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Battery dies in 2 minutes

Battery dies in 2 minutes

Old 06-27-2020, 02:15 PM
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Default Battery dies in 2 minutes

I recently broke out two Traxxas Stampede's that have been sitting in my basement for 14 years. I sprayed and cleaned out the motors with electrical small parts spray and lubed all the moving parts. My original batteries we not charging so I just bought two "Powerextra" 6 cell 7.2v 3600mAh NiMh batteries off Amazon.

I charged the batteries with my original Hobbieco 910 charger that has a 15 min twist dial timer. I cycled and ran them several times in the cars. The needle gauge shows they charge at about 2a or a little more. When taken off the charger the batteries are at about 8.25v.

The cars run for about a two minutes each and then putter out. The battery shows about 6.2v after resting for a few minutes.

Am I not charging the batteries enough, are the batteries garbage or does it have something to do with the old cars killing the batteries too fast?

When the cars are running they appear to be running fine.

Last edited by Brianosaur; 06-27-2020 at 02:29 PM.
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Old 06-27-2020, 03:24 PM
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Found an online old brochure for that charger:

The Hobbico Model 910, Variable Rate AC/DC Multi-Charger is a most versatile charger It's variable rate current adjustment lets you charge any NiCd battery pack containing four to seven cells of 500mAh to 1700 mAh capacity in fifteen minutes It super heavy duty transformer can pump out charge after charge without overheating Other deluxe features include a dependable 15 minute timer, an accurate ammeter, voltage monitoring jacks, trickle pilot light and charge and discharge circuit
15 minutes isn't going to be enough to fully charge 3600mAh with that charger. From what I can tell, that charger will do a max of 3.5 amps so you are looking at a little over an hour to charge a 3600 battery fully (provided it can maintain around 3.5 amps for charging).

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Old 06-27-2020, 05:31 PM
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Doesnt want to go over the 2.0-2.5a mark. The needle meter shows 3.0-3.5a in green but it wont go that high.
Charging voltage is about 9v while connected.
Ran it through three times and the battery doesnt go over 8.3v after a little resting period.
My old batts were 1900mAh so the 15min at that amperage worked well if I remember correctly.

What should my fully charged voltage be?
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Old 06-27-2020, 06:18 PM
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either stepup to a more modern charger , and if your gonna use a old school charger then its gonna take way longer than 16 minutes to charge those cheap nimh packs..so at 2 ish amps its nowhere near A fully charged battery....nimh always do best with a condition charge then disharge at work your way up to 3.5 amp charge rate...a condition charge is the slowest rate your charger can do into those batt might take some 15 + hours but always works best ...if you want to stay in the vintage chargers .get a tekin bc 112... all depends what software version is on it ... look 4 one that shows in the 20's when 1st powered on.I think ver 26 was last .but unsure
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Old 06-27-2020, 06:43 PM
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Originally Posted by the rc guy View Post
either stepup to a more modern charger , and if your gonna use a old school charger then its gonna take way longer than 16 minutes to charge those cheap nimh packs..so at 2 ish amps its nowhere near A fully charged battery....nimh always do best with a condition charge then disharge at work your way up to 3.5 amp charge rate...a condition charge is the slowest rate your charger can do into those batt might take some 15 + hours but always works best ...if you want to stay in the vintage chargers .get a tekin bc 112... all depends what software version is on it ... look 4 one that shows in the 20's when 1st powered on.I think ver 26 was last .but unsure
Yeah, I don't want to be fighting this old charger. I will buy a new one.
Any suggestions? Would like to keep it under $75 if possible.

I am not stuck on these batteries either. Should I get different ones? These new ones can go back w/ Amazon Prime if they are knock-off pos.

Was just looking to break out the old cars and play with them a bit with my 12yo, but not really looking to dump hundreds of dollars into it.
I originally used them with my older son but he's out of the house now and thats why they've been sitting for years.
I just want to mess around with them while camping as we recently got a travel trailer and I see kids with rc cars here and there at campgrounds.

What the most efficient, and cost reasonable, set up to get my old 7.2v Stampedes up and running again?

Thanks for the help.
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Old 06-27-2020, 08:31 PM
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Id take a look at this charger.it will charge just about any battery we use in rc and you can set it to charge at a much higher amperage and a low conditioning rate. the toolkit M8 or even M6.. you will need a 12volt power supply. I made a 12.4 volt power supply from a computer power supply a little time and a few parts and your set....many online tutorials to help you convert the atx to a bench power supply...amazon is where to get that charger.id also look into a 2 cell lipo in the 5000mah + range ..about 50c will be fine. run times will exceed 25 minutes so take a break after about 8 and lets things cool off...
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Old 06-28-2020, 08:08 AM
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Here's a good charger within your price range:

https://www.amainhobbies.com/hitec-r...c44245/p535970

One of the benefits is that it can be AC or DC (should you need/want DC).

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Old 06-28-2020, 04:45 PM
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Originally Posted by the rc guy View Post
Id take a look at this charger.it will charge just about any battery we use in rc and you can set it to charge at a much higher amperage and a low conditioning rate. the toolkit M8 or even M6.. you will need a 12volt power supply. I made a 12.4 volt power supply from a computer power supply a little time and a few parts and your set....many online tutorials to help you convert the atx to a bench power supply...amazon is where to get that charger.id also look into a 2 cell lipo in the 5000mah + range ..about 50c will be fine. run times will exceed 25 minutes so take a break after about 8 and lets things cool off...
Can I run a Lipo battery in my cars?
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Old 06-28-2020, 07:54 PM
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brushed or brushless you can run a lipo.. Nixx batteries used to come off the charger at more than 9 volts sure they discharge faster than a lipo....8.4volts should be no problem 4 a pede..xl5 12 turn titan.. no issue running a lipo.
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Old 06-28-2020, 09:10 PM
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Try charging for an hour with your current charger and see how it does
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Old 06-29-2020, 08:27 AM
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If you use a lipo remember if you run the voltage down too low your battery will puff and be no good. Cheap insurance to put in an esc with low voltage cutoff. Car will be tons faster with the lipo over a nimh.
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Old 06-30-2020, 12:08 PM
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I just checked the manual for the Hobbico 910 (http://manuals.hobbico.com/hca/hcap0175-0190-manual.pdf) and it appears that if the voltage drops .02 during quick charging that it may automatically switch to trickle charging to protect the battery from damage. I've had some Nihm batteries that could be finicky and would false peak causing problems with charging. In cases such as those, I would check the batteries to see if they were warm to the touch. If they weren't, I would charge them for an additional cycle. Eventually after multiple cycles of charging, the batteries would get warm and be fully charged. Always monitor your batteries at all times especially if you are having to use multiple cycles to fully charge them.

As Nihm replaced Nicad as the batteries of choice in racing, battery chargers began to incorporate false peak and/or voltage drop options in them. Basically the charger would have the option of ignoring brief voltage drops or your could set a larger range for the voltage drop to continue to charge the pack through the "false peak". You can often find good deals on many of the used chargers that were considered high end when Nihm batteries were standard. Even new chargers should have this option. Here is an example of 2 different Duratrax Onyx chargers that I did a quick comparison of. Note on the comparison what the different peak detection (mV) are between the chargers.
https://www.duratrax.com/chargers/on...P4192+DTXP4211

Most people who raced when Nihm was the standard would charge the batteries until they were hot (which can be dangerous) to get the most charge they could in them. Just know that an over-charged Nihm battery can explode if it can't properly vent gasses and may explode even if it can. If you ever notice a Nihm battery that is leaking liquid from inside, is getting deformed/getting larger, or is hissing when charging, that battery is damaged and could be dangerous. Here is a good video on Youtube showing someone who deliberately over-charges a 7-cell Nihm battery in a controlled manner to illustrate what can happen.
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