Reviving neglected Rolls batteries

[neve]

I was recently given eight Rolls 4000 series 375 aH 6v batteries manufactured in 2005. I was told that they were used for a few years then put on a shelf. I understand that they are most likely suitable only for recycling, but since they had a 10 year warranty and a 20 year estimated service life, It is worth trying something.

I have access to a charger which will do 6 or 12V at 2,20, or 60 amps. It also has an auto mode and a starter mode which I think is 125 amps. I also have some small 12V 5A chargers.

Without any charging, the batteries range from 2.5 to 3.5 V. Even if I could get them to half their original capacity I could use them for a project I have.

I charged one at 60 amps for several hours yesterday. It got a little warm (The cables were hot) and was bubbling slightly. This morning the voltage was only 5.8. I'm going to charge it for a few more hours today at 60 amps. I could also charge them with the charger set to 12V. I tried this for a minute at 20A and the voltage came up to 7.1 while charging. I'm not sure how long or at what current I should do this.

There's a local battery shop which will drain and re-fill batteries. One thought is to drain, treat with EDTA, , flush, then re-fill with new acid. I wouldn't be doing anything with acid myself.

The project I need these for will have a constant current draw of only 3 amps @ 12V and a single 250 watt panel. The batteries are just for nights and cloudy periods.

[Wy_White_Wolf]

...The project I need these for will have a constant current draw of only 3 amps @ 12V and a single 250 watt panel. The batteries are just for nights and cloudy periods.

You'll need a bigger panel to support that load.

WWW

[Sunking]

If they are 4000 series they DO NOT have a 10 year warranty. It is 2/7 where first 2 years is free replacement, after that up to 7 years is prorated. I have no idea where you got the idea of 20 year service life. If treated with kid gloves you can get 5 to 7 years out of them.

OK if you can pump current into them they have a chance. No need to replace the electrolyte as it will not buy you anything. You only charge them until the Specific Gravity reaches 1.275 and no higher. Otherwise you will be destroying the battery.

I also agree with WWW you do not have near enough panel wattage to support the batteries if they are still good. 250 watt is not even quite enough to support 2 of the 8 batteries you have. To support all 8 would require either configuring them as 24 volt (60 amp MPPT) or 48 volts (30 amp MPPT), using a minimum 1600 watt panels.

You need a minimum 400 watts configured at 12 volt with just 2 batteries in series with a 30 amp MPPT controller, or if using a 30 amp MPPT controller and 600 watt panels. 250 is not going to cut it.

[neve]

Now that I look, I have no idea where I got those warranty and service life numbers.

Thanks for the specific gravity tip. At what rate should I put current into them, 20 or 60 amps?

I don't plan on using all the batteries with a single panel. There will be only two batteries per 250W panel. They will have an MPPT controller. In previous instrument deployments I've used four Trojan T105s with good success.

[Sunking]

[QUOTE=neve;82826] Thanks for the specific gravity tip. At what rate should I put current into them, 20 or 60 amps? In your case to revive them rate is not that important so long as it is no higher than then C/8. So for a 375 AH / 8 H = 47 amps. So 20 amps is the correct answer. What is important is the voltage and time. You want to use a precise Equalization Constant Voltage of 2.6 volts per cell. EQ voltage is to be applied for as long as it take to EQ the cells where the specific gravity is equalized. That should be no more than 24 hours.

An EQ charge is a controlled over charge and does do damage to the battery. Thus all manufactures only recommend the EQ be applied when the SPG falls outside a specific range, and the charge only applied just long enough to correct the SPG up to 24 hours max. If the batteries will not EQ in 24 hours or less they are toast.

I don't plan on using all the batteries with a single panel. There will be only two batteries per 250W panel. They will have an MPPT controller. In previous instrument deployments I've used four Trojan T105s with good success.

Still not enough. FLA especially the Trojans and Rolls have a min charge requirement of C/12, and no higher than C/8. 250 watts on a 12 volt MPPT charger can only generate at max 250 watts / 12 volts = 20.8 amps. That is only a C/18 on a 375 AH battery. C/12 is about the minimum to cause the battery acid to roll and agitate to prevent stratification, and most importantly disolve soft lead sulfate Crystals before the harden. Once hardened off you cannot disolve them. Sulfated batteries is 90% cause of premature battery failure of all batteries. Not a big problem for AGM and Gel batteries. At less than C/12 will require you to EQ more frequently, and EQ does damage. It is a trade off.

[Wy_White_Wolf]

....The project I need these for will have a constant current draw of only 3 amps @ 12V and a single 250 watt panel...

3 amp * 12v * 24 hours = 864Wh

250Watts * 4 hours *.8 (MPPT Controller) = 800Wh

Unless this is a summer time only setup your panel will not supply enough to power to cover the load.

WWW

[Cipherion]

Aspirin to revive old batteries.

Has anyone ever heard of dropping an aspirin into each cell to help revive a weak battery? Any other wives tales out there that may work?

[russ]

Has anyone ever heard of dropping an aspirin into each cell to help revive a weak battery? Any other wives tales out there that may work?

That sounds equally effective to goat urine - a waste of time

[PNjunction]

I was recently given eight Rolls 4000 series 375 aH 6v batteries manufactured in 2005. I was told that they were used for a few years then put on a shelf. I understand that they are most likely suitable only for recycling, but since they had a 10 year warranty and a 20 year estimated service life, It is worth trying something.

Yes, but that warranty and estimated service life is based on proper maintenance. Ok, you've got a science project now. Ignore the suggestion to use aspirin. Batteries develop hard sulfation, not headaches.

The problem with reviving zombie batteries, is that some tend to only look at them from a sulfation standpoint as if that is the only thing you need to repair. Even if you spend the next two years of your life trying to get rid of it (how much is your time worth?), and somehow magically get them desulfated, the one thing often overlooked is grid-corrosion, which ALSO takes place along with deep discharge sulfation. There is enough acid left even after deep discharge to eat the grids / plates and nothing on the market will repair corroded grids.

The other major issue is that your application calls for 12v and your zombies are 6v. You'll need to put them in series, and even if some amount of revival takes place, those batteries will NOT be candidates for putting in series due to severe capacity / performance imbalance. Ok, maybe now YOU will be taking the aspirins.

The project I need these for will have a constant current draw of only 3 amps @ 12V and a single 250 watt panel. The batteries are just for nights and cloudy periods.

Based on this, your best bet would be to cut your losses in recycling costs of those zombies, and just get a quality 110ah deep cycle or even a lowly marine hybrid and go from there. Perhaps your core-exchange rate alone would help pay for this quite nicely.

[thastinger]

Out of the 8, perhaps it will be possible to get 2 of them which are evenly matched, then try to reduce your load or go to 24V with 4 of them and more panel because you will totally drain them each day at 12V.

[Cipherion]

That sounds equally effective to goat urine - a waste of time

Russ - you really need some happiness in your life.

[russ]

Russ - you really need some happiness in your life.

Lots of happiness but that doesn't include going along with strange schemes that don't make sense, old wives tales or most green plans.