RCCrawler Forums

pullstarter · 11-10-2005, 11:30 PM

Hey Guys,
Having some issues with my AA nimh's for my TX, the battery alarm is going off yet when i try and charge the cells on my millenium it says they're fully charged no matter how many times i press start they peak within a minute or so of starting. It's set at 4mv threshold and charging at 1amp on ni-cd linear, have also tried it on nimh profile but still does the same thing. Any ideas as to what could cause this?

cheers
simon

EeePee · 11-11-2005, 07:06 PM

Don't use the Nicd charging for Nimh!!!! It's totaly different, and doesn't work the same way.

Set the threshhold for 6mv, and try 0.5 amp.

If you still have problems, try discharging the batteries. I use three 1157 bulbs and take them off the light string when my multimeter shows 0.9 volts per cell while under a load. 7 cells x 0.9 volts = 6.3 volts. Let em cool, charge at 0.5 amp.

pullstarter · 11-11-2005, 11:11 PM

Thanks for the advice eepee i'll give it a go.

EeePee · 11-12-2005, 04:23 AM

Oh, and even with three 1157 bulbs, the AAs will get quite warm, so use either a fan to help keep them cool, or discharge them in intervals, allowing them to cool a little. Or, use only one or two bulbs.

pullstarter · 11-12-2005, 04:29 AM

I just discharged using a resistor I had lying around, got them down to about 7.2v for the 8 cell pack, they did get a bit warm but when i put a computer fan on them they were ok, gonna try charging in the morning, its too late to charge now, will let them cool too, altho i realise they don't need that long lol. Thanks for your help

pullstarter · 11-14-2005, 03:25 PM

Just received an email from Novak in reply to my questions, they say to use the NiCd linear profile for charging AA Nimh's, .5 amp at a 10mv threshold for the first 10-15mins then change back to 4mv after that. I'll give it a try and see what happens i guess, waiting on a discharger from integy so i'll see if that makes a difference also, maybe a few cycles will sort them out.

EeePee · 11-14-2005, 03:46 PM

Interesting.

pullstarter · 11-14-2005, 03:47 PM

Once i get the discharger and give them a few cycles i'll let you know the results.

sim · 11-21-2005, 10:35 PM

How is the charging going? I had the same problem. I think the transmitter battery tray that I am using to hold the batteries has a lot of resistance in it. Was going to solder the batteries together and give that a try but haven't gotten around to it yet.

pullstarter · 11-21-2005, 10:37 PM

the new discharger hasnt arrived as yet, i was thinking of making up a soldered pack too, maybe a 9 cell, might last a bit longer, are you using a millenium too?

RIPPER357 · 11-21-2005, 11:42 PM

I got some energizer 2500's that I've been using and have to charge every 2 hours of use or so. I noticed that they're 1.2v batts where regular alkaline are 1.5v. So basicly imy 3PJ is running 2.4v lower than it expects. Fully charged it shows 10.6v and the alarm goes off at 9.9v.

pullstarter · 11-21-2005, 11:56 PM

Thats why i want to make up a 9cell pack, will almost compensate for the lower cell voltage, mine cuts out at 9.5, fully charged is about 11v but still dont get much run time out of it. There is a pre fab 9 cell pack you can get for the 3PJ i think, not sure if still available tho. Only problem then is you will need a charger that does more than 8 cells and mine doesn't.

SPEED_RACER · 11-22-2005, 05:44 AM

here's an idea.if you need longer run times on the trx.use an 8 cell or 9 cell for that matter and seeing you're thinking of the 9 cell pack,make it out of sub-c cells and the trx will last alot longer.an old trick i've seen 1/12 scale racers use in the past

JohnRobHolmes · 11-22-2005, 08:07 AM

if I can get 2400 AA's why would I use heavy sub-c batteries?

If I was gonna make a custom pack it would be an 8000 mah 3 cell lipoly

sim · 11-28-2005, 08:06 PM

pullstarter,

Ya, I've still got that Novak Millenium Pro. It's small and portable and great for charging 3300 mAH sub-c's. But for charging AA's it's really reluctant. I've heard you need something like a 20A power supply for it to work and even then you still need to charge at a low rate.

I've tried it with a 28A power supply at 1A and it still false peaked before the batts got anywhere close to being warm, so I gave up on that.

I think I'm having sort of the same problem as most guys with digital transmitters because I have an Airtronics MX-3 and the alarm comes on at about 8.8v and its loud and annoying and there's no way to turn it off. I can still play for another 15-20 minutes after that but it's really annoying.

Right now I'm charging the AA's individually with one of those chargers that take up to 4 at a time. I got 2 of them (mine are Johoyo brand and takes about 3 hours to fully charge the 2500s). Haven't had the chance to test out a full charge yet.... so far so good... but if it runs below 8.8 very quickly then it's time for the last resort - which is to make the 9-cell pack. I'll find 8 more AA's and make a 9-cell pack (and use the other 7 to make a 7-cell pack for the crawler).

So far I've really been reluctant to solder the nice AA's together because I keep thinking I might find some other use for them apart from the transmitter.

We'll see how they behave first

sim · 11-28-2005, 08:15 PM

RIPPER357,

You charge the batteries with an AA-type charger or you just charge them while they're inside your transmitter?

RIPPER357 · 11-29-2005, 10:04 AM

I went the cheap route and bought the 8 hour charger/batt combo. I bought the TX used and didn't get a cord with it.

sim · 11-29-2005, 08:14 PM

And you're still having to charge your batts every 2 hours of use?

Sounds like I'm due for another charging soon then.

RIPPER357 · 11-30-2005, 10:38 PM

Thats just a rough guesstimate, haven't really timed it tho. Plus theyre still new and not broken in yet.

sim · 12-05-2005, 06:46 PM

Okay, so far I think the batteries are lasting a lot longer each charge with the dedicated AA chargers that charge the cells individually (compared to putting them in the transmitter battery tray and charging through that with a charger in 8-cell mode).

So far it's only been about 40 minutes of use plus a week of leaving them in the transmitter and they're still at 10V, which is definitely better than what they used to be with my old charging method.

I guess I won't solder them up afterall

11-10-2005, 11:30 PM	#1
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	AA nimh charging problems Hey Guys, Having some issues with my AA nimh's for my TX, the battery alarm is going off yet when i try and charge the cells on my millenium it says they're fully charged no matter how many times i press start they peak within a minute or so of starting. It's set at 4mv threshold and charging at 1amp on ni-cd linear, have also tried it on nimh profile but still does the same thing. Any ideas as to what could cause this? cheers simon

11-11-2005, 07:06 PM	#2
EeePee MODERATOR™ Join Date: Jul 2004 Location: Ohio Posts: 18,928	Don't use the Nicd charging for Nimh!!!! It's totaly different, and doesn't work the same way. Set the threshhold for 6mv, and try 0.5 amp. If you still have problems, try discharging the batteries. I use three 1157 bulbs and take them off the light string when my multimeter shows 0.9 volts per cell while under a load. 7 cells x 0.9 volts = 6.3 volts. Let em cool, charge at 0.5 amp.

11-11-2005, 11:11 PM	#3
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	Thanks for the advice eepee i'll give it a go.

11-12-2005, 04:23 AM	#4
EeePee MODERATOR™ Join Date: Jul 2004 Location: Ohio Posts: 18,928	Oh, and even with three 1157 bulbs, the AAs will get quite warm, so use either a fan to help keep them cool, or discharge them in intervals, allowing them to cool a little. Or, use only one or two bulbs.

11-12-2005, 04:29 AM	#5
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	I just discharged using a resistor I had lying around, got them down to about 7.2v for the 8 cell pack, they did get a bit warm but when i put a computer fan on them they were ok, gonna try charging in the morning, its too late to charge now, will let them cool too, altho i realise they don't need that long lol. Thanks for your help

11-14-2005, 03:25 PM	#6
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	Just received an email from Novak in reply to my questions, they say to use the NiCd linear profile for charging AA Nimh's, .5 amp at a 10mv threshold for the first 10-15mins then change back to 4mv after that. I'll give it a try and see what happens i guess, waiting on a discharger from integy so i'll see if that makes a difference also, maybe a few cycles will sort them out.

11-14-2005, 03:46 PM	#7
EeePee MODERATOR™ Join Date: Jul 2004 Location: Ohio Posts: 18,928	Interesting.

11-14-2005, 03:47 PM	#8
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	Once i get the discharger and give them a few cycles i'll let you know the results.

11-21-2005, 10:35 PM	#9
sim Quarry Creeper Join Date: Apr 2005 Location: Malaysia Posts: 374	How is the charging going? I had the same problem. I think the transmitter battery tray that I am using to hold the batteries has a lot of resistance in it. Was going to solder the batteries together and give that a try but haven't gotten around to it yet.

11-21-2005, 10:37 PM	#10
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	the new discharger hasnt arrived as yet, i was thinking of making up a soldered pack too, maybe a 9 cell, might last a bit longer, are you using a millenium too?

11-21-2005, 11:42 PM	#11
RIPPER357 Newbie Join Date: Sep 2005 Location: Anchorage Posts: 43	I got some energizer 2500's that I've been using and have to charge every 2 hours of use or so. I noticed that they're 1.2v batts where regular alkaline are 1.5v. So basicly imy 3PJ is running 2.4v lower than it expects. Fully charged it shows 10.6v and the alarm goes off at 9.9v.

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11-21-2005, 11:56 PM	#12
pullstarter Pebble Pounder Join Date: Apr 2005 Location: Australia Posts: 153	Thats why i want to make up a 9cell pack, will almost compensate for the lower cell voltage, mine cuts out at 9.5, fully charged is about 11v but still dont get much run time out of it. There is a pre fab 9 cell pack you can get for the 3PJ i think, not sure if still available tho. Only problem then is you will need a charger that does more than 8 cells and mine doesn't.

11-22-2005, 05:44 AM	#13
SPEED_RACER Quarry Creeper Join Date: Nov 2004 Location: MANVILLE Posts: 413	here's an idea.if you need longer run times on the trx.use an 8 cell or 9 cell for that matter and seeing you're thinking of the 9 cell pack,make it out of sub-c cells and the trx will last alot longer.an old trick i've seen 1/12 scale racers use in the past

11-22-2005, 08:07 AM	#14
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	if I can get 2400 AA's why would I use heavy sub-c batteries? If I was gonna make a custom pack it would be an 8000 mah 3 cell lipoly

11-28-2005, 08:06 PM	#15
sim Quarry Creeper Join Date: Apr 2005 Location: Malaysia Posts: 374	pullstarter, Ya, I've still got that Novak Millenium Pro. It's small and portable and great for charging 3300 mAH sub-c's. But for charging AA's it's really reluctant. I've heard you need something like a 20A power supply for it to work and even then you still need to charge at a low rate. I've tried it with a 28A power supply at 1A and it still false peaked before the batts got anywhere close to being warm, so I gave up on that. I think I'm having sort of the same problem as most guys with digital transmitters because I have an Airtronics MX-3 and the alarm comes on at about 8.8v and its loud and annoying and there's no way to turn it off. I can still play for another 15-20 minutes after that but it's really annoying. Right now I'm charging the AA's individually with one of those chargers that take up to 4 at a time. I got 2 of them (mine are Johoyo brand and takes about 3 hours to fully charge the 2500s). Haven't had the chance to test out a full charge yet.... so far so good... but if it runs below 8.8 very quickly then it's time for the last resort - which is to make the 9-cell pack. I'll find 8 more AA's and make a 9-cell pack (and use the other 7 to make a 7-cell pack for the crawler). So far I've really been reluctant to solder the nice AA's together because I keep thinking I might find some other use for them apart from the transmitter. We'll see how they behave first

11-28-2005, 08:15 PM	#16
sim Quarry Creeper Join Date: Apr 2005 Location: Malaysia Posts: 374	RIPPER357, You charge the batteries with an AA-type charger or you just charge them while they're inside your transmitter?

11-29-2005, 10:04 AM	#17
RIPPER357 Newbie Join Date: Sep 2005 Location: Anchorage Posts: 43	I went the cheap route and bought the 8 hour charger/batt combo. I bought the TX used and didn't get a cord with it.

11-29-2005, 08:14 PM	#18
sim Quarry Creeper Join Date: Apr 2005 Location: Malaysia Posts: 374	And you're still having to charge your batts every 2 hours of use? Sounds like I'm due for another charging soon then.

11-30-2005, 10:38 PM	#19
RIPPER357 Newbie Join Date: Sep 2005 Location: Anchorage Posts: 43	Thats just a rough guesstimate, haven't really timed it tho. Plus theyre still new and not broken in yet.

12-05-2005, 06:46 PM	#20
sim Quarry Creeper Join Date: Apr 2005 Location: Malaysia Posts: 374	Okay, so far I think the batteries are lasting a lot longer each charge with the dedicated AA chargers that charge the cells individually (compared to putting them in the transmitter battery tray and charging through that with a charger in 8-cell mode). So far it's only been about 40 minutes of use plus a week of leaving them in the transmitter and they're still at 10V, which is definitely better than what they used to be with my old charging method. I guess I won't solder them up afterall

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