Start with what the light is doing. Completely dark usually points at the supply side: outlet, cable or the charger itself. Flashing red, or a light that never turns green, usually points at the battery side: poor contact, a deeply discharged pack, age, or temperature. Steady green means either full or an empty bay on standby. Colour conventions are not standardised across brands, so treat this as the common pattern and your own manual as the authority. The checking order stays the same: supply first, then contact, then the pack.
Common Indicator States
| Light | Usual meaning | Check first |
|---|---|---|
| No light at all | No power | Outlet, cable, charger plug seated properly |
| Steady red | Charging (constant current / constant voltage) | Nothing — wait for it to turn green |
| Flashing red | Poor contact, pack fault, or over temperature | Reseat the pack, clean contacts, let it cool |
| Steady green | Full, or standby with no pack fitted | Confirm the pack is actually in the bay |
| Alternating red and green | Abnormal voltage or pack not identified | Fit a different pack to see which is at fault |
| Flashes once, then goes dark | Protection trip or internal fault | Test with another outlet and another pack |
One trap worth knowing: some chargers show green before any pack is fitted, which is standby, not “full”. To confirm charging is really happening, check whether the pack warms slightly after a while, or watch for the colour to change.
No Light: Three Supply Checks
- Outlet: try a socket you know is live, or plug a phone charger into the same one. Ruled out the socket and any switched strip in one go.
- Cable: with a detachable mains lead or USB cable, swap in one you know works. Loose connectors and broken inner cores are common.
- Charger: look for scorch marks, smell or bent prongs, then fit a different pack. On a multi-bay unit, try another bay — if one bay stays dark while the rest work, that bay is the fault.
Flashing Red or Never Going Green: Four Battery Checks
- Reseat it: take the pack out, confirm orientation, push it fully home, and put it back. Not seated properly is the most common cause by a distance.
- Clean the contacts: wipe the pack terminals and the charger springs with a dry soft cloth, or rub lightly with a pencil eraser, to remove oxide, sweat and dust.
- Correct the temperature: a pack just in from the cold, or one already hot on charge, can trip protection. Let it sit at room temperature for ten minutes or so and try again; heat limits are in charging heat and safety limits.
- Compare with another pack: fit one you know is good. If that charges normally, the original pack is the problem — deeply discharged or aged. If the new one flashes too, it is the charger.
A pack left in storage long enough to self-discharge deeply may be refused outright. If there is still no response after a few minutes of a flashing light, retire the pack rather than coax it.
Green Light, but the Pack Is Empty
That means the charger is not seeing a load, and the usual reason is no contact: bent springs, a pack not pushed home, film or dirt on the terminals. Press lightly on the pack to see whether contact is made, or measure the voltage with a multimeter if you have one. If other packs charge fine in the same unit, the terminals on that one pack are the issue.
When to Replace the Charger
- Still completely dark after you have swapped outlet, cable and pack.
- One bay permanently dead while the others work.
- Hot shell, smell or noise during charging.
- Fill times that are wildly off, or packs that come off “full” and die quickly.
When replacing, make sure the charger actually matches the pack spec; the buying criteria are in how to choose an NP-FZ100 charger. If the pack itself will not take a charge either, work through the seven-step charging fault checklist.
Good Everyday Habits
- Charge on a ventilated, hard, flat surface. Not a bed, not a camera bag.
- Wait for green before pulling the pack. Do not keep interrupting the cycle.
- Store long-term at roughly 40–60% charge and top up every three months.
- Pack the charger and cable separately when travelling, so the prongs do not get bent.
- Leave space between packs on a multi-bay charger so heat does not stack.
FAQ
Red never turns green, even after hours
Check whether the pack is unusually hot first. If it is merely slow, a large pack on a low-current charger will take its time. If it is several times the normal duration and the pack is clearly hot, cut power and try a different charger.
Green with no pack, red once I fit one — normal?
Normal. Red means charging has started. Once it goes green, the pack is ready to use.
The light blinks a few times and goes out
Usually a protection trip. Take the pack out, check the shell for swelling, clean the contacts and retry. If it keeps happening, stop using that pack.
Can I mix charger and battery brands?
Physically, a matching form factor usually works, but pick products with clearly stated specs that are designed for the pack. Matching voltage and connector is the minimum requirement.
Rather than decoding an old charger’s light language, use a matched kit. YO’s NP-FZ100 compatible battery is rated around 2280mAh / 7.2V / 16.4Wh: about $17.89 for a single pack, about $22.93 for one battery with a charger and about $36.74 for two batteries with a charger — the charger effectively adds roughly $5, which is hard to beat shopping for one separately. The TNP-FZ100 is the 2400mAh / roughly 17.3Wh version. Restocking in volume goes through wholesale enquiry, where orders over 100 units are quoted per batch.