What to ask for in fitout?

[blackrose]

@blackrose

 

I said, "if you have a generator or alternator big enough" and you came back, "Given the same size alternator or generator/battery charger.............................."

 

We are at cross purposes!

 

@mross

 

I said "You can have as big a battery bank as you like, but when it's down at 50% capacity it's going to take a lot longer to recharge than a smaller bank." and you then came back "If you have a generator or alternator big enough, the time to charge the batteries will be the same regardless of the battery bank capacity. That is to say, a bigger bank does not take longer to charge."

 

We are indeed at cross purposes because I was talking about charging both banks from 50% capacity with the same charging system. Of course if you upgrade the charging system then the bigger bank is going to charge quicker.

The charging will be the same time, and potentially less with a larger bank as even with the same charging equipment optimised for a small bank you still only be adding what you took out and you'll have longer in between charge times...

 

Not if you're charging both banks from 50% capacity [to fully charged as you should always try to do] which is what I said in my posts above.

Edited January 29, 2017 by blackrose

[mross]

Regardless of the capacity you can get the same charging time with a big enough generator / alternator. Double the capacity, double the charging amps!

[blackrose]

Regardless of the capacity you can get the same charging time with a big enough generator / alternator. Double the capacity, double the charging amps!

 

Post 70:

 

It's very easy to increase one's battery bank size, but not so easy to support larger battery banks with adequate charging equipment/regimes. If what you said were true we'd all have huge battery banks.

 

My point is that as well as finding space for big battery banks batteries, it can also become impractical and very expensive to install big generators or massive alternators on boats.

Edited January 29, 2017 by blackrose

[mross]

The OP could look at the newer battery technologies.

 

http://www.cruisingworld.com/how/replacing-batteries-do-your-homework-firstThis dates from 2012 but is quite interesting.

 

http://www.mastervolt.com/products/li-ion/

[Robbo]

Post 70:

 

It's very easy to increase one's battery bank size, but not so easy to support larger battery banks with adequate charging equipment/regimes. If what you said were true we'd all have huge battery banks.

 

My point is that as well as finding space for big battery banks batteries, it can also become impractical and very expensive to install big generators or massive alternators on boats.

As the OP is getting the boat built and is planning stage he has the choice of easily balancing all the systems required for an efficient charging system for the amount of daily ah's he uses and the amount of between times he wants. As the OP sounds to like a very large daily usage (which I believe can be reduced by quiet a bit) then he will need some serious charging equipment.

[Alan de Enfield]

 

Now I'm confused... if you've got your estimated power requirements down to 300Ah a day, isn't a 1200Ah battery bank overkill? I mean, surely the starting point is to have 600Ah capacity and aim to put back most of what you take out every day.

 

 

 

No

 

Assuming you do not want to take your batteries below 50% SoC, then you need a 600Ah bank.

Working on the principal of not wanting to run the engine / generator every day, most people work on a minimum of having a '3-day battery capacity', so that would actually give a required bank of 1800Ah.

 

My usage reckons to be around 100Ah-150Ah per day.

I have 6x 230Ah batteries giving me approximately a 5-day 'window' before charging. In practice the solar (170W 'low-light' panel) potentially provides in excess of 50Ah per day in Summer so I have even more 'freedom'.

[MtB]

I have a 225AH 24v battery bank and daily use of about 20-30AH. This allows me to recharge once a week which is mightily convenient.

 

Proportionally, should the OP wish to recharge once a week like me, he will need 2,250AH of battery at 24V. That's 41 ordinary 110AH 12v leisure batteries. That puts his proposed power consumption in a different light doesn't it?!

[mross]

The Mastervolt lithium battery (24V and 180 Ah) can be charged at 500A. But it costs £4,200 plus VAT!

[MtB]

The Mastervolt lithium battery (24V and 180 Ah) can be charged at 500A. But it costs £4,200 plus VAT!

 

 

And I'd imagine a 500A charger would cost even more than that!

[magictime]

 

No

 

Assuming you do not want to take your batteries below 50% SoC, then you need a 600Ah bank.

Working on the principal of not wanting to run the engine / generator every day, most people work on a minimum of having a '3-day battery capacity', so that would actually give a required bank of 1800Ah.

 

My usage reckons to be around 100Ah-150Ah per day.

I have 6x 230Ah batteries giving me approximately a 5-day 'window' before charging. In practice the solar (170W 'low-light' panel) potentially provides in excess of 50Ah per day in Summer so I have even more 'freedom'.

 

I have a 225AH 24v battery bank and daily use of about 20-30AH. This allows me to recharge once a week which is mightily convenient.

 

Proportionally, should the OP wish to recharge once a week like me, he will need 2,250AH of battery at 24V. That's 41 ordinary 110AH 12v leisure batteries. That puts his proposed power consumption in a different light doesn't it?!

 

Well OK, clearly the longer you want to go between charges, the larger a battery bank you need. But with an 800-1000W solar array and daily power usage of 300Ah, wouldn't the OP effectively be fully recharging pretty much every every day for maybe six months of the year, and needing a top-up from the generator maybe once a week during another three, and only needing to run the generator every day or two in the depths of winter? Which would suggest to me that in terms of planning his boat, the balance tips away from a large bank and towards a smaller bank that's more frequently charged.

[mross]

Perhaps a diesel generator DC? Instead of an AC one

[David Mack]

 

 

And I'd imagine a 500A charger would cost even more than that!

A charger giving 500A at 24V would draw more than 50A from the mains. Where is the OP going to find a mooring with that available?

[Robbo]

Well OK, clearly the longer you want to go between charges, the larger a battery bank you need. But with an 800-1000W solar array and daily power usage of 300Ah, wouldn't the OP effectively be fully recharging pretty much every every day for maybe six months of the year, and needing a top-up from the generator maybe once a week during another three, and only needing to run the generator every day or two in the depths of winter? Which would suggest to me that in terms of planning his boat, the balance tips away from a large bank and towards a smaller bank that's more frequently charged.

In perfect conditions the 1000 watt solar will be putting out around 40amp at 24v, you'll need over 7-8 hours of this to get replace the ah's used. This doesn't include charging losses and only bulk charging calculations! so no 1000watt is no where near enough!

[dmr]

For many liveaboards running the engine every day in winter to charge batteries is a necessary evil. I have met a fair few boaters whos routine is an engine run every morning and every evening.

 

However the capacity still needs to be well over twice the daily amp-hour consumption. Batteries are not charged to 100% most days, just to whatever can be achieved in perhaps 2 hours. In cold winter weather the battery capacity will be significantly reduced, and just prior to the occasional equalisation there will be capacity lost due to sulphation. As the batteries age their capacity will reduce , 80% is often considered end of life in professional installations but I suspect most boaters would not replace batteries till they are down below 60%.

So.... even for daily charging the bank really should be at least 4 times the expected the daily consumption. This has the bonus that when everything is going well it should be possible to go an extra day without an engine run.

 

..............Dave

 

edited to correct a silly mistake due to fuddled brain from partying last night

Edited January 29, 2017 by dmr

[Robbo]

A charger giving 500A at 24V would draw more than 50A from the mains. Where is the OP going to find a mooring with that available?

13Kw generator?

[MtB]

A charger giving 500A at 24V would draw more than 50A from the mains. Where is the OP going to find a mooring with that available?

 

 

Exactly. I was imagining a three phase diesel genset being required, costing perhaps £10k+

[Ally]

Toilet - yes but haven't a clue (yet) on which is best or what is what. We had a clever chemical jobbie that rotated around to save space in the motorhome. Thinking along the lines of pump out with portable pump-out kit as expecting to be away from amenities for several days at a time. The machinators look good on youtube but I'm not expecting to put anything apart from the usual down (though my phone does have a habit of throwing itself in), so not sure they are worth the money (for me anyway). Starting to settle along the lines of a 3.5VA inverter a nice cocooned genny and a bank of 6 200Ah batteries (type yet to be decided), with 800-1000W solar, depending what will fit. Now I have no idea how much space that will take up but quite a bit I would imagine, so clever storage is going to be very high on the list.

 

Now paint - excuse my ignorance but why not spray the blacking (I had to look up what 2 pack was)?

I really meant the cabin to be coach painted instead of sprayed for a better lasting job.

[mross]

What does a 24v 300A WhisperPower cost?

[cuthound]

Exactly. I was imagining a three phase diesel genset being required, costing perhaps £10k+

Commercial 3 phase gen set is about £1000 per kW.

 

Edited to remove a spurious h from kWh.

Edited January 30, 2017 by cuthound

[magictime]

In perfect conditions the 1000 watt solar will be putting out around 40amp at 24v, you'll need over 7-8 hours of this to get replace the ah's used. This doesn't include charging losses and only bulk charging calculations! so no 1000watt is no where near enough!

 

I've lost track somewhere along the way... where's the assumption of 24V rather than 12V come from?

[Robbo]

I've lost track somewhere along the way... where's the assumption of 24V rather than 12V come from?

Quickly going over the thread I don't believe JJPHG has confirm if his power audit figures were for 24v or 12v, however we have been talking a lot in 24v and he his has not corrected us on the voltage. JJPHG?

Edited January 29, 2017 by Robbo

[magictime]

Quickly going over the thread I don't believe JJPHG has confirm if his power audit figures were for 24v or 12v, however we have been talking a lot in 24v and he his has not corrected us on the voltage. JJPHG?

 

I've just naturally been working in 12V (maybe partly because JJPHG made reference early on to having done a lot of 12V living in motorhomes etc.). And I suppose partly I just can't help thinking that, putting voltage and current on one side for a moment, a solar array generating c. 4kWh of power a day surely couldn't fall that far short of meeting the OP's power requirements!

[mross]

Isn't the consensus here that 24V is the better option at initial fit out?

[Robbo]

 

I've just naturally been working in 12V (maybe partly because JJPHG made reference early on to having done a lot of 12V living in motorhomes etc.). And I suppose partly I just can't help thinking that, putting voltage and current on one side for a moment, a solar array generating c. 4kWh of power a day surely couldn't fall that far short of meeting the OP's power requirements!

However even 1000watt to provide 300ah per day at 12v could only really be done on the best summer days but it will provide the majority or near enough all during summer, but use of the genny will be needed for around 9 months of the year.

Isn't the consensus here that 24V is the better option at initial fit out?

Especially if your going to have some high amp charging equipment.

[MtB]

Commercial 3 phase gen set is about £1000 per kWh.

 

 

Eh? What sort of unit is THAT supposed to be for a generator??!!!

 

Anyway the discussion veered off on this tack when mross said them £4k 12v batteries can be charged at 500A. I said the gear to charge 12V at 500A would cost about £10k. No-one has come up with a more accurate figure yet.

 

 

 

I've lost track somewhere along the way... where's the assumption of 24V rather than 12V come from?

 

 

I'm pretty certain the OP stated this fairly early in the thread when 650AH/day was first questioned. He said he used 24v as motorhomes in Oz use 24v almost universally. CBA to trawl back and find it though...

Edited January 29, 2017 by Mike the Boilerman