Trend Airshield Pro DIY Battery Mod!

[MikeJhn]

Old thread I know, but since 2011 Enerloop batteries have been made available and are a much better solution to the NiMh conundrum, together with this thread and this pdf: http://azwoodturners.org/pages/tips/100 ... y_Pack.pdf replacements for the Airshield Pro batteries can be made for a few pounds.

Mike

 

[Ttrees]

Thanks for bumping this thread Mike
Loadsa stuff to learn from it 8)
Tom

 

[MikeJhn]

Ttrees

The problem is, I think the battery connections inside the Airshield pro have changed since the chap made his home made version, so there may be some difficulty in making replacement battery packs for the newer version of the Trend Airshield Pro will have a look at mine when I get a chance.

Mike

 

[MikeJhn]

This is probably the best option now they are available: http://www.ebay.co.uk/itm/112108324112 a single cell will do the work of the previous three and may even fit inside the original casing, still the problem of compatibility with the connections though, may have to take the helmet to bits to get a lead installed.

Mike

 

[Eric The Viking]

I'm not sure that is a solution at all:

The really awkward issue is charge management - it's quite different for lithium-ion compared to NiCd chemistry. The Lithium-ion charging curve (current and voltage management) is complex and needs an IC to control it, and I think access to individual cells, to charge sequentially (one-at-a-time)*. There's also a temperature sensing function too. You can use a sharp temperature rise as a proxy for reaching full charge with NiCd's, but Lithium ion cells get hot during normal charging, so that doesn't work.

And NiCd cells don't usually explode if wrongly charged - Lithium Ion cells can do so.

E.

*You can charge NiCds as batteries, although that will knacker them fast if they're not well matched cells. Cheap chargers do this.

The voltages are almost irrelevant in comparison to the charging problem.

 

[MikeJhn]

Eric

I think you are talking about the Lithium Polymer cells that used to explode or catch fire if charged incorrectly, it can happen if you try to charge multiple cells without the correct balance charger, but I have never had that happen with a single cell, I use multiple A123 nano phosphate Lithium cells in all sorts of applications and have never had a problem with them charging at 500Mah or less, preferably charged at 10% of capacity, unlike the Lithium Polymer cells of old.

Mike

 

[Eric The Viking]

Well this is from the supplier you mentioned above:

Product Description

2* Panasonic lithium ion cells NCR18650B
1x storage box for 2 pcs 18650 LiIon batteries

Safety note: Please note that lithium cells may be used only by authorized personal. Improper handling or short circuit may result in fire or explosion.

Specifications:
Cell Type : Li-ion
Battery type : NCR18650B
Battery Made in Japan
Capacity : 3400 mAh
Voltage : 3.7V
Size: Ø18.5mm x 65 m

Ignoring the bad English translation, they're obviously concerned enough to mention it.

 

[MikeJhn]

Improper use/abuse of any battery will cause a reaction of some kind irrespective of its chemistry, I have purposely overcharged NiMh batteries to demonstrate just that, (inside an ammunition case) the bang is quite impressive and the casing splits wide open, the first time I demonstrated this I expected the positive end cover to push away from the casing, but it seems they will split the case before the positive end fails.

Mike

 

[SVB]

I expected the positive end cover to push away from the casing, but it seems they will split the case before the positive end fails.

Mike

Ah, it all comes flooding back!

http://www.engineersedge.com/material_science/hoop-stress.htm

Happy reading! :wink:

S

 

[MikeJhn]

This looks interesting for a power supply to the Airshield, single battery, so no concerns re balancing: https://www.amazon.co.uk/dp/B01MYX11A6/ ... 8GP0&psc=1

Mike