12v low voltage cut out

Submitted: Friday, Apr 17, 2015 at 12:12
ThreadID: 117520 Views:3773 Replies:5 FollowUps:4
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HI
To all, just came across a Baintech programmable [10 profiles] 10 amp low voltage disconnect .Great for one fridge . The different profiles allow for different battery chemistries /voltages , cut in cut out settings . Definitely the simplest out there but also at the right price $35.90 .
Batterybusiness .com.au
40amp LVD Victron Energy 10 programs similar to above .Available as above
For those of u who must have the best "The 12v shop" fully programmable .Intervolt programmable voltage sensing relay 150 amps continuous .

Having one of these would have saved me a battery or two over the years.
Every bodies experiences or opinions would be appreciated .

Swampfox
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Reply By: Member - Phil G (SA) - Friday, Apr 17, 2015 at 13:47

Friday, Apr 17, 2015 at 13:47
I used to use the Jaycar kit for low voltage cutouts because you could alter the voltage cutout settings - but that was 15 years ago.

Main issue is that they consume current. With the smaller units such as the Baintech, it is only around 4mA (or 2mA when disconnected), which won't matter at all.
But with the large units, it might be 200mA to run the relay so it would be an issue.
AnswerID: 552585

Reply By: Sigmund - Friday, Apr 17, 2015 at 16:02

Friday, Apr 17, 2015 at 16:02
Sounds like a good idea.

My fridge has a cut-out but it's set too low.

I was surprised reading AC Delco tech stuff to find that they recommend that deep cycle batteries don't go below 80%. Have always thought the line was at 50%.
AnswerID: 552591

Reply By: Trevor&Verna - Friday, Apr 17, 2015 at 16:27

Friday, Apr 17, 2015 at 16:27
Can any of you knowledgeable readers advise a recommended setting for the cut off?
Mine is a 40L Engel drawing from an 80Ah AGM battery.
I have recently purchased a Baintech cut-out as per 'swampfox'
Trevor&Verna, Kal WA

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AnswerID: 552594

Reply By: swampfox - Friday, Apr 17, 2015 at 19:05

Friday, Apr 17, 2015 at 19:05
hi
11.66 volts is the 20% level of either lead or AGM [temp does vary this ]
Depending upon application
some appliances have a high starting requirement that might pull the voltage down to very low levels causing the unit to trip in out in out etc
If this happens with the cheaper units set the voltage higher .
The more expensive units have a time delay and some times adjustable .
A fridge should not have this problem to a great extent . Others may have some experiences to offer .

swampfox
AnswerID: 552603

Follow Up By: swampfox - Friday, Apr 17, 2015 at 19:10

Friday, Apr 17, 2015 at 19:10
hi
I meant set the voltage lower .
I would not set lower than 11.5 volt in theory for a high start power draw.
My preference would be 11.8 volt to start with .
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Follow Up By: Member - abqaiq - Saturday, Apr 18, 2015 at 08:03

Saturday, Apr 18, 2015 at 08:03
Perhaps consider a "12V Low Voltage Protector" from EV-Power in WA [no connection to me, Blah, Blah]. Handles up to 50A draw consuming 0.6mA, set at 12.0 V cutout for ~$35.00. Bare bones no frills encapsulated circuit board.
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FollowupID: 838229

Follow Up By: swampfox - Saturday, Apr 18, 2015 at 16:49

Saturday, Apr 18, 2015 at 16:49
hi
Thanks abqaiq
50amp $35 great stuff
swampfox
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Reply By: Allan B (Member, SunCoast) - Friday, Apr 17, 2015 at 23:11

Friday, Apr 17, 2015 at 23:11
The whole concept of equating battery 'State of Charge' to voltage is an approximation at best. Furthermore, the voltages referred to are with a battery at rest with no current being drawn and no charge being supplied and battery temperature at 20-30c.
Accordingly it is difficult to reliably monitor and protect batteries from over-discharge whilst the battery is supplying a fridge or any other load.

A further difficulty arises due to voltage drop in the cable cable between the battery and the point where load and the under-voltage detection is being applied. To have any chance of success the voltage sensing must be connected at, or close to, the battery terminals.

Providing the above precautions are observed and assuming a deep-cycle battery, the protection should be set to disconnect the load when the battery falls to 50% SOC which is theoretically 12.2 volts at the battery terminals. However due to the load current and typical battery resistance, it is more appropriate to set the trip at say 12.0 volts whereupon the voltage will probably rise to 12.2 volts soon after the load is disconnected. The protection device should not restore supply until the voltage rises above 12.4 volts and the operation is improved if the device incorporates some 20 seconds of time delay to avoid 'hunting'.

Regularly discharging lead-acid batteries below 12.0 volts invites permanent damage.

Cheers
Allan

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AnswerID: 552612

Follow Up By: swampfox - Saturday, Apr 18, 2015 at 06:35

Saturday, Apr 18, 2015 at 06:35
Hi
Agree with all u have said
Although I have not measured the battery voltage with a fridge connected . First impressions is the voltage would not be pulled down a large amount .This is why I was researching the LVD and found a voltage selectable to be the best option [to suit all the variables ].

cheers
swampfox
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