The by1 battery model name is written B-Y1 on the label, and the usual spare part listing gives the Vivo Y1s as its phone, with a pack of about 4030 mAh typical. The maker is Vivo. People type it as BY1, B Y1 or "vivo by1 battery", but they all mean the same code with a hyphen after the B. Listings do not all agree, so treat the phone name as the likely answer and the old label as the final one.
One trap is the letter Y. It does not mean the phone belongs to the Vivo Y series, and a Y phone does not automatically use a Y code. The two characters after the hyphen are only part of a part number. The code is printed on the pack itself, which a technician can read only after lifting the back of a sealed phone.
Quick facts
Step by step
Write down the exact phone name
Open Settings, tap About phone and note the name shown. If you cannot find it, type model in the Settings search bar.
Have the old label read by the technician
With the back open, look for
B-Y1on the sticker, beside the capacity and voltage. Ask for a photo of it before the pack is removed.Compare the new pack with the old one
The code, connector shape and size should match the old pack. Hold them together and check that the contacts line up.
Look at print and weight
Good print is sharp and carries batch details. A pack that feels clearly lighter than the old one is a bad sign.
Which phone uses the BY1 battery model name
A B followed by a hyphen is the pattern Vivo and iQOO use for their packs. That points to the maker group only. For B-Y1, the listings name one phone, the Vivo Y1s. Other Vivo phones of a similar size and age might share the pack, but there is no confirmation for any of them, so none is listed as a fit.
| Phone | Status | Note |
|---|---|---|
| Vivo Y1s | Named by the usual listings | About 4030 mAh typical; read the label |
| Other Vivo Y phones | Not confirmed | Do not assume a share from the phone name |
| Vivo phones with a different code | Different pack | Use the page for that code |
If your phone is not the Y1s, the old sticker decides. A B-Y1 code read off the cell in your hand outweighs any list, this one included.
Rated and typical capacity of the B-Y1 pack
Advert copy and parts lists show 4030 mAh here, which is the usual typical rating. A pack sticker often carries a rated value that is a little lower. Check your own pack for that number, because nothing is confirmed for this code.
Watt hours tell you the energy a pack holds. A 4030 mAh B-Y1 at a typical 3.85 V stores about 15.5 Wh. For this pack the volts are not confirmed, so no energy figure is given on this page. If you want to compare two packs, read the volts on each label and work out the numbers on your own.
Do not judge a pack only by mAh. A replacement that claims far more than 4030 mAh in the same body is almost never honest, since the space inside the phone fixes the cell size.
Confirm the code before you order
Many wrong purchases start with a search for the phone name alone. Use these checks together:
- Get the phone name from About phone, then the code from the old sticker.
- Match all three details: code, capacity and connector.
- Ask for the code in writing, not just "for Y series".
A customer came in with a Y-series phone and asked for "the Y1 battery". The counter had a pack marked B-Y1 on the shelf, but the phone's own sticker read a different code. The pack stayed on the shelf, and the right one was ordered after the sticker was photographed.
The same method works for any other handset. Follow the guide on our finding your battery model name page.
Look-alike Vivo codes that get mixed up with B-Y1
Vivo codes are short, so a wrong glance is easy. Characters such as 1, I and 7, or G and 6, are hard to tell apart on faint print. Read the sticker in bright light.
- B-G7 has its own phone list and capacity, so never substitute it just because the length and first letter look alike.
- B-O5 is often typed as BO5 or B05, and the zero and the letter O cause the same kind of slip.
- B-W1 shares its last digit with B-Y1 but is a separate pack.
Equal capacity on two packs says nothing about size or connector, and a pack with another code can be wrong for your phone. Every family member is listed on the Vivo battery list.
Signs a B-Y1 pack is wearing out
| Symptom | Why it happens | Sensible move |
|---|---|---|
| Level jumps down in big steps | Aged cell that resists current flow | Check how healthy the battery is before you decide on a replacement |
| Phone dies with charge still shown | Cell cannot give short bursts of power | Ask a counter to load test the pack |
| Y1s back gaps or screen edge lifts | B-Y1 has puffed up | Unplug the charger and go to a service centre |
| Feels warm while idle | A background app that keeps running, or a faulty battery | Restart, remove the cover, and watch for a repeat |
An older phone drains faster for many reasons besides the cell. Read why a battery drains fast and use the battery health check before you spend money.
Never charge a bulging, leaking or very hot battery, and never squeeze, bend or stab it. Rest the phone on a hard, cool surface and let a service centre handle it. Replacement packs with an inflated mAh label are widely sold, so accept only one whose printed code is the same as your old sticker.
Getting a new pack fitted safely
Glue seals the Y1s body. It is wise to let an authorised service centre or a trusted repair person open it. Prising the Y1s back with a blade risks slicing the cell or tearing the display ribbon.
Tell them your phone name and request that they compare the B-Y1 sticker on the old pack with the new one. Once the replacement is in your hand, inspect it before the phone is closed:
- Weight close to the old pack.
- Print that is sharp, with batch details.
- No capacity claim far above the original.
Read mobile battery replacement for the steps in more detail.
After the job, use the phone until it is low and then charge it fully with its own charger. Note how long that first day lasts so you can compare later.
Daily care for an older Vivo pack
A phone of this age has already seen many charge cycles, so heat is your main enemy. Keep it away from strong sunlight, not on a mattress while charging, and out of a tight case when it feels warm.
Use the original charger or one of equal or lower watts. If the cable plug gets hot, change the cable. Real battery life depends on the chip, screen brightness, signal strength and apps, not only the mAh printed on the pack, so two Vivo phones with the same capacity can last different hours.
Frequently asked questions
Which phone has the by1 battery model name?
Parts sellers link B-Y1 with the Vivo Y1s and list around 4030 mAh as typical. Sellers do not always agree, so check the code printed on the sticker of your worn-out battery before you buy.
Is BY1 the same as B-Y1?
Yes. The label shows a hyphen after the B, and most people type it without one. Search it as B-Y1 or BY1 and you are looking for the same code.
How many mAh is a Vivo B-Y1 battery?
It is usually given as 4030 mAh typical. The rated value on the sticker can be a bit smaller, so check your own pack.
Does a Vivo phone with Y in its name use the Y code?
No. The letter in the code is part of a part number, not the phone series. Match the full code and the phone name instead.
Is it fine to fit a battery with a different code if the mAh matches?
Not safely. Same capacity does not mean same size or connector. Fit only the code that the old sticker shows.
How can I tell a weak B-Y1 copy?
Fake packs are often lighter, with smudged printing and no batch marks, yet they promise much more capacity than the real one. Place the two side by side and check.