battery question

~losi 8 1.0 rtr receiver battery pack nimh 1700 mah with supplied charger. my question is...

i was at the hobby store the other day and the guy behind the counter said something about needing to 'deep cycle' a battery after 5 or so cycles (1 cycle being a charge and discharge of the battery) he told me to hook the battery up to a light bulb until the light goes out and then immediately charge the battery fully(instructions say takes 12 hours with supplied charger that came with the rtr/battery). hook it back up to the light until it goes out again and immediately give it a full charge and then its good to go...

any comments or suggestions on this procedure, did the guy tell me the right thing??? I'm about 5 cycles on my battery and wondering if i should do this 'deep cycle' procedure.

thanks in advance.. Rock Chalk

Thanks for the help..

This phrase is meaningless. It may explain the lack of response, people don't know what you have(?)

The procedure from the counter-guy is unnecessary and has a risk of degrading your battery.

With a receiver battery, it may be 4-cell (4.8v) or 5-cell (6v). If it's a battery pack for an electric-powered plane, the battery could be any number of configurations; e.g. from 5-10 cells (6 - 12v).

In any event, "deep cycling" a NiMh battery serves no purpose. Nicad cells are subject to a "memory" phenomenum which is alleviated by a deep-discharge cycle. NiMh cells do not suffer from the "memory" phenomenum.

NiMh cells do benefit from a series of "forming" charge/discharge cycles about 3 cycles. Each cycle: slow-charge (12-16 hours at the C/10 charge rate) (e.g. your battery: 1700/10 = 170 ma); followed by a slow-discharge (~300-500 ma rate) until the cells drop to no lower than 1v per cell: 4-cell => 4v; 5-cell => 5v. These cut-off voltage levels are to avoid any reverse charging of any one cell. (For extra safety, many people recommend a discharge cut-off at 1.1v per cell.) The "forming" cycles help the NiMh battery cells develop their full capacity (e.g. the full 1700mah for your battery).

Losi 8 1.0 rtr= Team Losi Eight buggy, first version, Ready-to-Roll package

Sorry for the confusion. Also the battery is 1100 mah not 1700mah, 5 cell hump pack nimh...

How do I perform this "forming" charge procedure, with the supplied charhger? I asked the guy if he was referring to nicad batteries and he said "no, I deep cycle all my batteries, nicad's, nimh's and lipo's."

Thanks

Short answer: You need more equipment.

If you had a programmable “smart” charger, you could program in the desired charge-discharge cycle.

Your present charger will perform the charging at an acceptable 12 hour, “slow” charge-rate. However, to properly manage the “discharge”, you’d need an ammeter and a group of resistors to set up an accurate discharge current, and a voltmeter to monitor the voltage. A low-cost digital multimeter would suffice.

Instead of using the ammeter and resistors, you could use a 6v lantern bulb and accept whatever discharge-current that the bulb causes.

In any event, you would continually monitor the battery voltage (while the battery is “under load”, lighting up the bulb), and then stop the discharge when the voltage drops to 5-5.5v. This discharge procedure could take several hours. Thus, the reason for inventing the smart charger/discharger that automatically monitors the voltage and cuts off the discharge.

As mentioned before, in my view, “deep-cycling” a NiMh cell serves no purpose; it also uses up the cycle-life of the cell, and may damage a cell if one cell drops its voltage faster and gets “reverse-charged” by the other cells in the battery pack.

Deep-cycling a LiPo (lithium-polymer) cell below ~2-2.3v can ruin it; oftentimes the cell will no longer accept/hold a recharge.

However, some lithium cells are specially designed for deep-discharge use; for example, Li-Fe (lithium-iron) chemistries (e.g. “A123” cells) developed for cordless power tools.