Battery questions

[navspecwar]

i got a buncha questions bout batteries.

NiHM has longer runtime than NiCD, but less punch, right?

do NiMHs need to be discharged?

it seems to me that battery charging is highly complex, and requires high precision and expertise. what exactly do i need to do to get the most outta my NiCDs? i have a cheapo quick charger (30min fast/unlimited)?

[Shakes]

Yes NIMH batteries have a longer run time and with the newest cells on the market we are seeing more voltage than NiCad's. So now we are getting the best of both worlds. More volts and longer run times.

From what I have heard NIMH do still need to be discharged, but they don't have the memory buildup like NiCad's do. When I store mine for over a week I make sure that the battery is fully charged. Then before racing I cycle them a couple of times to get them ready. I have also heard you do not want to store NIMH for a long period of time completely discharged.

To get the most out of any battery use a peak charger. That way there is almost no chance of them overcharging and you are getting the most charge into your battery.

If you are charging NiCad's using a flex charger of some type seems to bring life back into old batteries. They recommend not using flex charging on NIMH or trickle charging NIMH batteries.

I charge my Nicad's at 4 amps with flex on. I discharge at 30 amps. For my NIMH batteries I charge at 4 amps also but I use regular peak charging mode with them. I discharge at 30 amps also. I will then repeak my batteries right before I race so that the voltage spikes up a little.

There are many good chargers out there that are relatively cheap. You will find that your batteries will get more run time, I am almost certain. Besides with the cost of good batteries now, why not spend the money to charge them properly.

[navspecwar]

yea, i have an MRC 959 on backorder right now. anyway, what is cycling, and what is flex? thanks for the replies.

[sosidge]

Cycling is where you give something a full charge and then a full, constant, discharge.

Flex is just a kind of charging, but for NiMH's use linear, which is fine for everything.

[IanMan]

If your running Nicads, one of the best investments you can make is a discharge board. Are you running cells that are assembled side by side, in saddle packs, or stick packs(3 end to end next to 3 end to end, in a tube)? Saddles or side by side packs will allow you to use a discharge board, aka Discharge Tray. Integy and Trinity make really nice ones. These boards discharge the cells down individually, to equalize them. This erases the "memory" in the cell and ensures that you'll recv a full charge.

Just run the car 'till it Dumps, drop the pack in the tray 'till the lights all go out, pull it out and stick it in your pit box.

Nimh's are more of an issue. I won't list my Nimh maintenence on-line because I'm tired of hearing about the way I'm destroying my packs. I will tell you though, no-one actually knows how to treat Nimh cells yet, and at the rate new Nimh's keep popping up we'll never know.

[highroller]

If you are not racing competitively, or using matched cells all you need to be concerned with is getting the battery fully charged and discharged after use. Batteries get warm or their voltage began to drop when fully charged. On timed chargers with the analog meter will show a voltage drop as the pack starts reaching peak voltage. You can use a variety of things to discharge a pack - running, light bulb(s), motor or voltage resistor.
Packs that use unmatched cells generally don't last as long as the matched racer cells, when you subject them to high charge voltages and high discharge voltage it usually causes the weak cell to go bad. Stick with a 4-5 amp charge and 2amp discharge stopping the voltage at 5 volts.
The matched race cells can be subjected to charge rates of 4-10amps and discharged at 35 amps. With the NiMh cells you will get 12 different ways to care for them, use the method that works for you.
I've tried different methods of storing NiMhs- fully or partially discharge and a few that were dead shorted. Whatever methods I used full or partially charged (lost runtime), discharge (voltage increase, lost less runtime) deadshorted (not recommended)-lost runtime, increased voltage. It took 3-5 cycles before these cells came up to hold a normal charge. It took 2 cycles with the others. Some of the first generation Panasonic cells that showed promising numbers didn't perform that way on the track while the older Sanyo were opposite. They still weren't good race packs but a little better than practice packs.