24 VOLT ENERGY AUDIT

[Horatio Sprague]

I have just done an Energy Audit for my new narrowboat which will have a 24 volt system. This indicates a daily consumption of around 80 amp/hours at 24 volts. How many 12 volt 110 amp batteries would I need wired together (to give 24 volts) to provide this power? Would it be 2 pairs of 2 batteries wired in series?? Any help appreciated!

[cuthound]

2 pairs of 2 x 12 volt 110Ah batteries would give a total capacity of 220Ah, which is in my opinion a bit marginal for an 80Ah consumption, as you shouldn't discharge the batteries below around 50% if you want them to last, particularly if you intend to liveaboard and CC.

Personally I would go for a minimum of 4 pairs of 2 x 12 volt 110Ah batteries would give a total capacity of 440Ah.

How do you intend to charge them?

Edited November 3, 2017 by cuthound
Spillung

[WotEver]

3 pairs would be the minimum really. 4 pairs better, as Cuthound suggests. 

[Alan de Enfield]

9 minutes ago, Horatio Sprague said:

I have just done an Energy Audit for my new narrowboat which will have a 24 volt system. This indicates a daily consumption of around 80 amp/hours at 24 volts. How many 12 volt 110 amp batteries would I need wired together (to give 24 volts) to provide this power? Would it be 2 pairs of 2 batteries wired in series?? Any help appreciated!

That is very high – that’s equivalent to 160Ah at 12v

(As a comparison I use, on average, approx 100-120Ah per day with 220v Freezer, 220v Twin-Tub washing machine, 220v microwave, 12v Fridge,12v TV, lights, water pumps, 2x Computers, 2x phone charging.

I have 1300Ah battery bank, giving me about 6 days ‘storage’)

Recommendation is normally that you should have a battery bank of a minimum of 3x daily usage. This will mean that you have 1.5 days of usage before you MUST recharge your batteries, a battery bank of 6 times daily usage will give you 3 days usage before recharging – the next question is how do you intend to get 100Ah (at 24v) per day back into your batteries. Purely as a guesstimate that would be 4 hours + per day (or 8 hours every 2 days) of engine running with a 100Ah 24v alternator

A battery bank of about 800-1000Ah (8-10 x 110Ah batteries) would not be unreasonable to minimise battery drain

Only you know how you will use your boat - will you be cruising 5 hours very day ?

Will you tie up and not move for a few days?

Will you have solar ? how much ?

Will you have a generator ?

Will you be on a mooring with a land-line?

 

[nicknorman]

58 minutes ago, Horatio Sprague said:

I have just done an Energy Audit for my new narrowboat which will have a 24 volt system. This indicates a daily consumption of around 80 amp/hours at 24 volts. How many 12 volt 110 amp batteries would I need wired together (to give 24 volts) to provide this power? Would it be 2 pairs of 2 batteries wired in series?? Any help appreciated!

It also depends a bit on how you intend to use the boat. If it’s primarily a leisure / cruising boat, then some of that 80 AH will be used when the boat is cruising and so the batteries need to supply less than 80AH. In which case, probably 4 batteries is OK. But if it will be static quite a bit, then I’d say 6 batteries. 8 batteries seems overkill to me, and will require a lot of space.

[Horatio Sprague]

Thanks for your replies on this. It might help if I showed you my energy audit workings to see if I have got it right! The actual set up will have a 100amp 230V TravelPower option on the Beta 43 engine in addition to the 24V domestic alternator. I also plan a Victron Phoenix Inverter and a 200 Watt flexible solar charging kit. Boat will be used for continuous cruising.

ITEM	LOAD IN	TOTAL	TIME IN	AUDIT IN
	AMPS	AMPS	HOURS	AMP HOURS
22 NO 1.3 WATT LED LIGHTS	0.06	1.32	6	7.92
2 NO LED READING LIGHTS	0.07	0.14	2	0.28
2 NO FLUO GALLEY LIGHTS	1.3	2.6	2	5.2
2 NO BULKHEAD LIGHTS	1.3	2.6	1	2.6
1 NO 42 WATT TUNNEL LIGHT	1.6	1.6	1	1.6
WATER PUMP	2.2	2.2	1	2.2
SHOWER PUMP	1.6	1.6	1	1.6
DIESEL HEATER	1.5	1.5	6	9
FRIDGE	1.9	1.9	12	22.8
TV	1.9	1.9	4	7.6
TOILET	10	10	1	10
			TOTAL	70.8
BATTERY CAPACITY REQUIRED			A/H X 3	212.4

[cuthound]

29 minutes ago, nicknorman said:

It also depends a bit on how you intend to use the boat. If it’s primarily a leisure / cruising boat, then some of that 80 AH will be used when the boat is cruising and so the batteries need to supply less than 80AH. In which case, probably 4 batteries is OK. But if it will be static quite a bit, then I’d say 6 batteries. 8 batteries seems overkill to me, and will require a lot of space.

That is one the the problems that is rarely mentioned when going for a 24 volt system. You need twice as much space for batteries if a given battery capacity in Ah. (Although the Wh's will be doubled with the increase in voltage from 12 to 24).

8 batteries at 24 volts only gives 440Ah which for a liveabord is probably a realistic minimum.

Leisure users can get away with less capacity unless they have a high energy consumption like you. Don't you have 450Ah batteries for leisure use?

Edited November 3, 2017 by cuthound
Clarification

[ditchcrawler]

Well you are unlikely to want 22 lights on all evening, we normally have 6 in the lounge and then Galley, toilet as required. If the TV is on then no lights at all. Our show pump probably runs for 5 minutes a day, 10 at the outside. How long is a toilet flush, 1 minute ? The tunnel light is only on while the engine is running so not taking anything from the battery.

[Horatio Sprague]

Thanks Ditch Crawler....I agree with the usage. I have deliberately overestimated many of the figures, so it looks like I'm coming down to about 6no. 12V batteries wired for 24V!

[WotEver]

44 minutes ago, Horatio Sprague said:

Thanks Ditch Crawler....I agree with the usage. I have deliberately overestimated many of the figures, so it looks like I'm coming down to about 6no. 12V batteries wired for 24V!

I’d say so. 

As previously asked, how are you going to generate your 70Ah (or whatever) daily?

That’s more relevant than how many batteries really. 

[nicknorman]

51 minutes ago, cuthound said:

That is one the the problems that is rarely mentioned when going for a 24 volt system. You need twice as much space for batteries if a given battery capacity in Ah. (Although the Wh's will be doubled with the increase in voltage from 12 to 24).

8 batteries at 24 volts only gives 440Ah which for a liveabord is probably a realistic minimum.

Leisure users can get away with less capacity unless they have a high energy consumption like you. Don't you have 450Ah batteries for leisure use?

Yes but comparing AH without taking into account voltage is meaningless. We have 450AH at 12v which is the same energy as 225AH at 24v.

440AH at 24v is equivalent to 880AH at 12v, which is much more than most people have.

[smileypete]

Maybe get 4x 110Ah leisures (decent brand like Numax, Varta, Banner), but have cabling and space to add another two later if needed.

Travelpower would definitely be handy, also an ammeter like the NASA BM1. Next spring think about a solar setup too.

Edited November 3, 2017 by smileypete

[Horatio Sprague]

Sounds like good advice Smiley Pete!!

[MtB]

2 hours ago, cuthound said:

2 pairs of 2 x 12 volt 110Ah batteries

 

Qué?

Do you mean eight batteries? 

[MtB]

1 hour ago, Horatio Sprague said:

TOILET 10 10 1 10

 

A toilet using 10AH per day???!!!!!!!!!

Mine uses ZERO AH per day!

[nicknorman]

10 minutes ago, Mike the Boilerman said:

 

Qué?

Do you mean eight batteries? 

edited out because MtB is right. Sort of!

Edited November 3, 2017 by nicknorman

[WotEver]

17 minutes ago, Mike the Boilerman said:

 

Qué?

Do you mean eight batteries? 

Awkward pedant

[Onewheeler]

19 hours ago, Mike the Boilerman said:

 

A toilet using 10AH per day???!!!!!!!!!

Cholera?

[Alan de Enfield]

19 hours ago, Mike the Boilerman said:

 

A toilet using 10AH per day???!!!!!!!!!

 

Slash / Splash & Burn ?

Edited November 4, 2017 by Alan de Enfield

[OldGoat]

22 hours ago, Mike the Boilerman said:

 

A toilet using 10AH per day???!!!!!!!!!

Mine uses ZERO AH per day!

I hesitated to ask; assumed a 'flaming' composting type. Don't want to go there...

[MtB]

1 minute ago, OldGoat said:

I hesitated to ask; assumed a 'flaming' composting type. Don't want to go there...

 

I don't mind going there!

I'd overlooked the possibility of a desiccating bog. They need a fan to run 24/7 to stop them stinking the boat out, IIRC. That would explain the 10AH and day! 

[cuthound]

Then there was the post asking about the incinerator toilets.  However I think that consumed something in the order of 100Ah per day or a 13kg gas bottle for the gas fired ones! 

[Dave_P]

I've merged the two duplicate topics and moved it all to the equipment section.  It could have gone in the boat building section, but battery stuff usually goes in equipment.

[nb Innisfree]

When I designed Innisfree I decided to place batteries across the beam and found 8 batteries fitted so I went with that. Coupled with a 24v 100amp alternator it all proved effective and able to comfortably supply us with 70 ish ah per day (at 24v)

[Alan de Enfield]

8 minutes ago, nb Innisfree said:

When I designed Innisfree I decided to place batteries across the beam and found 8 batteries fitted so I went with that. Coupled with a 24v 100amp alternator it all proved effective and able to comfortably supply us with 70 ish ah per day (at 24v)

8 x 110ah ?

So, I wasn't far out in post #4 when I said :

A battery bank of about 800-1000Ah* (8-10 x 110Ah batteries) would not be unreasonable to minimise battery drain

* at 12v

 

Edited November 6, 2017 by Alan de Enfield