Battery. Why is it so?

Submitted: Wednesday, Aug 03, 2016 at 12:52
ThreadID: 133136 Views:2736 Replies:9 FollowUps:7
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My van has 2 X 6 volt batteries in series. The SOC is showing 100% & voltage 12.7.
I have just disconnected & removed the batteries in order to check water levels and hydrometer test. 5 cells in the green & 1 on border of green/white.

My question is: Why is it that when I re-installed the batteries the SOC has dropped to 65%?

The same problem occured when I last checked the batteries and it took several days, using both the solar & charger, to restore SOC to 100%.

Cheers
Ted
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Reply By: wombat100 - Wednesday, Aug 03, 2016 at 16:08

Wednesday, Aug 03, 2016 at 16:08
How did you determine your SOC ??

AnswerID: 603058

Follow Up By: henpecked - Wednesday, Aug 03, 2016 at 18:36

Wednesday, Aug 03, 2016 at 18:36
SOC reading is from the solar regulator/controller.
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Follow Up By: Peter_n_Margaret - Thursday, Aug 04, 2016 at 12:25

Thursday, Aug 04, 2016 at 12:25
What brand/model solar controller?
They are not all made equal.
How does it determine the SOC. Maybe read the manual?

Cheers,
Peter
OKA196 motorhome
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Follow Up By: henpecked - Monday, Aug 08, 2016 at 17:01

Monday, Aug 08, 2016 at 17:01
Peter, the controller is a AECA 15 amp unit. There is some info in the book re. SOC, a bit "Hi Tech" for me though.

Thanks Ted.
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Reply By: oz doc - Wednesday, Aug 03, 2016 at 21:45

Wednesday, Aug 03, 2016 at 21:45
Hi Ted , did you add any water to the cells?doc
AnswerID: 603063

Follow Up By: henpecked - Thursday, Aug 04, 2016 at 10:21

Thursday, Aug 04, 2016 at 10:21
G'Day Doc. Yes. Added a small amount of water to each cell.

I'm also wondering if separating the 2 batteries by disconnecting the series link may have had some effect.

Ted
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Reply By: Member - Jim B8 - Thursday, Aug 04, 2016 at 10:19

Thursday, Aug 04, 2016 at 10:19
One possibility to explore is that one cell cold be getting close to failure, while on charge it is "ok" but when you remove the charge, it drops its charge very quickly. When reconnected to charge, it eventually makes it back up to an acceptable state? So perhaps, a lot of the solar charge is being wasted in leakage of this cell?
Easy to test, get the batteries load tested and it will fail if this theory is correct.
Good luck
AnswerID: 603076

Follow Up By: henpecked - Thursday, Aug 04, 2016 at 10:28

Thursday, Aug 04, 2016 at 10:28
Thanks Jim, the one cell that is not completely in the green zone of hydrometer could be the culprit.

Ted
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Reply By: Member - DOZER - Thursday, Aug 04, 2016 at 11:00

Thursday, Aug 04, 2016 at 11:00
surface charge is what you are reading first off, and one or both of your batteries are on their way out.
b4 you bag me out, walk a mile in my shoes, then your a mile away and have my shoes :)

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AnswerID: 603077

Reply By: member - mazcan - Thursday, Aug 04, 2016 at 12:55

Thursday, Aug 04, 2016 at 12:55
hi
I.m with Jim B8 and Dozer on this
imho you have at least 1 failing cell in each battery all the charge rate will be constantly going to them to try and keep them boosted and as soon as you disconnect charge will rapidly drop it,s a no win situation time for new set
been there done that scenario
cheers
AnswerID: 603080

Reply By: Nomadic Navara - Thursday, Aug 04, 2016 at 14:03

Thursday, Aug 04, 2016 at 14:03
Maybe the batteries just need equalisation. Does your battery charger have an equalisation stage on it? If so is it enabled or disabled?

Read more here - 9. HOW DO I CHARGE (OR EQUALIZE) MY BATTERY?. When you have that sorted out, read the rest of the site.
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AnswerID: 603081

Follow Up By: henpecked - Thursday, Aug 04, 2016 at 21:01

Thursday, Aug 04, 2016 at 21:01
No Peter, my charger is evidently only a power supply from Wialki Electronics with no fancy stuff.

Thanks
Ted
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Follow Up By: Nomadic Navara - Thursday, Aug 04, 2016 at 23:51

Thursday, Aug 04, 2016 at 23:51
I suggest you are not treating your batteries correctly. What is the set voltage of your Wialki PSU? Your solar regulator will probably have the set voltage for the absorption charge at a higher level than the PSU voltage. The PSU will bring your batteries so much and when the solar charging commences to charge the battery further the PSU will cease charging as soon as the system voltage starts to exceed its set voltage. At that stage the solar will be the only charging mechanism.

I suggest you get yourself a proper battery charger before you do any more damage to your batteries. If you are going to continue using flooded batteries then you will need one that includes a boost stage as part of its charging regime.
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Reply By: The Bantam - Thursday, Aug 04, 2016 at 18:52

Thursday, Aug 04, 2016 at 18:52
First and above all ... adding water to your batteries WILL effect the state of charge.
Lead Acid batteries are a water / acid reaction .... adding water will dilute the acid and effect the state of charge.

This is why when doing battery maintenance you do you observations and measurements before you top them up, THEN you put them back on charge till they are fully charged.

Second remember reading voltage ( which is what your battery managment system does) is not a bang to rights measure of state of charge and may be effected by errors.

Third ..... every cell in a battery is an individual ...... they will all have differences ....... as batteries are charged and discharged normally the differences between these cells my widen.
This is why it is wise to equalise batteries from time to time ...... basicly you give em a good flogging.

Your batteries may be on the way out ..... remember the basic life span of a Lead acid battery is 2 years in service ........ by some minor chemical trickery from the manufacturers the practical service life can be extended to 5 to 7 years ...... if treated very well.

If ya batteries are in the 3 to 5 year age ...... yeh you getting bonus life and should be thinking about replacement sometime soon.

It is very much worth running a couple of equalising and resting cycles on your batteries ...... looking at your hydrometer readings ....... this my bring you some more life out of your batteries ...... or it may show the suspect cells to be on their way out.

Full points for looking at your batteries in the first place.

cheers
AnswerID: 603086

Reply By: Sigmund - Friday, Aug 05, 2016 at 10:21

Friday, Aug 05, 2016 at 10:21
Once you've done all that then do a drain test to see what the banks can actually deliver. It's the only way to be sure about their health. Voltage doesn't tell you much.
AnswerID: 603108

Reply By: henpecked - Monday, Aug 08, 2016 at 17:19

Monday, Aug 08, 2016 at 17:19
Thanks everyone for your input. I'm curious as to why Coromal fitted a PSU instead of a charger in the first place.

My thoughts when the time comes is
http://www.supercheapauto.com.au/online-store/products/Calibre-Battery-Charger-Multi-Stage-12-Volt-20-Amp.aspx?pid=213976#Recommendations
charger with SLA battery.

Regards
Ted
AnswerID: 603193

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