Problem with rechargeable batteries

[rak sa_ngop]

I have a 5 year carpet sweeper powered by rechargeable batteries which need replacing.

The current batteries are a pair of Ni-Cd batteries, 2.4 v 1300 mAh wired in series. The charger is 9v.

I have switched these batteries for 2 Li-ion batteries 3.7 v 3000 mAh wired in parallel.

I have kept the same polarity as before; black wire to case, red wire to post.

I am using the same 9v charger but it seems that the batteries warm up, but do not take the charge. Moreover when I remove the batteries and try to recharge on the normal Li-ion charger the batteries still take no charge i.e. they appear to have been permanently damaged.

This has happened twice now, I originally tried a single Li-ion battery which also looks damaged.

Can anybody suggest the cause before I go out and buy another set of Li-ion batteries? I want my carpet sweeper!

Thanks

[Crossy]

Have you actually verified that the batteries really are the same polarity with a meter, red does not always mean +ve?

2 * 2.4V in series = 4.8V (Ni-Cd cells are 1.2V so your batteries are 2 cells). The correct solution is to replace like with like - 2 * 2.4V Ni-Cd units.

To correctly charge and protect your Li-ion batteries the charger electronics in the device will likely need modifying, it was after all designed to charge Ni-Cd cells which are very robust when it comes to handling overcharge.

You are also running your device with 25% under voltage, DC motors are very voltage sensitive it will run slow, possibly so slow it won't do its job.

[rak sa_ngop]

Thanks for the speedy reply.

Sounds like the best solution is to buy some Ni-Cd replacements. I assume they are still available? All I see these days are Chinese Li-ion batteries.

[RichCor]

On devices with built-in battery charging capabilities, you should only use replacement batteries of the same energy storage technology.

Lead-Acid, Reusable Alkaline, Ni-Cd, NiMH, Li-Ion each have different charging and circuit protection requirements.

Using a charger meant exclusively for another type can lead to disaster (Damage, Fire, Explosion, etc, etc)

With Ni-Cd you should always match the voltage capacity when replacing the storage cells, but it's safe to use replacement Ni-Cd cells with higher mAh ratings (only affects run time and recharge time of the battery).

[Crossy]

Absolutely no problem getting replacement Ni-Cd cells, they may have slightly higher capacity in the same form factor but that shouldn't worry the charger.

Try Amorn.

[rak sa_ngop]

I made a trip to the Baan Mo soi in Chinatown (near Old Siam) and found ni-cd replacement batteries in the Amorn branch there. They were also able to solder the 4 ni-cd batteries together and re-attach the connector clips for a total price of 400 baht. They have 'bench press' type industrial soldering machine so the whole thing took a matter of a few minutes.(not sure if all Amorn branches offer the same service)

Now my carpet sweeper is working like an F-1 racing car!

You live and learn, don't replace one type of re-chargeable battery with another type.

Thanks

[Crossy]

Amorn in Zeer Rangsit can certainly do it too, I've had the batteries for my cordless drill sorted there.

[Daffy D]

Amorn in Zeer Rangsit can certainly do it too, I've had the batteries for my cordless drill sorted there.

That's interesting Crossy.

I've got a Bosch cordless drill where the NiCad batteries have just about had it. I opened up the battery pack to see if I could replace the batteries myself but there's a stack of about 7 batteries crimped together in series/parallel that even if I could source new batteries could only be done with a machine.

A pair of new batteries are quite expensive so would rather not have to spend that much.

Is this the kind of battery Amorn sorted for you, and how much did it cost?

Thanks

[Crossy]

Yup Daffy ^^^, they'll fix that no problem.

Mine was about 500 Baht (cost of the cells plus a small charge to fit) but it's only 7.2V, so work on less than a grand or so per battery.

[Daffy D]

Cheers Crossy

Mine's a Bosch 7.2 so the price should be about the same

Just have to locate a Amron within reasonable striking distance of Saraburi

[Tagaa]

Does anyone know where I can buy sub C NiCad batteries, besides Amorn?

 

The closest Amorn is 2+ hours away & they don't answer the phone number listed on the website and shocking, I know, they don't reply to e-mail.

 

The closest big city to me is Mukdahan.

[bankruatsteve]

28 minutes ago, Tagaa said:

Does anyone know where I can buy sub C NiCad batteries, besides Amorn?

 

The closest Amorn is 2+ hours away & they don't answer the phone number listed on the website and shocking, I know, they don't reply to e-mail.

 

The closest big city to me is Mukdahan.

Have you tried Lazada?

[Tagaa]

Yep...Lazada and Banggood both.......Nothing

[Crossy]

14 hours ago, Tagaa said:

Does anyone know where I can buy sub C NiCad batteries, besides Amorn?

 

The closest Amorn is 2+ hours away & they don't answer the phone number listed on the website and shocking, I know, they don't reply to e-mail.

 

The closest big city to me is Mukdahan.

 

If you don't mind waiting for shipping AliExpress have many.

 

https://www.aliexpress.com/premium/subc-nicd.html

 

[Tagaa]

Thanks...I went to Ali found the batteries I need,  They even have a 15 cell 18v pack already assembled in the configuration that I need.

 

Item + shipping ($5.26 more than the cost of the pack) is equal to 2310 Bt for one pack. I have 2 packs and both are dead, so by the time I add duty & VAT & I can buy a new 18v Mactec drill with 2 new battery packs for less at Global House or Watsadu.

 

I just hate to throw away a perfectly good drill when I can repair this one. That's just how I am wired. So.....

 

....still looking for a local shop, in or around Muk that may have the Sub C cells.

 

Again, Thanks.

[Crossy]

48 minutes ago, kumarpradeep said:

It is better to take up a service for the device. It could really help you.

 

There is a reason this is called the DIY forum.