UAV Battery Maintenance for Search & Rescue

[Nighthawk98TJ]

Good morning,

I am a member of a Sheriff's Office Search & Rescue Unit and we are turning up our UAS program at this time and I am looking for some input regarding battery maintenance given some mission-specific requirements. Those pertinent requirements are as follows:

1. Aircraft will be stored in locked containers within vehicles for hasty deployment.
2. Batteries should be ready for deployment within about one hour of a callout.

In order to meet these requirements, I am currently looking at storing batteries that are fully charged in fire resistant bags and shuttling them back and forth from vehicles so that they are not left unattended in a (potentially) hot vehicle. This seems to make sense based on my research about the battery temperature requirements and the Li-Po fire hazards.

My main question is regarding the charge level. Maintaining a 100% charge on these batteries seems to be a bad idea and the batteries will begin to discharge after 10 days automatically. However, in order to meet requirement number 2 above, I am looking for some input as to how we can balance longevity of batteries versus ensuring that they are in a ready or nearly ready state at all times.

The aircraft batteries concerned are for Phantom 3, Phantom 4, and Mavic aircraft.

Thoughts/suggestions/comments are appreciated.

Thank you.

 

[msinger]

One option would be to buy more batteries and cycle through the batteries you're using so the same batteries are not always sitting fully charged.

 

[Nighthawk98TJ]

One option would be to buy more batteries and cycle through the batteries you're using so the same batteries are not always sitting fully charged.

That's a good idea. I didn't think of that!

 

[BigAl07]

We have extra batteries and maintain one complete "flight set" (could be 1 battery or 2 depending on the aircraft) 100% mission ready. This will require some effort and documentation so that you rotate your battery stock and don't keep the same units always ready.

Initially this was a concern but once we started using them more and more and constantly training we realized we rarely ever hit the "Auto Discharge" level any more with our batteries.

 

[Nighthawk98TJ]

We have extra batteries and maintain one complete "flight set" (could be 1 battery or 2 depending on the aircraft) 100% mission ready. This will require some effort and documentation so that you rotate your battery stock and don't keep the same units always ready.

Initially this was a concern but once we started using them more and more and constantly training we realized we rarely ever hit the "Auto Discharge" level any more with our batteries.

Thanks for the reply. Could you provide some additional details about your maintenance cycles? For example, if you have two batteries available for a UAS, how long would you maintain full charge on one battery? What are your discharge days set at? Are you "topping off" batteries? Etc...

Thanks again.

 

[BigAl07]

Thanks for the reply. Could you provide some additional details about your maintenance cycles? For example, if you have two batteries available for a UAS, how long would you maintain full charge on one battery? What are your discharge days set at? Are you "topping off" batteries? Etc...

Thanks again.

We have our DC set to 5 days.

Once the battery goes into Auto Discharge we allow it to do so and bring another one up to 100% in it's place.

We "Top Off" batteries only when we are called upon or if we know ahead of time we will be flying that day.

We have at least 5 batteries for any single aircraft and in some instances as many as a dozen. Each battery is numbered so we track charges, battery status etc on our monthly maintenance logging.

 

[Nighthawk98TJ]

We have our DC set to 5 days.

Once the battery goes into Auto Discharge we allow it to do so and bring another one up to 100% in it's place.

We "Top Off" batteries only when we are called upon or if we know ahead of time we will be flying that day.

We have at least 5 batteries for any single aircraft and in some instances as many as a dozen. Each battery is numbered so we track charges, battery status etc on our monthly maintenance logging.

This all seems reasonable. As we do not have a large cache of batteries at this point, would you suggest a max (10 day) discharge cycle before rotating, or retain a shorter auto discharge cycle and just rotate the batteries more often. We have 2-3 batteries per aircraft at this point.

I should also note that I am comfortable with just one battery at 100% per aircraft as that would provide enough time to bring a second or third battery to 100%, as needed.

 

[BigAl07]

This all seems reasonable. As we do not have a large cache of batteries at this point, would you suggest a max (10 day) discharge cycle before rotating, or retain a shorter auto discharge cycle and just rotate the batteries more often. We have 2-3 batteries per aircraft at this point.

I should also note that I am comfortable with just one battery at 100% per aircraft as that would provide enough time to bring a second or third battery to 100%, as needed.

I'm more conservative and "gentle" on my batteries. I'd rather have more cycles on them than maintaining 100% longer. That's just my personal preference and I do not have stats to back up why I do it this way.

If an aircraft goes out of service (for repairs etc) we change the discharge days to 1 and get them down to storage level asap.

My way does mean more work and more tracking but thus far it works well for us.

 

[Nighthawk98TJ]

I suppose another option that just came to mind would be to leave the batteries at their storage state and use an inverter in a vehicle to top them all up. Get them plugged in as soon as the call comes in, then head out. It usually takes 30-45 mins to get on scene anyway, plus other logistics time would mean that the batteries would have a good hour or more to top off in the vehicles before they were needed...

 

[WetDog]

Or you could just leave the batteries on a charger in a safe place (like you plan).

Yes, you won't get 'optimal' use out of them, but they will last 2, 3 or perhaps 4 years that way. Then you get new ones.

This is always an issue with Emergency Services stuff. You need them for emergencies which don't give you time to spool up. You just trade off longevity for function. We have two P3Ps with a total of six batteries on full charge at all times. We do cycle them off with others as we've collected a few more batteries over the years. I've not seen any significant degradation of flight times in 2 years of use. There well may be some accelerated decay of storage but we don't notice it.

I always have at least two batteries siting on full charge as there as photography opportunities happen (and go away) quickly.

 

[Nighthawk98TJ]

Or you could just leave the batteries on a charger in a safe place (like you plan).

Yes, you won't get 'optimal' use out of them, but they will last 2, 3 or perhaps 4 years that way. Then you get new ones.

This is always an issue with Emergency Services stuff. You need them for emergencies which don't give you time to spool up. You just trade off longevity for function. We have two P3Ps with a total of six batteries on full charge at all times. We do cycle them off with others as we've collected a few more batteries over the years. I've not seen any significant degradation of flight times in 2 years of use. There well may be some accelerated decay of storage but we don't notice it.

Good info, thank you. Leaving them on a charger may not be optimal for our hasty deployment use, as the UAS are currently kept in the pilots' personal vehicle for quick deployment (with batteries shuttling back and forth to keep ambient temp exposure down). Since the batteries are going to discharge at a max of 10 days without use, it may make sense for us to keep them at storage state and charge up on the go.

My understanding is that Li-Pos kept at storage levels rather than 100% are less prone to heat damage (bulging, explosion, fire, etc.). Anyone have any insight as to whether or not it would be advisable to store batteries at storage levels in a metal ammo can inside the trunk of a vehicle?

 

[BigAl07]

Good info, thank you. Leaving them on a charger may not be optimal for our hasty deployment use, as the UAS are currently kept in the pilots' personal vehicle for quick deployment (with batteries shuttling back and forth to keep ambient temp exposure down). Since the batteries are going to discharge at a max of 10 days without use, it may make sense for us to keep them at storage state and charge up on the go.

My understanding is that Li-Pos kept at storage levels rather than 100% are less prone to heat damage (bulging, explosion, fire, etc.). Anyone have any insight as to whether or not it would be advisable to store batteries at storage levels in a metal ammo can inside the trunk of a vehicle?

LIPo batteries "Can" be very volatile if misused but with today's "Smart Chip" on board a lot of that has been "programmed out". We keep them in their own "Cases" but not metal ones. GoProfessional type cases for easy transport. During "mild" weather they are in the vehicle with the sUAS but when we see temps outside of "Human Comfortable" (35 - 95 for instance) they come inside the building with us.

LiPo lose capacity and "punch" when left at 100% for extended periods of time. We keep them at "Storage Charge" until we get the call and immediately put them on charge (in office or in vehicle) unless we know ahead of time.

 

[Nighthawk98TJ]

Great information. Thank you!

 

[O6-Hammerhead]

We keep ours mission ready at all times and budget to replace half of our battery stock each year. Minutes count and battery failures are just not an option. Agree with earlier post that mentioned trading readiness for longevity.

PM me for more details about how we manage our battery stock.

 

[ravedog]

We keep ours mission ready at all times and budget to replace half of our battery stock each year. Minutes count and battery failures are just not an option. Agree with earlier post that mentioned trading readiness for longevity.

PM me for more details about how we manage our battery stock.

Why not just post your management tips here?

 

[O6-Hammerhead]

Would love to, but we aren’t allowed to post procedures. Silly, but gotta follow the rules so I can keep eating and sleeping indoors.

 

[ravedog]

Ahhh. Got it. Thought that might be the case.

 

[msinger]

Would love to, but we aren’t allowed to post procedures.

Assuming this procedure is generic enough to share with others, feel free to PM it to me and I'll repost it as an idea I came across while searching on Google

 

[O6-Hammerhead]

Ummmmm. No. But thanks for the suggestion. [emoji16]

 

[msinger]

No worries. I didn't think a procedure that involved taking care of batteries was going to be top secret.