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post #1 of 5 Old 01-07-2005 Thread Starter
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Battery Chargers

Electrical systems have always perplexed me, so if someone can lend a thought it would be apprecitated.

I have a two bank battery system on my 30 foot sailboat. The existing battery charger is the old style charger that goes at one speed all the time and appears to be dieing.

I want to upgrade to a smart 3-stage charger which will take care of my two bank set up, but am confused on the different available chargers.

There seems to be numerous variations of the two bank chargers available ranging from 12 to 15 to 30 amps. My confusion comes from where this amperage is measured. Is this the input amperage (ie. the amperage coming from the panel to the charger?) or is it the exit amperage (ie. going from the charger to the battery)?

My shore power comes in to the A/C panel at a 30amp breaker. I have a dedicated circuit at 15amps for the charger.

I''m guessing that the advertised amperage on the charger is going from the panel to the charger, but want to make sure.

Also, if you have a preference on manufacturer or model feel free to share.

Thanks much,

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post #2 of 5 Old 01-07-2005
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Battery Chargers

In my experience the quoted amp rating on a battery charger is the output amps (from charger to the batteries). The input amps (panel to charger) will be about 1/10 of that rating. The 1/10 figure is not exact but is a good working approximation. Also be aware the rated amperage is probably the total available for all banks charged, ie. a charger rated at 30 amps for two banks, will not charge each bank at 30 amps, but will split the 30 amps between the two banks.

Somewhere on the battery charger, you will see the input (AC) voltage and amperage listed. There should also be an output(DC) voltage and amperage listed.

Probably somewhere in the manual for the charger it will detail how the output amperage is divided among the banks.

I''ve seen several references to Calder''s book "Boatowner''s Mechanical & Electrical Manual" on this board. I would highly recommend it for anyone wishing to know more about their boat''s electrical and other systems. As I recall, battery charging is covered in detail.
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post #3 of 5 Old 01-07-2005
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Battery Chargers

Go get yourself a Xantrex 40+ and set it to your battery conditions and forget it. You might want the temp guage and remote panel all plug and play stuff easy on the brain and will do a nice job and you can bost to your buds about your high tech smart charger.They will think your a tech geek when they find out you installed it.
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post #4 of 5 Old 01-14-2005
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Battery Chargers

Garret, here are a couple of web sites you can go to for additional information. The first is Lewco Electric, a battery charger manufactuing company.
The second one is from a wind and solar power manufacturing company.
I have found both of these to be really helpfull in my search to understand batteries and chargers among other things electrical. I have a Lewco charger on my boat and it works great. I have another one for sale if you are interested. Regards, Peter
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post #5 of 5 Old 01-14-2005
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Battery Chargers

I have always liked the Newmar line of chargers. They seem to be MUCH better built than any other chargers on the market.

They have been very helpful whenever I have called them with technical questions during an installation.

About the only downside is price, they run about 50% to 100% more than your average "store bought" unit. But if you want the best, and a unit built to last, they can''t be beat.
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