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Experts Panel

Worth knowing about

Battery Watering

Open lead acid batteries consume water, and it is very important that the water used to top up the batteries is good quality battery water. It is also important to top-up to the correct level.


What is good quality battery water?

The conductivity should be less than 30μS (Micro Siemens). Use a conductivity meter to check the water quality.


What happens if I use water with more than 30μS?

The battery loses capacity and the electrolyte will get “contaminated”. For a car battery which you top up once in a while this is not a major issue but for a traction battery that is topped up maybe several times per week it will have a big impact over time.


When should I top up water?

The important thing is to have a routine for when to do it and to make sure that you NEVER fill up just before charging, ALWAYS AFTER CHARGING. Today there are modern single point filling systems allowing you to top up to the correct level by just connecting a quick coupling and then filling up all the cells at the same time. In heavy use and high ambient temperatures you can do this after each charge. If your use is not so heavy you can rely on the indicator of the single point filling system which tells you when it’s time to top up. If you don’t have a filling system you have to open the cell caps and check the water level at regular intervals.


What happens if I don’t top up water?

Your battery will run dry, and in a heavy duty operation with high ambient temperatures like in Thailand this can happen very quickly. When the battery runs dry it will get very hot when charging. As high temperatures is one of the of the worst enemies of batteries this can, and will, seriously damage your battery. Low water levels will also make the battery acid (electrolyte) more concentrated and thereby more aggressive, “eating” on the battery’s lead plates which will shorten the battery’s lifetime.


What happens if I top up too much water?

If you top up too much water, or if you top up just before charging, there is a big risk that battery acid will leak out on top of the battery. Battery acid is aggressive and you don’t want this on top of the battery. If you are unlucky your battery tray has a drainage hole in the bottom which means that the battery acid will leak out into the vehicle and on the floor. Too much water also makes the acid less concentrated which has a negative impact on the capacity of the battery.

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