Ventilation of Lithium Battery Cases - Page 1
Forum section: electronics / general

author: bullet308
author_rank: Frequent Contributor
timestamp: July 27, 2012, 10:09:02 pm
content: Hi:I am currently designing a product that uses a section of Schedule 40 6063 aluminum pipe as a battery case. An important design criteria is that the device be highly water-resistant. For maximum battery life (both shelf and service) I intend to ship with x2 Energizer Ultimate AA lithium batteries. Current draw will range from 5mA in standby up to 50mA running wide-open. The data sheet for the batteries dont seem to mention anything:http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CGkQFjAA&url=http%3A%2F%2Fdata.energizer.com%2FPDFs%2Fl91.pdf&ei=8hATUNXbKeP00gH8hYHgCA&usg=AFQjCNEk6hgatr_w8oFA9lUtVKXwc9TLkw&sig2=RL4XYtaJrBr0nN0e45LdOwAre their any issues with running these batteries in a sealed enclosure?Thanks in advance:

author: digsys
author_rank: Unknown
timestamp: July 27, 2012, 11:31:37 pm
content: At 50mA, there'll be no problems. But I'd still design one end to be able to "pop-off" under pressure.The main concern will be external short, maybe add a 100mA Polyfuse. If they are a snug fit, then theAl will provide heatsinking as well, ALL good.

author: amyk
author_rank: Super Contributor
timestamp: July 28, 2012, 10:08:04 am
content: I would certainly design in a vent valve or similar, which prevents ingress of water while allowing egress of any gases generated by the batteries should they vent. Otherwise you may end up with a pipe bomb.See here for some examples of what happens in flashlights when batteries vent, a similar situation:http://www.candlepowerforums.com/vb/forumdisplay.php?107-Smoke-and-Fire-Hot-Cells-and-Close-Calls-The-dangerous-side-of-batteries

author: SeanB
author_rank: Super Contributor
timestamp: July 28, 2012, 11:06:22 am
content: Had the boss's maglite yesterday, with the 2 duracells somewhat solid in the housing. Drilled a drywall screw into the end of the lower one and pulled it out with pliers before it got too hot, as it was leaking but still ran the torch. Batteries were expired mar 2010, so very likely to leak after this time. Top was luckily not leaking yet. I have seen the OHL clones burst at the seams as the batteries corrode. Best is to put in a weak section as a bursting point that will fail first if overpressure is present on the inside. Machine a section of the case to around half the thickness of the wall, and it will serve the purpose while not compromising the waterproofing.

author: bullet308
author_rank: Frequent Contributor
timestamp: July 28, 2012, 01:36:10 pm
content: Thanks for the feedback, all.I read the CP forum entries of spectacular lithium battery failures with some alarm. However, a search seems to reveal that most if not all of these issues seem to be associated with CR123As, a type already considered and rejected for my application (not the right size to fit available tubing, for one thing). I can find no mention of malfunctions associated with the EverReady AA lithiums. If I missed some that y'all are aware of, please let me know. Those threads were enough to make me scrap my CR123A flashlights, though. :-/However, I know the chemistry is the same so I need to be concerned. Fortunately, my design already accounts for catastrophic explosion in that while the tube is solid and sealed on one end with a solid aluminum plug, the other end is a tight sip fit into a plastic housing with a thin plastic barrier sealing the opening in the housing and the tube retained with a pair of set screws. These features weren't intended as a "blowout" feature for an overpressure situation but should serve nicely. Also, the tube would tend to pop out of the housing before pressure got anywhere near enough to burst the tube, in any case.I am continuing my research. Thanks again.

author: IanB
author_rank: Super Contributor
timestamp: July 28, 2012, 04:56:57 pm
content: Quote from: bullet308 on July 28, 2012, 01:36:10 pmThe chemistry isn't exactly the same as CR123A is lithium manganese dioxide (3 V) and the AA cells are lithium iron disulfide (1.5 V).Most of the reports of exploding CR123A cells are for sub-standard Chinese cells. Few if any failure reports exist for high quality name brand cells.I would think that Energizer or EverReady AA lithium cells count as name brand and probably have a low risk of failure. In the US Energizer is the only brand of lithium AA available due to patent protections and litigation. I presume the EverReady brand is found in Australia?The cells do contain metallic lithium though, so caution is still appropriate.