Charging Lead-Acid Batts with Very Small Charger

[Kenomac]

Originally Posted by Dockhead

I considered that, but got multiple reports that Mastervolt reliability is about the same or even worse than Victron. One other thing I particularly don't like about Mastervolt is that they use switching transformers which produce a lot of RF noise.


That charger inverter which apparently does have greater reliability than Victron is Magnum -- which is differently engineered from the two complicated very high tech Dutch brands. But I can't buy that here, nor is there any service, so that's out the window.



I seem to be stuck with Victron. Long term -- say, the next boat -- I will install a gang of them, two or even three, so that a failure doesn't take the boat down. And I will sure as heck install them in a more accessible location, than what I have now

I don’t know where you heard or read that, but it’s not factual. We presently have twenty Mastervolt chargers and inverters in service on two boats, and so far no issues at all.... 100% reliable. One thing I don’t understand, is your loyalty to a product like Victron which has a history of letting you down.

When you need to begin installing spares in anticipation of an expected failure, it’s probably a good idea to change your plan.

[Dockhead]

Originally Posted by Kenomac

I don’t know where you heard or read that, but it’s not factual. We presently have twenty Mastervolt chargers and inverters in service on two boats, and so far no issues at all.... 100% reliable. One thing I don’t understand, is your loyalty to a product like Victron which has a history of letting you down.

When you need to begin installing spares in anticipation of an expected failure, it’s probably a good idea to change your plan.

Well, I have a lot of data points on the unreliability Mastervolt charger/inverters, including several Oyster owners in fact. I'm glad you've been so lucky, but you are the first person I've met with much experience with Mastervolt and no problems. The professional marine electricians I deal with in the Solent area all say the same the same thing -- Victron and Mastervolt quite unreliable, with Mastervolt slightly worse than Brand V, and Sterling, despite its El Cheapo background, considerably more reliable than either M or V.


I would love to ditch Victron, which has given me lots of problems, but I just don't have a decent alternative. I'm not willing to give up the functionality of the MultiPlus charger/inverter, which is key to how electrical power works on my boat. The functionality and programmability of the MultiPlus is second to none, the power is super clean, it's totally free of RFI -- it's the best of the best -- when it's not broken. Sort of like a Range Rover, I guess, and oh yeah, I drive one of those


So the new boat will also have Victron in it, just arranged in a gang so that one unit going down doesn't take down the whole system.

[tanglewood]

Originally Posted by Dockhead

:
So the new boat will also have Victron in it, just arranged in a gang so that one unit going down doesn't take down the whole system.

I’d love to hear about ways to gain redundancy from multiple Victron’s. But from what I can tell, two units cuts your MTBF in half rather than increasing it by 2x.

As was pointed out earlier, when they are stacked in parallel, they only work if both units are present and accounted for. So if one fails, they both go down. The other gripe I have is that one of the two doesn’t idle when loads are light to save on standby power draw. Both behaviors are in contrast to Outback, for example.

To get one surviving inverter operational from a Victron pair requires reprogramming the survivor as a stand-alone unit, using a PC and proprietary interfaces. So you could get it going again, but it’s far from seamless.

Or has someone figured out a trick?

I quite frankly would stay with Outback, except that don’t have the load assist function.

[Dockhead]

Originally Posted by tanglewood

I’d love to hear about ways to gain redundancy from multiple Victron’s. But from what I can tell, two units cuts your MTBF in half rather than increasing it by 2x.

As was pointed out earlier, when they are stacked in parallel, they only work if both units are present and accounted for. So if one fails, they both go down. The other gripe I have is that one of the two doesn’t idle when loads are light to save on standby power draw. Both behaviors are in contrast to Outback, for example.

To get one surviving inverter operational from a Victron pair requires reprogramming the survivor as a stand-alone unit, using a PC and proprietary interfaces. So you could get it going again, but it’s far from seamless.

Or has someone figured out a trick?

I quite frankly would stay with Outback, except that don’t have the load assist function.

I've never operated ganged MultiPluses, so my information may be wrong, but I heard that if the slave goes down the master keeps going. If that is wrong, then you still just have to flip a DIP switch or plug in your computer -- this is trivial compared to removing and replacing a unit or rewiring around it.



You are of course correct about MTBF however Double the units and you double the failures


However, the sum of the idle power of two smaller units is similar to the idle power of one larger one, so this is not a big problem.



I am hoping that the more recently built Multipluses are more reliable -- that Victron have been developing it. I have no actual information on this, but Victron is a good company which invests huge sums in R&D -- I would expect they keep improving them. My old Multiplus did last for about 7 years trouble free since the last failure. I wish it would go for decades without a failure, but 7 years is not all that horrible. I will accept that kind of failure rate for the incomparable functionality, programmability, and clean power of these units. I use HF radio as well, so the absence of RFI is also important to me. Charger/inverters with switching power supplies like MasterVolt are much worse in regard to RFI.

[a64pilot]

You could install two, just use one at a time with an A/B switch, that way if one fails, just flip the switch and deal with the broken one once your in port.

[Fuss]

Years ago , I gave you guys a solution, but obviously no one was listening.... here it is again....
You can install 2 or more in series, do you really think that one multiplus cares where it’s source of ac is coming from... would it say, oh, I’m not accepting that ac source, it’s from a multiplus!.
That’s what I do as I have 2, but one feeds into the other. In series and it works, giving me 5000 watts of ac if I need it.

[chris95040]

Originally Posted by Dockhead

...105 amp/hour 12v Trojans...420 amp/hours...210 amp/hours...

On the off chance someone is on the verge of understanding the difference between Power and Energy and is confused by these units, rest assured, battery capacity is measured in amp*hours, not amp/hours.

This isn't just pedantic nomenclature, the use of operators in a unit is fundamental for understanding their meaning and putting them to practical use.

Miles per hour = Miles / Hour. If I'm driving 50 miles per hour, how far do I go in 2 hours? (50 Miles / 1 Hour) * (2 hours) = 100 Miles. The units of the result were (Miles*Hour/Hour). With "Hour" appearing both in the numerator and denominator, the result simplifies to "Miles".

If I'm drinking 3 beers per hour and it's been 2 hours, my six pack is gone.

[john61ct]

amp hour

with a space is correct, or a dash (not any mathematical symbol)

Abbreviated Ah or AH

X amps for Y hours, so yes a bit like multiplication

40A for 15min = 10AH

Amps are already a flow rate that includes a "per time unit" already.

Thus AH are a static quantity of power, and also required when you want to indicate energy usage over a period of time, so

AH per min/hr/day is correct

but amps per min/hr/day makes little sense.

[Dockhead]

Originally Posted by chris95040

On the off chance someone is on the verge of understanding the difference between Power and Energy and is confused by these units, rest assured, battery capacity is measured in amp*hours, not amp/hours.

This isn't just pedantic nomenclature, the use of operators in a unit is fundamental for understanding their meaning and putting them to practical use.

Miles per hour = Miles / Hour. If I'm driving 50 miles per hour, how far do I go in 2 hours? (50 Miles / 1 Hour) * (2 hours) = 100 Miles. The units of the result were (Miles*Hour/Hour). With "Hour" appearing both in the numerator and denominator, the result simplifies to "Miles".

If I'm drinking 3 beers per hour and it's been 2 hours, my six pack is gone.

I absolutely agree with the importance of this, and I thank you very much for the correction. My bad!

[chris95040]

Originally Posted by john61ct

amp hour

with a space is correct, or a dash (not any mathematical symbol)

Abbreviated Ah or AH

X amps for Y hours, so yes a bit like multiplication

40A for 15min = 10AH

As in algebra, the absence of an operator implies multiplication. If you ran your 40 amp load for 0.25 hours, you drained 40*0.25 amp*hours, or 10AH.

Google ‘dimensional analysis’.

Originally Posted by john61ct

Amps are already a flow rate that includes a "per time unit" already.

Thus AH are a static quantity of power, and also required when you want to indicate energy usage over a period of time, so

AH per min/hr/day is correct

but amps per min/hr/day makes little sense.

Amp hour is energy. Amp is power. Although to be clear, you’d actually need the voltage as well to know actual energy and power of those terms.

Here’s some help understanding the difference between the two that some utterly gorgeous genius wrote a while back:

Originally Posted by chris95040

Energy is the amount of work you need to do to accomplish some task. If you lift one case of beer off the dinghy onto the boat, you've done some work. If you lift a second case of beer, now you've done twice as much work. Whether you lifted them both at the same time or one after the other doesn't matter, it's the same amount of work, aka energy, in total. 2 cases worth.

Power is how much work you can do in a certain amount time. I'm a wimp and can only lift one case of beer at a time. My buddy can lift two. He's twice as powerful as me. If hoisting a load of beer onto the mothership takes 10 seconds, my power output is 1case/10seconds. My buddy's is 2cases/10seconds.

To be fair, my buddy and I will each unload half the beer. In total, when we are done loading up, we'll each have done the same amount of work (aka, expend the same amount of energy) but since my buddy is twice as powerful as me, he'll be finished with his share of the work in half the time.

Additionally, if you want to know how much work I can do in 60 seconds, multiply my power output by 60 seconds. (1 case / 10 seconds)*60 seconds = 6 cases loaded on deck. Power, multiplied by time, equals energy. Mmmmmm beer.

For a given voltage,

the Amp is a measure of power.

and

The Amp hour (Ah, amp * hour) is a measure of energy.


Power, multiplied by time, equals energy.

Example: Your alternator may be really powerful and put out 200 amps. Run it for a few seconds and you haven't stored much energy in your batteries (200 amps *.001 hours = 0.2 amp hours), you won't be able to do much work with that! Run it for an hour and you'll have 200 amp hours of energy, nice, time to chill the beer.

[Caddy Shack]

I never leave my boat plugged in. If it's sound enough to sail offshore, then surely it can live safely tied to a dock (or mooring, where plugging in isn't even an option). Even in weeks of heavy winter rains at most I'd end up with a gallon or two in the bilge, since the only place it comes in is through the inside of the mast (that I minimize by covering the openings as best as possible).

If your boat is legit close your seacocks and walk away.

PS. I should note that I have good passive ventilation so that mildew is not an issue either.

[john61ct]

Leaks can arise while you're away

[Caddy Shack]

Originally Posted by john61ct

Leaks can arise while you're away

Sure, as can a fire or charging issues....

Best if you have someone reliable with eyes on her.

[Dockhead]

Originally Posted by Caddy Shack

Sure, as can a fire or charging issues....

Best if you have someone reliable with eyes on her.

That's very true, and it's a good point.



I think if my batteries could be totally isolated without fiddling with cables, I would probably just leave her unplugged.



But I have some very small but not zero loads which gradually run the batteries down when I'm not off board, so I like to leave her plugged in despite the risk of fire (or charging issue).


To illustrate Caddy Shack's point -- I once had a cell short out while I was not on board, which led to all the batteries boiling out as the charger tried to make up for the low voltage. I arrived on board just before something worse happened.


After that I got the temperature sensor for the charger installed

[Dockhead]

Originally Posted by john61ct

Leaks can arise while you're away

Also true. I close all my sea cocks when I'm off board -- except however six deck/cockpit drains. There is always a risk that something can split, come off, or leak despite good maintenance.


There's just no good solution for this which covers every eventuality.


It will be easier once I have lithium batteries.


I suppose one could have a separate single bilge pump battery which stays on the charger, while the main bank is isolated, but that is sure a faff and a bunch of complexity. Maybe if you have a separate small bank for radios as per GMDSS/SOLAS, you could hook up one bilge pump to that.