yet ANOTHER battery question

In my quest for a physically smaller battery on my 71 roadster I've come up with a few AGM units that will work, but the amp hour rating is lower. Whats in it now is a standard lead acid 14 AH one but the AGM unit I'd like to use is only 9AH. To complicate things more, some of my research on the net says that AH ratings can be subjective, as not all manufacturers use the same testing methods. So taking into account Power Arc ignition, which is less voltage sensitive than a Boyer, Sparx 3 phase alternator and lights on riding, will the lesser AH battery be OK? Any problems with overcharging ?
Thanks

On kicker's Battery size only depends on how long you want or need to idle w/o lights or barely roll over idle with hi beam on. Sparx allowed Peel 65 watt hi beam and two 55 watt drive lights 175 watts plus brake light dragging 15 watt, 190 watt, down slope in 3rd to be too bright from reflection of bluff face on LH and fence/tree line on R and keep the LED in & out of green charge with 1.2 ah and be able to step on start next day if I just blipped up good a hand ful of time before shut down. Peels old boyah would only idle about a min w/o lights and about 20 sec with hi beam before 10.v brain dead misfire and silence. So basically most of ya are following the young wife slicing her ham ends off because that's what her mother did. When new husband questioned it and calls the mother he was told their pan was too small for a big ham. Only reason for much over a few ah size is to leave parking lights on over night per English city ordinances and to give some basis for the mythical PR visions of awaking far from home camping then plug into 12 v shaver power port to clean up for breakfast with new girl friend that really likes being on the C'do as much or more as you. I say go with some fudge factor [ie: if not keeping a metering score in brain with all the other distractions] and fit a 4.8 ah and if that ain't enough buy another and wire in and try not to notice the extra mass and less space while enjoying damaging worse operation state of slow idle nil oil surf.

MikeG said:

In my quest for a physically smaller battery on my 71 roadster I've come up with a few AGM units that will work, but the amp hour rating is lower. Whats in it now is a standard lead acid 14 AH one but the AGM unit I'd like to use is only 9AH. To complicate things more, some of my research on the net says that AH ratings can be subjective, as not all manufacturers use the same testing methods. So taking into account Power Arc ignition, which is less voltage sensitive than a Boyer, Sparx 3 phase alternator and lights on riding, will the lesser AH battery be OK? Any problems with overcharging ?
Thanks

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The AH rating of the battery will have nothing to do with overcharging. The voltage is regulated and the battery will only draw what it needs.

You can easily get by with a smaller battery with no electric start. The smaller battery may loose it's reserve a little quicker if you are driving at low RPM with a headlight on. A three phase alternator would help with that. Jim