i find a group 24 in the bow is a nice counter-weight to the crew in the cockpit.  the M15 can easily be made to 'squat' and as a result sail poorly.   the older steel ballast M15s (assuming this is what you have based on the porta-potti sizing issue) allow a group 24 to fix 'like it was made to be there' in front of the steel 'hump' under the forward v-berth hatch.  see pictures of this setup on Scred's www-site (look for the 'interior tour' link).   another option, if you will only use lights and others for a limited time, is to hook up two 6V lantern batteries in series (giving 12V).  have no idea how many amps this would provide ... but would be cheap and very light in weight.     dave scobie M15 #288 - SCRED visit Scred's www-site: http://www.freewebs.com/m15-named-scred --- On Sat, 4/18/09, Lou <capnlou@ec.rr.com> wrote: I also need a battery to run my depth finder and eventually some lights.  I would like to avoid using a big heavy battery.  Does anyone have any experience in this area?     Thanks,  Lou Aliotta