Review on E Z Red SP101 Battery Hydrometer by Darin Grosz

The product appears to be well made to withstand everyday use and abuse. If you're just using it to get a rough idea of the state of charge of individual battery cells, it works great. This is probably sufficient for troubleshooting the car battery. However, if you need to know the state of charge of a battery cell with an accuracy of 5%, the scale will most likely not be incremental enough - there are large jumps, especially in the upper part of the range. Hydrovolt might be the best choice. Another problem I had was that it had to be kept straight for accuracy; There is a level mark on the back of the scale, but in use this is often obscured by the float and its large meniscus.