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Initial post: May 24, 2010 12:44:45 PM PDT
Last edited by the author on Jun 22, 2010 1:41:56 PM PDT
alternety says:
I have one of the NST2036 36V Battery string trimmer. It lasted about 4 seconds. But I am exchanging it.

I am curious about the possibility of converting the battery pack to a better technology, but they have a seal on the seam so I can't open it up if I hope to return it. If anyone has a dead battery pack they would send me I can take it apart and see what can be done. If I find a solution I will share. The battery pack does not need to have the batteries in it. I just need the case.

Posted on Jul 22, 2010 6:45:18 AM PDT
It could definitely benefit from lithium-ion, although I'm not sure how much li-ion you could pack into the case to get the weight right for a usable balance wrt the head. Worth a shot though.

In reply to an earlier post on Dec 9, 2011 11:37:24 AM PST
17crewchief says:
I think your idea is a great one and would like to open comm with you. Although I don't have a "dead" battery pack yet (it may be on its way), I certainly like your idea considering that Black and Decker no longer sell the 36 V battery and have nothing to replace it. I fear that by the look of the charging problems, I may have a hulk of a wonderful lawn trimmer with nothing to drive it.
If you are still interested, I will be interested in your reply.
Thank you

In reply to an earlier post on Dec 9, 2011 12:17:48 PM PST
knitter599 says:
I have not done anything yet. I keep looking at Lithium based cells. I have never gotten a dead pack and I am reluctant to destroy my only operating one. I did however look inside.

I have however moved to plan B in my head. Instead of trying to cram a different form factor into the case, use a shoulder pack and run a wire to the dead battery pack. Clip the internal wires to the NiCd cells going to the connector.This lets you use any form factor Li battery you want and keeps the balance of the trimmer. You could also fool around and try to rebalance it with less weight. I have never gotten around to disassembling things enough to measure the current draw of the motor. You need that for picking replacement cells.

The batteries I would prefer to use are LiFePO4. The best ones out there are made by A123 Systems. The project will be pretty expensive. Batteries in the range of $100 to $300. Then you need a charger and probably an equalizer. Although these particular cells are quite rugged and are not nearly as likely to explode in flame if you mishandle them, they are still rather sensitive about some things. Charging any Li chemistry is quite different from previous chemistries. When charging a battery, you must monitor and control the voltage and charge to each of the individual cells. This seems to involve some combination of a bulk power supply capable of supplying both voltage or current limited charging at the appropriate time. Then you need an equalizer that monitors and controls the charging of each cell. You are talking a few hundred bucks for this part.

An alternative is to do the same thing to a couple of NiMh or NiCd packs and just charge one while using the other. Cheaper and less complicated.

When you are finished, particularly with the A123 cells (and of course, cell size), you will have a pack capable of some serious current draw, very fast recharge, and very long useful life. I am sort of thinking that I want an extra weed whacker before I go to the trouble. But I have not seen any at a decent price.

If you go Li, be very careful and educate yourself before buying or using anything. They are easy to damage, and they can literally explode n flames.

In reply to an earlier post on May 8, 2012 9:17:36 AM PDT
Have you found a solution yet?
I received this as a gift and was shocked to find that B&D had quit making batteries already - I need a bit longer time cutting time than my single battery allows (although it is very heavy and gives me a real workout!). When is somebody going to realize a **hip pack** is the way to go for a heavy duty electric?

Posted on May 10, 2012 11:42:16 AM PDT
17crewchief says:
I did find a solution to the defective battery... it was less then a year old, still under warranty, so I called B&D who refereed me to another front-line office who sent me a brand new one in exchange for the old one. It was their latest model and at that time had not been released for purchase. It to is a 36V, but a much smaller and lighter battery and the unit is a good deal need for a shoulder strap. I am totally pleased with it and B&D are back in my good graces.

Posted on May 10, 2012 12:06:10 PM PDT
knitter599 says:
Be careful. Their new 36V trimmer uses a smaller lighter lithium battery. You may not be able to safely to use the existing charger. They are entirely different charging requirements. And Lithium batteries can be quite dangerous (e.g., burn, explode) if the charger is not correct. If they put all the electronics in the battery pack and specifically made it backward compatible, it would be OK. I have no idea if the new lithium even fits the same socket. Let us know how this works out. They should have used Lithium the first time. They did not even use NiMh. Probably because the NiCd can be better at high currents.

Posted on May 10, 2012 2:02:46 PM PDT
17crewchief says:
Thanks for your "heads up" on the newest of B&D string edger. Because of your information, I'm glad B&D'd rep had me send everything back for the exchange including the charger. The charger I now have is the one recommended for the particular battery.

I have charged the Lithium battery 5-6 times since it was new and not had any problems. I do like the unit. Thanks for passing on your concerns.

Posted on May 10, 2012 2:56:05 PM PDT
knitter599 says:
It would appear from your post that the Lithium battery fits in place of the old NiCd in the NST2036 trimmer. Is that correct?

Posted on May 10, 2012 11:02:40 PM PDT
17crewchief says:
Sorry for not being clear...When I found out that batteries for the 2036 were not to be found and B&D stating that they no longer made that battery, I was told to send the 2036 to an office in Oklahoma City, OK and because it was still under warranty, they would replace it with there new 36V trimmer LST136: I really like the unit and the battery seems to last longer than the 2036. It doesn't seem to matter that there is only 1 string instead of 2 that the 2036 had.
Good Day to you.

Posted on May 10, 2012 11:05:39 PM PDT
17crewchief says:
To answer your question more succinctly, no the batteries configuration is totally different from the 2036 to the 136.

Posted on Dec 13, 2012 5:57:43 AM PST
Paul Plasma says:
Wow thanks for all the great info on this weedwacker. I too have been looking for a battery alternative. Mine is not dead yet but I am annoyed how it goes into battery cutout prior to full discharge. My plan for when it dies was to put 3 12v gelcells (like in small UPS) in series. I toyed with the backpack idea but it would have to be heavy gauge twisted pair to not damage the controller. Anyone know if any communication occurs between the battery and the controller?

In reply to an earlier post on Dec 13, 2012 9:28:54 AM PST
I would assume there is comm between the two, since "it goes into battery cutout prior to full discharge".

In reply to an earlier post on Dec 13, 2012 10:08:53 AM PST
Paul Plasma says:
I agree especially because the charger can sense if the battery is too hot to charge. So the big question is will the controller even turn on if you are using the wrong battery and it can't talk to it. I wish there was some sort of hackers forum for this cool widget. Do you think the comm is I2C serial?

Posted on Dec 13, 2012 2:51:59 PM PST
knitter599 says:
If I may make a guess. First of all, I am going to have to do something. On about the 5th charge/discharge cycle on my battery, the charger now refuses to charge it.

Now some thoughts. I don't believe that the trimmer has any discussions with the battery. You can check by opening up the trimmer control unit. I don't really remember, but I think only the power leads are connected to anything. It is unlikely for NiCd that any connection is necessary. The trimmer most likely shuts down by looking at the operating voltage. When it gets low, it cuts off. The charger may use some internal connections in the battery. OK, I got off my butt and went and got my battery. There are only two connections (each with two pins). There may be a temperature sensor inside the charger that just senses the case temp when you put the battery in.

First - battery safety. These things can be dangerous. They generally have low internal impedance (some more than others) which means they are capable of supplying very high currents for a short time. I strongly recommend you not wear jewelry on your hands or wrist while working on batteries or battery powered circuits. They can melt tools (like your soldering iron tip, screwdriver, etc.) or rings on your finger. Even at very low voltages (e.g., a single cell). The rings melting or getting very hot has issues I am sure you can all figure out. The three types with the lowest internal impedance are lead acid, NiCd and many Li varieties. Use your heads when messing with this stuff. Never ever try doing a Li based battery assembly, charging, etc. without fully researching and understanding proper techniques. These can literally be little (relatively) bombs and fire sources. Chargers are, unless otherwise indicated specific to a battery cell type. Use only with the specified type. Otherwise you may, at the least, damage your batteries. Lithium chemistries come in many variants and many are distinctly different charge and discharge voltage and charge detection methods. These are the most dangerous of the battery types. Don't screw with them unless you really understand how they work and their needs. A lithium battery from one manufactures tool should not be charged on another manufacturers Lithium charger. It can cause poor performance at best, explosions and fires at worst.

Regarding replacement cells. The NiCds in the battery are probably connected with short strips of metal spot welded to the cells. Could be wire, and might be soldered. You can probably find replacement cells of the same size and may be able to rebuild the battery. It is quite possible that only one or two cells in the battery are actually bad. Replace them with a matching cell, and the battery can be used. Better practice would be to to replace all cells so they are better matched.

Also note that the different chemistries have different voltages at the cutoff point when you should stop using them and recharge. So the protection in the tool may not protect the different battery. The voltage vs discharge curve is also significantly different. You can make your batteries in the form of several smaller batteries. And then charge them separately but equally. The 3 Lead Acid batteries mentioned by another poster are an example. This simplifies using (i.e, getting) a 36V charger.

My last choice for replacement battery packs would probably be lead acid. They are heavy, can provide very high currents, but their voltage will drop faster that the other chemistries. They are sensitive to being both over and under charged. Permanent damage can result if done even once.
NiCd is potentially the easiest. Even with larger capacity cells, you can probably use the B&D charger for them. Provide high current and relatively stable voltage. Good energy density.
NiMH are a good replacement. You might get away with the NiCd charger, but I would get one specific to NiMH. Not quite as high a discharge current in general but a good choice.

Lithium cells are the best for energy density and some have huge current capabilities. Except for cost, these are my first choice. But I know enough not to hurt myself. The safest tend to be LiFe chemistries and some newer cobalt mix devices. YOU MUST use the correct charger it you play with these.

If you want to contact me directly I am: ha rold five and 2 times niner at g letter system.
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Participants:  6
Total posts:  15
Initial post:  May 24, 2010
Latest post:  Dec 13, 2012

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Black & Decker NST2036 Heavy-Duty 36-Volt Cordless Electric String Trimmer (Discontinued by Manufacturer)
Black & Decker NST2036 Heavy-Duty 36-Volt Cordless Electric String Trimmer (Discontinued by Manufacturer) by Black & Decker
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