Forums Announcements staring battery and winch battery size

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    • #225003
      Rock Richardson

      what size stating battery and winch battery do I need with my westerbeake 58 (I have a lofrans tiger winch) currently I have one deep cycle 100 ah and the same for the winch. I plan on moving the two deep cycle batteries to my one 100 ah deep cycle house bank. but need to get a battery for the starting and winch

    • #225004
      Bryan Bywalec

      Hey Rock,

      You might have more luck if you post in the General Discussion section of the site.

      To answer your question, almost any commonly sold automotive diesel starting battery will work. The manual is silent on sizing. Common automotive diesel engines are much larger and can be started easily. That being said, it is always nice to size the start battery as an emergency reserve so up-sizing is common and a matter of personal preference.

      AS for the windlass, I highly recommend just biting the bullet and running large diameter wires from your house bank to the windlass. It is a waste to carry around a battery in the bow to save money on wiring when you could then use that battery to buffer the amp hours you are drawing from the house bank. This is especially true considering you probably only run the windlass when the engine is running.

      Bryan Bywalec
      S/V Pelican, Hull 209
      Siren Engineering, LLC

    • #225005

      I have a Lofrans Tigress on my 424. I use my house batteries to power my windlass. This is done with 2/0 gauge battery cable from the batteries to the winch. IMHO, this is the best way to power a windlass. I run the engine when pulling an anchor so the voltage applied to the windlass is near the 14.4v acceptance voltage provided by the alternator. Many folks put a separate battery up in the forepeak to power their windlass and use smaller gauge wire because the 2/0 stuff is expensive. I think this is a less effective way to power the winch. When powered this way, the voltage provided to the windlass will be less than 12v because power provided by the alternator is lost in the cable. When you use the windlass, you draw most of the power from the forward battery. The battery voltage drops. If the windlass sees 10V instead of 14V, it will have power reduced by about 30%. Assuming that you have a big alternator and wire it with proper heavy gauge wire, the installation doesn’t draw power from the battery but instead draws it from the alternator. Battery size doesn’t matter.

      I have a separate starter battery, the largest car battery Sam’s Club sells. It’s mounted in the shelf behind the hanging locker. This is overkill but the thing fits there, no problem. Even if I run down my house batteries, the engine will start. I have two alternators in my installation but it can be done with one as long as the starter and house batteries remain isolated when the engine is not running. The cheapest and most reliable way to do this is to connect a 6v relay to your alternator tach output (e.g. Amazon – Uxcell DPDT 8 Pin 5 Amp 240VAC/28VDC MY2J) and use this to close a solenoid switch available at any RV/Camper supply store or Amazon (e.g. Cole Hersee). The solenoid switch connects the starter battery to the charging circuit. The house batteries always remain connected. Once the engine starts, it combines the batteries so your house batteries get charged. There are of course other ways to do this. Contact me if you have questions about hooking this up.


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