After I receive my M26 Pershing HL tank, I was tempted to get another battery pack to replace the stock 2000mah Ni-Cd pack since its quality is just OK. From the search of the forum, other people already used 3000, 3600 or even 4000mah Ni-MH pack and have a very satisfactory result. Well, a 3600mah perhaps can run like more than one hour continuously, however, when I come to my situation, I rarely drive my tank for one hour without stop in single run or in single day, instead, I drive my tank mostly 10-15 mins a day or perhaps only drive on weekend only. High capacity may not my immediate need, however, a long shelf life (hold the capacity longer or slow self discharge rate) is what I am looking for, so, I do not have to worry after put the tank aside for few days and come back with the battery running out of juice because of the self discharge of Ni-Cd or Ni-MH.
Then I got lucky and got a good deal on a Li-Po battery one eBay, 7.4V 2050mah costs me $11 shipped, and I also have a spare Li-Po charger from my RC heli.
The battery weights only 1/3 and much small than the stock pack, lighter tanks means longer run time and no need to squeeze the battery into the compartment anymore.
Li-Po battery comes with a separately charge plug, extra soldering/wire for charging on board is not needed. (will do modification later on to put the charge plug near the turret since its small size)
Charging time is 1C, so same as fast Ni-Cd charger but the battery never get hot (not even warm), also can charge at any certain usage point, no worry of fully discharge before charge.
Finally, put it inside the tank and test run, the punch of the power is wonderful, it is max. 12C discharge rate, now I do not worry to put the metal track on. Well, perhaps, the stock pack is just not good enough.
P.S. Since I opened the tank and did the soldering work, after put back everything, the tank had short receiving range problem, the tank only responsed in around 3 feet diameter, extended the antenna help a bit, so it was not the Tx problem, Used mutlimeter to test the wire from the receiver board to the antenna joint, no broken wire, but still no luck. After spending an hour, finally figured out the problem is still this wire, it passed DC current no problem, but not RF signal.
< Message edited by patpatballball8888 -- 8/19/2007 6:37:13 AM >
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Joined: 4/20/2006 From: Launceston, AUSTRALIA Status: offline
The short range thing happened to me from new (HL Tiger 1), i turned the frequency pot (heaps) and it came right. If yours WAS working OK then after mods has lost range, perhaps you've bumped something. Mine is still not as it should be, but yeah, my tank used to drive about 3-6ft then stop dead, and I'd have to put both aerials within 1ft of each other to wake the tank back up then it'd go a further 3-6 feet and do the same. Now in can go perhaps 10-15ft without stopping (out of range...)
If it were working fully as intended I'd be painted, all metal mods and covered Zimmerit by now... but since it plays up I'm not gonna throw heaps of cash at it only to have it fail completely. And when I get another HL it won't be a Tiger
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Joined: 5/7/2004 From: prospect park, NJ, USA Status: online
I would definitly get a lipo cut off unit like the novak one or some others they have out...look into it some may not work with the tank and you may need a reciever...some i think don't and are buzzers that buzz when voltage cut off is reached.... as with our tanks they use so little current and drive so slow it's very hard todetect when the battery is running low.... if you run the lipo batt and run it to low you will run a BIG risk of having a fire start from the lipo pack going up in flames!
Thanks for your concerns, I have to make it clear, the short range problem is solved, the culprit is the antenna wire, replaced it, problem gone. Careful examined the original wire, I found the copper inside kind of oxidized.
This is not my first time to use Li-Po, I fly RC heli too, they use Li-Po as well. If the Li-Po puff up, do not charge and use it again. Over discharge Li-Po will not get fire but will damage the Li-Po and shorten its life.
High discharge rate does not mean the battery will force to "push" such high current to the circuit by itself, it is like a big reservoir and the water flow rate depends on how wide you open the tap (the circuit), so it will not damage the circuit even it draw very little current. Another example like the lead-acid car battery, it has much higher discharge rate, so it can starts your car, truck, SUV but not toast your radio inside your car.
< Message edited by patpatballball8888 -- 8/19/2007 6:14:21 PM >
Posts: 1664
Joined: 5/7/2004 From: prospect park, NJ, USA Status: online
That is not what i mean ....with a tank it's hard to tell when the battery is going dead due to the fact of the slow nature of the tank... so with this in mind you most likely will drain your lipo much lower than you supposed to.
There is a battery alarm (sorry, no sure that is the exact name) for Li-Po, once the battery below 3.2V (drain below that voltage will damage the cell), it will trigger the sound to alert. Also the discharge behavior of Li-Po is similar to Ni-MH, the voltage falls sharply when approaching the empty of the capacity, when push the control stick, the tank will run slowly and the head lamp light dim a lot. I understand Ni-MH has better resistance against over discharge damage and can be regenerated if so, that is the good point of Ni-MH.
< Message edited by patpatballball8888 -- 8/19/2007 7:04:52 PM >
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Joined: 3/27/2007 From: Poultney,
VT, USA Status: offline
Li-poly alarms aren't as great as you might think. I ran a Li-poly in a $1200 airsoft gun, and it had a volt meter and a sound alarm installed. The gun burned.... The volt meter dropped off in less than 2 minutes, and the sound alarm told it was burning....
Thanks OliverLove, It is true many reports on Li-Pobattery cause the fire and explode, particularly happened in the cell phone and laptop computer (even worse, those cell phone battery is charged inside the phone, an enclosed environment). But if a device cause the battery to drop from full charge battery to alarm level in 2 mins, no matter it is Li-Po, Ni-Cd or Ni-MH, it definitely burn the battery and the device since there is something in the device has short circuit.
< Message edited by patpatballball8888 -- 8/20/2007 4:46:12 AM >
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Joined: 1/12/2007 From: Clifton Park, NY, USA Status: offline
I believe that LiPo's are different from the LiON used in cell phones and laptops. Plus cell phone batteries are single cells so you don't have to worry about cell balance which is were most of the problems occur. LiPO's are way too expensive for a laptop so you won't find any there for now. I haven't heard of anyone else using LiPO's in a tank, I guess primarily due to cost but sounds like you got one pretty cheap.
Sorry for the info, the reported battery on fire is mostly on Li-Ion, not Li-Po, however, Li-Po should be less chance in causing fire. According to the statement from Sony Electronics President Stan Glasgow.
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Joined: 3/4/2007 From: Leeds, UNITED KINGDOM Status: offline
Hi all Just wondering If its possable to run a S&S heng long on standard radio gear and mabie a seperate speed controalers to put some mega tourquei motors in? Thanks Jonjoe
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Li-Po (lithum Polymer) battery for HL tank - 
Didn't realize LiPO's had penetrated the handheld consumer market. Thanks for the links. Interesting.