Desulfator; do I need one?

[john]

I have 4 100 amp hr batteries(lead acid ) and two panels (100w and 120w) I seem to notice some voltage drop over the last year 13.2 down to 12.9. Is a desulfator necessary and/or worth it.Thanks for any help

[Mike90250]

Maybe.


With good battery maintenance, you are not supposed to need a desufator.

That said, I use one myself, only burns about 15W, and with a used battery bank,
maybe it will help.
desulfater:

http://www.facebook.com/photo.php?pid=31078084&l=94e4bd40ec&id=1196643274

whole album

http://www.facebook.com/album.php?aid=2030956&id=1196643274&l=56e4b57d3e

[john p]

My answer if you can get one at a good price use it. Even it does only a little bit of good thats better than none and there is NO EVIDANCE FROM ANYONE it can do harm. You can also find pulsed battery chargers that do about the same thing.
Why its very hard to give a totally accurate answer to this asked a million and six times question.. its impossible to do a test on two sets of batteries under exact same conditions.. Even differences between the same type battery from the same manufacturer will give different results.. ie incandesant light bulbs, get 2 from same maker then turn both on . one will fail mabe a very long time before the other .

[Sunking]

Even it does only a little bit of good thats better than none and there is NO EVIDANCE FROM ANYONE it can do harm.

On the flip side there is no creditable evidence they do any good. IMHO it is just a marketing mumbo-jumbo.

What I can tell you is your low voltage is not from lack of a desulfator, but a lack of proper battery maintenance and/or abuse.

One thing that caught my eye right away is it appears you do not have near enough panel wattage to properly maintain the batteries you have now assuming the batteries are used daily in cycle service.

I assume when you say 400 AH it is at 12 volts? With only 220 watts of panel wattage the most current you can push is 17 amps or a C/23 charge rate. Typically solar systems run at C/15 up to C/8 charge rates. You are well below that rate.

[john p]

Mabe the first question we should have asked him is what type of batteries he has ?
second question their age?
I agree that 220 watts of panels is not enough in most cases for 400ahr batteries
220 w panels and about 200ahr battery is a more reasonable match

[john]

undercharge

On the flip side there is no creditable evidence they do any good. IMHO it is just a marketing mumbo-jumbo.

What I can tell you is your low voltage is not from lack of a desulfator, but a lack of proper battery maintenance and/or abuse.

One thing that caught my eye right away is it appears you do not have near enough panel wattage to properly maintain the batteries you have now assuming the batteries are used daily in cycle service.

I assume when you say 400 AH it is at 12 volts? With only 220 watts of panel wattage the most current you can push is 17 amps or a C/23 charge rate. Typically solar systems run at C/15 up to C/8 charge rates. You are well below that rate.

I know I am undercharging,and probably why I am losing capacity.I am hoping to offset some of that with a desulfator(IF they work)

[Sunking]

I know I am undercharging,and probably why I am losing capacity.I am hoping to offset some of that with a desulfator(IF they work)

A deslfator is not going to achieve what you are wanting. If all you want is a desulfator go get a PWM charge controller as that is the same basic idea. Will not solve your problem.

They only real chance you have of saving your batteries any more capacity loss, cannot fix the damage already done, is to take two steps:

• Buy an AC powered 4 stage battery charger that can supply at least a C/10 charge rate, and no more than C/8. Put the battery on the charger and run an EQ charge until all the cells read the same specific gravity and voltage. No solar system can perform a proper EQ charge.
  
• Next is up your solar panel wattage to match your maximum demand with the shortest days of the year. If you compliment that with a quality MPPT 4 stage charging, you will maximize your battery life and up the efficiency of your system.

Your diagnoses is correct, the problem is from undercharging your batteries for a prolonged period of time. The big problem is likely lead sulfate crystals have hardened on the battery plates reducing capacity, and the damage is not reversible, but you can slow down the process by acting now. Otherwise your batteries days are numbered.

Well all batteries days are numbered as all will fail. The question is when. With proper care and maintenance you can maximize their useful life up to 5 to 10 years depending on the manufacture and quality of materials used in construction.

Good luck.

SK

[russ]

As Sunking pointed out - 5 to 10 year life cycles for batteries are expected if well taken care of and correctly charged.

The best maintenance and proper charging may get you the full 10 years.

If the batteries are put back back into a corner, undercharged and forgotten then maybe they last a year or two.

Off gridders talk a lot about how to check and maintain batteries - it ain't easy!

Batteries are expensive and a consumable - if one elects to use a battery backed system it is worth spending some time on determining the appropriate panel wattage/battery amp hour combination.