My Old Charger Has 10 amp Rating, Whats The Big Deal?

Your old charger says it can produce 10-20 amp. So what's the big deal??

This area is an area that is commonly misunderstood and an area that we get asked about a lot here at iCharger NZ.

Much like the "power rating" of mini systems and certain lower end amplifiers that boast 100's of watts of power, what they actually fail to mention in that this rating isn't what is actually delivered to the speakers, but an overall power consumption of the unit. So you may wonder how such a small box has the potential of so much power and in theory is much louder than that very expensive precision engineered German amp? Well, in reality, it doesn't come close.

Your old charger might boast a maximum current of 10 amps or even 20 amps, but if it doesn't have the adequate power potential, it will never be able to provide that current to your battery during the whole battery charging process. Which means your overall battery charging time will be much longer than expected and you will never see it reaching even close to the 10 amps it is claiming to deliver.

The theory is that the more current you have, the faster you can charge. Although it is not recommended to charge any battery faster than its recommended charging "C" rate (rating of charge and discharge). If you battery boast a charging "C" rate of 3C or 4C, in theory you should be able to charge this pack very fast. But if your charger doesn't have the output power, this will never be achieved.

If you are still new to battery terminology and want to better understand "C" rating, "S" rating and capacities we recommend you read our article about understanding Lipo batteries located here.

Back to your old charger… here is an example; say you have a standard 3000 mah 3 cell Lipo, each cell in a Lipo battery pack is rated at 4.2 volts fully charged. In this example, this battery packs voltage rating would be 12.6 volts nearing full charge with a 3000 mah capacity or 3 amps capacity. If you wanted to charge this at 1C (1 x the capacity rating) the charge current would need to be 3amps. Based on that logic, if you were to charge it at 2C (2 x the rated capacity) the charge current would be 6 amps. Therefore your 10 amp rated charger would knock this out of the park right? No sir, not necessarily. There is another very important factor that comes into play regarding whether the battery charger will deliver the current needed to charge at 1c or 2c. That is the wattage!

In this example, when the battery pack is nearing its full voltage of 12.6 volts and being charged at 1c (1 x capacity rating of 3amps) it will be drawing 38 watts of power. Worked out by multiplying the voltage by the current. 12.6 volts x 3 amps = 38 watts. If you were to charge this at 2C (2 times the rated capacity of 3 amps) this equation would result in 76 watts and so on. This does not take into account any energy loss in input voltage, leads etc. Energy will be lost from heat in the battery, leads, input power and general circuitry. Let's say you will never charge anything higher than 2C, based on our 3000 mah 3 cell example packs, you will need a charger rated not only at 6+ amps, but also 76 watts or higher power rating.

If you old charger can only deliver 45 watts for example, but boasts a 10 amp charge rate, it would only be able to deliver about 3.6 amps when the 3000 mah 3 cell Lipo in our example is nearing its full charge voltage of 12.6 volts (45w divided by 12.6v = 3.6 amps). As you can see, even though the charger is rated at a maximum 10 amp charge rate, it would only be able to deliver 3.6 amps at 12.6 volts and that is not taking into account any efficiency losses that are usually in the 10 to 20 percent range reducing the charge current even more.

So why can the charger manufacturer in this example claim a maximum charge rate of 10 amps?

Well, depending on the voltage of the battery you are charging, a 10 amp charge rate can be achievable. If you were charging a single cell Lipo pack for example (4.2 volts fully charged) on this 45 watt charger, at that voltage it will be able to deliver about 10 amps (45w divided by 4.2v = 10 amps). The manufacturer is certainly not lying about the maximum charge rate, but if they also exclude the wattage rating of the charger, you are not getting the whole picture. Which may, or may not explain why it takes so long to charge those batteries.

With the progress of battery technology over the last few years, particularly with Lithium cells, and new battery charging techniques, such as balance parallel charging (covered in another article on this website) even a 60 watt charger will be limiting and won't be a an adequate future proof solution.

iCharger uses advanced synchronous buck boost DC/DC converter technology with an output conversion efficiency that can reach over 90%. With the entry level iCharger 106B+ carrying a rating of 250w with a maximum current of 10amps. While the top model iCharger 3010B carries 1000 watts of power with a maximum current of 30 amps. Allowing fast charge rates of any type of battery configuration. This is a completely future proof solution for all your charging needs.

**Please note that in order to achieve these power ratings, the power rating of the power supply running the charger is also a factor. Input voltage multiplied by maximum available input current draw.