Newbie charging question. (Sorry)

[Krusty]

Hello everyone.

Please be gentle with me as this is probably a silly question. I've looked at past threads but to be honest, when I typed in battery, I got so many old threads that it will take years to read them all.

I have a 110 amp alternator, split charge relay into 1 starter battery and 4 x 110 amp domestics.

After a 2 or 3 second burst of power from the starter battery to start the engine, that's it for the day so the battery still has a high soc.

My question (silly?): When cruising/running for a few hours and the starter battery is fully charged, is there a piece of kit ( or re-wiring trick ) that will divert the charging power, from the starter battery to the domestics or is this done automatically?

If so, will the domestic batteries get charged quicker?

Many thanks.

[Robbo]

You already have it - split charge relay!

 

When your engine is running it links the battery banks together.

Edited September 21, 2013 by Robbo

[Tony Brooks]

To expand Robbo's answer.

 

The amount of current (charge) that flows into a battery is proportional to the difference in voltage between the battery at whatever its present state of charge is and the alternator and 0.1v is a lot in this context.

 

Any explanation is complicated by the fact that unless the batteries are all very well charged the alternator voltage will start off lower than when they are fully charged and then gradually climb until the voltage regulator starts to work. However this makes no difference to how the charge is apportioned.

 

Engine battery fully charged - battery voltage 12.8 volts, charging voltage 14.2 volts, difference 1.4 volts.

 

Domestic battery well discharged - battery voltage 12.3 volts, charging voltage 14.2 volts, difference 1.9 volts

 

So more current will naturally get pushed into the domestic bank.

 

Far too often the man alternator output is fed to the engine battery and the relay is used to connect the engine battery pos. to the domestic bank. This is asking for problems because oh high current flows and voltage drop through the relay during charging. Ideally the main charging lead will go to the domestic bank and the relay connect to the engine bank. This is probably far more important than worrying about diverting the engine charge to the domestic bank.

[by'eck]

 

Hello everyone.

Please be gentle with me as this is probably a silly question. I've looked at past threads but to be honest, when I typed in battery, I got so many old threads that it will take years to read them all.

I have a 110 amp alternator, split charge relay into 1 starter battery and 4 x 110 amp domestics.

After a 2 or 3 second burst of power from the starter battery to start the engine, that's it for the day so the battery still has a high soc.

My question (silly?): When cruising/running for a few hours and the starter battery is fully charged, is there a piece of kit ( or re-wiring trick ) that will divert the charging power, from the starter battery to the domestics or is this done automatically?

If so, will the domestic batteries get charged quicker?

Many thanks.

 

 

The simple answer is don't worry about this issue.

 

The starter battery, once (quickly) re-charged, will then draw so little current as not to deprive the domestic bank whilst the split charge relay is energised.

[nicknorman]

Yes, I think the important point is that its the battery that decides how much current to absorb, and once it is fully charged (very soon, in the case of the starter battery) it will naturally cease taking all but a very small charge current, meanwhile virtually all the alternator output will go to the domestic battery, until it too is fully charged.

 

The amp rating of the alternator determines only the maximum current. Once both batteries are fully charged, the alternator will only be putting out a few amps.

[Krusty]

Thanks all for your replys.

 

Looks like I'll have to find something else to worry about.

 

Tony, just checked, and, as you suggested, the alternator lead does go to the domestic bank first.

 

K.

[Tony Brooks]

Then that bodes well for the quality of the engineering & electrical fit-out.

[comfortably numb]

I have a question about charging which I know has been answered in the past but I can't find it so being as this is a live thread of a similar nature I'd live to take the opportunity to ask.

 

What is the lowest a battery is safe to go down to before it damages it and makes it so it won't hold its charge so well in future? On days when I'm not cruising more than a couple of hours the reading has gone down as low as 1160 by bedtime and I seem to remember that this is about the threshold. Is this about right?

 

On none cruising days I run the engine for an hour twice a day and the reading goes up to about 1300+. I try to keep to a minimum stuff that is using electricity but we do have on permanently a 240v fridge/freezer and the other things are TV in the evening, laptop charging, and a couple of LED lights after dusk.

 

Should I be running the engine for longer than 2 hours in order to replenish what I'm taking out, or is the loss of charge partly attributable to the batteries being 4 years old and/or me having damaged them by letting them get too low? BTW I do check them regularly and ensure they are topped up.

 

I'm a real dummy with anything to do with electrics so please forgive if these are stupid questions, LOL.

[DeanS]

I have a question about charging which I know has been answered in the past but I can't find it so being as this is a live thread of a similar nature I'd live to take the opportunity to ask.

 

What is the lowest a battery is safe to go down to before it damages it and makes it so it won't hold its charge so well in future? On days when I'm not cruising more than a couple of hours the reading has gone down as low as 1160 by bedtime and I seem to remember that this is about the threshold. Is this about right?

 

On none cruising days I run the engine for an hour twice a day and the reading goes up to about 1300+. I try to keep to a minimum stuff that is using electricity but we do have on permanently a 240v fridge/freezer and the other things are TV in the evening, laptop charging, and a couple of LED lights after dusk.

 

Should I be running the engine for longer than 2 hours in order to replenish what I'm taking out, or is the loss of charge partly attributable to the batteries being 4 years old and/or me having damaged them by letting them get too low? BTW I do check them regularly and ensure they are topped up.

 

I'm a real dummy with anything to do with electrics so please forgive if these are stupid questions, LOL.

 

You're going to get some expert advice , which I'll rehash now quickly before giving you my take on it.

 

1. Make sure you give your batts a nice 8hr charge once a week to get them to 100%.

 

My advice(as doing a 8hr run once a week is often not possible unless you have a gennie that can run for that long, or are doing a long trip), is to monitor the reading (which I presume is under load...and would show higher if you removed all the load, let the batt settle and then read it), ....and work out a trend graph for yourself. Keep within your upper and lower limits....and you should be fine. In other words, if it goes down to 11.7V (under load) and thats lower than what you normally see, then it's a good indication you arent charging enough.). I will get slated for saying that.......but under load you'll struggle (with a fridge on permanently) , to see it above 12V often, in the middle of the night. Solar is helpdful during the say in summer.

[Naughty Cal]

11.6v is effectively flat. Ideally you would want to see readings below 12.2v.

 

It sounds like your charging regime isn't keeping up with your power demands. You need to be charging for longer and looking at ways to reduce your power consumption.

[bottle]

I have a question about charging which I know has been answered in the past but I can't find it so being as this is a live thread of a similar nature I'd live to take the opportunity to ask.

 

What is the lowest a battery is safe to go down to before it damages it and makes it so it won't hold its charge so well in future?

That figure does not exist any discharging of a battery damages it until it will not hold a charge but the general advice is to never let the batteries go below 12,2v (50% SOC) this is a balance between usage and damage.

 

On days when I'm not cruising more than a couple of hours the reading has gone down as low as 1160 by bedtime and I seem to remember that this is about the threshold. Is this about right?

11,6 battery is 'flat as flat can be' and will die completely very soon if you let it get that low.

 

On none cruising days I run the engine for an hour twice a day

Probably not enough but without battery monitoring you will never know.

 

and the reading goes up to about 1300+. I try to keep to a minimum stuff that is using electricity but we do have on permanently a 240v fridge/freezer and the other things are TV in the evening, laptop charging, and a couple of LED lights after dusk.

 

That 13v is it with or without the engine running or just after the engine is turned off, the only way to tell when a battery is charged by the voltage is after the battery has rested.

 

 

 

Should I be running the engine for longer than 2 hours in order to replenish what I'm taking out,

Yes

 

or is the loss of charge partly attributable to the batteries being 4 years old and/or me having damaged them by letting them get too low?

Yes

 

BTW I do check them regularly and ensure they are topped up.

Well you got that bit right

 

I'm a real dummy with anything to do with electrics so please forgive if these are stupid questions, LOL.

No question is stupid, some of the answers maybe.

[Sir Nibble]

Difficult. Lots of people say you should charge your batteries for 8 hours at least once every week. I say "really? why?" Some say you should run a long high voltage equalisation charge every so often. I say again, "really? why?

How much you charge depends on how much you discharge. A set of batteries on a chandlers shelf do not require an 8 hour charge once a week. A heavily discharged and frequently cycled set will. There is no simple answer nor universal rule of thumb. Do not let batteries rule your life, they are there to serve you not the other way around. Broadly speaking the better charged your batteries and the less time they spend discharged the better for them. My last set were utterly ignored and charged only when the boat was moving and lasted 10 years. If you consider putting yourself to constant trouble and worry worth getting another year out of them then that is your decision. If batteries are for light and pumps then just don't worry. If on the other hand you use them to run washing machines, high power home cinema systems with a sound system that would shame Led Zep and of course the indispensable on board iron foundry then you deserve everything you get.

[blackrose]

11.6v is effectively flat. Ideally you would want to see readings below 12.2v.

 

 

 

Surely you meant wouldn't?

[Tony Brooks]

Although I also think CN probably means 11.6 volts it is possible he has given us a specific gravity (relative density) reading of 11.60, but the answer is still the same - that is far too discharged for optimum life.

 

Just shows how careful one needs to be when asking questions.

[smileypete]

As long as the batt voltage can recover above 12.2V 'off load', ie when less stuff is on, then all is well.

 

Going a bit below will add some wear and tear but it's not the end of the world. What is useful is an ammeter either fitted (shunt type) or handheld (DC clamp type), to monitor how full the batts are getting when they're being charged.

 

If the batts are never recharged fully they'll gradually lose capacity making it harder to get back above the magic 12.2V figure.

 

If you're living aboard 'off grid', as Dean says a good long charge at least weekly, say 6-8hr engine, genny, or maybe even solar if there's plenty of it will help keep the batts tippy top.

 

cheers, Pete.

~smpt~

Edited September 22, 2013 by smileypete

[comfortably numb]

Thanks everyone for your advice. Sorry I did forget to put the decimal point in my figures btw.

 

I will take on board all the information given and keep a careful eye on them. They don't appear to be holding their charge very well so it looks as if letting them get too low has b*ggered them.

 

We're out and about for the next 4 weeks but hopefully I can get by until we're back at the marina and onto shore power. At least then I might not have to get new ones until after the winter.

 

But as Sir Nibble says, I'm not going to let them rule my life and if I have to change them sooner than later then so be it.

 

Thanks again boys and girls.

[Robbo]

 

What is the lowest a battery is safe to go down to before it damages it and makes it so it won't hold its charge so well in future? On days when I'm not cruising more than a couple of hours the reading has gone down as low as 1160 by bedtime and I seem to remember that this is about the threshold. Is this about right?

 

 

The more you take out the more you damage it. There's no "50% rule". Leisure batteries damage more if you go below 90% this is why there only really good for leisure. A Traction type battery can handle 30%, but it's still not good for it.

[Terryb]

Hi guys,

as a side issue, I am weighing up all the information I will need to ( within reason ) come to terms with a reasonable cost per week of running ( say ) a 50' NB.

Its 10 years to go before the UK Gov decide I need to work till. I say,stuff you I'm off. So with early retirement in mind and an income of around £100 per week ( excluding emergency fund of £xxxxx ) what do you Liveaboards think ?

Tying this in to this topic, one of my quandaries is, what I can and can't do, with regards to battery life. Are solar panels worth the expense etc.

 

Any, and all info will be greatly appreciated. Thanks in advance.

 

Terry

[Phil Ambrose]

Hi guys,

as a side issue, I am weighing up all the information I will need to ( within reason ) come to terms with a reasonable cost per week of running ( say ) a 50' NB.

Its 10 years to go before the UK Gov decide I need to work till. I say,stuff you I'm off. So with early retirement in mind and an income of around £100 per week ( excluding emergency fund of £xxxxx ) what do you Liveaboards think ?

Tying this in to this topic, one of my quandaries is, what I can and can't do, with regards to battery life. Are solar panels worth the expense etc.

 

Any, and all info will be greatly appreciated. Thanks in advance.

 

Terry

Oh dear I'm not sure that £100-00 a week is going to be enough, it may be possible if you are very very frugal but a license is going to cost you something like £13 pw just for starters. You may be able to scavenge enough fuel to keep warm for free, and if you CC mooring fees wont come into the equation but you will need to come out every 2 years for blacking plus the cost of new anodes, fuel for propulsion and hot water, general maintainance is a constant cost. Insurance is another cost plus BSC every 4 years. Hang on till some more financial savvy members come along.

Living on a boat is not a cheap option, I know as we have lived aboard for 13 years.

 

Welcome to the Forum,

Phil

[nicknorman]

I'm not a liveaboard but my take is that solar is definitely worth it if you plan to stay tied up for your 14 day allowance or thereabouts. On the other hand, if you plan to cruise every day they're not worth it because you will be recharging the batteries whilst cruising.

 

Although solar is initially expensive, when looking at cost comparisons don't forget to allow for wear and tear on the engine, as well as fuel. Also solar does seem to help with battery longevity if it is able to fully recharge the batteries during the day. Of course, this is only likely to be the case for the summer half of the year

 

In terms of non-financial issues, solar is much quieter than a genny or engine! Plus you get that cosy Eco-feeling when your batteries are being charged "for free".

[nb Innisfree]

Difficult. Lots of people say you should charge your batteries for 8 hours at least once every week. I say "really? why?" Some say you should run a long high voltage equalisation charge every so often. I say again, "really? why?

How much you charge depends on how much you discharge. A set of batteries on a chandlers shelf do not require an 8 hour charge once a week. A heavily discharged and frequently cycled set will. There is no simple answer nor universal rule of thumb. Do not let batteries rule your life, they are there to serve you not the other way around. Broadly speaking the better charged your batteries and the less time they spend discharged the better for them. My last set were utterly ignored and charged only when the boat was moving and lasted 10 years. If you consider putting yourself to constant trouble and worry worth getting another year out of them then that is your decision. If batteries are for light and pumps then just don't worry. If on the other hand you use them to run washing machines, high power home cinema systems with a sound system that would shame Led Zep and of course the indispensable on board iron foundry then you deserve everything you get.

I could be wrong but I think the 8hr weekly charge thing originated with me, after various charging regimes I found a weekly(ish) absorption charge to be as long as we could go before the voltage started to drop out, sometimes it was less than a week sometimes more. It seemed to be a reasonable regime and still does, but it was picked up and repeated until it's become some sort of 'rule'. Same with the 50% rule, it's been distorted so that it's ok to go down to 50% SoC but not any lower, a sort of safe minimum, if you stay above that your batts will be ok and suffer no damage. It's been reinforcd by the fact that Gibbo published it but he did state on here that there is nothing special about 50% with regard to battery damage but that it's the best compromise between battery costs and fuel costs, unfortunately the myth seems to have taken root. Edited October 10, 2013 by nb Innisfree

[nicknorman]

I could be wrong but I think the 8hr weekly charge thing originated with me, after various charging regimes I found a weekly(ish) absorption charge to be as long as we could go before the voltage started to drop out, sometimes it was less than a week sometimes more. It seemed to be a reasonable regime and still does, but it was picked up and repeated until it's become some sort of 'rule'. Same with the 50% rule, it's been distorted so that it's ok to go down to 50% SoC but not any lower, a sort of safe minimum, if you stay above that your batts will be ok and suffer no damage. It's been reinforcd by the fact that Gibbo published it but he did state on here that there is nothing special about 50% with regard to battery damage but that it's the best compromise between battery costs and fuel costs, unfortunately the myth seems to have taken root.

As fairly heavy electrical users and a 440Ah bank, by the time we have had the electric blanket on overnight and used the electric kettle and toaster for breakfast we are often down to 50-something percent. Having both a Smartgauge and AH counting gauge its easy for me to keep track of the actual battery capacity on a day by day basis. I find that after a few weeks use even with 8 hrs cruising per day, capacity is starting to reduce noticeably, but a 15.5v (temperature compensated) belt for an hour or so restores it. If we tie up and run the engine for an hour or two (175A alternator) per day, by day 3 the capacity is starting to noticably reduce and it takes a good charge to current 0.5% of capacity culminating in say 15v to get things back to normal. When things are normal the batteries which are now 18 months old, retain their full 440 Ah capacity within the accuracy I can measure it.

 

So I would say that a long weekly charge is pretty important. Of course if you have a reasonable bank and are a light user, you may not know or care that the capacity is down to 50% of what it could/should be

Edited October 10, 2013 by nicknorman

[Phil Ambrose]

Wow Nick an electric blanket on all night, your boat must be a cold one, we have a 4 tog duvet on all year and never feel cold, in fact we spend most of the winter in T shirts

 

Phil

[nicknorman]

Wow Nick an electric blanket on all night, your boat must be a cold one, we have a 4 tog duvet on all year and never feel cold, in fact we spend most of the winter in T shirts

Phil

We're just wimpy northerners! We have a stove at the front, a bedroom at the back with a bathroom in the middle with side corridor, so bedroom can get quite cold in the depths of winter without the Mikuni on. If I was ever building a liveaboard I would now know to have the stove in the middle and/or back boiler with rads.

 

The leccy blanket is the best thing since ... as its an underblanket with thermostatic control so is left on all night and just means that when you roll over in bed you don't hit a cold spot. It seems to use less than 5% SoC in 8 hrs but makes for a fantastic night's sleep. There is no need for boating to be a feat of endurance!

[Naughty Cal]

 

Surely you meant wouldn't?

Of course!

Wow Nick an electric blanket on all night, your boat must be a cold one, we have a 4 tog duvet on all year and never feel cold, in fact we spend most of the winter in T shirts

 

Phil

I must admit we also have an electric blanket on NC. We like to get into a toasty warm bed on a cold winters night!