Popular Post Garry Posted January 13, 2007 Popular Post Share Posted January 13, 2007 **March 2010 Thread Update** General First of all, LiPo cells are no more dangerous than any other kind of cell (NiCD, NiMH etc). All cells will fail if mistreated or misused. LiPo packs come in two flavours, hardcased and softcased. Hardcased have a tough plastic box around the pack internals, and they are resistant to most impacts. They are usually more expensive than softcased packs, but they are vastly safer to use. Hardcased will have connectors either sunk into the pack itself, or on wire. Bear this in mind for what car you'll be fitting it into. Hardcased packs can be modified slightly though, to aid fitment. C-Rating is something else to consider. When looking at packs, you'll see a couple of numbers, such as '5000mah 30C'. This is the amount of current the pack can supply under load. You'll need to do a bit of maths to work it out. 3.8 x 30 = 114A 4.8 x 15 = 72A The resulting number is an indicator for how ''punchy'' the pack will feel when driven hard - the higher the number, the better. Do the maths and work out which will be better for you, as a lower capacity/high C pack is better for racing than a high capacity/lower C pack, but will be the other way around for bashing. C-ratings aren't the only thing to look at when buying a pack though. Some people will say ''A 30C pack is all you need''. This statement is very misleading and potentially dangerous. For example, say you have a car with a brushless system which is rated at 120A. That means, you need a pack which will supply 120A when asked. So, you should try a look for a pack which exceeds this requirement. This can be done with a combo of higher capacity/lower C-rating, or lower capacity/higher C-rating. However, don't automatically think that a high-C-rated pack wil always be enough. For example... If someone said you'd need a 30C pack to power the 120A system, it may sound like any 30C pack would do. Is a 1500mMAh is OK because its 30C? It definitely isn't OK. 5000MAh (5.0A) x 20C = 100A 5000MAh (5.0A) x 30C = 150A 4000MAh (4.0A) x 45C = 180A 1500MAh (1.5A) x 30C = 45A As with most stuff, the more you spend, the better the pack. Beware of packs with soft cases, and packs with suspiciously good numbers from the Far East through eBay (a lot are just made-up numbers). If you use a pack that can't supply enough current, then the pack will overheat and fail with spectacular consequences. Charging The method most LiPo chargers use, is the CC/CV method. This means that the user inputs the charge rate, cell count and/or capacity, and the charger will then charge the pack in the following way: - Charge to peak voltage (3.7v per cell) at max charge current (1C normally) - Holds the voltage at 3.7v per cell until the pack is approx 80%, lowering the amperage constantly - ''Fills up'' the remaining capacity while keeping the voltage the same For all packs and applications, charge at the rate of 1C. This means that 100mah = 0.1A. 3600mah = 3.6A 4000mah = 4.0A 5400mah = 5.4A etc. Expect the charging times in the 20 to 75min region. Some packs can be charged at 2C, 3C or even higher, but the overall useable life of the pack is drastically cut (from 500+ cycles to 100ish cycles), and there isn't any performance benefit to charging higher (just decreased charging times), so its not worth it You can balance charge packs too, where each individual cell in the pack is charged on its own. This requires a dedicated balance charger, or a separate balancer. You don't need to balance charge on every charge, but depending on the manufacturer, you should do so every 50 or so charges. Double and triple check all charger settings (cell type, capacity and voltage) before starting the charge. Discharging LiPo cells do not need manually discharging as they don't suffer from the memory effect that NiMH or NiCD's used to. They should never be allowed to drop below 3v per cell. When this happens, there is an irreversible chemical reaction inside the cell itself, the the cell expands. The cell will now be fit for the bin. For general driving/bashing, you should use a Low Voltage Cutoff (if your ESC doesn't have one built in). This is a device that is wired inline with the ESC and receiver, and alerts you to when you approach the 3v threshold (by LED or buzzer). If you are using LiPo cells for 5 minute races, you don't need an LVC. As the design of LiPo packs have such a flat discharge curve, its easy to see when the pack is low on capacity. If you are driving and the car starts to slow down, then stop immediately, and remove the pack from the car. If you are storing LiPo packs for up to a year, its best idea not to store them fully charged, but neither at 3v/per cell. Just charge them like normal, then have a quick 3-5min drive, then put into storage. When you come to use them again, check the pack voltage on a multimeter before charging. Disposal When a pack comes to the end of its useable life (or the pack fails and puffs up), there is a simple method to make the pack safe for disposal. This is tried and tested but both car and aero LiPo users. - Attach the pack to a low drain across the main terminals (like a fan, lighting kit etc), in an open area. This is to discharge the pack to 0.0v. - Fill a plastic container with tap water, then add salt to it. Lots of salt, around half a cup per gallon. Then, submerge the pack. This is to neutralise the chemicals as much as possible, and to dissolve the aluminium tabs that connect the cells in the pack. - Leave for 7 days to completely discharge, then wrap in newspaper, and throw away in the household rubbish bin. ------------------------------------------------------ Found this online. Its aimed at the Flight guys, but it can all be applied to car use. Use it in addition to the LiPo section in out Electric Guide. Click here. Feb 2008 update - BRCA Guidelines http://www.brca.org/BRCA/elecboard/news/20...r%20Website.htm To dispose of a LiPo, you need to discharge all the cells in a pack to 0.0v using a small load, something like a fan, an LED, a motor etc. Then place it in a salt bath to break the connections inside the pack and remove the last remnants of the energy. I've read about cutting the cells slightly at the edges of each cell, it lets water into the pack, but I don't know the effects of that. 9 2 Quote Link to comment Share on other sites More sharing options...
chris746568462 Posted June 7, 2007 Share Posted June 7, 2007 wow i never knew lipo could explode like that. And i thought that hydrogen RC car was dangerous. kool though Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted February 3, 2008 Share Posted February 3, 2008 Can u use flight LiPo's in RC Cars? I'm guessing u need a flight ESC 2 use them, but would it be possible? 1 Quote Link to comment Share on other sites More sharing options...
Nick Posted February 3, 2008 Share Posted February 3, 2008 There aren't any batteries that are only for a specific model type, they might suit them better but aren't requirements - so no 'special' ESC is needed. Quote Link to comment Share on other sites More sharing options...
Garry Posted February 26, 2008 Author Share Posted February 26, 2008 Just added the BRCA guidelines to the original post, have a good read of them before buying or using a LiPo battery. http://www.brca.org/BRCA/elecboard/news/20...r%20Website.htm Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted June 10, 2008 Share Posted June 10, 2008 Can you use LiPo's with any ESC? If not then is there anything you can do to make them LiPo compatible? Quote Link to comment Share on other sites More sharing options...
Garry Posted June 11, 2008 Author Share Posted June 11, 2008 Yes you can, but if you're going to drive until the pack is flat (like bashing), then you'll need a cutoff that will stop the car when the battery voltage reaches 3v per cell. Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted June 11, 2008 Share Posted June 11, 2008 K, cheers. Anyone know where to get a (cheap) one? Quote Link to comment Share on other sites More sharing options...
joe of loath Posted June 11, 2008 Share Posted June 11, 2008 K, cheers. Anyone know where to get a (cheap) one? if you don't care about hard cases or can make your own, check out the flightpower ones; remember to add about 30% to the capacity of your nimh to get the equivalent lipo. Quote Link to comment Share on other sites More sharing options...
danb1990 Posted June 18, 2008 Share Posted June 18, 2008 (edited) I heard about these blowing up, that's why we don't allow them at Rugby. I was told to Youtube "Lipo fire" and I think it looks pretty cool! Don't know how to embed videos on here so I will just post a link: Now that was done by professionals in a controlled environment some bored European/Russian chaps in a car park, so in order for me to be Politically Correct I must say that you must not try this at home! God I hate political correctness, to be honest if you're stupid enough to do this on purpose in a confined space then you deserve whatever comes your way Edited June 18, 2008 by danb1990 Quote Link to comment Share on other sites More sharing options...
Garry Posted June 18, 2008 Author Share Posted June 18, 2008 LiPo are no more dangerous than a NiMH pack exploding when also deliberately charged at the wrong setting. Quote Link to comment Share on other sites More sharing options...
dclapp Posted June 25, 2008 Share Posted June 25, 2008 hi been out of r/c cars for a while but was quite into a few years ago and now decided 2 get back into it got a old schumacher cat but decided 2 upgrade probabaly the new schumacher cat sx cus was pleased with old one but comes in two battery configuration!! been looking at lipo configuration but don't want to waste all of my current gear what new things do the new lipo require compared to the nimh batteries and any ideas what good equipment would go well in it many thanks look forward to plenty of helpful information Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted June 25, 2008 Share Posted June 25, 2008 All you need is a lipo cut-off regulator thingy unless you get a new lipo-compatible ESC Quote Link to comment Share on other sites More sharing options...
dclapp Posted June 25, 2008 Share Posted June 25, 2008 hi been out of r/c cars for a while but was quite into a few years ago and now decided 2 get back into it got a old schumacher cat but decided 2 upgrade probabaly the new schumacher cat sx cus was pleased with old one but comes in two battery configuration!! been looking at lipo configuration but don't want to waste all of my current gear what new things do the new lipo require compared to the nimh batteries and any ideas what good equipment would go well in it many thanks look forward to plenty of helpful information oh ok u think its worth going to lipo in a car like that got a few motors and novak cyclone speed controller so will probably get a charger cut out device and a comple batterys any specfic ones u can reccommend Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 19, 2008 Share Posted August 19, 2008 never knew there was ever such thing as a lipo cut off well ya learn sumtin everyday does anybody no how much they are and where i could get 1 i would feel alot less worried when driving Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted August 19, 2008 Share Posted August 19, 2008 Novak do some for 2, 3 & 4-cell packs. Clicky 1 Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 19, 2008 Share Posted August 19, 2008 no sadly that wouldnt do i need one for 6 cell lipos Quote Link to comment Share on other sites More sharing options...
Spoonmeister Posted August 19, 2008 Share Posted August 19, 2008 For what? An E-Revo? It'll have one built in. Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 19, 2008 Share Posted August 19, 2008 its in a tt-01 but will be going into a xray t2. i am using a novak GTB speed controller Quote Link to comment Share on other sites More sharing options...
Garry Posted August 19, 2008 Author Share Posted August 19, 2008 6 cell LiPo? How big's the pack? 7.4v LiPo's are just 2 cells. And if you're racing in proper organised 5 min races, you don't need a cutoff as the pack doesn't get discharged that low in just 5 mins. If you're regularly using the majority of the capacity of the pack though, then a cutoff is needed. Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 19, 2008 Share Posted August 19, 2008 wot u mean how bigs the pack? like demessions wise i dunno but it 7.4v i think its the demon power products 3600 pack Quote Link to comment Share on other sites More sharing options...
Garry Posted August 20, 2008 Author Share Posted August 20, 2008 Yeah, all you need is a 2 cell LiPo cutoff. LiPo packs are multiples of 3.7v instead of NiMH/NiCD which is 1.2v per cell. 7.4v is a 2 cell LiPo. 11.1v is a 3 cell LiPo. a 6 cell LiPo would be 22.2v and be absolutely massive in terms of size, it would be a big pack for a plane. Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 20, 2008 Share Posted August 20, 2008 o sorry silly me thanks Quote Link to comment Share on other sites More sharing options...
rc-racer-kirby Posted August 22, 2008 Share Posted August 22, 2008 think im gunna buy one of these as they are cheap. but how do they work? are they hard to install? wb Quote Link to comment Share on other sites More sharing options...
evoboy Posted August 22, 2008 Share Posted August 22, 2008 been running lipos for a bit in my mlst. stupidly left a pack plugged in overnight (but switched off) and my charger refused to recharge the pack ( low voltage)....so it had been sitting for a bit till i was told on another forum that if the pack hasnt 'swelled up' , it is possible to revive the pack by chargeing the lipo on a nimh setting at 0.1a. had nothing to lose ( but maybe my face, nothing much lost there! ) so i gave it a try, charged it till the voltage in the pack came up to around 6.5/7v keeping an eye on it the whole time for any 'swelling' of the cells, then continued to balance charge the pack on a normal lipo setting (1300mah pack i charged it at 0.8a just to be safe), charged up/balanced as normal. yet to try it, but i thought this might be useful info for this thread? Quote Link to comment Share on other sites More sharing options...
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