Charging batteries on shore power

[YANDINA]

Originally Posted by StuM

So let's just be clear about this. You are saying that lead moves from one plate to another during discharge and back again during charging. Do I have that right?

And that this lead can grow out of one spot on one plate across to the other plate?


(I won't use the words anode or cathode, since strictly speaking, it is the direction of electron flow which determines which is which and that changes between charge and discharge)

Yes, just as you can electroplate items in an electrolyte and transfer metal by putting current INTO the circuit, by using the right components you can get electrical current OUT of the process as you "unplate" it.

[StuM]

> So let's just be clear about this. You are saying that lead moves from one plate to another during discharge and back again during charging. Do I have that right?

Originally Posted by YANDINA

Yes, just as you can electroplate items in an electrolyte and transfer metal by putting current INTO the circuit, by using the right components you can get electrical current OUT of the process as you "unplate" it.

ROTFLMAO! You are completely mistaken both in your conception of how batteries work and how electroplating works.


IOW, your statements in your link are based on bad science and are "not even wrong" to use a common expression.

I must give you credit for your disclaimer however:
"This is an empirical article is based on 10 years of cruising experience, with no technical verification."

[YANDINA]

So I got the chemistry wrong but the theory is correct. I Googled it and found:

The charging reaction converts the lead sulfate at the negative electrode to lead. At the positive terminal the reaction converts the lead to lead oxide.

This confirms that there is a reversible physical change on the surface of the electrode between metallic lead and lead oxide, and that if the depth of discharge is always at the same place the material will become stratified and less uniform causing some areas to be closer to the other electrode and some further away. Concentrating the current at the high points will aggravate the situation, eventually resulting in end of life.

So even if the theory was wrong, the solution of substituting a $60 Walmart battery for my $2,000 battery bank transferred thousands of small charge/discharge cycles to a battery that Walmart replaced under warranty and saved losing another bank of batteries.

[facciatosta]

Originally Posted by YANDINA

So even if the theory was wrong, the solution of substituting a $60 Walmart battery for my $2,000 battery bank transferred thousands of small charge/discharge cycles to a battery that Walmart replaced under warranty and saved losing another bank of batteries.

But when battery is charged from the shore power does it really goes through thousands of charging cycles? Did you monitor it for extended period of time?
It should be always charged by the float voltage. Even it does goes through the cycles the currents are probably miniscule and can be neglected

[YANDINA]

Absolutely, in our situation, we had 4 electric toilets and the water pressure pump that apparently drew enough current to kick the shore power charger out of "maintenance" float voltage and trigger a short "absorption" cycle. The current these draw, especially when starting, is not insignificant and tended to always be on for the same number of seconds.

Using a cheap single starting battery substitute, we would get minimal life under these conditions that lead me to the conclusion that short cycling to the same depth each time was killing the batteries. The peace of mind to know that the big banks were on standby while at the dock and only a $60 battery was being used up was cheap insurance.

[StuM]

Originally Posted by YANDINA

So I got the chemistry wrong but the theory is correct. I Googled it and found:
This confirms that there is a reversible physical change on the surface of the electrode between metallic lead and lead oxide, and that if the depth of discharge is always at the same place the material will become stratified and less uniform causing some areas to be closer to the other electrode and some further away. Concentrating the current at the high points will aggravate the situation, eventually resulting in end of life.

Are you aware that deep cycle batteries frequently use tubes and not flat plates? Think about that. It sort of destroys your argument again.

[GordMay]

Originally Posted by StuM

Are you aware that deep cycle batteries frequently use tubes and not flat plates ...

How common are Tubular Batteries [OPzS / OpzV]?
Who makes them?

[YANDINA]

Originally Posted by StuM

Are you aware that deep cycle batteries frequently use tubes and not flat plates? Think about that. It sort of destroys your argument again.

Huh, yes and some are painted blue.

The shape of the electrodes has nothing to do with the fact that you still have alternating layers of positive and negative plates with electrolyte liquid, gel or matt between them.

[jt11791]

When I'm on shore power the battery charger is floating the house bank and supplying power for the DC electrical demands. The batteries stay fully charged, they don't go up and down 2% or any %. The only way the batteries can discharge is if there is a DC demand for more current than my charger can output (not likely as it is a 250A charger).

[sailinglegend]

Originally Posted by YANDINA

So I got the chemistry wrong but the theory is correct. I Googled it and found:

The charging reaction converts the lead sulfate at the negative electrode to lead. At the positive terminal the reaction converts the lead to lead oxide.

It might help readers if they could see the charge/discharge reactions in a formula.

This helps to explain why ‘temporary sulfation’ is the by-product of the normal chemical reactions during discharge and causes deposits of Lead Sulfate crystals to form on the lead plates. This is a very complex subject, but a very simplified explanation shows that the value of the elements Lead (Pb), Oxygen (O), Hydrogen (H2), and Sulfuric ACid (SO4) balance on each side of the equation, they just combine in a different way to form different elements.

PbO + Pb + 2H2SO4 = (discharge____><____charge) = 2PbSO4 + 2H2O

Put in plain English - during discharge:

The Lead (Pb), lead oxide (PbO) and the hydrochloric acid (2H2SO4) convert to lead sulphate crystals (2PbSO4) and water (2H2O) which dilutes the hydrochloric acid and so lowers the specific gravity.

During a ‘full charge’ the reverse happens:

Lead sulfate (2PbSO4 ) and the water (2H2O ) convert back to lead and lead oxide and sulphuric acid (PbO + Pb + 2H2SO4), so the specific gravity of the sulphuric acid returns to its original level. This is why Specific Gravity can be used to determine when a battery is fully charged.

But if the batteries are not fully charged there will be some lead sulphate crystals left on the plates! Fully recharging normally removes these crystals but if they have grown too large and hardened over even a short period of time then recharging cannot remove them. Lead Sulfate crystals that can’t be removed will cause permanent sulfation which reduces the battery’s active material and hence permanently reduces the available Ah capacity of the battery.

That’s why the advice from nearly all battery manufacturers is to fully recharge batteries as soon as possible after discharge, never leave them in a partial state of charge (PSoC). On a cruising boat this is sometimes impossible, but after maybe one week a full charge might clear all the sulfation. After two weeks an equalisation charge may be needed to break away the lead sulfate crystals but after a month permanent damage will have been done.

The important idea to take from all this is to understand what ‘fully charged’ really means, as small areas of the plates not converted back to Lead and Lead oxide will progressively reduce the capacity of the battery.

It can’t be repeated often enough - batteries are not fully charged when the float mode light comes on!

[donradcliffe]

Originally Posted by sailinglegend

It might help readers if they could see the charge/discharge reactions in a formula.

This helps to explain why ‘temporary sulfation’ is the by-product of the normal chemical reactions during discharge and causes deposits of Lead Sulfate crystals to form on the lead plates. This is a very complex subject, but a very simplified explanation shows that the value of the elements Lead (Pb), Oxygen (O), Hydrogen (H2), and Sulfuric ACid (SO4) balance on each side of the equation, they just combine in a different way to form different elements.

PbO + Pb + 2H2SO4 = (discharge____><____charge) = 2PbSO4 + 2H2O

Put in plain English - during discharge:

The Lead (Pb), lead oxide (PbO) and the hydrochloric acid (2H2SO4) convert to lead sulphate crystals (2PbSO4) and water (2H2O) which dilutes the hydrochloric acid and so lowers the specific gravity.

During a ‘full charge’ the reverse happens:

Lead sulfate (2PbSO4 ) and the water (2H2O ) convert back to lead and lead oxide and sulphuric acid (PbO + Pb + 2H2SO4), so the specific gravity of the sulphuric acid returns to its original level. This is why Specific Gravity can be used to determine when a battery is fully charged.

But if the batteries are not fully charged there will be some lead sulphate crystals left on the plates! Fully recharging normally removes these crystals but if they have grown too large and hardened over even a short period of time then recharging cannot remove them. Lead Sulfate crystals that can’t be removed will cause permanent sulfation which reduces the battery’s active material and hence permanently reduces the available Ah capacity of the battery.

That’s why the advice from nearly all battery manufacturers is to fully recharge batteries as soon as possible after discharge, never leave them in a partial state of charge (PSoC). On a cruising boat this is sometimes impossible, but after maybe one week a full charge might clear all the sulfation. After two weeks an equalisation charge may be needed to break away the lead sulfate crystals but after a month permanent damage will have been done.

The important idea to take from all this is to understand what ‘fully charged’ really means, as small areas of the plates not converted back to Lead and Lead oxide will progressively reduce the capacity of the battery.

It can’t be repeated often enough - batteries are not fully charged when the float mode light comes on!

You've got the concept, but H2SO4 is sulfuric acid, not hydrochloric (HCl). Now its time to change to LiFePO4 and learn a whole new set of rules.

[sailinglegend]

Originally Posted by donradcliffe

You've got the concept, but H2SO4 is sulfuric acid, not hydrochloric (HCl). Now its time to change to LiFePO4 and learn a whole new set of rules.

Many many thanks for the correction. I'm getting too old for all this - especially for LifePO4!

[dmkkeng]

Originally Posted by lawrence_craig

Hello all.

I have a pretty new set of Bosch 12v batteries onboard. Bought in August last year, used for about 60 cycles max, not dropping below 60% charge.

I have since been living onboard connected to shore power with a Victron Centaur charger.

Normally, the voltage from the charger sits around 13.5-13.6 volts. I assume this voltage is coming from the charger to keep the batteries topped up whilst we use the 12v services.

However, today, whilst doing some work on the 230v system, the batteries dropped to 12.4V. This suggests to me that there is either a problem with the batteries (losing charge quickly) or with the charger (not charging the batteries correctly).

Has anyone had a similar experience? Any advice?

Thanks,
Lawrence

Are the batteries Flooded Lead Cell or AGM. if they are flooded cell have you checked the electrolyte levels in the batteries? Perhaps you may also need to equalize the batteries? That is a significant drop in voltage for such a short period of time, I would estimate the battery charge level to be at 75% based on your voltage reading, unless you have a small battery bank I would expect battery voltage to be around 12.8 vdc based on the info you provided on time and current drew while the charger was turned off.

Check all your battery connections to make sure they are secure and free of corrosion and, as mentioned above your electrolytic levels if your batteries are flooded lead cells prior to investigating further. Your charger float voltage (13.5 vdc) is typical of what you would expect, this voltage should increase by a volt or so temporarily when you re-connected your battery charger, when the charger determines the batteries are fully charged it will drop back down to the float voltage.

[guyrj33]

Originally Posted by dmkkeng

Are the batteries Flooded Lead Cell or AGM. if they are flooded cell have you checked the electrolyte levels in the batteries? Perhaps you may also need to equalize the batteries? That is a significant drop in voltage for such a short period of time, I would estimate the battery charge level to be at 75% based on your voltage reading, unless you have a small battery bank I would expect battery voltage to be around 12.8 vdc based on the info you provided on time and current drew while the charger was turned off.

Check all your battery connections to make sure they are secure and free of corrosion and, as mentioned above your electrolytic levels if your batteries are flooded lead cells prior to investigating further. Your charger float voltage (13.5 vdc) is typical of what you would expect, this voltage should increase by a volt or so temporarily when you re-connected your battery charger, when the charger determines the batteries are fully charged it will drop back down to the float voltage.

The voltage level quoted in the original post is meaningless! It was not a resting voltage level reading.
There simply isn't enough information from the original poster.

[Nyaminyami]

0200 hours, moored in the marina - BOOM!
Woken to find my 12v genset battery had exploded - completely blown the top off, spraying battery acid all over the battery compartment under the steps and a fine acidic mist in the galley.(Used a bicarb solution to neutralise)
A couple of days previously I had cursorily checked the battery and the indicator had shown green and it remained permanently connected to its remote (max 3 metres away) charger drawing from 220v shore power.
Examination of the shattered battery revealed buckled plates (presumably from heat) and the (smart) charger output was only 10.9V
I have assumed that the incident was somehow caused by the charger, having become faulty, had lost its ability to measure battery charge levels and had simply continued to pump in 10.9V even though the battery, being previously held at full (float?)charge, might not be able to take any more charge.
Is this a fair assessment or am I missing something? What lessons can be learned? Are there any fail-safe suggestions out there.
Thanks in advance and greetings all, from Barcelona.