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Battery replacement on a Qualcast hedge trimmer.


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We have a Qualcast 18v hedge trimmer, MOE-7ET-410 , which has been very useful . The battery is a special 18v 1.7Ah and no longer holds a charge. It has a red clip which holds it in the tool , and a red thumb operated loop to move the location clip. I have spent some time chasing Qualcast, Ebay, and Amazon. The only battery that looks as if it may fit is for a Black and Decker tool, a Firestorm heavy duty. It has three connections and my original Qualcast has only two. Before I become careless and buy it , I am trying to research the third contact. What would it be used for?  I have also E mailed B&D and will get a reply tomorrow.

If any one has a working battery and a broken motor please let m know.

Thanks Richard & B

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13 hours ago, RogerH said:

Hi Roger,

Thanks for the link which is very helpful but the battery is sold and not available. I am still looking for the correct one. The Back and Decker unit has a third terminal and B & D can not tell me what it is for. My battery looks the same but only has two terminals. What do you think ??

Richard & B

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I think the third terminal is to connect a temperature sensor (in the battery pack) to the charger to tell the charger when to stop charging.

Bob

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Thanks Bob. It looks as if I could take a risk and buy the one that is available. It looks correct in the picture but it may have some other problems. What do you think?

Thanks Richard & B

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It might look the same superficially, but it probably won't physically fit.  Companies have a habit of making subtle differences in the shape and size of the cases otherwise they couldn't sell exclusive spares.   

Another option is to replace the NiMh cells in your existing battery. The cells will be a standard size and cells with tags for soldering are available. 

 

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2 hours ago, RobH said:

It might look the same superficially, but it probably won't physically fit.  Companies have a habit of making subtle differences in the shape and size of the cases otherwise they couldn't sell exclusive spares.   

Another option is to replace the NiMh cells in your existing battery. The cells will be a standard size and cells with tags for soldering are available. 

 

+1.

Pete

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  • 2 weeks later...

Hi Roger,

I can not find a Qualcast battery. Please could you look again and if you are lucky send me a link. I have checked Ebay very day and there is never any Qualcast.

I hope you can be lucky  again.

Thanks Richard

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  • 1 month later...

I have had a good look at Richard's battery & charger, the battery consists of 15 X NiMh cells rated at 1.7AH  On testing the pack I can only get 0.9AH out of it.

Check cell voltage when down to a pack voltage of 15Volts (1 Volt per cell is the voltage at which you should stop discharging)3 of them were well down.

To replace all 15 would be expensive (£5.34 X 15 = £80 :o) I happen to have 3 or 4 in stock, so will try replacing the weaker ones, & test again.

Also the charger is suspect ! The reason there are only 2 contacts is that the charger is "intelligent" that is to say it can tell when the pack is fully charged, & switch it's self off. It does this by charging at a high rate, & waiting for the battery voltage to stop increasing, and to then fall a little bit. (this is what NiCad / NiMh cells do when fully charged) Signs so far are that it may not be charging at a high rate at all.

These are the nearest I could find to the ones fitted, they are 2.2AH capacity.

https://cpc.farnell.com/gp-batteries/gp300sch1a1p/battery-ni-mh-tags-sub-c-1-2v/dp/BT01302

Bob

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I have just replaced the batteries for a strimmer

DESCRIPTION QUANTITY PRICE COST Sub C 2000mAh 1.2V NiCd -  £29.95 Tagged Battery 15 pack for - 18V 

https://www.batteriesplus.co.uk/acatalog/Batteries_Plus_Tagged_Batteries_26.html

Initially they sent only 14 but after a phone call the 15th arrived quickly.

Bit of a challenge soldering them all in the correct polarity but seem to work fine. There was a temperature sensor to connect as well. It helped to sellotape them together to hold them in place during soldering.

Keith

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Usefull. The originals are NiMh, not Nicad so more money, but still cheaper that my findings above, at £37.15, & they are higher capacity at 3AH

No problem with the soldering, but will have to check with Richard on how much he wants to spend. Then there is still the charger to sort out !

No temperature sensor, as the charger shuts off with "delta voltage sensing" (or should do)

Bob

 

https://www.batteriesplus.co.uk/acatalog/Sub-C-3000mAh-NiMH-Tagged-Battery---Pack-of-15-cells-1900.html#SID=613

Edited by Lebro
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1 hour ago, Lebro said:

Usefull. The originals are NiMh, not Nicad so more money, but still cheaper that my findings above, at £37.15, & they are higher capacity at 3AH

No problem with the soldering, but will have to check with Richard on how much he wants to spend. Then there is still the charger to sort out !

No temperature sensor, as the charger shuts off with "delta voltage sensing" (or should do)

Bob

 

https://www.batteriesplus.co.uk/acatalog/Sub-C-3000mAh-NiMH-Tagged-Battery---Pack-of-15-cells-1900.html#SID=613

Hi Bob

Just checked the Bosch battery pack on my trimmer and definitely labelled NiCd. You had me worried for a minute. As you probably know you need to choose correct battery for charger (or vice versa). In the past I have had meltdown with a mismatch between batteries and a charger.

Keith

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You don't really need a fancy charger for NiMh if you are not in a hurry - modern cells have an oxygen catalyst so you can use constant-current charging at C/10 or below,  for a set time.   e.g. For those 3AH batteries, charging at 150mA for 30 hours or more (C/20) would be fine. The current is low enough not to cause a significant temperature rise . Although not optimal, it would do no damage but of course that isn't much use if you need to use the battery fairly quickly.

The problem with putting just a couple of new cells in a series pack is that you end up with unbalanced states of charge.  On discharge in use,  it would be possible for some cells to become fully discharged before others, and suffer reversed polarity which they certainly won't like. 

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8 minutes ago, keith1948 said:

Hi Bob

Just checked the Bosch battery pack on my trimmer and definitely labelled NiCd. You had me worried for a minute. As you probably know you need to choose correct battery for charger (or vice versa). In the past I have had meltdown with a mismatch between batteries and a charger.

Keith

Nimh & Nicad can use the same charging system, traditionaly Nicads could handle higher charge / discharge currents than Nimh, but these days Nimh have pretty much taken over. the advantage being the lack of "memory" (loss of capacity if full capacity is not used regularly)

Bob

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2 minutes ago, RobH said:

You don't really need a fancy charger for NiMh if you are not in a hurry - modern cells have an oxygen catalyst so you can use constant-current charging at C/10 or below,  for a set time.   e.g. For those 3AH batteries, charging at 150mA for 30 hours or more (C/20) would be fine. The current is low enough not to cause a significant temperature rise . Although not optimal, it would do no damage but of course that isn't much use if you need to use the battery fairly quickly.

The problem with putting just a couple of new cells in a series pack is that you end up with unbalanced states of charge.  On discharge in use,  it would be possible for some cells to become fully discharged before others, and suffer reversed polarity which they certainly won't like. 

Agreed. which is why I would prefer to change them all. It's down to cost !

A "Delta voltage sensing" charger can charge at much higher rates for both types.  Th instructions for this pack say full recharge in 3 hours.

original capacity was 1.7 AH, so charging current was 1.7 /3 = approx 0.6 amps

Bob

Edited by Lebro
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36 minutes ago, Lebro said:

Nimh & Nicad can use the same charging system, traditionaly Nicads could handle higher charge / discharge currents than Nimh, but these days Nimh have pretty much taken over. the advantage being the lack of "memory" (loss of capacity if full capacity is not used regularly)

Bob

Hi Bob

Yes the mismatch I had was in the early days of Nimh. I used a high charging NiCd charger and the Nimh batteries overheated. Ever since I have been careful not wishing to set the house on fire. So are the newer Nimh batteries able to take the higher charge or is it best to still use dedicated Nimh chargers?

Keith

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Thanks very much for the advice. We are considering a new hedge trimmer. It looks like a problem with the existing charger anyway. Until I read the reviews we were considering Terratek, but we need a proper service team to help. So goodbye Terratek

Has any member on the forum got a hedge trimmer , with two batteries and a charger. Summeruse only and quality electrics. It must work easily. We have a Hayter ride on mower and it starts easily even after six months of no use. It is not made in the Far East.

Please send some advice. Thanks Bob what would you do ?

Sunny day here is Sussex so I will be under the TR3A fitting new propshaft bolts which should fit this time.

Richard and B

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OK, problem found with the charger. The mains power pack was putting out more AC than DC ! so I opened it up and found:

At some point it had been dropped, & the impact had broken both the connections on the capacitor inside.

20220518_122259.thumb.jpg.664496d1a660b167c242abab966f8ac3.jpg  20220518_122956.thumb.jpg.7551190529275b1233eb4122a97b6902.jpg  20220518_123544.thumb.jpg.648a7c2353040d70bee52e33acf9ca96.jpg  

This is now repaired, & instead of charging at <100mA, It now charges at 0.5 Amp, which is about right for a 3 hour charge.

Unit on test.    I propose fitting new cells at cost of £30 if that is OK ?

Bob

 

Edited by Lebro
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