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Topic: electric fence batteries - possible use ? (Read 1 time) previous topic - next topic

Twogan

Hello,

I have a project that draws between 90 and 190 milliamps.

I need it to run for 10 days constantly.

I have been looking at car batteries and smaller sealed lead acid batteries, however, I do come across a lot of ' car battery killed my arduino' posts. It seems using 12-14v input can make the on board regulator get too hot.

To remedy this I have been googling high capacity 9v batteries. I have come across many 'Electric fence Batteries'. like this :
http://www.flytesofancy.co.uk/chickenhouses/Hotline_Saline_9v_Batteries.html

The second one down offers 130Ah for £36. Seems to good to be true.

Is it possible to use it for my project ?

Whats the catch ?

Many Thanks
Twogan

CrossRoads

Instead of using the little heat generators, er, I mean linear voltage regulator, on the board, go with an off board switching regulator.They take in the higher voltage and efficiently convert it to 5V with very little battery power thrown away as heat.

See if you can locate this or something comparable at Farnell or your favorite source, and power your Arduino thru the 5V pin instead of thru the regulator.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=811-2115-5-ND
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

jackrae

The catch is that these batteries are not rechargeable so it makes for an expensive one-time use.  Follow the previous recommendation and go for a switching regulator.  That is by far the most efficient way to go. 

Say your 5 volt load is a maximum of 200ma, then power requirement is 1 watt, which is  24watthours per day.   So total requirement over 10 days is 240watthours.  At 12 volts, that equates to around 20AH.  Say you limit depth of discharge to 50%, to prevent irreversible battery damage, then you need a battery of at least 40AH.

Twogan

Thanks.

Of course. I see now the lack of recharge-ability ( rechargeableness ? :)) is the downside.

I am making a one off installation that just needs to last 10 days. I assume that as they are single use I can run them all the way down and get nearly the whole capacity out of them without worrying about damaging the disposable battery.

This makes the pricing seem favourable again, and also being 9v I don't have to worry about overheating the arduino, and therefore dont have to get a stepping regulator.

I have managed to find out that an average electric fence uses about 60 milliamps of current, so do you think these Batts will manage outputting a continuous current between 90 and 200 milliamps ?

Many Thanks
Twogan

sinkoman

10 days = 240 hours

200 mA * 240 hours = 48A

I think the batteries should be fine.

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