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[Solved] Yuasa Lead-Acid Battery Swelling and Cracking: Possible Causes and Discussion

hostipl 23232 16
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Why did a 3-year-old lead-acid backup battery swell and crack, and what should be checked before replacing it?

The thread points most strongly to overcharging: a buffer/backup battery should not be held above 13.7 V, because too high a charging voltage can make it swell and crack. Before installing a new battery, measure the charging voltage and charging current; the suggested buffer voltage is 13.5–13.7 V [#17753871][#17753639] One reply also notes that this is not normal wear for a used battery and likely indicates a charging error rather than ordinary aging [#17756389] Freezing was mentioned as a possible cause only if the battery were fully discharged and exposed to very low temperatures, but that was considered unlikely here because the battery was in a heated room [#17753871]
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  • #1 17753618
    hostipl
    Level 2  
    Posts: 4
    Rate: 1
    Hi
    I have such a problem. Please advise.

    I used a Yuasa lead-acid battery. he was about 3 years old
    It was connected as a support for the alarm system in a single-family house.
    I didn't see him for several months.
    Recently, after checking, it turned out that the battery swelled up to such an extent that the housing cracked (photo).

    I'm quite a beginner in this topic, so I'm curious if this behavior of the battery happens? What could be the reason?
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  • #2 17753635
    stanislaw1954
    Level 43  
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    If it is due to frost, discharged and kept in a room with a minus temperature, then it froze and burst.
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    #3 17753639
    kot mirmur
    Level 33  
    Posts: 2131
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    It happens. It would be good to measure the charging voltage before connecting a new one. On the old one you have the values of this voltage.
  • #4 17753640
    leonov
    Level 43  
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    hostipl wrote:
    What could be the reason?
    E.g. low temperature and freezing of the electrolyte.
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    #5 17753724
    keseszel
    Level 26  
    Posts: 4090
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    Before connecting a new one - measure the charging voltage and charging current. It is often the case that the electrolyte can disappear - gas, be poured out, for example, during improper storage. The charging current increases, there is stronger gassing, the vapors cannot escape and boom..
    Interesting fact - the battery in the car, dark plastic, sealed plugs. I unscrewed the charger when charging and ... the electrolyte was uneven in the cells. I topped up with distilled water to the level that seemed right to me, but I'll buy something to measure the density anyway..
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    #6 17753725
    _jta_
    Electronics specialist  
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    Something like this happened to me, without minus temperatures, with a battery from another company (although a slightly different shape of swelling and cracks). It was still under warranty, they exchanged the whole set for Yuas without saying anything. But the inside of the UPS from corrosion after the spill of acid was cleaned for a long time and laboriously by myself.
  • #7 17753728
    Boryc2014
    Level 20  
    Posts: 464
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    The battery should not freeze in the cold. The cell inside just went and, unfortunately, the battery had to be replaced.
  • #8 17753734
    hostipl
    Level 2  
    Posts: 4
    Rate: 1
    I would rather avoid frost
    the battery was in a heated room, near the radiator, which ran all winter
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  • #9 17753735
    Boryc2014
    Level 20  
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    I forgot to add that it's possible that it could have frozen but if it was used well, it shouldn't.

    Added after 52 [seconds]:

    And if it stood in the heat, then, as I wrote, one of the cells was damaged and unfortunately there is no help for it.
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  • #10 17753772
    SKM 1964
    Level 34  
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    It looks like it fell from a great height. Alternatively, a short circuit occurred in the cell and hydrogen exploded. :|
  • #11 17753787
    Boryc2014
    Level 20  
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    All that's left to do is replace it with a new one. Unfortunately
  • #12 17753837
    kot mirmur
    Level 33  
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    Gentlemen, stop pouring water - what freezing, what explosions when there is a short circuit in the cell, and adding anything to this battery is physically impossible - unless someone removes the factory protections. There is an electrolyte in the form of a gel anyway. There is nothing to argue here, just put on a new one. Measure the charging voltage and current and that's it.
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    #13 17753871
    ^ToM^
    Level 42  
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    hostipl wrote:
    What could be the reason?


    A classic of the genre.
    The battery has swelled from too high hold-up voltage. The backup (buffer) voltage cannot be higher than 13.7 V. If it is higher, the battery will swell from overcharging.
    A common phenomenon in UPSs when the charging voltage is not set precisely enough, or something breaks down in the power supply. I received such power supplies where in order to remove the swollen batteries, the frame of the power supply had to be cut with a flex knife or the welds drilled out.

    A fully charged battery will not freeze, even partially, because the freezing point of the battery is minus several dozen °C. The only possibility is that it will freeze as it is discharged to ZERO and instead of the electrolyte there is only water. However, this is not the case here, because the battery was in a heated room.

    Even a completely discharged battery freezes somewhere around -10 °C.
    Yuasa Lead-Acid Battery Swelling and Cracking: Possible Causes and Discussionaku.jpg (8.53 kB)You must be logged in to download this attachment.

    Before installing a new battery, check the charging voltage. Must be 13.5-13.7 volts.
  • #14 17756269
    mariuz2
    Level 19  
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    It died of old age, it's not a specific brand to last 10 years.
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    #15 17756389
    ^ToM^
    Level 42  
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    mariuz2 wrote:
    He died of old age, it's not a specific brand that would last 10 years.


    The most respectable, well-known and reputable brand founded 100 years ago in Japan. It has also been producing batteries for a very long time. A global tycoon, products known all over the world and of excellent quality.
    That's on the margin.
    But back to the merits. This is not normal battery wear. There was some error in charging, probably, because normally used batteries from old age do not look like this.
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  • #16 17756651
    hostipl
    Level 2  
    Posts: 4
    Rate: 1
    Thank you very much everyone for your help.
    Everything I needed I already know.
  • #17 17756654
    hostipl
    Level 2  
    Posts: 4
    Rate: 1
    Thank you very much everyone for your help.
    Everything I needed I already know.

    Added after 1 [minutes]:

    Thanks for your help, valuable information.
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Topic summary

✨ The discussion revolves around a Yuasa lead-acid battery that swelled and cracked after three years of use in an alarm system. Possible causes for this issue include exposure to low temperatures leading to freezing of the electrolyte, overcharging due to high hold-up voltage, and general battery aging. Users suggest measuring the charging voltage and current before replacing the battery, as improper storage and maintenance can lead to electrolyte loss and increased gassing. Some participants share personal experiences with similar battery failures, emphasizing the importance of proper charging practices. Ultimately, the consensus is that the battery needs replacement due to damage, and preventive measures should be taken for future use.
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FAQ

TL;DR: Most swollen/cracked Yuasa SLA batteries trace to overcharge; float above 13.8 V. "Overcharging will cause corrosion and gassing." Check float 13.5–13.8 V, move away from heat, and replace safely. [“BU-403: Charging Lead Acid”]

Why it matters: This FAQ helps homeowners, alarm/UPS users, and techs stop repeat SLA failures, avoid hazards, and set chargers correctly.

Quick Facts

  • 12 V VRLA float/backup spec: 13.5–13.8 V at 20–25°C (2.25–2.30 V/cell) [“Yuasa NP Series Technical Manual”]
  • Temperature compensation (float): approx. −3 mV/°C per cell from 25°C [“BU-403: Charging Lead Acid”]
  • Freezing point depends on state of charge: ~−60°C full, ~−10°C discharged [“BU-502: Discharging at Low Temperatures”]
  • Yuasa NP7-12 design life: 3–5 years at 20–25°C in standby use [“Yuasa NP7-12 Data Sheet”]
  • VRLA are sealed; do not open or add water; replace if damaged [“Yuasa NP Series Technical Manual”]

Why did my Yuasa battery swell or crack while on an alarm system?

Overcharge and heat are the top causes. Excess float voltage drives electrolysis, generating gas that inflates the case. That stresses seams and can crack the housing. Heat near a radiator accelerates failure and amplifies gassing. Fix the charger settings and replace the battery. “Overcharging will cause corrosion and gassing.” [“BU-403: Charging Lead Acid”]

What float/backup voltage should I set for a 12 V Yuasa in an alarm or UPS?

Set float to 13.5–13.8 V at 25°C (2.25–2.30 V/cell). Yuasa specifies: “Recommended float voltage is 2.275 V/cell at 20°C.” For cooler rooms, increase slightly with temperature compensation. For warmer rooms, decrease accordingly. Use a calibrated DMM and verify at the battery terminals. [“Yuasa NP Series Technical Manual”]

How do I check if my charger is overcharging?

  1. Disconnect system loads so the charger operates in float mode.
  2. Measure DC at the battery terminals; expect 13.5–13.8 V at 25°C.
  3. If voltage exceeds spec, adjust or replace the charger and enable temperature compensation. [“Yuasa NP Series Technical Manual”]

Could freezing have caused the bulge if the battery was indoors?

Freezing is unlikely indoors. A fully charged lead‑acid battery freezes around −60°C. A fully discharged unit can freeze near −10°C. Near a radiator, neither condition applies. Swelling from overcharge is the more plausible cause here. [“BU-502: Discharging at Low Temperatures”]

Can I add distilled water or open a Yuasa sealed (VRLA/AGM/gel) battery?

No. VRLA batteries are sealed gas‑recombination designs. Opening caps or adding water defeats safety valves and degrades performance. Replace the battery instead of attempting electrolyte maintenance. Follow the manufacturer’s “do not add water” guidance. [“Yuasa NP Series Technical Manual”]

Does placing the battery near a radiator or warm equipment matter?

Yes. Elevated temperature accelerates aging and raises gassing. As a rule of thumb, every 10°C above 25°C roughly halves service life. Relocate batteries away from heat sources and improve ventilation to extend life. [“BU-808: How to Prolong Battery Life”]

When should I replace a standby Yuasa battery?

Yuasa NP7‑12 has a 3–5 year design life at 20–25°C. For alarms or UPS, plan preventive replacement around that window. Replace sooner if capacity no longer supports the required backup time. [“Yuasa NP7-12 Data Sheet”]

What charge current is safe for small 7–12 Ah VRLA batteries?

Use a constant‑voltage charger with current limiting. A typical safe range is 0.1–0.3C. For 7 Ah, that’s about 0.7–2.1 A. Lower current improves longevity in standby service. Verify correct float voltage to prevent overcharge. [“BU-403: Charging Lead Acid”]

Could a single bad cell cause a “boom” or case crack?

An internal short can create rapid gas generation during charging. VRLA batteries include pressure‑relief valves to prevent rupture. If vents are obstructed or charging occurs in a sealed enclosure, hydrogen can accumulate and ignite. Treat this as an edge case and ensure ventilation. [“Panasonic VRLA Application Handbook”]

What did the forum recommend before installing a new battery?

Measure the charger’s float voltage and current. “Before installing a new battery, check the charging voltage. Must be 13.5–13.7 volts.” Correct settings prevent repeat swelling and early failure. [Elektroda, ^ToM^, post #17753871]

My battery is ~3 years old—did it just die of age?

A reputable brand’s battery can age out, but bulging is not normal end‑of‑life. An expert in the thread notes this looks like a charging error rather than simple aging. Correct the charger and replace the battery. [Elektroda, ^ToM^, post #17756389]

How do I dispose of a swollen or cracked SLA battery safely?

Do not put it in household trash. Lead‑acid batteries must go to authorized recycling or retailer take‑back programs. Store upright in a leak‑proof container and avoid contact with any electrolyte. Follow local transport and drop‑off rules. [“EPA: Used Lead-Acid Battery Recycling”]
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