Battery

[scousebantam]

I am after a battery for a D7 engine Bantam in the book it says a 6v 9Ah battery, searched ebay with no luck,
any ideas?

[Spaceman]

Just a very quick look suggests a Yuasa B49-6 6V battery might fit. Slightly less Ah's but that won't matter much!

[scousebantam]

Yes saw that one, thanks.

[rhyatt]

These D7 s with the DC charging rely upon the bulk of the battery to perform a rudimentary "regulation " of the charge.

1 of the big square batteries is perfect , from memory 10 AH

Varta B49-6 is 8Ah

[scousebantam]

Thanks rhyatt, thinking along the same lines but being a novice not aware of what you have said and I
agree. If I can't get a 9Ah I would try a 8 or a 10 preferring the 10.
It's the dimension that concerns me, don't know how many dealers I have emailed that don't give dimensions. 

[rhyatt]

I just googled BSA bantam D7 battery and this came up

https://www.google.com/search?q=bsa+bantam+D7+battery&rlz=1C1CHBF_en-GBGB864GB864&sxsrf=AJOqlzV976Z-f3NFYFOSd-tUO6YpkZourg:1674891057354&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi7i4u03-n8AhUGS0EAHTo8BrsQ_AUoAnoECAEQBA&biw=1680&bih=907&dpr=1#imgrc=A9V-E9kl3BV59M

or this one

https://www.google.com/search?q=bsa+bantam+D7+battery&rlz=1C1CHBF_en-GBGB864GB864&sxsrf=AJOqlzV976Z-f3NFYFOSd-tUO6YpkZourg:1674891057354&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi7i4u03-n8AhUGS0EAHTo8BrsQ_AUoAnoECAEQBA&biw=1680&bih=907&dpr=1#imgrc=7gEtNcTgv2C5tM

just ensure that you get the right physical bulk of battery - remember , when these little bikes were made and whizzing around , technology for charging and electrics was very minimal.
there were many articles written at the time about bantam batteries going flat and recommended fixes for various charging issues.

the charging on these is very simple, that single charging coil feeding the little rectifier and that feeding the battery - that is it, my D7 , the other 2 coils feed the headlights.

so get the right size of battery and you'll be fine - just remember that batteries don't get posted with acid in them , so ensure that you are buying a prefilled battery or have access to acid to fill a battery up

very roughly , mine is 3" x 3.5" x 6.25" tall and this is the correct size and fits perfectly - i will do a better measurement later on but these pictures may give dimensions

[rhyatt]

It does pay to get these things right if you can, I have 2 x D7 which have done 2500 miles last year and a D14(converted to 12v) which did 2000 miles, so I use them a lot.
There's lots of knowledge on these little bikes here and tips to keep them healthy .

[scousebantam]

If I have no access to acid filling how does the Gel ones go with bikes?

[Stubaker58]

I run a Bantam with a gel battery (hidden under the seat).
I've adapted the generator to full output sent through a modern regulator/rectifier to the battery and thence to the external coil.  It's all still six volt and contact breaker (but 12v and electronic ignition are also possible).
Fitting the reg/Rec makes the wiring so much simpler as it no longer has to be balanced to load via complicated switching.

[rhyatt]

many bike shops will have "surplus" acid packs , left over from batteries , just ring around your local bike shops, , many bike batteries come sealed with the acid safe inside - again - if you have the spec given here chat to your local chap.

the acid rules changed a while ago , once upon a time the acid pack came in the post , then stupid people started throwing acid at people and the Govt rightly changed the rules on posting acid out - sadly actions of idiots affected sensible people.

your local bike shops can sell acid in boxes with the battery as long as they have the acid licence to distribute it along with the new battery.

ask your local bike shops for the battery that you want , they'll get it in and fill with acid for you to collect after it has stood for a little while to soak into the plates.

as mentioned just above you can change the set up to a slightly tweaked version for the regulation , but if you are staying standard then go down this large square battery route. remember these little bikes were the workhorse of many going to work each day 60 years ago and they were reliable and simple that we enjoy today

[scousebantam]

rhyatt, your last comment is the way to go, thanks.