Ok Baz, great link. Thanks. As the the old Castrol advert said oils ain't oils. Battery circuits ain't battery circuits!!!! I love simple....
Aussie Paul.
-- Edited by aussie_paul on Friday 11th of April 2014 10:40:35 PM
03_troopy said
07:49 AM Apr 12, 2014
Yes Baz's link shows the ideal way to set them up and the importance of a balanced system to prolong battery life. So if you are about to purchase multiple batteries buy identical ones to achieve this, but if you are simply wanting to utilise a second battery that would otherwise be wasted, I'd hook it up in parallel provided it was the same chemistry of course.
oldtrack123 said
04:35 PM Apr 12, 2014
Baz421 wrote:
Paul
I disagree with previous posts in that the batteries should be the same, ie identical to each other.
Internal resistance and charging/discharging can result in serious imbalance in batteries in parallel.
Also it depends how they are wired. I found this out the hard way years ago when I kept killing one of the 12V boat house batteries (in a bank of 3).
Suggest you read the attached info from the UK it explains it in simple terms so suits me.
That link is primarily aimed at high charge & discharge rates & shows the ideal set ups for any parallelled battery set up
Fig2 arrangement& is not complicated & suits the great majority of purposes
What is important is to have the same length & size cables for ALL those battery interconnections.
Regarding replacing with EXACTLY the same type, size & age batterries & some claim even brand ,well if one likes throwing their money away by all means do, that but in practise that is rarely necessary.
The biggest problem with not replacing al the batterries is that the older ones may delevop a leakage or short that discharges the newer one
IF that is not detected [by the bank quickly discharging] all the batteries in that bank will have a short life
But that can happen at any time, even with new batterries
With the normal charge & discharge rates used by the great majority of RVers, slightly lower or higher capacity batteries can be parallelled with very little problems
Of course that is within reason, one should not parallell say a 20A hr with a 100Ahr
Although in pratical use that can occur by natural aging.
CHemistry can have a bit mor eefect, butthat is more associated with the charging settings
Mainly taking care to not overcharge or possibly not equalise charge sometypesof lead acid batterries
If one is realy keen to get longest life possible, the rules are simple
DO not over discharge fot the types used if mixed consider the type that can be the least discharged as the limit ]
Use either a volt meter or a battery monitor to ensure they are not accidently overdischarged
Check the battery makers specs for charging requirements,set the charger to the requirement of the battery which has the lowest max recommended charge voltage
Check if there are any equalising requirements for all the batterries, but if any should not be equalised, make sure they are kept within THEIR recommended voltage limits
IF flooded wet cell make a point of checking the electrolyte level regularly & topping up only with distilled or demineralised water
IF that is required frequently ,there is a charging problem, could be due to overcharging, charging to fast ,.float charge level set too high .
Then one final point for long life do not excedd the make'rs recommended CHARGE rate [Amps]
DO NOT FAST charge unless the make gives some guidance
Baz421 said
09:13 PM Apr 12, 2014
oldtrack123,,, Ralph
what I should of added is that IF one battery comes up to charge quicker than the other in parallel set up (by battery characteristics ie internal resistance),,, the other one NEVER gets charged and will fail very quickly.
Plus the one that comes up to charge quickest,,, takes a major part of the load on discharge (quite often) and this shortens its life, and the cycle repeats itself.
oldtrack123 said
09:51 PM Apr 12, 2014
HI Baz
How can one come up to charge quicker than the other?
They are both/ all being charged by the same charger
Each will have the same voltage at its terminals
Each will be at the same % SOCs under normal RV use[ NOTE, percent SOC not Ahrs capacity]
The 20Ahr cannot be fully charged & say the 100Ahr only have 20Ahrs of capacity
THe problem is more pronounced [of different SOCs] when the batterries are some distance apart & with light cables & unbalanced cable resistance between the critical interconnections
Voltage drop in the cables then leads to a significant diference in charge & discharge percentage SOC
As I have said with high loads &/or very fast charging,with poorly balanced interconnections & batterries with widely varying capacities can cause some problems.But for most RV use there is no problems
In fact even IF you start with the same Ahr NEW batterries, it is very unlikely they will have exactly the same CAPACITY. but the SOC will even out
Marked Capacity & 100% SOC are not the same thing
OF more importance ensuring equal % charging/discharging is making sure the Actual Battery connections are kept clean & tight
That is were the usual problems arise & can go undetected until to late!! when one battery ,[the one with good connections] has realy copped it
PeterQ
.
-- Edited by oldtrack123 on Saturday 12th of April 2014 09:56:55 PM
-- Edited by oldtrack123 on Saturday 12th of April 2014 10:01:00 PM
Baz421 said
10:09 PM Apr 12, 2014
oldtrack123 wrote:
HI Baz
How can one come up to charge quicker than the other?
They are both/ all being charged by the same charger
Each will have the same voltage at its terminals
Each will be at the same % SOCs under normal RV use[ NOTE, percent SOC not Ahrs capacity]
The 20Ahr cannot be fully charged & say the 100Ahr only have 20Ahrs of capacity
THe problem is more pronounced [of different SOCs] when the batterries are some distance apart & with light cables & unbalanced cable resistance between the critical interconnections
Voltage drop in the cables then leads to a significant diference in charge & discharge percentage SOC
As I have said with high loads &/or very fast charging,with poorly balanced interconnections & batterries with widely varying capacities can cause some problems.But for most RV use there is no problems
In fact even IF you start with the same Ahr NEW batterries, it is very unlikely they will have exactly the same CAPACITY. but the SOC will even out
Marked Capacity & 100% SOC are not the same thing
OF more importance ensuring equal % charging/discharging is making sure the Actual Battery connections are kept clean & tight
That is were the usual problems arise & can go undetected until to late!! when one battery ,[the one with good connections] has realy copped it
PeterQ
.
-- Edited by oldtrack123 on Saturday 12th of April 2014 09:56:55 PM
-- Edited by oldtrack123 on Saturday 12th of April 2014 10:01:00 PM
Well I can tell you INPRACTICE, IN THE FIELD batteries do not charge up the same.
I had over 20 Deutz gen sets years ago that we operated in very harsh conditions -3C to +40C, and the cold starts (about 40-60 seconds cranking and sometimes longer) were every hard on batteries.
We had a dedicated battery room for charging (take batteries from same gen set to battery room) and again one would charge up in say 8 hours and another along side it in 10+ hours,,, same common rail + and -, same leads, same ambient temp,,, so why does it occur?????
Many batteries performed totally against theory and one was better than the other. call it internal resistance, manufacturing in-equality or whatever that's what happened.
Similarly my yacht had 3 in parallel,,,, they never came up to same charge equally,, that's why I posted the link as to preferred wiring.
Not interested in pedantics and long winded responses.
-- Edited by Baz421 on Saturday 12th of April 2014 10:11:24 PM
Phil C said
03:44 PM Apr 14, 2014
I can only add this to this thread, when I was in the RAAF as an avionics tech we were told that cells and batteries in paralell had to be the same capacity. However we only dealt with lead acid and nicads these new fangled batteries are beyond me, the ones I have in my van can only be discharged to 50% rated capacity, so I ask why call them 110AH? why not 55AH? I dont get it......
Baz421 said
09:46 PM Apr 14, 2014
Phil C wrote:
I can only add this to this thread, when I was in the RAAF as an avionics tech we were told that cells and batteries in paralell had to be the same capacity. However we only dealt with lead acid and nicads these new fangled batteries are beyond me, the ones I have in my van can only be discharged to 50% rated capacity, so I ask why call them 110AH? why not 55AH? I dont get it......
Same principles still apply but as I said in practice you don't get 2+2 =4 with batteries,,, you get 2+2= 3.7 or 4.2 or 4.4 depends a lot on each individual battery.
We had the same batch batteries at Pt Cook (you'll know where that is Phil) perform very differently,, some lasted ages some lasted weeks,,, coupled together in gensets. work it out????
Similarly with tyre on a fleet of buses 1 would cost 0.001 cents per kilometre and another 3 times that, same production run.
Theory is good but practice tells the truth IMHO.
PS Love your avatar,,,,, makes you look "alert" and you know we still need more "lerts",,, old RAAF saying from early 70's.
When running batteries in parallel do they each need to be the same amp hour?
Aussie Paul.
HI Ditto
PeterQ
Ok, thanks.
Aussie Paul.
Paul
I disagree with previous posts in that the batteries should be the same, ie identical to each other.
Internal resistance and charging/discharging can result in serious imbalance in batteries in parallel.
Also it depends how they are wired. I found this out the hard way years ago when I kept killing one of the 12V boat house batteries (in a bank of 3).
Suggest you read the attached info from the UK it explains it in simple terms so suits me.
http://www.smartgauge.co.uk/batt_con.html
Ok Baz, great link. Thanks. As the the old Castrol advert said oils ain't oils. Battery circuits ain't battery circuits!!!! I love simple....
Aussie Paul.
-- Edited by aussie_paul on Friday 11th of April 2014 10:40:35 PM
HI Baz
That link is primarily aimed at high charge & discharge rates & shows the ideal set ups for any parallelled battery set up
Fig2 arrangement& is not complicated & suits the great majority of purposes
What is important is to have the same length & size cables for ALL those battery interconnections.
Regarding replacing with EXACTLY the same type, size & age batterries & some claim even brand ,well if one likes throwing their money away by all means do, that but in practise that is rarely necessary.
The biggest problem with not replacing al the batterries is that the older ones may delevop a leakage or short that discharges the newer one
IF that is not detected [by the bank quickly discharging] all the batteries in that bank will have a short life
But that can happen at any time, even with new batterries
With the normal charge & discharge rates used by the great majority of RVers, slightly lower or higher capacity batteries can be parallelled with very little problems
Of course that is within reason, one should not parallell say a 20A hr with a 100Ahr
Although in pratical use that can occur by natural aging.
CHemistry can have a bit mor eefect, butthat is more associated with the charging settings
Mainly taking care to not overcharge or possibly not equalise charge sometypesof lead acid batterries
If one is realy keen to get longest life possible, the rules are simple
DO not over discharge fot the types used if mixed consider the type that can be the least discharged as the limit ]
Use either a volt meter or a battery monitor to ensure they are not accidently overdischarged
Check the battery makers specs for charging requirements,set the charger to the requirement of the battery which has the lowest max recommended charge voltage
Check if there are any equalising requirements for all the batterries, but if any should not be equalised, make sure they are kept within THEIR recommended voltage limits
IF flooded wet cell make a point of checking the electrolyte level regularly & topping up only with distilled or demineralised water
IF that is required frequently ,there is a charging problem, could be due to overcharging, charging to fast ,.float charge level set too high .
Then one final point for long life do not excedd the make'rs recommended CHARGE rate [Amps]
DO NOT FAST charge unless the make gives some guidance
oldtrack123,,, Ralph
what I should of added is that IF one battery comes up to charge quicker than the other in parallel set up (by battery characteristics ie internal resistance),,, the other one NEVER gets charged and will fail very quickly.
Plus the one that comes up to charge quickest,,, takes a major part of the load on discharge (quite often) and this shortens its life, and the cycle repeats itself.
HI Baz
How can one come up to charge quicker than the other?
They are both/ all being charged by the same charger
Each will have the same voltage at its terminals
Each will be at the same % SOCs under normal RV use[ NOTE, percent SOC not Ahrs capacity]
The 20Ahr cannot be fully charged & say the 100Ahr only have 20Ahrs of capacity
THe problem is more pronounced [of different SOCs] when the batterries are some distance apart & with light cables & unbalanced cable resistance between the critical interconnections
Voltage drop in the cables then leads to a significant diference in charge & discharge percentage SOC
As I have said with high loads &/or very fast charging,with poorly balanced interconnections & batterries with widely varying capacities can cause some problems.But for most RV use there is no problems
In fact even IF you start with the same Ahr NEW batterries, it is very unlikely they will have exactly the same CAPACITY. but the SOC will even out
Marked Capacity & 100% SOC are not the same thing
OF more importance ensuring equal % charging/discharging is making sure the Actual Battery connections are kept clean & tight
That is were the usual problems arise & can go undetected until to late!! when one battery ,[the one with good connections] has realy copped it
PeterQ
.
-- Edited by oldtrack123 on Saturday 12th of April 2014 09:56:55 PM
-- Edited by oldtrack123 on Saturday 12th of April 2014 10:01:00 PM
Well I can tell you INPRACTICE, IN THE FIELD batteries do not charge up the same.
I had over 20 Deutz gen sets years ago that we operated in very harsh conditions -3C to +40C, and the cold starts (about 40-60 seconds cranking and sometimes longer) were every hard on batteries.
We had a dedicated battery room for charging (take batteries from same gen set to battery room) and again one would charge up in say 8 hours and another along side it in 10+ hours,,, same common rail + and -, same leads, same ambient temp,,, so why does it occur?????
Many batteries performed totally against theory and one was better than the other. call it internal resistance, manufacturing in-equality or whatever that's what happened.
Similarly my yacht had 3 in parallel,,,, they never came up to same charge equally,, that's why I posted the link as to preferred wiring.
Not interested in pedantics and long winded responses.
-- Edited by Baz421 on Saturday 12th of April 2014 10:11:24 PM
Same principles still apply but as I said in practice you don't get 2+2 =4 with batteries,,, you get 2+2= 3.7 or 4.2 or 4.4 depends a lot on each individual battery.
We had the same batch batteries at Pt Cook (you'll know where that is Phil) perform very differently,, some lasted ages some lasted weeks,,, coupled together in gensets. work it out????
Similarly with tyre on a fleet of buses 1 would cost 0.001 cents per kilometre and another 3 times that, same production run.
Theory is good but practice tells the truth IMHO.
PS Love your avatar,,,,, makes you look "alert" and you know we still need more "lerts",,, old RAAF saying from early 70's.
Cheers Baz