Want Battery Recommendation for Rotax 503

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Victor Bravo

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I figure I can find a few people here who might share their expertise, success, failure, and/or warnings. A LOT of you guys know a hell of a lot more about electrons and amperes and charge rates and voltmeters than I do. By volume, the majority of the aircraft I've owned and operated were powered by rubber bands...

I want to buy a battery to install in my RidgeRunner project. It has a pretty standard Rotax 503 DCDI in it. I have used Odyssey batteries with great success (PC680 in my Cessna, PC545 in my HKS Kolb), and I know they are a very high performance / high quality option. But they're certainly not the least expensive girl in the ho-house.

I found several other types of batteries that ALSO say "sealed lead acid" and "AGM" in the descriptions, at 60-70% of the cost of the Odyssey.

I found some Lithium batteries that are a LOT lighter than the Odyssey, within fifty bucks of the Odyssey price.

Has anyone here used the "Motobatt" brand, the "Aerovoltz" brand, etc. etc. who can offer some guidance?

The Odyssey I would use for this is probably the PC545. I KNOW that is a good battery. What I don't know is if the "sealed lead acid AGM' battery from Motobatt and/or other cheaper brands is good, bad, almost as good, horrible, etc.

I also do not have any experience with the super whiz-bang Lithium "Aerovolt" or "Anti-Gravity" units.

My FIRST choice is to buy something that works every bit as good as the Odyssey, and costs half as much because the brand name is different. But I don't know if that is reality or not.

If the Motobatt and other competitors to Odyssey are crap and not worth the price difference... then my SECOND choice would be to learn whether the lighter lithium batteries are really as user friendly, low-maintenance, safe, abuse-tolerant, etc. as the Odyssey.

All advice is welcome.
 

rv7charlie

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Please specify use: starting, or sustaining onboard electronics after alternator failure.

Charlie
( Herder of electrons in several past lives)
 

MadProfessor8138

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VB.....
For your 503.....you wont need a battery any bigger than what is needed for pretty much any street bike.
I would go with Lithium and save a ton of weight.
Just do a little research on the brand name and see how the motorcycle guys rate that particular brand....they will know better than anyone.

Lithium is the route I'm going with my Rotax 670......

Kevin
 

Cass256

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I'm using an Earth-x 680c with my GPL elec. start 503, mainly for weight and size purposes. They're not exactly cheap compared to lead acid - but with the integrated BMS it's very user friendly.
 
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Victor Bravo

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Please specify use: starting, or sustaining onboard electronics after alternator failure.

Charlie
( Herder of electrons in several past lives)
Main aircraft battery primarily for starting. Will, also run a small facet cube fuel pump and some light to moderate avionics (TXP, Mode C, very low drain glider radio, and maybe charge a small tablet for a GPS). No big strobe boxes or full-suite avionics stack. I removed the strobe box and put in a low-current radio, the only old dinosaur stuff will the pre-existing old style transponder and encoder, and whatever little ADS-B unit I can rig up for experimental use.
 

tallank

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I figure I can find a few people here who might share their expertise, success, failure, and/or warnings. A LOT of you guys know a hell of a lot more about electrons and amperes and charge rates and voltmeters than I do. By volume, the majority of the aircraft I've owned and operated were powered by rubber bands...

I want to buy a battery to install in my RidgeRunner project. It has a pretty standard Rotax 503 DCDI in it. I have used Odyssey batteries with great success (PC680 in my Cessna, PC545 in my HKS Kolb), and I know they are a very high performance / high quality option. But they're certainly not the least expensive girl in the ho-house.

I found several other types of batteries that ALSO say "sealed lead acid" and "AGM" in the descriptions, at 60-70% of the cost of the Odyssey.

I found some Lithium batteries that are a LOT lighter than the Odyssey, within fifty bucks of the Odyssey price.

Has anyone here used the "Motobatt" brand, the "Aerovoltz" brand, etc. etc. who can offer some guidance?

The Odyssey I would use for this is probably the PC545. I KNOW that is a good battery. What I don't know is if the "sealed lead acid AGM' battery from Motobatt and/or other cheaper brands is good, bad, almost as good, horrible, etc.

I also do not have any experience with the super whiz-bang Lithium "Aerovolt" or "Anti-Gravity" units.

My FIRST choice is to buy something that works every bit as good as the Odyssey, and costs half as much because the brand name is different. But I don't know if that is reality or not.

If the Motobatt and other competitors to Odyssey are crap and not worth the price difference... then my SECOND choice would be to learn whether the lighter lithium batteries are really as user friendly, low-maintenance, safe, abuse-tolerant, etc. as the Odyssey.

All advice is welcome.
I used a Shoria motorcycle battery for four years in my motorcycle before I put one in my IO360 powered RV-6. It has been in by RV-6 for about five years now. Weighs about 1/4 of the PC680 and cranks the IO360 better than the PC680.
 

rv7charlie

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OK. We need to start with being aware of the difference between power & energy. At wide open throttle, a Corvette with 1 gallon of gas will outrun a Chevette with 10 gallons of gas. But only for about 10 miles, at most. The Chevette wins a 200 mile cross country race, every time. So, having those differences in mind....

Add up (preferably by measuring with an ammeter) the total continuous consumption of all required electrical gadgets in the plane. Determine how long you need to fly to get on the ground safely if the alternator quits. For something like an RV-x, I use time to empty tanks; that avoids being forced to land early and being stuck somewhere without support. Multiply total amps by hours duration required, and add about 50% to that to allow for declining battery capacity as it ages. Then you can look at discharge curves for various battery types, and pick an ampere-hour (AH) capacity that will meet your needs. You can't just pick an AH number than matches your calculations; batteries' capacity varies with rate of discharge. An SLA battery (Odyssey, etc) is affected by this phenomenon more than the various lithium chemistries, but that's not the whole story. If you see an AH 'equivalent' rating on a lithium tech battery, you need to ask additional questions, and if the mfgr won't answer, walk away. Many of the lithium 'starting batteries' are the Corvette in the above example. They'll spin your engine with gusto, but may go dead in less than a half hour of powering your avionics without an alternator on line. Others, like the EarthX, seem to give honest AH ratings to their aviation batteries. They also have a built-in battery management system, which is (you'd think) a good thing, but it adds multiple failure points to the system. There have been cases where the BMS went south, taking battery power with it.

It's likely that any lithium tech or SLA with enough capacity to keep your avionics alive for a couple of hours will also start your engine just fine, but that's the next thing to check. The Rotax shouldn't take a tremendous amount of power (the Corvette) to crank, but required 'cold cranking amps' should be spec'd somewhere.

I've already mentioned one caution with lithium tech; the other is which *type* of lithium tech. The EarthX and many other lithium 'starting' batteries are LifePO (lithium iron phosphate), which are relatively safe from thermal runaway. Lithium ion (lithium cobalt, etc) which use the same tech as our cell phones, laptops, drones, R/C aircraft, etc might not be the best idea for a man carrying a/c, due to their propensity to thermal runaway (really hot, unstoppable fires).

A lot of guys are running LifePO batteries in a/c now, but I'm not (yet) a fan. It really is new (very expensive) technology, and not as easily integrated into existing electrical systems as some would have us believe. Plus, it can have significant, new, and different effects on safety. For me, it doesn't make sense (yet) for anything other than a 'round the patch', low&slow type a/c, and for that kind of flying I'd have a hard time paying the financial penalty. Your mileage may vary, of course.


Brands: Odyssey has had a great reputation over the years, but a lot of RV drivers are seeing shorter and shorter live span on newer Odyssey batteries. There are lots of anecdotes of the original Odyssey lasting 4, 5, 6 years, and the replacement only lasting 6 months to a year. This is not a controlled scientific study; we can't know how much conditions varied for each battery over the years. But it is a disturbing trend.

My favorite brand is the SLA battery with adequate capacity for my mission, that has the cheapest price tag today. I've run randomly branded SLA batteries in my Lyc powered homebuilts since the late 1990s. I get the same life as the Odyssey branded ones used to get, before people started having trouble with them. The only caution, for starting big 4 & 6 cyl engines, is that some of them are designed chemically to be 'deep cycle' rather than starting batteries, so their internal resistance (one marker for cold cranking amps) will be a bit higher (worse) than the same AH rated battery designed for starting, like the Odyssey. I compensate by simply buying slightly more capacity; an Odyssey is rated at 17 AH; I buy random-branded SLAs rated at 20-22 AH. This has the pleasant side benefit of additional AH capacity in an alternator-out situation. If you can live with with a 12-14 lb battery, then any 17-20 AH SLA will spin the Rotax fast enough to taxi the plane, and likely outlast your fuel. And, depending on the current price of lead, you can probably buy one for less than $50, with a bit of shopping.

Charlie
 

TFF

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The more advance the cells are, the less tolerant they are. That said, I would use the LIFEPO4 types. They are the least finicky of the newer chemistries. It will be half the weight of the Odyssey for same size. If you leave the master on , it’s probably toast but very unlikely to ever catch fire like a LiPoly. Low internal discharge, so it’s pretty much charged as you left it. You are not getting anything cheaper than an odyssey unless you solder your own cells together.
 

rv7charlie

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There are *many* options for quality SLA batteries at 1/2 the cost of Odyssey batteries.
https://www.google.com/search?q=12v+sla+battery&rlz=1C1CHBF_enUS843US843&oq=12v+sla+battery&aqs=chrome..69i57j69i65l3j69i60l3.1829939j0j4&sourceid=chrome&ie=UTF-8

https://smile.amazon.com/s?k=12v+sla+battery&ref=nb_sb_noss_2

12v sla battery | eBay

I've used the Weize, Mighty Max, Universal Power, Powersonic, Apex, and probably others that I can't remember. All have given me good service. (And probably originate in one of only a few actual factories. Like house branded pickles, or cheese, or...)

Charlie
 

Mac Hodges

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Feb 17, 2020
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Hodges Field 4GA0
I figure I can find a few people here who might share their expertise, success, failure, and/or warnings. A LOT of you guys know a hell of a lot more about electrons and amperes and charge rates and voltmeters than I do. By volume, the majority of the aircraft I've owned and operated were powered by rubber bands...

I want to buy a battery to install in my RidgeRunner project. It has a pretty standard Rotax 503 DCDI in it. I have used Odyssey batteries with great success (PC680 in my Cessna, PC545 in my HKS Kolb), and I know they are a very high performance / high quality option. But they're certainly not the least expensive girl in the ho-house.

I found several other types of batteries that ALSO say "sealed lead acid" and "AGM" in the descriptions, at 60-70% of the cost of the Odyssey.

I found some Lithium batteries that are a LOT lighter than the Odyssey, within fifty bucks of the Odyssey price.

Has anyone here used the "Motobatt" brand, the "Aerovoltz" brand, etc. etc. who can offer some guidance?

The Odyssey I would use for this is probably the PC545. I KNOW that is a good battery. What I don't know is if the "sealed lead acid AGM' battery from Motobatt and/or other cheaper brands is good, bad, almost as good, horrible, etc.

I also do not have any experience with the super whiz-bang Lithium "Aerovolt" or "Anti-Gravity" units.

My FIRST choice is to buy something that works every bit as good as the Odyssey, and costs half as much because the brand name is different. But I don't know if that is reality or not.

If the Motobatt and other competitors to Odyssey are crap and not worth the price difference... then my SECOND choice would be to learn whether the lighter lithium batteries are really as user friendly, low-maintenance, safe, abuse-tolerant, etc. as the Odyssey.

All advice is welcome.
Victor Bravo, I have a 503 both in my Skyraider and my Sportster. Both have a Battery Tender lithium battery. They are rated at 14 amps and 240 CCA. They were about $110 three years ago from Amazon and weigh a little under 2 pounds. They spin the heck out of the 503 and have never given any trouble. They don't self discharge so if you let it sit for a while it's still fully charged and ready to go. Just don't leave it on and run it down or you could kill the battery, ask me how I know. I don't see that particular battery listed on Amazon now but if you find one with similiar specs at a good price I think you would be happy. I also run a GPS and Ipad when flying.
 

sptomh

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Joined
Jul 14, 2014
Messages
9
Location
San diego
I have a 503 in my Kitfox Lite. I’m considering a Battery Tender 270 cranking amp lithium battery. It has a full battery management system and only weighs 2.2 pounds (about 10 less than my current battery). I think it may be the same battery as the Aerovolts brand for a lot less money. The management system can shut the battery down if it senses an issue but it can be easily reset. It is only 4.5 amp hours but I’m only running a handheld radio and a auxiliary fuel pump so I think that will give me enough power to get down even if the generator fails.
 

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rv7charlie

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Messages
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Delta,

That's a wet cell battery. I used them (lawn tractor batteries) in my Lyc powered RV4 back in the mid-90s, before SLA batteries became affordable. Since they can vent explosive gasses, and dump liquid acid if turned on edge or inverted, they really should be in a sealed, acid-proof enclosure that's vented outside the a/c. Today, you can buy an SLA (or AGM; same thing) that'll do the work we need, is about 30% lighter, won't vent explosive gas in normal operation, won't spill liquid acid, and can be mounted in any position, for the same money.

Randomly selected example:
12 Volt 22 Amp Sealed Lead Acid Battery
 

Jsample40

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Jan 18, 2020
Messages
44
Location
Western North Carolina
I figure I can find a few people here who might share their expertise, success, failure, and/or warnings. A LOT of you guys know a hell of a lot more about electrons and amperes and charge rates and voltmeters than I do. By volume, the majority of the aircraft I've owned and operated were powered by rubber bands...

I want to buy a battery to install in my RidgeRunner project. It has a pretty standard Rotax 503 DCDI in it. I have used Odyssey batteries with great success (PC680 in my Cessna, PC545 in my HKS Kolb), and I know they are a very high performance / high quality option. But they're certainly not the least expensive girl in the ho-house.

I found several other types of batteries that ALSO say "sealed lead acid" and "AGM" in the descriptions, at 60-70% of the cost of the Odyssey.

I found some Lithium batteries that are a LOT lighter than the Odyssey, within fifty bucks of the Odyssey price.

Has anyone here used the "Motobatt" brand, the "Aerovoltz" brand, etc. etc. who can offer some guidance?

The Odyssey I would use for this is probably the PC545. I KNOW that is a good battery. What I don't know is if the "sealed lead acid AGM' battery from Motobatt and/or other cheaper brands is good, bad, almost as good, horrible, etc.

I also do not have any experience with the super whiz-bang Lithium "Aerovolt" or "Anti-Gravity" units.

My FIRST choice is to buy something that works every bit as good as the Odyssey, and costs half as much because the brand name is different. But I don't know if that is reality or not.

If the Motobatt and other competitors to Odyssey are crap and not worth the price difference... then my SECOND choice would be to learn whether the lighter lithium batteries are really as user friendly, low-maintenance, safe, abuse-tolerant, etc. as the Odyssey.

All advice is welcome.
Hi VB;
I will weigh in here as have had some experience with a cross section of different types of batterys over the last 50 years. Headed up the small crew that activated the original NiCad battery banks on the second stage of the Saturn V rocket ship on the Apollo Moon Project.
Curiously enough, we are both endeavoring to get Ridge Runners aloft (LOL). I originally started out with the KFM 107 engine, but due to safety enhancements and rough field landing conditions, the max take off weight exceeded what the small 25 hp KFM engine could handle.
I recently purchased a new Rotax 503 dual carb setup... to provide the extra power. During the past year I have experimented with multiple batterys... including Ever Start lead acid, AGM, and finally the newest form of Lipo... the Lithium iron phosphate battery made by Twin Power. I had lousy results with the previous small power unit batterys... simply could not handle the cranking repeatedly so went to the AGM variety. Multiple AGM units failed in months... so finally decided to try the Lipo type. During initial research I was very concerned about the potential fire hazard of standard Lipo, so decided to try the Twin Power lithium iron phosphate unit (DLFP 20 HL BS H unit). It offers 400 CA at 1/3 weight of lead acid, and has unbeatable power to spin our "fans". Absolutely the best battery of its type I have ever had the pleasure of using in anything from air craft to hover craft to motorcycles, etc. It does require a special Lipo battery charger, but holds its power for months at a time with no apparent internal drain whatsoever. I recommend it for your application highly. Let's stay in touch as we contend with further issues on the Ridge Runner rascals...
Jay Sample
 

Victor Bravo

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Thanks to all of you guys for the expertise or experience or both. Some of you guys have more skill with electronics than I do with bull***t, which means you're truly world class!

Question: If I get one of the super light Lithium Phosphate batteries, which need a special charger... how will the charging system on the Rotax 503 affect the battery? Will the "old-school" Rotax charging system over-volt or over-amp the new battery?

I seriously doubt that the charging system on the Rotax has any of the special circuitry, protection system, etc. etc. that the special chargers do.

Thanks to all of you again for keeping me informed. I will return the favor whenever I can.

Jay, I will be glad to share anything I learn about the Ridge Runner, but there are some decisions I am making that I would not automatically recommend to others. Meaning I'm willing to experiment with my a$$ on the line long before I'll tell you to run the same experiment on yours.
 

JGlassFNP

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Joined
Nov 22, 2020
Messages
7
Delta,

That's a wet cell battery. I used them (lawn tractor batteries) in my Lyc powered RV4 back in the mid-90s, before SLA batteries became affordable. Since they can vent explosive gasses, and dump liquid acid if turned on edge or inverted, they really should be in a sealed, acid-proof enclosure that's vented outside the a/c. Today, you can buy an SLA (or AGM; same thing) that'll do the work we need, is about 30% lighter, won't vent explosive gas in normal operation, won't spill liquid acid, and can be mounted in any position, for the same money.

Randomly selected example:
12 Volt 22 Amp Sealed Lead Acid Battery
 

JGlassFNP

Member
Joined
Nov 22, 2020
Messages
7
I use an Odyssey in my Hipps, I am running a Rotax 503 with a Profin 3 blade prop. I have Dual carb and ignition,I have not had any issues.
 

rv7charlie

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Charging is worth a separate thread (or entire book). You're likely to be ok with any reasonably sized SLA/AGM lead-acid battery, as long as your charge voltage stays above 13.8V (preferably closer to 14.5V) and your flights are long enough to recharge the battery. Higher voltage obviously charges quicker (don't exceed ~14.8V for extended periods). Virtually all SLA/AGM batteries will be at full charge at the same 'resting' voltage level, so any charging system in the a/c that maintains around 14V will charge any SLA/AGM. Thay take a charge relatively slowly, so aren't likely to overload the alternator unless they are seriously discharged at the beginning of the flight (which, if the battery isn't near full charge, shouldn't happen anyway).

Lithium is more complicated. I won't pretend to know everything about them, but be aware that that 'full charge' resting voltage can vary from design to design, even within the same chemistry 'family'; eg: LifePO. So the particular cells the mfgr chose, the battery management system they chose (or didn't), and the a/c charging system all interact. Most LifePo with BMS, designed to be a starting battery, will likely be fine as a starting battery, but because lithium batteries have such low internal impedance (the thing that allows such small batteries to spin our engines with such gusto), they also can place a very large load on the alternator. With typical automotive style alternators, there's no risk of damage; just voltage sag (which can prevent the battery from actually charging). With the 'dynamo' permanent magnet style alternators typical on Rotax and other small engines, there can be some risk of damage, in addition to the voltage sag from overload. Not saying they *can't* work; obviously quite a few people are using them successfully. But there are more variables in play than with 'traditional' SLA/AGM.

Either type should be examined to be sure that it has enough reserve *energy* to power essential stuff to flight conclusion, if the alternator quits. As mentioned earlier, any SLA/AGM that will start the engine is likely to have enough reserve, but due to the high 'power dump' ability of lithium, and the deceptive marketing by some lithium marketers, the actual amp-hour rating (*not* 'pb equivalent') needs to be determined when doing your calcs.

Overvoltage is always bad, for avionics in addition to the battery itself. I'd worry a bit more about lithium than lead-acid in an overvoltage event. But if there's overvoltage protection installed in the a/c, that avoids the risk of damage.

Charlie
 

sptomh

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Jul 14, 2014
Messages
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Location
San diego
I had the same question about the compatibility of the Rotax 503 charging system and lithium battery’s. Earth X has a good article online on the subject. Bottom line the newer provision 8 engines with multiple coils and magnets put out a smoother current and would be compatible while the older Provision 4 engines would not. At least thats the way I read the article.

 
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