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3S or 4S LiPo for Electric Starter.


David Davis
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I haven't used my Dynatron starter for a while (I fly electric almost 100%) but when I used it to start either my 30cc Mackay or 26cc Zenoah it worked really well on an ageing 2200 3S LiPo and was infinitely better than lugging a heavy 12v lead acid battery around.  So unless you need a lot more torque for a big engine I would say 3S is adequate.

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Although I'm mainly a four-stroke enthusiast, I have a number of 2200 3S Lipos which I use in a foamy Cessna lookalike trainer to instruct beginners. I have been using them to power my starter motor successfully for at least the last six months but I have not used it on anything begger than a Laser 70.

Edited by David Davis
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I have used both Dynatron and the JE starters for a few years.  The Sullivan has been sidelined and rarely gets used.   Now that I have used both, I realise that the Dynatron turns too fast and can throw itself off the spinner or burn through the paint / plastic in a moment.

 

I have thought of setting about it and converting it to a geared starter using a couple of toothed pulleys but the JE has stood up to everything that I have used it against from  25 size glow to a Zenoah 62.  I use an old 4 cell Lipo with both and have not had any problem with the switch fusing together - which is more than I can say for the Sullivan.

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17 hours ago, Robin Colbourne said:

Having just acquired an old Kavan starter with planetary geared reduction, I wondered if anyone has experience of using one on LiPos? 
The starter is very compact compared to most, and according to what I have read, the switch actually pushes one of the carbon brushes in contact with the armature, so its not a metal to metal switch.
The Kavan starter I bought needs a thorough overhaul before it can be used, but with new ones costing over £, this one seemed worth a punt.  Kavan even offer a large range of spare parts for them.
This is the manufacturer's picture.  Mine looks as though its been kept in a bucket of sea water!

 

Kavan Planetary Geared Starter

I have one of these and it's been no problem at all in the 5 years or so that I've been using it. I have attached a 3s 3300mAh LiPo to it using a piece of wood as a stand-off. It won't quite manage a 50cc petrol, but anything smaller is no problem at all. I even leave it out for visitors to use at our open days.

The long leads have been shortened and the crocodile clips replaced with XT60s.

Edited by Gary Manuel
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1 hour ago, Andy Stephenson said:

I use a 3s 2200mAh pack on a geared starter which will start a Laser 300t. A 4s would probably be OK it's just the motor won't last so long if you push the voltage up beyond it's nominal specification.

I don’t think it matters too much. I use 4 s packs on a cheap Perkins unit, and a geared Kavan type. They are both used hard, get borrowed, and in 7 years, no breakage or switch weld. 

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  • 4 weeks later...

As previously posted my Align starter struggles a bit on my Laser 180 powered models, partly I suspect as they both have small prop hubs as opposed to spinners. So my plan is to upgrade the 3s battery to 4s. The problem though is that it is a neat unit with the internal battery but a 4s won’t fit and it kind of defeats the point by strapping a 4s to the outside. So I bought a 1s 2200ma battery to wire in series as that way I can keep the 3s internally and have just the slim 1s taped to the outside of the starter. 
image.thumb.jpeg.438fd807c6deca459b2e81c2f50afbc8.jpeg
 

I thought it would be simplest to charge the batteries separately to avoid having to add a 4s balance plug and rewire the 3s appropriately. However I am struggling to work out how best to set up a way to wire up some plugs so I can add in the 1s in series. Any advice from electrical wizards would be much appreciated.

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Hi Nick,

 

The Align starter has some built-in electronics that provide a cut-off to prevent over discharging the battery. This will be calibrated for 3s (as is the battery state LED display) and won't work on a 4s. So you'll need to be extra careful not to take too much out of the batteries. Also the electronics might not appreciate having around 15V applied to them instead of the usual 11V or so.

 

If you are still keen to go ahead with this you'll need to make up a lead with a female Deans connector to plug into the starter, the positive side of this will connect to the positive of a male Deans connector for one of your batteries. The negative of this male connector will connect to the positive of a second connector for the second battery, and the negative of this second connector will connect to the negative of the male Deans connector that will plug into the starter.

 

Like this...

 

1615249667_Seriesbatteries.jpg.92f5cdb498a315a7b4d8a0b9df2cce5a.jpg

 

It appears from your photo. that the 1s battery only has a Futaba style (servo) plug fitted and thin wiring. I don't know what the rating of this is but would be wary of using it in this application.

 

I know things are pretty tight inside these starters and doubt that you will get the new lead and connectors inside with the 3s battery. Whatever you do, make sure you insulate any exposed connections well.

 

Brian.

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Might not be what you want to hear, but I'll point it out anyway as it might be beneficial in the end ?

 

Starters have an inherent demand placed upon them which is to supply massive levels of torque from stationary up to a speed where the engine is able to continue to run. the upshot is that the combined resistance of the starter winding and internal resistance of the battery form the limiting factor. This is assuming that battery, starter and connections are kept short and to the minimum.

 

You might find that by using a new lipo or one with a high C rating would improve starting torque as the lipo internal resistance will be lower, battery performs better at very high discharge currents and the applied voltage is higher.

 

Adding more cables and connectors will only reduce available power although increasing the voltage by 33% goes some way to helping unless it cooks the electronics inside the starter.

 

Not forgetting that a 3S2200 at 35C should be good for 77A where as a 2200 at 90C should give 198A or go for a double whammy and use a 3S3300 at say 60C and have 198A available, but cheaper/greater capacity while retaining the cut off functionality of the starter.

 

As Pirelli Tyres used to say "Power is nothing without control" the down side with all that additional torque is that on the smaller engines (if flooded) you stand a good chance bending the con rod/other damage.

 

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39 minutes ago, Chris Walby said:

increasing the voltage by 33% goes some way

 

Power is proportional to square of voltage; so 33% extra gives you around 75% extra power.

 

Brian and Chris are right, the wiring on that 1s looks "problematic" for your application.

 

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3 hours ago, Nick Somerville said:

Ok, so with Nigel’s helpful reply making 3 against, I shall bin the idea and keep the 1s battery has a handy supply to couple with my servo tester. Now if I could just get a bigger capacity battery of the same physical size as the 2200ma 30c I will be happy.

Effectively you can, just buy a 3S2200 that has a higher C rating, I would suggest a Graphine but they are physically larger so HK or 4max. Other manufacturers are available, but worth noting two points, firstly some massively over quote the C rating and other the lipo physical size is different, but with a bit of hunting around I would have though you could fine a 3S lipo to fit with a higher C rating than you currently have.

 

Hope that helps.   

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Considering that the most recent posts in this thread relate to Nick's Align starter, a few points are worth mentioning I think before Nick goes ahead and buys a new LiPo with a higher C rating that may make little or no difference to improving how his starter works (or doesn't work) when attempting to use it on his Laser 180 (which was the point of his original question).

 

1. The Align starter contains electronics between the battery and the motor. This serves several purposes, including low-battery protection as already mentioned, and it also cuts the power to the motor if a stalled (flooded) engine is sensed. If the 180 is causing the latter to take place (due to it requiring a lot of torque to overcome compression) then a battery that is capable of supplying more current might not help at all.

 

2. I think the starter uses a brushed motor, this plus the aforementioned electronics will have the most significant proportion of the resistance in the whole circuit and again a battery capable of giving more current won't help much, unless the existing battery is faulty anyway.

 

3. Align's recommended battery is a 1900-2300 3S 16C or above, with the inbuilt 5.3:1 gearbox this is 'said' to be suited to upto 50cc petrol or 300 glow engines, but not necessarily with only a single cylinder.... or with a lot of compression.

 

If the existing battery in Nick's Align starter is poor (puffed up, imbalanced or high internal resistance) then definitely replace it with a new one of the correct spec. (maximum size 112 x 35 x 24mm). Otherwise it would perhaps be best to keep that starter for use with smaller less arduous engines and get hold of a Sullivan or similar starter and use that on 4S for the Laser. These turn up regularly on BMFA or at swapmeets.

 

Brian.

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