Familiar story indeed
And I have found advice of others on here to be incredibly valuable when I faced similar questions.
First of all, like most boat things, you will have to put aside a realistic budget to do it right. Or better not start. You won't be able to do this for a few hundred bucks.
Second, I suggest you set priorities. Very first I thing I would do is get rid of every incandescent light on the boat, including nav lights. In my opinion it is idiotic to work on increasing capacity before you've rationalized consumption
. The other big consumer is refrigeration
, and if you have a power hog reefer system, you should correct that before going on to supply side questions. "Power hog reefer system" means refrigeration
which uses an air cooled condensor and/or which is poorly insulated. If you have to change it out, I would go for one of those cold plate systems with the controller which freezes the cold plate when system voltage shows there is abundant power. In my opinion the best water-cooled condensor system is the Isotherm
SP which uses direct seawater cooling
of the condensor without a seawater pump.
Next question -- do you need an inverter or not? I don't know how you use your boat, but as I live on mine at least 1/3 of the year, I find the inverter to be absolutely essential. It means you have constant AC power on board to run the household, which for me includes microwave, nespresso machine, kettle, vacuum cleaner, multiple charging
devices for all kinds of electronics
, power tools, etc., etc., etc. Mine is on 24/7 and I have uninterrupted AC power, BUT -- I have battery capacity for that (420 amp/hours x 24v, equivalent to 840 in 12v). You'll have to decide yourself whether an inverter makes sense considering existing or desired AC consumers versus existing or feasibly increased battery capacity.
If you do decide you want an inverter, then I strongly suggest that it should be integrated with the charger. You then get a whole useful world of control over your power, especially, the ability to control the amount of AC power you take from shore power or generator
and to supplement that if necessary with inverted battery power.
On a small boat like yours, you can probably cover any power needed at anchor
or on the mooring
with a Honda
, a cheap
, easy, and convenient power source. Just set it up on the swim platform and run it once or twice a day to charge batts, maybe at the same time you have heavier AC loads. Here the power limit function of a charger/inverter is extremely valuable.
If you decide to stay spartan and do without an inverter, then of course you will save a lot of money
and complexity. Even Victron battery chargers without inverters are cheap; the Sterling ones are also supposed to be good. You will want enough capacity to charge your batts at a reasonable rate, especially if you plan to use a generator of any kind. So the charger should really be 20% C or so; with a smaller bank maybe even 25% C, so maybe 30 amps with your present bank (which I would increase if it's not outrageously inconvenient or expensive, if I were you).
As to busses, panels
, and so forth -- do not skimp. Any weak link in the system will bite you in the butt at some point. Make sure you have a master fuse in the system somewhere -- usually in the negative side of the main battery box
. It will be irritating to have to make an investment into this invisible part of the system, but do it if you have to.
As to battery monitors: I have found the amp-counting kind to be fairly useless for determing state of charge. The shunt which measures the current
for such montors allows them to tell you the momentary consumption
provided there's no charging going on at that moment. This is a somewhat useful datum. But if all you need to know if how much individual items of equipment
consume, you are much better off putting a DC clamp meter on the individual item. So if you decide to forego that type of monitor, you will avoid having to install the shunt, which is a PITA which requires you to cut one of the main battery cables
, and you can use the Smartgauge monitor which analyzes voltage patterns to give a much more accurate estimate of state of charge. I don't have one of these, but I am convinced that this is the superior system for monitoring batteries, after having evolved from a few years of using an amp-counting shunt-type Victron monitor to throwing that away in disgust and moving to analyzing voltage patterns myself by looking at a simple volt meter, which has given me much better results. I am planning to install the Smartgauge when I get around to it. If you go this route
, don't buy it from Balmar
, who sell it with their usual markup; rather buy it VAT-free by mail order from one of the UK distributers. Here is the mfg website: SmartGauge Electronics - Homepage
Don't forget to think about isolation transformers, if you're going to be hooked up to shore power a lot. I have the Victron one; avoid it -- it's crap. At least the one I bought; maybe they've been improved.
power right is very satisfying as it really transforms life on board -- if you spend a lot of time on board and really live. If you don't -- just an occasional night at anchor
or odd weekend in some marina -- then maybe it's really not worth screwing around with too much. Only you can decide that.