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Knowledge Base : Frequently Asked Questions : Large/RV/Marine Batteries FAQ : When Should I Add Extra Sulfuric Acid to my Battery?

When Should I Add Extra Sulfuric Acid to my Battery?

When you see your battery acid level begin to drop, you may wonder when and if it is appropriate to add acid, or just water.

We recommend that unless a battery was tipped over and all the acid spilled out, that you add only distilled water. Think of it like this: If you were to fill a pot up with salt water, and put it on your stove to boil, what happens? All the water will boil off, and you will be left with only salt. To re-create the original salt water mixture, you simply add straight water, because all the original salt is still in the pan, waiting to be re-suspended in the water. Batteries are the same way. All the chemical needed to make sulfuric acid is still in the battery, it is just the water that is gone. If you add more acid, you will be changing the chemical makeup of the battery which can lead to an incorrect sulfuric content.


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9 people commented, Tech, Always Choosing Wrongly, David, Ninja Kev, and 5 others
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  • Always Choosing Wrongly Please help…my friend put salt and water in my less than 2 year old battery whi h continuously needed a jump start. Battery water seemed to boil and bubble whenmuxture was added along withcharger. Battery responded well i think to charger, although it is not fully charged because we had to remove it due to bad lightning storm. Battery turned super hot to the touch!!!is battery now totally destroyed now? Xar starts and runs but battery is HOT!!! Will battery blow up? Will battery now mess up cars computer? What can i do now????!!!

    Reply  •  May 18, 2016 at 11:00 pm
    • BatteryStuff Tech It is only recommend to put distilled water in a battery once the acid is originally added. The only other exception is adding specially made chemicals such as the Battery Equaliser, which is designed to recover batteries on a chemical level. We have heard of all sort of ways people try to recover batteries, and we some customers tell us their success stories, and other end up with a dead battery. I believe in your case the battery is most likely damaged, as the battery shouldn’t be hot to the touch while charging. If it is hot it is only speeding up the sulfation process, and could eventually comprise the case if left on the charger. I would suggest replacing the battery.

      Reply  •  Ratted article 5  •  May 19, 2016 at 1:27 pm
  • Ninja Kev You answered my question and I’m glad I checked with you first! Thanks alot!

    Reply  •  Ratted article 5  •  November 25, 2014 at 1:22 pm
  • Justin Of course you recommend it, I assume for liability purposes… However, can one empty, ensure all the cells are empty, and refill them with electrolyte’s? FYI, I bought this 5lb dirt bike battery ($65), sealed it… then the bike sat for a year. Today I noticed the batteries cells were completely dry/empty when I reopened it. Just buying a container of Electrolyte’s $8.
    Thank you for your response. Disclaimer; I am responsible for any damage I may bring upon myself ;)
    V/R Justin

    Reply  •  October 5, 2014 at 5:46 pm
    • BatteryStuff Tech Justin it sounds like the battery is an AGM battery that you originally introduced the Acid to, and then sealed. Once sealed it is never recommended to open the battery, but as you have you would notice that it appeared dry, and that is because the fiberglass matting absorbed the electrolyte. It would not be my recommendation to add electrolyte to a sealed battery as all the electrolyte would most likely not be absorbed by the fiberglass matting.

      Reply  •  Ratted article 5  •  November 18, 2014 at 7:23 am
      • David I know it’s 1.5 years later, but this may help someone else…
        As I understand it, when filling an AGM battery (I think all ATV/motorbike batteries are AGM) you have to to add the electrolyte(acid) slowly, or more specifically, keep adding it for a long time as it will slowly absorb and soak down through the glass matting and after a while appear dry. Then you have to add more and wait. Repeat this process until you’re 100% certain that it has completely soaked in and saturated the glass matting. If you just top it up once and close it up, there will not be enough and it’ll shorten the life and reduce the strength of your battery.

        Reply  •  May 18, 2016 at 5:46 am
        • BatteryStuff Tech Their are some suppliers out ther that will ship an AGM battery without an acid pack, which is hard on customers. They don’t always come with instructions as to how much acid to put in the battery. Unfortunately the only way to know how much acid to put into the battery is if the battery comes with instructions, or you have a pre-measured acid pack with the battery. I would contact your supplier if your battery didn’t come with a pre-measured pack just to be sure you add the correct amount.

          Reply  •  Ratted article 5  •  May 19, 2016 at 12:58 pm
  • BatteryStuff Tech It is impossible to do so accurately. We do not recommend adding anything other than distilled water.

    Reply  •  May 16, 2014 at 2:18 pm
  • Vs what to do if some qty. acidic water spilled out? How to regain the quantity of acid that spilled out?

    Reply  •  May 15, 2014 at 5:57 am
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