Diy Battery Power Source

Colin Rathbun · Oct 8, 2015

Hi there,

I have a remote site being used for an antenna relay. The site gets 120v but gets a lot of outages. As it stands, I have a household battery backup UPS plugged in between the wall power source and the antenna power supply so that when the power goes out the antennas don't lose power and the UPS kicks in. I have a problem when there are long power cuts. The UPS really only runs for an hour or two at most and increasing it's size (500va vs 1500va) does not seem to help. I am guessing that all the electronics inside use quite a bit of power so there is a big overhead that drains the battery.

The antennas each draw 8watts.

So I'm thinking to get a trickle charger, and inverter and some UPS batteries. The setup I am imagining would be a little like this:

120v power source > Trickle Charger > battery > Inverter > Antenna power supply

I'm sure I can get this to work in the short run but I'm concerned of the longevity of the battery under this condition since there will be continuous power consumption from the inverter. Also concerned of fire hazards with this for the repeated charging of the battery. Any suggestions? (apologies, my electrical knowledge is limited)

Andy™ · Oct 8, 2015

well the power going in needs to be more than whats going out to keep the batteries charged, so really the batteries will only be discharging during power failure and charged after then kept topped up. deep cycle batteries would be best, but if its only occasional power failure then normal car batteries would most likely do the job. at 8w, your biggest drain will probably be the inverter

ProDave · Oct 8, 2015

Try and re design it so your load works directly from 12V dc.

then you have a float charged battery that carries on running when the power goes off.

binky · Oct 8, 2015

look at off-grid solar systems, it's quite straight forward, panel / wind turbine, battery charge controller, battery (do keep warm ie insulated box) output to inverter or direct DC as Pro Dave says

Colin Rathbun · Oct 8, 2015

Andy™ said:
well the power going in needs to be more than whats going out to keep the batteries charged, so really the batteries will only be discharging during power failure and charged after then kept topped up. deep cycle batteries would be best, but if its only occasional power failure then normal car batteries would most likely do the job. at 8w, your biggest drain will probably be the inverter

So if I connect the trickle charger to the battery terminals and also connect the inverter to the same terminal, then the inverter will effectively be running off the trickle charger and not "through" the battery? Assuming the charge produces more power than the drain of course. If that is the case, then that would be great because the battery would not get over-used....

For the battery, i was just going to use the same batteries that go into the UPS. IE the UPS replacement batteries.

binky · Oct 8, 2015

what voltage are they?

trickle charge (decent car battey charger will proably do) leisure battery (probably far cheaper than UPS batteries and hold far more energy). Connect inverter to same battery terminals, plug UPS into inverter. Don't forget a fuse in battery leads in case of a short