About UPS connection to the garage door - Page 1
Forum section: electronics / general

author: mtn1543
author_rank: Newbie
timestamp: November 01, 2023, 02:27:32 pm
content: Hello everyone, the garage door of our apartment has a 9.6 V 1600mAh ni-mh battery in its box for power outages, but this battery can open and close the door about 3 times during a power outage. In addition, the garage door has a separate 12V 0.6 A remote control receiver, which is fed by a 12V 1.3 A UPS. What I am thinking of doing is to remove the garage door battery, draw a line from the 12V UPS, reduce this 12Volt to 9.6 Volts with a DC-DC 3A converter, connect a 6A diode to the + section, and then plug it into the battery input. The purpose of installing a diode is to prevent current flow from the garage door battery socket to the UPS. What do you think of this idea? I tried to explain it with a diagram, I hope it is understandable.https://i.hizliresim.com/rpe5xyd.png

author: tom66
author_rank: Super Contributor
timestamp: November 01, 2023, 02:36:52 pm
content: The only issue I can foresee is what if the UPS can't supply enough current to open the door? The 1.6Ah battery being exhausted after 3 times, suggests each opening/closing uses 530mAh (1600mAh / 3). If it takes 60 seconds to open and close (I'm assuming it's slower than when on mains power), then the peak current works out to be 31 amps! Realistically the current is probably somewhere around half to a third of this due to Peukert's law (high currents exhaust batteries quicker than otherwise expected) but either way you need to make sure that the UPS can support that demand without shutting down.One method that might work would be to have the DC-DC converter shut off when the garage door operation was in process, allowing the battery to support the motor entirely. Then the DC-DC converter would charge the battery during the 'downtime', through a proper charger.Adding a series resistor on the output of the DC-DC converter may allow it to trickle charge the battery but be careful, the resistor value needs to be -very- small (current well under 0.1C) to avoid overcharging the battery. A proper Ni-MH charger is necessary otherwise. You cannot connect the output of the DC-DC converter directly to the battery. How does the garage door system charge the battery currently? I would guess it is trickle charging it because that is cheap and power cuts are normally rare.

author: mtn1543
author_rank: Newbie
timestamp: November 01, 2023, 03:06:49 pm
content: It is true, but I will replace the existing UPS battery with a 12V-7Ah UPS Type Battery. Additionally, the garage door's Ni-MH battery only charges in 36 hours. (This is the 3rd new battery).That's why I thought of this system.

author: tom66
author_rank: Super Contributor
timestamp: November 01, 2023, 03:19:14 pm
content: Quote from: mtn1543 on November 01, 2023, 03:06:49 pmThe capacity of the battery is not necessarily a factor here if the UPS has a current limiter or fuse built into it. Also, your DC-DC converter needs to be able to handle the full operating current of the motor. First step is to measure the motor current. I suspect it is very high.36 hours recharge time seems about right for trickle charging. (Less than 1/10C charge rate.) Probably the battery is being damaged by the high current, if it is frequently used in power cuts. Are they common in Turkey?

author: mtn1543
author_rank: Newbie
timestamp: November 01, 2023, 04:03:26 pm
content: Thank you, I will measure the motor current first. Meanwhile, I looked at the engine. It is a 24V DC motor and the user manual states that it draws 5W in standby and 600W when operating. No, there is no power outage. Maybe only once every 2-3 years. But I am the apartment manager and according to the apartment security rule, the garage door must work with the recovery battery in case of a power outage, but the current battery only opens and closes the door 2-3 times. If it is turned on and off 10-11 times with a single battery, it will not be a problem for me. Perhaps it would be most logical to switch to a generator system.

author: tom66
author_rank: Super Contributor
timestamp: November 01, 2023, 04:36:37 pm
content: Perhaps an alternative solution is to find a very big 9.6V NiMH battery to replace the one that is currently used. It will then perhaps be able to run longer in an outage, and probably will have better reliability as it won't be deep-cycled quite as much when the door does need to open. Something like a 5000mAh 9.6V battery may work better.