Battery Bank Location.

[micky44]

thank you all for your replys, so are we saying i could get away withmy battery bank in the bow if i used the 25mm solid cabble from the alternater to the battery bank thanks.

Edited March 16, 2012 by micky44

[Chalky]

thank you all for your replys, so are we saying i could get away withmy battery bank in the bow if i used the 25mm solid cabble? thanks.

 

NO. You need to look at the volt drops and the length of the run.

 

Assuming the cable run from the alternator to the battery is 20m each way gives a 40m round trip (can't use hull as return)

Assume you want to run a maximum of l00A through it.

 

Using this cable sizing tool http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

 

for 5% power loss you need 150mm squared cable

for 4% power loss you need 185mm squared cable

for 3% power loss you need 240mm squared cable

for 2% power loss you need 400mm squared cable

 

The losses are due to the length of the cable. Put the batteries by the engine and buy some ballast for the bow.

 

Some high spec luxury cars have the battery in the boot and the alternator in the front. The run is less than 4m yet they use 70mm squared cable. You're running nearly 10 times the difference. Yes the increase in voltage will help due to the drop in current, but not that much. For the distances your talking of you'll need a BIG cable.

 

From http://www.clevelandcable.com/products.asp?id=4397&step=2

 

150mm csa cable - 1440kg/km

185mm cas cable - 1776kg/km

240mm csa cable - 2304kg/km

400mm csa cable - 3750kg/kg

Edited March 16, 2012 by Chalky

[Taslim]

thank you all for your replys, so are we saying i could get away withmy battery bank in the bow if i used the 25mm solid cabble? thanks.

 

The cable sizes sorted but my first reaction to your initial post was, 'can be done electrically but what to do about ventilation? Obviously I don't know your boats' build or layout.

 

taslim.

[micky44]

NO. You need to look at the volt drops and the length of the run.

 

Assuming the cable run from the alternator to the battery is 20m each way gives a 40m round trip (can't use hull as return)

Assume you want to run a maximum of l00A through it.

 

Using this cable sizing tool http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

 

for 5% power loss you need 150mm squared cable

for 4% power loss you need 185mm squared cable

for 3% power loss you need 240mm squared cable

for 2% power loss you need 400mm squared cable

 

The losses are due to the length of the cable. Put the batteries by the engine and buy some ballast for the bow.

thanks for that.

but i am on 24 volts,.10 lead acid batterys 140 amp each, series/parrell which is 700 amps at 24 volt. my cable would be 25mm dia, not 400mm2.

Some high spec luxury cars have the battery in the boot and the alternator in the front. The run is less than 4m yet they use 70mm squared cable. You're running nearly 10 times the difference. Yes the increase in voltage will help due to the drop in current, but not that much. For the distances your talking of you'll need a BIG cable.

[Bob18]

Not a lot to add to Chalky's comments in post #27, apart from you'd be in for a hernia or two just getting the sort of cable you need into the boat...

 

While 25mm will carry the current, it will get "quite warm" doing so over any distance, and have a significant voltage drop between the alternator and the battery terminal. (under charge) will mean the batteries will suffer from under-charging, unless you have a "battery sensed" alternator, connected by the appropriate sized cable to the battery bank.

 

Stick with "tradition" - there's a very good reason why the vast majority of boats have their battery banks very close to the engine....

[Chalky]

Yes, buy you'll still be charging them off your alternator. What current does it produce? It's all about volt drops in the cable, not the cables ability to carry current.

[micky44]

you are quite correct about luxury cars haing the battery in the boot, again the ole man has several rollers, all with the battery in the boot. bit i would still like my question ansewring. with 25mm diametre solid cable could i run my alternater feed to the battery bank approx 40 feet from the alternator, 24 volt 200 anp, alternater. thank you.

[Bob18]

thank you all for your replys, so are we saying i could get away withmy battery bank in the bow if i used the 25mm solid cabble from the alternater to the battery bank thanks.

 

No, we are not saying that, indeed we are saying two things, first that 25mm cable is very inadequate, and second, unless you are going to construct some "very clever" bus-bars then doing it in solid cable will be "next to impossible (setting aside the debate over solid cables being "permitted or not")

[Chalky]

At maximum alternator output of 200A with a 40m cable run at 24V you'd loose 4% of your power in the cable if you used a 400mm squared cable. That's about 200W going to heat up a very big cable. 3% loss required a 500mm squared cable.

[blodger]

you are quite correct about luxury cars haing the battery in the boot, again the ole man has several rollers, all with the battery in the boot. bit i would still like my question ansewring. with 25mm diametre solid cable could i run my alternater feed to the battery bank approx 40 feet from the alternator, 24 volt 200 anp, alternater. thank you.

I think the answer is yes you can 25mm diam equates to 3.142x12.5x12.5 mm squared

[Chalky]

Quick check on terminology. Electrical engineers talk about cross sectional area of cables. Mechanical engineers talk about diameters of bars. I'm an electrical engineer so all of my references are in square mm.

[Bob18]

Ah, we are suffering the age old problem - cables aren't measured by their DIAMETER, but by their CROSS SECTIONAL AREA - a 25mm DIA cable is about 490sqmm cross section.

 

See my my post #33 for comments about "solid" cables/bus-bars.

 

(Even installing a 500sqmm stranded cable would be a struggle, as they aren't particularly flexible unless you spend an absolute fortune on some really fancy type of cable construction...)

[micky44]

i am probably missing some thing here, so please forgive me. the out side diametre of the solid copper cable is 25 mm or 1 inch in english, none of this 400mm2 , i dont understand that ! can or can not do. thanks.

[Chalky]

Pi * r ^2 gives 25mm cable as 490mm squared. That should work, but it'll be a bu$%£r to connect to. It's also very valuable and heavy so it may affect your trim some what.

 

As Bob18 said you need your alternator to be load sensing not machine sensing for best operation. If you can fit the batteries closed to the alternators I'd do it and sell the copper cable.

[micky44]

No, we are not saying that, indeed we are saying two things, first that 25mm cable is very inadequate, and second, unless you are going to construct some "very clever" bus-bars then doing it in solid cable will be "next to impossible (setting aside the debate over solid cables being "permitted or not")

right thanks, but it would only be the feed from the alternator to the battery bank.

[Bob18]

See blodger's post #35 - the only thing he didn't do was the sum, which I'll do for him:

12.5 x 12.5 x 3.314 = 490.9375 square mm

 

If you go to a cable supplier and ask for "25mm cable" you will get something a lot smaller than what you want - it will be about 6mm in diameter (1/4 inch!)

 

I haven't got the cable size conversion tables to hand, but in US parlance a "500sqmm" cable is probably about a "000" cable (I'm sure someone will correct me...), and in old Imperial sizes? (I've never had to use them...). Whatever its a "figging big" cable to have to handle and terminate without the proper equipment...

 

right thanks, but it would only be the feed from the alternator to the battery bank.

 

WRONG - On a narrowboat you would have TWO cables between the battery and the alternator (one for the positive, and one for the negative) as you should/must never, ever, ever, ever, ever, ever, ever, ever use the boat hull as the return, which is normally the negative (This is totally unlike cars...).

[Chalky]

Whatever its a "figging big" cable to have to handle and terminate without the proper equipment...

 

We use hydraulic crimpers to attach terminals to 50mm cables. 490mm is a whole new ball game, especially if you want to attach cables of a more "normal" size to attach to batteries and alternators.

 

Where's the distribution panel going? This'll need attaching to the batteries as well.

[micky44]

again thank you for the replys, glad we sorted tht out!my problem is i do not think i can accomodate 10 batteries in the engine room, and as all ready stated the bow is high, fitting the batts in the mid engine room would only make matters worse with regards ballast ? hence siting them under the tug deck. thanks.

[Chalky]

(This is totally unlike cars...).

 

Agreed - I think Bob18 and I are in the same industry...

[RLWP]

We use hydraulic crimpers to attach terminals to 50mm cables. 490mm is a whole new ball game, especially if you want to attach cables of a more "normal" size to attach to batteries and alternators.

 

Where's the distribution panel going? This'll need attaching to the batteries as well.

 

Should you be crazy enough to work with single strand, 25mm diameter cable, the best bet would probably be to forge the end flat and drill a hole through it...

 

I have a forge in the garden if that helps?

 

Richard

[bizzard]

If Mohamed won't go the mountain why not take the mountain to Mohamed.

Bolt a 40' shaft to the engines crankshaft and stick the alternator on the end of it next to the batteries.

Lots of plumber block bearing saddles would be required though, but no belt slip.

[Grace and Favour]

Should you be crazy enough to work with single strand, 25mm diameter cable, the best bet would probably be to forge the end flat and drill a hole through it...

 

I have a forge in the garden if that helps?

 

Richard

 

I can't help wondering - - - -- if all this cable is on one side of the boat . . . .

 

How much ballast will be needed on the other side?

[Ally]

It seems to me you are reasonably determined to do it regardless of what is said....but £700 odd would buy an awful lot of ballast, OR you can use the under deck space for other heavy items, storage, water tank, calorifier, washing machine etc etc. We have a smallish engine room so bought sealed AGM batteries to stand on their sides to fit....and nothing to stop them being mounted above each other so long as they are secure.

I believe there is always a way around things, the way you are proposing, to be honest, sounds like determination to use what you have however it may or may not comply/work.

No offence intended, but that's how it reads.

[bizzard]

If Mohamed won't go the mountain why not take the mountain to Mohamed.

Bolt a 40' shaft to the engines crankshaft and stick the alternator on the end of it next to the batteries.

Lots of plumber block bearing saddles would be required though, but no belt slip.

I expect your engines on rubber mountings so the first part of the shaft at the engine end would need a double UJ, an Aqua or python drive or a vehicles propshaft could be adapted.The series of bearing block saddles will need careful aligning with dial gauge and shims for it to run true. A 2''mild steel shaft should be adequate. If you refer to ''Fowlers machinists pocket book'' the correct procedure for these shafting arrangements are fully explained.

[David Mack]

If Mohamed won't go the mountain why not take the mountain to Mohamed.

Bolt a 40' shaft to the engines crankshaft and stick the alternator on the end of it next to the batteries.

Lots of plumber block bearing saddles would be required though, but no belt slip.

 

Would 25mm diameter copper do for the shaft?