What voltage can agm batteries safely be taken down too?

[stuee]

Hi all. As per this thread here:

http://www.outerlimits4x4.com/ftopic169630.php

I've purchased a Full River 100ah agm battery.

I've only just had a chance to put the multimeter over it and it was sitting at 6.94V!!! I double checked this with another multimeter I had in the shed. I know this would probably mean a dead lead acid but this is my first agm. What do people think (or preferably know)?

Do agm batteries come fully discharged or is this normal for them??

I only have a limited warranty so I want to sort it out in the next couple of days if this isn't right. I've put the battery on the charger to see if I can charge it up fully too.

Cheers all.

[stuee]

Edit* scrap the charging. I don't want to fully charge it then try to explain it only came with 7V when I purchased it. I can find anything to support the idea that agms would be supplied with such a low charge except that the $30 agm (12V, 9ah) I bought from Jcar for another project only had 8V and its brand new.

[drivesafe]

Hi Stuee, get that battery on a battery charger as soon as possible, at that voltage, they are usually stuffed BUT AGMs do sometimes come back from low voltages.

[stuee]

Hi Stuee, get that battery on a battery charger as soon as possible, at that voltage, they are usually stuffed BUT AGMs do sometimes come back from low voltages.

What would be a good indicator on whether or not the battery is stuffed?

Being 100ah I wouldn't expect the thing to go flat overnight but I'm tempted to run a known load (like a light of some description) on it for a period of time to see if it performs as it should.

I'll definitely be contacting the supplier to notify them of the issue. I would like to know what they think of it. Every lead acid battery I've bought has been close to fully charged when purchased.

[-Scott-]

I forgot to disconnect my car PC after a trip, and drained my FullRiver to the point where I expected it would be stuffed.

I recharged it anyway, and it seems to be working OK. I've probably shortened its life, but any reduction in capacity isn't noticeable.

[stuee]

I forgot to disconnect my car PC after a trip, and drained my FullRiver to the point where I expected it would be stuffed.

I recharged it anyway, and it seems to be working OK. I've probably shortened its life, but any reduction in capacity isn't noticeable.

Do you remember what voltatge it got down too?

In the last 10 mins the battery is showing 10.14 volts with the charger disconnected. (this is a handy way of documenting it and I can refer back to this later for notes haha). Its only a 6 amp charger so its gonna take a fair while to get fully charged.

[drivesafe]

Its only a 6 amp charger so its gonna take a fair while to get fully charged.

Which is actually the best way to charge any battery.

[stuee]

Well rang the supplier this morning and have been told to take it in.

They're gonna test it for me though if the charger doesn't bring it up then they will replace it on the spot. Good to deal with so far.

[+dj_hansen+]

Interesting.. i purchased 1 of each in the same deal last night, the guy tested them on the spot but i didnt see what he was doing really, so i hope mine are ok!

Better check them tonite i spose!

[stuee]

Well the battery was cactus. I took it in and they replaced it one the spot. They checked the new battery (so I didn't go home with another dud) then showed me how bad the old one was in comparison.

[me3@neuralfibre.com]

Depends on temperature.

As a guide - 12.1v at 25-30c.
Higher if it's hotter - lower if it's colder (+/- 0.2v approx)

Measure after sitting with no load for 30mins. Any load will give incorrect measurement.

Paul

[its aford not a nissan]

i got a 120 a/h battery and when i got it home the voltage was over 13 volts and holds 13.6 volts when fully charged , i also got a fullriver 100 a/h a few months later and it read 11 volts when i got it home , i was a bit concerned but after charging it up it holds 13 volts , and after running the fridge for 3 days it still holds over 12 volts so i guess it cant be too bad

[drivesafe]

Hi Nissan, any voltage reading from a battery that is higher than 12.8, is what is known as surface voltage and is no indication of the actual State or Charge of the battery.

[its aford not a nissan]

it must be a faulty battery then ( the 120 a/h ) cause even after 1/2 a day running the fridge it still reads over 13 volts

[greybeard]

it must be a faulty battery then ( the 120 a/h ) cause even after 1/2 a day running the fridge it still reads over 13 volts

or some inaccuracy in the measuring device

[me3@neuralfibre.com]

it must be a faulty battery then ( the 120 a/h ) cause even after 1/2 a day running the fridge it still reads over 13 volts

or some inaccuracy in the measuring device ;)

I've voting on this.

Paul

[drivesafe]

or some inaccuracy in the measuring device

Most likely the case.

[its aford not a nissan]

well everything else seems to measure up ok
starter battery 12.5 volts after sitting over nite ( i had to flick the headlights on to dissconnect from the 2nd batt to get this reading )
factory alt reads 14.2 when running give or take .1 volts
2nd alt runs at 14.1 volts as to what it says on the alt
the full river batt 100 a/h 13 to 13.4 volts sitting for a week
the 120 a/h agm is currently connected to the starter batt via a red arc battery isolator , currently the isolator stays energised for about 24 hours before the starter batt drains down the voltage low enough to dissengage the isolator , the voltage taken just then was 12.9 volts ( after flicking the lights ) but after a long drive , 3 or 4 hours ,or charging with a seperate charger the isolator has stayed engaged for over 3 days before dissconecting ( without driving )

the red arc isolator dissengages at 12. 7 volts

now my multimeter may be faulty or not reading correctly but that would mean my starter battery and alts are low or not running to spec and my battery charger is miss reading the volts by the same amount

[me3@neuralfibre.com]

well everything else seems to measure up ok
starter battery 12.5 volts after sitting over nite ( i had to flick the headlights on to dissconnect from the 2nd batt to get this reading )
factory alt reads 14.2 when running give or take .1 volts
2nd alt runs at 14.1 volts as to what it says on the alt
the full river batt 100 a/h 13 to 13.4 volts sitting for a week
the 120 a/h agm is currently connected to the starter batt via a red arc battery isolator , currently the isolator stays energised for about 24 hours before the starter batt drains down the voltage low enough to dissengage the isolator , the voltage taken just then was 12.9 volts ( after flicking the lights ) but after a long drive , 3 or 4 hours ,or charging with a seperate charger the isolator has stayed engaged for over 3 days before dissconecting ( without driving )

the red arc isolator dissengages at 12. 7 volts

now my multimeter may be faulty or not reading correctly but that would mean my starter battery and alts are low or not running to spec and my battery charger is miss reading the volts by the same amount

Very interesting.
I'm at Oxley BNE if you want to put a fluke meter on it to confirm.
All sounds ok though cept for the high one - interesting.
PM me if you like.
There is agood "SoC" doc on the Odyssey site from memory, and there used to be one on the fullriver site somewhere.

Paul

[+dj_hansen+]

I put mine on the CTEK7a charger last night, 135 was a tad low, but was onto the "full" lamp in about 1/2 hr, 100 was on the full lamp straight away and i have left it on till i get home tonight.

Now just have to make a new tray as they are 20mm longer than n70 size (doh)!

[rockcrawler31]

i took two lead batteries to the suppliers ( a local auto elec) and he refused to replace the second battery on my assertion that since it was down to 4 volts over a month it was stuffed (the first battery had dropped a cell and was venting - hence dragging it down with it). I said i didn't want to take the risk that it's life was shortened by being so low for so long, and he said he's never heard that idea before and it just needed a charge to be good as new. (obviously he would say that so he doesn't have to try and get the manufacturer to replace the battery and just leave it with me to try and get a replacement)

What arguement or technical speak can i tell them next time they tell me it's full of crap. What can i tell them actually happens inside the battery when you leave it that low for too long that makes it stuffed.?

[drivesafe]

Before you do anything, go to the battery manufacturer’s web site and check al the specs, including warnings and limitations.

If it’s convenient, print it out and take it with you.

If they what to try to baffle you with B/S, frig them with facts!