Reconditioning Dynon Backup Battery

[RudiGreyling]

Ok my 2 Skyviews are 5 years old +/- 200 hours of operation and the backup SV-BAT-320 packs did not pass its annual 45min run check.

Horror to my surprise they cost $180 each I need x 2 = $360 and I am situated on the other side of the globe South Africa, so add another $75 for HAZMAT shipping and this is getting a bit expensive...So I needed to make another plan.

So for the sake of Experimental and cost (my Skyview is out of its 3 year warranty in any case) I embarked to recondition them and share here what I have learned....

The SV-BAT-320 pack is simple to open with 4 screws.
IMG_5840

Inside is a simple 6 cell Lithium-Ion 18650 cell (3.7V) battery pack in (3S2P - 3 Series x 2 Parallel) configuration. These look like No-Name brand and the capacity is not listed, but an internet search revealed they are 2200 mah if you can trust the internet.
IMG_5842

On the one side, closed by some covering is a small PCB board, a BMS (Battery Management System) to manage the pack.
IMG_5841

So I had 2 new packs made up with quality branded SANYO cells of 3400mah capacity (50% more capacity). It cost me $50 locally and no special HAZMAT shipping required since it was local in South Africa.

I soldered the BMS board exactly like the orginal but I added an additional touch. I soldered balance lead, standard used in radio control LIPO batteries, to each pole of the BMS and battery pack. Now I can monitor the condition of each cell in the pack, by simply plugging in a Radio Control battery measurement device.
IMG_5845

I balance charged the Battery Pack on my Radio Control Balance Charger on the bench, then I taped the BMS closed and fitted everything back into the Dynon SV-BAT-320 housing.

The battery packs went back into the airplane and each of them passed the annual 45-minute duration test successfully.

I also have the added benefit to check the health of each pack during the annual inspection, by the way of the balance leads on each battery pole. If the cell voltages are different I have the means to balance them back into alignment with the means of simple a Radio Control LIPO balancer, to extend the battery pack life.

So in Summary:
This is a simple standard 3S2P pack than any good Battery Repacking Company can repack for you with higher capacity branded cells, with a cost saving...and if required can easily add a balance monitoring lead for you to inspect the health and balance the cells occasionally to extend its life.

I hope this helps some of you..

Kind Regards
Rudi

[Greg Arehart]

Rudi,

Thanks for the detailed instructions. I've done similarly on my PLB Li battery. All the "official" battery replacement places wanted over $100 to replace the batteries, so I bought new ones and made my own battery pack. Someone is getting rich on these battery replacement schemes.

[Brantel]

Good to see you on here Rudi! We miss you!

Met a guy at Osh from South Africa that said he knows you.

I did not get his last name but him and his son are named Arie and Kian.


Photo shamelessly stolen from Mike Bullock

Oh, and thanks for the write up on the batteries! Great stuff and saves people money!

[Mich48041]

Good going Rudi!
I tried doing the same thing with my D-180 backup battery, but gave up. The problem is that the battery pack fits inside of the D-180. I could not get the new batteries and circuit board and insulating tape all compacted enough to fit back inside of the D-180. If you ever removed the boxed contents of a newly purchased product, then tried unsuccessfully to pack everything back into the package, you will understand the challenge. Not wanting to risk a lithium battery fire, I broke down and bought a new Dynon backup battery pack.

[Carl Froehlich]

As option, design your power distribution scheme so you eliminate the need for backup batteries.

Carl

[Mich48041]

I wanted the backup battery mainly to prevent rebooting during engine cranking brownout. An added benefit is backup in case the aircraft electrical system fails. I had considered a DC to DC converter to maintain Dynon voltage during engine cranking. But buying a new battery was easier.

[n82rb]

Originally Posted by Carl Froehlich

As option, design your power distribution scheme so you eliminate the need for backup batteries.

Carl

you can never eliminate the need for backup batteries if you want redundancy. you either have independent batteries for the units or a two battery system like you advocate. it a single large backup vs smaller backups. to each his own.

bob burns
RV-4 N82RB

[RudiGreyling]

Originally Posted by Mich48041

Good going Rudi!
I tried doing the same thing with my D-180 backup battery, but gave up. The problem is that the battery pack fits inside of the D-180. I could not get the new batteries and circuit board and insulating tape all compacted enough to fit back inside of the D-180. If you ever removed the boxed contents of a newly purchased product, then tried unsuccessfully to pack everything back into the package, you will understand the challenge. Not wanting to risk a lithium battery fire, I broke down and bought a new Dynon backup battery pack.

Hi Joe,
I have not tried to recon batteries for D-180 yet, I have one in my other airplane, so might consider tackling them at a later stage.

Just a comment on lithium fire risk vs. stock Dynon battery. Having opened and deconstructing the original Dynon supplied SV-BAT-320, I have noticed Dynon has not taken any special measures in constructing their LIPO pack, and actually did the least amount of effort and least cost route.

The pack I reconstructed used quality branded cells of higher capacity, proper battery spacing trays and insulated wires from the battery poles to BMS. In addition, I enhanced it with the balance monitoring lead.

So, in a nutshell, my reconditioned pack is superior to the original pack in many ways. I am happy with my decision to recondition, your mileage might vary.

Kind Regards
Rudi

[RudiGreyling]

Originally Posted by n82rb

you can never eliminate the need for backup batteries if you want redundancy. you either have independent batteries for the units or a two battery system like you advocate. it a single large backup vs smaller backups. to each his own.

bob burns
RV-4 N82RB

Ditto Bob! The smaller Dynon SV-BAT-320 backup is a simple drop in redundancy without the need to worry about other decisions like keeping the aux backup battery charged and healthy. The Skyview unit makes that easy for you with a SV-BAT-320.

[NinerBikes]

The Dynon pack does indeed make it easy for you, but it never balance charges all of the cells, and that's a major cause of failure in LiPo battery packs. Lazy cells kill off the harder working cells.

It's all due to variance in production of the battery cells.

Storing LiPo cells with a full 100% state of charge is a good way to kill all the batteries. They do much better in storage, which is how your plane sits, most of the time, at a 50- 60% state of charge, long term. A Li Po cell stored at 3.9V will last easily 10 years, if not stored in extreme heat or extreme cold.