There may be potential damage to chargers or USB-C batteries Caused by 3-in-1 charging Cables:
When a 3-in-1 charging cable is connected to a QC/PD or other fast-charging adapter, and any of the Lightning, Type-C, or Micro interfaces is plugged into a fast-charging device (such as a smartphone or tablet), the protocol will be recognized and fast charging will be initiated. The unused interfaces will also remain in a high-voltage output state. If a 5V device (such as VC2, ET1, BC4, USB-C battery, etc.) is connected to these unused ports, it may result in overvoltage damage.
Example:
If a QC3.0 adapter is connected to a 3-in-1 charging cable, and an iPhone is plugged into the Lightning port, the following issues may occur:
Connecting an AA 1.5V battery to the Type-C port may cause the positive terminal of the battery to overheat and melt.
Connecting a BC4 charger may result in the LED indicator becoming excessively bright before it burns out and remains permanently lit.
Connecting an ET1 charger to the Micro port may cause the LCD to become excessively bright, followed by a black screen, rendering the device inoperable and unable to charge.
Thanks for the warning, but I think anyone who does anything that stupid (connecting anything to that charging cable except the batteries they were made for) kinda ‘deserves’ what is coming their way… just my opinion tho…
To try and avoid that, you could print a label in red attached to the cable saying, “don’t use for ANYTHING except charging the XTar batteries it came with”, would have more chance of being seen and prevent disaster, than a post in a forum (even one as nice and popular as BLF). Again, just my opinion…
I think this is THE way to avoid an issue as described in the OP.
When formulating not doing a specific action you always have a chance that people get (stupid) ideas they didn’t have before.
Like don’t dry your wet toy poodle in the microwave oven.
The same happens with many USB power supplies with multiple ports. If one connected device negotiates a higher voltage, the other ports receive the same voltage because all of them are in parallel.
I don’t even understand the original post, so I guess I deserve some sort of punishment?
The 3 in 1 cable Xtar is talking about is a generic cable, no? So it would be logical to assume you can plug anything USB-C related into the other “arms” while charging an e.g. cellphone, else what is the point of the “splitter cable”?
And if one connected device did negotiate a higher voltage, you would not know that, unless you had a mini voltmeter connected between the USB power supply output and the input of the multi-output USB cable in use.
I plead guilty, but I suggest that almost no-one - other than a few of us types around here would (have the mini voltmeter). So I’m not sure about the deserving what you get bit - and think XTAR’s warning is useful.
I agree. I understand what the problem is, but had never really thought abut it. But I don’t remember having any of these multi connector splitter cables. I use USB charging hubs that have ports that individually negotiate power delivery. But I do think the problem is something that people should be aware of. I tend to think that the reason Xtar reported the issue is that they have themselves gotten reports , or saw in testing, the over voltages.
Huh, I have always thought these split cables contain nothing but the two power lines. If some of them have a CC line and can facilitate voltage negotiation, that’s a bad design for sure.
I can’t imagine somebody thinks that they would be able to fast charge their phone and have enough power to do other things at the same time.
But some people may not really know all the differences and whether or not their phone is “fast” charging. And I’m quite sure most don’t really know that when their phone is fast charging it can be at different voltages. They likely understand that it is “more power”.
If you have a need for multiple cables I can understand why some people would potentially use a multi-cable thingy with one somewhat powerful charger.
Most people know visually what a type A USB port is or a type C or an iPhone port or plug. But they don’t necessarily know what the proper name for those ports are.
There are more information about refreshing NiMH batteries, how it works, its benefits, and when and how to use it effectively on xtar L4 PRO charger.
Frequently Asked Questions (FAQ) as below:
1. Is the refresh function mainly for eliminating memory effect?
The memory effect was a major issue with Ni-Cd (Nickel-Cadmium) batteries, but modern NiMH AA batteries have greatly improved in this regard. The refresh function is primarily designed to correct capacity deviations and rebalance the battery after extended use, rather than specifically addressing memory effect.
2. If memory effect is no longer a big problem, do I still need to refresh my batteries?
Yes, even though memory effect is not a major concern for NiMH batteries, long-term use can still cause imbalances in battery performance, leading to a phenomenon called “false capacity.” The refresh function helps correct these deviations through a scientifically controlled discharge-recharge cycle, restoring some lost capacity and improving battery life in your devices.
Additionally, different brands and qualities of NiMH batteries vary in their susceptibility to capacity loss, meaning the need for refreshing depends on the specific battery model and usage conditions.
3. Do all types of NiMH batteries require refreshing?
Not all NiMH batteries require frequent refreshing.
Low self-discharge (LSD) batteries, such as Eneloop, have a more stable internal chemical structure, meaning they require less frequent refresh cycles.
High-capacity NiMH batteries, however, tend to degrade faster due to their heavier usage, so they may benefit from regular refreshing.
Users should determine the need for refreshing based on actual battery performance and usage patterns.
4. Can the refresh function damage AA batteries?
No, a well-designed refresh function will not damage batteries. For example, the XTAR L4 PRO smart charger carefully regulates the refresh process:
It does not fully discharge the battery to a dangerous level.
It avoids overcharging, ensuring safe and effective battery maintenance.
This precise control ensures that refreshing helps maintain battery performance without causing harm.
5. How often should I refresh my NiMH batteries?
The frequency depends on how often the batteries are used and their performance over time. If you notice a significant drop in runtime or unstable battery behavior, it’s a good time to perform a refresh cycle.
6. Can I use the refresh function on over-discharged batteries?
Yes, but only if the charger has a smart detection system. The XTAR L4 PRO charger, for example, can automatically detect over-discharged batteries and take the following steps:
Step1: If a battery is over-discharged, the charger will first activate a gentle charging mode to revive it.
Step2: Once reactivated, the charger will fully charge the battery before entering refresh mode.
Step3: The refresh cycle will then discharge and recharge the battery in proper times to restore its optimal performance.
If a battery is too heavily degraded and fails to recover after multiple refresh cycles, it may be time to replace it.
【Updated】 Keep Your Charger Contacts Clean for Reliable Charging
Recently, we got some feedback from a customer about his L4 charger. He told his charger sometimes failed to charge, or the red charging light stayed on for a long time. To find ou the problem, we carefully examined his returned L4 charger.
Upon inspection, we found that the positive contact of the charger had dirt and debris stuck on it, preventing proper contact between the batteries and the charger’s positive terminals. After cleaning the contact points, multiple cycles of battery charging and aging tests returned normal results.
To avoid such charging issues, there are some suggestions:
Please keep both battery and charger contacts clean. Dirt or residue on the positive or negative terminals can block proper contact.
Persistent dirt may damage the charger plating. Over time, stuck debris may even damage the metal plating, which is hard to restore.
If you experience similar issues, you can check and clean the contact points yourself, try to resolve the problem.
【Updated】 Your Charger Sometimes Show “Insufficient Charging Current”, Why?
Some customers asked why their charger doesn’t always charge at the rated max current for their 18650/21700 batteries. In fact, charging current is not determined by the charger alone. It’s the result of multiple safety and technical factors working together.
1. Battery Status
When the charger input meets the required specifications, the actual charging current is mainly affected by:
Battery internal resistance
Battery voltage level
Battery protection circuit parameters
If any of these factors trigger safety limits, the charger will automatically reduce the current to protect the battery.
2. Three-Stage Lithium-Ion Charging (TC–CC–CV)
XTAR chargers follow the standard TC–CC–CV charging method, which means the charging current changes at different stages:
TC (Trickle Charge)
When battery voltage is below 3.0V, the charger uses a very small current to safely wake up and protect the battery.
CC (Constant Current)
Once voltage rises above 3.0V, the charger enters fast charging, typically up to 0.5C.
CV (Constant Voltage) When battery voltage reaches 4.2V, the charger switches to constant voltage mode and gradually reduces current. This means low current at the beginning or near full charge is normal behavior, not a malfunction.
3. Internal Resistance Directly Affects Charging Current
The chargers also dynamically adjust charging current based on the measured internal resistance of the battery. Such as, charging a 18650 battery with different IR on xtar VX4:
0–39 mΩ → 3A
40–59 mΩ → 2A
60–79 mΩ → 1A
80–119 mΩ → 0.5A
≥120 mΩ → 0.25A
As batteries age or degrade, internal resistance increases. To prevent overheating and ensure safety, the charger automatically lowers the current.
4. Battery Protection Circuits Also Matter
For protected batteries, the charging current may be limited by the protection board itself. Even if the charger is capable of higher current, the battery protection circuit may restrict it by design.
There are some tips:
Use a reliable adapter and good-quality cable rated for the needed current.
When cell voltage is below 3.0 V, allow the charger to complete the wake/trickle phase.
If protection-board aging or damage is suspected, replace the cell or consult the vendor for testing.
Record charger-displayed ESR/current info for support troubleshooting.
From components to finished products, every XTAR charger is designed, tested, and built with safety and reliability in mind.
This video shows how our chargers are designed, assembled, tested, and delivered. From performance and safety testing to strict quality control at every stage, we focus on the details that truly matter. They are exactly what ensure our chargers remain safe, reliable, and efficient in real-world use.
【Updated】XTAR Battery & Charger Manufacturing and Testing Process
We often see discussions about battery safety, charger reliability, grading standards… As a manufacturer focused on batteries and smart chargers, we’d like to share how XTAR batteries and chargers are manufactured and tested before reaching users.
Below is an overview of our battery and charger manufacturing & testing workflow.
【Updated】 Why Do the “Fully Charged” AA Batteries Not Show 100% on the Devices?
We recently received the feedback from a custome. He used the BC8 charger to charge his AA batteries and notice something interesting. He got the XTAR 1.5V 4150mWh AA Li-ion batteries and IKEA 1.2V NiMH batteries fully charged in the BC8. Then he put the batteries in his device, while found the device showed 97% charge with XTAR 1.5V 4150mWh AA batteries; 80–90% charge with IKEA NiMH 1.2V batteries. So why weren’t they showing 100%?
In fact, some devices estimate battery charger percentage based on the batteries’ voltage level. Those electronic devices are designed to support multiple types of batteries, such as Alkaline, 1.5V Li-ion, 1.2V NiMH AA. These different batteries have different full-charge voltages. If the device uses alkaline batteries as its standard, it may show different charge level with other battery types. The percentage reading would simply be a voltage interpretation issue, not a charging problem.
Here’s what typically happens:
Alkaline AA (new): around 1.60V
→ Device reads this as 100%
XTAR 1.5V 4150mWh Li-ion AA (fully charged): 1.5V
→ Slightly lower than alkaline
→ Device may show around 95–98%
NiMH 1.2V AA (fully charged): around 1.40–1.45V
→ Much lower than alkaline
→ Device may show 80–90%
Indeed. I have some older radios that actually had a switch so that I can select that I am using either Alkaline or NiMH/Nicad so that the battery indicator stays more accurate.
【Updated】 Avoid Charging Lithium Batteries in Low Temperatures
For safe and reliable charging of your Lithium batteries, it’s suggested to charge them around 10°C to 30°C (50°F to 86°F), and avoid charging below 0°C (32°F), as charging at low temperatures can significantly accelerate battery degradation and may even introduce safety risks.
This behavior is driven by the internal electrochemical mechanisms of lithium-ion cells.
*** Slower Lithium-Ion Diffusion**
At low temperatures, the electrolyte becomes more viscous and its ionic conductivity decreases. As a result, lithium-ion mobility is significantly reduced. During charging, lithium ions are unable to efficiently diffuse and intercalate into the graphite anode structure. This creates a bottleneck at the electrode surface.
*** Lithium Plating on the Anode**
When lithium ions cannot properly intercalate into the anode, they accumulate on the surface and are reduced into metallic lithium, a phenomenon known as Lithium Plating. This leads to several critical issues:
Permanent capacity loss, as metallic lithium cannot be reversibly cycled
Increased internal resistance
Potential formation of lithium dendrites, which may pierce the separator and cause internal short circuits
*** Instability of the SEI Layer**
Under low-temperature charging conditions, the electrochemical reactions become unstable. The SEI layer may repeatedly break down and reform. This process consumes active lithium and leads to accelerated capacity fading, and increased impedance and reduced efficiency.
*** Increased Polarization Effects**
Low temperatures also increase internal resistance, resulting in stronger electrochemical polarization. This causes artificially elevated charging voltage, premature charge cut-off before full capacity is reached. Such conditions further promote lithium plating, creating a compounding degradation effect.
To ensure optimal performance and longevity, pls kindly allow the Lithium batteries to return to ambient temperature.
