Standard HL 7.2V Battery Pack

[daviddunlop]

A curiosity question.

The two such battery packs I have are working just fine, but I wonder what is inside them...four small cells or two long ones or...

Has anyone disassembled a dead 7.2V battery pack to see what makes it tick? Part of this curiosity is just to learn what it's all about, but a part of me also wonders if a smaller 7.2 V pack could be made up, with similar endurance, to free up more internal space in our tanks. After all, the more space you have, the more gizmos you can stuff into it!


David

[BREL]

there are 6 cells in a 7.2v pack,

[wibblywobbly]

It's not so much the size of the battery, its the amp/hour rating. The HL 2000 batteries are quite low quality, though they do the job as HL tanks aren't heavy on juice.

Batteries are rated by how long they will sustain an average spread of power. Some start off giving out a high voltage and then drop off rapidly, the more expensive ones will output a constant voltage for a longer period of time, and then drop below the minimum that is required.

In the RC Racing world, it is the latter that is required. Eg For the duration of a race the car/buggy needs a consistent high voltage.

If a cell fails it is feasible to swap one out, but it would have to be one of the same rating. It would also be possible to split the pack up and install the cells around the tank hull in convenient locations, but charging off the tank might create a problem?

Some companies build custom battery packs, though these are usually the Lithium Polymer ones that are used in Rock Crawlers etc, and aren't suitable for tanks. The old NiCad packs are now replaced by NiMh (Nickel Metal Hydride?) which are less polluting when they are discarded.

What many people don't realise is that virtually all aa,aaa and 9v batteries etc are actually tubes of watch battery cells. Cells are added or removed depending on the voltage that is required. Take one apart and you will see what I mean.

Thats the trivia lesson over for today! ; )

Rob G

[daviddunlop]

Thank you, gentlemen, for your comments.

They say curiosity can electrocute the cat, so I put this on the back burner for a while, along with the Tiger I project. Now having opened up the Tiger for a major rework, I was reminded once more of just how much space the HL power pack actually takes up inside the hull.

What got me thinking about a smaller battery, apart from the idea of more space in my Tiger I, was a reference on a website to a Lithium Ion battery that I think is made by LG. The part number was ICR18650 A2, and the available specs for it were:

3.6V
2,350mAh
Weight 46.5 grams
Length: 65.1mm
Diameter: 18.4 mm

Two of these should be capable of replacing the standard HL battery pack, in less than half the space. I now need to try and find more detailed spec. and prices to see if it would really work. If anyone has run across these cells in a local shop, please let me know.

Best regards,


David

[Joat]

If your only gonna run 2 cells in series 2s, you may want to look at higher mah cells like these
http://cgi.ebay.com/Sony-Li-ion-Lithium ... 3a53219312
But I would suggest running at leaset 2s2p, so 4 cells total , with would give you 5200mah capacity and you should beable to safely draw 10.4 amps and then some, these would come out slightly smaller then a standard nicad or nimh 7.2 sub c pack, but might be slightly larger then a henglong 7.2v pack, I am currently gonna run a 2s6p pack from my old dell laptop, also beaware that the cells when fully charged and rested will comeout about the 7.2v, mine rested are at 8.1v no load, and that goes for either my 2s2p 3000mah or my 2s6p 6450mah pack.
Also you will need a dedicated lipo/li ion charger.

[daviddunlop]

I was wondering about a possible upgrade of the charger I am currently using with my NiCads, but I am not that sure where to draw the line in terms of "enough or too much" current.

The two original 1,700 mAh NiCads that came with the Tiger I several years ago are still performing well and giving me more than enough play time. All electrical gear is still original HL at this point, but it will eventually be pushing HL metal gear boxes and metal track, and at some point when the Money Fairies smile favorably upon my balding head, I hope to upgrade to eMod electronics on board. So for now, could I not get away with 2,300 odd mAh's?

David

[Joat]

It really depends on your current draw, I have a ss tiger and could not use the stock battery for beans, it would barely operate the tank, then with smoke on the batt would just dump. i would take a current reading and see where you at with your max amp draw.

[Crispy]

Has anyone tried running the 7.2v tanks on 6v or even less? Would this be a feesible way of reducing the speed of a standard tank? Reason i ask is I've played airsoft for years and my guns mostly use 8.4v & 9.6v batts. But I built my own Vietnam era CAR15 a few years back and it didnt have room to fit an 8.4v battery inside. I'd assumed the 7.2v r/c batts i had lying around wouldnt be powerful enough to run the gun or would drain very quickly but it turned out that it worked fine and fitted inside perfectly. Admittedly it was a 3300mah 7.2v batt so the large capacity probably helps.

Anyone tried running different voltage batteries?