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Old 06-17-2004, 11:29 AM   #1546
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Yea, no kidding. The prices for airline flights is cheaper than gas for the entire trip. I spoke with the family, and it is definite they are not coming! WOOHOO! I made reservations for airline tickets already, thanks for the info.
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Old 06-17-2004, 01:27 PM   #1547
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Old 06-17-2004, 01:38 PM   #1548
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overdrivedgn....keep down man....you're talking too much You coming Saturday?
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Old 06-18-2004, 08:25 AM   #1549
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promatchrcr: no I won't be able to make it down there this weekend. I have too much work to do and not enough time to do it in. oswald and gimp at least will be coming. I heard that eyeman will be there but don't quote me on that one.LOL
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Old 06-18-2004, 08:38 AM   #1550
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That sucks man....I know what you mean though...not enough time in the days... See you at the state race then.
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Old 06-19-2004, 07:28 AM   #1551
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Old 06-19-2004, 09:35 AM   #1552
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Default Problems discharging battery

What am I missing?
I hook my batteries up to a bulb discharger. Lights come on bright, after 2 minutes or so they dim and go off.

I measure voltage of pack it is over 7. I put the batteries on and Octane 2 tray, bulbs light for 30 secs or less and go off.
Voltage is the same.
I attach a motor to the pack until it wont spin any more.
Now I measure around 6.5 volts. I check each cell they are all around 1.3 volts. I finally attached a small electric motor from a toy car and there was more than enough power left in this battery to spin the motor very fast.


I thought the Octane 2 or similar trays lights would stay on until the battery was completely discharged.

I used two different voltmeters.

How can I reliably take these packs down to the recommended 5.4 or .9 per cell level. It is hard for me to believe I am not getting all the energy out of the cell, but if the cells are discharged why do I get the voltage readings I am? Is there another way to measure the voltage.
--------------------------------------------------------------------
... bonus question the current recommendation from every one is charge at 6 amps to maximize "punch" on the other hand almost all of the under $100 chargers charge at a max 4 amps even the latest Team Trinity advertisement in the RC magazines recommends 4 amps. Given the fact I am running stock 1/10 touring and I am a fairly new driver, can I safely assume the difference between 4 and 6 amp charging is relatively small and only of significance to the expert class driver?
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Old 06-19-2004, 09:54 AM   #1553
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Default Differences in chargers?

I see so many different chargers all claiming to do about the same thing.

It appears that they all do one primary task and that is to deliver 4 to 6 amps at 7 or so volts.

The primary difference between them(for NIMH) is how accurately they stop the charging process.

I see a ton of used chargers on E-Bay relatively cheap that were designed for Nicads. As far as I can tell the problem with using these on NIMH is that the peak detection system is not sensitive enough and they go into trickle charge after they shut off the main high amp charging. Other than that they appear the same.

If the charger is AC/DC then it must contain a power supply to transform 110 AC to 7 volt DC, this makes the charger considerably bigger and heavier than a DC to DC unit.
What confuses me is some of the differences between the DC to DC chargers.
I have seen these relatively small chargers like Tekin and the $20 Durtrax Pirahna which are only about 50% larger than a pack of cigarettes and I have seen DC to DC which are 5 times that size.
Is there something significant about the size difference? Are the smaller ones not providing a linear charging current? are they doing something different when it comes to the actual electrical properties of the charge? or is it primarily more circuitry to control the peak detection or ability to adjust the charger that is missing?
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Old 06-19-2004, 10:25 AM   #1554
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Default Re: Problems discharging battery

Quote:
Originally posted by imjonah
What am I missing?
I hook my batteries up to a bulb discharger. Lights come on bright, after 2 minutes or so they dim and go off.

I measure voltage of pack it is over 7. I put the batteries on and Octane 2 tray, bulbs light for 30 secs or less and go off.
Voltage is the same.
I attach a motor to the pack until it wont spin any more.
Now I measure around 6.5 volts. I check each cell they are all around 1.3 volts. I finally attached a small electric motor from a toy car and there was more than enough power left in this battery to spin the motor very fast.


I thought the Octane 2 or similar trays lights would stay on until the battery was completely discharged.

I used two different voltmeters.

How can I reliably take these packs down to the recommended 5.4 or .9 per cell level. It is hard for me to believe I am not getting all the energy out of the cell, but if the cells are discharged why do I get the voltage readings I am? Is there another way to measure the voltage.
--------------------------------------------------------------------
... bonus question the current recommendation from every one is charge at 6 amps to maximize "punch" on the other hand almost all of the under $100 chargers charge at a max 4 amps even the latest Team Trinity advertisement in the RC magazines recommends 4 amps. Given the fact I am running stock 1/10 touring and I am a fairly new driver, can I safely assume the difference between 4 and 6 amp charging is relatively small and only of significance to the expert class driver?
Betteries output a very different voltage whether they're loaded or not... empty batteries will still read out around 7V with no load. If you measure the voltage with your bulb discharger connected, the voltage should be close to zero after lights went down. Now, unhook your bulbs, wait a few seconds, measure again, and it reads 7V! Magic, isn't it? The thing is, there's voltage, but no energy left... HArd to conceptualize, eh?

If you hook an "empty" pack to a toy car motor, it will still spin, only up to a point though.

Later
Paul
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Old 06-19-2004, 11:53 AM   #1555
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Imjonah:

Nimh or Nicad batteries stay at aprox 1.2 volts per cell. .9 is considored dead, but this is under load. After the cell is down to .9 volts per cell, it bounces back up to 1.2 per cell. It is still basicly dead. If you put a light load on it it will still produce power.

What you are doing is dead shorting your packs. Putting a small load on until there is nothing left in the pack is not good for it.

Putting your bulbs on till the cutoff stops them is all needed to do until the day before you race, then tray them (small load per cell) until they come down to .9 volts per cell. See the Promatch Website for their battery care. It is the best. I have a Smart Tray and Its the best thing I bought for my batteries in a long time.


Most of what you said about chargers is true. Cheap ones do not charge at 6 amps. I use 5.5. Also cheap chargers use a pulse charge instead of a nice even linear charge which is important. All I have to do is hook them up to my ocilliscope and I can see if its a pulse or "flex" charge.

I use an old Tekin 112 with H27 software. It works great. I have an Indy 16 X 5 which is awesome because it has a 20 amp discharge feature. I also have a millineum. Good charger cept you have to watch it because it false peaks in the beginning of the charge. The last chartger I have is a paranah digital. Great charger for $50.00. It charges 5 amps when hooked up to DC and only 3 on AC. Otherwise you can set the threshold, # of cells, capacity so it doesn't cook your batteries if it miss the peak (which mine hasn't). It also has 9 charge profiles so you can charge Rx and Tx packs or what evere else you have.

************************************************** *'

And now for the bonus question. 6 amps will give more voltage especially for stock, I don't know if you will notice it or not. BUT 6 amps charges a pack a lot quicker than 4 amps.

************************************************** **
David Root

Last edited by David Root; 06-19-2004 at 12:01 PM.
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Old 06-21-2004, 06:56 AM   #1556
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PMRGirl - DId you get my E-mail about the Mod Nats and the upcoming Cajun Classic ???....I'll give you a ring later this week about it....L8R..

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Old 06-21-2004, 11:35 AM   #1557
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Rod, great prawn convention. Next time we will invite PMRGirl, I know she would get a kick out of it.
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Old 06-21-2004, 12:54 PM   #1558
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-- Battery placement in tray --
I just picked up a Pro Match tray this weekend - I was looking last night, and only 1 of my packs is configured where it can sit at one end of the tray - the other packs (all 6 cell) have to sit in the middle with an empty slot on each end - is this OK? I think I looked at all ways to turn the battery, and couldn't find a way to situate it where it was at one end.

-- How long on tray --
I also read on ProMatch's site to not leave the cells on the tray for over 20 minutes - is this correct? I obviously don't want to question them, -- but -- I thought I had heard/read to leave them on the tray overnight, or at least until the green LEDs go out.

-- When to discharge, tray, charge --
I know this has been gone over in this thread, but the thread is almost too long to dig back through (code for "yes, I'm lazy") - Is this correct?
- after race day, put about 10 minute charge in batteries
- day before race day, discharge at 20A to .9v/cell, then tray for 20 minutes, then fully charge
- race day, repeak

Sorry for all of the questions that I am sure have already been covered - I just picked up the equalizing tray and a deans discharger with black box cut-off - by the way, is the black box adjustable, or is it fixed at it's stop point?
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Old 06-21-2004, 01:05 PM   #1559
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Sounds like the tray you bought isn't for the configuration your batteries are built in except for that one.


It says 20 mins and that is fine,you can leave them on the tray overnight as well; it gives the advantage of deadshorting without the runtime loss.

I am sure everyone has their "way"...I tray them about 30 mins before I charge them on raceday and once a month or so I will tray them overnight.

The Black Box is preset to cutoff at 5.40....
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Old 06-22-2004, 09:21 AM   #1560
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