Charge USB battery with any USB charger or not?

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Charge USB battery with any USB charger or not?

Postby samiam » Wed Sep 04, 2019 10:04 am

I have several of the USB Battery Packs used in T-Link3's and my emitters. I also have a variety of USB chargers I use to charge these batteries. I do notice a few of the chargers take a long time to charge up the batteries. Does not seem to be relative to a battery pack but related to the charger.

As an example, I have a 6-port USB hub and can charge six batteries at a time but it takes an average 12 hours to fully charge. Compare this to using the wall charger from my phone which charges in about 9 hours. I have been told the reason for the charge time difference is the rate of charge which makes sense and this is different from the Raceamerica charger. Why is this different? and is it okay to charge batteries at a slower charge rate like my hub?
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Re: Charge USB battery with any USB charger or not?

Postby MannerTee » Wed Sep 04, 2019 10:11 am

I am experiencing the same long charge time as well. I have three 4-port USB hubs and use them to charge all my batteries. It does take about 10 hours to charge a battery so I charge overnight which I have been told is not good for the battery over time. I thought the batteries would charge in a maximum of 8 hours as advertised.
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Re: Charge USB battery with any USB charger or not?

Postby raceamerica » Wed Sep 04, 2019 2:34 pm

Not all USB chargers charge with the same concept. USB chargers simply output current and voltage to the battery pack within set parameters and charging is actually controlled by the battery's internal charge circuitry.

Multi-port hubs are generally not chargers, they will however charge the battery. If the hub is powered by an external AC adapter, check the adapter for its output voltage. If 5vdc, check the current output of the AC adapter. Divide the output current by the number of ports and that will be the approximate charging current level. The USB Battery Pack can charge at a maximum input current of 1.0A. The lower the charging current level, the longer it takes to charge the battery.

PC USB ports generally have a total output current level of 0.5A for USB 2.0 and 0.8A for USB 3.0. This will charge the battery but with a longer charge time.

Most standard USB chargers for a smartphone will charge the USB Battery Pack. They vary in output voltage and current and thus, charge time will vary.

The biggest most important charge variable is what the USB charger does when the battery is fully charged indicated by solid green on the battery pack. When the battery first enters the solid green state, the battery's internal charging circuit disconnects from the USB charger and measures the internal battery charge level of the battery. It then reconnects the USB charger and measures the current level flowing into the battery (very low at this point with a fully charged battery). Trickle charging continues and the disconnect, check battery, reconnect sequence repeats. Once the battery's internal charge circuitry detects full charge has been attained, it shuts off and no longer charges the internal battery.

The issue here is when most inexpensive USB chargers are disconnected from the battery, their voltage output changes to reflect no load. When the battery circuitry reconnects to the USB charger, it senses a higher outside voltage and a momentary higher trickle charge current results. The charge circuitry is fooled into thinking the battery is not yet fully charged and sometimes will enter back into full charge mode until the next measurement cycle. This is why is is best not to repeatedly leave Lithium batteries connected to a USB charger overnight beyond the full charge point. A little overcharging occurs once in a while and that is okay but repeated overcharging will see the battery's full charge level slowly decay over time due to the overcharging is damaging very small portions of Lithium chemistry each charge cycle resulting in less Lithium to charge.

Why did RaceAmerica design their own battery charger? All of this was considered when RaceAmerica designed the model 5500 Desktop Charge Station which operates differently when full charge is attained. This battery charger consists of 8 separate battery ports and circuits, one for each battery. Each charge port keeps the charge voltage constant and controls the charge current level so no overcharging will occur or is greatly reduced extending the life of the Lithium batteries. The circuitry is designed to work with the battery's internal charge circuitry to turn down the trickle charge current and optimize the battery's sensing of when full charge is attained, then the battery's circuitry can shut off and disconnect the charger from charging the battery.

Most USB chargers do not have circuitry to monitor when the battery nears full charge so best practice is to remove the battery pack from the USB charger when fully charged. This will extend the life of the Lithium and lengthen the useful life of the battery pack.
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