12v 3s Lithium Ion Battery Using a 7ah Lead Acid Battery.


Introduction: 12v 3s Lithium Ion Battery Using a 7ah Lead Acid Battery.

Ok so you want a battery that would last a bit longer than your average lead acid battery.. Right... Get yourself the following :

1) an old /dead 7ah lead acid battery
2) couple of small hinges
3) a pull down latch hook
4) some 18650 lithium cells
5) some reasonably thick wire
6) couple of connectors
7) 3s ballance leads
8) and some tools to do the job, including a hacksaw, sodering iron ect...

VERY IMPORTANT PEOPLE! Please note that there are dangers to working with ang lithium cells, please dont bother with this build if you are not prepared to take the risk! The explode, hey burn down your house, they cause you to loose limbs... Bla bla bla... Go google the risks, and weigh them...


Ok Gary, with that out of they way, lets move on!

Step 1: Before Opening the Battery

Make sure the battery is dead! If not.. Discharge it completely... Please Gary!

Take the battery, and locate the small gouge on the top where you can lift the top part using a very small flat screw driver... See the red circles... This will expose the little rubber caps.. Remove the caps and drain any acid, and flush it as much as you can with water...

Step 2: Cutting the Battery Open

Battery must be discharged completely!

Cut the battery in a straight line right on the line where the top and bottom part had been glued together... Cut through the battery all the way...

This will leave you with 2 halves.

You can clearly see the one I opened was a fake.. It was full of glass!

Step 3: Level the Two Halves

I have not taken any pics of this step, but after cutting open, wash bothe sides after all the insides had been removed... Then put a piece of sand paper on a very level top, and sand the areas where you had cut untill the two halves fit on top of each other nicely without any gaps.

Step 4: Add Cells

Then add 3 cells to each compartment, ensuring that you solder all 3 cells top and bottom in parallel.. Those cells will then be connected in serries with the cells next to it untill you have a 3 cell battery in serries, that consist of 6cells each... See pics

Step 5: Add Ballance Leads and Close Up

Use the hinges and latch to close up after the ballance leads had been added.

You save more than half the weight and gain a whole lot of amp hours!

Hope you enjoyed this instructable.... :)



    • Oil Contest

      Oil Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Clocks Contest

      Clocks Contest

    16 Discussions

    necesitas un circuito de proteccio

    I see, each paralleled set is made up of six cells. There are three sets of paralleled cells. The three sets are then wired in series. The balance leads go to an external lithium cell balance regulator, wired for the three sets. It would be nice to install an internal balance pcb. I wonder if we could find, or fabricate our own lithium cells to take maximum advantage of the area in each of the cell compartments?

    The gel cell is not a fake. They just don't need all the room inside to make up their rated capacity. I would assume the glass is to add weight for stability. The goop you took out is lead and sulfuric acid jelled and should be disposed of properly. Just because it doesn't look like a traditional battery doesn't mean it isn't one and disassembling one that still has life in it can cause personal injury or a fire. Take it seriously

    8 replies

    Gary its a fake! It was like $3 and lasted like 3 months... Its died.. It had no gel in it.. It was 6 small lead acid plates wigh little bit of white cloth like stuff against it... Lol

    Just a warning lest someone else break into a real one with just 1 cell dead. Lead acids go bad one cell at a time often.

    Point is, just because the one you took apart was a dud doesn't mean all lead acid Gel-cells are. I have worked with these and they can be real current producers. If you take one apart that has real live cells in it the second you start moving around the electrodes and manage to short a cell you are going to have sparks at least and a fire or explosion at most. If you aren't wearing a rubber apron, gloves and safety goggles you are risking damage to your eyes, body and a fire you can't put out without lots of water. The explosion will be from hydrogen and oxygen and the fire from heat, lots of it, when the electrodes weld themselves together and start producing copious amounts of hydrogen. You can also be burned from the acid and the fire. Most of these don't have the glass and you won't get them apart without scooping action and when you start that you will produce electrode shorts.

    Secondly as someone else pointed out the charging on the lithium ones is not optimal to say the least. Lithiums do start hot vigorous fires and once the lithium is exposed it starts to burn. It is highly unlikely you have anything that will fight a lithium fire. Water makes it worse, dry chemical fire extinguishers are useless. Charging circuits need current control, voltage control, and charging curve control. Without that you will either have a dead battery soon or an exploding battery, or a fire and the fire can happen even when the battery is just sitting on the shelf. When these batteries burn they explode the lithium once it gets exposed to moisture, even from the air starts to produce hydrogen. The hydrogen bursts into flame instantly and produces a very hot fire then the nearby cells follow the same pattern. These batteries have just been banned from air transportation because they can short with no provocation and once that happens they do not calm down they go from hot to an inferno, then they heat nearby batteries and cause them to do the same. Lithiums are shipped in a 35% or so halon atmosphere and with halon flooding in case of a fire. That is the preferred method of fighting a lithium fire and the FAA has just discovered that halon is ineffective. Parallel charging lithiums is unwise for the reasons stated above. Now before you say it notebooks have lithiums and do OK but they have complex charging circuits that monitor the batteries and fusable links in the battery pack that open up when they sense to much heat during charging or use. In spite of that they still cause the occasional house fire.

    I know creativity and reuse is a real purpose of this group and if you are going to do this do it educated:



    I have some lithiums sitting around that I would like to do something like what you want to do but, I haven't bothered to make a charging circuit so I haven't done it. Secondary batteries are not like flashlight batteries that you can charge. They are really dangerous if not respected. By the way I am an electronics engineer I earned the degree.

    Learn something and stay safe.

    Gary! Stop whining! If you dont like the damm build then report it and carry on with your life mate, no need to be such a drama queen about it.. Hell mate.. Its a fake! PERIOD! Google the damm brand name and the battery if you want! Its a fake! Where in your life will you get a damm 7ah gel battery for $3?? Please! Its NOT a gel battery... I know, coz the gel batgeries cost like $30 locally... And besides.. I know where I bought it from... And about the lithiums being so dangerous.... If you dont want to take the tisk, MOVE ON WIGH YOUR LIFE :) but thanks for the input... Good day to you sir ;)

    Hey , where can I buy these AGM batteries for $3 ? I might want them !!

    Cheers , take care , and have a good day ! 73 mate !

    I think what you had there was an AGM TYPE battery .


    Well ....if it lasted 3 months before it died , it could have been a charger problem . Lead-acid batteries can be a little tricky , depending on how they are used , ie , depth of discharge , charging current , how long they sit in a discharged state , etc .

    Cheers , take care , and have a good day !!

    You don't explain the purpose or how to connect the " ballance " or " ballace " lead ( you spelled it both ways ) It looks like a Molex connector that you would use to power an older computer disk drive .

    The old guts of the battery appear to be an AGM type ( absorbent glass mat ) see my other post below .

    The glass plates were most likely used as good stiff spacers to ensure the plate spacing and prevent plate warpage .

    You need to know what you are working on when you take something apart . It kind of reminds me ( a little humor here ) of a 3 stooges episode where they were supposed to be plumbers . Curly Joe took a conduit apart , and said " Here's why you can't get any water , your pipes are all full of wires !! "

    Cheers , take care , and have a good day !! and 73