Help fitting NiMH batteries into 1990's Fire Dragon

[rajw78]

Hi all,

I haven't seen this issue raised before (in fact most of the time it is the opposite!) but the new NiMH battery I have just bought for the rebuild of my 1990's Fire Dragon is too short by ~2-3 cm for the holding space and bounces about all over the place. In fact after one too aggressive turn, the battery came flying out and scraped all down the side.

Does anyone have any tips on how I can stop this happening and make it fit the new battery shape?

Any help much appreciated

Rob

[Frog Jumper]

I used stick-on felt furniture pads (they stick on the bottom of your chair legs, etc).  I got a sheet of it, cut it to shape, and stuck that on my batteries...  Fits well, but also gives you some cushion for those hard-landings...

Terry

[taffer]

also a section of foam (adhesive backed) inside battery hole on chassis helps

[rajw78]

11 minutes ago, taffer said:

also a section of foam (adhesive backed) inside battery hole on chassis helps

Thanks for the comments. Just checking that I understand the principal you have both suggested.....................but are you suggesting making the battery wider so it is a more snug fit into the recess? Will this work and wont I have the same problem over time? Is there a way to make the recess shorter? Apologies if I have misunderstood what you have both suggested.

[Frog Jumper]

OK, I erroneous posted last time...

I actually stuck my padding on my chassis (Frog) so they don't eventually wear off the batteries...  So yeah, I "shortened" my battery box instead of making my battery longer with the pads...  It still moves around a little, but it don't flop all over the place like it used to do...  Sticking the pads on one or the other does the same thing - and you'll have to see what works best in your application...  

I'm not sure how the Fire Dragon battery recess works, so this solution may not work if you have 2.5cm (1 inch for us Imperial Folks) to span...  Maybe a piece of styrofoam or wood cut to fit???  

Terry

 

[racer1]

I ran into a similar issue when running thin LiPo packs with mine FD. I used a kids foam pool toy and cut out a piece of it just large enough to fit inside the battery slot.  Once I had that I then hollowed out enough room for the small 2S 3400mah Lipo I was running. 

I can post up some pics later tonight if that helps

[GregM]

Rob, what's the capacity of your NiMH battery? The thing is, with more capacity, the cells within the pack will be slightly larger.
E.g. 3000 mAh NiMH packs should virtually fit any car, while you'll struggle with 4500 mAh packs on some cars like the DT-01 and TT-01E, like I did.

 

EDIT: I just re-read your post and realized that you were talking about the battery being too short. D'oh! Silly me. Sorry!

[rajw78]

Apologies for not replying sooner but been away for a long weekend and haven't been able to take pictures of the issue.  As you can see there is at least a finger's width between the battery and holder (you can also see the damage on the battery when it was flung from the car!)

The battery is an Overlander 3300 NiMH while in a previous incarnation it had been using NiCd which were obviously a lot bigger.

Hope this answers any of the questions above but if not, Ill answer above

 

[rajw78]

On ‎08‎/‎07‎/‎2016 at 6:26 PM, Frog Jumper said:

OK, I erroneous posted last time...

I actually stuck my padding on my chassis (Frog) so they don't eventually wear off the batteries...  So yeah, I "shortened" my battery box instead of making my battery longer with the pads...  It still moves around a little, but it don't flop all over the place like it used to do...  Sticking the pads on one or the other does the same thing - and you'll have to see what works best in your application...  

I'm not sure how the Fire Dragon battery recess works, so this solution may not work if you have 2.5cm (1 inch for us Imperial Folks) to span...  Maybe a piece of styrofoam or wood cut to fit???  

Terry

 

Thanks for the ideas Terry. Racer had some pics so hopefully I can get some tips from him

[rajw78]

On ‎08‎/‎07‎/‎2016 at 7:06 PM, racer1 said:

I ran into a similar issue when running thin LiPo packs with mine FD. I used a kids foam pool toy and cut out a piece of it just large enough to fit inside the battery slot.  Once I had that I then hollowed out enough room for the small 2S 3400mah Lipo I was running. 

I can post up some pics later tonight if that helps

If you could post some pics that would be great. Hopefully you can see the issue from my pic above.

[racer1]

Not sure this is going to work for you as it looks like your issue is the length of the battery where my issue was that the battery was so small that it would fall out of the battery tray and slid under the retainers but here is what I did. 

[rajw78]

2 minutes ago, racer1 said:

Not sure this is going to work for you as it looks like your issue is the length of the battery where my issue was that the battery was so small that it would fall out of the battery tray and slid under the retainers but here is what I did. 

Thanks racer1. Like the idea and I am sure I can get something to fit. Maybe like someone else suggested so wood or stiff plastic which I can cable tie to the chassis? Fingers crossed!

[racer1]

Well you could always just use cable ties to strap it in and leave it there. I have a few cars that i bought dedicated LiPo's for. I have a couple of crawlers that have 2S 7500mah packs strapped in. IN all honestly, I get tired of running my crawler long before the battery runs out. I've gotten 2 hrs of run time and there pack wasn't showing any signs of slowing down. For reference, the small 3300 Mah Lipo I run in my FD lasts about 30 mins with the stock silver can. Same battery in a 380 powered Hopper runs about 45 mins.

[rajw78]

3 hours ago, racer1 said:

Well you could always just use cable ties to strap it in and leave it there. I have a few cars that i bought dedicated LiPo's for. I have a couple of crawlers that have 2S 7500mah packs strapped in. IN all honestly, I get tired of running my crawler long before the battery runs out. I've gotten 2 hrs of run time and there pack wasn't showing any signs of slowing down. For reference, the small 3300 Mah Lipo I run in my FD lasts about 30 mins with the stock silver can. Same battery in a 380 powered Hopper runs about 45 mins.

Nice idea. I think I would still have to put a piece of something in there but at least it would be stuck fast. Does the heat from the NiMH battery affect the chassis or not as long as you have a Delta charger? My FD is only a basher (personal use) so 30 mins is more than enough. Really enjoyed the rebuild though so maybe I can get something a little more refined next time. Thanks for your help

[wolfdogstinkus]

Is that a different holder for the 7cell 8.4Volt battery?, that would explain the gap.

 

 

[racer1]

The LiPo packs I run never get above room temp even during charging as I only charge at 1C or below so no chance of hurting the chassis with those. 

Odds are good that your packs get hotter while running than during charging so it shouldn't be an issue but you can monitor the first couple of times to make sure. 

 

[GregM]

From my experience, NiMH battery packs convert more energy to heat when charging/discharging than LiPo battery packs, on the same level of current source/drain.

Ultimately, it depends on the current your motor drains and how much current your charger provides. If possible, I avoid charging R/C battery packs within their vehicles, and rather put LiPos in fireproof charging bags and let NiMHs get enough air for cooling. But then, I'm also charging with currents of 2A and more.