External Battery Roundup: Stay Away From The Wall Socket

Feature Checklist

Feature Checklist Dual Charging Separate Charger Charges Dell Charges Mac with MikeGyver MagSafe
Amstron MedXP 140YYNY
Amstron MedXP 300YYNY
Brunton ImpelNYYY
Brunton SustainNYYY
Digipower Universal Notebook BatteryN/AYN/AN/A
Electrovaya PowerPad 130YYYY
Electrovaya PowerPad 95YYYY
Energizer XP18000YYNY
Energizer XP8000YYNY
Lenmar PPU916NNNY
PowerTraveller MiniGorillaNYNY
PowerTraveller PowerGorillaNOptionalNY
Tekkeon MP3450YYNY
Tekkeon MP3450iYNNY
Tekkeon MP3750YYNY
Feature ChecklistAccepts MikeGyver ChargerUse Dissimilar Input/Output Tip CombinationOff stateLinear Battery Gauge
Amstron MedXP 140NN/ANY
Amstron MedXP 300NN/AYN
Brunton ImpelNN/AYY
Brunton SustainNN/AYY
Digipower Universal Notebook BatteryN/AN/AN/AN/A
Electrovaya PowerPad 130YNYY
Electrovaya PowerPad 95YNYY
Energizer XP18000N/AN/ANY
Energizer XP8000N/AN/ANY
Lenmar PPU916YN/ANY
PowerTraveller MiniGorillaN/ANYN
PowerTraveller PowerGorillaNN/AYN
Tekkeon MP3450N/AN/AYN
Tekkeon MP3450iNNYN
Tekkeon MP3750N/AN/AYN

Dual Charging: If your external battery and notebook are both short of a full charge, you need to charge both batteries. If they are connected, the external battery always takes priority. Some batteries will charge both systems at the same time by demanding a higher current from the wall socket. Notice that only a handful of the batteries in this roundup are capable of this.

In the case of Brunton and PowerTraveller, you need to physically disconnect the AC charging cable before using the external battery to power the notebook. The battery refuses to output power otherwise. In the case of Lenmar, you don’t need to disconnect, but everything is done on a priority-based system. Say your notebook is at 50% and the PPU916 is at 90%. First, the PPU916 finishes charging, then it stops charging and charges your notebook. After the PPU916 goes to 0% or your notebook hits 100% (whichever occurs first), it repeats the process. Obviously, Lenmar's implementation is very inefficient. It doesn't properly shunt power.

Separate Charger: Not all of these batteries allow you to make dual use of your notebook’s charger. Some require you to use the one included in the box. Only the PowerGorilla provides an option to choose. Remember that this benefit is a double-edged sword. With a separate charger, you are guaranteed a way to charge your battery. An input tip system has no guarantee unless the company explicitly states that your notebook is compatible.

Charges Dell Notebooks: The majority of Dell notebooks (excluding the Minis) have a power circuit that requires a proprietary identification signal before charging initiates. If this signal is absent, you can only power the notebook. That is why third-party chargers often do not work with Dell notebooks. Some vendors have figured out Dell’s charging scheme and others haven’t. The only batteries in our roundup that can actually charge a Dell notebook are from Electrovaya and Brunton. Every other battery could not charge our Vostro 3300.

Charges Mac with MikeGyver MagSafe: All of these batteries will output to the old 16 V ThinkPad tip. Every battery in our roundup will power and charge a Mac notebook provided you have a modified MagSafe cable.

Accepts MikeGyver’s Charger: MikeGyver’s modified MagSafe charger uses the old 16 V IBM ThinkPad tip. This setup only works with the Electrovaya’s PowerPads and Lenmar’s PPU916. Why? Well, technically Apple’s power brick sends out three voltages. The default is 12 V, which is enough to keeps your Mac powered. That is why the MagSafe’s LED turns green when you first plug it in. When the notebook needs to charge, it demands 16 V (or 19 V if you have a 15.6” or 17.3” MacBook). This demand initiates a voltage switch in the adapter. Electrovaya’s tip system is based on sense resistors, so it demands 16 V from the beginning. The PowerGorilla and MP3750 also use sense resistors, but because the resistor is set up on the input side within the battery, both only detect the default voltage (12 V). This is insufficient to charge either battery. Lenmar doesn’t use sense resistors, but it does have a manual switch that forces the battery into a 16 or 19 V mode. This allows the PPU916 to demand a voltage higher than 12 V from the power brick. The solution is to move to a third-party power brick like Targus' Premium Laptop Charger (APM69US).

Use Dissimilar Input/Output Tip Combination: This is a safety issue. In order to prevent overload (or underload), the entire circuit must maintain the same voltage. This only applies to Electrovaya’s PowerPads, because they allow you to use a notebook’s charger for dual charging. Simply put, you cannot use a 16 V IBM adapter to charge and power a 19 V Dell notebook. If you force this, the PowerPad will refuse to output power until you disconnect the input power source.

Off State: Using a multimeter, I found that only some of these batteries have what would be considered an off state. Even if it has an on/off power state, there is no guarantee that the battery is completely powered down. The lowest state for some of these batteries is similar to the ACPI S3 state. Simply put, the circuit is nearly always live in a kind of sleep state. The difference is minor, but having an off state is important if you want to put these batteries into storage. If we don’t consider chemistry, the ones with an S1-like power state would exhibit the slowest rate of energy leak.

Linear Battery Gauge: Electrovaya no longer uses a digital battery counter. So, all battery gauges are incremental, using bars in an LCD display or multiple LEDs. I have read the manuals to confirm, but several of these batteries have an odd number of indicators or a number that isn't a factor of 10. This means the first LED may indicate a 0-5% charge while the second indicates 5-20%. This is a feature to keep in mind if you need to keep track of how much charge you have left.

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  • sylvain
    Interesting read. Would it be possible to do a similar test for pure USB external batteries. Used for adding that extra bit of juice to an iPad, iPhone or similar devices?
  • Anonymous

    I am interested in using the battery for a DSLR video rig, i want to use the 12v to power the camera, then split the 5v to power both an asus wicast and a SDI to HDMI down convertor. both these last two devices take a 5v feed. would this be possible do you think?
  • Spanamana
    I purchased one of these batteries from a UK supplier and have to say I have never encountered such poor customer service in a long time. They claim that they supply one free tip a year. Rubbish! When you try to get one for a iPad 3 or later, they charge you $10 because they changed the name of it from "tip".

    After 8 months the battery started not keeping its charge. I tried to use the 2 year warranty to get it replaced and found out that although the unit is guaranteed for two years, the battery is only guaranteed for 6 months. Then I was told that it would cost too much to get it repaired as there is no UK repair centre and therefore there is a charge of $30 for a replacement.

    Having delivered the replacement battery, I have not received a VAT order for £21 for import duty from TNT. So a battery that cost me £50 has now cost me £95.

    Shonky product, useless service. Don't waste your money.