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Old 07 December 2007, 11:50   #11
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Hightower;

Sounds like your suspect battery is already out of the boat? Take it to a local mechanics, and have them run a load test on it. Over here, most will do it for free (anticipating sales of new batteries, most likely.) They may be able to shock charge it as well, which may get a little more time out of it (not really something I believe in, but some do.)

BTW, what you have is commonly called a battery switch, rather than an isolator. What is commonly called an isolator is an electronic module that senses a charge-capable voltage at one terminal, and opens to allow both batteries to be charged. If it doesn't sense a charging voltage, it remains closed, allowing drain off only one battery (depending on how your load is wired up.)

I have 2 batteries and a switch, much like your setup. One of these days, I'll drop an isolator in as well, so I don't have to remember to hit the switch to get a charge on both batts. I subscribe to the " 'Both' only in emergencies" school of thought.

jky
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Old 07 December 2007, 14:16   #12
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When charging both batteries at the same time which battery will charge first if the batteries are of different amperage capacities?
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Old 07 December 2007, 16:42   #13
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There may be reasons for this not being true but, if the batteries are of the same type, I think they will charge together and become fully charged at pretty much the same time.
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Old 09 December 2007, 20:54   #14
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There may be reasons for this not being true but, if the batteries are of the same type, I think they will charge together and become fully charged at pretty much the same time.
If you have the two paralleled, the voltage will be the same on both by default.

Whether or not they reach full charge at the same time is another matter, but the charging voltage they see will be the same. Assuming they are equally drained, and in roughly the same condition, then yes, they should attain full charge about the same time.

If they are not equally drained, setting the switch to "both" will equalize the condition (based on voltage and assuming again they are both in similar condition), and we're back to square one.

There may be an issue if you have one fairly flat battery and one fairly charged; there will be nothing to limit the current from one battery to the other (other than internal battery resistance and whatever is in the cables and switch), so the surge can be pretty dramatic.

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Old 09 December 2007, 23:09   #15
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Originally Posted by jyasaki View Post
Hightower;

Sounds like your suspect battery is already out of the boat? Take it to a local mechanics, and have them run a load test on it. Over here, most will do it for free (anticipating sales of new batteries, most likely.) They may be able to shock charge it as well, which may get a little more time out of it (not really something I believe in, but some do.)

BTW, what you have is commonly called a battery switch, rather than an isolator. What is commonly called an isolator is an electronic module that senses a charge-capable voltage at one terminal, and opens to allow both batteries to be charged. If it doesn't sense a charging voltage, it remains closed, allowing drain off only one battery (depending on how your load is wired up.)

I have 2 batteries and a switch, much like your setup. One of these days, I'll drop an isolator in as well, so I don't have to remember to hit the switch to get a charge on both batts. I subscribe to the " 'Both' only in emergencies" school of thought.

jky
I used this set up for mine

http://bluesea.com/category/2/productline/overview/329
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Old 10 December 2007, 14:32   #16
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Check your drawing, the batteries are not connected in 'series'
You need the negative of the first to be connected to the positive of the other battery.

ie

- (Batery one) + - (battery two) +

This would double the voltage of your two 12 volt batteries
12 volts + 12 volts = 24 volts

if you connect in parallel it would stay at 12 volts but the available power would be double (roughly), I have used this on many old cars/vans.
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Old 10 December 2007, 14:41   #17
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Andy,

I thought you were only supposed to have the switch set to the "both" setting in an emergency when you need to parallel the batteries together in order to get a boost,

I may be wrong on this but leaving the switch set to both when you are running is not good.

I would speak to Merlin Electronics 01202 697979 . They sell Blue Sea stuff so could help.

Chris
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Old 10 December 2007, 17:05   #18
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Have you got a pic of the isolator Andy?
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Old 11 December 2007, 11:43   #19
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I may be wrong on this but leaving the switch set to both when you are running is not good.
I don't think that it's "not good" in the sense that you'll damage anything, but it defeats the purpose of having two batteries (assuming you have two for redundancy rather than additional cranking capacity.)

Generally, you should leave the switch set to one battery or the other such that if you drain the thing to where it won't crank the motor, you can simply switch to the other battery and still get the motor started.

If you run set to both and run them flat (which will take twice as long, theoretically), you're dead in the water (so to speak... hopefully.)

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Old 11 December 2007, 13:30   #20
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On his drawing he has connected the negatives on the batteries togethor, this is wrong? IMHO Or is it right? IYHO
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