How to Replace Dead Batteries in a Cordless Vacuum Cleaner
Cordless vacuums are powered by the energy stored in onboard batteries, and as long as the batteries are going on strong, so does the vacuum.
However, after some time, batteries lose their capacity, and they are unable to provide strong enough current. When that happens, cordless vacuums can't operate as long and as strong as they used to - it is time to replace the batteries or get a new cordless vacuum.
Updated: January 12, 2023.
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Intro to Cordless Vacuum Batteries
Cordless vacuums come either with a replaceable battery or with a fixed battery.
If You have a model with a replaceable battery that is showing signs of aging that is out of its warranty period, simply order a new OEM battery, and that's all.
However, if your model doesn't have a replaceable battery, but the battery is failing, while the rest of the unit is in perfect working order (and the warranty period is gone a long time ago), You can either take/send a unit to a repair shop and let them replace the batteries for You, or you can replace the battery by yourself.
Or, you can recycle your old cordless unit and buy one with a replaceable battery.
Note: It is highly recommended to let professionals either replace the battery or recycle the whole unit. Whatever You do with your unit, it is your responsibility and with lithium batteries being able to store and release large amounts of energy quickly, they are not something to play with ...
When replacing old batteries, be sure to replace old batteries with new batteries that have the same or better features than old batteries - but they must be of the same chemistry.
Cordless Vacuum Battery Chemistries
The most common battery chemistry types often found in modern cordless vacuums are Nickel Metal Hydride (NiMH) and Lithium-Ion batteries, although some older models are still using Nickel Cadmium (NiCd) batteries.
Nickel Cadmium (NiCd) Batteries
NiCd batteries are found in older and cheaper models, and since they contain cadmium, a very toxic heavy metal, they are being phased out in favor of Nickel Metal Hydride (NiMH) batteries.
In general, NiCd batteries feature a nominal voltage of 1.2V per cell, very low internal resistance, and are able to provide very large currents.
But they also feature a very strong memory effect, have a rather strong self-discharge rate, and support a relatively low number of charging and recharging cycles.
As the NiCd battery is being discharged, its output power decreases - it is not a power fade-free battery type. Also, NiCd batteries MUST be recharged using battery chargers intended for such batteries.
Fortunately, most brands (all?) have switched from NiCd to NiMH and Li-Ion batteries.
Nickel Metal Hydride (NiMH) Batteries
Nickel Metal Hydride (NiMH) batteries also feature 1.2V per cell, but they don't contain toxic heavy metals and are environment-friendly batteries.
Also, modern Nickel Metal Hydride (NiMH) batteries feature no memory effect, have a very low self-discharge rate, and support hundreds of recharging cycles, with some models supporting up to 1500-2000 recharging cycles.
As the NiMH batteries are being discharged, their output power slowly decreases - they are not a power fade-free battery type, but this power drop is not very significant. Also, NiMH batteries MUST be recharged using battery chargers intended for these batteries.
Nickel Metal Hydride (NiMH) batteries are reliable and affordable batteries, but their energy density is lower than the energy density of rechargeable lithium batteries.
Lithium IMR, INR, IFR, or ICR Batteries
Rechargeable lithium-ion batteries are lightweight batteries that are able to store large amounts of energy and release it when required.
However, lithium rechargeable batteries are sensitive to charging and discharging conditions and come in several similar chemistries, that also differ in a few very important details.
For example, lithium-ion battery labels often include abbreviations like IMR, INR, IFR, or ICR - these abbreviations describe actual battery chemistry:
- IMR rechargeable lithium batteries feature LiMn204 (Lithium Manganese Oxide) chemistry. Their nominal voltage is 3.6 - 3.7V per cell, with a maximum recommended charging voltage of 4.2V. IMR batteries commonly have a smaller capacity but are capable of delivering strong currents.
- INR rechargeable lithium batteries feature LiNiMnCoO2 (Lithium Manganese Nickel) chemistry. These batteries are very similar to IMR batteries since they can provide strong currents with slightly lower capacity.
- IFR rechargeable lithium batteries feature LiFePO4 (Lithium Iron Phosphate) chemistry. Their nominal voltage is 3.2V per cell, with the maximum recommended charging voltage of 3.5 - 3.6 V.
- ICR rechargeable lithium batteries feature LiCoO2 (Lithium Cobalt Oxide) chemistry. Their nominal voltage is 3.6 - 3.7V per cell, with the maximum recommended charging voltage of 4.2V. They commonly have higher capacities, but maximum allowed currents are often limited to just a few C.
Note: there are other chemistries on the market, too, including hybrid technologies like Lithium Nickel Cobalt Oxide (LiNiCoO2), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2), etc.
To achieve performances that are very close to or even better than some corded models, Dyson and a few other brands are using high-capacity Lithium Nickel Cobalt Aluminum Oxide and similar batteries and achieve very strong suction power - Dyson V11 Outsize 220 Air Watts, Dyson V15 Detect 230 Air Watts.
All lithium rechargeable batteries MUST have a built-in Battery Management System (BMS) that protects the battery from unwanted events like low/high voltage, low/high temperature, high current, short circuit, and similar.
Also, all lithium rechargeable batteries MUST be recharged with the battery chargers intended for such batteries - or they can overheat, catch fire and even explode!
Lithium Iron Phosphate (LiFePO4) batteries are the safest lithium battery chemistry, but they are not so common in high-discharge applications. Also, their nominal voltage is 3.2 volts, while other lithium chemistries have a nominal voltage of 3.6-3.7 volts.
Obviously, if your cordless unit is using 3.2-volt batteries, don't replace them with 3.6-volt batteries and vice versa - these batteries can easily overheat, catch fire, and even explode. Seriously.
Standard Battery Sizes
Some brands offer their cordless vacuums with detachable battery packs that fit only that particular model - such detachable battery packs feature non-standard dimensions and should be ordered as OEM battery packs.
But, if You plan on replacing individual battery cells, the most common standard battery sizes are cylindrical batteries with dimensions of (D x H):
- AA batteries: 14.5 x 50.5 mm
- RCR123A batteries: 17 x 34.5 mm,
- Sub-C batteries: 22.2 x 42.9 mm,
- C-Cell batteries: 26.2 x 50.0 mm,
- 18650 batteries: 18 x 65.2 mm,
- 26650 batteries: 26.5 x 65.4 mm, etc.
But, with so many standard battery sizes, other sizes are often used as well.
How to Replace the Batteries in Cordless Vacuum at Home
If You have an old cordless vacuum cleaner that is out of warranty and it doesn't have a replaceable battery, and it is too expensive to replace the battery at a repair shop, perhaps You can replace the batteries yourself and give your old cordless vacuum a few more years of service.
First of all, whatever You do, it is your own responsibility - if You are not 100% sure what You are doing, recycle your old cordless vacuum and get a new one. Seriously.
Note: The author of this article has a Master's Degree in Electronics with a strong background in math, physics, and chemistry, with a decades-long habit of disassembling and (usually) assembling tools, toys, devices, appliances, etc.
When replacing the old batteries with new ones, there are several important details to consider: battery chemistry, the size and the number of the batteries, their capacity, maximum charging/discharging current, the presence of the Battery Management System (BMS), and similar.
In this example, I will replace batteries in an older Electrolux convertible 2-in-1 stick/handheld vacuum, which is very similar to Electrolux EL3020A UltraPower Studio.
Again - should You decide to replace the batteries on your own, it is your own responsibility if something goes wrong...
Detach the handheld vacuum from the rest of the unit and locate the positions of the screws - also, check what kind of screwdriver they require.
Very often, units with non-replaceable parts, batteries in this case, come with awkward-looking, non-standard screw heads - is it deliberate in order to prevent people from opening the devices or not, I don't know.
After opening, clean the dust and try to locate all required parts while taking notes (and/or photos). As one can see, this model uses batteries without built-in BMS, but the BMS is present in the form of a controller board.
This Electrolux cordless vacuum uses three lithium batteries with a nominal voltage of 10.8 volts (3 x 3.6 volts = 10.8 volts) - so it is NOT using 3.2V Lithium Iron Phosphate (LiFePO4) batteries.
Now, gently pull out and take apart (but don't break any connections!) the motor, battery pack, and battery controller.
And this is the battery, one of three lithium 3.6 volts high-discharge 18650 batteries with soldering tabs.
Now, take the blank sheet of paper and draw a wiring diagram while at the same time adding labels to all three batteries - no photos here since this activity is highly specific.
Also, if You can't label it on your own, please, do yourself a favor and take the unit to some vacuum repair shop or get another unit.
After some googling around, I have found out that these LG batteries don't have built-in BMS, can come with or without soldering tabs, feature a nominal capacity of 'only' 1500 mAh, but they are able to provide 20+ Amps constantly (15+ C discharge current).
Since the new vacuum was able to operate for 10+ minutes, it means that the new batteries must have a capacity of at least 1500 mAh and a maximum constant discharge current of 6+ C.
Note: low-discharge 18650 batteries feature nominal capacity in the 3500-5000 mAh range, but they often can't support more than 1-2C constant discharge currents. Such batteries will die very soon in high-discharge applications, despite their initially higher capacity.
When new batteries arrive (may be ordered from online shops and with fast delivery, they may arrive within 24-72 hours), remove (desolder the tabs) the first old battery, and attach (solder) the first new battery. After that, do the same with the second and third old/new batteries - this is the safest way of replacing old batteries with new ones while avoiding mistakes.
Note: before soldering new 18650 batteries, it is a good practice to recharge and equalize them first using a smart lithium battery charger.
Now, return the batteries and other parts to their original position and assemble the unit which is ready for the first cleaning task.
Note: this unit features the label Li-21 suggesting that it comes with ~21V lithium battery - no, it is not, it is just good marketing :) but it still vacuums well...
Cordless Vacuum Batteries Frequently Asked Questions - Batteries' FAQ
Here are some of the most common Frequently Asked Questions about cordless vacuums and their batteries.
How long do cordless vacuum batteries last?
If the battery is recharged as recommended by the manufacturer, NiMH and Li-Ion batteries may withstand at least several hundred charging cycles when the battery is discharged fully each time.
If the battery is not discharged completely each time, the number of discharging/recharging cycles may be much higher.
Note: modern NiMH and lithium batteries don't suffer from the memory effect, so there is no need to discharge them completely almost every time.
Also, some models allow, and some even recommend the users to leave their batteries (or units) connected to the battery chargers, while some models require users to detach the battery charger when the charging is done - check the Owner's Guide and act according to the manufacturer's recommendations.
Can cordless vacuum batteries be replaced?
Yes, they can. Is it worth it, is it a smart thing to do, that is another story. If Your vacuum has a detachable battery that is showing signs of age, replace it with a new one.
Can you replace the battery in the Black and Decker cordless vacuum?
This depends on the model, but if the battery is not detachable, replacing the battery in a repair shop is recommended. Or recycle your old vacuum and get a new one, preferably one with a detachable battery.
What is the best battery-operated vacuum?
This is hard to say since "the best" one depends on individual needs and preferences.
But, Dyson, Shark, and Tineco offer excellent units which are anything but cheap - what You pay is what You get.
Also, other brands are also manufacturing very fine units that often come at very acceptable prices.
Which cordless stick vacuum lasts the longest?
One with a detachable battery and several spare ones. Seriously, most cordless stick vacuums have so-called Eco Suction Mode with lower suction strength but also the longest runtime - such Eco Suction Modes are good for everyday cleaning but are often unable to pick up anything heavier than dust and papers.
When looking for a cordless stick vacuum, go for the unit with a preferably detachable battery that features a runtime of at least 10-15 minutes in so-called Standard or even Max. Suction Modes.
My Hoover is not accepting charge, and the battery doesn't last much?
In that case, either the battery died, or the battery charger is not charging it properly.
If You have another battery that is being charged using the same charger and that battery is working properly, then it is a problem with the battery.
How do you fix a cordless vacuum that is not charging?
Read the Owner's Guide and if that doesn't help, take the unit to the repair shop.
But, it is also a good idea to check the battery contacts, battery voltage (voltmeter or multimeter are required), check the battery charger and its output voltage, check issues with electrical contacts and similar.
Why does my Black and Decker hand vacuum keep shutting off?
It is either the battery or battery charger, or there is a clog of some kind preventing the airflow ... again, check the Owner's Guide for probable causes of such behavior.
If possible, check the output voltage of the battery charger and the voltage of the battery after the automatic shut-off - if there is enough charge in the battery, check the vacuum for clogs or blockages, which can decrease the suction of the vacuum, causing motor thermal protection to shut off the vacuum.
How long do Lithium batteries last in vacuum cleaners?
If treated properly, at least a few hundred charges, with some models supporting 1000+ charging cycles or 2-5 years of almost everyday use.
In most cases, one may expect 300-500 full battery charging/discharging cycles - although lithium batteries cycle very well, it is a good practice not to discharge them completely every time.
Why is my Black and Decker battery not charging?
There is some issue with the battery, battery charger, or contacts.
Check the voltages of the battery and battery charger, and check the contacts between the battery and the charger and charger and the wall power outlet.
If this doesn't help, please, check the Owner's Guide for exact troubleshooting procedures.
How do I know if my Dyson battery needs replacing?
If the battery doesn't last as long as usual, then it is time to replace the battery. Of course, check the unit for other potential causes, like clogs, blockages, dirty air filters, etc.
How to replace the batteries in Shark cordless vacuum?
If the battery is detachable, get a new one. If the battery is not detachable, take the unit to the repair shop.
Why isn't my Dyson holding a charge?
The battery is probably (almost) dead, or the charger is gone, or there are issues with the contacts. Check the Owner's Guide for exact troubleshooting tips.
If You have two batteries and one is working properly, and another one is not, then it is the battery - replace the battery if it is within the warranty period, and if not, get the new one.
Few Final Words
If You are looking for a new cordless vacuum cleaner, if possible, go for the unit that features a detachable battery - such batteries may be replaced by simply ordering the new one, without the need of taking/sending the unit to a repair shop or disassembling it at home (at your own risk).
When looking for a new cordless vacuum cleaner, always choose according to your own needs and personal requirements.
And when replacing dead batteries, it is the best practice to take the unit to the repair shop and let them do the job or get a new one. But, if you know what you are doing, you can replace dead batteries on your own, be sure to use batteries with exactly the same chemistry and the same or better features.
Of course, too good new batteries (larger capacity, lower internal resistance) may overload the original battery charger too much, causing it to fail, but that is whole another story ...