Backyard Aquaponics
A place to discuss aquaponics

Here is another one for you,

Before I read Rupert's thread on major fish loss I was watching TV and noticed a Police car arrive at a house down the street (Tonight). I had a little sticky but they left fairly quickly with lights flashing. Before this I had heard some yelling down the street (Not uncommon, thought it was neighbours). Today we had 20mm of rain dumped in about 3 hours, plus more than average rainfall throughout the day... This is where I get jinxed.

I read Ruperts thread while watching TV, and responded accordingly. Then I noticed a tow truck pull up at the same house, followed by some power company vans. This time I got super nosey and went and had a look, finding a car on top of a mini sub station (The ones housed on residential property). Strange but nothing unusual except no occupants of car visible. Car got towed away and the workers stood around for a bit scratching their heads...

"Going to have to turn the power off" said one, "How long for?" says the other. By the time I walked into my backyard and said "Aqqquuuaaaapppooonnniiicccsss" the power was off and the bilge kicked in. My neighbour went and asked how long it would be off and got a gruff open ended response. I had tested the backup system before a couple of times to check but only plugged the trickle charger back in yesterday after I removed additional aeration I had running to combat suspected white spot.

My battery was donated free of charge and was a near new marine battery with a CCA of 575 and RC of 105 minutes. I never really worked out the actual AH of it as I assumed it was larger than the equivalant 40AH SLA. The bilge kept chugging away for an hour and doing what looked like a decent job (2.5ah 2000lph), thats when I figured out I had no idea how long I could get out of the battery. 'Googling' in the dark, outside in the wet is not much fun...

All I could find about an AH conversion was something along the lines of AH = RC/2 + 16. Given that the higher the CCA does not equal the higher the AH im guessing that my projected guess at 68AH taken from the RC conversion is about right... And if thats the case, and I am only drawing 2.5AH then how long do you think I will get? (6 hrs? 12 hrs? 28 hrs?).

Power is obviously back on.

May I suggest you run it one day when you have the time at home and find out for sure?

Ideally you'd have enough time to go get a generator, or for the power to come back on. Our power has never been out for more than a few hours before, but I know people who have had theirs out for days and no battery backup will last that long. Steve did a test of his once back in the day, but from what I remember he fell asleep about the time it stopped because such tests are boooring.

lol perhaps connect a switch to the backup pump connected to an alarm to wake you up when the battery is dead.... Either way testing the actual time a back up will last will be better than having a guess and just think it is an excuse to sit in the shed and have beers while you wait. It can't be all bad.

60 to 80AH is pretty much right.

A DC Bilge pump drawing 2.5 amps will run (from a fully charged + floated battery @ 100% capacity) for around 20 hours. This is assuming use-able capacity of around 50 AH.

As for testing, leave the main pumps running, start the backup and monitor it hourly until you are happy with how long it lasts for. If you want a minimum of 6 hours, and its still running at 12 volts + after 7 hours, you have a good backup.

I use a carbon pile tester for checking my batteries, it puts a huge load on the bank for 15 seconds, gives a very good indication of total capacity.

Thanks man, very reassuring to know...