http://www.powerstream.com/1922/battery_1922_WITTE/battery_WITTE.htmhttp://danielwebb.us/projects/pd_tech_books/http://chestofbooks.com/crafts/scientific-american/sup5/The-Montaud-Accumulator-Continued.htmlhttp://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Accumulator
The above links are some of the references I used when building my first lead acid cell about two years ago. There is a wealth of information on the internet on how to build lead acid batteries but it does take some digging to find. "Plante Accumulator" will find some of the older documents that give more detail in the construction and plate formation techniques. Going through the old patents (most are available on-line) is also an excellent source.
The last link provides provides good detail especially on how to do the plate formation which is required if you want to improve the capacity of the plante plate (solid lead plate).
I highly recommend that you build a very small test cell so you can get the hang of doing cell construction and plate formation which is critical to the performance of the cell. My first cell had 3 plates (2 negative and 1 positive plate) constructed of lead sheathing cut to 1"x2". For separator material I used paper towel (no name brand) wrapped around the positive plate. I thought the sulfuric acid would destroy the paper towel after a few minutes but it lasted about 7 months.
Here are some notes extracted from my tinkering logs on building lead acid batteries using Plante type plates. Most of these notes are about one of my 6V batteries that I use in my small RE system based on the Plante Accumulator.
The 6v battery is made from 3 cells. In each cell I used 11 negative and 10 positive plates. For plate material I used lead sheathing reclaimed from the local scrap yard. 100lbs cost me $35. Each plate was cut to measure 5"x6"x0.070" with a 1"x1.5" tab on the top off to the side. Plates were scored vertically on both sides using a metal comb scoring tool with teeth 0.025" apart. I cast the lead bus bars with terminal post. The lead plates were soldered to the bus bar with 0.30" spacing. The negative bus bar has 11 plates attached and the positive bus bar has ten plates attached.
For separators I used thick plastic vegetable bags with micro pores. I made positive plate pouches (which forms the separator) out of the bags by cutting the bags a little bigger than the plate (0.25" around edges) and heat sealed (using wife's iron) the two sides and bottom. Using sintered pvc material would be better but the scrap yard didn't have any old lead acid batteries laying around at the time I built the first battery .
I placed the pouches on the positive plates first before sliding the positive and negative assemblies together. Trying to put the pouches/separator on the positive plates after the assemblies were together did not work too well.
The plates must hang from the bus bars. In my first cell I had the plates support their weight but after about 2 months during plate formation the plates were buckling. Discharging at too high a current also didn't help.
For cell containers I originally used HDPE 2 plastic square containers 10"x7"x5" for each cell. I used plastic inserts to support the bus bars so that the plate bottoms were suspended about 1" from the bottom. The top of the cell was made from HDPE 2 plastic about 0.375" thick and is split in half so I can lift one half to inspect the cell. I used roofing tar to seal the two halves to the case. The battery posts are sealed using the roofing tar. I used tar because I wanted to be able to remove the tops and inspect the cells every few days. Proper venting is a must so I picked up 3 vent caps from the local battery shop.
You must make sure that the posts and bus bars are well anchored so that the plates don't move. Ok, with my current setup I have not achieved that so I must be very careful when connecting/disconnecting the battery or when removing the tops.
The electrolyte (sulfuric acid @1.26 sg) was purchased through NAPA auto supply at $20 for 5 gal. Yeah, I have lots left over for more batteries.
Have a read of the last link on plate formation. Plate formation does take a while. For my first battery it took almost 3 months before I got up to about 80 AH (@20hr rate) capacity. That doesn't mean you can't use the battery during that time. After doing plate formation for the first 5 days I was up to about 20AH and put the battery into service. I kept a log of the charging, discharging to determine when to do polarity reversal and rest periods.
Some things I learned while doing plate formation:
- For the first charge I had to make sure I started with the negative post as the negative ie the post with the odd number of plates which is the polarity you will use when you finish plate formation. I found that the plates that operate at the polarity that they were first charged with will have a slightly higher capacity than their opposite polarity.
- Keep charge current very low during initial formation. Initially I kept charge current < 300 mA for the first 5 cycles.
- I used an absorption phase termination voltage of 2.40v/cell @ 20 celcius. Once the battery charge voltage reached 2.40v/cell then current was decreased to maintain charge voltage at 2.40v for one hour before commencing a discharge cycle or rest period.
- As the battery capacity increases it takes longer between each polarity reversal cycle and rest period. Don't get greedy on trying to get maximum capacity quickly because you will end up with a shorter life cycle or a box of mush (only happened once).
- Doing heavy discharges or bulk charging right after a polarity reversal during the plate formation stage is bad. After reversing the charge leads only use about half the current as was used in the previous cycle. If you don't decrease the charge current after polarity reversal you will lose more plate material especially from the plates that were positive in the last cycle. After the first recharge after a polarity reversal I would go back to using normal charge current during the bulk phase. For the size of plates I was using I only used a charge/discharge current of 1.5 Amps after I had reached about 20AH capacity. For the first recharge after polarity reversal I used 0.5 amp charge current until the cell voltage was 2.4V.
- I found discharging to 1.60V/cell as stated in the 1911 documentation increased the time taken to increase cell capacity. It seams to be ok for about the first 5 plate formation cycles. I did this on the first cell and thought things were good. For cells 2 and 3 I used a micro controller to automate the process and mistakenly had the low discharge cut out voltage set for 1.75v and those two cells reached the same capacity as cell 1 in about 2/3 the time. I did individual cell plate formation to learn how changing parameters affected plate formation but its the slow way if dealing with multiple cells. I did the second battery as a whole unit.
- For each charge/discharge cycle you loose a little bit of the plate material that was was being formed. Structural strength decreases in the positive plate as it turns into the very soft PbO2 and eventually turns to mush. Its a bit of a balancing act to know when to stop the plate formation stage and achieve good capacity along with good cycle life. You will find that the negative plates will easily out live the positive plates no matter what you do.
- If you are using pure lead then be careful about the maximum discharge/charge rate. Pure lead is very soft and buckles easily when subjected to high currents. Buckling is related to the thickness to plate area ratio. Thin plates buckle more easily than a thicker plate with the same area. The plate size I use handled 5A discharge no problem. The plates showed some curvature with a load of 15A over 1 hour. I limit the batteries to a max draw of 5 amps.
Total weight of my first 3 cell battery was about 60lbs. After 9 months I did a couple of capacity tests. The first test was at 5 Amps which went for 21 hrs with the battery voltage starting at 6.36v at 24 celcius and finishing at 5.90v at 15 celcius. Second test 2 days later was 1 Amp for 126 hours, starting voltage 6.47v and stopping at 5.90v with temperature varying between a high of 27 Celsius in the day and a low of 14 Celsius at night. No where near as good as a T-105 220AH golf cart battery which weighs about the same.
It has now been about 17 months that I have been using the batteries and they are still working well. I only use about 12AH a night for 2 CFL's in the house that run off a small 60 Watt inverter so the batteries should last for several more years. The batteries are charged by noon the next day from solar and wind.
About 8 months ago I did a battery rebuild. Building from scratch was a good learning experience but finding a good case, and separators was a problem. I found a discarded 6V tractor battery in the ravine down the road and was going to take it to the battery recycling center and on the way changed my mind when I realized that the case was in excellent condition. To make a long story short I replaced the spent positive plates with Plante type plates and re-used the negative pasted plates since they were in fair condition. I didn't do plate formation since the negative pasted plates were already formed.
It took about 40 days before the battery capacity was up to 30AH, each day being a charge/discharge cycle of about 3AH at a rate of 0.3 Amps. Its been in service for about 7 months now. The electrolyte was re-used and water was added to bring the level up since the cells were only about half full. After about 14 days of charging/discharging plus using an Alistair Couper pulser, the specific gravity went from 1.05 up to 1.20. I then added a little bit of Sulfuric acid to bring each cell up to 1.25. Specific gravity in each cell has now settled out at about 1.26 @ 20 Celsius once charge voltage has been at 14.4v for a few hours and charge current < 0.5A. I haven't done another capacity test yet.
I was not able to reclaim the positive plate mush. The mush was put in a plastic container and taken to the recyclers. I did have to pay for them to take the stuff but better than having it in the landfill.
I didn't save any money by building/rebuilding my own batteries when you factor in build time, plate formation time, material costs, and mistakes. I didn't build a better battery than what is on the market. But it has been a good learning experience and I have a better idea as to what I want in a battery if I ever buy one. I haven't had any cells fail yet, all are working well, but when something does go wrong, doing repairs shouldn't be a problem.