Battery Isolators

ARCWINSTON

Petty Officer 3rd Class
Joined
Oct 21, 2003
Messages
80
I am investigating the ins and outs of using an isolator to distribute the charging current from my outboard. Does anyone have words of wisdom/warning about this. I am looking at Hellroaring brand and Charles brand but am very open to suggestions/recommendations.Thanks...W
 

18rabbit

Captain
Joined
Nov 14, 2003
Messages
3,202
Re: Battery Isolators

A battery isolator (a.k.a. diode on steroids) only limits the battery with the most umph from dumping back into the battery with the greatest need. The battery with the greatest need is the one that “sees” the charging source.<br /><br />When I was researching a design for our boat’s electrical system I bumped into something called “echo charging.” It is a ‘smart’ technology that daisy chains and/or splits the charging source to multiple battery banks.<br /> http://www.xantrex.com/products/product.asp?did=188 <br /><br />If charging on the fly, the addition of a regulator can offer true 3-stage charging (bulk/accept/float) from your alternator. This condition creates a “fully” charged battery. As a rule, alternators do not charge a battery more than about 80%. They can do more but the way we use our boats it is unlikely to happen and we need to be charging our bats once we get back to terra firma.<br /> http://www.xantrex.com/products/product.asp?did=189 <br /><br />If you read the marine product description and especially the user manuals on the Xantrex web site, you will learn more than you ever really wanted to know about battery charging. But you’ll be happy you did. :) :) :)
 

Boatist

Rear Admiral
Joined
Apr 22, 2002
Messages
4,552
Re: Battery Isolators

ARCWINSTON<br />I have been useing a battery isolator since 1980 and never had a battery that did not last 6 years. For my boat it is my choice. Having said that I must ask some questions. My boat is a I/O with a 35 amp alternator. The isolator does a great job of stoping a bad battery from discharging a good battery. Also you are not going to blow your alternator from someone turning a switch at the wrong time. <br /><br />1: What type batteries are you charging and what is there use??<br />2: What size alternator does your outboard have??<br /><br />If you have a large outboard with a 30 amp belt driven alternator or more the isolator should work just fine.<br /><br />If you have a outboard with a 6 or 12 amp built in alternator then may not be a good choice.<br /><br />Now if you have a starting battery and a deep cycle and the deep cycle runs a electric trolling motor. Then you need a large alternator if you want to charge both batteries. A small 6 or 12 amp alternator trying to charge both a starting battery and a run down trolling motor battery is not a good Idea. First the small amps will not charge your trolling motor battery back up unless you run for many hours. Second your alternator will be running at max amps all the time and that will shorten its life. Third the discharged trolling motor battery would get most of the current and your starting motor may not get charged up.<br /><br />As far as type of isolator, you want one that at least twice the amps of your alternator. 30 amp alternator then get a 70 amp isolator.
 

18rabbit

Captain
Joined
Nov 14, 2003
Messages
3,202
Re: Battery Isolators

What I learned about batteries, charging and onboard wiring, had isolators pop up as petty much a needless item. Boatist nailed it, maintaining you bats will increase their useful life. And the better maintained (fully recharged), the longer the bat life.<br /><br />To fully charge a bat w/o over charging, you need a 3-stage charger. The charging process passes thru stages of high amps/low voltage to low amp/high voltage to top off for a fully charged bat. This is something an alternator is not designed for, but a smart regulator is. This is why you cannot get a bat fully charged with your typical alternator alone. If you could, you would cook your batteries.<br /><br />Echo charging takes the regulated output and manages it for multi bank, 3-stage bat charging. There is no need for an isolator.<br /><br />I think what Boatist said about not taxing the alternator’s output cannot be over emphasized. You definitely need an alternator beefy enough to support the bats charging demand and/or the onboard amp draw. A regulator can monitor the alts output and temp to prevent potential damage. An echo charger does the same for input into the bats.<br /><br />Arcwinston – what you are going toward is not ideal and does require an additional charging source be applied to the bats when you return, for it to be so. That said, the isolator will do no harm if the alt is up to the challenge. However, your isolator $$$ might be better spent investing in a good 3-stage charger for when you get back to the barn, presuming of course, you have an appropriately size deep cycle to meet your daily amp needs.
 

Boatist

Rear Admiral
Joined
Apr 22, 2002
Messages
4,552
Re: Battery Isolators

rickdb1boat<br />That is not good reading it is great reading. I like the D configutation. Isolator will charge both batteries and save your alternator even with cheap switch that does not have a field disconnect switch. Switch still allows you to start engine from either battery.<br /><br />Thanks for the great link.
 

ARCWINSTON

Petty Officer 3rd Class
Joined
Oct 21, 2003
Messages
80
Re: Battery Isolators

Gentlemen,<br /> Some good advice here...exactly why I asked BEFORE I buy. Just to clarify, I'm not looking to eliminate battery maintainence <br />(all my batteries spend their off water time connected to 3 stage chargers). I do a lot of night fishing and sometimes stay on the water for several days at a time. My new boat has everything except the trolling motor connected to the cranking battery. That's probably Ok if all I did was daylight fishing but not so good when the anchor lights, bait tank pumps, work lights, ect. have been in use all night and I need to know the motor will crank in the morning. I would like to draw "general" power from the deep cycle trolling batteries (which I very rarely use for trolling) and leave the cranking battery to do only that. I thought that maybe an isolator would allow me to perhaps top up the trolling batteries a bit whenever the engine was running. I'm not completely sure that the deep cycles won't last for several days. I am just exploring options.<br /> The thing I really like about this site is the depth of knowledge and experience available just for the asking. thanks...W
 
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