Rejuvenate old rolls batteries

[squowse]

We've got 6 (I think) of these 6V Rolls batteries - https://www.rollsbattery.com/battery/6-cs-21p/
Theyve been discarded by previous owner, presuambly because they were becoming weak.

Any advice for how to get the most of them?
Charging voltage and current for starters?
If they need topping up is de-ionised water correct or should we be using acid?
I've got a hydrometer (somewhere) I can check the SG of the fluid.
Should I even be looking at opening them up to scrub the plates or something. I saw something on the internet about using epsom salts but the whole site seemed a bit sketchy. Maybe a high voltage is all that's needed to desulphate them?

Thanks in advance for you best advice

 

[sunshine_eggo]

We've got 6 (I think) of these 6V Rolls batteries - https://www.rollsbattery.com/battery/6-cs-21p/
Theyve been discarded by previous owner, presuambly because they were becoming weak.

Any advice for how to get the most of them?

If they have sat for an extended period, they may be permanently garbage especially if they were already degraded.

Charging voltage and current for starters?

Charge voltages are listed on the linked page. You'll likely need to invest in a 6V charger capable of 70A+. Charging these batteries at less than 70A is counterproductive.

If they need topping up is de-ionised water correct or should we be using acid?

Add distilled water only until the plates are covered. As SoC rises, the electrolyte level will rise. Filling while discharged may cause overflow during charging.

I've got a hydrometer (somewhere) I can check the SG of the fluid.

Do this first. If you can't find it, buy a new one.

Should I even be looking at opening them up to scrub the plates or something. I saw something on the internet about using epsom salts but the whole site seemed a bit sketchy. Maybe a high voltage is all that's needed to desulphate them?

Those efforts never demonstrate actual capacity recovered - simply that they'll start an engine or hold voltage. I regard them as useless. According to Battery University, those efforts are most useful to squeeze out a little more life prior to replacement.

Read the manual. Return with any questions:

https://rollsbattery.com/wp-content/uploads/2018/01/Rolls_Battery_Manual.pdf

 

[squowse]

I can charge 2 or even 4 at circa 15v 70A. I was wondering whether a more gentle charge would be better given their unused state.

I'm inclined to believe they could be returned to near new state given enough effort cleaning and rebuilding. At the end of the day it's only lead and acid? Unless someone will correct me? Obviously the liquid solution needs to be just right

 

[Bluedog225]

I’m afraid it is more complex than that.

 

[Tecnodave]

I’m afraid it is more complex than that.

Yep, way more complex........

 

[Bluedog225]

And if you pour out the current contents of the battery, you create a generational superfund site. (slight exaggeration)

 

[sunshine_eggo]

I can charge 2 or even 4 at circa 15v 70A. I was wondering whether a more gentle charge would be better given their unused state.

No. Low current generally does more harm than good.

I'm inclined to believe they could be returned to near new state given enough effort cleaning and rebuilding. At the end of the day it's only lead and acid? Unless someone will correct me? Obviously the liquid solution needs to be just right

This is magical thinking.

The lead has been damaged. The acid has been polluted.

Flooded batteries CAN perform incredibly well for very long service lives; HOWEVER, that is with continual and judicious maintenance. Once you let them go down the dark path, they are forever lost to the gods of sulfation.

 

[Tecnodave]

They are worth a lot as core value...

 

[squowse]

what happens to the lead? sulphation is just a surface build up isn't it?

 

[squowse]

I found some info here about a possible treatment. I'll find out how damaged they are.

Battery Sulfation

Causes of battery sulfation: Batteries sit too long between charges. As little as 24 hours in hot weather and several days in cooler weather. Battery is stored without some type of energy input. Undercharging of a battery to only 90% o...

support.rollsbattery.com

 

[sunshine_eggo]

The treatment is equalization charging, which is described in the battery manual that I linked. I'm guessing you didn't bother to read it.

The contents of that manual are more applicable and valuable to this situation than any Googling you can do.

 

[squowse]

I could be rude and say that "you obviously didn't bother to read the link". The voltage is higher than regular equalisation for starters. And Rolls technical have given me some other pointers as well.
I did have that manual but thanks for posting it.

 

[sunshine_eggo]

I could be rude and say that "you obviously didn't bother to read the link". The voltage is higher than regular equalisation for starters. And Rolls technical have given me some other pointers as well.
I did have that manual but thanks for posting it.

LOL. Pointing out how you could be rude while pointing out what you would if you were being rude is no different than being rude.

You may HAVE the manual, but it's clear you haven't READ it, or you're not interested in following the instructions. They are very clear and explicit with specific criteria, but you'd rather ask a bunch of strangers to see if you can find evidence to support your "belief."

I read it. I'm well aware of the 2.7V/cell as that's an industry standard. I can't tell you the number of 12V I've equalized at 16.2V. It's not always necessary for light sulfation, and that's why Rolls and some others use a lower EQ voltage for "routine" equalizations. EQ cycles are by definition stressful to cells and can lead to premature failure if done too frequently or when not necessary.

 

[Koldsimer]

I read it. I'm well aware of the 2.7V/cell as that's an industry standard. I can't tell you the number of 12V I've equalized at 16.2V. It's not always necessary for light sulfation, and that's why Rolls and some others use a lower EQ voltage for "routine" equalizations. EQ cycles are by definition stressful to cells and can lead to premature failure if done too frequently or when not necessary.

Just wondering what you would recommend to eq charge a 48v setup of 8 crown cr430 batteries. I've always eq'd at about 62.5. Do you think a 64.5 eq would help if the batteries were lightly sulfated? I know it's a fine line between under eq-ing and shedding plate material.

 

[sunshine_eggo]

Crowns are nutty. Their charge profile is pretty convoluted.

https://documents.unboundsolar.com/media/996010020-20Crown20CR43020Flooded20Battery20430Ah206v20L1620size20Specifications.pdf

3 phases:
1) Bulk: 40-100A per parallel battery to 56.88V
2) Absorption: hold 56.88V until current drops to 15A (tail current of .035C - pretty typical end-of-charge for FLA)
3) Absorption+ (my term); hold 15A for X hours until you've charged an additional 15-18% of your last discharge.

Each phase has "safety" end of charge criteria.

EQ: phases 1, 2 and 3 + an additional 4 hours beyond phase 3 at 15A EVERY 7 DAYS.
Safety end of 64.8V, but NOT required - can be implicitly exceeded.

It's a tough call. I don't claim to have more knowledge than the manufacturer, but compared to Rolls and Trojan, those recommendations are nuts... EQ every 7 days!?

If I owned Crowns, I would first:

"PLEASE CONTACT CROWN BATTERY MANUFACTURING COMPANY TO ADVISE THE SPECIFIC CHARGE TERMINATION METHOD USED." -

Given that the charge profile is essentially custom, I would look for them to advise on a traditional termination criteria, e.g., end absorption at 0.01C as that probably gets me close to the 115-118% input vs. output.

I would also hope that they would give better EQ criteria. In lieu of that, I would apply Rolls/Trojan trigger criteria for EQ:

If SG < 1.275 @ full charge OR cell SG deviation is > 0.03, then EQ. EQ per Crown instructions - 15A constant current. Would terminate at sooner of 4 hours or when all SG have returned to 1.275.

 

[squowse]

LOL. Pointing out how you could be rude while pointing out what you would if you were being rude is no different than being rude.

You may HAVE the manual, but it's clear you haven't READ it, or you're not interested in following the instructions. They are very clear and explicit with specific criteria, but you'd rather ask a bunch of strangers to see if you can find evidence to support your "belief."

I read it. I'm well aware of the 2.7V/cell as that's an industry standard. I can't tell you the number of 12V I've equalized at 16.2V. It's not always necessary for light sulfation, and that's why Rolls and some others use a lower EQ voltage for "routine" equalizations. EQ cycles are by definition stressful to cells and can lead to premature failure if done too frequently or when not necessary.

The tech at rolls specifically states to use low current which is opposite to what you've insisted. The manual doesn't specify equalisation current but it does specify 15.6 to 15.9 voltage, lower than the attempted repair charge. Not sure why you're getting so worked up about it.

 

[RCinFLA]

Discharge-> sulfuric acid from electrolyte combines with lead plate (neg plate) and lead-oxide (pos plate) to create a soft mossy like lead sulfate on plate, leaving water behind in electrolye from the sulfuric acid missing its sulphur molecule.

Charging reverses process to put sulphur with water back to sulfuric acid in electrolyte and plates lead sulfate goes back to pure lead. This all assumes the batteries have not been laying around in discharge state so the lead sulfate is now hard crystals, This is why specific gravity of electrolyte drops during discharge and rises during charging based on percent of acid in electrolyte. (see table below)

Lead sulfate left for some time without recharging creates hard crystals that will not recharge. Best you can do is a controlled overcharge (equalization) and hope the vigorous bubbling and heating will knock off the hardened sulfate crystals so lead plate surface is re-exposed. The dislodged crystals work their way to bottom of cell. If lead sulfate is not fully hardened some of it will recharge back to lead and sulfuric acid with the equalization controlled overcharging.

This at least frees up the plate surface so it can participate in cell performance. Hardened sulfate coated plate surface is insulated so inactive to normal cell operation reducing cell capacity.

Any sulfate crystals that dislodge or are left on plates lock up sulphur that cannot be recharged back to sulfuric acid in electrolyte so electrolyte specific gravity will be lower than normal.

You should get a float based hydrometer. Not one of the crappy auto parts store plastic junk units.
Before you start measure battery voltage and specific gravity for each cell. Record the readings.
Start with a normal charge cycle as manf. recommends but instead of stopping at absorb voltage (like 14.5v) keep going up to 15.5-16.5v.

This is the controlled overcharge called equalization. Leave battery caps off and expect a great deal of vigorous bubbling,. The bubbling is oxygen coming off the positive plates and hydrogen off the negative plates, so it would not be a good time to smoke a cigarette while doing the equalization. This eats up water from electrolyte so have distilled water to replenish it. Never let electrolyte drop below surface of plates as viewed down cell cap ports. As the bubbles pop they may spit some electrolyte acid around area of battery so be careful. Don't wear good clothes as they will have acid holes in them afterwards. I normally do for no more than 2 hour at the high voltage or until battery gets uncomfortably warm to touch. Let it cool back down than check specific gravity of electrolyte again to see if you have raised it any. If after three attempts you don't see any increase in SG you have gone about as far as you can go. Further equalization will just shed lead from plates contaminating electrolyte and ruining battery.

There is a semi-legit last ditch option but I am not a real believer in it. Epsons Salt will react with and dissolve lead sulfate crystals. It does contaminate electrolyte somewhat however. There are some Youtube videos with procedures for this process

 

[sunshine_eggo]

The tech at rolls specifically states to use low current which is opposite to what you've insisted. The manual doesn't specify equalisation current but it does specify 15.6 to 15.9 voltage, lower than the attempted repair charge. Not sure why you're getting so worked up about it.

LOL... not worked up. You'll just understand it all better once you actually READ the manual. You're looking for solutions to a problem you can't quantify or understand without gathering data first.

Since you seem to think this is meaningful:

"In both cases, the fact that the battery "won't take a charge" is a result of improper charging procedures which allowed the sulfate to harden. In most instances, it is possible to salvage a battery with hardened sulfate. The battery should be charged from an outside source at 2.6 to 2.7 - volts per cell and a low current rate (approximately 5 Amps for small batteries and 10-Amps for larger ones) until the specific gravity of the electrolyte starts to rise."

Let's look at the words and their meaning:

CHARGED AT (not below) 2.6-2.7V (funny how the manual specified EQ voltage is 2.65V/cell)/CELL)

You understand that voltage responds to current? If you apply 5-10A on a battery, its voltage will raise in accordance with its resistance and state of charge. If it fails to achieve 2.6-2.7V, you're not getting there, so you need to increase current.

You're thinking "low current" is the key, but it's "low current AT 2.6-2.7V."

Now what do you do? It's actually ambiguous. Once SG starts to rise, what now? It doesn't say. Do you let the voltage fall and just keep applying 5-10A? NO!!!!! NOT ON YOUR LIFE!!!! The MANUAL says that's counter productive as charge rates below 0.1C may increase the tendency for sulfation to form during charge (it even recommends 10% minimum in your link).

I'll line it out for you so you don't have to read it:

Check fluid levels. Fill only with distilled water such that all plates are covered. Do not top off cells.
Charge battery @ 0.1-0.2C (71-142A) to 7.5V.
Absorption charge at 7.5V for:
T = .042 * 710 / I where T = hours of charging and I = bulk current
Alternatively, until current drops to 0.02C (14.2A) @ 7.5V.
Once charge is completed, float for two hours at 6.75V (this allows SG to stabilize).
Check SG by drawing and expelling electrolyte 3 times, draw in a 4th time and take reading (this ensures you don't get stratified surface reading).
If SG below 1.265, EQ.

EQ:
Charge at 0.05-0.1C (35.5-71A) until 7.95V.
Hold 7.95V.
Periodically monitor SG.
Terminate EQ:
1) when battery temp exceeds 125°F (allow battery to cool and restart EQ if SG is still rising)
2) when SG stops increasing.
3) when SG > 1.265

Batteries that don't respond to the above are done for. You may need to conduct the process described in the link, but what you will find is that when the battery starts to "wake up" and SG increases, the current required to maintain the 7.95V begins to increase markedly above 5-10A. At that point, you should transition to a normal charge, or you will actually damage the battery.

 

[Koldsimer]

Some really good info in this thread. I've always thought crowns instructions were somewhat odd and probably not geared to RE applications.

 

[RCinFLA]

Low charge current won't do much for sulfation. The Rolls charging instructions are basically for a good battery and keeping it charged properly so it doesn't get sulfated.