I read through the old threads here, and it appears there are few different models of Antigravity Micro-Start batteries that people are using. There's also at least one new model listed on the manufacturer's website since some of those threads concluded.

I would like to carry one for backup starting of a Lycoming IO-360 (4-cyl, MT prop), and possibly for running an electric fuel pump on a portable fuel trailer. I need it to work at -20F ambient temperature, assuming decent preheating, and keeping the Micro-Start warm.

Would appreciate any advice on model selection.

Thanks

denalipilot wrote:I read through the old threads here, and it appears there are few different models of Antigravity Micro-Start batteries that people are using. There's also at least one new model listed on the manufacturer's website since some of those threads concluded.

I would like to carry one for backup starting of a Lycoming IO-360 (4-cyl, MT prop), and possibly for running an electric fuel pump on a portable fuel trailer. I need it to work at -20F ambient temperature, assuming decent preheating, and keeping the Micro-Start warm.

Would appreciate any advice on model selection.

Thanks

I don't have a specific model to suggest, but would like to offer some general comments about the LFP (aka Lithium Ferrous Phosphate, or Lithium Iron-along with many other names) batteries that might help in your selection process. I'll offer a couple of guesses at the end.

-Below around 50F the LFP batteries begin to lose capacity-they are very temperature sensitive.
-Using an LFP generates heat internally: in a sense it is self heating. On a cold morning hitting the starter the batt will barely turn the engine over. Wait 30 seconds and the heat generated from the first try will warm the battery and away you go.
-The key advantage of all the modern Lithium based chemistries is they have extremely low internal resistance, which means they will give up all their energy in seconds--perfect for a cranking battery. It allows a much smaller capacity battery to start the engine. The downside is just a few starts and the battery is dead.
-Running a fuel transfer pump is a tough load for such a battery as it is a low current draw that simply needs amp/hours of capacity, not flash power all at once. Often an LFP will have to be oversized to be sufficient for pumping or other longer term loads. In short you must calculate the amp/hours required to do the job based on amp draw/time of the pump or other load.
-LFP batteries are marked with an amp/hour rating that is "lead-acid equivalent". In my testing I find the actual useful AMP/Hours from an LFP to be roughly 1/2 to 1/3 the lead-acid equivalent stamped on the case. This is because the LFP's are marketed for starting, where it can give up all its energy at once to make a small LFT do the work of a much larger lead-acid battery-but only when starting.
-The Antigravity batteries use the cylindrical A123 type cell with is mechanically stable and quite shock resistant, but requires accurate voltage regulation—overcharge will kill it fast. Much of the competition uses the "prismatic" cells, which are cheaper, more compact, far more mechanically delicate, and possibly less durable. Most of your handheld gadgets have this type.
-LFP batteries are a minimum fire hazard unlike most Lithium chemistries. They become more chemically stable as they charge; most of the other flavors of Lithium batteries become more unstable as they charge (think Boeing 777). This is key for us, I think.

I think LFP is the way to go once you account for these differences. After much testing of several brands of LFP I am going with 3 Antigravity batteries for my bushplane build. One for each alternator/electrical bus, and the third for a UPS-like backup for the EFIS. Altogether the 3 batteries will weigh less than 6 pounds. I am running a Rotax 912 so these battery weights will not power a Lyc or Continental of course, but the weight savings should be significant there as well.

The key to succeed with LFP is to understand what actual capacity one needs, and size the battery for that need. For example, to start an IO360 the XP-1, kept in a jacket pocket, would likely do a great job. However with so few AMP/hours capacity, pumping 40 gallons of gas might require the XP-10, or bigger.


-M3X

Thank you for the explanation. I guess there's no such thing here as a single silver bullet. My main requirement is a backup means of cranking my engine. Pumping fuel would have been a nice bonus, but I can do that by other means/ power sources.
Good luck with your plane build,
-DP

p.s. Still curious to hear from others about what they are using. Thanks

M3X wrote:

denalipilot wrote:I read through the old threads here, and it appears there are few different models of Antigravity Micro-Start batteries that people are using. There's also at least one new model listed on the manufacturer's website since some of those threads concluded.

I would like to carry one for backup starting of a Lycoming IO-360 (4-cyl, MT prop), and possibly for running an electric fuel pump on a portable fuel trailer. I need it to work at -20F ambient temperature, assuming decent preheating, and keeping the Micro-Start warm.

Would appreciate any advice on model selection.

Thanks

I don't have a specific model to suggest, but would like to offer some general comments about the LFP (aka Lithium Ferrous Phosphate, or Lithium Iron-along with many other names) batteries that might help in your selection process. I'll offer a couple of guesses at the end.

-Below around 50F the LFP batteries begin to lose capacity-they are very temperature sensitive.
-Using an LFP generates heat internally: in a sense it is self heating. On a cold morning hitting the starter the batt will barely turn the engine over. Wait 30 seconds and the heat generated from the first try will warm the battery and away you go.
-The key advantage of all the modern Lithium based chemistries is they have extremely low internal resistance, which means they will give up all their energy in seconds--perfect for a cranking battery. It allows a much smaller capacity battery to start the engine. The downside is just a few starts and the battery is dead.
-Running a fuel transfer pump is a tough load for such a battery as it is a low current draw that simply needs amp/hours of capacity, not flash power all at once. Often an LFP will have to be oversized to be sufficient for pumping or other longer term loads. In short you must calculate the amp/hours required to do the job based on amp draw/time of the pump or other load.
-LFP batteries are marked with an amp/hour rating that is "lead-acid equivalent". In my testing I find the actual useful AMP/Hours from an LFP to be roughly 1/2 to 1/3 the lead-acid equivalent stamped on the case. This is because the LFP's are marketed for starting, where it can give up all its energy at once to make a small LFT do the work of a much larger lead-acid battery-but only when starting.
-The Antigravity batteries use the cylindrical A123 type cell with is mechanically stable and quite shock resistant, but requires accurate voltage regulation—overcharge will kill it fast. Much of the competition uses the "prismatic" cells, which are cheaper, more compact, far more mechanically delicate, and possibly less durable. Most of your handheld gadgets have this type.
-LFP batteries are a minimum fire hazard unlike most Lithium chemistries. They become more chemically stable as they charge; most of the other flavors of Lithium batteries become more unstable as they charge (think Boeing 777). This is key for us, I think.

I think LFP is the way to go once you account for these differences. After much testing of several brands of LFP I am going with 3 Antigravity batteries for my bushplane build. One for each alternator/electrical bus, and the third for a UPS-like backup for the EFIS. Altogether the 3 batteries will weigh less than 6 pounds. I am running a Rotax 912 so these battery weights will not power a Lyc or Continental of course, but the weight savings should be significant there as well.

The key to succeed with LFP is to understand what actual capacity one needs, and size the battery for that need. For example, to start an IO360 the XP-1, kept in a jacket pocket, would likely do a great job. However with so few AMP/hours capacity, pumping 40 gallons of gas might require the XP-10, or bigger.


-M3X

M3X,

An excellent and well explained discussion of a relatively new technology. Thank you!

MTV

M3X really hits the nail in the head with his explanation. I have a 900 amp model. It has boosted my 0-470 with heavy 3 blade 3 times and still had over half a charge. But use it to charge a phone and its pretty much empty after 1 charge. That really showed to me how much these things are really just for boosting.

This one for a portable jump start. It works:

http://earthxmotorsports.com/shop/earthx-jump-pack

Their on board stuff is good too. Excellent CS from good folks in Colorado, USA.