Thread: Ultra 2nd Battery Backup
07-04-2007, 03:15 AM #1
Ultra 2nd Battery Backup
I want to install a 2nd battery in my Ultra for offshore. I originally planned to just glue in bracket in right bow within about 12" of main battery. No wired connections, just a backup battery that is securely stored and can be easily retrieved. I am now thinking, however, that a prewired switch to change batterys should not be that dificult. It would be great to hear your views on these questions:
1) Is the prewired battery selector switch relatively easy to do and the best way to go?
2) I like redundant safety systems esp when 25% of my problems over last 3 yrs were electrical. Is the ability to switch batteries good enough or should I incorporate redundant wiring to specific electrical components?
Right now, the only add on equipment that might draw power is the rule bilge. Will be adding depth finder tho.
I am sold on idea of 2nd battery in part because these Yuasas are so small & light, why not?
Thanks for any comments.
07-04-2007, 06:42 AM #2
These Perko battery switches have been around for ever. Widely
used in boats. I've had several.
What I do like is that when you install them their selector switch gives you
1) battery one or battery 2
2) parallel both batteries for extra boost
3) both batteries can be cut off from electrical feed to boat
4) Usually you put a starter battery on position one, a "House" battery on two
that is a deep cycle to run stereo, fridge, etc
Super easy to install. You use reg batter cables and connectors.
By putting two batteries in with this switch would give you a premium
installation. Heck, I might have to do this one myself!
They're made in Miami, can't seem to find corporate website.
Last edited by tomgtv; 07-04-2007 at 06:46 AM.
07-04-2007, 08:39 AM #3
The second battery with a selector switch that tomgtv describes sounds like a great idea. If you can select both batteries in parallel, I think this should not be the normal operating position since it will demand more current from your charging system and the batteries can discharge through eachother if the voltages are different. I would keep one battery normally connected and one isolated as an accessory battery (depthfinder etc.). The nice thing about this is that if you leave your accessories on too long, you could only lose the second battery. You can move the switch to recharge the accessory battery or just recharge it at home before each use. You could also add a waterproof 12V outlet for recharging cell phone, marine radio etc.
07-04-2007, 08:56 AM #4
That's exactly how it works
I can't tell you the amount of times that I had to parallel the batteries
due to discharge after use. Yeah that small charging voltage may
be taxed if you leave them both online. However if they are topped off
via a battery charger when in storage it shouldn't be a problem.
With that second battery you could run your stereo, ipod, whatever without
worrying about starting the ski.
07-04-2007, 09:15 AM #5
Well I am actually right in the middle of doing this so look on my thread soon. The 2nd batt will take place of the 2nd waterbox. It will be isolated. Techjunkie is right on the money. This charging system will not handle too much more than a 800 gph bilge or 1 4" attwood fan IMO.
A very rough but quick close estimate of finding what size batt you need is:
A batt has an amp/hr rating like the factory one is 18 amp/hrs = can run 18 amps for one hour or 1 amp for 18 hrs to KILL the batt so you need a little headroom. There is a much longer formula for better accuracy, but this should do ya.
07-04-2007, 10:12 AM #6
Great stuff, guys, thanks a bunch. EShakr, can't wait to see your own install.
07-04-2007, 12:51 PM #7
If it would fit, wouldn't running one more powerful battery, instead of two small ones, have it's advantages?
07-04-2007, 01:49 PM #8
But the MO for dual batteries is you leave starter battery out of
loop when at anchor or stopped. That way it is just used for
starting purposes. The house battery can be run til it dies (not a good
idea for longevity) and you can still start motors.
Usually you use a high cranking amp battery for starter and a deep cycle
for accessories (house).
My dual 5.7L SeaRay had 3 batteries, two starter and one house. SeaRay
wired a special ignition switch that if thrown put all batteries into the
circuit. This was in addition to the Perko.
Lots of people use the Perko for theft deterrent. Put it in an out of the
way non obvious place. When leaving craft turn it off and that will prevent
hot wires and other mischief. So Earthshaker putting it back in the aft
of the ski would give another round of protection.
I knew a guy who even went to the extreme of redoing the numbers on
the Perko switch. Off was really On, etc.
07-04-2007, 02:08 PM #9
I have not weighed the factory 18Ah batt. But would likely be a good option for those interested in relocating to unload the front end a bit.
Another reason, and correct me if i am wrong, but won't the mag want to keep up with current draw regardless of batt size?
07-04-2007, 05:38 PM #10
Guys; for those of us who don't need a second battery but want extra reliability and power, is there a better battery than the stock one that I can swap out? On my cars, I always go for the Optima reds; I know they have marine batteries too.
I really don't like the BAT warning when I re-start..
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