|
|
19-03-2018, 07:40
|
#1
|
Registered User
Join Date: Sep 2011
Location: South East Asia
Boat: Amel Euros 41
Posts: 92
|
Different current from house bank batteries
Hi,
I have 3 x 12V batteries in parallel. When turning on a few consumers I have measured how much current is leaving each battery.
1. 4.0 A
2. 1.2 A
3. 4.4 A
If I understand correctly this indicates that the internal resistance of the 2nd battery is higher then of the 1st and 3rd so it is more aged. (The batteries are 5 years old). I would like to delay replacing the batteries till next season. What should I do? I suspect that having all 3 connected together is worst then only having 1 + 3. Should I consider the 2nd battery dead and disconnect it? (and leave with the less battery capacity)?
|
|
|
19-03-2018, 08:44
|
#2
|
cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
|
Re: Different current from house bank batteries
A proper load test on each would be a more accurate measure of SoH.
Were they all purchased at the same time? I assume the same model.
A bank made up of paralleled strings have inherent balancing issues, but 3 is often given as a safe maximum.
If the one is really that much worse than the others, I would probably replace all three sooner than later.
Worst case, go to a 2-batt bank and put in a reserve one, possibly using the "bad" one if it's not too bad. But don't just buy one new one now planning to mix it with others purchased later.
Obviously keeping everything fully charged as often as possible becomes more critical.
|
|
|
19-03-2018, 09:03
|
#3
|
Moderator Emeritus
Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 5,486
|
Re: Different current from house bank batteries
It could also be that the wiring is not balanced for the cells. If your feeding plus and minus from the same side that can cause different resistances in the wires which effect which battery works harder.
You can swap two battery's and re read the current to check that. Ideally Plus is taken off in one direction/end and Minus is taken off at the far end of the bank, which equal length interconnects.
|
|
|
19-03-2018, 09:11
|
#4
|
cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
|
Re: Different current from house bank batteries
|
|
|
19-03-2018, 09:16
|
#5
|
Registered User
Join Date: Dec 2017
Location: Acworth, GA
Posts: 97
|
Re: Different current from house bank batteries
Quote:
Originally Posted by john61ct
Yes, the incorrect pattern is very often found online.
This is correct:
|
Updated link to make it an image.
|
|
|
19-03-2018, 17:49
|
#6
|
Registered User
Join Date: Mar 2013
Location: South Jersey
Posts: 361
|
Re: Different current from house bank batteries
The center battery is reading low? have you cleaned all your connections? has one battery used more or less water than the others? are they all the same resting voltage?
|
|
|
19-03-2018, 19:04
|
#7
|
Registered User
Join Date: Sep 2011
Location: South East Asia
Boat: Amel Euros 41
Posts: 92
|
Re: Different current from house bank batteries
I have all the + and - line connected to the same point with heavy same length cables.
Will do some more testing
|
|
|
20-03-2018, 08:18
|
#8
|
Registered User
Join Date: Dec 2014
Location: the Med
Boat: Nauta 54' by Scott Kaufman/S&S - 1989
Posts: 1,180
|
Re: Different current from house bank batteries
Disconnect one battery at a time, and check for a set of 2
Be sure that contacts are similar,and ok.
Also V at rest will tell you if a bad battery draws from the other two.
V is about the state of battery, A draw may depend on some few more factors (oxidized wires you can't see...)
|
|
|
20-03-2018, 08:31
|
#9
|
cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
|
Re: Different current from house bank batteries
Quote:
Originally Posted by rotorman
I have all the + and - line connected to the same point with heavy same length cables.
Will do some more testing
|
I hope not literally the same point.
Do you mean to posts on the same battery?
Or are you wired as per the diagram just above?
|
|
|
20-03-2018, 08:36
|
#10
|
Registered User
Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 10,208
|
Re: Different current from house bank batteries
Quote:
Originally Posted by rotorman
Hi,
I have 3 x 12V batteries in parallel. When turning on a few consumers I have measured how much current is leaving each battery.
1. 4.0 A
2. 1.2 A
3. 4.4 A
If I understand correctly this indicates that the internal resistance of the 2nd battery is higher then of the 1st and 3rd so it is more aged. (The batteries are 5 years old). I would like to delay replacing the batteries till next season. What should I do? I suspect that having all 3 connected together is worst then only having 1 + 3. Should I consider the 2nd battery dead and disconnect it? (and leave with the less battery capacity)?
|
Your suspicions are correct! I would bet you can get to next season eliminating the bad one. You may have to watch your usage.
|
|
|
20-03-2018, 08:44
|
#11
|
Registered User
Join Date: Dec 2014
Posts: 600
|
Re: Different current from house bank batteries
Quote:
Originally Posted by sailorchic34
It could also be that the wiring is not balanced for the cells.
|
thats my thinking too, and its very common
out of a bank of three batteries, power ought be distributed from the middle one
__________________
'give what you get, then get gone'
|
|
|
20-03-2018, 09:26
|
#12
|
Registered User
Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 10,208
|
Re: Different current from house bank batteries
I don't by the wiring. Paralleled batteries are electrically the same no matter where the taps are. As long as the wire ga. is sufficient connecting them.
|
|
|
20-03-2018, 09:34
|
#13
|
Registered User
Join Date: Sep 2013
Location: Montreal
Boat: Dufour 39 Frers
Posts: 402
|
Re: Different current from house bank batteries
Quote:
Originally Posted by Cadence
I don't by the wiring. Paralleled batteries are electrically the same no matter where the taps are. As long as the wire ga. is sufficient connecting them.
|
I totally agree in that too. Electrons motion follows simple rules.
I would make sure also there is no hidden resistor in the connection such as corrosion.
|
|
|
20-03-2018, 09:59
|
#14
|
Registered User
Join Date: Mar 2015
Location: Boston's North Shore
Boat: Pearson 10M
Posts: 839
|
Re: Different current from house bank batteries
I suggest cleaning ALL of the connections to the underperforming battery and testing again.
|
|
|
20-03-2018, 10:01
|
#15
|
cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
|
Re: Different current from house bank batteries
So much wrong in the last few posts.
Look at the source of the diagram I posted, read the whole site, lots of good learning there from Maine Sail, to say a very experienced professional is understatement.
Obviously some bits may be expensive overkill for small boats or those on a budget, but they're very solid on the fundamentals
which **are** both real, and important.
|
|
|
|
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Rate This Thread |
Linear Mode
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
Advertise Here
Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
Vendor Spotlight |
|
|
|