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Old 09-06-2006, 08:02 PM   #1
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Default NiMh vs. Lipo

If Lipo batteries are aprox. 4000mah and the newer IB and GP cells are also just over 4000mah, what's the benefit of running Lipo technology, besides the batteries being lighter in weight?
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Old 09-06-2006, 08:07 PM   #2
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Quote:
Originally Posted by chicagokenji
If Lipo batteries are aprox. 4000mah and the newer IB and GP cells are also just over 4000mah, what's the benefit of running Lipo technology, besides the batteries being lighter in weight?
The internal resistance of LiPo is drastically lower than NiMH. What that means is that it delivers its power much more efficiently than NiMH. A 4000mah LiPo battery will deliver energy for much longer since a lot less is wasted getting it out of the cells and into your electronics. I don't know the exact ratio, but I believe you can expect almost twice the run time from the LiPo than its equivalent NiMH step-child.
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Old 09-06-2006, 08:11 PM   #3
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And that's just one benefit. The discharge curve is generally better, and maintenance, battery life and weight are much more favorable.

This is the point where people come in here and tell you stories about how LiPo burned down their car, killed the cats and blew up their garage. The cells can be volatile. Don't use them if you're stupid or lazy. Make sure you investigate the topic thoroughly, there are many different manufacturers making LiPo cells, and they're NOT all even.

I would recommend the Orion packs at this point. They seem to be the safest, and the most suited for use in R/C cars. Don't miss their Avionics charger, either. It's tiny, cheap ($80) and will be all the charger you need for LiPo.

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Old 09-06-2006, 08:34 PM   #4
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I've been running the Apogee LiMn (Lithium Manganese) version of the LiPo the last few weeks and have been very happy with them.

They are also less volitile than LiPos - they have video of a LiMn battery pack being drilled through while charging and nothing happens. They have another picture of one being hooked up directly to a car battery. Nothing happened except for the alligator clip leads connected to the car battery desoldering themselves.

Another big benefit is that I can charge the pack at 7.6A so it takes about 20 minutes to peak. Plus, no need to discharge after a run, nor the need to repeak or have it peak as close to when I need to run it.

In general, the main reason why I like LiPo/LiMn is that I can make a change to my car, run some laps, make another change, run my car, and repeat. If I ran NiMh batteries and tried that, the battery pack would probably be flat and I wouldn't know if the change I made was being affected by the flat battery.

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Old 09-06-2006, 11:27 PM   #5
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I've ran a cheap maxamps 4000 Lipo for a meeting and it seems to be alot more consistant than my 3800's but it has slightly less punch and the start of a race. I don't know if this is how Lipo's are or if it just because it's a cheap pack.
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Old 09-06-2006, 11:33 PM   #6
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Quote:
Originally Posted by Drewdc90
I've ran a cheap maxamps 4000 Lipo for a meeting and it seems to be alot more consistant than my 3800's but it has slightly less punch and the start of a race. I don't know if this is how Lipo's are or if it just because it's a cheap pack.
LiPo will have a slightly lower voltage than a peaked NiMH, and may lack some of the punch in the first minute or so. It should be (and stay) faster pretty quick once the peak starts to wear off on the NiMH packs.
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Old 09-06-2006, 11:39 PM   #7
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Great, I thought there may have been something wrong with my pack.
Thanks, Drew.
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Old 09-06-2006, 11:58 PM   #8
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Quote:
Originally Posted by chicagokenji
...what's the benefit of running Lipo technology, besides the batteries being lighter in weight?
i recently went for lipos because of the ff:

1. almost zero maintennance - no need to discharge/tray/rematch/etc.

2. charge it right after running - no need for cooling down because it doesnt heat up during using and charging (although i think it would still be better if you put a fan on it right after running, just to be safe. just my opinion )

3. you only need 1 pack for the whole day (see above)

4. doesnt need a fancy charger - orion avionics makes a nice full featured lipo compatible charger for only $80. i think you can get away with even cheaper chargers but they only charge at a lower amp rate, so it will take a long time to charge.

5. punch/power lasts longer than comparable nimh/nicad batts - havent seen this advantage yet because i only had my lipo for a few days. but ive read that you can charge this days/weeks/months in advance and run it with the same power as a freshly charged one. ive also read that repeated charge/discharge cycles show that it still retains the same punch as the first cycle. for nicad/nimh, you have to use it immediately (or repeak) after chaging to get the full power. also, they cant be used several times per day (the reason why most racers have at least 3 packs for a race day)

6. lastly, lighter weight

the downsides are:

1. expensive but compare this to having 3 nimh packs to race.

2. wont fit some R/C chassis ie. especially saddle pack configs (but i think theyre working on this. maxamps has saddle packs)

3. not yet ROAR legal, or some clubs may not allow this (yet )

4. horror stories of exploding/burning lipos (but i think a large percentage of this is user error or faulty charging equipment )
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Old 09-07-2006, 12:42 AM   #9
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after reading what you said, I am more interested to get a lipo battery even though I just bought 2 nimh batteries!!!

I have also read in another thread that the nimh and nicad are more explosive in nature compared to lipo batts...

Lipo batts, will definietly be the next thing for EP racing, give it one year or so, well, that's just my opinion...
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Old 09-07-2006, 06:17 AM   #10
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alecladanga: answered your PM

i also have 2 nimh batts (novak platinum GP 3700s) that i will use for big races, i think our organizers will only allow lipos in club/weekly races. another big plus for the lipos is you can practice all you want without taking it out of the car. just charge right after running. as soon as your motor/esc cools down, the lipo is ready to go

so just save your newly bought nimhs and use them for big races
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Old 09-07-2006, 06:22 AM   #11
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Quote:
Originally Posted by marvi
3. you only need 1 pack for the whole day (see above)
Well.. It doesn't apply for the bigger part of the world, but smaller clubs where i race usually have 1 hour "gap" between heats of every group... This means if I ran Mod with LiPo's and charged it at 1C rate i'd be forced to have at least 2 LiPo packs.. And 2 chargers (luckilly they're cheaper).
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Old 09-07-2006, 06:57 AM   #12
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Couple things:

1) The Apogee 3800 packs I purchased were $99 each. So, in the end, I feel they are cheaper overall compared to NiMh.

2) Regarding having to purchase 2 LiPo packs to do club racing (especially for mod), it depends. If you get the LiMn packs like I have, you can charge them at 7.6A and they peak off the CC portion at 20 minutes. The CV portion can be skipped -- all that does is add some extra run-time. I have not had any run-time problems running a Novak 4.5 brushless for 5 mins.

I purchased 2 LiMn packs thinking I would not have enough time for regular club racing, but in fact, I just needed 1. I ended up just rotating them out anyways just to keep the number of cycles on each on the same.

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Old 09-07-2006, 07:24 AM   #13
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Quote:
Originally Posted by Lokanas
Well.. It doesn't apply for the bigger part of the world, but smaller clubs where i race usually have 1 hour "gap" between heats of every group... This means if I ran Mod with LiPo's and charged it at 1C rate i'd be forced to have at least 2 LiPo packs.. And 2 chargers (luckilly they're cheaper).
i thought 1 hour was enough to charge lipos to 90%. anyway, i agree that the good thing about lipo chargers is theyre much cheaper and yet still do the job
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Old 09-07-2006, 07:43 AM   #14
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Default Apogee LiMn Batteries

Here is info on the LiMn batteries from Apogee.

http://pfmdistribution.com/secure/sh...d=197&catid=46

Also, they also have a LIFETIME warranty on the batteries - whether you somehow blow them up, abuse them, etc. So, in reality, it is no risk to try them out.

Details here: http://www.pfmdistribution.com/warranty.htm


They are finishing testing a 6000 mAh version.

-Rich
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Old 09-07-2006, 08:03 AM   #15
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Marvi, can you do something about your signature it makes everything you post on annoying to read!!!!
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