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Old 26-12-2019, 17:06   #1
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Battery Woas

Given some of the recent battery threads I thought I might share my current ongoing battery misery. Maybe the electrical nerds like myself will enjoy the tribulations.
First, in relation to this post the terms 'good' and 'bad' are relative to my situation only.
BOTH BATTERIES ARE BAD
Per the pic, my house bank in the motorhome consists of two group 31 925 amp semi truck batteries (which served as the house bank in Adeline)
On the left is the good battery, on the right is bad. If you look close you can see the g and b professionally sharpied on them. I must apologize as I forgot for measure voltage drop before disconnecting the parallel ground :: I do however remove the batteries almost weekly to charge them so connections are clean regularly and I am 99.99% sure voltage drop is not a charging or discharging issue.
The left(g) battery holds a higher charge and will outlast the right(b) everytime, individually.
I charged the set yesterday for three hours 13.4v@10amps (8.9 actual) with the charger clamped to the L battery. Only 1.9amps were feeding to the R battery. After charge voltage was 12.3 measured at all points.
Removing the parallel reveals the L(g) battery is 12.3, the R(b) is 12.4.
Charging by itself today (2+hrs 13.4v@6.7amps) the bad battery was 12.8, which dropped to 12.4 in 60 minutes. Cells 2 and 4 boil heavy, 1, 3, and 5 lightly, and 6 you can see movement but never a bubble.
The good battery, following the same charge, 2+hrs 13.4v@3.8amps reads 13.4, 12.7 after 60 minutes. By itself 5 of 6 cells boil normally, 1 seldom emits a bubble(barely charging). When hooked parallel with the bad battery, charged voltage would never exceed the nominal voltage of the bad battery, in fact it measures just under the voltage of the bad battery.
Just disconnecting the batteries and testing shows the 'good' battery at a lower voltage than the 'bad' one. It was taking 6 amps while the bad one was taking less than 2, seemingly taking the bulk of the charging and testing less voltage. Logical to assume it was the weaker battery.
Isolated charging and testing revealed the exact opposite. This demonstrates that when connected with others, the battery showing symptoms might not be the battery causing the problem. It's important to isolate, charge, test, and monitor each battery.

Regardless of today's readings, both left sitting will be dead in short order, g in about a month, b in a couple weeks. (By dead I mean no longer turn on lights) Surprisingly, the 12.4 dead battery will hold that voltage quite a while burning the 12v interior lights. Both were left in Adeline in North Carolina for a year, one came home reading 3v, the other 1v. Both had 3 dead cells, charging in series 24v@10amps for 24hrs brought back two cells in one, with some life in the last cell, but not much. It revived 1 cell in the other with some life in the other two, but barely. Only the 'good' one will be going back in this time.
I'm at the point I forgot why I started this post, so I think I will go put the bad one back on charge overnight just to have something to do. And...maybe re-label them as bad and really bad.Attachment 205684
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Old 26-12-2019, 17:58   #2
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Re: Battery Woas

From what I could gather from your post I’d suspect bad and really bad.
The attachment doesn’t work, but I’d suppose neither is a deep cycle battery, and I question your charging voltage as well assuming flooded batteries.
It seems low
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Old 26-12-2019, 18:11   #3
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Re: Battery Woas

I suspect massive sulphation due to neglect and chronic under-charging. Assuming they are wet cells, try charging at 14.4V for a couple of days, then up the voltage to 15.5V for about 16 hours. Good ventilation and replace H2O if/when necessary. Might be too far gone though. Charge voltage of 13.4V is nowhere near enough for any nominal 12V battery that I know of. Of course, I have frequently been known to be wrong!
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Old 26-12-2019, 18:14   #4
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Re: Battery Woas

https://www.reactiongifs.us/wp-conte...l_ted_whoa.gif
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Old 26-12-2019, 20:52   #5
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Re: Battery Woas

a64pilot - perhaps you could help me understand why I dont have an option to edit my original post please.
As for the batteries: I only have a Schumacher manual multi-volt charger at the moment. It doesn't 'act' like a true manual charger though. The settings are 5 or 10 amp, but the charger does not seem to force it, if the battery will only take 3amps, that is what the charger feeds it. I know hooking to a drained but otherwise good battery it gives slightly over 10amps. The voltage is the same way, sorta. When the batteries are parallel the charger will not exceed 13.4, (works fine 14.4 +/- with good batteries parallel) In the last hour it raised to 14.4v@5.4amps charging the really bad battery that seems to have only 3 working cells. It's set on 12v@10amp.
The batteries are FLA specifically for semi trucks, they provide starting power and the reserve power to the truck interior when engine isn't being run. While they are sold with description of being deep cycled I highly doubt they are true deep cycle. For a 925ca battery, when new they seemed to have no end to reserve.
Pretty much DefinitelyMe nailed it, I purchased 3@$50 each (brand new!!) But could only fit two in my crab boat. That boat was repossessed when the private seller found someone who offered more days before first payment was due, so the batteries sat for a couple years with very little use. Tried to keep them charged but they got neglected bad. One was ruined completely. When we got the DeFour only one would fit so I rotated them, but they repeatedly were drained to 2-3v. Yes, abused, neglected, deeply drained, and infrequent charging. Guilty as Charged!!
Really I think my original post was more just for sharing the sometimes odd symptoms that can happen when batteries are tied together being drained and charged. Also how different a battery can respond if charged by itself. As noted the battery that will actually charge to full voltage will not do so when in a parallel circuit with the battery that will not charge above 12.4. For some reason it will only charge at about 13.4v but holds full voltage after the charge. The battery that will not hold the charge accepts 14.4 while charging alone.
This is why I always suggest isolating and charging/testing separately when diagnosing multiple batteries in a bank.
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Old 26-12-2019, 21:41   #6
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Re: Battery Woas

Get a new charger. You need to charge them at 14.4v +.

The batteries at 12.4v are not charged yet.

Even a weak battery will still charge to full voltage 12.8v. It will just drop sooner when used.

A dead cell is different.

Once they are fully charged. You can do a 20h discharge test to test their capacity
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Old 26-12-2019, 22:05   #7
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Re: Battery Woas

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Originally Posted by smac999 View Post
Get a new charger. You need to charge them at 14.4v +.

The batteries at 12.4v are not charged yet.

Even a weak battery will still charge to full voltage 12.8v. It will just drop sooner when used.

A dead cell is different.

Once they are fully charged. You can do a 20h discharge test to test their capacity
I don't believe it's the charger, when they were used as the house bank in our sailboat we had similar issues with two other chargers, especially when they were in parallel. Charger works normally with other batteries.
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Old 26-12-2019, 22:09   #8
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Re: Battery Woas

Battery charger amp rating is a max capability, not a defined charge rate. There is bound to be an exception or two out there, but by and large, small automotive chargers just don't do the job. With near certainty I can say that the batteries in question have suffered from chronic undercharging (2nd-ing earlier comment).

The 'bad' battery has one shorted cell, the one observed with no activity under charge. It's toast, and a battery that's been left flat dead for a year is toast.

The charger capacity is not quite adequate for even one of those batteries. The distribution of current between the two charging in parallel is of no relevance when the voltage is only reaching 13.4. The battery with the lower state-of-charge takes the higher share of the available current. A battery with a shorted cell will take more current than normal.

Adeline needs new batteries and a better charger. Charger capacity should be 15% of the combined amp-hour rating, which is around 110 for a GP31. 20 Amps minimum, 25 better, 30 good. In round figures, the batteries are charged when the voltage is 14-14.4V and the current is 2% of amp-hour rating or less.
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Old 26-12-2019, 22:33   #9
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Re: Battery Woas

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Originally Posted by EngNate View Post
Battery charger amp rating is a max capability, not a defined charge rate. There is bound to be an exception or two out there, but by and large, small automotive chargers just don't do the job. With near certainty I can say that the batteries in question have suffered from chronic undercharging (2nd-ing earlier comment).

The 'bad' battery has one shorted cell, the one observed with no activity under charge. It's toast, and a battery that's been left flat dead for a year is toast.

The charger capacity is not quite adequate for even one of those batteries. The distribution of current between the two charging in parallel is of no relevance when the voltage is only reaching 13.4. The battery with the lower state-of-charge takes the higher share of the available current. A battery with a shorted cell will take more current than normal.

Adeline needs new batteries and a better charger. Charger capacity should be 15% of the combined amp-hour rating, which is around 110 for a GP31. 20 Amps minimum, 25 better, 30 good. In round figures, the batteries are charged when the voltage is 14-14.4V and the current is 2% of amp-hour rating or less.
I agree with almost everything, however I do not have a small automotive charger. This unit was designed to charge 6x12v batteries at once, either in parallel or series, or up to 12x6v batteries in series(grouped in twos). It takes our 36v golf cart series (6x6v) from completely dead to fully charged in just over six hrs, the factory charger was almost twice that. As I mentioned it is odd, as three chargers and two alternators all appeared to lower voltage to accommodate these two batteries. I would say that is impossible, but I am reading the numbers myself.
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Old 26-12-2019, 23:37   #10
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Re: Battery Woas

The edit function is only available for a short period.
I believe the charge voltage is low due to the charger being so small, it’s only 10 amp, and 10 amps only gives you 13.4V, a larger charger will give you proper voltage
But the batteries are I believe toast. 10 amps into shorted cells equals 13.4 V, the shorts eat the 10 amps, nothing left for charging.

A larger charger would carry higher voltage, and due to them being shorted would probably overheat them too.
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Old 27-12-2019, 04:15   #11
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Re: Battery Woas

Quote:
Originally Posted by S/V Adeline View Post
I agree with almost everything, however I do not have a small automotive charger. This unit was designed to charge 6x12v batteries at once, either in parallel or series, or up to 12x6v batteries in series(grouped in twos). It takes our 36v golf cart series (6x6v) from completely dead to fully charged in just over six hrs, the factory charger was almost twice that. As I mentioned it is odd, as three chargers and two alternators all appeared to lower voltage to accommodate these two batteries. I would say that is impossible, but I am reading the numbers myself.
Just because the advertising blurb says a charger can charge 6 batteries at once does not mean it actually can.....

Average golf cart battery is ~230AH... assuming you’re charger could pump in it’s 10 amps continuously (it can’t) it would take a minimum of 32 hours for it to charge them from “completely dead to fully charged”
If it’s only supplying 13.4v to a 12v lead acid battery it can fully charge it, but will take a very long time.

As such, I believe your batteries have never been fully charged. You may even have a corrupted view on what fully charged actually means (no insult intended)

A fully charged lead acid battery has a resting open circuit voltage of ~12.8v (varies based on lead alloy composition)
At 12.4v rested open circuit voltage, it’s at 50% at best, probably less....

A 12 volt lead acid battery that you bought home at 1v or 3v open circuit voltage needs to be replaced, they aren’t worth the effort to recover and will be very low capacity and quite unreliable.
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Old 27-12-2019, 07:02   #12
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Re: Battery Woas

There seems to be cherry picking in what people read, so I will try again. Three separate chargers drop voltage when hooked to these batteries WHEN THEY ARE IN PARALLEL. Two alternators (according to line voltage readings at the alternator and battery) did the same.
Maybe I didn't state that clearly, but all the chargers operate normally when hooked to good batteries. As stated in the initial post both batteries are essentially bad to begin with and the post was intended to demonstrate the need to isolate and diagnose batteries one at a time.
For the golf cart, there is a voltage cut off when it drops to a certain level, to prevent overdrawn batteries, 'dead' was referring to that point, semantics
For anyone truly interested in the oddities of FLA cells, in moving the worst battery out of the motorhome I must have shook something lose banging it around, as it is now taking over 14.5v and all cells are actively accepting a charge !? I might get a couple more months out of it yet.
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Old 27-12-2019, 07:13   #13
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Re: Battery Woas

A dead cell will soak up the available current and will keep a small charger from ever reaching its voltage. Think about it, connect a charger and voltage stays roughly the same, then over hours slowly climbs, but if something is using the current the voltage will never climb.

Yes you likely did shake something loose, it’s called mud, mud is what sloughs off of the lead plates and can build up on the bottom of a cell and eventually short it out. Most likely it will short again soon.

Your batteries have most likely been dead for a long time, but you have adapted to their greatly reduced capacity and gotten by, eventually of course one or both will completely quit, some nurse batteries until that happens, and that’s fine so long as they don’t really depend on them and are where new batteries can be bought.

When in Germany I “nursed” a dead battery in my old Mercedes, parking on hills, and carrying cables, cause a new battery cost many times more than they did in the US, and I didn’t want to pay that much for a car that I wouldn’t own in a Year.

Decades ago I would take a dead battery drain it and put it on a expanded metal table I had upside down and flush it out with water attempting to flush the mud out, I’d then fill it with fresh acid and charge it.
I’d often get another year or two out of it in a tractor etc.
But that’s junk yard maintenance and I was doing it more just to see if it would work.
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Old 27-12-2019, 09:09   #14
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Re: Battery Woas

Post the make and model of the charger(s) so we can have a read of the manual.
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Old 27-12-2019, 17:44   #15
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Re: Battery Woas

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Originally Posted by S/V Adeline View Post
I only have a Schumacher manual multi-volt charger at the moment. It doesn't 'act' like a true manual charger though. The settings are 5 or 10 amp, but the charger does not seem to force it, if the battery will only take 3amps, that is what the charger feeds it. I know hooking to a drained but otherwise good battery it gives slightly over 10amps. The voltage is the same way, sorta. When the batteries are parallel the charger will not exceed 13.4, (works fine 14.4 +/- with good batteries parallel) In the last hour it raised to 14.4v@5.4amps charging the really bad battery that seems to have only 3 working cells. It's set on 12v@10amp.
None of this has anything to do with the equipment, that's how charging lead works.

A charge source only makes current available. The actual rate is determined by the demand from the load, battery in this case - acceptance rate, resistance, SoC level, Ah capacity are all factors.

Same with the voltage level, the charge source is only "striving" to bring a thirsty battery up to the profile setpoint during the Bulk / CC stage, not under its control but by the battery factors as above.

A higher available current with a high-CAR chemistry will get to the CV / Absorb stage faster, maybe two hours rather than five, but will then need to hold CV longer, maybe four hours rather than one.

Those batteries are definitely not suitable for true deep cycling usage, load test to see their current SoH, at 70-80% replace with better. But I'd bet only scrap at this point.

At some point get a proper marine charger too.

And only put matching healthy batteries together to create a bank.
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