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what size battery isolater ?


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Hi folks, i now it is probably a stupid question but i will ask any way. If my 24volt doemestic battery bank consists of 6 12volt 110 AMP hour batteries wired in series/parralel, will i be ok fitting a 250 amp isolator and does it have to be a 24 volt one or will a 12 volt one be ok ? Also while i think about it! what comes first the 300 amp fuse or the battery isolater ? thank you for your input :cheers:

Edited by micky44
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It is unlikely that a 12V isolator will be rated less than 24VDC so yes on both counts (provided 250A is enough on the supply side) but check the isolator specs. I recommend Bluesea switches - avoid cheapo red flag isolatora

Thank you for the reply, i have just noticed that my Sterling combi, 2500W requires a 300amp fuse! so am i right in thinking that the said 250amp batt iso will be ok ? sorry to be a pain :cheers:

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Thank you for the reply, i have just noticed that my Sterling combi, 2500W requires a 300amp fuse! so am i right in thinking that the said 250amp batt iso will be ok ? sorry to be a pain :cheers:

 

2500W is around 125A at full chug then yes, in theory.

 

Which 250A isolator are you looking at?

 

They are not all equal (or all equal to the job). The main problem with isolators is once they start to develop problems they develop resistance = heat which exacerbates the problem.

 

Mind 330Ah is not a lot to run a 2500W inverter.

Edited by Chris Pink
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2500W is around 250A at full chug so if your isolator is rated at 250A continuous and a higher figure for intermittent then yes, in theory. As Bluesea do a 350A isolator for not a lot more that's what I'd go for.

 

Which 250A isolator are you looking at?

 

They are not all equal (or all equal to the job). The main problem with isolators is once they start to develop problems they develop resistance = heat which exacerbates the problem.

dont yell at me but i had seen a cheap one at midland swidlers surface mount about a tenner!http://www.midlandchandlers.co.uk/Products/Electrical/IsolationSwitches/VS259.aspx

Edited by micky44
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2500W is around 125A at full chug then yes, in theory.

 

Which 250A isolator are you looking at?

 

They are not all equal (or all equal to the job). The main problem with isolators is once they start to develop problems they develop resistance = heat which exacerbates the problem.

 

Mind 330Ah is not a lot to run a 2500W inverter.

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yes i know what your saying about 330amp, the problem is i do have several more batteries in fact another 4, but they are all different amp hour cappacity, i.e 90, 100, and 120 amp, was thinking i would be better sticking to the 4 batteries with all the same amp hour ?

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330Ah is fine as long as you're not going to be running the inverter for long periods at high power.

 

It's the inverter that's over-spec rather than the batteries under spec for normal narrow boat liveaboard use though I don't know how you're planning to put the power back in.

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:smiley_offtopic:

 

I run my fully electric boat of a 330 amp.hr @24v bank with a 2Kva inverter.

 

 

 

ps. the same set up as the OP, if I read his post correctly ;)

 

Once again you dangle an disingenuous post in front of a discussion about electrics.

 

You say you have some of the same equipment as the OP

 

Why don't you run it from a 4 pot Lister and a 140A lorry alternator?

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Thank you for all your advice, i dont want to start a new thread so will tag my question on here if i may. i have some 95mm2 cable left over, would it be worth me using this to connect my alternator to my battery bank? :cheers:

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Nice bit of kit, 3.5Kw for £100

Yes it had to be bought, it weighs 15kg!my engine revs at 1200rpm when i am just going steady, its not too noisey at this speed and does not make the crockery rattle! the lister had a 200mm o/d fly wheel on it, the alternator shaft is 30mm ! i have had a new fly wheel cast twin groove z section, 260mm o/d and managed to get a 67mm pilot bore pulley machined out to 30mm inside o/d with a 8mm key way. This set up has given me a ratio of 3.8 /1 which even on tick over 550rpm gives an alternator spindle speed of 2134 revs, at 1200rpm it gives a alt speed of 4560 rpm, sounds good in theory, will report back when the fly wheel is deleverd . And i have managed to fabricate 2 sets of altenator brackets, one for the feeble 35amp 12 volt altertnator for the starter motor, (could not source a 24 volt starter motor )and of course one for big bertha, still struggling to work out the tensionong on bertha though, as i posted several months, the days of the sr4 plodding along not under load are over! she wont know whats hit her,

Edited by micky44
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Once again you dangle an disingenuous post in front of a discussion about electrics.

 

 

Oh dear bottle , looks like you interrupted the electrical "master" when he was in full one to one flow. You really ought to know better laugh.giflaugh.giflaugh.gif

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Thank you for all your advice, i dont want to start a new thread so will tag my question on here if i may. i have some 95mm2 cable left over, would it be worth me using this to connect my alternator to my battery bank? :cheers:

 

Yes. If it was me I'd spend a bit more on a chunkier switch. It's a fairly heavy duty setup even if the switch is within its limit.

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2500W is around 125A at full chug then yes, in theory.

 

Mind 330Ah is not a lot to run a 2500W inverter.

Although dont forget, while not wishing to teach grandmas to such eggs, that 330Ah at 24vdc is worth twice that at 12vdc.

 

We use vetus branded ones of these on our boat, dont know how they are considered on here, but its done ok running a 24vdc 3500kw bow thruster.

http://www.ebay.co.uk/itm/DUAL-BATTERY-ISOLATOR-SWITCH-300amp-175a-FIVE-OCEANS-/270840076909

 

The red flag ones vary make to make too, some are quite good, especially the 'msa spec' ones used on race cars which have additional no and nc contacts for cutting the engine and earthing the output of alternator.

 

 

 

Daniel

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Oh dear bottle , looks like you interrupted the electrical "master" when he was in full one to one flow. You really ought to know better laugh.giflaugh.giflaugh.gif

It's a fair point, bottle is neglecting to mention (as always) he's got a 7kW genny with batt charger too presumably, which comes on whenever he uses the electric hob! :P Both you and bottle are free to offer some useful advice of your own... :rolleyes:

 

Anyway the link to the Blue Sea isolator looks like a good deal, the isolators with a metal key that locks down seem to be well regarded too.:

http://www.ebay.co.uk/itm/221067408502

 

cheers, Pete.

~smpt~

Edited by smileypete
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