Trend Airshield Pro: Build Your Own Battery

I do a lot of woodturning, so eventually it was necessary for me to buy an air supplied shield. After hours of research I decided the Trend Airshield Pro was the best choice for me. It was expensive, but with some more research I found one online for less than $300. It works great. I’m really happy with it.

After about a year the battery refused to hold a charge. No big deal–rechargeable batteries wear out, won’t hold a charge and need to replaced occasionally. I went online to buy a new battery and was shocked at the price. They cost $70. I thought that was crazy. I took the battery out of the helmet and noticed that it was just a plastic container holding a battery pack. The battery pack is marked 3.6 volts, 3600 mah. I took the plastic container apart, which was really easy. It just snaps together. Inside was an unlabeled, shrink wrapped group of three batteries. I scoured the internet looking for a replacement but could find nothing. You can’t buy a 3.6 volt, 3600 mah battery pack. It looks like Trend had this battery specially manufactured just for them, forcing you to pay three times what the battery should cost to keep your AirShield Pro running once the battery wore out. Things like this really piss me off. I have no problem with companies making money, but when they design products that require purchasers to continually pay for that product by forcing their customers to buy overpriced, proprietary consumables, I refuse to play that game. Had I known I would only get a year out of a $70 battery, I could only buy from Trend, I would have bought something else.

I decided to try to make my own battery. Below are photos and step-by-step instructions so you can make one for yourself. It is very easy to do. I am not very handy with electronics, but I have some basic soldering skills and that is about all you will need to make your own battery. Click the photos for a larger view.

Before you begin, take responsibility for your actions. I’m not an electronics expert, and can’t guarantee you won’t hurt or kill yourself. This may be dangerous if you don’t do things correctly. You could fry your helmet fan if you connect the batteries incorrectly. It worked fine for me. Proceed at your own risk.



Here is what the battery looks like after it is removed from the helmet.



Now, carefully pull the two halves of the battery cover apart. The batteries are glued to the bottom cover. The glue is like rubber cement so you can just pull them from the bottom cover.



This is the view of the bottom of the batteries.



Here is the top of the batteries.



Remove the red protective covers. They are just paper glued on to cover the connectors. Cut all the wires from the old batteries at the terminals. Leave the wires connected to the battery cover.



Here are the replacement batteries you will have to buy. I did some research and the best deal I could find was from Order 3 Powerizer-4-3A-NIMH-3800wTa. They cost $4.24 each. With shipping and tax the total was $18.24. If, for some reason, you want to buy batteries at some other place be sure to get 4/3A NiMH batteries, at least 3600 mAh (I got 3800 mAh because that is what Battery Junction had. mAh stands for milliamperes/hour. You may also find it listed as 3.6 Ah, same thing.), flat top with tabs. The tabs make it easier to solder them together. These batteries are 1.2 volts each. Three connected in series creates a 3.6 volt battery pack. These batteries came with a piece of heat shrink tubing on each of the positive terminals. Pull them off.



I used a clamp to hold two batteries together while I soldered the tabs together. The battery on the right has the positive terminal, or the end with the white ring, facing you, and the battery on the left (which will be the center battery) with the negative terminal facing you. I folded the tabs over each other and soldered them together.



I flipped the batteries over so the terminals are opposite of the above photo. I soldered the red wire that is attached to the battery cover to the tab on the positive terminal of the right battery.



If you look in the upper left corner you can see that I soldered the black wire attached to the battery cover to the negative end of the third battery.



With a few dabs of hot glue, I permanently connected the three batteries together. Also notice that I soldered the white thing with two wires to the remaining tabs. I don’t know if this a resistor or what, or if it is even necessary, but I thought it would be a good idea to use it.



If you look carefully you will see that I folded the long tabs closer to the batteries and covered them with hot glue. I figured this would both insulate the wires and stabilize them in case the solder joint failed. Not the neatest job, but this was an experiment and I wasn’t going to get carried away until I’m sure this would work.



Stuffing the batteries back into the battery cover. I didn’t glue the batteries to the cover like the manufacturer did. Once the top cover is snapped on they aren’t going anywhere.



The battery reassembled.



Testing the output with a volt meter. Batteries came charged and ready to go.

I put the battery back in the helmet and the fan worked perfectly. Total time to replace the batteries was about a half hour. Cost was less than $20. Definitely worth the effort. It was also rewarding to get around Trend’s trap of overcharging for their replacement batteries. I’m sure Trend pays only $5 or $10 for these batteries. It’s ridiculous that they sell them $70.

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Rosco Bridenbaker
9 years ago

The “White Thing” is a thermal switch to stop the batteries overheating and control the charge time, the way this if fitted on the refurbished battery pack is likely to cause the pack to catch fire or even explode.
It should be fitted tight up against the batter case so it can read the battery temperature.

This quick fix by someone who knows nothing about electronics is typical of idiots playing with things they do not understand, buy the correct replacement battery.

I just hope is carving is better than his electrical tip’s

Rosco Bridenbaker
9 years ago

It will run longer because it is being overcharged and therefore weakening the lithium battery,
Keep on and it will blow your bloody head off, which may not be a bad thing!

Norman Harrison
Reply to  Rosco Bridenbaker
1 year ago

The batteries used in the Trend and these replacements are nickel metal hydride NOT lithium. If you are going to be critical of what seems to be a viable alternative it would be good to be accurate, constructive and not insulting and aggresive.

Dean ford
9 years ago

tks for the info on the battery pack . just put one together works great,saves a lot of money ………. hope i dont lose my head

9 years ago

Your battery pack is fine. The charger that comes with the Airshield is not the best changer. You can buy a smart charger for less than $20 that will control the charge rate and go to a maintenance charge when primary charge is complete. The smart charger will extend the life of the Trend battery also. Thanks for the info.

Michael Meisman
8 years ago

I performed this procedure about a week ago, before I saw this little ‘how to’ page. First I think John did an pretty good job on this. I say this being an electronics guy. Next I have to say that the comment from Dan Ford is wholly inappropriate and nu-necessary because of the FACT that these are not lithium based batteries. They are NiMH. A nickle based battery.

I bought newer 4500 mAH Sanyo batteries so these have over 1/3 more capacity than the original ones. I am getting a much greater run time than the brand new pack I bought from Trend 2 weeks ago. This is before I have even conditioned the new battery pack. Once I finish doing that my guess is that I will get about 60% longer run times. I base that in the fact that right now I get just under 50% longer times.

I do agree that the Trend charger is vary cheaply made and not near as good as my $300 Hyperion charger. But It does charge these packs to about 97% of absolute peak. That is something that you pay a lot for so it is not a junk charger but it is not a high end one. For what you pay for it it should be better.

Lastly, Rosco is a jerk. One of those whiners that cant get past that his job is not rocket science.

Again thanks John for a job well done. No real dangers here.

Howard Shpegel
8 years ago

I just wanted to say thanks for your efforts on this article. I do work with electronics and have made battery packs in the past for my model helicopters. While I might do things a bit differently, I see nothing wrong with your approach and applaud your tenacity. I like the idea of making something just as good if not better and saving money.

I wanted to offer another view of the $70 cost for these battery packs as I work for a electronics manufacturer and get to see what it takes to bring a product to market. When the market you are selling into is not a mass market, then the number of units you will sell will often determine the selling cost. Add in all the costs it takes to keep a company afloat like rent, engineers, and the need to provide discounts along the the entire chain of jobbers and merchants until it gets to you and you start to see why they charge what they do. Typically, the selling price of will be 5 times the actual cost to make the product.

We do owe this company a thanks for making a product that is sorely needed and if they fail to make a profit, then they won’t be around to sell us spare parts or make new units.

Currently, I work full time and taking the time to make a battery pack means less of the already too little time I have to turn wood. The cost of a battery does not seem so high to me now but next year when I retire, I will be making my own batteries and I thank you for your excellent article.

Paul Dyer
7 years ago

I managed to pick up a very cheap Trend Pro-Ari Shield for £30 as the battery was almost flat and wouldn’t recharge. The shop was a cash-converter type shop so they had no inclination to change the battery. But then when i saw how much a new battery + new air filters was going to cost i felt my ‘bargain’ had turned into a much larger investment….until i saw your post and having used it as a confidence boost, i changed the battery pack myself last night for under £12 and got filters for £15. I saved a massive £50! Thanks again!

5 years ago

As has been suggested here, the Trend Airshield Pro is a good tool but the battery is its tragic flaw.

I followed some advice I saw elsewhere on the net and purchased the Tenergy TN456 charger ($58.95 on and two 18650 batteries ($35.50 for two on

Each of these batteries is rated for 3.6V and a similar capacity to the total of the original three batteries from the original unit.

I built a cardboard battery holder that fit inside the original battery case. I used a couple of pieces of copper soldered to the original wires and glued them to the ends of the cardboard holder.

I shut the new battery with its holder into the old battery case and popped it into the airshield.

So far, so good. Shield works fine and , when the first battery runs out of power, I can put in the other battery and recharge the first while I use the second.

Total cost was only a bit less than I would have paid for two old Trend batteries. But I have a fantastic new charger that will charge all kinds of batteries and has a great deal of “intelligence” that will prevent the kind of overcharging issues the old system had. So these new batteries will last longer than the Trend ones.

Bottom line: John, of course, is right. Don’t throw out your old Airsheild Pro, yet. There may still be years of life left in it. You just need to remove the big flaw!

Earnest Nettles
3 years ago

just found this article wish I had found earlier just replaced my second pack I had one battery pack explode in the charger had to get both new did not know there were two different chargers. but will keep this article in case I need to replace a battery pack in future.

B Noone
Reply to  Earnest Nettles
3 years ago

Just found as well while looking for a replacement battery for my Trend. Just old age so I went looking and amazon has “Generic 3.6V 3600mAh Battery Pack” meant for a Sony product at 13.89. I am ordering it and will switch cases. Might even send Trend a heads up or not, Rosco has been watching the house speaker too much, if it works for you then he should bow out.

Reply to  B Noone
3 years ago

Just found this post while trying to figure out the same issue that everyone else is having with their batteries. I’m not an electrician by any means but I think the the product you posted might not work because it’s lithium whereas the original trend battery is nimh. If you do get it to work please do let us know. I spoke to someone a while back and they said you can’t really just swap them out because lithium can be really finicky and needs to charge differently or something like that. You may want to talk to an expert first.

Reply to  DANIEL
1 year ago

I took my battery pack to Batteries Plus and they made up a new pack and put it in for $38.

1 month ago

Well what a lot of discussion! Agreed manufacturers need profit but….. Trend could provide an updated product, much better value for the same investment they made! We all know Li-ion is much cheaper now and in fact Ni-mh is getting harder to find and more expensive. Trend you need to keep your market edge and update your product with meaningful changes. I have updated my own battery to Li-ion that fits in the battery case and have a smart charger to suit, total cost $25 plus a bit of time. Had Trend supplied a similar option even with their mark up I would have gladly bought it. My helmet now runs for 14hrs before a recharge is needed plus, the recharge time is much shorter and being a smarter charger no worries leaving plugged in if you accidentally forget to unplug.