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Old 02-03-2002, 12:24 PM   #1
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Default Good Discharge Tray NiMH

Who makes a good discharge tray for NiMH batteries? I'm looking for one to use primarily on sanyo 3000HVs also on some NiCads. Any recommendations? Thanks.
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Old 02-03-2002, 03:23 PM   #2
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I have the Trinity one, but the Pro Match and integy ones are also good.
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Old 02-03-2002, 03:25 PM   #3
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The fastets ones use to be Trinity Real Time 2 and Integy Octane 2. But they also go all the way down to zero volt, which aren't good for NiMh. On NiCd this increase voltage and decrease IR and runtime. Of course, you can choose to manually take the NiMh packs out, when the bulbs goes out.

Or check out the Robitronic equalizer. Auto cut off at 0,9 volt pr. cell. Discahrging at approx 1 amp. www.robitronic.com
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Old 02-03-2002, 03:29 PM   #4
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I'm using the Trinity Real Time 2 discharger.

Positive points: it works very fast, it indicates the discharge of the cell below 0.9 volts by a light per cell that goes out, it has a built in fan that is driven by the battery you discharge (altough I use it more to speed up the discharge then for cooling).

Negative points: it has no automatic cut off so it discharges each cell down to zero volts. This is fine for Nicad but for NiMh it still remains a question if its good for the cells.

On one forum it is said that NiMh have no memory and should be stored partially charged. They should only be discharged just before use.
On other forums i've read that you need to treat them exactly as Nicad.
Who knows what is correct ?

Only thing I have seen is that the cells have an erratic voltage curve if you charge them after they have been discharges down to zero volts.
If you don't have a charger which can be set up not to look at peak drops for say about the first five minutes you will need to restart your charger about four or five times due to false peaking.

It costs about 35 USD on Tower Hobbies. I've attached a picture off it from the Trinity site.

Hope this helps
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Old 02-03-2002, 06:12 PM   #5
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Let the pack rest for a couple hours after it had been brought down the zero volts should have with the false peak problem~
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Old 02-03-2002, 10:36 PM   #6
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Thanks for the responses, are there any dischargers with adjustable or non-0 volt cut off? Also, is it better to get one good robust discharger, or a few simpler ones?
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Old 02-04-2002, 03:11 AM   #7
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Potato,
There are a few dischargers out there with cut off voltage:
fi
Robitronic discharge tray
http://www.robitronic.com/robitronic_e.htm

Team Orion Active discharge device
http://www.team-orion.ch/products/dischargers.asp

You also have a few chargers that have a discharge function build in. I can't really remember which ones but I think the GM chargers have those functions.

As to buying discharges I bought one Trinity discharger and made copies out of it out of wood.
A lot of workinghours but definitly a lot cheaper.
You have to remember that a discharger is really nothing more than a resistor that is put over each battery cell. The resistors I used are 10 watt 0.22 ohms.
Only drawback: no cut off and no lights.
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Old 02-04-2002, 05:20 AM   #8
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Question: is it possible to make a "discharger" by placing a diode and resistor in series with each battery? Granted it will discharge to about 0.7V but still better than 0. Any comments on this?

Thanks!
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Old 02-04-2002, 06:19 AM   #9
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Alvin,
I did that and the theory is correct that you can make it stop discharging at 0.7 volts.
I have made three of those but have the same problem with all three.
I use six cell packs and on each tray one cell refuses to discharge (different packs are used). It's the same with all three dischargers. If i check the resistors with a multimeter all seems fine, in actual use it doesn't work however.
I'll have to open one up and do the soldering again to see if it is a contact problem.
If it doesn't work i'll remove the diodes.

I've made three without diodes and they discharge fine (no cut off, discharge to zero volts per cell).
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Old 02-04-2002, 06:54 AM   #10
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Spillertwo,
you mentioned "on each tray". I assume the battery was placed in a tray, and then the diode/resistor combo connected across each battery. Will that work? I haven't taken apart my discharge tray to see the innards.
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Old 02-04-2002, 10:23 AM   #11
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I meant that I have three trays with diodes and resistors and that when I put a batterypack (six cells each time) on every tray that on each tray one cell of the pack doesn't discharge.
That makes three trays, 18 battery cells and 18 combinations of a resistor and a diode discharging each cell individually

If you take the Trinity discharger apart you can see on the inside that it has 6 resistors simply connected to the posts that you connect to each battery cell.
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