Hi all, I wasn't sure which category to post this in – this question is not MINI-specific (although I do have a 2nd generation MINI). Please let me know if there's a better section to post questions like this:

I pulled out a battery from a 1992 Suzuki Cappuccino (yes the model is called a Cappuccino ). The car sat in a lot for about a year and half and of course I forgot to disconnect the battery so it's completely dead.

It's a lead-acid 12v battery with the 6 compartments. I see the distilled water level is right near the "upper level" marker. I hooked up my battery charger (which I just used on another battery and successfully "reconditioned" it from almost-dead). However with this battery it keeps saying "Connect clamps" error message as if theres no circuit detected at all. The terminal posts were cleaned and are definitely free of corrosion.

I topped off each of the 6 compartments with distilled water and saw the plates just submerged in the water, but still get the same issue. Before I go and buy a new battery, I wanted to know would it be a bad idea to try to "clean" the battery inside, as maybe some parts have corroded too heavily?

for reference this is what the battery looks like: https://www.amazon.co.jp/-/en/40b19r.../dp/B002DF40ZG



Thanks all

 

anyone?

 

Personally, messing with the acid in a battery would be a definite "NO". If the battery is dead due to age, a bad cell, sulfation,etc., it's highly doubtful that you could resurrect it- and an exploding battery is truly dangerous. Maybe take it to Autozone or Advance Auto to have them test it. Take care.

 

@BRGPA thanks for the reply, and under most circumstances I'd agree with you not to touch it. However having some basic chemistry and electrical knowledge I felt comfortable attempting to resurrect the battery and I found some very good information here: https://www.the-diy-life.com/recondi...-acid-battery/ [taking all precautions as noted]

I was able to resurrect the battery, although I have yet reinstalled it to see if it will crank the car, but basically what I did was as follows.

- I tried to recharge the battery as it was using a smart battery charger. However the battery charger just kept saying "please connect clamps"... as in, it did not recognizes a circuit to send current to. The terminals were clean so that didn't seem to be the problem. I had just used this to charge another dead battery, but "dead" on the other battery meant ~ 5V. This Japanese battery pictured here, when I measured it, actually read 0.30 V, completely discharged.

- At this point thought it was worth a shot for a last resort. I got a plastic drain pan (any thick HPDE type plastic is OK) and drained the sulfuric acid/distilled water battery solution from each of the 6 cells into the pan. For this I wore nitrile gloves and eye protection, and did this outside with plenty of ventilation. A glass jar would work as well. Metal was not recommended because unless you are sure of the metal composition, you may strip metal into the solution.

- Separately, prepare a solution of Magnesium Sulfate (pure epsom salt) and distilled water at 60 degrees Celcius and a ratio of 250g epsom to 1 liter of water. At this temperature the epson will fully dissolve quickly. Mix as much as needed, in my case it was about 2 liters needed.

- Use a funnel and fill up all the cells with the epsom solution to somewhere about halfway between min and max fill lines. On this japanese battery, it was easy to tell because it's clear and you could see each of the cells levels. Once it's close you can use a suction/dropper thing to even them out so they are all approximately even. Leave the cell caps "loosely" on so gas from charging can still escape safely. It probably has a vent somewhere anyway, but this is just a precaution

- After this I hooked the battery charger back up, and still showed "please connect clamps" Almost gave up at this point

- Checked between terminals with a multimeter and it showed 0.30 V , resistance was about 5k Ohms. I'm no expert but I think the voltage differential was too low with a resistance too high that this "smart battery charger" didn't recognize a circuit. At this point I thought let's just check it again tomorrow.

- Next day, checked again with multimeter, almost 4V ! Just the epsom solution sitting in the battery built up the voltage differential. Connected the battery charger again, still "please connect clamps"

- Last resort, I grabbed a DC voltage supply with current limiting and hooked that up to the battery (in picture below). I set voltage to 13V, amps limited to 2A. At first the voltage supply read very little current, but slowly over the next hour or two the current gradually increased on the meter until it was almost 2A. At this point I disconnected it and checked the voltage across battery, 12.5V!

- Now, I connected the smart battery charger back and no more "please connect clamps"! It begin a charge cycle and completed charging the battery! I have not yet tested it in the car but all appears to be OK.

According to the reconditioning guide (linked at the beginning), while you can theoretically leave this epsom solution in the battery, for best performance, after fully charging the battery, it's recommended to:
- fully discharge the battery (use a light bulb or resistor to limit the rate of discharge)
- empty the epsom solution
- put back your original sulfuric acid/distilled water solution
- charge the battery back up



TLDR.. If you have a completely discharged battery, many battery chargers might not even recognize the battery, but you can use a simple DC voltage supply set at 1-2 A and get it back to the point where your battery charger will recognize it.




the battery with magnesium sulfate/distilled water solution being charged by the DC voltage supply

DC voltage supply with limiting, set at 13V and 2A

 

Wow, great job! Your knowledge and persistence really paid off. Hope the battery cranks the engine right up. Thanks for sharing your process.