RM-01 Battery Options

[Slyda 183]

I put together one of my re-re RM-01 chassis yesterday and I'm about to start on one of the bodies, but in order to make it a runner I need to come up with a solution to the battery problem. I'm guessing that the 6.6v LF battery that it is designed for is neigh on impossible to get now so has anyone converted one to the 7.2v NiMh set-up? If so what have you done? I have no interest in going brushless/Lipo so please don't bother bombarding me with that option. 

[wolfdogstinkus 1893]

What about using 4cell Ni-mh @ 6volts?

Other than that a small lipo would be perfect, you don't need brushless.

[Juggular 4964]

Have you considered using safer Lithium-Ion?  Unlike LiPo, these won't catch fire.  Each cell is about 3.7v, so two of them can give you 7.4v.  A lot of smaller 1/18 size buggies use these batteries these days.   

These cases are like $2.  The length of the case is about 3 inches (7.7cm).  The width is about 4cm (maybe 4.1cm).  Height is 2cm.  I thought about soldering it with bigger wires, but the plastic case would melt.  I might slide in copper tabs with bigger wires.  

 

[Or you can buy a built one--they have one with Tamiya plug too.  Only 1500mAh though] 

https://www.ebay.com/itm/7-4V-2S-1500mAh-15C-18650-Li-Ion-Battery-T-plug-Burst-30C-RC-model-Vehicle-power/263195994545?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Dbab3937373d648bb9e073898c8dcfe7d%26pid%3D100005%26rk%3D3%26rkt%3D12%26mehot%3Dag%26sd%3D282985591148%26itm%3D263195994545&_trksid=p2047675.c100005.m1851

[Below is 2600mAh, but you have to solder your own plug. No balance lead, but built in cut off protection.]

https://www.ebay.com/itm/Tenergy-Li-Ion-7-4V-2600mAh-Rechargeable-Battery-Pack-w-PCB-2S1P-19-24Wh-5A/391735794800?epid=1900077680&hash=item5b3545dc70:g:x7kAAOSwOgdY0rfG:rk:23:pf:0

 

[Slyda 183]

Some interesting options there Juggular, food for thought. I am currently pursuing the idea of using the normal 7.2v stick as it fits across the chassis (just) with a slight overhang but is well within the bodywork. The only issue I see at the mo is it doesn't fit under the rear shock which can be sorted by making a new taller front shock mount which will give enough clearance for the battery to fit.

[Juls1 1661]

I would avoid using a 7.2v nimh on that car on the basis of the weight alone. If the chassis isn’t built for 6 cell nimh or nicad it’s likely the suspension is going to be too soft for that added weight.  I’m with jug on this one, or a small lipo soft pack. Lipo’s are so cheap and easy to use these days and provide a huge boost in performance (around 20%) just seems crazy to even consider spending money on obsolete technology, and on top of that cutting or modding the chassis to use it.

if you really want to stick to vintage it was designed for 4cell nicads.

Juls

[njmlondon 570]

The 6.6 is actually pretty easy to find. https://www.modelsport.co.uk/index.php?product_id=425236&gclid=Cj0KCQiA_s7fBRDrARIsAGEvF8R-rvFTWFuBAAQCfQQ--OiK_DXyEkO3Y1KyP4mZIHa3ThPMbyiXeQAaAhdIEALw_wcB

I switched out to LIFE a year ago and am a complete convert now. Most good chargers charge them without issues and you just set your ESC to Nimh rather than Lipo and you are off.

Of course, being Tamiya, they are not cheap though!

 

[Juggular 4964]

I am curious as to why LIFE would be better.  (I'm not trying to dispute, I simply don't know enough about LIFE to dispute anything) 

I'm just genuinely (and politely) curious.  On paper, LIFE offers 0.8 volt less than LiPo.  Amp draw is similar.  LIFE is as safe as Li-Ion.  So when njmlondon says 'I'm a convert,' there must be a reason.  

Would LiFe folks enlighten me?  (my middle name is "Cheap RC," but if I know the strengths of LIFE, I might grab one when one is available on sale or something)  

 

[njmlondon 570]

Hi Juggular. I am not saying Life is "better". It is just a better technology for me. I prefer them to Lipo for the following reasons:

1) I have 7 and 10 year old kids who each have a GF01 each and with Life I am able to let them crack on and charge their own batteries. There is no worry about balancing, fires, leaving them unattended etc. 

2) Life do not mind getting wet. My kids love driving through deep puddles and I have just bought one of the big Life batteries for my Mountain Rider for this very reason.

3) they fit all my Tamiyas. The 959 and WR01 have very tight spaces for the standard sized stick pack and my Fighting Buggy and RM01 benefit from the smaller battery as per the OP. 

4) 0.8 volts less than Lipo sounds a lot and I am sure that on a track you would notice, but for bashing with a Black Sport motor and bearings all round, you simply do not miss it. I used to use core RC Lipos and cannot tell the difference.

In conclusion I feel you get Nimh style useability, moron-proof charegeability, perfect size and a lack of fear of water combined with Lipo style punch and length of charge. For instance we can run a GF01 with a Sport Tuned in it for 35-40 minutes pretty much flat out with no drop off.

I really wish Lipo had not beaten Life so conclusively. That extra 0.8 has meant that most people have simply gone for power first and foremost, even though most people do not race. In reality, Life is perfect for the hobbyist and Lipo for the racer, but that fight has been fought and Lipo won across the board.

Another TC member pointed me in the direction of Graupner who do a great range of Life batteries at non-Tamiya prices so worth a look. https://www.graupner.com/Graupner-Online-en/Chargers-Batteries/Batteries-Rechargeable-Batteries/LiFe-Cells/