Dead Battery Charging

spdas

Aloha, I have been using 24-36-48V  600-1100AH forklift batteries in my off-grid manufacturing facility in Hawaii for 10 years.   Now I am trying to more fully understand charging methods of lead acid batteries, especially "dead" ones.   Here is my example and conclusions....please be free to comment and advise:

1) I recently got a 36v 1080ah large electric sitdown forklift with battery and trying to bring it back to life.   It was at 4.5V. and the cosmetic condition was really good and had almost no Positive Cell growth.
2) I am using an outback FMX 80 charge controller on a bank of 12x280watt panels and....
3) charging for 6 days now @ 5-8 KWH per day.  Battery is coming up and at the sunniest time it is 65A @ 41V.   (I am setting the controller at 48V equalize charge.
4) 3 cells were still a bit low.   Most now are about 2.10- 2-15, but the 3 are still about 1.90v but coming up .5v per day
5) I plan to watch the temp of the battery and only allow the case to be a bit "warm to the touch"
6) I have noticed that the first few days the case was warm on the top 1/4 of the case and now after more days the case is warm down past 2/3 and even slightly warm at the bottom.  
7) I have used the forklift and "cycled" the battery and every day the duration of charge gets longer.

so I assume that I am progressively "knocking the sulphated material" off the plates and the lessening heat and more uniform heat of the battery is the resistance lessening and I am actually adding capacity, rather than giving the battery a "Top Charge."   (the first day of use the battery lasted 3 minutes driving and now it is 30 minutes or so).  

Comments/Advice?

Francis
   
   

Photowhit

You should talk about the specific gravity of the cells!

Voltage information, particularly when charging, is pretty useless in terms of capacity! I have no idea what the heck "...Battery is coming up and at the sunniest time it is 65A @ 41V..." are you saying it's has is accepting 65 amps? 41 volts would be low for charging voltage. I would want higher. Equalizing would be 46 volts and above, but no need to go to higher voltages until it is accepting 2-3% of capacity.

I'm guessing you are charging from a solar array?

spdas

Photowhit said:

You should talk about the specific gravity of the cells!

        Yes,  I am doing that now and am seeing that Voltage alone is pretty useless.

Voltage information, particularly when charging, is pretty useless in terms of capacity! I have no idea what the heck "...Battery is coming up and at the sunniest time it is 65A @ 41V..." are you saying it's has is accepting 65 amps? 41 volts would be low for charging voltage. I would want higher. Equalizing would be 46 volts and above, but no need to go to higher voltages until it is accepting 2-3% of capacity.

     Yes from my Solar Array and since it is winter, the max I am getting is 65A @ 41v which is 2665 watt coming from my 3360w panels.  .   I have it set at 48v but not going over 41v yet.  ,  Voltage has been climbing up daily from 35V the first day..     
What do you mean by   "until it is accepting 2-3% of capacity."

thanks

Photowhit

That is generally how you determine if a battery is fully charged, once fully charged you can start equalizing, trying to bring up the weak cells. 

Do you have a hydrometer and can you tell us the Specific Gravity (SG) of the cells?

spdas

will get the SG tomorrow.   But is it better to try charge setting at 39V and after a few days go to 48v to EQ?   Or just use 48V from the start (since I started at 4.25V)?
thanks. 

westbranch

well your method is certainly not orthodox but appears to be working... if you have done the same to other batteries and brought them to life again... Is this the case or am I not reading your post?

My  thoughts about the top of the battery cells starting to get hot at the top and then it moves down is that the electrolyte is boiling at the top as it is EQ-ing the top of the plate s and as the heat moves down, means that the EQ is  removing sulphites on a different part of the plates..

I also agree with Photowhit that the standard is to measure the SG and the voltage of each cell to see just what is chemically happening in each cell...  however the fact that the cell voltages are rising is also a good sign.

Tell us more about your experiences with battery recovery... how did you come up with the idea to EQ a 36V battery at the setting for a 48Volt battery?

mcgivor

Are you cycling the battery? Your OP said #7 you are using the forklift every day, it would probably be better to try getting the voltage up to full charge, then do an EQ, rather than dragging it down and having to start over every day.

spdas

Aloha, all.
   
1) What is a more common method to bring back a dead battery?   I am just following advice from you-tube and other searches.
2) i am not using the forklift, only draining off the surface charge.
3) I understand to equalize a 12v battery you would use 16v, so 3x16=48v for the 36v battery
4) one other thing I do for my 24v offgrid system is to get used 36v batteries and tap off at 24v and when one cell eventually dies off, I still have 6 more cells as a spare.
5) yes it seems to me that the warmth spreading through the battery is that the sulphate is getting broken up and the capacity is improving, but I will do the SG later this morning to confirm.
6) I have been getting batteries over the years mostly free as companies don't want to deal with them, but now there is more awareness of $ for recycling, so it is a bit harder.
7) FYI we run welders and all sorts of electrical equipment here at our shop and have 10 outback charge controllers and 5 inverters, with 12 forklift batteries.  Since panels are so cheap, I am putting up 2 new systems....... one for only charging forklifts (12 panels and one fm80 outback)   and a big 8000watt Radian inverter (sp?) Outback all-in-one system with 24 panels.   (panels on sale here for $.39 a watt)

francis

Photowhit

You don't 'equalize' until the battery is fully charged. In running at a high voltage, you are heating things up and likely hardening the sulfates to the plate. That is the theory anyway. Are you using a temperature sensor?

spdas

I guess I am alright as I am not really "Equalizing" yet as the voltage is running at 39v up to 41v or so at "high noon".
  
Doesn't a normal battery charger lead the voltage by more than 40v  to achieve 38v?  (ie  12.65x3 = 38v full charge?).   Does  a normal battery charger start at say 44v and backs off to 38v at full charge or does it stay at 44v and backs off the amperage to "0" when fully charged? 

Estragon

spdas said:

I guess I am alright as I am not really "Equalizing" yet as the voltage is running at 39v up to 41v or so at "high noon".
  
Doesn't a normal battery charger lead the voltage by more than 40v  to achieve 38v?  (ie  12.65x3 = 38v full charge?).   Does  a normal battery charger start at say 44v and backs off to 38v at full charge or does it stay at 44v and backs off the amperage to "0" when fully charged? 

Generally an off-grid charger will put whatever current it can into a bank until it reaches a setpoint, say 44v.  It will then hold that voltage and current will drop off as the battery gets full.  It will fall back to a float voltage (eg) 38v after a set period of time, say 3-4 hours, or in the case of some chargers, when the current drops to a set level, say C/100. The battery manufacturer should have specifications available for these settings.

Incidentally, are you checking electrolyte levels through this process?

spdas

Yes electrolyte levels are coming up slowly.  From totally dead up to ~1225.   Battery is warm all over now during the daily charging so I may have to limit the amperage if it gets too warm.  Charger is putting out about 13kwh per day.

Estragon

Sorry, by levels I was referring to the physical level as well as SG. As the batteries get full they may gas some and need water. Some cells may do more than others as each gets full at different rates. Presumably you'll notice when you check SGs though and add water as needed to keep plates covered.

mcgivor

Some information gathered, see page 24, this is something I will begin to attempt tomorrow, water treatment.

softdown

Welcome back to the forum! Seems that it has been a few years.

I have read a number of your old posts. You have brought back some really old forklift batteries. Batteries that most would consider beyond the point of being repairable. I wonder if that is possible because Hawaii rarely gets much over 77 degrees?

It seems that heat may be a large factor in the "lethality" of sulfation. I say that because we have a few stories of batteries surviving cold winters at an approx. voltage of 10. Yet there are many, many stories of batteries suffering sulfation ruination from several days below 11 volts. In fact, there are numerous claims that sulfation starts when battery voltage drops below 12.5.

Then spdas shows up with repeated stories of bringing back really old batteries that have been really dead for many years....as memory serves me.

I am also a forklift battery enthusiast. My main lament is the water usage. I consider the ~$5/each "water economiser" caps as a "must have" item. Their weight can also be a safety concern especially in the 24 volt configuration. Easy to tip over when moving. You have a warehouse which makes them much easier to handle. I have a lot of sand, snow, and ice.

Estragon

@mcgivor - re:water treatment. Would be interested to hear how it goes. Maybe start a new thread? Thanks

mcgivor

Estragon said:

@mcgivor - re:water treatment. Would be interested to hear how it goes. Maybe start a new thread? Thanks

I have a thread already, Water treatment for over sulfation, have begun the process and will update there rather than derail this thread. 

spdas

I would like to know the difference using my outback controller vs a "real charger"?  The outback will not set to an EQ voltage of 48v as it is not a constant voltage machine, and only will lead the voltage that the battery allows.   Then will adjust amperage and voltage up to the limits I set the Controller.  So there seems to be no way to initiate a "real EQ".  (slamming 48v into the battery).   Thots?
Francis      BTW  the forklift (1080 amp) battery seems to be coming up nicely and every day I end up at 38 or so volts.and each day with that ending voltage the SG gets higher, suggesting that there is less and less of a daily "surface charge".    

mike95490

spdas said:

I would like to know the difference using my outback controller vs a "real charger"?  The outback will not set to an EQ voltage of 48v as it is not a constant voltage machine, and only will lead the voltage that the battery allows. ......

Can you give us the model #  of your controller ?    Most modern controllers CAN perform a battery EQ, if they have enough solar panels to provide the needed power.

spdas

Aloha, it is a Outback Flexmax 80 FM80 MPPT 80 AMP Solar Charge Controller.   and I am quite familiar with the eq settings.  My question is more along the lines of whether an "ordinary charger"  will eq at the required voltage right from the start?  Such as will it eq at 48 volts or like the Outback, does it still depend on the battery to regulate the voltage, and in my case the voltage is around 40v now and is slowly climbing  up to the EQ voltage (that i set for x number of hours) but it may take several hours.   Then what is the difference in me just setting the charge to 48v?
 

Photowhit

spdas said:

Aloha, it is a Outback Flexmax 80 FM80 MPPT 80 AMP Solar Charge Controller.   and I am quite familiar with the eq settings.  My question is more along the lines of whether an "ordinary charger"  will eq at the required voltage right from the start?  Such as will it eq at 48 volts or like the Outback, does it still depend on the battery to regulate the voltage, and in my case the voltage is around 40v now and is slowly climbing  up to the EQ voltage (that i set for x number of hours) but it may take several hours.   Then what is the difference in me just setting the charge to 48v?
 

Charging the battery doesn't depend on the voltage being any higher than needed to have an exchange going to the battery.

Equalizing only happens when the battery is fully charged. I think I said this before...

mike95490

You have to fully charge the battery before you can EQ.   Most common 48V chargers require 240VAC and 3 phase power, so that's not going to generally happen.  The common method is to use your genset and inverter/charger in the AM, and let the solar take over for the rest of the day,  It may take a couple days to get the battery up to FULL before you can initiate the EQ.