TOPIC:

Welcome Skenth nice projects If you need advices for your Mantaray, Edou Waterbock and me could help you Same for spares

Apols to hijack this thread, but I'm also returning to R/C after a very, very long time away from it - just spent the last two weekends cleaning up all of my old cars/buggy's and they're running pretty much spot on apart from my ThunderDragon and Vanquish that need some chassis parts to repair bits that have broken over time.

The only real buggy I've got a real issue with is my BigWig, which I've posted about separately, but I wanted to post on here, specifically about the options on battery power these days.

I've got about thirty old Ni-Cd packs which typically are 12-1400 mah (for the genuine Tamiya's) upto about 18-2000 for the non-genuine. I'd already invested in a real nice Turnigy Accucel 6 Charger/Conditioner, with a view to charging and discharging the Ni-Cd's to bring them back to life, and to be honest, it's done a pretty good job for me, with it cycling up Tamiya 1200mah packs back to 1135 mah charge, and the 1850 packs to 1891 mah! All in all, can't grumble at the charging!

However - I still only get 10-15 mins runtime on a buggy!

I've been reading about these Li-Po batteries, and a common theme seems to be that getting a good Li-Po battery will give something in the 40-55 minute runtime region, which seems amazing to me! I'd probably far rather invest in 1x £30 Turnigy battery that will run a buggy for 40 mins+ and apparently only take 60-90 mins to charge, than bugger about with 16+ hours of trickle charge for 15 minutes of performance.

So, is this all true?

From what I can see, I've already got the correct charger for Li-Po charging/conditioning, so all I really need is a good battery and a converter for the Tamiya MSC/ESC connections. I do have some questions though:

1 - People seem to be split on whether you can use a standard 7.4v Li-Po battery with a vintage Tamiya. Logically, I can't see why it would be an issue, as at the end of the day, it's just a power source. My Wiggy, with standard MSC, was intended to be run with the larger 8.4v battery pack to help overcome the larger weight of the Wig, so I can't see how increasing from a 7.2v Ni-Cd, to a 7.4v Li-Po would affect any vintage MSC or even a vintage ESC - is my logic sound?

2 - I've seen that you can buy some "fire bags" which are recommended for the Li-Po batteries to be stored in unless they explode during charging - seriously? Are they really that unstable? Or is this only el cheapo Chinese knock-off's that cannot be trusted? If I go Li-Po, I'll probably only buy a Turnigy branded one, just for the reassurance of a quality battery brand.

3 - Can I really expect 40+ min runtimes on a standard Li-Po battery. Ifso, what sort of capacity can I reasonably expect to give me that long? I can see that they tend to start out at around 3300mah, and go upto around 5800mah for a 2 cell (2S) 7.4v battery - am I on the money there? I'm expecting to have to invest in a 5800 mah 2S 7.4v battery to give me these sorts of runtimes? Would love to hear from any vintage Tamiya runner's that have moved over to and are running Li-Po batteries.

4 - What's with these alarms or cut-off's? Why can't you run a Li-Po to virtually flat as we all ran our Ni-Cd's until the buggy just wouldn't move anymore?!?!

I think that covers all of the holes in my knowledge - the benefits of Li-Po do seem to be great. I figure that I need to buy a few "converters" and stick them on MSC/ESC power plugs of my runners, so that I can just swap one or two new Li-Po batteries between and get 90 mins+ of runtime from a couple of batteries!! That would be awesome....

Anyway - hope my logic is sound. Sure would appreciate any replies that share their experiences or highlight anything I've missed or overlooked in terms of moving over to this battery technology - much obliged!

PS - anyone got any:

1 - A parts for ThunderDragon - specifically A5 where the two front arms mount the side of the gearbox

2 - A parts for the Vanquish = specifically A2 (gearbox casing) where part of suspension mounting has snapped off

3 - Midnight Pumpkin - Shell mounts - all four please?

4 - Blackfoot rear shell mounts - x2

5 - Celica Castrol Rally '93/94 shell in good nick for a runner and also some white five spoke wheels and rally block tyres - all for the same model!

Thanks again!

Running time is going to depend on weight, gearing, how you drive, the running surface etc etc, but assuming all that's equal, then any battery with twice the capacity will run for twice as long.

Why 16 hours trickle charging? You know you can charge nicads faster than that? 1C (i.e. 1 amp per 1000mah battery capacity, e.g. 1800mAh pack x 1C = 1.8 amp charge rate) should be no problem at all, even with old packs. 1.5C again no problem with packs you know are sound, 2C might be pushing it.

I'm suprised one of the members here (eddrick) hasn't been on & explained why nicads are so much better than NiMH


1 - I'm not really aware of anyone saying you shouldn't use Lipo in an old Tamiya, you can always disguise them There is a real problem with Lipo packs fitting though - you need a hard case to protect the cells, but old Tamiyas aren't optimised for new shapes, and Lipo fake "stick packs" tend to be far too big. 2S Lipo (7.4v) delivers a lot more performance than 7.2v Nicads or NiMH, (at least equivalent to 8.4v Nicads/NiMH) not because of higher voltage, but because it's a much faster chemistry. Still not enough to break anything IMO, unless it was very highly stressed or clapped out in the first place.

2 - I'm whizzing into a strong wind in saying this, but Lipo batteries do not explode. They may outgas very rapidly, go pop, bang, or, more usually, spew a huge flame of superheated plasma fire that you'll never put out; it'll only last a few seconds, but can set fire to & destroy whatever you happened to be charging the battery in (shed, car, house) - but they don't explode, only explosives do that Cue someone posting a video of a lipo battery "exploding". Apparently there are fake fireproof bags being made that aren't fireproof ... I think I'd trust a steel box better. If you use a hard cased battery, don't push your luck on charge rates, and dispose of it if it gets damaged (especially swelling) then I don't see why lipo shouldn't be considered safe. Lipo batteries are routinely used in small electronic devices, when did you last hear of someones phone "exploding"?

3 - Again, if you're getting 10 mins on a 1200mAH pack, 4800mAh would theoretically give you 40 mins. Bear in mind that not only do prices go up as capacities increase, but in the case of Lipo batteries, the physical size increases too.

4 - Not a technical answer, but I know if you run a Lipo battery down past a certain voltage, it'll never charge up again. I guess this (and all that "exploding" is the trade off for smaller size, lighter weight & much improved power delivery.
Either get an ESC with Lipo support (cuts off when minimum safe voltage reached), fit an alarm on the "balance" lead on the battery, or stop driving when the edge goes off the speed.

One issue though - there can be heat build up issues with longer running times, the design of some older cars counted on short run times and long rests for adequate cooling

The soft lithium batteries are dangerous because in case of short cut, you just can lose 1 hand the head, your home or just your life...
A test was made by a friend: 1 cellule of 1cm square, in short cut:
1st step: The cellule become 1 rugby ball form
2nd step: chimical explosion wich give the last step:
1 flames launcher with 1 meter long chemical flame during 1 minute.
There are 680 cells like this one in a Renault ZOE Crazy bomb Under the back

Perso, NICD, NIMH sticks are charged Under 1,5X max capacity. They are not Young but enough to have fun. 5 sticks Sanyo RC2000 for 12minutes of fun

Jonny wrote:

Why 16 hours trickle charging? You know you can charge nicads faster than that?

I know! But I've never found that fast-charging Ni-Cd's never gets really good results, and that the performance drops off far quicker than if they'd been trickle charged.

Jonny wrote:

I'm suprised one of the members here (eddrick) hasn't been on & explained why nicads are so much better than NiMH

I would like to know too!

Jonny wrote:

1 - I'm not really aware of anyone saying you shouldn't use Lipo in an old Tamiya, you can always disguise them There is a real problem with Lipo packs fitting though - you need a hard case to protect the cells, but old Tamiyas aren't optimised for new shapes, and Lipo fake "stick packs" tend to be far too big. 2S Lipo (7.4v) delivers a lot more performance than 7.2v Nicads or NiMH, (at least equivalent to 8.4v Nicads/NiMH) not because of higher voltage, but because it's a much faster chemistry. Still not enough to break anything IMO, unless it was very highly stressed or clapped out in the first place.

I don't care what anyone thinks! I'm only interested in doing it for the much improved run-times. My understanding is that I can get packs upto about 5000mah Li-Po that are near enough identical in size to a stock Ni-Cd - they just tend to be a bit squarer in shape rather than the 6 cell Ni-Cd's of old. This fine for most vintage Tamiya, but it's not going to fit in my 959! (bugger!) Would be dead handy to hear from anyone that is running vintage Tamiya on new Li-Po and recommend a specific Li-Po battery that works really well for them with the old kit...

Jonny wrote:

2 - I'm whizzing into a strong wind in saying this, but Lipo batteries do not explode. They may outgas very rapidly, go pop, bang, or, more usually, spew a huge flame of superheated plasma fire that you'll never put out; it'll only last a few seconds, but can set fire to & destroy whatever you happened to be charging the battery in (shed, car, house) - but they don't explode

Ok, now in my world, that sounds like an explosion (or at least a serious event) to me! "Superheated plasma fire that you'll never put out but will set fire to your house" (was that a little joke?) Excuse my ignorance on Li-Po's!

Jonny wrote:

3 - Again, if you're getting 10 mins on a 1200mAH pack, 4800mAh would theoretically give you 40 mins. Bear in mind that not only do prices go up as capacities increase, but in the case of Lipo batteries, the physical size increases too.

Yep - fair enough. Do you use Li-Po's with your vintage Tamiya's?

Jonny wrote:

4 - Not a technical answer, but I know if you run a Lipo battery down past a certain voltage, it'll never charge up again. Either get an ESC with Lipo support (cuts off when minimum safe voltage reached), fit an alarm on the "balance" lead on the battery, or stop driving when the edge goes off the speed.

Ok, this is very useful to know - I don't want to spend £30 on a battery and run it so flat that it will never charge again! I think I'll get one of these cut-off devices that will protect it then. Sounds worthwhile.

Jonny wrote:

One issue though - there can be heat build up issues with longer running times, the design of some older cars counted on short run times and long rests for adequate cooling

Ah, now this seems like a good point that I hadn't thought about before - do you mean the motor / ESC / receiver / battery or all of the above? Any particular models spring to mind which would seem to you particularly in need of shorter running times to cool and recover?

Thanks Jonny - this has been a very useful learning curve for me. Much appreciated.

downtime on longer runtime, motor running hot if forgetting to take a break.

It can be worthwhile 'zapping' your NiCds with a high current on a 'dumb' charger (without delta peak cut off).
Over time, crystals can form that will dissolve with this.
They can cause a temporary voltage peak that a 'smart' charger will see as a signal that the pack is full.
After this treatment, you will most likely notice the modern charger can go to a higher capacity.

oups I use a wizard delta peak charger. delta peak changed my life. Now I can charge a stick Under 5A but it is very fast

I've never gone over 4A - for a 5Ah pack myself...
Mods, maybe move a few posts to the what are you charging thread (if that doesn't mix up things)?

YEP!