Mixing Battery types in 1 Bank

[sailorchic34]

Originally Posted by colemj

Did you read Calder's?

Mark

Already said I didn't.

But I read SL's posts and happen to understand the engineering behind it. Basic stuff really.

Believe it or not I've read many books on electric's and electronics, way back when tubes were still in radios, as well as complex hydraulic engineers books. That was just one of the things folks use to pay me the big bucks for, Hydraulics in piping that is, not reading.

[monte]

Originally Posted by sailorchic34

Actually even 14.4V should not cause out gassing. Either the charger was doing an equalizing or you might having a bad cell in one battery. Not uncommon.

To find the bad cell, turn off the charger and disconnect the Ground cable from each parallel battery. Lt it sit for a 1/2 hour then measure voltage at each battery with a VO meter. if both batteries have the same voltage, somewhere around 12.8V life it good. IF one battery reads low, say 12V or 11. something then you have a bad battery.

OK I have disconected shore power, turned the positive and negative isolator switches OFF. So you are saying disconnect the Negative only from each battery then check the voltage at the battery terminals after 30 mins?
Ill also check each cell with a hydrometer..

[colemj]

I wasn't arguing or questioning your hydraulics, just the specific application of that example.

I fail to see how you don't recognize that to use that analogy for any two batteries connected to a bank, the pipe connecting those two batteries is large compared to the inlet/outlet pipes. Dave's explanations were just that - while the two batteries take/give current (water) according to their inlet/outlet pipes (internal resistance), they reach equilibrium with each other fairly quickly (large internal pipe). He stated that one battery does not race to full charge and overflow, nor does one race to discharge and sit there - which would happen with a small internal pipe. He also stated that when the water tanks are empty, the amount contributed by each tank will be close to the same (he gave a 10% difference as his best guess). That can only happen if the internal pipe between the two batteries is large relative to the others.

The same points I have made, but let's say Dave is more correct than me.

Mark

[colemj]

Originally Posted by monte

OK I have disconected shore power, turned the positive and negative isolator switches OFF. So you are saying disconnect the Negative only from each battery then check the voltage at the battery terminals after 30 mins?
Ill also check each cell with a hydrometer..

You will need to disconnect the batteries from each other so they lie independent.

30 minutes will probably not be long enough - overnight would be much better. If that is an inconvenience, then just disconnect 3 of the 4 batteries and keep one on the charger running light house loads. You can do that one tomorrow.

Mark

[sailorchic34]

Originally Posted by monte

OK I have disconected shore power, turned the positive and negative isolator switches OFF. So you are saying disconnect the Negative only from each battery then check the voltage at the battery terminals after 30 mins?
Ill also check each cell with a hydrometer..

Ah you have a hydrometer, perfect. Just use the hydrometer to check the cells then.

Yes, when a cell's plates warp and touch each other they short out and will cause out gassing even at 14.4V and even lower. This causes the battery to self discharge pretty quickly.

Hard to see when the battery charger and connected and on. It will also draw down other battery's in the bank too. So by disconnecting the grounds you can isolate which battery is bad.

Generally all the batteries should be at or very close to the same charge. Varied only due to different conductor lengths, if you have unbalanced conductors. Assuming same type and age of batteries that is.

Even 1/2 hour should show a fair drop in one battery if its bad. Longer time would show more drop.

[FlyingCloud1937]

Boost charging is a throwback from old transformer chargers. That was the first part of the charge max current of the charger, until the batter hit 13.8 volts, then trickle charge at 13.8 volts until fully charged. This would take up to 40 hrs to fully charge a battery. Then it was either automatic shut off or had a spring timer.

AKA constant cookers.

13.8 is a trickle charge voltage not a float voltage.

Float voltage is not a charging voltage per say, it's a maintenance voltage. It should be no higher then necessary to maintain the self discharge rate.

Today the best chargers have a float set time, and then turn off and go into standby. Then turn back on at a voltage set point of 12.6(settable) give a quick boost, then return to float and run the time cycle again.

This uses less water, and cause less grid corrosion, and helps stop stratification.

Above is for FLA's, and AGM/Gells of course have their own voltage needs as per manufactures spec.

Lloyd

[hellosailor]

Mark-
Someone else had posted very similar (perhaps the same) illustrations of their charger's switch positions, from an English language product, recently. I notice the same problem with them: They are lousy illustrations and there's no way to tell if the black or the white portion of each "switch" is suppose to be the little bit that actually gets moved. The result being that no one can be sure of which way is on, and which way is off, and some users will definitely get that backwards.

Monte-
Your's is a new boat, with a warranty presumably? In which case I'd notify the broker and the builder, both in writing, that there appears to be a serious electrical problem resulting in the heavy odor of poisonous hydrogen sulfide gas from the batteries and asking them to correct it immediately, including replacement of the batteries. Poison gas and the risk of fire making the boat dangerously unusable and making them subject to liability.
That should motivate them to come and fix whatever the problem is fairly quickly.

As others have said it appears that your charger is actually set to the lower voltages required for gel batteries, and those voltages could only undercharge conventional wet cells, which in theory would only damage it IF that resulted in some permanent capacity loss as sulfites formed. But...

http://www.phlsci.com/support/CatPaper01.01.pdf

Check out that pdf online for some complex reading that seems to end up saying no one really knows (after 100 years?!) the complete chemistry happening in lead acid batteries. My take on it is that large amounts of H2S indicate something abnormal in the battery, which in turn could certainly could from damage from incorrect charging. I'd ask them to REPLACE the batteries and confirm proper charger operation, citing the H2S as proof that something is wrong and that's enough reason to consider the batteries as damaged or potentially damaged--a warranty issue.

Let it be their problem, not yours.

[FlyingCloud1937]

wait wait....

Before you disconnect everything.

Turn the charge source off. Then turn on a large load something on the order of 25-50% of amp hr capacity the larger the better. Run this load for at least 5 minutes.

What this will due is bleed off all of the surface charge on the plates. The larger the load the better, because it won't actually effect the SOC, because there is not enough diffusion to reach deep into the plates.

Now disconnect and run your voltage and hydro test. As this will be more indicative of actual SOC, and SOH

Lloyd

Originally Posted by sailorchic34

Ah you have a hydrometer, perfect. Just use the hydrometer to check the cells then.

Yes, when a cell's plates warp and touch each other they short out and will cause out gassing even at 14.4V and even lower. This causes the battery to self discharge pretty quickly.

Hard to see when the battery charger and connected and on. It will also draw down other battery's in the bank too. So by disconnecting the grounds you can isolate which battery is bad.

Generally all the batteries should be at or very close to the same charge. Varied only due to different conductor lengths, if you have unbalanced conductors. Assuming same type and age of batteries that is.

Even 1/2 hour should show a fair drop in one battery if its bad. Longer time would show more drop.

[hellosailor]

It can take "overnight" for the electrolyte to completely flow around and equalize the charge in a wet acid battery. You don't need to let it stand that long to get a meaningful number, but if you want to be sure, let it stand as long as you can, up to "overnight".

[monte]

Thanks again,
well its just an hour at this stage but its late in the day and Id rather have power overnight. Ill check again when I can disconnect in the morning and test in the evening, but all cells were pretty equal and batteries were 13.28, 13.28, 13.28 and 13.30
Our main charging will be solar and a victron 85/150 bluesolar MPPT to be installed as soon as this battery issue is resolved. Hopefully in a couple of days. The one battery that was slightly higher voltage was also higher when I first disconnected by about .03V. Next time ill apply a load as suggested. At this stage the inverter isnt hooked up either so its a bit hard to apply a high load

[monte]

Originally Posted by hellosailor

Monte-
Your's is a new boat, with a warranty presumably? In which case I'd notify the broker and the builder, both in writing, that there appears to be a serious electrical problem resulting in the heavy odor of poisonous hydrogen sulfide gas from the batteries and asking them to correct it immediately, including replacement of the batteries. Poison gas and the risk of fire making the boat dangerously unusable and making them subject to liability.
That should motivate them to come and fix whatever the problem is fairly quickly.

As others have said it appears that your charger is actually set to the lower voltages required for gel batteries, and those voltages could only undercharge conventional wet cells, which in theory would only damage it IF that resulted in some permanent capacity loss as sulfites formed. But...

.

Thanks, Im not sure about the "lower voltages for Gel batteries" comments though. Why are they shown as higher voltages in the manual? I now have it set at 13.4/14.1 open type/free electrolyte. Is this right?
BTW as far as warranty, they will fix it when we find the problem. Strange yes, but basically they want me to find the problem and then they will accept a warranty claim.
The voltage settings again. I now have it set on the lower voltages.

[sailorchic34]

Originally Posted by colemj

I wasn't arguing or questioning your hydraulics, just the specific application of that example.

I fail to see how you don't recognize that to use that analogy for any two batteries connected to a bank, the pipe connecting those two batteries is large compared to the inlet/outlet pipes. Dave's explanations were just that - while the two batteries take/give current (water) according to their inlet/outlet pipes (internal resistance), they reach equilibrium with each other fairly quickly (large internal pipe). He stated that one battery does not race to full charge and overflow, nor does one race to discharge and sit there - which would happen with a small internal pipe. He also stated that when the water tanks are empty, the amount contributed by each tank will be close to the same (he gave a 10% difference as his best guess). That can only happen if the internal pipe between the two batteries is large relative to the others.

The same points I have made, but let's say Dave is more correct than me.

Mark

Ah confusion...

I may have missed it but SL not taking about a internal equalizing line. Yes if there is an equalizing line (much like how cooling towers s are sometimes interconnected), then it would balance the flows between the tanks/batteries. But the conductors are not quite true equalizing, as the resistance in the conductors may be unbalanced due to end fed and different lengths of conductors.. Least in most boats I see anyway.

BTW, equalizer lines are added to cooling towers because the tower closest to the pumps would drain faster then the others. Even though all are connected with say a 12" to 16" pipe or even a 42" pipe, with all towers being the same type and flow rate into them.

The closest tower would suffer from a dry sump under flow conditions. The separate equalizer line stops that from happening. Under dynamic flow rate/ load, the towers do not flow equally into the suction header even with a 42" suction line.

The same thing happens under dynamic loads in electrical circuits though with a bit more things happening, like inductance, capacitance, etc.

Assuming 4 battery parallel bank( all same type) with +- conductors fed from one end. The first battery in the set will see a higher charge current, due to internal resistance in the conductors (wires) to the other three batteries. This as very small resistance changes impact how much current goes to each battery. Feed the 4 batteries with + from one end and - from the other, with equal conductor lengths between the batteries and the battery charge will be pretty equal and balanced, between the batteries.

In both examples above the batteries will equalize over time. But in the first example where + - feed from the same side of the bank, the end battery will not contribute as much current to loads and will tend to pull the other batteries down a bit once the charger drops to float and the batteries equalize.

Now mix old batteries and new batteries of the same type and the resistance values are even greater.

Probably clear as mud.

[sailinglegend]

Originally Posted by colemj

You know, I had a peek at Calder's book and the explanation you are citing.

He not only was discussing series cells (as I stated), he was discussing an individual cell. Like you state in your last sentence, he was describing an analogy for a high surface charge to migrate throughout a thick plate.

His analogy has nothing at all to do with with mixing batteries, or even putting two of the same type of batteries together...

And I thought that this contentious thread had ground to a halt, but you continue to see in people's writings what YOU want to see to support YOUR incorrect ideas!

Nowhere in Calder's water tank analogy does he mention CELLS in the second OR even third series of his book. He is describing exactly what you quote me as saying- 'an analogy for a high surface charge to migrate throughout a thick plate'

This applies at cell level, battery level, or bank level. All your questions and Dave's excellent analysis can be explained using this battery plate analogy.

I reported you to the moderator for continually trying to make me look stupid with your misleading and incorrect postings. Unfortunately they don't -'moderate for accuracy of content'. So all forumites should read your posts with care! Sorry I quoted their private response to me about another poster. That is an illegal manoeuvre, but readers need to understand why moderators don't moderate!

I have some good news from Interstate Batteries that confirms what all sane people have been saying about mixing AGMs and FLAs in a bank. This was a thread drift introduced by Commercial Member Andina Marie back in #60 where she contacted Interstate to try and support her YANDINA battery combiners mixing FLA and AGMs. After three emails she finally got the answer she wanted from their 'battery engineer' that mixing them was OK. We all wondered what question she finally asked their 'battery engineer'.

I sent Interstate the challenge that I posted in #57:

I challenge your, or any of your supporters out there, to find a battery or a charger manufacturer (not a battery combiner manufacturer) to say that combining AGM and FLAs permanently in a service bank is a good idea.

I also sent her posting and a link to this thread, their 'battery engineer' sent this reply:

Thank you for your inquiry here at the home office of Interstate Batteries, Inc. It is not advised to add an AGM battery to an existing flooded lead acid battery. The reason behind this would be the discharge and recharge as explained in the posting on the forum. Two different chemistries and two different internal resistances can cause a huge nightmare with possible out gassing, run times and recharge capability. Current travels the path of least resistance. Meaning, the battery with the least resistance (the AGM battery) will get all the current before it returns to the flooded batteries. This will increase the heat of the AGM bringing on out gassing and a shorter life span of both batteries.
I hope this makes sense. Let me know if you have more questions.

Thanks,
Jeff Barron
Engineering & Technical Service Specialist

A follow up email confirmed that they had no record of emails from Andina Marie and they were happy for me to quote their email:

I do not have a problem with you posting my response on the forum at all. This will get the situation under control and have the correct answer out there for all to see.

This time Andina you have pushed your 'commercial member' interests too far in trying to deceive us all, so I shall be reporting you to the moderator.

[sailorchic34]

Originally Posted by monte

Thanks, Im not sure about the "lower voltages for Gel batteries" comments though. Why are they shown as higher voltages in the manual? I now have it set at 13.4/14.1 open type/free electrolyte. Is this right?
BTW as far as warranty, they will fix it when we find the problem. Strange yes, but basically they want me to find the problem and then they will accept a warranty claim.
The voltage settings again. I now have it set on the lower voltages.

Ah, By chance is your battery charger a Xantrex. I remember the manual showing the switches where it looked opposite of how it should be set. Their diagrams were not quite clear as I recall. I had the same problem with it, till I looked closely at the diagram.

For lead acid, you want it at the 13.8 and 14.4 volt setting.

[donradcliffe]

We'll get back to mixed batteries later, but here is a good example of recommended charging voltages from Exide for their various types. I'd take a digital multimeter to the terminals and see what you are actually getting. Keeping the voltage of lead-acid batteries less tha 0.4v too high will generally not damage them quickly, but they can lose water and should be checked.

If you are smelling rotten eggs, see if one of the batteries is getting hot-it could have a shorted cell.