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Help need charging a 12V PB battery

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Rocker11/04/2018 15:45:22
347 forum posts

I have a 12V ,7.0 Ah battery and I am trying to charge it up on mu Overlander 80 W AC/DC charger .Not sure what is happening .I have set the charger for Pb battery and it is charge OK but now it has reached 18 .v and is discharging the battery it is down to 16.3 volts at the moment but still discharging the battery further .When I take the battery of the charger and connect it to my 12v car battery charger it is showing full charged but when I put it back on the Overlander 80 W ac /dc charger it starts to discharge it again Is this normal or is there something wrong .I have stop charging it at the moment not sure if thing are going right .HELP ( it is set on charging and not set on discharging)

Edited By Rocker on 11/04/2018 15:46:22

Edited By Rocker on 11/04/2018 15:54:58

Steve Balaam11/04/2018 15:55:13
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117 forum posts

Check the charger settings to see if it's set to cycle and not charge

Dickw11/04/2018 15:57:12
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661 forum posts
93 photos

I'm a bit worried about the 18v. Apart from setting it to Pb charge, what did you set the charge curent and battery volts to?

Dick

Simon Chaddock11/04/2018 15:57:52
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5683 forum posts
3021 photos

Rocker

18V on charge will do a 12 V Pb no good at all. smile o

If you set the Overlander to 6 cell (12V) Pb it should not go higher than 14 V and charge at 7A (1C) max.

Assuming you set the Overlander up correctly and the connections were good then something is wrong with it, at least on the Pb cycle..

Cuban811/04/2018 19:29:07
2905 forum posts
1 photos

If we're talking about a 12V sealed gel battery, then I'd really not charge it at more then 0.1C - i.e for 7A Hr then ideally 700ma or 1A max.

1C charging tends to heat the electrolyte, may cause gassing (not good for them)  and in my experience shortens the life of the battery considerably. Sealed gel Pb batteries are tricky little devils and their charging methods are quite complex.

The 18V on a 12V battery is very alarming - something sounds wrong with the reading.

 

Edited By Cuban8 on 11/04/2018 19:35:35

onetenor11/04/2018 20:21:53
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1901 forum posts

14.5 or so is max for charging voltage for a 12g battery, no more than 5 amps max rate.18v means battery is overcharged and the charger may be correcting the error. Overcharging can do all sorts of damage.

Rocker11/04/2018 20:29:14
347 forum posts

Would it be OK to use my 12 volt car Battery charger or is that a no , no

Denis Watkins11/04/2018 21:29:41
4322 forum posts
104 photos

OK Rocker, just this once

The gel cell is rated 7ah so max 7 hours at 1 amp, minimum 10 hours at 700mah

If the gel cell gets more than mildly warm then stop to cool it down

Martin Harris11/04/2018 21:37:57
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9262 forum posts
245 photos

Rocker, you wrote "I have set the charger for Pb battery and it is charge OK but now it has reached 18 .v"

There's no mention of the cell count...did you set it for 6 cells? I think the display shows something like 12.0V (6P) at the bottom right when set correctly. If it was showing something like 18.0V (9P) or 20.0V (10P) it would explain why the cell appears to have been overcharged.

Don't worry if the display shows 12.0V (6S) or similar - the info above is from the online manual but I can't see any logic in the use of P...

Edited By Martin Harris on 11/04/2018 21:44:40

J V R11/04/2018 23:00:35
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326 forum posts
62 photos

Rocker you may have a faulty cell that is causing the over charge, I had a similar problem on a 24 volt Land rover due to a bad cell the total charge went up to around 30 volts

Nigel R12/04/2018 10:44:39
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3730 forum posts
582 photos

"on mu Overlander 80 W AC/DC charger"

which exact model Rocker?

Rocker12/04/2018 11:19:46
347 forum posts

The model is" Overlander RC 6- VSP " and I did not set it to 12 v 6 cell .I have now set it to 12v 6 cell and the cut off is 14.7 so that sounds better

Cuban812/04/2018 12:15:16
2905 forum posts
1 photos
Posted by Rocker on 12/04/2018 11:19:46:

The model is" Overlander RC 6- VSP " and I did not set it to 12 v 6 cell .I have now set it to 12v 6 cell and the cut off is 14.7 so that sounds better

What is the current set to?

Rocker12/04/2018 13:09:32
347 forum posts

IT is now set at "PB Charge 1.0 a 12.OV (6P ) Does that sound right ?

Biggles' Elder Brother - Moderator12/04/2018 13:31:43
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Moderator
15748 forum posts
1460 photos

That sounds better!

At 7A and 12V you are actually above the max power of this charger - ie 12x7 = 84W. Its not likely to be a problem TBH, but it may be the cause of your difficulties?

If it was pushing up to 18v and 7A that is way, way over the charger's capacity - i.e. 18x7 - 126W!

BEB

Edited By Biggles' Elder Brother - Moderator on 12/04/2018 13:32:14

Denis Watkins12/04/2018 13:38:51
4322 forum posts
104 photos

12v 7mah is most likely a sealed gel cell

They are OK, but are designed for trickle charging,

Does the battery have Pb on the causing Rocker?

A lead acid will have Pb stamped upon it.

Ideally 1/10th C charge, one tenth capacity being 700mah charge

Assuming some charge is in the battery, then 1A for 7 hours will be too long

Is the charger auto shut off.

To make the battery useful a 1A 12v charge will revive the battery but it needs close attention

Cuban812/04/2018 15:02:20
2905 forum posts
1 photos

The charger will initially sink the maximum preset current into the battery (0.1C) and over time as the charge progresses and battery terminal voltage approaches the programmed max charge voltage (probably 14V or just above for cyclic charging or a little above 13.5V for long term float charging), then things will balance out and the current flowing into the battery will fall to virtually nothing.

The damage is done during the inital phase, if current is not limited to an acceptable level which is usually 0.1C.

Nigel R12/04/2018 15:39:31
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3730 forum posts
582 photos

Rocker, what is the current state of the battery, have you discharged it down to a respectable voltage?

"you are actually above the max power of this charger"

I have the older version of the charger and it just self limits the current to (theoretically*) prevent the magic smoke from coming out.

* supplied power brick in mine was in no way capable of sustained 80W output.

PatMc12/04/2018 17:30:20
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4381 forum posts
524 photos
Posted by Rocker on 11/04/2018 15:45:22:

I have a 12V ,7.0 Ah battery and I am trying to charge it up on mu Overlander 80 W AC/DC charger .Not sure what is happening .I have set the charger for Pb battery and it is charge OK but now it has reached 18 .v and is discharging the battery it is down to 16.3 volts at the moment but still discharging the battery further .When I take the battery of the charger and connect it to my 12v car battery charger it is showing full charged but when I put it back on the Overlander 80 W ac /dc charger it starts to discharge it again Is this normal or is there something wrong .I have stop charging it at the moment not sure if thing are going right .HELP ( it is set on charging and not set on discharging)

Edited By Rocker on 11/04/2018 15:46:22

Edited By Rocker on 11/04/2018 15:54:58

I think you'll find that the voltages you're reading are what the charger is connecting to the battery not the battery's voltages.
This means that if the charger's 80W limit is accurately applied then when the reading was 18V the battery was being charged at 4.44A [80W/18V = 4.44A].
The battery wasn't discharging, it's voltage would have been increasing due to the received charge..The 16.3v you read was charger's voltage, which would have reduced because it would have been trying to increase the current to what the 80W limit would allow. At this point the current input would have risen to 4.91A [80W/16.3V = 4.91A]

Now that you've set the battery's correct nominal voltage you should set the current at 0.7A.

It's not a good idea to discharge a PB battery through a charger, it wouldn't achieve anything positive but would  decrease it's life by one charge/discharge cycle. Also PB batteries can be irreparably damaged if discharged too deeply.

PS the above would also explain JVR's Land Rover battery experience.

Edited By PatMc on 12/04/2018 17:48:04

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