Can anyone identify this?

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dagoinc66   1 µW

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Can anyone identify this?

Post by dagoinc66 » Nov 30 2019 10:21pm

ImageImage can any one tell me what this is? Originally it had 2 wires coming off it, one has broken off as you can see. It was part of a Ridgid 18v ni-cad battery pack that I am rebuilding with Li-ion batteries instead. I believe it to be a resistor??? It was taped to the side of one of the inner most batteries and wires were attached to 2ndary pins. I've rebuilt the pack but when I put pack on a charger it doesn't begin charging it, I'm thinking that it part of a safety feature so pack doesn't over heat but not sure, any help would be much appreciated.
Thanks
Last edited by dagoinc66 on Dec 01 2019 1:07am, edited 1 time in total.

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fechter   100 GW

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Re: Can anyone identify this?

Post by fechter » Nov 30 2019 11:14pm

Picture didn't come through.

Use the "Attachments" tab below the text box to add a picture file and place it inline.
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Voltron   10 MW

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Re: Can anyone identify this?

Post by Voltron » Dec 01 2019 12:31am

If it was taped to the side, and had two wires, it was almost def a temp sensor. For ni-cad in particular, the battery temp was important for the charging algorithm.

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amberwolf   100 GW

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Re: Can anyone identify this?

Post by amberwolf » Dec 01 2019 12:52am

dagoinc66 wrote:
Nov 30 2019 10:21pm
Originally it had 2 wires coming off it

ni-cad battery pack

that I am rebuilding with Li-ion batteries instead.

It was taped to the side of one of the inner most batteries

I've rebuilt the pack but when I put pack on a charger it doesn't begin charging it,
No pics, but I can still tell you what it is, from the above snippets of your post. It's a thermistor (thermal sensor), used in Ni chemistry packs because they're commonly charged until they reach a certain temperature then shut off, because of the way that chemistry works. Any good Nixx charger requires a connection to that thermistor to read it's temperature, and it it cant' read it it won't charge because it could cause a fire if it did. (if the cells were already hot).

You will want to read up on NiCd and NiMH batteries (there's a bunch of threads to help, just search for NiMH or NiCd or NiXX in the titles), to help you understand what you will need to do to switch a system from Nixx to a Li chemistry. It's not a straightforward cell-swap.

You cannot use the original charger for Nixx to charge Li. The one does not charge the same way that the other needs to be charged.

You'll need to buy a new charger for the Li pack, or modify the old charger by replacing it's guts with a Li charger. "safe" way to do that is with an RC charger with a balancing connector wired out from the cells in your pack.

You probably also want to add a per-cell voltage monitor (like the RC LiPo pack alarms), or even a BMS, so you will know when to stop using the tool. Nixx tools aren't designed with a cutoff, they'll drain a pack dead, whcih is ok for Nixx cells, but will destroy Li cells (and potentially cause a fire when you recharge them afterward).

dagoinc66   1 µW

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Re: Can anyone identify this?

Post by dagoinc66 » Dec 01 2019 1:19am

Thanks for solving my mystery, what you've said makes perfect sense, I was planning to use a standard li-ion ridgid charger. I'm guessing that I'll still need a thermistor, now to find out which one?

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amberwolf   100 GW

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Re: Can anyone identify this?

Post by amberwolf » Dec 01 2019 9:21pm

It's possible the Li charger also uses a thermistor, but not all that likely. More likely is that they have a BMS in their packs that the charger talks to in some fashion, and thus may not charge any DIY versions.

If they do just use a thermistor, you'd have to open up a Li pack of theirs to find out what kind and p/n or type or value it is, and match that, if you want it to serve the same purpose, and oeprate the same way.

It's also likely that the Li packs use different physical keying so they can't be inserted into a Nixx charger, and vice-versa. (they might still be able to run the same tools, if the keying features are only part of the charger slots).

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