I found myself in the some weird situation with the Hitachi battery. The charger only flashes red and refused to give charge to the battery..
The fast blinking of the red light on the charger shows that the battery system signals a problem. In this state, it simply does not try to charge the package. It only stays there, flashing endlessly.
Really frustrating, when you have strict deadlines to finish work.
How to Revive a Hitachi 18V Battery When the Charger Flashes Fast Red
I removed the old battery package from the charger and turned it to look more closely. Below are those terminal contacts, where the battery connects to the charger and my tools. Some serve for energy, others for data, for instance, to send info about the health of the battery and the status of the charge back to the charger.
When the voltage falls too low or the cells go out of balance, the protective circuits step in, and the charger does not touch it.
The main step is to find another Hitachi battery in good condition that has the same voltage level as the broken one. Later, you can carefully use the energy of the healthy package to restart the protection circuit in the bad one and restore to it the ability to charge. Be close to the positive and negative terminal, check the labels to ensure the right direction before making connections.
Only don't skip something, the secret is to find that right moment, where the good battery gives to the bad only the needed starting push.
I took two pieces of wire with ring connections connected on the ends. That improved the connection compared to using clip or bare wires, the rings ensured firm hold on the terminal without sliding. I checked that the wires were long enough to cover the distance between the two battery side by side.
It worked perfectly.
When the two battery placed together, I took the wire with the ring connection and insert one end to the positive terminal of the good battery. Later, I connect to the another end of the positive terminal of the broken battery.
So I went slowly, first connecting the negative terminals carefully. I had to control that the wires do not touch places where they should not. Apparently, it was enough to hook it for around fifteen seconds.
Not to fully reset, but to give enough voltage level to restart the protection circuit. If the wires smoke or get hot, pull them out right away. Burning the batteries would be a disaster.
It seemed to work, at least according to the readings of the meter later. One step closer to keeping that issue under control and working.
After disconnecting the wires from the terminals of the batteries, I saw that the broken battery still had low voltage level.
Even so, the protective circuit should be restarting, so I thought that the best way to check is to compare the two packages directly. Interestingly, both were marked as 18V lithium-ion models, fit for 14.4V and 18V tools of Hitachi.
The problem battery had a date of production in 2017, so it was a bit old, but not ancient by any measure.
I put the supposedly revived battery in the charger and watched with held breath. Really, the light changed from fast blinking to steady red glow. The charge started, finally, after all those efforts.
I crossed fingers that it keeps going.
That red light showed that the charger finally did its task and pumped energy into the battery. The protective circuit of the battery blocked all attempts to charge before. But after the jump start with another battery, the circuit decided that it is safe to let the charger in.Leaving the old battery in the charger for some hours seemed to work.
Later, the light show solid green, showing full charge. I decided to try it in my tools, and it works well as ever. Not bad for a quick homejob!The protective circuit of the battery sometimes triggers when it should not.
When the package sits unused for long time or fully drains, the voltage can drop below the minimum limit.Not all battery packages can be revived, that is true. Worth trying before writing it off, for sure.
