Charging a NiMH battery

[spangle82]

So today I went to a model shop to get some bits for my MTB - deck fittings and also a replacement battery and speed controller to run the old Mabuchi 540.

The owner/expert Id discussed it with yesterday was out but he'd left a suitable speed controller out for me, a Tio Marine 15.

They only had NiMH batteries so I chose an Overlander Tornado 7.2V 5000mAh pack.

Of course when getting it home I thought - ah, charger... My old charger says 'Nicad charger. To charge 1200mA Nicad packs, output 6-7.2 volts 1VA'. Will it charge the new battery?

Thanks all!

[clockworks]

I think the only difference between NiCad and NiMH from a charging perspective is how they are rapid-charged as they approach being full. The peak voltage is slightly different, so the charger needs to slow the charge and stop charging in a different way.

Since you are using a trickle charger, I don't think it will matter. Might take a while though, as from what you've written it will only charge at 140mA. About a day and a half from flat for a 5000mAH pack.

To get the best from the battery, it's worth investing in a better charger at some point. Something like the IMax B6 AC - about £20 from Hobbyking. It will charge just about any type of RC battery.

[spangle82]

Thanks clockworks, I agree its worth investing in a new charger, not least because theres no indication of when its charged, I think it will just keep going.

Is this the one? https://www.ebay.co.uk/itm/iMAX-B6-AC-Lipo-NiMH-Po...

(bottom option with UK plug for £21.59)

[clockworks]

That one will do the job, but they also make a version that doesn't need the AC adaptor - mains lead plugs straight into the charger:

https://www.ebay.co.uk/itm/IMAX-B6AC-LCD-Digital-R...

[spangle82]

Much more sensible - thankyou!

Now I have to do something with the prop shaft as I did a full speed test run for about 15 secs each way; a burning smell appeared and now the shaft is stiff (oops missus) - the top bush seems to have melted The tube is epoxied through the keel so I hope I can change just the middle bit...

[clockworks]

Propshaft with plastic bushes?

[spangle82]

Yep.

I thought afterwards maybe they were only supposed to run in water for cooling...

[clockworks]

I'm new to RC boats (done a lot with cars and planes in the past though), so I've got a lot to learn. I've bought 3 boats so far that other club members have built, and it looks to me that all the propshafts have brass bushes and thrust washers at both ends.

Still, melting a plastic bush with a 540 motor after 30 seconds seems odd. Most Tamiya RC cars come as standard with plastic bearings in the gearboxes and drive shafts, and they don't melt on stock motors.

[spangle82]

Luckily they still make 7" propshafts - I found this one: https://www.ebay.co.uk/itm/7-MODEL-BOAT-PROP-SHAFT...

Wonder if I should go for the oiler option?

[clockworks]

I was wondering about oilers the other day. None of the 3 boats that I've bought have oilers fitted.