Battery(s) conundrum

[Nasher]

I've been thinking (dangerous at my age) & thought that I could utilise the expertise available on this forum

I have just purchased a roller starter to start my classic race motorbikes. It uses a 12volt 2.5Kw motor for about 10 seconds max to start the bikes. The rollers would not be in constant use, maximum usage to start 2 bikes 4 times every month

I will need a 12v battery for it

At the same time, my van's leisure battery LION 110 LB - 110ah (Size: H: 190mm W: 175mm L: 353mm) is 4 years old, it has been well looked after & appears to work well, but 4 years old.....

So my conundrum is:

Should I simply buy a battery for the roller starter & if so, which one?

Or replace my leisure battery with a new one - I was thinking of Yuasa L36-EFB (Halfords Leisure Battery HLB700 is apparently the same) and use my current leisure battery for the roller starter?
Plus is there a better option than the Yuasa for my leisure battery?

Or just connect the roller starter to the vans battery....?

A bit more background info: Van is a Pug Boxer 2011 with a VSR to charge leisure battery when driving, there is an inbuilt Victron charger for when on hookup, plus I have a small generator which supplies 240v to the Victron charger when at motorcycle events (nobody cares about generator noise at these events!) The Cab battery is the bigger of the 2 that can be fitted. The van also has a Battery Master fitted. No Solar

If the roller starter fails, due to lack of battery, it just means I have to bump start the bike - so not mission critical, just convenient

All comments including funny ones are welcome - but please don't turn this into a(nother) anti generator thread!

Thank you in advance for your helpful comments

 

[funflair]

If you are looking for an excuse to replace your habitation battery this looks like a good one, I don't think LION are the most expensive battery in the world so at 4 years you might have had your moneys worth.

And just to avoid confusion LION not Li-ion.

Martin

 

[pappajohn]

For one 10 second burst the motor will pull 0.6amps.....really doesn't warrant the cost of a new battery just for that.

 

[Vipar]

When I used to race go-karts 2 stroke 210 Villiers. I had 2 sections of rolling conveyer rollers. I jacked the van up put the rollers under the rear wheel (remember rear wheel drive?). Started the van put the kart on the rollers got the wife to put the Transit in 1st gear put kart onto rollers put Kart into 2nd gear and bingo. Hope this helps. Can’t use it on my petrol chainsaw which had a pull cord. Gave it away gonna buy an electric one in the autumn. As arthritis means have no power in muscles.

 

[autorouter]

2.5kW (just over 200 amps) for 10 seconds is a classic starter battery scenario. Anything that does that job well will not be purpose-designed for a leisure battery. I'm not sure the LION Leisure Battery is up to this - it depends on whether is has a Cold Cranking Amps (CCA) spec. Some Leisure batteries, especially Gels, are not suitable. The one you're thinking of as an alternative, an EFB type, is 'dual purpose' starter and leisure battery, so I think it would be OK.

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[peterc10]

For one 10 second burst the motor will pull 0.6amps.....really doesn't warrant the cost of a new battery just for that.

A 2.5kw motor will pull 200 amps at just over 12v. If it is on for only 10 seconds it will use 0.35 Ah each time it is used. So need heavy duty cables, and hope the battery will be good enough to sustain that short term load, but it will not take much out of the battery if it does. .

Edit beaten to it

 

[pappajohn]

Nah, still 0.6amps

2500 ÷ 12 =208.33333333333 amps
÷ 3600 seconds (1hr) = 0.057703703703 amps /sec
× 10 seconds = 0.5787037037036 amps @ nominal 12v

Near enough 0.6a but for such small numbers it's not worth bothering about.

 

[autorouter]

I agree with all the numbers, but it's 208 amps for 10 seconds, which is 0.6 amp-hours.

 

[peterc10]

Nah, still 0.6amps

2500 ÷ 12 =208.33333333333 amps
÷ 3600 seconds (1hr) = 0.057703703703 amps /sec
× 10 seconds = 0.5787037037036 amps @ nominal 12v

Near enough 0.6a but for such small numbers it's not worth bothering about.

You are confusing the rate of flow of electricity (amps) with the total amount used (amp hours). Important to know the difference, because it is the rate of flow that dictates the size of the cable needed.

 

[ctc]

Nah, still 0.6amps

2500 ÷ 12 =208.33333333333 amps
÷ 3600 seconds (1hr) = 0.057703703703 amps /sec
× 10 seconds = 0.5787037037036 amps @ nominal 12v

Near enough 0.6a but for such small numbers it's not worth bothering about.

If you had used 15 decimal places you would have a more accurate result.

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[pappajohn]

OK, got it wrong but no matter whether it's 0.35 or 0.6 it's going to have little effect on the battery and certainly doesn't warrant a new one.

 

[pappajohn]

If you had used 15 decimal places you would have a more accurate result.

Calculator at its max.

 

[peterc10]

OK, got it wrong but no matter whether it's 0.35 or 0.6 it's going to have little effect on the battery and certainly doesn't warrant a new one.

Calm down calm down..........

But I also got the calculation wrong because it is 0.6 Ah not 0.35 Ah. The flow is 208 amps which means it needs very thick cables.

 

[pappajohn]

Calm down calm down..........

But I also got the calculation wrong because it is 0.6 Ah not 0.35 Ah. The flow is 208 amps which means it needs very thick cables.

I didn't think there was a mistake in my calculations.
The roller starter comes with pre-installed cables which appear to be 16mmsq, maybe 25mmsq, and presumably a heavy remote triggered relay..
For a 10 second burst they are quite adequate.