FAQ
What is the difference between Current (Amps), and Power (Watts)?
Power (Watts) is derived by multiplying the application Voltage x Current required. Conversely, the amount of Current can be calculated by dividing Power/Voltage where Voltage is the battery pack voltage.
Can different cells of the same size and capacity handle separate applications differently?
Yes. NiMH cells can be designed to handle different types of loads. For example, a cell that has high capacity may not handle a high discharge rate. Also a cell that has a high discharge rate may not have high capacity. It is important to fit the cell to the application, and not just look for a capacity value.
What is the self-discharge rate of NiMH?
It is generally accepted that the self-discharge rate of NiMH is 1/64 of the cell capacity per day, however this can change slightly from cell to cell. Environmental temperature can also accelerate or decelerate this process.
What are the methods for determining NiMH battery pack available capacity at any time during its usage?
There are several methods of determining capacity of a NiMH battery pack, however some are not as accurate as others. Probably the most inaccurate method is to use the packs terminal voltage as an indicator. This is due to the relatively flat voltage profile of NiMH during discharge. The most accurate method is coulombmetric counting. In this method, the current passing in and out of the pack is measured and added or subtracted from the capacity on record.
Is a Polyswitch and a Klixon the same?
A Polyswitch and a Klixon are not the same. A Polyswitch uses a crystalline polymeric substrate that becomes amorphic during an over current to open the circuit. It can also be tripped by over-temperature but is much slower in reaction. It should be used primarily for over current protection. It should only be used as a temperature device in the rarest of applications.
A Klixon uses bi-metal contacts that open when heated to a specified temperature. The Klixon also incorporates a conductor that acts as a heater during over current which forces the bi-metal contact open. It should be used primarily for temperature, but is also a good current protection device.
Should NiMH batteries be "Float" Charged like Lead Acid batteries?
No. The voltage profile of NiMH is unlike that of Lead Acid. However, modifications may be made in rare instances, but only under the guidance of engineering.
What is the self-discharge rate of Li-Ion?
The self-discharge rate of Li-Ion is very low. We can expect to see between 1%-3% per month with the Li-Ion technology. This compared to the NiMH chemistries of 40%-50% per month.
What is the best way to store Li-Ion?
The best way to store Li-Ion is at 40% charge at 25°C. Storing Li-Ion in this manner will provide for 98% of initial capacity after one year. If the cells were stored at 100% charge there will only be 96% or less. Fully discharged storage is not recommended because Li-Ion does not accept over-discharge well.
What is a PCM?
A PCM (Protection Control Module) is a PCB used to enhance the safety of a Li-Ion battery. It accomplishes this task by monitoring voltage and current. It will open the circuit between the battery and charger/appliance when the voltage goes over or under the pre-defined levels. It will also open the circuit if the current reaches a level that is not safe. This type of board is needed on all Li-Ion packs.
Is Li-Ion charged differently than NiMH?
Yes! NiMH is generally charged using a "Constant Current", where Li-Ion uses a "Constant Current/Constant Voltage" charge method.
What is the range in voltage of unloaded NiMH & Li-Ion cells from 100%-0% state of charge?
Most could tell you that the nominal voltage of Li-Ion and NiMH is 3.6(7)V and 1.2V respectfully, but that is only part of the difference. NiMH cells have an unloaded full charge voltage of about 1.35-1.40V and an end of discharge voltage around 1.00V. During 70% of the discharge, at rates less than 1C the voltage will be stable above 1.2V. Li-Ion on the other hand has a full charge voltage of 4.20V and a discharge termination voltage of 2.70V. The Li-Ion voltage will have more linear decreasing voltage from 4.2-3.0V.
What is a SMB or SBS compliant gas Gauge?
SMB (System Management Bus) or SBS (Smart Battery System) are industry standards that allow for battery pack/application communication using two wires(clk/data). The standard communication protocol is SBS 1.1. This protocol is integrated into a PCB that is attached to the battery pack. Cardio Dynamics uses this technology.
Do we have Gas Gauges in stock?
No. We do not have Gas Gauges in stock. This item must be customized for each application individually. There are lead times involved when producing a new application gas gauge.
Where are your products manufactured?
Harding has operations in the US and China to serve all customer needs.
Can you fast charge NiMH batteries?
With proper termination you can fast charge (as fast as one hour).
Does NiMH have memory effect like NiCD technology?
No, Harding's NiMH does not have the same issues of memory like NiCD's.
Do you recommend NiMH technology to be used as inplantable batteries?
The use of NiMH batteries are not recommended as inplantable batteries.
