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MG Midget and Sprite Technical - Battery size - NMC

Firstly, I apologize unreservedly for taking advantage of the vast amount of knowledge held by many on this forum, but I cannot seem to find a definitive answer elsewhere.

Essentially, as well as Spridgets, I have a parallel interest in old motorcycles. As such, I am in the midst of constructing a cafe racer style bike from a 1981 200cc Honda Benly. To create the look, the battery needs to be located under the seat, and as such, needs to be about half the size of the original. As I am a complete ignoramus of most things electrical, then apart from a reduction in the capacity to take and store charge, does anyone foresee any issues here? To assist matters, I have removed the power sapping electric starter motor - it has a kickstart - and I do not foresee any major use of the headlight.
Oggers

Interesting choice of bike!
I would imagine that with modern battery technology would mean that you can get one of much the same power capacity as your original, but in a much more compact size than in 1981.
GuyW

I once had a Benly 125 with a factory race cam - it was always a work in progress and was sold likewise. Looking back I'm amazed the neighbours never complained about that 'youth' who revved up a noisy motorbike most evenings.

The starter motor would have been the largest draw of current, followed by the headlight so a smaller battery should be ok but depending on how efficient the charging system is, after very long runs it might need a trickle charger now and again.
Daniel

If size is everything, then how about a racing battery?
This lithium ion says it's for cafe racer style bikes and fits under the seat?

http://www.ebay.co.uk/itm/CAFE-RACER-BATTERY-LITHIUM-ION-12V-COMPACT-LIGHTWEIGHT-45AMP-START-CURRENT-/252027029274?_trksid=p2385738.m2548.l4275
Jeremy T2

Lots of race bikes and cafe racers use compact lithium batteries. I found this example on a US site:

http://www.dimecitycycles.com/6-amp-hour-120-cca-antigravity-4-cell-battery.html

I saw something like it fairly recently neatly fitted in the seat hump of a very nice Triton. ISTR it had a Japanese voltage regulator because the lithium batts are easy to wreck if the charge voltage is too high, but happily you already have a Japanese reg. BTW lots of older Suzuki owners replaced their regs with Honda units which were reckoned to be super reliable.

On the other hand some use no battery at all, relying on a zener diode. The downside being no headlight or turn signals.

Edit: Crossed in the post with Jeremy!
Greybeard

Great minds etc Greybeard!
Jeremy T2

Chaps

Thanks for the links - very useful. Lithium batteries certainly an option, but appear a tad pricey. My thinking was I may be able to get away something smaller considering the lack of starter motor and running without lights. This is what I was thinking of...

http://www.ebay.co.uk/itm/152201776969?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The added advantage is that you can orientate these gel batteries any way to suit. Charging system appears fine.

The original bike looks pretty ordinary, and combined with a fairly feeble single carb gives ahem modest power. I may change this with twin carbs, and certainly the look will change considerably. Not my ideal choice of bike but it was close, cheap-ish, and keeps me busy. If successful, I may graduate to something more interesting - XS650 or GS750 perhaps.
Oggers

Ogger

Dont ever appologise for taping into the power of the bbs... heck we live for this stuff. Its more of a competition to see who post first with the correct / best answer... its the puzzle that we all enjoy working on

Or maybe thats just me...haha

I would take the bike down to a good fully stocked battery shop. To match up what works best... they will have all differsnt sizes and post configureations

You caj get batt that have post on top, on the sides, post reversed, post positioned forwards or back on top of the bat. Even differsnt kinds of post and then rinse and repeat all the above for differsnt physical sizes of the batt

Id be less concerned about batt funtioning specs and more focased on bow the batt will fit the space and the best route for the battry cables

As you said ... you tossed the starter and wont be using tje head light very often that leqves the poijts and condenser the horn and the turn signals..and none of those will pull much continuse power
1 Paper

You might be able to get away with a 6 volt lawn mower yard tracctor batt. For no more power that your going to need.

P
1 Paper

"You might be able to get away with a 6 volt lawn mower yard tracctor batt. For no more power that your going to need"

Not if it is a 12V system i'm not.....
Oggers

This thread was discussed between 01/04/2017 and 02/04/2017

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