450 AH vs 675AH charging question

[GILow]

Nice one Brian, but I am gonna pick on you a bit.


What you just described gave us 6 volts if they were all T105s, and unless you are driving an early model Volkswagon 6 volts is not going to be very useful. :^)


Matt

[btrayfors]

Option B??

Sounds kinda like the setup I built with my six 6-volt golf-cart house batteries (Crown Red Top 235AH each).

This is my winter setup in my basement to keep these puppies happy while my boat is on the hard up in Maine.

All charging cables of equal length to each of three pairs.

Works like a charm.

Note: since this is only for storage (float, short absorption, and infrequent equalizing) and involves much lower amperages than on the boat, these cables are AWG6....much smaller than the 1/0 cables on the boat.

These batteries are 2.5 years old now and still test like new (Midtronics MDX-650 tester).



Bill

[El Pinguino]

Righto Matt, what do you plan to do?
Stick with 450 or go to 675?

[GILow]

Originally Posted by El Pinguino

Righto Matt, what do you plan to do?
Stick with 450 or go to 675?

Hi E.P.

Right at the moment I am thinking 675AH. I really do like the idea of shallower depth of discharge. It does appear that I was not understanding the charging issues.

There has just been a frustrating delay while I confirm that the AGM battery bank is actually kaput. The 40 degree days here, combined with work commitments, have prevented me from going down to the boat to do a real test of the battery bank. I may regret this because Jim put me in touch with a guy who had the T105s at an excellent price, and by the time I confirm the demise of the current battery bank that source may have dried up. Frustrating, but oh well.

Matt

[brianlara 3]

MATT Did you see Bills picture. It's easy Matt.
Have a rest and bother me back....bated breathing......
BILL, my boat is tiny and for a long while I got away with 8/0 cable even to the windlass = 900W . But have almost finished running 2/0 even to the bow, the weight of which is something I'd rather not have.
As you know, 8/0 ran the windlass well for five years but two foot black mud has tripped the breaker a couple of times.
Anyway, proper is proper, so 100' of 2/0 later.....a 20lb gas bottle, a 10.....250' x 5/16"..... tiny boat but added mass slows the motion rate from shocking to tolerable when sitting in a sliding/rotating Springfield Ladderback
5% sorry about the drift.

[GILow]

Originally Posted by brianlara 3

MY GOD MATTHEW!!! I feel like calling you.
Mattey, where did you get six volts from??
Matt.....hellloooo.
Matt, most boats run 12 volt batteries, even 24 volt systems run 12 volt batteries....,like you didn't know right.
...

Hope the TV viewing is good.

The Trojan T105s are 6 volts each and are pretty popular with the boating fraternity.

So putting them all in parallel would give me 1350 AH @ 6 volts. That would probably even start a '57 1200cc single carbie VW pancake motor on a cold morning, though we found pushing the darn thing was just easier in the long run. Good exercise to boot. I spent my childhood assuming you push-started cars, I was quite surprised to see my friend's dad start his car from the drivers seat when I was about 7 years old.

I thought it was magic.

Matt

[GILow]

Originally Posted by brianlara 3

MATT Did you see Bills picture. It's easy

Yep, Bill has his batteries paired in series, then in three parallel banks. Pretty much what I expect I will be doing.

Of course I doubt my setup will look quite as neat, but I will try.

Matt

[leftbrainstuff]

Originally Posted by GILow

Hello Cruisers,

I feel like this one has been done to death, but I still can't quite get my head around the charging question.

I have an option of putting in either 4 or 6 Trojan T105 batteries, so either 450 AH @ 12v or 675 AH @ 12 V.

The power consumption of the boat is pretty low. Main items are the Danfoss DB50 fridge compressor, the autopilot, plotter, windlass, pursurvivor 35 watermaker, TV and a few radios, VHF and HF. Lighting is 100% LED. I have been managing fine for weekend overnight sailing on a pair of very cheap 125 AH AGMs and they have never gone below 12.5 volts.

Power production comes from 280 watts of solar connected to a 420 watt capable MPS controller, an Aerogen 6 (300Watt) wind-generator and reasonable quality 100 amp alternator. (Hitachi, so I figure it is good for about 60 - 70 amps in reality, that may be optimistic.) In practice, we are never using the Aerogen or engine driven alternator because the solar panels are keeping the two 125AH batteries full all the time. We never plug into the mains.

Engine electrics are a totally separate 24 volt bank.

The previous owner lived aboard for many years with a 400AH battery bank and felt it was plenty, so I am inclined to think, with the advent of LED which he did not have, that 400 AH will still be plenty. But, I have the space to fit the bigger bank easily enough, so logic says it would be better to have the shallower depth of discharge and go the larger bank.

BUT, do I have enough charging capacity? I see the mention of 10% of battery capacity required for charging current and I realise that as it is, the solar will not be enough to provide that peak current. I could add panels, up to 420 watts, but I would rather not do so if is just to provide charge capability that I don't really need. Would short runs of the engine provide what I need to prevent sulphating from inadequate current or is it good enough to keep the bank fully charged to prevent problems?

Really confused, and I have read lots on C.F. without being any less confused. Can anyone enlighten me?

Matt

Short runs of a diesel is definitely not best practice.

We have 6 trojan t105s. 675 Ahr capacity. We consume approx 80 Ahr / day while on the hook.

We have 280W of heavily shaded solar and a wind gen.

We run the gennie to heat hot water and techarge when solar doesn't keep up.

Our trojans are 8 yrs old and are using lots of water. Typical of aged batts.

Were planning to add up to 720 W of solar. Mainly to heat hot water and reduce the need to run the gennie.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[brianlara 3]

Matt, yep TV, lemon and sugar pancakes, great tea.
Think the beetles were 1100cc. But flat out at 62mph.
Nice post Matt.
Cheers.

[GILow]

Originally Posted by leftbrainstuff

Short runs of a diesel is definitely not best practice.

We have 6 trojan t105s. 675 Ahr capacity. We consume approx 80 Ahr / day while on the hook.

We have 280W of heavily shaded solar and a wind gen.

We run the gennie to heat hot water and techarge when solar doesn't keep up.

Our trojans are 8 yrs old and are using lots of water. Typical of aged batts.

Were planning to add up to 720 W of solar. Mainly to heat hot water and reduce the need to run the gennie.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

Thanks L.B.S., you have, for practical purposes, exactly the same charging setup we have with much the same power consumption, and it sounds like you need the generator.

Bugger!

Er... what sized wind generator please?

So, you run the generator when there is not enough wind or solar... I suppose those two variable are going to be utterly dependent on WHERE on the planet you are at the time... but how often would you say you need to run the generator on average?

Matt

[GILow]

Originally Posted by brianlara 3

Matt, yep TV, lemon and sugar pancakes, great tea.
Think the beetles were 1100cc. But flat out at 62mph.
Nice post Matt.
Cheers.

Our 1200 was in a split windscreen kombi van. Hopelessly underpowered, top speed, on a good day, was a bit under 50mph. We put a 1500 in later, but it blew up when a paper bag got sucked into the cooling air intake.

There's a little red light on the dashboard of the older kombis that comes on to tell the reason you are sitting by the side of the road in a cloud of brown/black smoke is that the engine has overheated. It takes about two minutes, but it is a very helpful light. It might have been hard to figure out what had gone wrong without that light.

A good mate has a 2000 cc later model kombi that goes like stink and sounds like an aeroplane too.

[brianlara 3]

Loved it Matt!
Hope we don't get banned for thread destruction.
When I was an apprentice in a Sydney VW dealership, one of the mechanics, a German, accidentally pup the crown wheel on the wrong side of the pinion when overhauling a Kombi transmission.
Klaus dropped the the wehicle to the floor, jumped in sticking it into reverse and slammed forward into his/our bench...4 reverse ratios and one forward!! Serious at the time but killed us later.
2% sorry for drift.

[GILow]

Originally Posted by brianlara 3

TO WHOM IT MAY CONCERN.

Judge Judy was fantastic today.

Well, at least you found a good use for all those carefully harvested electrons.

[Salty Mike]

I had a VW many years ago...... And dinner last night.... time for breakfast now....

Yes 6x6=36 but that was just a for instance could be 4x4 for a 24 volt starter or whatnot.
Actually I keep thinking one (I) may want to tap off different voltages IE you may need 6v for lighting should you run across a deal on some 6 volt led fixtures or for charging cell phones and what-not, or some if not all laptops use an 18 volt power supply I put a 6v battery in line with my 12v house bat in a motorhome to run a laptop back in the day, we were using the laptop for navigation before we got a Tom Tom, the laptop was better.

The thing I cant stop from pondering is the first battery in line gets the charge first from the charging system, Yes? The last one in line gives up its charge first.No? looks like their end plates first and last respectively take the beating from all them electrons having to pass through them first and would benefit from a rotation.

I know I'm overthinking it and I'm sure if I sat down with two or three bottles of wine and some graph paper I could figure it out but I don't have that much wine right now and I seam to have lost my draft paper and where is my pencil? .... Oh look a squirrel.

[brianlara 3]

Salty, no. There is no first or last in a proper setup.
If my description wasn't clear, just Google, the verb, " twelve volt batteries in parralel" and go to images.
You see diagrams of multiple batts in a row.
A single pos comes from a pos on one side of the set and a single neg cable comes from the opposite five, eg, batteries. These two cables are it.
Salty, sure you weren't playing games with my head ???