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Designing 12v charging system from scratch


Capnbob

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I hoped this would be so easy. Oh dear...

Acquired a 13 year old boat in October, took 10 days to sail it back home, and moored up at marina with 240v shoreline. All 12v services (from 3 batteries) seemed fine. I assumed there'd be a 240v battery charger, but went looking when the lights started going dim after 24 hours and discovered not only is there NOTHING to recharge the batteries (apart from the second alternator), there's no battery management, not even a simple meter (apart from when I stick my ammeter into the exposed inverter tails).

This obviously needs rectifying, and I'm wondering what might be a sensible "standard" setup for a boat that's used about equally between liveaboard, holiday cruising and moored empty. No, I know there is no standard setup, but I'd be grateful for ideas for a shopping list - starting from the nothing I've got - for a system to get this right before I ditch these batteries and buy new ones (which I think will happen quite soon; don't think these will charge above 12.5v).

BTW I *have* waded through the forums for answers, and forgive me if I've missed an obvious summary somewhere, but a) answers on individual system elements tend to be spread between several separate topics; and B) many apparently authoritative recommendations are now years old so potentially out of date.

Thanks for your thoughts...

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It sounds like the boat is at the "basic" end of what most would concider "standard". Just needs a volt meter and a small charger to maintain the battery whilst at the marina. Wire the charger so that it only works from the shore supply. Check and clean all the terminals and away you go. Bear in mind that its probably worked fine for the first 13 years, so there can't be that much wrong with it. More expensive and complex options are available.

Edited by Eeyore
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An ammeter is also essential when you’re out and about in order to simply determine end of charge. You can opt for a cheapy Chinese job for a fiver or you can spend £100+ for something more clever which will also offer Ah counting. 

If you are able (have the knowledge and experience) to determine the state of charge with a voltmeter while the batteries are under load then all you require in addition to the ammeter is an accurate voltmeter. If you want something simpler then a SmartGauge takes the guesswork out of it but that’s £120 again. 

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This is for battery monitoring of course. Charging is a different subject and we need to know your daily usage, how much time you’ll spend on shore power, and the size of your battery bank to offer suggestions. 

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1 hour ago, Capnbob said:

I hoped this would be so easy. Oh dear...

Acquired a 13 year old boat in October, took 10 days to sail it back home, and moored up at marina with 240v shoreline. All 12v services (from 3 batteries) seemed fine. I assumed there'd be a 240v battery charger, but went looking when the lights started going dim after 24 hours and discovered not only is there NOTHING to recharge the batteries (apart from the second alternator), there's no battery management, not even a simple meter (apart from when I stick my ammeter into the exposed inverter tails).

This obviously needs rectifying, and I'm wondering what might be a sensible "standard" setup for a boat that's used about equally between liveaboard, holiday cruising and moored empty. No, I know there is no standard setup, but I'd be grateful for ideas for a shopping list - starting from the nothing I've got - for a system to get this right before I ditch these batteries and buy new ones (which I think will happen quite soon; don't think these will charge above 12.5v).

BTW I *have* waded through the forums for answers, and forgive me if I've missed an obvious summary somewhere, but a) answers on individual system elements tend to be spread between several separate topics; and B) many apparently authoritative recommendations are now years old so potentially out of date.

Thanks for your thoughts...

when you say exposed inverter tails do you mean wiring where an inverter used to be?

if that is the case you will probably find that the missing inverter was a combi unit (inverter and charger)

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3 hours ago, Capnbob said:

I hoped this would be so easy. Oh dear...

Acquired a 13 year old boat in October, took 10 days to sail it back home, and moored up at marina with 240v shoreline. All 12v services (from 3 batteries) seemed fine. I assumed there'd be a 240v battery charger, but went looking when the lights started going dim after 24 hours and discovered not only is there NOTHING to recharge the batteries (apart from the second alternator), there's no battery management, not even a simple meter (apart from when I stick my ammeter into the exposed inverter tails).

This obviously needs rectifying, and I'm wondering what might be a sensible "standard" setup for a boat that's used about equally between liveaboard, holiday cruising and moored empty. No, I know there is no standard setup, but I'd be grateful for ideas for a shopping list - starting from the nothing I've got - for a system to get this right before I ditch these batteries and buy new ones (which I think will happen quite soon; don't think these will charge above 12.5v).

BTW I *have* waded through the forums for answers, and forgive me if I've missed an obvious summary somewhere, but a) answers on individual system elements tend to be spread between several separate topics; and B) many apparently authoritative recommendations are now years old so potentially out of date.

Thanks for your thoughts...

IMHO the only sensible minimum for modern day us is:-

  1. (A second alternator - you have that already)
  2. An alternator controller (open to discussion if the current device is not capable of staged charging) examples Sterling, Adverc)
  3. A battery status reporting system (aka "battery management") Vetus do a good one
  4. A good set of batteries. Capacity and type is always open to much argument, from 2v traction types down to heavy duty wet cell type. Capacity depends on your anticipated usage.
  5. An inverter or preferably an inverter/charger sized for your usage, preferably pure sine wave.

Those are the components. The discussion starts when you bring costs into and / or get woolly about what you want the batteries to do. Electric cookers  / heaters even microwaves take a vast amount of power. Large tvs, laptops, big HiFis take a bit less, but still need a decent system. 

It can't be simpler than the four points  above. 2 and 3 above are relatively inexpensive. 4 and 5 are where the money goes and are not absolute.

I have all five and the batteries are NiFe.   

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5 hours ago, Capnbob said:

I hoped this would be so easy. Oh dear...

Acquired a 13 year old boat in October, took 10 days to sail it back home, and moored up at marina with 240v shoreline. All 12v services (from 3 batteries) seemed fine. I assumed there'd be a 240v battery charger, but went looking when the lights started going dim after 24 hours and discovered not only is there NOTHING to recharge the batteries (apart from the second alternator), there's no battery management, not even a simple meter (apart from when I stick my ammeter into the exposed inverter tails).

This obviously needs rectifying, and I'm wondering what might be a sensible "standard" setup for a boat that's used about equally between liveaboard, holiday cruising and moored empty. No, I know there is no standard setup, but I'd be grateful for ideas for a shopping list - starting from the nothing I've got - for a system to get this right before I ditch these batteries and buy new ones (which I think will happen quite soon; don't think these will charge above 12.5v).

BTW I *have* waded through the forums for answers, and forgive me if I've missed an obvious summary somewhere, but a) answers on individual system elements tend to be spread between several separate topics; and B) many apparently authoritative recommendations are now years old so potentially out of date.

Thanks for your thoughts...

I hope that you do not mean what the red above reads like. If you do you also probably need to buy a new ammeter - I hope you mean voltmeter.

Edited by Tony Brooks
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50 minutes ago, Tony Brooks said:

I hope that you do not mean what the red above reads like. If you do you also probably need to buy a new ammeter - I hope you mean voltmeter.

Yes, I came back to this thread to mention the same thing. With any luck if he did do what he wrote he’ll have just blown the internal fuse but I suspect he did indeed mean voltmeter. 

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Thanks for the comments. Some responses:

"An ammeter is also essential when you’re out and about in order to simply determine end of charge."

Do you mean seeing when I've used up everything I put in at the last charge? That makes sense, and explains why Ah counting is so valuable

"If you are able ... to determine the state of charge with a voltmeter while the batteries are under load..."

Good point. I've seen the necessary voodoo described somewhere on here, so presumably it's learnable. Tempted by the Smartguage, but wonder if I can justify £120.

"we need to know your daily usage, how much time you’ll spend on shore power, and the size of your battery bank"

Point taken, but I have no idea myself yet. At the moment we're living on board, and mostly stationary (but with shorepower), but eventually I anticipate a more leisure usage pattern. No heavy use items, and I'm hoping to reduce where I can, such as changing all the halogen lights for leds.

"when you say exposed inverter tails do you mean wiring where an inverter used to be? "

Ah, no, sorry. There is a working 1500w inverter, but never switched it on yet. And yes, I should have said multimeter (voltmeter), not ammeter. The tails are exposed (which I must fix) but which does at least offer a convenient route to the battery terminals for checking voltage. Otherwise, where should I check the voltage?

" And if the combi has gone, what is the shore line connected to? "

Consumer unit with 2 circuit breakers. Simple swapover of shoreline socket to inverter output when on the canal.

"I have all five and the batteries are NiFe."

Realy useful summary, thanks, with pointers for much research.

"Many battery monitors can only monitor up to 200A"

Yes; keen to make it all forwards compatible, and just the sort of thing I was concerned about when I mentioned authoritative - but old - threads.

This is all letting in some light through the fog, and I'm very grateful.

If it's easy I'd love to hear what actual devices people use/would get if upgrading - it would really help me scope my own project.

 

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Try and estimate what your power requirements might be.  Do you want all the conveniences of home?  To run microwaves, washer dryers, induction hobs etc will take a punishing toll on your electrcal system.  It's better to go with modest systems and forego the trappings of suburban bliss.

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There are so many ways to skin the cat!

For battery charging, do you intend to use a generator when away from shore power, or just charge from the engine? If the former, you will need a fairly high current charger to minimise genny running time, but be careful about the max generator power to “start up” the charger (aka surge current). If the latter, you just need a small charger for use when on shore power (when time is not of the essence).

to make the best of the alternator(s) you need to minimise voltage drop between them and the batteries. Good connections with fat cable throughout. An alternator controller (adverc or Stirling) will help to minimise charge time if you are likely to be running the engine only to charge the batteries.

Then there is the battery issue. Personally I have never got on well with dual purpose (cheap) leisure batteries. I think my semi-traction Trojans are great! It depends on your expectations.

Inverters: older inverters were often quasi-sine (modified sine) which is not ideal. A decent pure sine inverter is fairly cheap these days but one of the important difference between a quality Mastervolt inverter and a cheapo pure sine inverter of seemingly quite similar spec, is the current consumed when the inverter is idling.  Massive difference! It depends on whether you want mains power available all the time (we do) or whether you are happy to turn the inverter off when you’re not actually using it.

Inverters vs Combis. A Combi is a combined inverter charger, switching seamlessly between shore or genny power and inverter power, or a mixture (for high power loads). On shore /genny it automatically starts charging the batteries. Personally I think they are great but there is also a school of thought that it’s bad to put 2 devices in one basket such that when one fails, you lose both. IMO if you buy quality this is not much of an issue.

7 minutes ago, mross said:

  To run microwaves, washer dryers, induction hobs etc will take a punishing toll on your electrcal system.  It's better to go with modest systems and forego the trappings of suburban bliss.

I disagree. The only important thing is to ensure that the capabilities of the system match the expectations.

Edited by nicknorman
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1 hour ago, Capnbob said:

"An ammeter is also essential when you’re out and about in order to simply determine end of charge."

Do you mean seeing when I've used up everything I put in at the last charge? That makes sense, and explains why Ah counting is so valuable

Nope. An ammeter shows the current going into or out of the battery. When you are away from shore power and charging from generator and charger or from alternator it can tell you when your batteries are about full. 

A Smartgauge can tell you when you’ve used up what you put in at your last charge. An Ah counter can try to tell you the same thing, generally with less accuracy. A voltmeter can, with experience, also tell you much the same thing. 

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2 hours ago, Capnbob said:

Ah, no, sorry. There is a working 1500w inverter, but never switched it on yet. And yes, I should have said multimeter (voltmeter), not ammeter. The tails are exposed (which I must fix) but which does at least offer a convenient route to the battery terminals for checking voltage. Otherwise, where should I check the voltage?

" And if the combi has gone, what is the shore line connected to? "

Consumer unit with 2 circuit breakers. Simple swapover of shoreline socket to inverter output when on the canal.

"I have all five and the batteries are NiFe."

 

What make inverter, and are you sure it isn't a combi inverter/charger this could change lots of things.  Do you have a fridge, if so 12 volt or 240 volt, makes a huge difference to your daily requirements. Do you have or want, Solar also needs to be considered. If the inverter is OK and adequate for your needs then you need a charger, you can get good chargers that include a Solar MPPT controller in them, but you need to know how much Solar you are going to have. Space to fit this lot also matters.

I do not understand "I have all five " if you do have five genuine good NiFe batteries it completely changes the situation as NiFe need special chargers and cannot be charged from much of the gear you will have seen mentioned on this forum. Victron do some chargers for NiFe and I believe a few of the Sterling bits are geared up for them. If they are NiFe and are not duff they would cost £600-1000 per battery. None of the battery monitors I know off are able to read SOC of NiFe batteries and as I understand you will be better off with a £30 amphour counter from e-bay. As NiFe are almost 99% efficient, ie. discharge 100 Amphours you need to put in 101 Amphours to replace that charge, not the 115-125 Amphours you need with lead acid.  All Battery monitors currently use voltage and amphours to guess the SOC, NiFe have almost no voltage change from 90% to 10% (a few millivolts)  it is only the Amphours that can be used.

 

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2 minutes ago, Detling said:

What make inverter, and are you sure it isn't a combi inverter/charger this could change lots of things.  Do you have a fridge, if so 12 volt or 240 volt, makes a huge difference to your daily requirements. Do you have or want, Solar also needs to be considered. If the inverter is OK and adequate for your needs then you need a charger, you can get good chargers that include a Solar MPPT controller in them, but you need to know how much Solar you are going to have. Space to fit this lot also matters.

I do not understand "I have all five " if you do have five genuine good NiFe batteries it completely changes the situation as NiFe need special chargers and cannot be charged from much of the gear you will have seen mentioned on this forum. Victron do some chargers for NiFe and I believe a few of the Sterling bits are geared up for them. If they are NiFe and are not duff they would cost £600-1000 per battery. None of the battery monitors I know off are able to read SOC of NiFe batteries and as I understand you will be better off with a £30 amphour counter from e-bay. As NiFe are almost 99% efficient, ie. discharge 100 Amphours you need to put in 101 Amphours to replace that charge, not the 115-125 Amphours you need with lead acid.  All Battery monitors currently use voltage and amphours to guess the SOC, NiFe have almost no voltage change from 90% to 10% (a few millivolts)  it is only the Amphours that can be used.

 

It is 'Old Goat' that has the Nife batteries - NOT CapnBOb

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13 hours ago, WotEver said:

Yes, I came back to this thread to mention the same thing. With any luck if he did do what he wrote he’ll have just blown the internal fuse but I suspect he did indeed mean voltmeter. 

Yes. if he used anything other than the 10/20 amp scale. All the meters I have seen (fairly cheap because it was in FE) only fused the mA scales with this highe est scale just being a shunt. Sometimes the solder holding the crude shunt wires into the PCB melt so you can resolder them. However how accurate the meter is after that goodness knows. In other cases the  shunt wires melt. I used to fit a 13 Amp fuse in the meter leads but still the students managed to wreck meter.

Please to see the OP confirmed he was using a voltmeter.

Edited by Tony Brooks
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I use a 20 year old avo digital meter as my main one, I think the worst I have done to it was put it across mains.... while the meter was set on continuity test.

after doing that I would have expected to need to replace the meter but in this case it just bleeped (50 times a second) and carried on working perfectly

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On 08/12/2017 at 19:27, Capnbob said:

Yes; keen to make it all forwards compatible, and just the sort of thing I was concerned about when I mentioned authoritative - but old - threads.

 

I'm not sure why you think information in old threads goes 'out of date', it doesn't. Battery technology is evolving glacially slowly despite what the media would have you think. Very little written 10 years ago is wrong today.

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On 08/12/2017 at 21:21, WotEver said:

A Smartgauge can tell you when you’ve used up what you put in at your last charge. An Ah counter can try to tell you the same thing, generally with less accuracy.

 

You have to love WotEver's blind loyalty to the Smartgauge. He never mentions the following:

Firstly, they cannot be relied upon to be accurate either. There are five examples on just this forum of them being wildly inaccurate straight from the box. (So inaccurate in fact that people have wrecked their battery banks.) That's from a random sample of perhaps 20 users here who have taken the trouble to check the calibration of theirs.

Secondly, the Smargauge will tell you when the batteries are 100% charged but it is usually wrong, even on a correctly calibrated Smartgauge. just like the AH counter can be wrong, so beware both types of monitor.

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1 minute ago, Mike the Boilerman said:

 

You have to love WotEver's blind loyalty to the Smartgauge. He never mentions the following:

Firstly, they cannot be relied upon to be accurate either. There are five examples on just this forum of them being wildly inaccurate straight from the box. (So inaccurate in fact that people have wrecked their battery banks.) That's from a random sample of perhaps 20 users here who have taken the trouble to check the calibration of theirs.

Secondly, the Smargauge will tell you when the batteries are 100% charged but it is usually wrong, even on a correctly calibrated Smartgauge. just like the AH counter can be wrong, so beware both types of monitor.

I'll give you £11 for both yours.......well it is nearly Christmas!

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On 09/12/2017 at 12:13, rusty69 said:

I'll give you £11 for both yours.......well it is nearly Christmas!

 

Funny you should say that. I'm impressed you think they are that valuable.

Edited by Mike the Boilerman
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Thing is Mike even if they are recalibrated as you have solar they will lie to you when your solar is active especially if the solar is only lifting the battery voltage slightly and not putting in a significant charge. They will however be accurate after a couple of hours darkness and then remain like that until the next dawn.  I find 3am as one is on the way to have the middle of the night wee a good time to check SOC :o

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