Measuring Amps - for Liveaboards :)

[DeanS]

Ummmm I'm confused, you've counted the fridge twice and you've counted "laptop" twice (2 different laptops?)

 

Also, the correct unit for the numbers on the right hand side and the total, is Amp hours.

 

If you've missed electrical items (lights, pumps etc) out then its not a total....its a subtotal. Make a guess of these, and you're 90% there to getting your power audit done.

 

the fridge is on its lonesome for 8hrs.

the fridge and laptop run together for 16hrs

Yes 2nd laptop

Reason I didnt add the lights/pumps etc..is they are small in comparison...so not bothered with them

 

What if the sun doesnt come out. lol.

 

 

 

I have 2 x 100w solar panels with a mppt controller to each one, works great during the sunny days and we are power hungry too. We are getting around 10 amps per hour from both on a good sunny day. When the suns gone in its time for the engine lol. 3 years onboard, 4500 hours on the engine in the 3 years and solar for 2 and a half years. We did have some charging issues though which we have had sorted now, fuel per month is around £60-£80 a month now based on 94p per litre using about 1 and a half litres per hour, and some genny use but not much. hope this helps, i would recommend solar though, they worth it.

 

I hate the fridge so i fitted 2 computer fans underneath it to help stop it coming on all the time.

 

Very helpful thanks....!

[nicknorman]

 

Yep..I've always looked at solar slightly cautiously. Our daily usage is approx 210Amps per day. Thats based on:

 

Fridge on by itself - 2Amps@8hrs = 16Amps

Fridge and laptop - 10Amps @16hrs = 160Amps

PS3 - 6Amps@4hrs = 24Amps

IPAD,TV,Laptop - 5Amps@2hrs = 10Amps

 

Total = 210Amps

 

This excludes lights, water pumps etc.

 

I'm supposed to put back 50% more than we use....so I should be putting back 300Amps into the batteries each day. If I cant, I have to cut down on appliances. Not likely. We've been in the boat for a month, and no evidence of the batteries struggling, so the charging regime seems to be working, except it's costing in diesel. ..and a bit of engine noise. (need to put soundproofing along the one side of the engine wall I think which would improve that). If I can generate half of that using solar, and the rest in a morning engine charge, that would be idylic.

 

ETA - thats the requirements for running a business from a boat, and keeping 3 kids happy in the evenings.

Ok I give up with you and Amps and AH. If I was there I would put you on the norty step for not trying!

 

Anyway, IMO the "put back 50% more than you took out" is a myth. My monitoring gadgetry tells me that my charge efficiency is around 92-94%, that means I have to put back say 8% more than I have taken out. The only time 50% is anywhere near correct is right at the end, to squeeze in the last few AH, but then its 50% of a very small amount.

[nb Innisfree]

Yep..I've always looked at solar slightly cautiously. Our daily usage is approx 210Amps Amphours per day. Thats based on:

 

Fridge on by itself - 2Amps@8hrs = 16Amps Amphours

Fridge and laptop - 10Amps @16hrs = 160Amps Amphours

PS3 - 6Amps@4hrs = 24Amps Amphours

IPAD,TV,Laptop - 5Amps@2hrs = 10Amps Amphours

 

Total = 210Amps Amphours

 

This excludes lights, water pumps etc.

 

I'm supposed to put back 50% more than we use....so I should be putting back 300Amps Amphours into the batteries each day. If I cant, I have to cut down on appliances. Not likely. We've been in the boat for a month, and no evidence of the batteries struggling, so the charging regime seems to be working, except it's costing in diesel. ..and a bit of engine noise. (need to put soundproofing along the one side of the engine wall I think which would improve that). If I can generate half of that using solar, and the rest in a morning engine charge, that would be idylic.

 

ETA - thats the requirements for running a business from a boat, and keeping 3 kids happy in the evenings.

[Paul C]

Lighting isn't an insignificant amount of power! Needs to be included! Pumps, I'll accept, you can put to one side for now.

[DeanS]

If 10Amps flows for 8 hours....is it correct to say it has used 80Amps in an 8 hour period.....

You want me to say it has used 80 AmpHours.

 

I dont get what an AmpHour is.

I understand a battery is x AmpHours, because I can understand it can supply x Amps consistantly in an hour

 

God help me.

 

ETA - from Wikipedia.

 

An ampere-hour is not a unit of energy. In a battery system, for example, accurate calculation of the energy delivered requires integration of the power delivered (product of instantaneous voltage and instantaneous current) over the discharge interval. Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power

 

so if it's not a unit of energy...watsit.

Edited April 23, 2013 by DeanS

[Richard10002]

If 10Amps flows for 8 hours....is it correct to say it has used 80Amps in an 8 hour period.....

You want me to say it has used 80 AmpHours.

 

 

.

In Maths I was taught that in this type of calculation, you multiply the digits and you multiply the units

 

e.g.

 

10mph for 8 hours 10x8=80. Miles per hour x hours = miles NB. Mph is the same as m/h so m/h x h =m

 

thus 80miles

 

10amps for 8 hours. 10x8=80. Amps x hours =amphours

 

Thus 80amp hours

 

Not sure if that helps or confuses?

[nicknorman]

If 10Amps flows for 8 hours....is it correct to say it has used 80Amps in an 8 hour period.....No

You want me to say it has used 80 AmpHours. Yes!

 

I dont get what an AmpHour is. Its a quantity of electrical charge - or a pot of electrons if you like, like some water in your tank.

I understand a battery is x AmpHours, because I can understand it can supply x Amps consistantly in an hour Nearly, but not precisely because nomally AH is quoted at a slower discharge rate. Due to the chemistry and losses, if you discharge it over an hour you will get less out of it because you are discharging it too fast.

 

God help me. You need him!

 

ETA - from Wikipedia.

 

An ampere-hour is not a unit of energy. In a battery system, for example, accurate calculation of the energy delivered requires integration of the power delivered (product of instantaneous voltage and instantaneous current) over the discharge interval. Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power

 

so if it's not a unit of energy...watsit.

Dean are you on the sauce tonight?

 

An Amphour is a unit of electrical charge. Using my water analogy, its the volume of water in the tank, or the volume of water in the bucket after you let some run out of the tank. It is not a unit of energy as you say. To get energy out of water, you have to carry it up a hill and then let it run down a hill in a stream and operate a water wheel. Same with Amphours, you need something to move them in order to get energy, and that is voltage. So lots of amphours stored in a battery is stored with voltage, the voltage is just desperate to push the amphours out as soon as you connect a circuit. That's why 100AH in a 12v battery is only worth half as much energy as 100AH in a 24 volt battery.

[nb Innisfree]

It's a way of expressing power usage, instead of amphours you could use watts which is a true expression, multiply amps by whatever voltage you are using and you finish up with watt hours or kilowatt hours. If I say I am using 70ah per day I have to add that it is 24v to make it clear, instead it would be better if I said it was 1650 watt hours or 1.65 kwh, (24x70) a true measure of power used, but many folks wouldn't understand. I have a 24volt 100amp alternator but when I say I have a 2.4 kw alternator it's assumed by some, incorrectly, that it's a 240 volt unit.

 

You can't win.

[DeanS]

In Maths I was taught that in this type of calculation, you multiply the digits and you multiply the units

e.g.

10mph for 8 hours 10x8=80. Miles per hour x hours = miles NB. Mph is the same as m/h so m/h x h =m

thus 80miles

10amps for 8 hours. 10x8=80. Amps x hours =amphours

Thus 80amp hours

Not sure if that helps or confuses?

 

No.

An Amp is a symbol of current flow.

An hour is a symbol for duration of time.

You cant just make up a new word called an AmpHour and expect me to understand what it is....LOL...

 

A litre is a symbol of liquid flow

A degree is a symbol of temperature.

Lets just make a new word...".litredegree " . Simples

[Richard10002]

 

 

No.

An Amp is a symbol of current flow.

An hour is a symbol for duration of time.

You cant just make up a new word called an AmpHour and expect me to understand what it is....LOL...

 

 

OK sometimes you just have to accept that what is, is

 

1 amp flowing for 1 hour is 1 amphour - because it is!

 

It isnt a new word, it's been around for a long time.

 

A litre can't flow for a degree, so you can't have a litredegree.

 

I guess amphours are a bit like volumes of power, in the same way that litres, or gallons etc. are volumes of liquid. Perhaps they are stores of stuff and, when used, the stores are drained of the stuff.

 

As I said, it's not easy, and not simple, and sometimes you just have to have some faith and accept.

[Paul C]

Amps is a "flowrate" - ie a rate of flow

 

Rate of something, is something per unit time.

 

The something in this case, is the amp-hour.

 

So an amp is an amp-hour per hour.

[Naughty Cal]

Dean.

 

I think you either need to find a way of cutting down your power useage or accept that you are going to have to run your engine for a long time each day to keep up with your consumption. A solar panel will help but it isnt a magic wand. If it supplies 30 amps to the batteries on a sunny day that is only 15% of what you claim to be using per day (Based on your estimates) which still means you have a long time of running your engine to even put back what you have used. Plus bear in mind that whilst you are running the engine to charge the batteries you are still consuming power as well so it isnt all going into the batteries.

 

I would budget for changing your batteries on a regular basis because they wont last long with that sort of abuse!!

[DeanS]

few things.

1. I now understand amp hours.

2. I'm going to install 2 computer fans under the fridge to stop it coming on all the time.

3. I'm going to take a loan holiday on my bank loan, and use the money to buy around 6 solar panels plus MPPT controller.

4. In winter I'm in a marina.

5. I'll cruise in the afternoons/evenings through summer. The daylight is out till 8:30pm at the moment.

6. Sunday is gennie day on a towpath somewhere for washing machine.

 

Hows that sound

[Paul C]

DeanS, just reviewing the figures I think you might have estimated laptop #1 too high. If the fridge alone draws 2A and the fridge + laptop#1 10A, then that means its continuously drawing 8A for 16 hours. It may well draw 8A for periods of intense activity + charging its internal battery, but a) once that internal battery is charged the current will drop off and b ) I'll assume you aren't using it intensively all 16 hours (you mentioned you actually go cruising and see things etc?)

 

Mine draws 4A, during charging the battery, for example.

 

I think an amp-hour counter might be a good investment, to accurately gauge the power you're using.

 

For example: http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/

Edited April 24, 2013 by Paul C

[DeanS]

Out of interest.

 

Starting the boat engine this morning, showed the alternator pushing out 150 amphour ( )

The demand from the invertor is 5 amphour

 

The fridge and laptop are on. So the reading of 10amphour yesterday for fridge and laptop was at the high end, probably because the fridge was working overtime. So...instead of 160Amps needed, if I can reduce the fridge requirements, it'll knock off half of that per day, which is a substantial savings.

 

 

ETA...the laptop battery is stuffed, but we've ordered a new one, which will reduce the fridge/batt value even more. Being the main big demanders for constant power, my earlier stats should improve.....so in reality I'm probably needing around 150Amps per day in the long term. ( a quick thumbsuck)

Edited April 24, 2013 by DeanS

[nicknorman]

Starting the boat engine this morning, showed the alternator pushing out 150 amphour ( )

The demand from the invertor is 5 amphour

You're a very naughty boy!

[DeanS]

sorry:)

 

Just checked again. Morning engine run.

 

It's been running for 30mins.

The alternator has dropped from the previous value of 150 AMPS to 50AMPS

 

The demand on the invertor however, has crept up from 5AMPS to 10AMPS again. I assume it's the fridge as nothing has changed in the past 30mins. laptopwise.

[smileypete]

few things.

 

1. I now understand amp hours.

2. I'm going to install 2 computer fans under the fridge to stop it coming on all the time.

3. I'm going to take a loan holiday on my bank loan, and use the money to buy around 6 solar panels plus MPPT controller.

4. In winter I'm in a marina.

5. I'll cruise in the afternoons/evenings through summer. The daylight is out till 8:30pm at the moment.

6. Sunday is gennie day on a towpath somewhere for washing machine.

 

Hows that sound

 

Maybe it'd be good to buy one or two solar panels and see how it goes. These work out at 75p/watt delivered for new panels, slim chance of doing better these days unless you collect and or haggle a deal:

 

http://www.ebay.co.uk/itm/Solar-Panels-Ideal-Thermasol-TSPV-200-PE-Solar-PV-Collectors-200W-/271122529531

 

Direct to the batt or via a cheap 20A PWM they should each give approx 7.5 amps tilted towards full sun, 5 amps flat on the roof in full sun, and possibly 3 to 4 amps on bright but overcast day.

 

But once you add a £140 30A Tracer MPPT which can handle up to 2 such panels, or a £95 20A Tracer for one panel, each should give approx 13.5 amps tilted toward the sun, 9.5amps flat on roof in full sun, and possibly 5 to 7 amps on a bright but cloudy day.

 

ETA If you'd like to get the panels and MPPT at the same time, and don't mind second hand panels, you could get a couple of 170W panels and a 20A Tracer MPPT from here for about £285 all in:

 

http://www.bimblesolar.com/index.php

 

Or maybe spend the extra £40 for a 30A MPPT so you can add another panel later.

 

BTW did you get a chance to see what the batt voltage was first thing this morning?

 

cheers, Pete.

~smpt~

Edited April 24, 2013 by smileypete

[bizzard]

Install a s/h gas fridge Dean and save yourself thousands of pounds in the long run. It would also give everyones ears a rest.

[DeanS]

Install a s/h gas fridge Dean and save yourself thousands of pounds in the long run. It would also give everyones ears a rest.

 

Dont be rude This is my little thread As far as I know, some people are actually quite interested in the trevailings of a liveaboard family with a high elec demand. Like I said, on the old boat, we spent a year onboard without the lights going out once in 365 days. We had tvs on, laptops on, XBox on... I've seen people on this forum having trouble just keeping their lights from going dim. I then moved into a marina, and now that winters over, I'm back off the shorepower. It's only been a month, but again, I have no problems with power at the moment. None. at all. BUT......I dont want to spend as much on fuel, I'd like to limit the engine running hours, and a gas fridge is a lot smaller than a 220V fridge.

 

Would you like some earplugs

[Naughty Cal]

Dont be rude This is my little thread As far as I know, some people are actually quite interested in the trevailings of a liveaboard family with a high elec demand. Like I said, on the old boat, we spent a year onboard without the lights going out once in 365 days. We had tvs on, laptops on, XBox on... I've seen people on this forum having trouble just keeping their lights from going dim. I then moved into a marina, and now that winters over, I'm back off the shorepower. It's only been a month, but again, I have no problems with power at the moment. None. at all. BUT......I dont want to spend as much on fuel, I'd like to limit the engine running hours, and a gas fridge is a lot smaller than a 220V fridge.

 

Would you like some earplugs

I think he was refering to your engine running and genny running requirements

[bizzard]

Dont be rude This is my little thread As far as I know, some people are actually quite interested in the trevailings of a liveaboard family with a high elec demand. Like I said, on the old boat, we spent a year onboard without the lights going out once in 365 days. We had tvs on, laptops on, XBox on... I've seen people on this forum having trouble just keeping their lights from going dim. I then moved into a marina, and now that winters over, I'm back off the shorepower. It's only been a month, but again, I have no problems with power at the moment. None. at all. BUT......I dont want to spend as much on fuel, I'd like to limit the engine running hours, and a gas fridge is a lot smaller than a 220V fridge.

 

Would you like some earplugs

Sowwy Yes but did you have an electric fridge on the other boat? Thankfully I'm about 200 miles away from you, so don't need em thanks.

[DeanS]

Maybe it'd be good to buy one or two solar panels and see how it goes. These work out at 75p/watt delivered for new panels, slim chance of doing better these days unless you collect and or haggle a deal:

 

http://www.ebay.co.uk/itm/Solar-Panels-Ideal-Thermasol-TSPV-200-PE-Solar-PV-Collectors-200W-/271122529531

These seem a good price. 200Watts....@ £139. What is the difference between mono, multi, type solar panels.....I think I heard that mono are better? I know nothing.

 

ps...the battery voltage this morning was 12.1V

 

 

I think he was refering to your engine running and genny running requirements

oops....SORRY BIZZARD...LOL.

 

Sowwy Yes but did you have an electric fridge on the other boat? Thankfully I'm about 200 miles away from you, so don't need em thanks.

 

Nope. Last boat was a gas fridge. Was great, but not ideal for a large family. Leaving the marina we've already switched off the microwave, dishwasher, freezer, ....not going to tell wife we need a smaller fridge.

[bizzard]

These seem a good price. 200Watts....@ £139. What is the difference between mono, multi, type solar panels.....I think I heard that mono are better? I know nothing.

 

ps...the battery voltage this morning was 12.1V

 

 

oops....SORRY BIZZARD...LOL.

I was only trying to help you. Why a few days ago you said you only had ten quid in the bank.

Edited April 24, 2013 by bizzard

[Naughty Cal]

These seem a good price. 200Watts....@ £139. What is the difference between mono, multi, type solar panels.....I think I heard that mono are better? I know nothing.

 

ps...the battery voltage this morning was 12.1V

 

 

oops....SORRY BIZZARD...LOL.

 

 

Nope. Last boat was a gas fridge. Was great, but not ideal for a large family. Leaving the marina we've already switched off the microwave, dishwasher, freezer, ....not going to tell wife we need a smaller fridge.

For you Dean

 

 

 

So at 12.1V in the morning your batteries have somewhere between 35 and 40% capacity left and are ready for a good charge, not just an hour here or there.

Edited April 24, 2013 by Naughty Cal