How to make a load test on your battery bank
With the right instrument it is easy to measure the voltage of the batteries. The voltage tells you how charged your batteries are, but not how big your battery is. To find out, you must perform a load test.
The size of your battery bank is measured in amperage hours (Ah). It is a measure of how many hours you can consume a certain number of amps with your batteries. If you have a 200 Ah battery, you can in theory, consume 20 A for 10 hours. The amount of amps you actually can consume without damaging your batteries depends on the type of batteries you have.
A load test is done to check how many Ahs there are in your battery bank.
If the batteries have a few years on the neck, it may be good to make a load test to find out how much capacity is left in your battery bank.
How to perform the test
To know what voltage corresponds to full and half charge on your batteries, we look at the voltage table to the right. We see that the batteries are fully charged at 12.7 V and 50% discharged at 12.2 V.
The first step will be to ensure that your batteries are fully charged and that the voltage is at least 12.7 V.
So first you charge your batteries, then you start a known consumer and check how long it takes before your batteries are 50% discharged. Be sure to check how many amps your consumers are use (preferably measure with a ampere meter).
Of course you can disharge the battery 100% but that is something we NOT recommend since it is an unnecessary battery wear.
Now we want to know how long it takes for your measuring instrument to show 12.0 V, so start the clock then wait.
Keep in mind that, when during consumption or charging, you need to add 0.2 V to the value you read on your meter, to get the correct voltage. 12.0 V of the instrument thus corresponds to 12.2 V in the batteries if you consume electricity.
When the voltage in the batteries is 12.2V, check the time. Then take the time and multiply it with your consumption.
Time (h) x Consumption (A) = Ah
Now, we know how many ampere hours that your batteries contain, if you only want to charge your batteries to half. Double it if you want to know how much is available until your batteries are fully discharged.
A combined ampere meter and DC power meter, are both good for troubleshooting and to see how much capacity is left in the batteries.
You only hold the pliers around the cable to see how much power it is in the cable.
How much of my battery bank can I use without destroying my batteries?
