How many volts is flat

How many volts is flat

Postby DingoCC on Wed Dec 23, 2015 7:47 am

I saw a battery box (which I'm guessing would hold a deep cycle AGM) with a sticker on the side. It said 12.7v 100%, 12.5v 80%, 12.2v 50%. 10.5v flat.

As a general rule is this true?
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Re: How many volts is flat

Postby tmichel on Wed Dec 23, 2015 8:57 am

yes
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Re: How many volts is flat

Postby ag9111 on Wed Dec 23, 2015 9:21 am

I thought it was closer to 11.5V
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Re: How many volts is flat

Postby borngeek on Wed Dec 23, 2015 9:28 am

Multimeters at 10 paces? :P :lol: :lol: :lol:
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Re: How many volts is flat

Postby NowForThe5th on Wed Dec 23, 2015 11:56 am

0v is completely flat. ;)
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Re: How many volts is flat

Postby Ricky on Wed Dec 23, 2015 2:18 pm

11.5v to11.9v would be flat, depends on the battery.
Anything under 12.1v is severely reducing the life span of the battery.

If your battery hits 10.5v chances are its toast. And if you do recover it you will have reduced its life by probably 80-90%.
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Re: How many volts is flat

Postby coughy on Wed Dec 23, 2015 3:28 pm

where talking about DEEP cycles Here lads dont forget
yes it would be the case if the item using it draws a few amps then it would be struggling to work
but if only a radio or something it will still work and drop the volts down more
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Re: How many volts is flat

Postby salt36 on Wed Dec 23, 2015 3:34 pm

Ricky wrote:11.5v to11.9v would be flat, depends on the battery.
Anything under 12.1v is severely reducing the life span of the battery.

If your battery hits 10.5v chances are its toast. And if you do recover it you will have reduced its life by probably 80-90%.


coughy wrote:where talking about DEEP cycles Here lads dont forget
yes it would be the case if the item using it draws a few amps then it would be struggling to work
but if only a radio or something it will still work and drop the volts down more


Both are very true, a deep cycle battery will stop operating fridge, for example, and yet still operate a radio or LED lights...

I was always told that once the battery gets down to 12 Volts charge it or risk losing it !
I apply the rule to any 12 Volt battery, deep cycle or normal start.
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Re: How many volts is flat

Postby coughy on Wed Dec 23, 2015 3:41 pm

true to some degree
a agm is a totally different animal and is built to go flat and then recover from it
totally different from a lead acid cell

but yes if you stick to this you will be fine

i play with batterys all day every day as part of my job and you would be surprised what comes back and what dont

but dont forget we have VOLTS and AMPS to very different things in a battery lots of variables involved

but yes 11.2 is flat
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Re: How many volts is flat

Postby Ricky on Wed Dec 23, 2015 5:14 pm

coughy wrote:true to some degree
a agm is a totally different animal and is built to go flat and then recover from it
totally different from a lead acid cell

but yes if you stick to this you will be fine

i play with batterys all day every day as part of my job and you would be surprised what comes back and what dont

but dont forget we have VOLTS and AMPS to very different things in a battery lots of variables involved

but yes 11.2 is flat


Agm or not, you will reduce the batteries cycles the more you discharge the battery.
Saying an agm is built to go flat and then recover is untrue. An agm has the same cycling limitations as other deep cycles, eg. Gel.
The more you discharge a battery the less cycles you will get, regardless of the makeup.

http://www.fusionagmbatteries.com.au/ta ... (DeepCycle).aspx

I would advise anyone who is interested to take a look at the site in the link and scroll down to the chart that shows cyclic life in relation to depth of discharge.

You will note that these are agm batteries, and one of the best in Australia.
You will see that if you take a 100A/H battery to 70% (used 30A), you can achieve 1600 cycles.
Take that same battery to 30%, (used 70A) and you can expect only 200 cycles. A drastic reduction in battery life.

An agm battery benefits because it can accept a much higher charge rate than other deep cycle types, it can be mounted in any position, and there is nothing to spill if the case is damaged. They can not discharge any more than any other battery without suffering the same damage.

Also, an agm IS a lead acid battery. It uses Absorbent Glass Matt to soak up the lead acid and hold it.
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Re: How many volts is flat

Postby honeyiboughtamitsi on Wed Jul 06, 2016 11:21 am

DingoCC wrote:I saw a battery box (which I'm guessing would hold a deep cycle AGM) with a sticker on the side. It said 12.7v 100%, 12.5v 80%, 12.2v 50%. 10.5v flat.

As a general rule is this true?


0-11.9V is flat.

Make sure that the battery is never discharged below 10.8 volts. If AGM batteries are below 10.8 volts, permanent damage will occur
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Re: How many volts is flat

Postby bitplay33 on Thu Nov 24, 2016 2:29 pm

Depends on the chemistry of the battery. Deep Cycle could be most battery types, Pbacid, AGM and Gel.
Lead Acid 10.5 volts would be considered in operable for most loads. Continue to draw current from a resistive load like a heater then the lead Acid will be destroyed.
AGM and Gel will have different voltage points. Different brands have individual data sheets, so brand names also to be considered.
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Re: How many volts is flat

Postby RHKTriton on Thu Nov 24, 2016 6:41 pm

Just about all rechargeable batteries will lose lifespan if discharged beyond a point.
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Re: How many volts is flat

Postby striker99 on Fri Nov 25, 2016 8:21 am

For the sake of trying to make the battery last I try not to run our dual battery below 12.2v.
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Re: How many volts is flat

Postby Skullator on Thu Apr 06, 2017 3:57 pm

10v is considered to be discharged to a point the battery is starting to sulfate and damage the plates, the longer a battery sits below 10v the more damage is done
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