Battery Bank Configuration

[ChrisOlson]

I am kind of confused about that.
Are these in the 24V system the new batteries with the gawd awful high voltage and long duration equalization routine?

Yessir.  They do not seem to mind it at all.  They don't get excessively warm when I equalize, and I have not had to add a single drop of water to them.  I've checked the voltage on each individually during equalization and they stay within about .05 volt of one another running at 16.0 volts (Edit: just to clarify this is at 32.0 volts with the batteries in series).

After they cool down they go back to work with the rest of them and I have just not noticed a single thing going wrong with them.  With their age, those 16 volt equalizations might be doing them some good and maybe get another season out of them yet   

Yikes.
Slower is more efficient in that situation.
With six year old batteries at 1AM, I'd have been running at about half the peak MPH.
Still slower, but a better chance of getting back with dry oars.

Well, I still had the starting battery I could revert to if the main one went dead   

I restored this Backtroller 14 a few years back:





It's my favorite boat of all time.  When I tore the engine down to put the reed block in it I worked a little magic on the ports to improve cylinder scavenging and increase the port timing a bit.  Let's just say it's a pretty "strong" 40.  It goes about 44 mph with a 12" pitch prop on it.

It's the best walleye boat you could even imagine and we've taken it to Canada behind our fifth wheel camper countless times.
--
Chris

[ghurd]

I seem to recall your battery guy telling you no other battery would survive that kind of eq charging?
And you agreeing with him?

My favorite boat only happens when it's the only boat on the lake.
Then again, my LEAST favorite boat on the lake is a boat with a Chinkineese Merc, even if it is the ONLY boat on the lake.
(can't find the pics)
Not a 5th wheel within 100 miles of here, and thats maybe 5% of the lakes areas...
Notice there are no wakes, because I was not there yet...

[Watt]

Seems maybe my question was too vague or general.  I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems.  What I didn't consider was balancing, or not, the other now unbalanced 12v battery group since I assumed they were in parallel series to make the 24v system.  I had guessed the now smaller group would be in absorption longer than required because the time taken for the now larger group to complete each cycle/phase of charge.  By amp hour capacity, it seemed to me the then larger paralleled group would require more amperage at the same voltage to get through those cycles.   And due to the now resistance difference of the groups....  Anyway, thank you for your answers.   

[ChrisOlson]

I seem to recall your battery guy telling you no other battery would survive that kind of eq charging?
And you agreeing with him?

Well, like I said those batteries are old in marine deep cycle years.  I suspect if they were newer they wouldn't like it too well.  They're not getting worked as hard on my battery bank as they would if they were in the boat and I think they've gone thru two equalization cycles since I put them on there last fall.

So I dunno.  If they fail I'm not out much.  They have served well.  But they sure seem to be thriving for right now.

Seems maybe my question was too vague or general.  I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems.

Again, Watt - I just have not seen it make any difference.  Based on what I've seen I'm going to say it's perfect "safe" to put batteries with different ah capacity in parallel groups.  I'm sure some battery manufacturer might have a fit over it and say it's the worst thing ever to do that.  But I have to go by what I see that works.   
--
Chris

[Watt]

I bet you are right Chris.  Seems some of us get too wrapped up in what we read.  Sometimes a feller has gotta just get'r done.  Thanks again.

[ChrisOlson]

Just for giggles I went and took a photo of those two boat batteries and checked their voltages.  I have them in a plastic tub in case one would explode or something.





The inverters were pulling 82 amps at the time I took the photos and the wind turbines were putting out 27 amps.  So the net load on the bank was 55 amps.  Theoretically each battery in the bank (26 batteries including these two) should be delivering 4.2 amps.  I don't know if this pair is or not.  I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it.  Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.

But even so, this is where they always seem to run - about .04 volts difference from one another.

The first six years of their life they get worked pretty hard in the boat all summer.  The boat has a built-in Minnkota dual channel battery charger so they always get recharged right away when the fishing is done.  The Minnkota unit absorbs them at 14.4 volts but it has no temperature compensation on it.  For summer time temps, that's probably a good voltage for them.

When I put them on my bank in years past, we had a 12 volt system back then.  I used to absorb at 14.5 and equalize at 15.0 so they endured 5 years of that during the winter, many times being worked harder than in the boat.

If I end up getting 8-10 years out of these cheap $65 batteries then I'm going to conclude that the early demise of most deep cycle batteries is caused by inactivity and/or being undercharged.  The last thing that's happening to these poor old things is being underchanged harnessed up with my Surrettes, at the voltages I run those at.  I absorb the Surrettes at 30.0 and equalize them at 32.0 (temperature compensated).

So lets consider it The Experiment.  LOL!  As of right now, these old batteries have endured unbelievable pounding in the boat making fast runs on rough water, get pulled down to 50% or below on average 3 times a week during fishing season for six years, have been worked on my battery bank every winter since new, and they still appear to me to be pretty dang healthy.
--
Chris

[ghurd]

I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems.  What I didn't consider was balancing, or not, the other now unbalanced 12v battery group since I assumed they were in parallel series to make the 24v system.  I had guessed the now smaller group would be in absorption longer than required because the time taken for the now larger group to complete each cycle/phase of charge.  By amp hour capacity, it seemed to me the then larger paralleled group would require more amperage at the same voltage to get through those cycles.

The bold part is correct.

The spin implied is often published on the internet, but it is incorrect.

Theoretically each battery in the bank (26 batteries including these two) should be delivering 4.2 amps.  I don't know if this pair is or not.  I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it.  Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.

But even so, this is where they always seem to run - about .04 volts difference from one another.

Theoretically, it is all completely incorrect, except that the #10 may cause a voltage difference due to current flowing (in either direction).  At rest, they will be the same voltage.
This was known, and published, 20 years before Lincoln was shot.
Or about when the percussion cap was introduced to replace flintlock firearms.

get'r done?
Lets connect a 1000AH 12V battery in parallel with a 0.6AH 12V battery.
Lets run a 500W 12V load.
So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-

[ChrisOlson]

Theoretically, it is all completely incorrect, except that the #10 may cause a voltage difference due to current flowing (in either direction).  At rest, they will be the same voltage.
This was known, and published, 20 years before Lincoln was shot.

I don't know what Lincoln has to do with it, but my bank is NEVER at rest.  It is under load, or being charged, 24 hours a day, 365 days a year, unless it is disconnected for service.

Those boat batteries will (obviously) always stay at bus voltage, plus the voltage drop in the 10 gauge wire.  What I was talking about was the amps they have to deliver to meet the 55 amp net load when harnessed up with the big ones.  With 26 batteries, and all are the same size, every battery is delivering 4.23 amps to the load.  I don't know what the actual load is on this pair when I took the photos, but I know it's less than the big ones because they're smaller.

And that's why you can put batteries of unequal capacity in parallel and it don't make one bit of difference.  And taking it one step further, you can put series pairs like this in parallel with bigger series pairs and it still don't make any difference.  If you go to some "battery expert" and suggest that he'll probably start babbling about how you can't do it or you'll wreck them all.  Well .... I'm doing it and it don't wreck anything.  What WILL wreck them in short order is having unmatched batteries in series.
--
Chris

[ghurd]

I was telling people it would not hurt anything, and I was doing it many years before you had a 24V battery.

Theoreticallyeach battery in the bank (26 batteries including these two) should be delivering 4.2 amps.  I don't know if this pair is or not.  I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it.  Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.

THINK about it.

[WooferHound]

So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-

How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?

[ghurd]

So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-

How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?

That's what I said!
Apparently almost 2 centuries of physics no longer applies.

[oztules]

Or put simply.....

All things in parallel will have the same terminal voltage. (where they meet the parallel connection points)

All things in series will carry the same current.


..............oztules

[Watt]

So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-

How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?

That's what I said!
Apparently almost 2 centuries of physics no longer applies.

ghurd...  So, for the simple guy, what are you saying?

If the " think about it " statement was to be answered by me, I'd say the batteries would be equal in voltage depending on the size of wire to it and current. 

My question was about the voltage and time at that voltage.  Will the time it takes to bring the larger batteries from bulk to absorb and from absorb to float and from say float to equalize matter if that little battery is in series with a 1000ah group.  I know I wouldn't want to keep a .6 at 16v for 2 hours.  But, maybe I should. 

[ChrisOlson]

My question was about the voltage and time at that voltage.  Will the time it takes to bring the larger batteries from bulk to absorb and from absorb to float and from say float to equalize matter if that little battery is in series with a 1000ah group.

Watt, what I have seen is that it doesn't make any difference.  Equalization is a process where you overcharge the battery until the SG of the individual cells stops rising in relation to one another.  If the smaller batteries actually need equalization, then it will take the same time as the bigger ones.  If they don't need it, then disconnect them.

But the same applies to your big ones.  That's what they make battery hydrometers for, and why it's not usually recommended to run automatic, unmonitored equalization charges.  You should be checking and recording SG during equalization, and quit when the SG stops rising in the low cells.

As far as absorbing those batteries at 30.0 volts (15.0 each), I have seen zero problems with that.  I haven't had to add a single drop of water to them, nor do they get excessively warm.  If they were actually being overcharged by absorbing at 30.0 volts, they would take some water by now.

My Surrettes take a little water from service to service, but not much.  A few cc's per cell is all I've ever added at every service.  But they don't have those "maintenance free" caps on them like the boat batteries do that are designed to minimize water loss.
--
Chris

[Watt]

Hey Chris

I feel you have answered my questions and I don't want to make it sound like I was arguing or didn't believe you.  I do, believe me, believe you and appreciate your experience.  I do have my reservations regarding a big battery in parallel with a little battery but I will overcome that once I just do it and see what my results are. 


Thanks again for all your detailed help Chris.