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A different approach to solar and batts etc


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Ok, I KNOW, some of my fans are going to want to smash me over the head with a windlass when they hear what I've done, but , such is life smile.png

 

 

We have an interesting mix of people on our boat. Oldies (me and the missus). Teenager (read alien person with own set of strange habits and requirements) . Other Kids.(2). Electricity has always (for years) been a hot topic. We have always done ok, one way or the other, and recently invested in 920W of solar power, wired through 2 MPPT controllers, into 6 batteries. (7 actually because I discovered that the old one I was using as a door stop was measuring 11.9 on it, so I figure a bit of solar will heal it, so I've connected it to the bank as an extra smile.png

 

The thing with electricity, is....when you read the gauge showing the battery voltage, and it starts dropping, my habit has been to shout..."shutdown the PS33333333......get off your PC!!!! etc, in a wild bid to try and save what little power the batteries have left.

 

Unfortunately, since we work/live aboard, by the time the teenager arrives back from college with loads of homework to do, and wants to power up the desktop PC, I've been a little over the top, telling him...."you've got 1 hour!....and then when he's in the middle of his creative flow, I come along and say....Save your work....shut down...time up!".

 

I could see the pain in his eyes when he told me....he was frustrated....understandably. (as a side note, let me say he's complete motivated to do his best at College, and was chosen as a representative to take part in a competition in London a week ago, which he came second in, losing 1st place by a few marks.).

 

So....something has to change, I thought....and out came the paper and pen, so I could design a new system which would work better for him.

 

This is the solution I've been using for 2 days now.

 

1. I split the battery bank up into 2 banks.

2. I connected the one MPPT controller to Bank A.

3. I connected the 2nd MPPT controller to Bank B.

4. I have an isolator switch between Bank A and Bank B so I can join the banks when I want

5. I connected a 600Watt old invertor to Bank A. I ran an extension cable to the Teens room.

6. I connected a 3000Watt invertor to Bank B. It powers the rest of the boat.

7. During the day, solar charges up Bank A. When he arrives back in the evening, he has full batteries to power his desktop PC, so he can work on projects, play games, charge IPad etc.

8. During the day, the rest of us run the TV, laptops, fridge, PS3 etc . At night, the fridge goes off.

 

Last night the Teen spent 5 hours on his desktop PC doing college work. Today his batteries (Bank A) are full again by 2pm.

 

Bank B's batteries started the day at 12.2V, and have been receiving about 10A - 20A from solar all day. That will be ample to keep everything the rest of us need running till late into the night.

 

 

When I run the boat engine (cruising), I'll connect both banks together via the isolator, and both banks will get a nice charge.

 

The ONLY downside I can currently see in this way of doing it, is that ...today...at 3pm, the Teens batter bank A is telling it's solar controller "I'm FULL...dont give me any more current", while the other battery bank B is telling it's solar controller..."I want more"....and getting 20Amps in good sun. So of course, my next step will be to fit a switch so that if one battery bank IS full, I can connect the full 920W of solar all to the empty bank. (rather than losing the sun power).

 

I dont care about Peukerts Law. smile.png

Yes, the Teen does share his battery bank with his brothers smile.png

Yes, I can now wipe my hands clean of managing the Teens power needs....he has become acquainted with a multimeter and runs to measure HIS battery bank voltage about 10 times a night. (fun to watch).

 

It's 12.4!!!!!!! he shouts..... as I continue watching the telly with a grin on my face......

 

Solar is marvelous.

Edited by DeanS
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I like it Dean...

 

Seems to be a good solution to your particular needs

And teens are much less stroppy when they have power available LOL

 

Cheers

Andy

 

Yes, but shhhHHHH.....I just switched the banks together to steal some of his power :)

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Does sound a bit complicated, why not get a combo meter that measures Ah, something like:

 

http://www.ebay.co.uk/itm/DC-120V-500A-Volt-Amp-Combo-Meter-Battery-Charge-Discharge-Indicator-Shunt-/181137158158

 

You could give the teens their own dedicated inverter, connect the Ah meter and say:

 

'Look you've got up to 150Ah to use as you like, then it's lights out til tomorrow!!!'

 

Or just use the Ah meter to monitor the whole boat, easier than a voltmeter. All I'd do is look at the batt voltage first thing, look how many Ah used since the last charge, then after charging reset it and use that number as a baseline. Should decrease any 'range anxiety' considerably.

 

Or get a Smartguage...?

 

cheers, Pete.

~smpt~

Edited by smileypete
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Does sound a bit complicated,

 

ooo no...it's marvelous.........simple enough for all involved.

 

I was hopping around the galley today shouting....we're getting 25Amps!!!!!!!!!!!!!!!!! (and that was one controller output...so it would have been 50Amphour for both....so at least I know on good days, there's a lot up there.

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I think Julian/Loddon has, maybe send a pm.

 

There's a bit of discussion of them here and there, should be able to find a linky to the manual:

 

http://endless-sphere.com/forums/viewtopic.php?f=14&t=40434

 

There's also the Nasa BM2, but only goes to 200A:

 

http://www.amazon.co.uk/Nasa-Bm2-12-Battery-Monitor-12Vdc/dp/B0088YDHS2

 

cheers, Pete.

~smpt~

Edited by smileypete
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yes I have one and it works well for the price.

However setting it up is right royal PITA you do need to know what you are doing!

you will need a decent volt meter and amp clamp and if you don't get it right it will read rubbish.

 

I have written a basic set of instructions in English as to how to set it up

 

http://db.tt/R4LiBD1N

 

other than that its fine.

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However setting it up is right royal PITA you do need to know what you are doing!

 

 

No prob. My Teen son can join the forum and ask you lot how he should install it on HIS bank of batts. My bank is fine thanks...tv works ok.

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Google 'Voltage Sensitive Relay'. You can use one of these between the two banks instead of a manual switch. Then, when Bank A is fully charged the relay will open, charging Bank B and maximising your panel output.

 

These relays will close again if one bank begins to discharge the other too much.

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Google 'Voltage Sensitive Relay'. You can use one of these between the two banks instead of a manual switch. Then, when Bank A is fully charged the relay will open, charging Bank B and maximising your panel output.

 

These relays will close again if one bank begins to discharge the other too much.

 

Thanks for that. Very interesting...but...

 

it says it cuts in at 13.7V and cuts out at 12.8V .

When the sun is out and solar is feeding Bank A, it will be at 13.7V almost instantly....due to the output from the MPPT controller...which would then trick the relay into activating...which would be bad I think. Likewise when an alternator is running, it would feed 14.5V instantly to BankA...and the relay would activate....which would be bad.

 

I think my logics right.

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Dean, I know you don't care about Mr Peukert but one advantage he provides is now you have split the banks, when you connect them together you will more than double your total capacity! All you need to do is erase from your mind the fact that you reduced your total capacity in the first place! That way you feel like you have beaten the system!

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Why not just not worry about it, and get some proper semi traction batts from the likes of Trojan, US Battery, when the existing are nearly kaput. Provided they're charged and equalized well enough they should stand heavy use quite well.

 

Do you really neeeeed a desktop PC though, a cheap secondhand Core2Duo laptop, £100ish?, should do most things well enough.

 

cheers, Pete.

~smpt~

Edited by smileypete
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The desktop, surprisingly, only uses 10AH.

The laptop 7AH

It's not that much more.

 

Chris...I know...I swear I'm going to cut the wire to the display...but I think you told me to get one in the first place :)

 

One thing I have discovered....it's almost impossible to keep a fridge running 24x7 on 3 batteries alone.

 

I drilled holes in the floor today, and fitted a computer fan to blow cold air up the back of the fridge. I moved the fridge too....it had the compressor facing our coal stove, and we've been using that a lot to dry clothes at times...so I suspect the fridge has been chewing amps.



Well, there has to be a first sometime...

 

Richard

yes I know...but is this the time?



Dean, I know you don't care about Mr Peukert but one advantage he provides is now you have split the banks, when you connect them together you will more than double your total capacity! All you need to do is erase from your mind the fact that you reduced your total capacity in the first place! That way you feel like you have beaten the system!

 

erased.

I've beaten the system !!!

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The desktop, surprisingly, only uses 10AH.

The laptop 7AH

It's not that much more.

 

Lappy sounds quite high, I take it you mean 7A through the inverter which is ~84 watts in total. Get a 12V laptop adapter from the likes of Maplins or Ebay and you should see the current fall by up to half that, which will make it a third of what the desktop uses.

 

Chris...I know...I swear I'm going to cut the wire to the display...but I think you told me to get one in the first place smile.png

 

Dean! No one said to watch it all the time! smile.png

 

Just check it first thing in the morning, see what it says. OK it won't tell you everything but it's a hell of a lot better than nothing, and so for £5-£10 is money well spent.

 

To monitor SoC in real time in a nice easy way, get a Smartguage. Or as a halfway house get something that measures Ah like a Nasa BM2 or the meter above.

 

Seems you like thinking big, but sometimes it's also good to think ahead, or think of the smaller things, like how the lappy is run, and how the mains frig is set up, stuff like that it all makes a difference.

 

At least you have some sort of ammeter now, otherwise you'd have no idea what anything uses. ohmy.png

 

yes I have one and it works well for the price.

However setting it up is right royal PITA you do need to know what you are doing!

you will need a decent volt meter and amp clamp and if you don't get it right it will read rubbish.

 

I have written a basic set of instructions in English as to how to set it up

 

http://db.tt/R4LiBD1N

 

other than that its fine.

 

Sounds good does it measure amps/Ah in and out when it's working in '2 wire mode' ie without a separate supply?

 

cheers, Pete.

~smpt~

Edited by smileypete
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Sounds good does it measure amps/Ah in and out when it's working in '2 wire mode' ie without a separate supply?

 

cheers, Pete.

~smpt~

mine is rigged with 4 wires

2 from the shunt

and + and - dc that supplies both the volt meter and the supply

it measures

amps in

amps out

volts

soc %

remaining ah in battery

watts being used

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mine is rigged with 4 wires

2 from the shunt

and + and - dc that supplies both the volt meter and the supply

it measures

amps in

amps out

volts

soc %

remaining ah in battery

watts being used

 

Sounds good, didn't know it did SoC too.

 

So when more than 100% of the Ah reading is put back into the batts, does the Ah stay at zero or does it count past zero into a negative number? I'd expect the SoC stays at 100% in either case.

 

Pete. Dean will be even more confused about units if you refer to Amps per Amp Hour!!

Oh I just meant amps OR amp hours. :)

 

cheers, Pete.

~smpt~

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