NiMh Batteries

[Tim CooperParticipant @timcooper90034]

[Tim CooperParticipant @timcooper90034]

What battery pack would be most suitable for running 380 motors on 7.2 v, as they are available in AA, 2/3A , 4/5 Sub C. In similar capacities. Of course the weights differ.

Tim

[Paul TParticipant @pault84577]

Sub C every time

[Dave MilbournParticipant @davemilbourn48782]

Tim

Many of the smaller sizes won't accept a charge rate above C, so check that if you envisage ever fast-charging the pack. As Paul suggests, Sub-C cells will usually take fast charge rates. That aside, your use of a 380 motor implies a small fast boat so I'd go for something light, all else being equal.

Dave M

[ashley needhamParticipant @ashleyneedham69188]

Tim.Sub C are most `usual` size. The motor does not care what size batteries are fitted, just the voltage. Weight is the thing between battery types.

Ashley

[Tim CooperParticipant @timcooper90034]

Thanks

I guess what I find confusing is AA' s ,Sub C' s Tec having the same capacity but such different sizes and weights.

Tim

[S MParticipant @sm83187]

With any battery it is all about energy density, how quickly you can replace that energy density using charging, and how quickly you can release that energy density without damaging the cells.

In reality most cells cannot absorb their full charge irrespective of rated capacity and a good start is to derate their stated capacity by 25% to give an acurate indication of capacity over its working life, hence a 4ah rated cell should be treated as a 3ah cell.

[Paul TParticipant @pault84577]

Are you sure?

 

Edited By Paul T on 06/09/2018 11:26:58

[Tim CooperParticipant @timcooper90034]

The 380's are in the Italeri S100 I' m building, which is a metre long, so weight is not so critical ( I hope) . I just find it odd that a 2500 mAh pack of AA and Sub C batteries will power the motors for the same length of time.

Tim

[Dave MilbournParticipant @davemilbourn48782]

Tim

Chapter and verse from the folk who sell them **LINK**

Are you fitting one pack for the whole installation or separate packs for each motor? If you plan to use the P94L then one pack for the P94 + outer motors and another for the centre one + ESL would perhaps be best. If you get the very latest P94L it has BEC so you wouldn't require a third pack for the receiver.

DM

[Tim CooperParticipant @timcooper90034]

Dave

I was planning 2 packs for the outer 380's and another pack for the centre brushless motor and esc. I have the 8.4v pack I used for the PT Boat for this.

Tim

[Dave MilbournParticipant @davemilbourn48782]

Tim

P94 will accept only one power source for the two outer motors, so if you use two 7.2v packs then they will need to be wired in parallel before connecting to P94. That will of course, double the effective capacity – irrespective of whose version of by how much you chose to believe! PM me for further details of P94/P94L as/when/if required.

Dave M

[Tim CooperParticipant @timcooper90034]

Thanks Dave will do.

I usually use one of the P103 Parallel power boards when using 2 batteries.

Tim

[Malcolm FraryParticipant @malcolmfrary95515]

The critical point is not how fast batteries charge, but how well they survive discharge into a load. Generally, the larger the physical size of the cell, the more current it can deliver and still be capable of recharging later. When looking for performance, there is always going to be a trade-off between weight, capacity and available current. Then mix in the different qualities between brands. High capacity might deliver the same performance as sub-C types, but "probably" won't do it as often.

[Tim CooperParticipant @timcooper90034]

I found a previous comment on another thread that the 'Converter' had converted the Italeri kit to a weight of 2.7kg.

So far mine weighs 1.7 kg. Allowing for the other bits needed to be fitted I reckon I have about 500 grams for the batteries.

Two sub C 7.12v 2500 Mah would be 710 g or 4/5 sub c 2200 mAh would be 560 g. Other alternative is 7.2v AA 2600 mah as Dave Abbott used. 364 g.

How do I find the Converters album to look at the pictures he posted?

Tim

Edited By Tim Cooper on 14/09/2018 17:14:42

[Dave MilbournParticipant @davemilbourn48782]

Tim

Bite the bullet? **LINK**

Come on in – the water's fine!

Dave M

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