Battery Desulfators -- yes/no/maybe?

Brent

Anyone have any experience with pulse type battery desulfators?

I have a 48V battery bank of two strings of 8 - 6 volt batterys and they are beginning to show their age after 5 years. Best charge is around 75 - 80% of what it used to be.

SG is 1.235 after EQ and charge cycle where last year it was near 1.277. All batteries are at about the same SG.

I was wondering if the pulse type desulfators really work or is just a gimmick. Several companies make 48V desulfators for strings.

I also read that adding a small amount of Epsom salts to the electrolyte can help desulfate. Voodoo perhaps?

Any thoughts would be appreciated.

Brent

Cariboocoot

Re: Battery Desulfators -- yes/no/maybe?

If you search the forum for desulfators you'll come up with quite a bit of discussion on the topic.

The short form is that the majority believe them to be a waste of money.

waynefromnscanada

Re: Battery Desulfators -- yes/no/maybe?

It's a religion. Those who believe don't need proof, their mind is made up.
Those who don't believe would believe if there was proof.
There is no legitimate proof.
Epsom salts? Definitely not in my batteries!
Keep them properly charged on a proper regular schedule and they won't get sulfated.

Brent

Re: Battery Desulfators -- yes/no/maybe?

Thanks for the input. The batterys I have are still very serviceable but I would like to prolong their usefulness as long as possible. These batteries have been on vacation since I bought them 5 years ago. They spend their life on a float charge and get an equalization about every 2 months and a periodic bulk and abs charge and also a periodic discharge several times/year. They are only used when the power goes out and have been discharged to no more than 30% from full charge about 40 - 50 times since new. For the last 4 years they have had SG's near 1.270 and have only recently started to decline.

The caps have a dark grey paste deposit on them which I understand is an indication of some sulfation starting. I may try some longer and more frequent EQ's around 64 volts. I did several 2 hour runs recently and the SG did pickup a little.

Brent

BB.

Re: Battery Desulfators -- yes/no/maybe?

You might try discharging/cycling down to 50% state of charge a few times too... Might help shed the sulfate and expose fresh lead again.

And, discharge to what you expect the system to support (say to 40% state of charge)--If it fails to support the loads you need--Then the bank is failing for your needs.

-Bill

Cariboocoot

Re: Battery Desulfators -- yes/no/maybe?

Be advised that the desulphators allegedly work on a basis of applying Voltage @ frequency, which in essence is the same thing a solar charge controller does to regulate Voltage during Absorb and Float.

There is no scientific reason to believe they would offer any advantage over a good charging system.

BB.

Re: Battery Desulfators -- yes/no/maybe?

One or two downsides to desulfators--They make "electrical noise". May cause interference in audio/radio equipment.

And we did have one member here that had a couple of Outback MPPT controllers on a large battery bank with desulfators. Found out that the desulfators significantly reduced energy collected from the solar array (interference seem to confuse the voltage/current feedback (control) circuitry in the controllers. Once he turned off the desulfators, both Outbacks worked noticeably better.

So keep in eye on the system and make sure the desulfators do not cause secondary issues (not reported often--Just one of the "strange things" we see from time to time here). Did not appear to cause any damage--Just left the desulfator turned off/disconnected from battery bank and all was well.

-Bill

Brent

Re: Battery Desulfators -- yes/no/maybe?

Thanks for all the good info. I think I will put off the desulfator for now. If the batteries ever get to the point where the SG is really low I might try it as I would have nothing to lose.

Since my batteries are seldom discharged does it make sense to still have the charge controller do a bulk/abs each morning or would it be better to set the voltages the same as the float voltage?

Brent

BB.

Re: Battery Desulfators -- yes/no/maybe?

I guess you are Grid Tied and feeding power to the utility?

Watch the charge controllers and see if they take the battery bank much above 52 volts for an hour a day--Or if the GT system stays at ~52-54 volt volt during the day. If so, then I would not change anything.

You might think about turning off your grid power once a month or so and cycle the battery bank down by ~25% to "exercise" both the batteries and the equipment.

Unless you have "telecom" batteries that are designed for floating 99.8% of the time, your batteries will probably be healthier if you cycle them occasionally--Plus you don't want to find "problems" when you have a real power outage.

-Bill

Brent

Re: Battery Desulfators -- yes/no/maybe?

Thanks Bill,

Yes, I am grid-tied. I do a 20% discharge about every 3 months along with an EQ.

Each morning the MPPT60 charge controller charges the batteries when the sun comes up. The bulk charge voltage is set to 57.5V and usually runs about 30 min [longer if batteries are low]. Absorb voltage is at 62.0V and has a programmable time set of 45 min. Both charge voltages are recommended by the battery manufacturer.

My only concern is that I might be overcharging the batteries since they are already pretty well charged when the new charge cycle starts.

Brent

Cariboocoot

Re: Battery Desulfators -- yes/no/maybe?

This is why I dislike charge controllers with fixed Absorb times. It can be too long at the higher Voltage than the battery needs, especially in a low DOD application. Such repeated heat stress is not good for longevity.

Brent

Re: Battery Desulfators -- yes/no/maybe?

Currently I have the Absorb time set to 45 min. Unfortunately the charge controller does not automatically adjust the Absorb time like it does for Bulk.

I guess I could set the Absorb time to 1 min and not worry about it.

Brent

Cariboocoot

Re: Battery Desulfators -- yes/no/maybe?

Watch the current as it goes through Absorb and see what time span shows a significant change from the initial rate. If it goes down to and then stays at 'X' Amps in 5 minutes you don't need 50 minutes in Absorb.

Brent

Re: Battery Desulfators -- yes/no/maybe?

Good suggestion. I will try that.
Brent

Cariboocoot

Re: Battery Desulfators -- yes/no/maybe?

Just remember that if you actually do have to use them for back-up you'll have to lengthen the Absorb time again to achieve full charge.

That is the advantage the Bulk/Absorb timer used on Outback & MidNite controllers.

mtdoc

Re: Battery Desulfators -- yes/no/maybe?

Brent wrote: »

Currently I have the Absorb time set to 45 min. Unfortunately the charge controller does not automatically adjust the Absorb time like it does for Bulk.

I guess I could set the Absorb time to 1 min and not worry about it.

Brent

Do the XW CCs have the ability to end absorb based on end amps?

NorthGuy

Re: Battery Desulfators -- yes/no/maybe?

mtdoc wrote: »

Do the XW CCs have the ability to end absorb based on end amps?

Yes. However, this is not straightforward. You need to multiply your end amps by 50 then set the value as a battery bank size. Say, you want 10A. You set your bank size to 500AH. This effectively sets the end amps to 2% of 500 - 10A.