Coach Battery Charge Level Determination

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whemme
Posts: 2110
Joined: Mon Aug 15, 2005 8:05 pm

Coach Battery Charge Level Determination

Post by whemme »

Some have asked me the best way to accurately determine the level of charge in their coach batteries. Probably the most accurate way (and the messiest) is to use a good old fashioned battery hydrometer. And one that is cheap to buy and is accurate and even temperature compensated is the EZ Red S101 Battery Hydrometer available for less than $10 from many online sites. Below is the website link for this product available from amazon.com.

http://www.amazon.com/E-Z-Red-S101-Batt ... B000JFHMRU

A picture of this hydrometer is shown below.

An easier and less messy (but somewhat less accurate) way of determining battery charge level is to use the voltage vs charge level chart below. However, to use this method accurately requires that you let the batteries set undisturbed for a period of 24 hours without any load on them or any charger hooked up to them. The best way to insure that is to place the coach battery master switch in the off position for 24 hours before taking the voltage readings.

It also requires are relatively accurate digital voltmeter with a stated accuracy of least 0.5%. Note that the chart also shows the hydrometer readings for each level of charge. Note that these voltage readings are for a 12 vdc flooded cell battery. Use 1/2 of these voltage readings for a 6 vdc battery.

Battery Voltage vs. Charge Percentage

Hydrometer Reading on Each CellxxxVoltagexxx Percentage Charge

1.270xxxxxxxxxxxxxxxxxxxxxxxxx12.7 voltsxxxxxxxx100 %
1.250xxxxxxxxxxxxxxxxxxxxxxxxx12.5 voltsxxxxxxxxx75 %
1.190xxxxxxxxxxxxxxxxxxxxxxxxx12.3 voltsxxxxxxxxx50 %
1.150xxxxxxxxxxxxxxxxxxxxxxxxx12.1 voltsxxxxxxxxx25 %
1.120xxxxxxxxxxxxxxxxxxxxxxxxx11.8 voltsxxxxxxxxxx0 %

Some Born Free owners may have installed a sophisticated battery monitoring system and for those that have such a system installed, read your owners manual on how to determine battery charge level.
Attachments
EZ Red S101 Battery Hydrometer
EZ Red S101 Battery Hydrometer
EZ Red S101 Battery Hydrometer.jpg (15.3 KiB) Viewed 6258 times
Bill Hemme - Spencer, Iowa
E-mail: whemme@earthlink.net
2002 Born Free (Ford E-450 V10) 26' RSB
2016 VW Golf GTI - toad

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