Block batteries have become rarer in our everyday life. However, they are still occasionally needed, especially for remote controls and measuring devices.
Here, as with normal AA batteries, it can also make sense to rely on rechargeable batteries. 9V “block” batteries are rarer, but quite available in stores.
There are mainly two versions here, normal NiMH batteries and lithium-based models. The latter are more expensive, but usually advertise a much higher capacity.
For this comparison, I ordered 7x 9V rechargeable batteries. Let’s see which one is the best!
7x rechargeable 9V block batteries under test
Let’s take a look at our test candidates.
We have 4x NiMH batteries and 3x Lithium batteries in this test. Surprisingly, the lithium batteries are not much more expensive, if at all. You just have to buy larger sets here. For example, the EBL and the BONAI Lithium 9V batteries are offered in sets of four, but then cost less per piece than most NiMH batteries.
But the most expensive battery is ANSMANN battery 9V block type 300mAh with almost 12€ per piece! This is because this has a very large capacity for a NiMH battery with 300 mAh.
Special case lithium
Three of our test candidates rely on lithium battery technology. There are a few points to consider here.
You need a special charger.
The voltage of these batteries is a maximum of 8.4V!
I had assumed that Lithium batteries have voltage converters, similar to Lithium AA batteries. There a voltage converter is used to fix the voltage to 1.5V.
This is not the case here! Instead, we seem to have only two lithium cells connected in series, so a maximum of 4.2V x2 = 8.4V.
Not bad, but it can lead to some devices thinking your battery is almost empty, because they expect 9V and not 7-8V.
Not for smoke detectors!
You should not use any of these batteries in smoke detectors. Why? Smoke detectors will completely drain the batteries and deep discharge them. After that you will not be able to charge the battery.
We come to the most exciting point, the capacity. I discharged all batteries once at 0.100A and once at 0.200A. I think there are few “high power” applications for 9V block batteries, so this somewhat more leisurely discharge rate is appropriate.
All batteries were discharged to 6.5V.
We first see a clear difference between the lithium-based batteries and the classic NiMH cells.
All four NiMH cells manage between 200 mAh and 272 mAh. Excitingly, the ANSMANN 300 mAh battery consistently offers a lower capacity than the ANSMANN 280 mAh battery in practice.
The ANSMANN 9V battery type 280mAh is also the “best” NiMH battery in the field.
However, the lithium batteries offer double to triple the capacity! Although the capacity specification of Realcell is exaggerated and BONAI is a bit too high, but these still come to 500mAh +.
The EBL battery even has a whopping 599 mAh and is thus clearly the largest 9V battery in the test field.
Voltage of 9V batteries
Let’s take a look at the voltage curve of 9V batteries. The difference between lithium and NiMH is quite interesting.
We can see here that the NiMH batteries have a significantly higher voltage than the lithium batteries when full. In return, the lithium batteries last much longer.
However, if you have devices that are “voltage sensitive”, i.e. require the highest possible voltage, then you should avoid lithium batteries.
Conclusion, which is the best 9V battery?
If you want a 9V battery with as high a capacity as possible, then you have to go for a lithium-based model. These easily achieved about twice the capacity of NiMH cells in the test.
The test winner is the EBL 9V 600 mAh battery, which can keep its advertised 600 mAh almost 100%.
However, the lithium batteries have a much lower voltage. These do not offer 9V, but a maximum of 8.4V. For example, my multimeter has not disturbed this. But if you have more sensitive devices, you have to use a NiMH battery.
Here the ANSMANN 9V battery type 280mAh offered the best capacity with a maximum of 272 mAh.
I hope this small test could help you to find the best 9V block battery.