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Description
BTI L77991-002-BTI 11.55V 56WHR LI-ION BATTERY 28Y92UC, L77991-002, HSTNN-DB90, L77991-005, L77622-2C1, L77622-2C2 ELITEBOOK 850 G7, ELITEBOOK 850 G8, ELITEBOOK 855 G7, ZBOOK FIREFLY 15 G8Power through demanding days with the BTI L77991 002 BTI 11. 55V 56Wh Li Ion battery. This 3 cell replacement battery is engineered for long lasting performance in HP EliteBook models, including the 850 G7, 850 G8, and 855 G7, as well as select ZBook configurations. Its designed to be a seamless, high quality OEM replacement option that delivers dependable run time, improved energy density, and reliable safety features. With a capacity of 56Wh and a
Power through demanding days with the BTI L77991-002-BTI 11.55V 56Wh Li-Ion battery. This 3-cell replacement battery is engineered for long-lasting performance in HP EliteBook models, including the 850 G7, 850 G8, and 855 G7, as well as select ZBook configurations. It’s designed to be a seamless, high-quality OEM-replacement option that delivers dependable run time, improved energy density, and reliable safety features. With a capacity of 56Wh and a nominal voltage of 11.55V, this BTI battery gives you the freedom to work, study, or create away from a power outlet without constant recharging. It also comes with an 18-month manufacture warranty in the USA, offering peace of mind alongside its powerful performance. While providing robust everyday power, it also emphasizes battery health and device safety through advanced protection mechanisms to guard against overcharge, short circuit, and overheating. If you’re seeking a dependable power solution that restores your laptop’s original endurance, the BTI L77991-002-BTI is a strong choice that combines compatibility, safety, and value in one package.
- Extended run time for HP EliteBook 850 G7/850 G8/855 G7 – 56Wh capacity delivers longer days between charges, so you can work, edit, and collaborate without frequent recharges.
- Direct compatibility with popular OEM part numbers – Replaces 28Y92UC, HSTNN-DB90, L77622-2C1, L77622-2C2, L77991-002, and L77991-005 for a seamless replacement that fits the original battery bay.
- 3-cell Li-Ion technology at 11.55V – Lightweight, efficient energy with solid thermal characteristics to maintain performance across many charge cycles.
- Designed for HP EliteBook and ZBook Firefly 15 G8 – Compatible with multiple premium laptops from HP’s business and creator lines, preserving mobility and productivity in the field or office.
- Safety and warranty you can trust – Includes built-in protections against overcharge, short circuit, and overheating, plus an 18-month USA warranty for added confidence in your purchase.
Technical Details of BTI L77991-002-BTI
- Model: BTI L77991-002-BTI
- Voltage: 11.55V
- Capacity: 56Wh
- Chemistry: Li-Ion
- Cells: 3-cell
- Replaces OEM numbers: 28Y92UC, HSTNN-DB90, L77622-2C1, L77622-2C2, L77991-002, L77991-005
- Compatible models: HP EliteBook 850 G7, 850 G8, 855 G7; ZBook Firefly 15 G8
- Warranty: 18 months (USA)
How to install BTI L77991-002-BTI Battery
- Power down the laptop and disconnect it from any power source before starting.
- Remove the bottom cover and locate the existing battery connection to the motherboard. Carefully disconnect the battery cable.
- Remove the old battery, insert the BTI L77991-002-BTI into the battery bay, ensuring the connector aligns with the socket, then reconnect the battery cable.
- Replace the bottom cover and secure all screws. Turn the device on to confirm proper operation and charge status.
Frequently asked questions
- Q: What devices is this BTI battery compatible with?
- A: It is compatible with HP EliteBook 850 G7, 850 G8, 855 G7 and select ZBook Firefly 15 G8 configurations, serving as a reliable OEM-replacement option for those models.
- Q: What is the capacity and voltage?
- A: The battery provides 56Wh of capacity at 11.55V, using a 3-cell Li-Ion configuration for a balanced mix of run time and weight.
- Q: Does this battery come with a warranty?
- A: Yes. It includes an 18-month manufacture warranty in the USA for added peace of mind.
- Q: What OEM numbers does this battery replace?
- A: It replaces multiple OEM part numbers including 28Y92UC, HSTNN-DB90, L77622-2C1, L77622-2C2, L77991-002, and L77991-005, providing broad compatibility as a direct replacement.
- Q: Is this battery safe and reliable?
- A: The BTI battery includes safety protections against overcharge, short circuit, and overheating to help safeguard your device during use and charging.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.4 ★★★★★
Based on 15 reviews
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Product Reviews
★★★★★ 3
Does help, but needs constant adjusting during walk
I watch so many Cesar television shows on how to correct dog behavior and see him use a Yellow version on the shows. I see there is not a yellow version of this lead available on the site so that was irritating because I wanted to get what he uses exactly from his show. Anyway, thanks to another reviewer, I knew to buy the "large" size of this for my 40lb dog because she made the mistake of buying the regular smaller size this site defaults to choose. The "large" is not very long, only 2 ft but maybe the rope is thicker.
The rope is a light stretchy material so it does not chafe your hand, but it still burns after a while of your dog pulling and you trying to keep it from pulling. I could not imagine trying to use this on a dog bigger than 40 pounds because it feels like it is at it's max strength when I am dealing with mine.
My dog likes to eat anything and everything on the ground as we walk so I needed this for the option of the muzzle control feature of the rope. As others have said it acts like the gentle leader halter.
Pros: The adjustable slide to "secure" the loop size over your dog's head, behind it's ears is easy to move up and down.
The black metal ring works well when you use the second circle to loop over your dog's muzzle. Every time she tries to open her mouth to eat something on the ground she can't.
CONS: The adjustable slide to "secure" the loop is too easy to move and therefore I have to constantly push it back down on my dog's head while walking. I am trying to find a clamp of some sort I can clip behind this slider to keep it in place once my dog starts moving.
As soon as it begins to slide up from movement, causing the neck hoop opening to widen and she is back to pulling hard.
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Reviewed in the United States on November 7, 2022
★★★★★ 5
Such a great tool!
Size: 48" One Size Fits Most, Color: Black
I have had this product for a week, and I have nothing but good things to say about it! I debated for a couple of days as to whether or not to purchase it because the price seemed a tiny bit much for what looked like such a simple item. Now I know it’s that very same simplicity that makes this such an effective tool! Best money I could have spent on my dog!
I’ve had my rescue Patterdale Terrier for a little under 3 months and I have quickly found out he is far from being perfect. It has taken a lot of time to begin working on correcting some of his problems, one at a time. Like many dogs, he also pulls when being walked. So what did I do as a regular person in need of quick dog tips? I searched up Cesar Millan videos on YouTube. 😂
I had purchased a Flexi leash two weeks after adopting my dog, and he broke it within another two weeks. While it was disappointing when I first found out, I now see it as a blessing in disguise. Paying close attention on YouTube, I noticed common features in all of the videos where the owners had pulling problems. Most owners in these videos had Flexi leashes, and the dog is always walking in front of the owner, not besides them. All Cesar uses to start making a change are leads just like this one. He never explicitly promotes his lead on his show, but after seeing the immediate increased control using such a simple tool, I decided to look online and found this. So I figured, why not?
My dog is 28lbs, so he isn’t big enough to overpower and drag me during a walk. After the Flexi broke, I resorted to using a regular hook-through-the-collar leash. The pulling problem was still there, and would only get worst if we came across a squirrel. As soon as we started using this lead, he’s become much more responsive to my corrections. As soon as he is too far in front of me, even without actually pulling, I give it a quick, gentle tug and a “Chh!” and he‘s learned that he needs to slow down. If he actually pulls and won’t immediately respond to my correction, we’ll sometimes stop walking altogether until he sits, calms down, and realizes that we’ll only walk at my pace. This lead has helped tremendously and there’s rarely ever any tension on the lead when walking now. It’s hard to believe it has only been a week since I’ve started using it, and I don’t believe I’ll go back to using the traditional leash unless absolutely necessary. I would definitely purchase this again!
And no, I have not been paid by anyone, nor was I sent this by any company to review it. Just a regular girl who is so happy to have found something that is actually seeming to work!
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Reviewed in the United States on August 4, 2018
★★★★★ 5
Worked from day 1
Size: 48" One Size Fits Most, Color: Black
This leash is the best thing I’ve ever bought for my dog. He’s 1 year and 4 months old, and I’ve bought at least five different harnesses since I got him, including very expensive ones like DogfriendlyCo. He pulls with every single one of them.
I bought this leash a while ago, but I only used it once because I was afraid he would get hyperactive and choke himself. He hated it at first and tried really hard to get out of it. Today, after four months, I decided to give it another try and omg! This is the first time I’ve been able to walk him without feeling anxious or embarrassed. He walked by my side the whole time, and the leash stayed loose. Iwould only pull a little when he wanted to go ahead of me. I could tell he enjoyed the walk and so did I.
I’ve tried it a couple more times just to make sure it wasn’t luck, but this thing really works. Highly recommend.
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Reviewed in the United States on May 23, 2026
★★★★★ 5
Only “tough” toy my Doberman loves!
Pattern Name: Octopus
Not indestructible, but last a good long while. Definitely worth the money and lasts longer than any other plush toys we’ve had (which is all my dog will play with). It’s for sure my Dobermans favorite, I’ve ordered probably 10 at this point. He gets the stuffing out after a month or two and we open a new one. He’s picky with toys, either destroys them or ignores them, but he never gets bored with his octopus! 🐙 He sneaks one outside once in a while and the neighbor’s dogs steal it. They love it too and thankfully can’t destroy before I retrieve it.
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Reviewed in the United States on December 22, 2025
★★★★★ 5
Great for a Pitball
Pattern Name: Octopus
I have a Pitbull and she absolutely loves this toy. I always wait a while before giving a review. She has had this toy Since the beginning of July and she is still playing with this toy. It does have little holes but it is still going. She loves it. Playing tug of war with her. I also take it and wrap it around her collar and watch her dance around trying to get it out(I don't leave it there long). This a great buy. I also bought and extra one so when this one does finally dies she will have another. The material is strong, The sound is about normal for a squeaky toy.
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Reviewed in the United States on December 30, 2025