I made a UPS with (2) 12v batteries connected in parallel with a handful of small devices (router, modem, HDD) connected at all times.
Once a day I would like to charge this unit using a 7 stage automatic charger:
http://www.vmaxtanks.com/assets/images/technical%20info%20folder/manual-BC1215.jpg
Since there are devices that constantly draw small amounts of power, the charger never finishes charging. It stays on stage 3 and never gets to the end.
What would be the best way to handle charging where disconnecting devices from battery is not an option?
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\$\begingroup\$ I smell some xy problem. Why exactly do you want to charge them with this charger and not let the UPS do what it was designed for? \$\endgroup\$– PlasmaHHCommented Dec 15, 2014 at 11:55
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\$\begingroup\$ I dont have to use this charger but this is the one I have at the moment. Most automatic chargers have stages that are similar so I just used this as an example. \$\endgroup\$– t qCommented Dec 15, 2014 at 15:48
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1\$\begingroup\$ If I understand correctly, I have a similar arrangement. I have a 12V battery, an inverter, and a battery charger. The inverter runs at all times. The charger runs as long as utility power is available. However, the load is small enough that the charger terminates and enters float stage. Every few days it re-initiates the charge cycle. I forget why it does this, but it is documented in the manual. Maybe supposed to prevent sulfation or something. The first charger I tried did not terminate, and kept going back to bulk charging. The battery can run the load for around 24 hours. \$\endgroup\$– user57037Commented Dec 15, 2014 at 18:32
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1\$\begingroup\$ A conventional, all-in-on UPS consists of a battery charger, an inverter, and an AC transfer switch. When the grid is available, the battery is disconnected from the load, charged if needed, and grid power is passed directly from the grid to the load. When grid power fails, or becomes shaky, this is instantly detected, and the inverter is activated, and the transfer switch disconnects grid power. This happens fast enough that the load never realizes there was a power loss. Sounds like @tq is running from battery continuously, so it is not like a normal UPS. \$\endgroup\$– user57037Commented Dec 15, 2014 at 18:41
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1\$\begingroup\$ I see what you mean, The part that probably wasn't so clear was that i'm charging this once a day so its not a true "UPS". \$\endgroup\$– t qCommented Dec 16, 2014 at 3:28
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1 Answer
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you should make a circuit which will switch off the batteries from the devices while your adapter is charging the batteries. Instead of using the batteries current to power the devices use the current of the charger to power the devices.
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\$\begingroup\$ thank you, can you point me in a direction where i can get started with this? \$\endgroup\$– t qCommented Mar 18, 2015 at 17:14