Electronics > Power/Renewable Energy/EV's

10 year old rechargeable acid battery

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Rick Law:
The risk is typically not during discharge (assuming your connections and your load are safe).  The risk is during application of maintenance float or drip charge (or regular high-current fast charge) when something goes wrong.

When one has a charger plug into the wall with power on and battery connected, real danger can occur.  So I do "unattended charge" only for batteries in good condition.   When in doubt, I monitor charging very closely.

EDIT: decided to remove details about how some of my charging failed.  My equipment is likely different than others so how my charge fail doesn't really matter.

floobydust:
During float charging, a common SLA failure is for a cell to short. You've now got a 10V battery and a charger will go high current and roast the other cells in the battery, until they dry out. It makes a lot of heat, I see batteries bulged out and leaked (especially in UPS but this might be from high-rate discharge through a bad cell).
So float charging is not entirely safe.

vinlove:

--- Quote from: Rick Law on March 23, 2023, 12:17:00 am ---The risk is typically not during discharge (assuming your connections and your load are safe).  The risk is during application of maintenance float or drip charge (or regular high-current fast charge) when something goes wrong.

When one has a charger plug into the wall with power on and battery connected, real danger can occur.  So I do "unattended charge" only for batteries in good condition.   When in doubt, I monitor charging very closely.

EDIT: decided to remove details about how some of my charging failed.  My equipment is likely different than others so how my charge fail doesn't really matter.

--- End quote ---

Got you.  Yes I know what you mean.   I was under impression possible danger during recharging only happens with the SLA batteries of poor physical condition such as bulging casing or leaking from the casing.  Of course SLA batteries in that shape or condition must be discarded immediately.
But the ones I have are in clean solid condition without any trace of leak anywhere.  So I have tried revive them, but I can conclude that it is impossible to revive them into fully the original state.  That seems the definite impossibility.  But it could be revived into some sort of reduced capacity such as my old SLA batteries seem quite happy getting recharged for about 20 hours, and intermittent float recharging.  When it is recharged, it runs at about 12.5V, and it can power very light current drawing devices such as the Active Antennas = it can run for hours and hours before the battery goes under 11V which need recharging.  This is still something than nothing.

Because I am running my shortwave receiver with a new Lithium power bank which outputs 12V via cigarette socket and a few 5V for USB recharging (This power bank was quite expensive at about £70).   When both sw receiver and active antenna are connected to the power bank, it goes flat very quick.  When the active antenna is powered by the old SLA battery, it runs for hours and hours.  So it is still doing some good for my use.   If it shows any sign of degrading in the output, recharging or the shape of the SLA battery casing, it will be discarded there and then.

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