24volt electronics suppliers?

[stefan_r]

need some leccy bits from Santa (fluxgate compass is number one on the list) but having trouble finding suppliers who sell 24volt stuff...all seems 12volt for basic kit and instrumentation (including the £2,500 Burmarc Gyrotrac compass that is err... bit out of my league frankly even if it was 24volt!!).

Even RayMarine's instrumentation seems to be 12volt only and I really do not want to start running banks of transformers on board.

mailto: stefan@athito.com

 

[paulineb]

Cheapest place for 24volt stuff is a truck dealers/spare parts store. £££s less than chandlers and dealers - don't know about compass thought, never seen a fluxgate one in a truck (not that I've been in lots of trucks - before you pick that one up Barry !!)

Pauline B

 

[byron]

Stefan, check the spec. A lot of this stuff, indeed most of it, will run on voltages from 12 - 36 or even 48 volts. So don't despair.

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[Col]

Your 24V supply comes from 2 X 12V batteries wired in series, just connect your electrics via one of the batteries ( Suitably fused of course )
If you have a lot of kit to fit, take some off each battery.

 

[JohnR]

If you look at the equipement specs then a fair amount is 24v. or there are 24v. versions, often it is marked 10-30v A fair number of bigger boats are 24v

 

[byron]

I don't agree Col. It's bad news to tap batteries in that fashion. My old 24 volt Broom was fitted with a seperate 12 volt panel fed by a voltage dropper. I think a real top quality one with a heap of amps is only about £40.
Anyways as I said earlier most stuff today is designed to run 12 - 36/48 volts.

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[jfm]

Re: Connecting to one battery

I wd have said tap 12v off one off the batteries. Why is it bad news Byron? I see no point at all in a voltage dropper for DC circuitry. Maybe I'm missing something - plse enlighten!

As others have sed many electronic are rated 9v to about 30v these days

 

[byron]

Re: Connecting to one battery

I was always told that batteries should be drawn on evenly. To tap one means they aren't. If I am wrong then forgive me.
A voltage dropper takes evenly at 24 volts from all batteries and delivers 12 volts.

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[stefan_r]

yeah I know but I want to use my existing fuse panel and wiring so would rather stick with 24v supply from services than connect directly from one of the 12v batteries

mailto: stefan@athito.com

 

[stefan_r]

mostly they say 10-16volts...NM

mostly they say 10-16volts...NM

mailto: stefan@athito.com

 

[ccscott49]

dont! do that you will knacker the battery and get all kinds of high volatge spikes on your elctronics and bugger the whole caboodle!

 

[adarcy]

Re 12v from 24v bank

I hate to be pedantic but I do assume we are all meaning that we have 2 12v batteries in series giving out 24v and then taking a feed off one of the said 12v battery.
In which case, I cannot see any problem whatsoever. It's what a 12v battery is designed to do and it doesn't "care" if its attached to another battery to make 24v. The 24v charging circuit doesn't care if all 12 cells are down a bit or 6 of them because when the 24v circuit is made there will be a transfer of charge.
Sure it's not the same as a duff cell in a battery that discharges the whole but I think Byron and ccscott49 are worrying about nothing.
We have always wired our VHF off one 12v out of a bank with no trouble at all. That is permanently wired in case of connection probs.
Stefan_r obviously does not want his fluxgate permanently going and if he doesn't want to get a 12v dropper but does want it through his normal setup obviously only a 24v bit of kit will do. I regret to say, I cannot remember if our fluxgate is 12 or 24v or how it is wired, must have another look.

Anthony

 

[jfm]

Re tapping off 12v

ccscott, please can you say why? Not picking a fight, I'm no expert on this, but what is being said sounds like old wives tale.

What is going to generate spikes? What difference can it make if there is another battery attached in series? If the voltages are different as between the two 12v batteries then there will be a trnasfer of charge when the 24 circuit is made, but so what, batteries are meant to be charged and discharged.

Just doesn't stand to reason. Can you explain a bit more plse?

 

[BarryH]

Re: The ladies right you know

The ladies right you know, Most truck suppliers will sell you a neat little box that will drop the voltage to 12 volts, its noemally used to power radios, CB,s etc. I think I saw one in Maccess the other day priced at about £25+vat. I should think it has enough amps to run a few bits of lecy stuff.

 

[ccscott49]

Re: Re tapping off 12v

All I know is, my brother did this and it bollocksed all his 12 volt gear, I in the meantime not knowing this had happened wired mine the same way, whammo! all my gear bollocksed aswell, something to do with charging volatges, so I'm told, again I did read somewhere about this, but can't remember where, the old hard drive is running at 1/2 speed these days! I'm sure some super wizzkid will come up witha better answer. Also why do they sell a bunch of the 24-12 converters, they must sell a bunch, coz' they're so cheap! Thats what I now use. Never had any further problems!

 

[desG]

Re: Connecting to one battery

Byron, you are quite right. The point is that the same charging current goes through each of the series batteries. You want each battery to be charged to the same level. If the batteries are being discharged unevenly (as they will be if one is just supplying the 12v electrics), you end up with one battery being undercharged and the other over charged.

 

[adarcy]

Re: Connecting to one battery

DesG

I'm not sure you are right. If one 12v is supplying eg a VHF while the rest of the battery circuit is off, then when the circuit is made as when the engines start and the alernator charges, they will have been connected and equalised their charges. Whilst charging is proceeding on both at 24v and some 12v is being "drawn off" the charging current will supply it. Unless I'm mistaken the onlly damage that can occur is when the circuit is made but that is like the surge you get when putting jump leads on to start a car which doesn't seem to cause a lot of trouble. Even if it does cause a little, that is from a highly charged battery to a flat one, whereas we are talking about 2 biggish batteries, one of which has had some charge taken out of it.

Or am I barking up the wrong tree? Please advise beacuse I find this sort of discussion enlightening and we've been doing it for years with no trouble at all.

Anthony

 

[desG]

Re: Connecting to one battery

Anthony

My point is that the charge in the two batteries do not equalise when both are connected in series with the alternator. (Unlike connecting two batteries in parallel)

Take as an example two 100ah batteries that are fully charged with 24v loads switched off and then one (BAT1) supplies a 12volt load that say takes out 25ah charge before the engine is restarted and the alternator starts to recharge the batteries. One battery (BAT2) is still fully charged but the other needs a 25ah recharge. The charging current of course goes through both batteries so the BAT2 is now being overcharged (which will affect the battery life). The charging current will continue until the sum of the two batteries voltages reaches some value at which the regulator stops the alternator charging. Say this is 28volts. Normal if each battery has the same charge, each would now be 14volt. But because BAT2 is being overcharged, when the series voltage reaches 28volt, BAT2 will be higher that 14volt (say15V), thus BAT1 must be less (13v in example) but the charging stops, so BAT1 remains undercharged. Although you may not be aware of it, you are not utilising the full capacity of the batteries and shortening the life of one.

I guess you could get away with it if the 12volt load is only a small percentage of the total normal 24v load but I think the practice it is not to be generally recommended.

Des

 

[adarcy]

Re: Connecting to one battery

Des

Thank you for an admirably clear explanation.
Of course, I as wrong in using connecting a jump start battery as that is in parallel whereas we are (should be) talking about in series.
I can see your point especially if one runs one battery down a significant amount but also agree that you think it is not v important if only a small amount of charge is taken out. Effectively that probably happens in all batteries as they age, one would have thought it unlikely that all the cells in a pack age at the same rate but we only notice a problem when one cell goes really duff..

Perhaps the best way if one wishes to take a direct 12v off (in our position we don't want anything between the battery and the VHF that could go wrong - it's the wiring or the battery only if kaput) would be to take a small charge out of multiple 12v batteries rather then all out of one battery.

Thank you again.

Anthony