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CROWN Batteries CRO-6305 / 6v Flooded acid.

Rican

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Hi, 5-6 months ago I bought 8 of CRO-6305, 6v acid flooded batteries. The batteries have sat uncharged for about 5 months since I bought them. They have never been charged, but they arrived charged when I got them. Never charged or connected to each other, or to anything, or charger. They just been sitting there and I am afraid that they may have sustained damaged by now. Am I right? Any knowledge or experience welcome Thanks!
 
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If FLA, likely. If AGM, not likely.

Given their relatively young age, fully charging them followed by an equalization charge (if FLA) will likely improve them significantly.
 
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To give you an idea of what's possible, I had a Interstate group 24 deep cycle battery. Bought it super cheap on craigslist. It was less than 6 months old. Guy replaced it with two larger batteries in his 5th wheel and put it on a shelf in his garage. Said he charged it every couple months. I kinda doubt it.

It would barely hold 12.4V 24hr after a charge. Using chargers that actually count current input, it hardly had any capacity. A reserve capacity (RC) test (how many minutes it will supply 25A of current and stay above 10.5V) shows less than 50% of rated.

I popped the covers and hit it with a 16.2V charge until the case went over 100°F and the SG was 1.265 or higher per cell.

Let it cool and sit for 24 hours. Ran another reserve capacity test, and it tested to 86% of rated after that single treatment. Subsequent charges were typical of what one would expect.

Crown has instructions for equalization charging. I'd get them going ASAP. At a minimum, you should get them fully charged and floated to slow/minimize any further damage.
 
Hi, thanks for the knowledge and advice, I am off grid and after a year of generators I am finally getting the courage to assemble the components I bought a year ago lol, and put it all together.

So I guess that I need to charge them asap, could I charge them with a generator? Like assemble all the components and hook-up the genie to it?

I have to learn how to do that...the genie I meant, I bought the system Will suggested on his site...4000kwh, 24 volts, I have, 12- 150w panels, 2x40amp epevers, 3000w inverter, 8 FLA crown 6305 and the other components that the site suggest.

But the FLA batteries have sat for about 6 months. Thanks for the information.
 
Also, they are crown FLA batteries cro-305 not 6305...sorry about that.
 
Ideally use a regulated battery charger/maintainer, either powered by generator or a PV charge controller. That way you don't over charge them.
This will reduce further damage. But if any cells are low, they will continue to deteriorate until you perform equalization so plan to do than soon. To equalize you need a charger or other source able to deliver the specified higher voltage.

Since you have PV panels and charge controller, you could use that.
Don't suppose you have a 6V charger.
So I would sort the batteries by voltage. Pair up similar ones and put in series for 12V, two 6V batteries of similar state-of-charge. Then connect all 12V strings in parallel.
Connect charge controller (assuming good for 12V) to opposite corners of the battery bank for reasonably balanced current flow.
(There is a slightly more complicated and better way to connect 4, 12V batteries in parallel that perfectly matches them.)
Add PV panels and let become fully charged.

Do the batteries have accessible terminals between each 2V cell? If so check with volt meter.
Get a hygrometer and check density of each cell.
If imbalanced, an equalizing charge is necessary.

Does the charge controller have an equalizing function? Could use that.

Otherwise, a higher voltage power supply, battery charger, or direct wired PV panel. You have to monitor voltage, prevent it from going too high.
Or, maybe reprogram charge controller for an "absorption" charge voltage of the desired equalization voltage.
Equalization instructions will also say to monitor battery temperature, stop charging and cool when necessary.
 
Hi! Thank you very much for all the information...I am going to check and do all of that.

I have 2 Epever charge controller

Epever MPPT Solar Charge Controller 12V/24V Solar Regulator 150V 40A/30A/20A/10A​

Thanks for the help!
 
Well, finally got me a 6v charger to charge the batteries because it's taking time to build the panel rack.

Does anyone knows what's the specific gravity of a fully charge 6v, 305Ah crown battery? As read with a hydrometer?
And how many volts should it read fully charge? 6.9v?
 
If FLA, likely. If AGM, not likely.

Given their relatively young age, fully charging them followed by an equalization charge (if FLA) will likely improve them significantly.
Thanks!
 
Lead acid antimony alloy batteries have high self discharge. About 25-30% per month.

If sulfated they will charge just won't get full capacity from them. SG will not come up because of captured sulfate on plates won't charge back to sulfuric acid.

SG should be 1.28 at full charge. 1.18 is about 50%, 1.10 about 20%.
 
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"If sulfated they will charge just won't get full capacity from them."

Can FLA batteries become sulfated if they have never been charged, except for the factory charge, but then totally discharged on their own?

The antimony, selenium and the addition of arsenic is added to improve the quality of the soft lead plates.

Thanks for the info!
 
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"If sulfated they will charge just won't get full capacity from them."

Can a FLA batteries become sulfated if they have never been charged, but totally discharged on their own?

The antimony, selenium and the addition of arsenic is added to improve the quality of the soft lead plates.

Thanks for the info!

Yes.

The equalization process can partially/completely reverse "light" sulfation.

Charging and the equalization process for the Crowns is a little different than typical:


Essentially, after fully charging the battery to 7.26V and the current dropping to 12A, you are supposed to hold the 12A current for 3.5-5 hours until dV/dt flattens, i.e., voltage stops raising over time or increases negligibly.

Equalization just extends that time by 3 hours.

So, rather than a typical CC/CV charge profile, the Crowns want a CC/CV/CC profile.

Standard charge summary:
Charge to 7.26V
Hold 7.26V until current drops to 12A
Hold 12A until voltage stops increasing (about 3.5-5 hours)

For equalization, you just extend the 12A phase for an additional 3 hours.

This is likely going to be very challenging to accomplish because few chargers work like this. To equalize, you'll likely need to baby sit it and keep increasing the absorption voltage as needed to maintain 12A. Eventually, you'll find what the battery peaks at. It's likely going to be something around 8.1V - and I wouldn't personally allow it to go higher than that. Also, you should monitor battery temperature. If the battery exceeds 110°F, terminate equalization charge and allow to cool completely before additional charging.

Once you've established the equalization voltage (where 12A peaks), you can select that for future equalization operations rather than baby-sitting it.

Crown's don't say anything about float. I would personally choose 6.8V.

My supplemental recommendations are based on procedures recommended by Trojan and Rolls for their batteries.
 
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Yes.

The equalization process can partially/completely reverse "light" sulfation.

Charging and the equalization process for the Crowns is a little different than typical:


Essentially, after fully charging the battery to 7.26V and the current dropping to 12A, you are supposed to hold the 12A current for 3.5-5 hours until dV/dt flattens, i.e., voltage stops raising over time or increases negligibly.

Equalization just extends that time by 3 hours.

So, rather than a typical CC/CV charge profile, the Crowns want a CC/CV/CC profile.

Standard charge summary:
Charge to 7.26V
Hold 7.26V until current drops to 12A
Hold 12A until voltage stops increasing (about 3.5-5 hours)

For equalization, you just extend the 12A phase for an additional 3 hours.

This is likely going to be very challenging to accomplish because few chargers work like this. To equalize, you'll likely need to baby sit it and keep increasing the absorption voltage as needed to maintain 12A. Eventually, you'll find what the battery peaks at. It's likely going to be something around 8.1V - and I wouldn't personally allow it to go higher than that. Also, you should monitor battery temperature. If the battery exceeds 110°F, terminate equalization charge and allow to cool completely before additional charging.

Once you've established the equalization voltage (where 12A peaks), you can select that for future equalization operations rather than baby-sitting it.

Crown's don't say anything about float. I would personally choose 6.8V.

My supplemental recommendations are based on procedures recommended by Trojan and Rolls for their batteries.
Thank you very much! It's appreciated!
 
As @RCinFLA mentioned, specific gravity is key. While he listed 1.28 as typical fully charged batteries, there are variations. 1.265 is also common.

You may find that once the battery is fully charged based on the charge cycle, your specific gravity may be low. If it's below 1.265, I'd definitely engage in an equalization cycle. IIRC, Crown recommends them every 30 days, so given that they've sat, I think I would do it anyway.
 
When lead-acid battery discharges, sulfur from sulfuric acid in electrolyte (which is converted to water) combines with lead to form lead sulfate on lead plates.

Lead sulfate starts out as a soft purplish-brown mossy coating. If left for some time (weeks to months) it crystalizes on surface of plate. The crystalized lead sulfate will not easily split back to lead and sulfur when recharging done that normally would recombines with water to make sulfuric acid again when recharged. This is why lead acid batteries should be kept fully charged and never allowed to remain in partially discharged state for long period of time.

Besides tieing up sulfur and lead, the lead sulfate insulates the surface of lead plate so the lead behind it cannot contribute to battery capacity.

The only realistic improvement is high rate charge (called equalization) which dislodges lead-sulfate crystals allowing them to work their way to bottom of battery and at least exposes fresh lead plate. Equalization is an overcharge and is hard on battery so it should not be used too much. You still do not get much sulfur recovery to remake sulfuric acid so SG of electrolyte will not come back up to where it was before sulfation. But at least you recover some of battery's capacity by re-exposing remaining lead plate. This is why deep discharge lead acid batteries have thicker plates so they have some reserve lead and maintain physical structure of plates.

Other common failure on lead-acid battery is oxidation of grid support structure within the positive plates. Positive plate is coated with lead oxide with oxygen from water molecules. When charging, the water is split to hydrogen bubbles coming off negative plates and oxygen coming off of positive plates. The constant bathing of oxygen causes positive plate grid oxidation which reduces contact between grid and lead so the equivalent series resistance of the battery increases. This causes more terminal voltage drop when battery is electrically loaded for current. When you put a high rate of charge, including equalization, it splits up more water in electrolyte into oxygen and hydrogen gas so the water has to be replaced. The gases escape with the result of water loss in electrolyte. (also be careful about hydrogen gas build up in confined space).

Lead-acid batteries used for UPS backup on continuous float usually die due to positive grid oxidation with excessive equivalent series resistance preventing high current draw from battery.

Electrolyte level must always be maintained above top of plates so need to periodically check and add water to keep electrolyte level above plates top edge.

Deep discharge lead-acid batteries have their plate internal support grid made with antimony alloy which is stronger then calcium used for auto batteries. Advantage of calcium alloy is lower self discharge. Disadvantage of antimony alloy is greater self discharge.
 
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I have different experience with a couple dozen FLA batteries across multiple brands.

I have personally witnessed recovery of SG, and Trojan/Rolls explicitly indicate this is the goal of equalization, but it does have its limits. My cheap Trojan bank only recovered so much, but it was noteworthy.

Spot on about frequency of equalization. Crown may recommend monthly, but it should be based on SG. If SG drops below a minimum, or cells exhibit a deviation of greater than 0.03, then an equalization should be conducted. Healthy batteries that are well maintained and not too deeply cycled can go many months between equalizations.
 
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