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Batteries

2K views 14 replies 11 participants last post by  Aquarius 
Battery Isolator

I have two batteries, two switches and an isolator. I did the install last season and have not had a problem. BOth batteries are always on line. I have one starting battery that does nothing but crank my single diesel engine. The deep cycle does nothing but power electronics and lights. The switches allow me to double them up or take one off line for any possible problems. I can leave my electronics on while I drift. Starting will not knock out the electronics since the batteries are isolated. I can leave lights on, drain the deep cycle, and not drain any power from the starting battery. It is not necessary to flip any switches for normal ops. Only for an emergency. The system so far has worked great.
 
Cost of isolator

The cost of the isolator was about $100. I did the install myself. I made other upgrades to my 20 year old boats electrical system as well. I will give you an idea of what I did, the cost, and how much time I spent.

The previous owner had installed a 90 amp altenator. Up from the original 50 amp. The wiring was undersized, so I replaced the altenator cables. I also ran new auxiliary wiring to my main fuse panel. Again, these wires were terribly undersized. I installed one new battery switch. I combined it with the exsisting. The new switch had a 1000 amp rating. I have a diesel and draw heavy current on start up. The original switch was rated at 500 amps, again, too small. The new switch also ran about $100. In selecting the wires, I went to the charts in the West Marine Catalog. I measured the total distance run, multiplied by two for both lengths, used the column for 3% voltage drop and added another factor for high temperature since the wires are in my engine compartment. As a result, I ran size 2 wires to my auxiliary panel and size 4 from my altenator. Those are almost battery cables themselves. The price was about $3.50 per foot. I spent a few bucks on wire to tell you the truth, but, I think it is worth it. Add in the connections, heat shrink tubbing and a few other things, I spent about $400, and about two days of my time. You don't have to go as far as I did. I now have two swithches. One for the starting battery and one for the auxiliary battery. Normal ops are to keep the systems seperate. In an emergency, I can use the starting battery to power auxiliaries, use the auxiliary to start, or put both batteries on line together. Both systems can also be kept completely seperate.

The logic behind this is to use the starting battery for only the short burts of power needed at startup. The deepcycle will only be used for starting in an emergency. Normally it just powers electronics and auxiliarys. I can start my engine with the electronics powered up and not hit them with a low voltage spike. I can drain the deepcycle and the starting battery will remain untouched. The batteries will last longer when they are only used for thier designed purpose. Using both batteries all the time is fine as long as the systems remain isolated.

Feel free to ask anymore questions if you have them.
 
To any one who read my above post, that is the same battery that I use to crank my diesel. Even on a cold day (45deg), there is not much of a voltage drop when starting a 120 Lehman.
 
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