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Recondition this Ni-Mh battery?

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Old 04-15-2018, 06:49 AM
  #1  
maillemaker
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Default Recondition this Ni-Mh battery?

The battery in my Hovo 510 robotic vaccum is not holding a charge anymore for very long.

I thought maybe I could run in through the discharge/charge cycle a few times on my Venom PR2 charger.

Here is a picture of it:

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It measures 16V across the red and black terminals and 2.5 volts across the white and red terminals.

The RC2 does not have a plug that matches this, so I would have to rig something (stick sewing pins in the sockets and use alligator clips?

But, I don't know which terminals to hook up where. Anyone have any idea?

Thanks,
Steve
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Old 04-15-2018, 09:40 AM
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init4fun
 
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Hi Steve ,

Were this a "mission critical" battery , like one for an RC airplane's transmitter or receiver I'd be telling you to trash it before it trashes your plane . But where this is a robotic vacuum ("Roomba" type I assume ?) and the only danger is a crunchy floor , sure I'll share what I'd do ;

Disclaimer , if you , your bot , or the room it's to clean goes up in smoke remember free advice is worth every penny ya paid for it .

Id set up my charger outside , on a cement patio in case of fire (super tiny , almost non existent risk with Ni-Mh) and use the red and black wires disregarding the white . Red to + , Black to - , set your charger to cycle a 2200MAH battery (the stated rating on your battery's packaging) and let the charger have at it . It's my belief that the white is likely just a lower voltage "tap" that takes from one of the cells away from the full voltage ends of the battery . Oh , and as how to physically connect the battery to the charger ? The alligator clips and pins method would work provided you made darned sure to keep them from touching (shorting) , course on many occasions I've cannibalized different plugs to fit just such situations .
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Old 04-15-2018, 11:38 AM
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OK, I've got it hooked up and on a 5-time charge/discharge cycle. We'll see if this wakes it up.

Steve
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Old 04-15-2018, 06:35 PM
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Well, it finished it's 5-cycle charge/discharge, and then I gave it a charge. Now the robot has been running around the room for at least 20 minutes, and before it would not even go 5, so I think she may be back in action! This is great news, as a replacement battery pack is about $70 on Amazon!

Thanks for the help!

Steve
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Old 04-16-2018, 10:55 AM
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tntpooof
 
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ok this is a 12 cell looks like a C size batter 2200mah so build on wont be 70$..might be around $15 .id use a nimh battery of same size and build my own..id even build one outa a LIfe A123 cell 5 cells.Unlikely the wakeup will last b4 ur at 5 mins runs again.
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Old 04-16-2018, 01:12 PM
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Thanks, TNT, I might try building my own.

Steve
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Old 04-16-2018, 02:18 PM
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Welp, you're right, this time it only ran for about 5 minutes again. Could be the base stand charger isn't as good as hooking it up to the Venom charger, too.

These cells seem smaller than C-cell batteries. Any idea what they could be so I can build my own?

Steve
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Old 04-16-2018, 02:27 PM
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The cells are .871" in diameter and 1.66" long

Steve
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Old 04-16-2018, 02:28 PM
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I believe these are "Sub C" batteries, size RR. They are 23mm in diameter and 42.2mm in length, which is about what these are.

STeve
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Old 04-16-2018, 02:43 PM
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I think I need something like this:

https://www.ebay.com/itm/12-pcs-Sub-...oAAOSwNuxXX9AG

or this

https://www.ebay.com/itm/12-pcs-Sub-...YAAOSwc-tY7ed6

Question: These batteries have tabs that appear spot-welded to one another. How is that done? Can I do it with a normal soldering iron and simply solder them down using solder?

Also I believe the white wire goes to a thermal sensor which is glued to the side of one of the batteries in the stack. There is also a white thing, now sticking up, that I don't know what it is. A fuse?

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Old 04-17-2018, 03:08 AM
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The batteries you linked have tabs already on them. Half the job is done for you. A good soldering iron with a good chisel tip will do fine for making you own pack.

I never seen that white piece on anything before. My guess is it's some type of thermal fuse...it gets too hot...battery connection will be disrupted.
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Old 04-17-2018, 12:17 PM
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tntpooof
 
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white rectangle with 2 white wires is a thermal interrupter and yes subC are the size..dont think you really need thermal guard.
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Old 04-17-2018, 12:38 PM
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I have purchased some the 3300 mAh sub-c batteries linked above. I will try my hand at making my own battery pack. It looks pretty easy. I will preserve the thermal sensor and the thermal fuse.

Steve
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Old 04-18-2018, 07:49 AM
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tntpooof
 
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great but what charger you using?..
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Old 04-18-2018, 08:40 AM
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The robot has its own docking station for charging. When it detects it is low on power, it seeks out the docking station and docks with it to recharge.

Steve
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Old 04-23-2018, 11:19 AM
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So my batteries came in and after a little soldering I have my new battery pack. Robot vaccum is back in service!

Thanks for the idea to just build my own battery pack. Waaaay cheaper than buying a replacement.

Steve
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Old 04-24-2018, 10:50 AM
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good going steve .been building my own for 30 years.
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