mains power / inverter / charger question

[DaveNTL]

having just replaced two expensive gel house batteries on the 'new' boat (2001 boat but its new to me, this is the 3rd set of batteries it's had) i'm a bit baffled as to the design phylosophy it has, and i throw open to you (the oracle) for comments about it

what doesnt seem logical to me first off is that when plugged into shore power it goes through the charger / batteries / inverter to run the socket outlets of which there are 10 in the boat - typically i run a microwave, toaster, tv, and electric fan heaters.

I cant run all these at once, not that i want to of course, but at the moment i am limited to, say, one heater and the microwave.

if i put anything else on the battery charger breaker trips.

the refrigeration is 12volt, so i understand why that would always coming off the batteries

it this 'normal' ? wouldn't either a manual or perhaps even an automatic change-over switch of some sort be more sensible to run the mains when on shore power?

i think the design 'problem' comes from the generator / inverter size - i.e. the thinking behind it is, when not hooked up to shore power, if the generator can only provide 4kw and the charger / inverter are matched then that is how much power there is and you have to live with it

on a final note - i then went on to thinking - even though gel cells are supposed to be good at taking a deep discharge and recharging many times, maybe this has contributed to having them replaced so many times

or maybe the charger is dodgy

any input ( AC or DC! hahaha! ) will be much appreciated - Dave

 

[Steve Clayton]

From your description it would seem that your 240v source is derived from a 12 to 240v inverter so the load that you are placing on the 240v system is great enough to trip the charging circuit.

Why not rewire the majority of your 240v sockets to run off shore power? (marking which ones are shore power or inverter power).

Doesn't seem right that the boat is going through batteries as you describe. Probably overworking them on discharge and charge routines.

Steve

 

[Evadne]

The charger/batteries/inverter arrangement sounds to me like
a) a convenience to make sure that whatever you do, you are getting your batteries recharged.
b) ensuring that the earthing etc. arrangements are kept simple.
c) ensuring that you don't have 13A mains flying around the boat. Also that the microwave etc. always work whatever the power source. You could, of course, run a 240VAC socket from the shore cable so you can plug directly into the mains when available. This would need to be properly installed so that all the earths were the same and didn't cause problems, and you'd have to change sockets whenever you went onto shore power. But I agree with your sentiments, it would be a lot simpler.

Re. gel cells, I found that using (much smaller ones) on installed equipment that they don't like being left too long between charges, don't like being kept permanently trickle charged and aren't all that keen on being regularly cycled. In other words I wouldn't use them. I did see a graph a few years back comparing different types of battery, their life vs. no. and depth of discharges and if you regularly deep discharge a battery (~50% capacity) it doesn't matter what the construction is, it is not long for this life. Even at ~25% the difference between deep discharge and Halford's specials is not reflected in the price difference.

This is just based on experience, not sound scientific comparison.

 

[DaveNTL]

the sockets are wired for mains voltage Steve, thats the rub

it's going from mains to battery to inverter back to mains voltage - seems daft to me

i wondered if something simple like a wire to a switch when on shore power could provide direct mains to the circuit whilst still topping up the batteries through the charger

i think i have a fair understanding of what is going on, but i'm no electrical whiz and i am going to go and talk to the people who did it once i sort it out in my own head so that they don't try to baffle me with some strange logic / science

thanks - Dave

 

[DaveNTL]

noted Dave, thanks

well, i've got the gels now and will see how they go - as we will be live aboard maybe they'll last longer as the boat has previously been 'winterized' every year and that lack of use, as you say, probably didn't help battery life

 

[Salty John]

I don't think there is anything wrong with your system as far as it goes.
Your inverter does not appear to have a transfer switch to automatically detect when another source of AC is on the line and switch to battery charge mode, or if you have a separate battery charger, to off. So you need to add a 2 pole 3 position switch to select:
Shorepower to sockets
Inverter to sockets
Generator to sockets
This assumes the invertor/battery charger are integrated. If not, it is a bit more complicated because you want to make sure the inverter doesn't feed the battery charger which feeds the batteries which feeds the inverter and finally disappears up its own whatsit, damaging inverter and charger.
The main thing is to be certain that it is not possible to put more than one source of AC onto the line at one time.

 

[ccscott49]

There is an automatic switch system available, I have one fitted, which will switch charger on/inverter off when shorepower or generator is available and power your sockets, but when no mains is available, switches charger off and switches inverter to sockets, I think its made by mastervolt. I bought it in Holland. But its under a bunk now and I cant get at it easily to check.

 

[fireball]

We have shore power and a 300w inverter - but no clever auto switch... but then we've only got 1 double socket at the chart table...

The shorepower terminates in the aft locker with a circuit breaker and 15amp plug.
We can either - plug in the shorepower - powers up the double socket and can run the immersion heater or:
plug in the invertor down by the batteries with short extension cable running up into the aft locker.

At no time can we have shorepower and inverter running at the same time.
KISS

 

[ccscott49]

By the way, batteries should last longer than that. Mine certainly do and I liveaboard, they are also sealed lead/calcium acid, sealed but not gel, much cheaper.