2 batteries with minimal electrics on if the alternator took a dump.

Once fully charged, the engine does turn over a bit faster with these batteries compared to a fresh PC680.

I didn't notice any better climb performance with the 30 pounds less weight but I have 30 pounds more useful load now with the elimination of the vacuum system and AGM batteries.

Ross,

I thought that you routinely test the enduance of your batteries. I am curious how the 18 a/hr shoai compared to the 18 a/hr 680. I know some of these lithiums have an a/hr rating (lead acid equivalent) that is 3 times it's actual capacity, in terms of moderate (1/2C) drain levels. I assume they elevate it because their high drain (i.e. starting current levels) ratings are much higher than lead acid.

I have been considering non-bms batteries and the shorai seems highly rated.

Larry
 
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I test at annual each year pulling 10 amps out of them for an hour and see what the voltage falls to.

I do believe that these may not do this test as well as the old 18 AH AGM batteries did but an actual test will confirm or deny that.

I consider the AGMs functional down to about 10V and these Shorais maybe down to 13V. Of course there is no BMS on these so in an emergency, you can run them down to the point where they won't supply enough current to charge the coils or fire the injectors any more.

With two 18AH batteries, I'm pretty sure I can fly for at least 1 hour after alternator failure with just the engine electrics running and probably 2+ hours. That's more than long enough for my flying locale.

I will publish the results of my standard low load testing at annual time though.
 
Weight a minute...

With two 18AH batteries, I'm pretty sure I can fly for at least 1 hour after alternator failure with just the engine electrics running and probably 2+ hours. That's more than long enough for my flying locale.

I will publish the results of my standard low load testing at annual time though.

Ross,
I appreciate your candor and sense of weight awareness seemingly lost these days given most new RV's equipment lists.
Both my RV4 and RV6X weigh less than 950 lbs mainly due to doing without, rather than any magical weight reduction techniques. When Odyssey batteries came available in the late 90's I bought one the first for my RV4 which had a marginally effective motorcycle battery previously installed as aircraft batteries were (are still) heavy and inefficient.
I look forward to your test results.

Thanks for being an Experimenter...
V/R
Smokey
 
The Odyssey batteries seemed magically light when I was building my plane about 20 years ago. Always happy with them and had good performance and life with them.

I was attracted to lithium batteries when they came out but after seeing many problems and failures with one brand, decided to wait a few years to absorb more real-world reports from users.

Still early days with my Shorais, we'll see how they pan out a bunch of years down the road.
 
The Odyssey batteries seemed magically light when I was building my plane about 20 years ago. Always happy with them and had good performance and life with them.

I was attracted to lithium batteries when they came out but after seeing many problems and failures with one brand, decided to wait a few years to absorb more real-world reports from users.

Still early days with my Shorais, we'll see how they pan out a bunch of years down the road.

On my phone, sitting next to my bed, I want an awesome BMS that makes the battery safe.

I kind of look at a BMS on an airplane battery like a limp home mode on a car ECU. It will shut down to protect itself, even if that is not the best short term choice for me or the airplane.

I did think that the BMS was required for proper, safe, charging, but maybe not.

I stumbled on (accidentally) a youtube video of the owner of Viking engines doing a capacity test. He ran his engine on a lead and lithium battery until they hit a min voltage. The lithium battery far outlasted the lead acid. I want to say more than 3 times. I think the rated AH capacity was about the same.
 
Interesting. I can do a quick test here on my backup Shorai as the external charging wires are easily accessible. Will report my results.
 
I would need one of their biggest batteries to start my IO-540. 36 ah capacity should keep the engine turning for at least 1.5, maybe 2 hours. 2 of them give me a whole bunch of engine run time without the alternator.
 
Another year on my Shorai batteries. Nothing unusual to report. Engine cranks over briskly, load test is good. The airplane can sometimes sit for 40 days between flights. I never charge between flights and resting voltage is always good when I check before startup.
 
Ross - just curious to know if you are still doing the 10 amps for one hour capacity test on these batteries? If so, what voltage do they start at and what's their voltage at the end of the test?
 
Ross - just curious to know if you are still doing the 10 amps for one hour capacity test on these batteries? If so, what voltage do they start at and what's their voltage at the end of the test?

While these batteries turn the engine over very well, they won't sustain the same long term/ low current draw as the PC680. I show the results of my test here: https://www.youtube.com/watch?v=FPBaAil4dNg

I'd suggest 2 of the 36 AH rated ones for those with electrically dependent aircraft.
 
Russ,
You might want to take a look at the Shorai charger. If I understand correctly, it balances the cells in the battery while charging. I use it every oil change in case the battery needs to be balanced. It plugs into the charging port on the battery. My RV-8 has a 27amp Shorai and it has been good for the past ten mos. I’m using CPI on one side and a Slick on the other so I only need one battery. When mag needs service I’ll switch to two Shorais and dual CPI.
 
I never charge my Shorais between flights and just checked my primary here this morning for a customer who runs another battery brand and was concerned about low voltage. Mine read 13.44V, no load after sitting for 2 weeks.
 
Russ,
You might want to take a look at the Shorai charger. If I understand correctly, it balances the cells in the battery while charging. I use it every oil change in case the battery needs to be balanced. It plugs into the charging port on the battery. My RV-8 has a 27amp Shorai and it has been good for the past ten mos. I’m using CPI on one side and a Slick on the other so I only need one battery. When mag needs service I’ll switch to two Shorais and dual CPI.

What do you see for resting voltage after a 7-14 days off the charger?
 
Just a caution...Shorai uses a fake "PbEq" (lead equivalent) amp hour rating system. Actual capacity is about a third of what's claimed.

"36 Ah PbEq" is roughly 12 actual Ah.
 
I also have an Aeronca Chief 11BC, with a C85 and full electrics. Weight is an issue, so I replaced an Odyssey PC680 with a Shorai Lithium Iron. This saved 6kg, the 680 is actually much more powerful than the C85 needs. Worked well until I inadvertently left the Master on overnight when I put the Shorai charger on, the next morning the battery was flat and it would no longer charge.

After frantic phone calls to the dealer it quickly became clear that the battery was ruined, one of the cells had been destroyed. I eventually got it to charge to about 11V but not the 14V it normally held, and I had to put the PC680 back in. Shorai here in the UK were useless, wouldn't even answer any support call. The case is sealed so very unlikely they could have repaired it, and I don't want to repair and use a high energy battery that is stored in the cabin.

The dealer said they had a lot of experience like this, once the battery drops below a certain low voltage it will be permanently damaged, as a result he no longer sells these batteries. Most expensive battery I've ever bought, lasted about 6 weeks!

The alternative is something like an EarthX which has protective circuitry that won't allow the battery to fully discharge, but it is 50% more expensive than the Shorai. Lithium batteries are powerful but need to be treated cautiously, they are very easy to destroy, my next attempt will only be with an Earthx or similar.
 
Yes, the Shorai dealer I purchased mine from warned me about fully discharging them saying that would usually permanently damage them and I've mentioned this before.

I have a light that stays on on my panel when the bus is powered to give me an indication that I forgot the master or backup battery switch.
 
Not recommended for aircraft (neither are PC680s BTW) but I know a couple people who got warranty on their's after leaving the master on. I do think in most cases, you won't be covered.
I once had a problem with a PC680, took it back to the dealer who asked me what I was using it for. "To power accessories in my RV." Not a lie and I got the warranty replacement.
 
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