Flume 2 Battery Box

UPDATE I used alkaline AA batteries for about 2 months before the Flume app reported that the batteries were running low and then stopped working. It appears that Flume doesn't like the discharge curve of the akaline batteries, lithium AA batteries will maintaion 1.5V nominal through the entire useful life of the battery, dropping off a cliff when it's depleated. Whereas akaline AA batteries will start at 1.5V but quickly drop to 1.4V after about 100-200mAh are used up. The “dead” alkaline AA batteries measured 1.4-1.45V when I checked them, so in any other application they would be considered “new”. I replaced them with cheap EBL lithium AA batteries from Amazon and I'll report back when they start to fail (https://www.amazon.com/EBL-Pack-3000mAh-Lithium-Batteries/dp/B08SVZT3RH).

This is a battery box for a Flume 2 water monitor it can be used to replace the original battery packs. There are numerous reasons not to use this as outlined in this article https://help.flumewater.com/en/articles/6349883-why-flume-uses-a-custom-battery-pack but in theory, if you use the Lithium AA batteries in this battery box, the performance should be the same as the OEM. 

The battery springs that are exposed are 12mm x 12mm and the other tabs are 12mm x 26.50mm Amazon link https://www.amazon.com/dp/B09DSNM1Z5

Refer to the photos, but you will need to remove and trim the tabs from the 12mm x 12mm battery springs and solder pairs together (you will need a positive and positive and negative and negative pair). These will make the “front” battery springs the back of which will make contact with the flume monitor. There is just enough metal exposed to keep good contact. 

I used a trimmed piece of cardboard and a drop of CA glue to hold it in place to prevent the top back battery spring from sliding down and contacting the bottom, back battery spring, I could have printed a part to do this, but YOLO. 

The lid just sits on top of the body. It is designed just to hold the batteries down when the flume monitor lid is closed. Closing the lid of the flume monitor will hold everything in place. 

I printed the battery box in ABS, 0.2mm layer height and 15% infill. It flexes a little when all the batteries are loaded in, but once you put it in the flume monitor the additional support from the case keeps everything in place.

For reference, my original OEM batter pack came with Enegizer Lithium Ultimate AA's (nominally 3.0Ah so 6.0Ah in 2S2P), my second OEM pack had Flume branded lithium batteries (2.9Ah printed on the label so 5.8Ah in 2S2P). I am testing out alkaline batteries (2.6Ah so 5.2Ah in 2S2P and 10.4Ah total with both packs). In theory it should last longer for cheaper and I'll have more time where the monitor is reporting low battery before it actually stops working. Even if it doesn't last longer hopefully it will to be a magnnitude cheaper. IN any case, it's far more convenient to replace batteries that I can get off the shelf vs. ordeering a special pack from Flume. YMMV. 

I have included both STEP and STL files.