Swollen Battery? – How to Check Your Hotspot, Prolong Battery Life & Battery Replacement Guide

Over time, exposure to heat can cause your more expensive devices - such as smartphones and MiFi/Jetpacks - to start to have issues. Electronics, in general, don't like heat, and many come with fail safes that shut them off if there are sustained higher temperatures. Try leaving your smartphone on a hot dashboard in the baking sun sometime (or, actually, don't...  just trust us on this.)

One common problem reported with mobile electronics is batteries swelling in mobile hotspot devices such as Jetpacks and MiFis.

Thankfully, many mobile hotspots have a user replaceable battery, so the damage is not permanent or expensive to repair.  However, if your battery is aging and swelling, it could at best case cause your hotspot to shut down or shorten how long your battery keeps a charge. At worst, it could start a fire.

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Things that can cause battery swelling

After a device has been out for about a year and in heavy use is when we start to receive reports of battery swelling becoming a problem. In particular, the Pantech MHS291L (the former "Millenicom" Verizon hotspot) and the newer Netgear AC791L have been suspect. But no mobile hotspot device is exempt.

Here are some usage habits that tend to cause battery swelling due to a combination of internal charging mechanisms and exposure to prolonged heat:

  • Frequent use in a cradle style booster
  • Frequent poor signal areas (devices go into full transmit power to keep a signal)
  • Keeping your device plugged in non-stop (many don't work without the battery inserted)
  • Lack of ventilation
  • Leaving devices in a sunny spot
  • General battery aging

How to Check Your Battery

We recommend you check your battery often in any mobile hotspot device, especially as they age. (Note, in tech terms - a year old is probably considered "middle age".)

Periodically take the battery out of the device by popping the back cover off the hotspot, preferably after a period of high usage. Some have notches for prying the cover off, others might need a digging fingernail underneath the cover.

Feel the battery for any excess heat. If it's hot to touch, it is overheating.

Visually look it over. Look for splits or cracks in the case (a metallic line may be showing), like in this AC791L battery:

In this case, the battery had reached failure and shut our hotspot down even while plugged in.

Sit it flat on a table. If it no longer sits flat on a table without a slight wobble, you are developing a problem:

This battery didn't completely fail, but it was bulging!

You should start seeking out a replacement battery as soon as possible.


Prolonging Battery Life

To play it safe, do not leave a mobile hotspot plugged in when it is not actively in use.

To add battery longevity, it's also a good idea to periodically unplug your device and run it off battery for a bit - even getting it down to a full drain.

Providing ventilation for cooling is always a good idea. And if you're using a cradle style booster, providing an air gap can increase ventilation (see below for more).

And, keeping a solid strong cellular signal can also reduce how hard your mobile hotspot has to work to keep online. Using external antennas and / or boosters can help prolong your battery life by keeping heat down.


The Fix: Replace Your Battery

Thankfully, with regular inspection, it's fairly easy to stay ahead of any real problems with battery swelling. We recommend having a spare new battery ready to swap in before your device shuts down and leaves you offline. But, you can also usually source a new battery fairly quickly.

There are options for most mobile hotspots direct from the manufacturers (called "OEM") or cheaper off-brand options. Please note that listing generic non-OEM batteries is in no way an endorsement on our part that these are quality batteries. Be sure to read plenty of reviews before going with an off-brand battery, as quality can vary quite a bit.

Battery Replacement Center (Links & Part Numbers)

Here is information that may help you find replacements batteries for some of the most popular mobile hotspots in use today.

Keep in mind that batteries may come in and out of stock, and options can change frequently. We have tried to list both OEM (original equipment by the manufacturer) and generic batteries found in popular stores like Amazon, eBay and Walmart.

We have also listed the battery part number - which can be helpful in using search engines to find possible replacements if any of the product links within are no longer working. You can usually track down replacement batteries by searching the web for the hotspot name, model number and/or battery part number.


Novatel/Inseego 7730L & 8830L - Battery Part #: 40123117

Released in January 2017, we are beginning to receive reports of battery swelling issues with the 7730L If you do experience issues, check to see if they might still be covered by Novatel's warranty.

The 8800L released in late October 2018 uses the same battery as the prior 7730L. Any issues in the first year should be covered by Novatel's warranty.

But if you need a replacement, here they are:


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Netgear AC791L - Battery Type: W-9

In mid-2017 we started to see an increase in reports of battery swelling on the AC791L, released in September 2015.


Amazon: OEM | Generic| Generic

6620L - Battery Part #: 40115131.01

We have not received too many reports of the Novatel 6620L battery having issues yet, despite this model being released in early 2014.

OEM | Beltron

Pantech MHS291L - Battery Part #: BTR291B

The Pantech MHS291L (aka the "Millenicom" hotspot) was released in early 2013, and within a year started having frequent issues with battery swelling - with some owners describing the situation as the device "eating through" batteries. As this is an older device very near being obsolete, we'd highly recommend an upgrade to a newer hotspot instead of investing in new batteries.

But... if you must:


Ellipsis MHL900L - Battery Part #: 342123180

We haven't had an reports of swelling in the Ellipsis MHL900L


Netgear Nighthawk  - Battery Part #: W-10

Released in October 2017, we have received only a couple of isolated reports on battery swelling issues. The MR1100 (M1) takes a W-10 battery. Being that the the device is so new, any issues with batteries should be covered under warranty.

If you need to replace the battery on your own, we are finding them listed on eBay, mostly shipping from China:



Velocity 2 MF923- Battery Part #: CS-ZMF923SL

Released in March of 2018, we have no reports of the Velocity 2 having battery swelling issues. Being that the the device is so new, any issues with batteries should be covered under warranty.


Unite Explore 815s - Battery Part #: W-9

Released in Summer 2016, we have limited reports of the Unite Explore having battery swelling issues. It takes the same battery type as the Netgear AC791L.

OEM | Generic| Generic

Unite Pro 781s - Battery Part #: W-6

We have started to receive sporadic reports of the Unite Pro, released in mid-2014, starting to have battery swelling issues.

OEM on NewEgg

Amazon: OEM | Generic

Wireless Internet Router (MF279)

AT&T's Wireless Internet Router is a hotspot with a phone jack. This update to AT&T's original 'Homebase' was released in November 2017. We have had no reports of battery swelling in this device.



ZTE 915 & 917: Battery Part #: Li3720T42P3h704572

We have not yet received reports of battery swelling in either the ZTE 915 or 917. Batteries can be a bit tough to track down.


Alcatel LinkZone - Battery Part #: TLiB5AF

We do not yet have reports of the LinkZone having battery issues.

OEM eBay (specifically mentions LinkZone)

Amazon OEM (same part #, but does not mention LinkZone) | Generic



ZTE Warp - No User Replaceable Battery!

Released in May of 2017 for Sprint Prepaid subsidiary Boost, there are massive reports of both battery swelling issues and even fires caused by the Warp.   This device was sent out by many of the Mobile Citizen based non-profit plans (PCs for People and Calyx) with a warning, and distribution has been halted.

Since this unit has no user replaceable battery - if you notice any signs of swelling, discontinue use IMMEDIATELY. For prolonged life, do not keep this unit plugged in 24/7 - allowing it to run off the battery. Heavy constant loads in poor signal areas can also contribute to swelling - which is a common use case for those on the non-profit plans.

Pocket WiFi -Battery Part #: Li3827t43p3h544780

We do not yet have reports of the Pocket WiFi having issues.


Franklin Wireless R910 - Battery Part #: V515176AR

The R910 was released in October 2017. We have had no reports of battery swelling.

OEM | Generic

Franklin Wireless R850 - Battery Part #: Franklin Wireless R850

We have had a couple of reports of this battery for the R850 showing signs of swelling.

Beltron | Generic

Netgear Fuse - Battery Part #: W-8

We do not yet have reports of the Fuse having battery issues.

OEM (eBay) | Walmart


Members, please update in the comments if you experience battery swelling on your mobile hotspot if we've not yet listed it as having problems.

On the MHS291L model, we had a daring member attempt to 'hack' their device to run without a battery. If anyone is brave enough to try this with other models, please do let us know! Instructions for a "no-battery" hack you can make out of an old distended battery.


Why Cradle Boosters Create so much Heat

When cradle boosters, like the weBoost 4G-S, are used in a vehicle, they are typically used for a few hours of driving around town or in-between cities on a road trip. The booster and your device are constantly being passed off between different towers and varying cellular signals, and the booster helps stabilize the signal.

When a booster is concentrating on a weaker signal, it produces a lot of heat to make that signal usable. While in motion, that concentration is temporary and there tends to be very little heat build up. When a stronger signal is found a mile or two down the road, the heat produced is not as much - so the booster has a chance to cool off.

A cradle booster with a JetPack, in use as intended.

A cradle booster with a JetPack, in use as intended.

However, when you're parked in one location, especially with a weaker signal, the booster can continue to produce a lot of heat and doesn't have a chance to cool off - this is how RVers tend to use cradle boosters differently than how they were designed. We might be parked in one locations for days or weeks, and the booster never gets a chance to cool off.

The cradle boosters are specifically designed to hold your device right up against the interior antenna, which is integrated into the amplifier (the part that gets hot) to get the strongest boost. This means your device is being directly exposed to the heat produced.

Other styles of booster have a paddle antenna several feet away from the amplifier (such as the 4G-X or 4G-M), so this isn't as much of a problem. Even if you're keeping your device on the antenna itself, it's the amplifier (or the box) that is generating the bulk of the heat.

Easy Trick to Prevent Damage

Thankfully, there is a super simple, low-tech prevention to help reduce your risk of running into problems.

Create an air gap between your device and the cradle booster antenna.

A piece of rubber places between the antenna and MiFi.

A piece of rubber placed between the antenna and MiFi.

This can be as simple as placing the device in at an angle, or placing something that won't melt or conduct energy in-between the antenna and device - such as a piece of rubber.

This creates a way for heat to dissipate and you still get a strong boost from the cradle booster. Your device just needs to be within a few inches of the antenna to get a strong, boosted signal.


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