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Topdon BT100 battery tester in use, testing an AGM battery |
Quick specs
Make: Topdon
Model: BT100, 100 - 2000 CCA
Type: Electronic diagnostic tool
Pros: Very good value for money, easy to use. Useful crank and alternator testing.
Cons: Maybe the pincers could be a bit better.
What is a battery tester and why do you need one?
Battery testers work by applying a load and monitoring the voltage and current (in amps) of the battery. With this BT100, a few simple details are filled in, type of battery, lead acid, AGM etc. One thing to note, is this model makes no mention of testing lithium batteries. It is suitable for 6V (less than 6V and the tool will not switch on when connected to the battery) and 12V batteries only.
With the prices now so affordable and the features offered, it makes sense that you have one in your toolbox, but how do you know if you are getting a good one, read on to find out.
Battery specs
Next piece of information is about battery "size" or capacity. Size is not exactly a specific word for this, simply you must tell the machine exactly what it is going to test so it knows the baseline to test the battery against and decide whether it needs replacing or not.
To get the information on battery capacity there are usually specs printed on a label conforming to one of the accepted standards, EN and CCA (Cold Cranking Amps) for example are very well known standards or specifications for classing a battery. There is a very useful table available to download (link opens in a new window), that gives you some useful conversions for other battery types to use them with the tester. Don´t get to worried about all of this, most batteries will have some sort of rating on them, if you can find the make of the battery, more detailed information can be found online if necessary.
Before testing a battery
Make sure the battery is properly charged, not just measuring voltage but actually charged properly using a smart or multi stage battery charger. You cannot accurately be sure of a battery's condition if it has not been charged fully for testing, the tester often asks for the battery to be charged before retesting. If there is obvious battery damage, that awful smell of bad eggs from overcharging a battery or spilt acid or damaged battery case, do not put the battery on charge, it should be replaced directly.
Please make sure the charger used is correct for the kind of battery type, so an AGM profile for AGM batteries or a lead acid charge profile for lead acid etc. Batteries are ruined or fail prematurely just because the wrong charger or wrong charge profile is used.
After the battery has been fully charged, remove or disconnect the charger and let the battery sit for a while, do not be tempted to test it straight away. The reason for this is something called surface charge and can give false test and lead you to believe the battery is in good condition. Leave the battery to stand overnight, if time is of the essence connect a load to the battery for a short time, a light bulb works well.
If you are testing a car battery or any other single battery there is no need to disconnect the battery terminals providing the battery is isolated from other batteries, if you are testing a large hose bank of batteries that might be connected in parallel or series, you have to disconnect the batteries and test the, individually, maybe even charge them individually. Some smart chargers have the ability to recondition certain battery types.
Using the tester
The unit is pretty foolproof, I usually connect the red pincer first to the positive terminal and the black pincer to the negative terminal. The screen lights up and tells you the voltage of the battery.
Select battery test, press enter, then the type of battery, incidentally this device allows you to test spiral wound AGM batteries, to the best of my knowledge right now there are only a few of these types on the market, the most well know being the Optima brand and Exide also make them.
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| EN ratings on a battery. Top: 50Ah AGM battery with an 800 A (EN) rating, Bottom: 140Ah with a 900A (EN) rating. |
The next stage is to select the rating of the battery (CCA, EN etc.) Press enter to start the test, the machine will perform the test and give you the results in a matter of seconds.
Test results
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| Bad news for these batteries, all 3 failed the test, indicated on screen by "bad cell, replace" |
Interpreting the results
There are four lines of text, with the result in capitals that scrolls along the bottom of the screen, there are also three lights underneath the LCD screen. In all instances of these three batteries, the results were as expected, they needed replacing, these are AGM batteries forming a house bank, connected in parallel. All of these batteries were fully charged using a multi stage charger with an AGM charge profile, then left to stand about half a day.
Healthy: how much as a percentage and voltage reading of the battery capacity is actually left, these batteries only had 1% of their original available capacity. Any loss of capacity is not good, it´s normal as the batteries age and is to be expected, but 99% loss is something you don't see very often.
Charge: as a percentage, how much charged the battery is, testing a battery straight away after charging can give false results, indicating the battery is in better condition than it is, that's why we leave them or connect a load to remove any surface charge, the last thing you would want is to put a battery on its way out back into service.
As a reference, a fully charged battery, we would want to see somewhere near 13 volts.
Internal R: This is internal resistance, measured in Ohms. The lower the resistance, the better the battery is able to carry current. We would like to see a figure of 0.02 to maybe 0.05 Ohms, as near to being zero as possible, as we can see here, these batteries are giving readings in the milliohm range. Internal resistance is used as another parameter to indicate overall health of the battery.
Rated: This is the parameter we entered into the tester to be used as a reference, along with the type of battery we´re testing.
Scrolling text: A summary of the test, in the photos above a bad battery cell was detected and the machine advised to replace. Other examples of the text include, replace, recharge and retest and good battery. There are 3 LEDs below the screen that also indicate the results of the test.
Conclusion
At the price battery testers can be bought for, you almost cannot be without one. This model is still available, there are other models from the same brand with Bluetooth and a larger version capable of testing larger batteries and also 24 volts. The pincers I think could be a little stronger, this is a minor gripe and the tester in the photos has been used extensively in a workshop.
I would not hesitate to recommend this model, I would also recommend getting a plastic box or protective bag to keep it in. I think one of the most useful reasons to have a battery tester is you do not need to remove the batteries from the boat to test them, or take them anywhere.
For professional use there are more expensive testers available that have printers built in, this is very handy if you have to test lots of batteries. Another useful feature for a professional is if a client asks you to test the batteries, it can be done with them there, no doubts as to the results. The tester serves as a useful diagnostic tool, test before replacement, this particular model represents outstanding value for money and you could ask not more of it for the price.
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