# Battery confusion: Is the Devterm specifically designed for unprotected cells? **URL:** \ **Category:** DevTerm\ **Created:** [April 17, 2022, 6:54pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317 "2022-04-17T18:54:50Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![supercom32](https://avatars.discourse-cdn.com/v4/letter/s/eb8c5e/32.png) [@supercom32](https://forum.clockworkpi.com/u/supercom32)\ **Post date:** [April 17, 2022, 6:54pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/1 "2022-04-17T18:54:50Z")
Hi there, So In purchasing a set of protected batteries, I noted that it does fit inside the DevTerm, however because the battery diameter is slightly larger than what the cover supports, the battery door does close, but causes the entire back case to slightly bow, meaning the shell starts to separate from the front housing on the top of the unit (the plastic tab no longer catches the faceplate). So my question is, was the DevTerm specifically designed for unprotected batteries, which mostly fit inside the DevTerm fine without pushing the size limit of the battery compartment? Or is using such batteries unstafe (even if being left in the device all the time - On/off/charging)? ---
**Author:** ![Eugene](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/eugene/32/5685_2.png) [@Eugene](https://forum.clockworkpi.com/u/Eugene)\ **Post date:** [April 17, 2022, 8:30pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/2 "2022-04-17T20:30:20Z")
> [@supercom32](#): > > So my question is, was the DevTerm specifically designed for unprotected batteries, which mostly fit inside the DevTerm fine without pushing the size limit of the battery compartment? Or is using such batteries unstafe (even if being left in the device all the time - On/off/charging)? Take a look at the product page on the main site: > [@](#): > > We carefully designed the battery holder to make it more compatible with various 18650 battery sizes: Φ18±0.5mm diameter, 65-69mm length. The battery module has “Short Circuit and Reverse Polarity Protection” features, but you are still advised to purchase\* the batteries from a reliable distributor and install them correctly It can work without battery protection, but based on that wording it would seem they still recommend it. There are a variety of 18650s that have built-in protection that will fit. You just have to shop very carefully to get the right size. ---
**Author:** ![Eugene](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/eugene/32/5685_2.png) [@Eugene](https://forum.clockworkpi.com/u/Eugene)\ **Post date:** [April 17, 2022, 8:33pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/3 "2022-04-17T20:33:36Z")
Just for an example, I’m using [Samsung 35E 18650 3500mAh 8A - Protected](https://www.18650batterystore.com/products/samsung-35e-protected) batteries. They fit without any bowing/deformation of the chassis. They are very snug, but have showed no problems in 4 days of semi-frequent use (2-4 hours per day). They have been charged once per day. ---
**Author:** ![supercom32](https://avatars.discourse-cdn.com/v4/letter/s/eb8c5e/32.png) [@supercom32](https://forum.clockworkpi.com/u/supercom32)\ **Post date:** [April 19, 2022, 2:33pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/4 "2022-04-19T14:33:39Z")
Thanks. It would be nice if we had a sticky containing a definitive list of batteries (confirmed by users) which list if: - There are no issues. - Barely fits, but requires pry tool to remove batteries. - Fits, but diameter causes case/battery cover issues. Or at least some resource which isn’t scattered across multiple threads. For my contribution I’ll say: NCR18650B ([Panasonic NCR18650B Button Top Battery — FlashlightWorld](https://www.flashlightworld.ca/products/panasonic-ncr-18650b-3400mah-4-9a-protected-button-top-battery)) = Very tight (requires pry tool), battery cover can be forced close, but will cause case bowing. ---
**Author:** ![Eugene](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/eugene/32/5685_2.png) [@Eugene](https://forum.clockworkpi.com/u/Eugene)\ **Post date:** [April 19, 2022, 3:34pm UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/5 "2022-04-19T15:34:53Z")
> [@supercom32](#): > > Thanks. It would be nice if we had a sticky containing a definitive list of batteries (confirmed by users) Not a sticky, but there’s this great thread: > [@Battery model recommendation](https://forum.clockworkpi.com/t/battery-model-recommendation/6611): > > Hello About battery: could we have an exact model recommandation ? The one that would be the best capacity, perfect fit, safe, easily ordered on any website… Thanks you ---
**Author:** ![dkirchge](https://avatars.discourse-cdn.com/v4/letter/d/ecccb3/32.png) [@dkirchge](https://forum.clockworkpi.com/u/dkirchge)\ **Post date:** [April 22, 2022, 2:56am UTC](https://forum.clockworkpi.com/t/battery-confusion-is-the-devterm-specifically-designed-for-unprotected-cells/8317/6 "2022-04-22T02:56:28Z")
For what it’s worth, I’m using 2 Nitecore 3.7V 3200mAh cells in mine and they fit perfectly.