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Battery Charging Part 2


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One starting bank of 2 x 12v wired to be a 24V, this charges off the motor.

One house bank of 4 x 12V wired into 2 x 24V, this charges off a big Alternator driven by belts off the shaft, so prop knot spinning means no charging.

 

If I get a set of heavy duty jumper leads can I put them between the starting and one of the house sets to charge all at the same time?

 

Starters isolated immediately on motor shut down so I can start the bugger again. Just thinking of topping up while at anchor rather than having to motor around doing it. Knot a biggie really as the house shaft charger whacks out HUGE so they do seem to come up very quick.

 

And it has some '12V Interface' box thing in it. Knot too sure what exactly that is but are assuming is some jiggery pokery that steps 24V down to 12V as that's what most of the gear is. Or maybe a 240 to 12V? It has 12, 24 and 240V systems.

 

Supplementary question - If the fridge is 24V does than mean it takes only 1/2 as long as a 12V one to chill my beers? :lol: :lol:

 

Supplementary question 2 - Wheels, you and your electrical leaning more than my mind ARE coming for a weekend away. That's knot the question by the way, it's a reality :)

The question is what beverage is best suited to lubricate your grey matter while you explain to me what half the stuff is and does??? :thumbup:

No pressure though ;) :lol:

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What type of prop are you swinging :?:

A variable pitch prop can be trimmed to spin when sailing to charge house batteries WITHOUT using the motor amd motoring around . . . in ever decreasing circles . . . or until :think:

 

On a 46ft we had a variable pitch prop and when over 5 knots it worked well and when doing over 7 knots only lost about half a knot when prop was charging up the batteries, not really that noticable in a cruising yacht.

 

CAUTION: the start batteries may be driven by a generator OR a small alternator with the larger alternator for house batteries. There may be problems when you use thick jumper leads, apart from all the sparks and flashes, because there may be solenoids, regulators, rectifiers etc hidden somewhere. Further the wiring from the small engine generator / alternator might not be adequate to charge both start and house in parallel.

 

Try www.perkins.com for consumption details etc.

 

PM or phone me is you are about tomorow.

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I'll drink just about anything. Just about!!

The big question would be, what do we need to drink so we have the ability of tracing, understanding and having it sink in. No water does not work for me in that instance.

 

Hmmmm, I could easily say, it should have a such and such. But knowing the owner, I will through that thought into the back room of mind. In theory, 24V to 24V via a jumper should be fine. But not knowing this ones wiring just yet, I would very simply disconnect the main leads on the House bank and then jump across to Start bank to crank her up.

Sound like we may have to talk to Cpt K about doing some electrical tidy up and fit some extra while on a mooring generation.

 

Oh and if you want to warm up engine and pour a few billion electrons back into the electron sotrage facilities, put her in reverse and pull on the mooring line. She'll be fine. It will help the engine warm up quickly and under load and give the growth on the prop a headache and maybe some of it will turn green and fal off.

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jumper cables to hard. Stick in a decent VSR (voltage sensitive relay), then, when the start batt is full, it will automatically switch in the hose bank as well. When voltage drops agaiin below a certain point (charging finished) auro switches out. You probably only need the + side switched, provided there is a common -. Simple, automatic, and foolproof! :D

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Simple, automatic, and foolproof! :D

And never fully work properly.

Reason???? when the relay reaches its switch over voltage, the battery is not fully charged. So if that is the only means of charging your house bank, you will never have them fully charged and they will never last the number of years they could do. If you have your house bank as your primary and the switch cuts in and out the Start bank, the Start bank could handle never being fully charged, but you will still never get the full life expectancy from it. And sometimes, especially with these really big engines, they need as much Cranking energy as they can get and they are a big bank which means expensive. So you don't want to be replacing them too often.

In the case of this set up,(as I understand it) there is an Alt on the engine for start bank. There is an Alt on the prop shaft for the House bank. So with prop shaft spinning, due to either sailing or motor running, the house bank is charging. The only issue with that is that it can rob so sailing speed, but shes a big powerful boat, so it may not be toomuch of concern.

The best case scenario in my opinion, would be to have a seletor switch somewhere that would link the two banks for emergency start only and then isolate once engine is started and then when in gear, both banks can be charged under normal situation. I would also seriously recommend a top up type system of Solar that can trickle charge the banks and most importantly, lift the banks beyond the 13.8V regulated output of the Alternator. For absorbtion charging, a voltage of 14.7V is required, which a standard regulated Alternator can not provide. Only a special regulator multi level charging fitted to the Alternator can do that.

The only real place these VSR's should be used in, is small power boat situations where you have an outboard start batt and a small house batt and the two are linked for charging and more "house" power to run the wee chilly or fridge bin etc and then switch out the Start batt once the voltage drops too far, saving the start battery for the engine. Some also may have just one battery and use the VSR for switching out the fridge so as it saves their start batt.

If you want to charge two seperate banks from one charging source, then the only proper way to do this is to use a charge splitter.

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I think it's safer to go for a motor to charge house banks. She has a MONSTER unit off the shaft so should bang them up quick. We have 500amps in the house banks so it's knot like we'll burn them all up in an hour.

 

The wiring is all a bit :? so I'll spend some time over the trip sussing what goes where, why and the rest. At least then I'll know what's what and maybe able to do a simple tweak to boost or spread charging further. Most of the time the boat is in dock so connected to land for power.

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Yep, fair enough.

Wheels, not sure I agree re the VSRs though, although it can take longer to reach 100% charge. If it changes from start to house at say13.8v (for a 12v system), then it charges both banks untill 100% or switched off.

Lots of offshore yachts rarely acheive 100 % charge unless motoring for long periods, or connected to shore power. Many still use diode based spliters whch charge all banks when charging, or dedicated alternators for the starting and house banks. At least the Vsr puts most of the charge into the start battery first, before switching to the others..

Merry Christmas everyone

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Yes that's true IT. I guess I keep coming from the pure cruising self sufficient popint of view and forget about the smaller weekender cruiser where plugging into shore power after a week or two on Holiday gets everything back to full again.

Although, just to take the Start thing a little further....you don't tend to run a start bank down to flat. Unless something is very wrong. So even using a charge splitter, the start bank is back to full kick in pretty short order and the house bank is chugging along sucking juice for ages till they are all happy also.

Hehe, I remember discussing this kind of thing with another boating friend and after me explaining about how it will make his battery last longer, he proudly responded, "well this ole car battery has been doing the task of House battery for 10yrs now and it is still working. How many more years do you expect me to get?" Ha, so that blew the entire argument right out the win....I mean, hatch.

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