If you own an UPS (Uninterruptible Power Supply) to power devices while a power failure, you sure know time is running to safely shutdown your devices. For this reason i prefer using low-power and embedded devices which don't consume that much power so are able to run longer while the outage. According to my power-meter the sum of all devices (with modems, switches and a mini-itx server) is at about 70W. My current UPS is an APC BE500GR what according to it's battery specification is just enough to run for about 20 minutes in my situation. Never compared that directly when i bought it but actually it works for less than about 10 minutes, sure the battery suffered already after one-two years usage. Recently a friend called me, talking about his company trashing 16 sealed lead-acid rechargeable batteries, if i might be interested. Even if they might not work at all, i must give it a try i thought, to use them all toghether with my UPS.

First check what voltage the original shipped battery has.

original shipped battery has 13.25V


My voltmeter shows 13.25V so i went ahead to check the others. After checking all 16 batteries i noticed none of them has more than about 5V but most of them stable, just two batteries have a huge voltage drop. Then just daisychain enough together to get the needed voltage i thought, but that didn't work as expected. Maybe they need to be recharged? The UPS didn't accept any of them when i tried them one-by-one instead the original battery.




Even when applying load (like a fan), we've got more than 12V with those daisychained batteries. [picture missing] Next i would like to recharge them but i don't own a suitable charger for 12V lead-acid batteries. Just an AccuManager10 for AA/AAA NiMH 1,2V batteries, what i highly recommend but isn't taking me any further in this situation.

Then a friend told me about the Schumacher XM1-5 automatic battery charger which "maintains both 6 and 12 volt batteries keeping them at full charge using float-mode monitoring". From it's manual the intersting part:

If you’ve connected everything correctly, the AC POWER LED will be lit indicating the charger has power, the CONNECTED LED will be lit indicating the battery is properly connected and the CHARGING LED will be lit indicating that the charger is charging. If any of these LEDs are not lit, check the connections at the battery and AC source or have the battery checked/replaced.
NOTE: This charger is equipped with an auto-start feature. It will not supply current to the battery clips until a battery is properly connected and the CONNECTED LED is lit. Unlike traditional chargers, the clips will not spark if touched together.
Aborted Charge: If charging can not be completed normally, charging will abort. When charging aborts, the charger’s output is shut off, and the CHARGING LED will flash. To reset after an aborted charge, either disconnect the battery or unplug the charger.
Completion of Charge: Charge completion is indicated by the CHARGED LED. When lit, the charger has stopped charging and switched to the Maintain Mode of operation. 
Maintain Mode (Float-Mode Monitoring): When the CHARGED LED is lit, the charger has started Maintain Mode. In this mode, the charger keeps the battery fully charged by delivering a small current when necessary. If the charger has to provide its maximum maintain current for a continuous 12 hour period, it will go into Abort Mode (see Aborted Charge section). This is usually caused by a drain on the battery or the battery could be bad. Make sure there are no loads on the battery. If there are, remove them. If there are none, have the battery checked or replaced.

The specifications just say "Charger Type: Fully Automatic Microprocessor Controlled" and "Output Voltage: 6V/12VDC - Output Current Cont: 1.5A"Hopefully it is able to "refresh" and recharge those batteries. We'll see it if the "CONNECTED LED" will be lit.

[article work in progress]


Another interesting things about batteries: