3DR Solo Battery Case (fully enclosed and open versions) by KDan

Last crawled date: 3 years ago

FINAL UPDATE: 1/23/19 I have not updated this model for over 8 months now and don't expect to work on it anymore. My original intention was to create a case which closely matched the size/shape and capacity of the original. After buying cells from many different sources I have been unable to source any cells that will fit into a case that closely resembles the original and doesn't look like some kind of gross franken-battery. I have no interest in flying my Solo with a big gross looking generic battery pack strapped to the drone. For those who do - good for you. As far as I'm concerned the Solo is dead. The range was always weak compared to even 3 year old DJI drones, and the gimbals never worked worth a darn. Despite many isolation mount hacks, special HDMI cables, etc, etc, the Solo gimbal was - and still is - very shaky and inferior to the competition. TIme to move on - there are many other more cost effective options that are better right out of the box without a need for a bunch of aftermarket mods (green cubes, etc) that still leave the Solo well behind the capabilities of a an old original Mavic Pro.
This case design was created in DesignSpark Mechanical. If anyone wants the original RSDOC CAD files to work on, message me and I'll send them to you.
UPDATE: 4/30/18 Modified the lower case (both versions) to allow more clearance for the power connector. Now that I have cracked open an original case - I can identify and fix problems inside the case. More improvements will probably be coming.
UPDATE: 4/17/18. Top case revised with ledge to make accurate assembly easier. Extended top cover forwards by 1mm to provide additional clearance for the latch in the event that parts alignment is not perfect during assembly.
Removed duplicate top cover for open case version - both versions now use identical top case.
This is a replica of the 3DR Solo Smart Battery Case. I tried to stay close to the original design in order to keep the stock streamlined appearance. I'm not interested in creating a Frankenstein case at this time - I might consider it later.
The fully enclosed version is a three piece design that needs to be bonded together. I've found that E6000 works pretty well on PLA or PETG. 30 minute epoxy should also work but might not be as strong. Gap filling super glue would probably give a strong bond, but there would not be much working time to get things aligned. Acetone works well on ABS of course. The three piece design makes the parts easy to print with no additional supports strictly needed.
It's really quite easy to rebuilt a new battery for the Solo if you have a pack or cells that will fit into the original case volume. Unfortunately, there are very few options for 4S 5200 mAh packs that will fit, but if you are willing to drop down to a 4500 mAh, or 4000 mAh pack, there are more choices. If you are building a pack from 5200mAh bare cells, you might be able to get everything to fit. Offsetting the top cell as in the original Solo pack might also be needed.
If you have a pack that won't quite fit in length or height, there is an alternate version (green one in the pictures) that does not fully contain the battery. It Isn't quite as plug n' play as the fully enclosed version (or the original 3DR battery), but it does have a cover that snaps over top of a battery. If using this version the battery should be secured into the open battery tray with Velcro or something . It is currently a two piece design. Remember, if you ever disconnect the battery cells from the BMS, you will need to completely discharge the cells (slowly) and fully charge them again (through the BMS and stock charge connector) in order to re-calibrate the BMS.
Re-calibrating the battery management circuit for the new pack is not complicated. There is nothing you need to do except initiate a reset with a fully discharged battery, and then allow it to fully charge..
The BMS low voltage detection will be triggered if the battery voltage drops too low (fully discharged) or the battery is disconnected. When adequate voltage is reapplied (typically through the initiation of a recharge) the processor restarts and begins measuring current and elapsed time until the battery reaches a fully charged voltage level. At this point the mAh absorption value is saved and this is used as a reference for battery capacity. This process occurs upon restart and should not occur when the battery charge is maintained in the normal operating range.
With the capacity of the battery now known, it is a simple calculation to measure charge percentage remaining. The processor measures the mAh discharged since the last full charge, subtracts it from the total capacity and divides the result by the total calibrated capacity. To convert to percentage it takes that value and multiplies by 100.
As the battery cells age, their capacity gradually decreases, which is why 3DR recommends discharging the battery to cutoff every few dozen charges in order to remeasure the charge capacity. It is important to not discharge the battery to these low voltage levels quickly. Slow is better because it minimizes heating of the cells that can damage them at low voltage levels. In any case, the discharge to cutoff should not be done frequently, because it stresses the cells somewhat even when done very slowly.
The most important thing is be very careful not to short out any of the battery wires when working on it. If you are not 100% comfortable with your ability to avoid this, you might want to reconsider doing it.There is a fire hazard.
I kindly request that you abide by the license You are free to make as many as you like for your own use, but please don't use these files for your own, or anyone else's profit (that includes paid printing services). I reserve the exclusive right to sell them myself if I so choose.
I also reserve the right to remove or update these files at any time. I recommend checking for the most updated version before printing because these files are absolutely a work-in-progress.https://www.youtube.com/watch?v=bgCwRn5fC_A