nihm or lipo

[Boothy]

Just charging on the mains here, what's a psu?

Do they do mains chargers?

[lentner3]

PSU means power supply unit which gives your charger a 12 d.c. Supply. Some chargers have them built in some are seperate. Like this

http://www.rcpitstop.co.uk/fusion-100w-8-amp-138v-power-supply-o-fs-ps100-4415-p.asp

a good investment whichever batteries you are using.

[InsaneJim69]

Haha. I wasnt on about yourself mate just on all other forums its the be all and end all for some. Lol. Like i say i will no doubt go to lipo when decent nimh cells start getting harder to source and too expensive. But i do still enjpy sitting down and stripping a pack down for rebuilding = lots of fun.

James

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[Boothy]

So as my esc's have tamiya connectors do u just use a deans to tamiya converter? I would not really fancy chopping things about as I would still need to run my nimh battery's.

[InsaneJim69]

Preferably dont run tamiya connectors. Cut and solder some deans connectors for best results and to allow full power to reach the motor. Applying an adaptor will make no difference as the tamiya connector is still the issue. They are ok running low power motors. Its when you get to brushless systems that the connectors really need to go for best results.

James

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[Boothy]

So are you better running deans on nimh too? I have one ezrun but that came with a tamiya connector and I also have a couple of super stock motors.

Also what is the little lead for on the lipo packs?

The Overlander Sport Track 3250 25C 7.4V 2S LiPo Battery - 3250mAh on eBay look like they would fit and are sub £25... That's nearly half the cost of my last nimh...

[InsaneJim69]

Yes, thats where people think thats nimhs cannot supply the same power as a lipo. But if stripped and rebuilt for best current transfer they are every bit as powerful as a 2s lipo. This is where lipo is good as its just plugin and full power can be transfered to the esc without issue.

If you just use a nimh stick pack as is even with deans connectors, they are still holding back alot of power due to the rubbish connections between the cells. I tested my 5.5r brushless system with a standard stick pack and deans connectors and it was barely as quick as a 19turn brushed add to that the batterypack was getting hot. Strip down and rebuild the pack with deans battery bars and connectors and the top speed and acceleration almost doubled instantly and even after a hard 15 min run the battery was luke warm at best.

James

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[SteveU30]

So are you better running deans on nimh too? I have one ezrun but that came with a tamiya connector and I also have a couple of super stock motors.

Also what is the little lead for on the lipo packs?

The Overlander Sport Track 3250 25C 7.4V 2S LiPo Battery - 3250mAh on eBay look like they would fit and are sub £25... That's nearly half the cost of my last nimh...

That battery looks pretty decent and good value, I have an Overlander LiPo charger which can charge and discharge all types of battery and I find it to be excellent, it's not this exact one but it's very similar: http://www.modelsport.co.uk/overlander-rc6-vsp-80watt-7a-output-ac-dc-charger-with-fan/rc-car-products/379060

Other batteries to consider are these from componentshop.co.uk (UK company based in North Wales with excellent service):

http://www.componentshop.co.uk/7-4v-3300mah-30c-hard-case-racing-battery.html - same dimensions as the Overlander pack you linked to but the wires don't exit the pack in the middle like a traditional pack so just bear that in mind (not been an issue for me as yet). Fits nicely in a lot of Tamiyas but the odd minor mod is req'd here and there.

http://www.componentshop.co.uk/7-4v-4200mah-35c-hard-case-racing-battery-fast-charge-at-up-to-5c.html - bit longer again but fits ORV chassis perfectly with only a slight mod to the battery stop (2 minute job). Will also fit TL-01 and Wild Dagger family of chassis but you'll need your Dremel!

And these from Hobbyking (there are lots more at HK but these are excellent value)

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21001 - Incredible value battery and fits DT-02 and Lunchbox chassis nicely. You'll need to swap out the connector as it comes with that odd connector so only good if you are OK with soldering.

The little lead that pokes out of the battery is called the 'balance' lead. The nature of LiPo batteries dictates that to get the proper performance out of them (and to charge them safely) they should be what's called 'balance charged', which means that each battery cell (2 on a 2S, 3 on a 3S, etc...) should be charged equally. The balance lead is plugged into the charger as well as the main battery lead and the charger then intelligently monitors the pack to ensure it is charged perfectly. It is this side of LiPo that I love as it's far more accurate a way to charge a battery than just plugging it in and hoping the charger does what it's meant to do. You still can't leave it unattended but I like the fact that there is a computer managing the charge using an additional level of intelligence than you get with Ni-Cad and Ni-Mh.

I'm trying my best not to preach here as I still have a standard Ni-Mh charger and batteries but since converting to LiPo a fee months back the Ni-Mh stuff sees less and less use.

[danb1974]

Yes, thats where people think thats nimhs cannot supply the same power as a lipo.

Afaik a lipo has 5-20 times the current capability of a nimh.

If you only have cars that do not require powerfull motors, nimh is fine. Though switching a brushed motor from 6-cell to 2S is like wow, I've got turbo.

Once you have say a sct, things change.

[Boothy]

Cheers Steve, plenty to go at there

As my charger is just a basic one I am probably better to get a good charger like the overlander then it's just a case of battery's and at the price of the overlander one it seems to be a no brainer.

Other than a lipo bag I am guessing there is nothing else? My tamiya esc's will be ok?

[SteveU30]

If using TEU-101/104 ESCs you'll want some LiPo alarms which plug into the balance plug on the batteries and monitor the voltage. When it gets too low they make the most almighty racket and warn you to stop driving.

Something like these will do: http://bit.ly/M038Ja

[Boothy]

Cool, this does not seem quite as daunting as I once thought.

[SteveU30]

It's not mate, once you've got the charger and a pack or two you'll wonder why you need did it sooner (I was scared of it too but it's just fear of the unknown).

The best part is that you can leave the batteries in storage for ages and when you come back to them they've hardly lost any charge at all. They simply need a quick top up and they're ready to go!

[SteveU30]

You could do a lot worse than read Garry's guide to LiPo over at MSUK here (section D): http://www.msuk-forum.co.uk/topic/15730-electric-guide/#

[InsaneJim69]

If you only have cars that do not require powerfull motors, nimh is fine. Though switching a brushed motor from 6-cell to 2S is like wow, I've got turbo.

Once you have say a sct, things change.

Same as going from a stick pack nimh to a built pack nimh. its literally like a different world also. I know some people have never experienced a built nimh/nicad pack but the punch and power they provide is quite surprising. The amount of people that I know who used to run a 19turn motor and under with a stick pack and said it wasn't that fast was unreal.

Thats where lipo is easier, there is nothing needed to unleash full power from a system, where as nimh NEED to have a pack stripped and soldered back up with high current connectors.

James

[igbandy]

A few facts from me, who has been using Lipo in cars for quite a few years now.

1/ I have had a Nicd go up on me

2/ I have had A Nimh go up on me

3/ I have never had a Lipo go up on me.

[danb1974]

While I agree a built nimh pack would be better (you can use thick wires between cells), you can't go beyond the chemistry's capabilities

For example look at this comparative graph shamelesly taken from http://www.rcuniverse.com/forum/rc-electric-off-road-trucks-buggies-truggies-more-147/9302976-lipo-vs-nimh-discharge-curves.html#post9302976

nimh drops the voltage from the first moment and is at all times well below the (only 20C rated, nowadays we have in excess of 45C) lipo

And this at a measle 3C rate. Now imagine a brushless 4-pole motor that can take peaks of 100Amps, it has no chance with a nimh which can deliver, what, 30Amps tops?

[beefmuffin]

Don't let this put you off I don't know what you were doing with you copters but something wasn't right with the wiring/battery. For me the performance is why I use them and everything in lofe has an element of risk. With lipo the risk is easily mitigated. I guess you have no amalgum fillings? never eat tuna? Because they all have greater mercury content than you would be exposed to by a broken lightbulb?

Wach to there own. By the way I doubt the pack had too high an C rating it soinds like your battery had shorted out somehow from poor wiring.

hi - well, to answer your questions... no i actually don't eat much tuna (if any) these days, primarily because of the mercury issue. and i certainly don't feed it to my son. i don't think they use metal fillings anymore, do they? our dentist doesn't... it's porcelain or something tooth colored. so it isn't a case of me being ill-informed or hypocritical.

the wires that melted on the heli were definitely the ones that went from the battery to the ESC (the ESC also fried), and again, it's not very useful to suspect that i can't tell the difference. and it was definitely just a case of using a higher C battery. it was the same number of cells, same voltage, but something like 30C instead of 20C. i was always up to that point trying to push the limit on how much battery i could get into the helis to try to get more performance or airtime. i stopped doing so after that scare. you pretty much can't really grasp the danger viscerally until you experience it - i felt a lot more confident playing around with LiPos by trial and error before that incident.

what i really, truly would love for someone to do in one of these threads discussing LiPo vs NiMH ... there is inevitably one or more people who tell of their experiences with exploding NiMH or NiCd batteries in the past, meant either to make LiPo seem like the safer option, or at least no worse. but in pretty much all the cases i've heard of people admit that they were using some rapid charger, jamming charges into the batteries in as little time as possible, intentionally overcharging them, etc. i've never heard of a case of a NiMH or NiCd pack incinerating a buggy after hitting a bump while being driven, etc. it's always during charging and usually charging that's pushing the limits.

so... back to what i would love - i can go on youtube and find video after video of LiPos burning up and exploding. i can find loads of stories of people's houses, garages and 1:1 cars being burned down or incinerated. i can find loads of examples of R/C's catching fire and going up in flames because of some issue with the LiPo. BUT i've never, ever had someone actually find me a video of anything burning or blowing up because of a NiMH or NiCd battery. i believe the stories that they can go *boom*, make a loud sound, etc if you charge them abusively. but that's all. as far as i've ever heard there was no "...and then the house burned down" in any of the stories.

i'd be grateful if someone could dig up some volume of evidence of the dangers of NiMH/Cd batteries so i could at least get a good grasp of exactly what my choice of battery may have in store for me under the wrong circumstances. but if the paucity of documentary evidence of NiMH disaster compared to the plentiful examples of LiPo disaster is any indication on it's face, i think it wouldn't take an insurance adjuster to figure out which one is a greater risk to life and property.

here are a few of LiPo damage/danger:

(the list goes on and on)

and here is one of the only ones of NiMH burning... which they really had to try hard to make burn up (probably overcharge it, short it out, etc - not super likely normal conditions) and even then the fire can only be described as tame compared to any of the LiPo fires... and it looks like they used a pretty serious NiMH as well:

(just copy the URLs as it isn't bringing up the youtube windows or hyperlinks after the first 2)

[igbandy]

Or take up knitting, just make sure that you dont stab yourself.

[beefmuffin]

Or take up knitting, just make sure that you dont stab yourself.

yep - make fun of me! good one. now disprove me. or even just discuss a serious issue like adults. people are reading this and weighing the risks. what are you offering them?

[NWarty]

I should tell the story about how my parent's basement went up in flames a year ago due to a lipo fire. Let me put it this way, the insurance company is going after HobbyKing.

I use them every so often when I have a model that uses them, but keep an incredibly watchful eye when they're charging.

[EDIT] I also had a Nimh detonate on me when I was overseas the first time. Cell failed, ka-boom and scared the crap out of me.

[InsaneJim69]

I gotta admit, living in a 1 bedroom flat in the very centre of Aberdeen and also having a 6 month old son that I literally think the world of, you can imagine I would be ultra protective of him. So safety is my number 1 issue, hence my sort of hesitance towards lipo for now. I know nicads and nimh have their issues, but none have been as bad or had as devastating stories about them than lipo. Now I don't doubt for 1 moment that the % of actual lipo fire is very very low, but still, if I were charging my pack in the kitchen on the granite top I would still have that thought in the back of my head of "what if" ....... I have i that as it is with a nimh pack on charge, never mind a lipo pack (yes I know about charge bags, and they can also fail at times)

Again I am not in any way saying lipo's are bad etc, just that I have that mind set for now especially with my young son in the flat that heaven forbid anything were to happen on charge, it would be a heck of a lot worse with lipo than it would be with nimh.

James

[NWarty]

James, yep, I don't blame you a bit.

My father was incredibly lucky he had a fire extinguisher next to the work bench. He walked away for a couple of minutes to refill his coffee and in that one instant, thing went up like a roman candle. All failsafes on the charger failed (imagine that....) even though he had set everything correctly (ensuing investigation confirmed that he had all the charger settings correct).

[SteveU30]

At this point I think it's worth making people aware that there are what's called 'charging bunkers' available to give you that extra peace of mind. Ironically Hobbyking themselves offer one for not much money but there are plenty of others available too: http://www.hobbyking.com/hobbyking/store/__44552__Turnigy_Lipo_Bunker_Lipoly_Safety_Charge_Box_UK_Warehouse_.html

[InsaneJim69]

At this point I think it's worth making people aware that there are what's called 'charging bunkers' available to give you that extra peace of mind. Ironically Hobbyking themselves offer one for not much money but there are plenty of others available too: http://www.hobbyking.com/hobbyking/store/__44552__Turnigy_Lipo_Bunker_Lipoly_Safety_Charge_Box_UK_Warehouse_.html

TBH even with those, some people will have their opinions and thats that pretty much tbh.

Its just good that most of us can talk away and enjoy a good discussion on a subject.

James