Auto Cut-off circuit

[tmaker]

i can do Electrical and mechanical BUT not electronic

what i need :

- a circuit board to control the battery charger ( that will charge a normal car battery )

where do i use it :

- the car battery ( 70 A ) is FOR STANDBY for power outages ( very frequent here )

- the battery will run a DC 12 volt air pump which will provide aeration for my fish pond. it will last for about 4 hours at least.

- i am into Aquaponics and my 3000 L pond have 140 over fishes in it ( not critical at this moment as they are small ( about 2.5" to 3.5" now ) but when the fishes grew bigger in 6 weeks time,then it will be a VERY BIG ISSUE.

- I HAVE ALREADY HOOK UP THE AUTO CUT IN CIRCUIT WHEN THE POWER FAILS - my air pump will work.

how it MUST work:

- when the battery is low the circuit will switch on my battery charger to charge the battery

- when the battery is at a sufficient level,it will switch off the charger.

-------------------------------

THE REASON IS I DO NOT WANT TO KEEP THE CHARGER SWITCHED ON FOR 24 HRS and even if i buy the higher end battery charger, I still need to keep the charger switched on at all times.

anyone can built one for me and what's the cost or is there any other alternative ?

thanks guys.

[IMHO]

What's wrong with having the charger on 24x7?

[tmaker]

cost mate.

it will draw electricity,right ?

[IMHO]

OK, maybe best if we back this up and get some system specs...

What's the wattage rating of the air pump?

How many hours/day does it run?
What's the longest outage duration the needs to be supported?

How are you powering the pump when mains is available (you say it's 12VDVC)?

[ksamuiguy]

Buy a LARGE UPS System.

All automatic and reliable.

OR

Automatic Battery Charger. have one at Home Pro 4,0000 baht, 12 & 24 Vdc, fully automatic with Pulse Technology.

[tmaker]

OK, maybe best if we back this up and get some system specs...

What's the wattage rating of the air pump?

How many hours/day does it run?

What's the longest outage duration the needs to be supported?

How are you powering the pump when mains is available (you say it's 12VDVC)?

555.

most info are in my ori post.

to answer your Question in your post :

1. my tank is 300 L - so i put on standby a 120 W air pump - that will need 10 A to run it. - so I chose a 70 A battery ( also for future where i will add in another 4 x 1000 L tanks )

2. only use for outage - so,no run hr per day

3. the outage is is about 2 to 3 hrs on the high side and low side about 30 mins - so .i'm ok with my standby time of 4 hrs

4. I have a main pump on 220 V AC - this is DC air pump for standby

[tmaker]

Buy a LARGE UPS System.

All automatic and reliable.

OR

Automatic Battery Charger. have one at Home Pro 4,0000 baht, 12 & 24 Vdc, fully automatic with Pulse Technology.

1. Large UPS system - THIS WILL SET ME BACK 120,000 THB - I need 10 A supply

2. Auto Battery charger - see my ori post - the last paragraph

[billphillips]

Buy a LARGE UPS System.

All automatic and reliable.

OR

Automatic Battery Charger. have one at Home Pro 4,0000 baht, 12 & 24 Vdc, fully automatic with Pulse Technology.

1. Large UPS system - THIS WILL SET ME BACK 120,000 THB - I need 10 A supply

2. Auto Battery charger - see my ori post - the last paragraph

Errrm, not exactly 120k for a ups. Try thinking around 5k for a nice one, 10k for a very nice one. Can they go wrong ... Yes of corse they can, just the same as a bat charger, a power out diverter or a battery. In fact, that's exactly what a ups is.

[Crossy]

The amount of energy a full auto battery charger will use when floating the battery is tiny, to be honest that's all you need to do. I just checked mine at 3 Watts, about 100 Baht per year.

However, if you really want to switch the charger off when the battery is full one of these http://www.mynpe.com/mynpe/more.php?data=014398010104 should be readily adaptable to drive a relay which can then switch the charger mains input.

Many other circuits with similar functions available on the net.

[sappersrest]

How about a small solar panel with regulator to keep the battery charged.

[grin]

I have a couple of small solar panels that are made to keep 12V batteries charged. They came with both grips and bolt type connectors.

We use to keep the batteries charged in seldom used motorcycles.

I bought them in the U.S. but they might be available here.

Grin

[tmaker]

The amount of energy a full auto battery charger will use when floating the battery is tiny, to be honest that's all you need to do. I just checked mine at 3 Watts, about 100 Baht per year.

However, if you really want to switch the charger off when the battery is full one of these http://www.mynpe.com/mynpe/more.php?data=014398010104 should be readily adaptable to drive a relay which can then switch the charger mains input.

Many other circuits with similar functions available on the net.

thks mate.

will check them out.

[tmaker]

I have a couple of small solar panels that are made to keep 12V batteries charged. They came with both grips and bolt type connectors.

We use to keep the batteries charged in seldom used motorcycles.

I bought them in the U.S. but they might be available here.

Grin

I did check those out - but in Thailand - they can't answer my questions on supply and load on my battery and also they do not provide warranty on the panels.

so,this puts me off.

I tried to contact another company but....no reply as my deal is TOO SMALL... lol...

[sappersrest]

Some thing like this is ideal used one for years, probably need a regulator as well.

http://www.maplin.co.uk/p/solar-powered-12v-24w-battery-trickle-charger-n59fu

[tmaker]

Some thing like this is ideal used one for years, probably need a regulator as well.

http://www.maplin.co.uk/p/solar-powered-12v-24w-battery-trickle-charger-n59fu

555 yea.

but then, thais shop owner will never tell you this is available . they only want to sell you the expensive type and/or just sell you .

always will say - mai nai chai or mai mi.

[Litlos]

What you need is not a battery charger, but a battery maintainer, they look the same but there is a big difference in how they operate. One I have used previously and I was very impressed with is Ctek from Sweden.

Have a look on their website for details. ctek.com

Note: Generally for battery charging the rule of thumb is battery amp hours divided by 10 gives you charger output. So for a 70Ah battery you will be looking at a max rated charger of 7A.

Cheers