Batteries... the best way to charge??

[Brent]

I have followed various threads on the forum regarding this subject, visited numerous sites dealing with charging systems. My knowledge is better now but …. Not clear enough to allow me to go forward with confidence. I bought our current boat last year and she needs TLC. Battery area is a disaster, having a generator to change the domestic batteries. The genny is u/s and I want a greener solution. Current alternator changes the cranker/domestic, it’s a 90 amp job (I did say it’s a disaster) /forums/images/graemlins/frown.gif. There is a 800 amp hr domestic battery bank connected to a good 230 ac shore powered system when in the berth. I want to fit a second alternator plus either solar panels/wind generator to allow long periods of independent sailing. Any advice on the best way forward will be very gratefully received.

 

[oldsaltoz]

Adding a second second alternator will produce more amps than your charging system will allow to the batteries.

Wind generators can be very noisy and hazardous.

Adding solar panels will help but a system that charges the engine battery first when the 90 amp alternator is running, combined with a voltage sensitive relay will mean the domestic bank will start charging as the starter battery/s get closer to capacity. Use the solar panels to top up the domestic batteries and have a change over switch to divert the flow to the engine battery if you need it at some stage.

A smart regulator will also help boost the output of the alternator when needed.

Also a good idea to have a switch so that domestic batteries can be used to crank the engine in an emergency.

I hope this helps.

Avagoodweekend......

 

[mdrifter]

A second alternator sounds a good idea along with an Adverc BMS (twin alternator model). If it was originally fitted it might also be worthwhile replacing/refurbishing the generator. No solar panel and/or wind generator and/or water generator system will be as effective as either engine or generator charging system when away from shore power, imho...Another idea might be a prop shaft generator driven by the prop when sailing...

 

[Brent]

Thanks for the reply's .. as for the original genny, its been removed and due to a previous "maintenance man" lost!! He no longer looks after the boat! I agree wind generator is noisy... Med is sunny therefore solar looks more likely so long as I errect a s/steel arch at the back of the boat to mount it.

I thought a second alternator of 150 amp hrs - ish would be a good way foreward... but your replies appear to suggest otherwise. What management systems would need to be installed to manage the sytem effectively. Would a voltage sensitive relay and the aid of a battery monitor sensing/measuring amps being used, amps put back into battery, state of battery bank as a percentage, also time remaining before recharging be the best way forward.

 

[jeremyshaw]

I second oldsaltoz's advice. Mdrifter says that solar/wind will not be as effective as an alternator or generator. This is true in the sense that an alternator will put in more amps more quickly, but unless you want to run the engine for hours (and are using one with a sophisticated regulator) they will never get the batteries fully charged. Only solar or wind has the ability to put a modest charge in for hours on end. Given your location in Mallorca, I'd put in as much solar as possible.

We have a genset and solar panels and I find this combination works well in the Caribbean which has similar sunshine to the Med, where we started. Friends recently put in solar (they already had the generator) and said "wish we'd done it years ago, we've halved our generator hours." Note halved, not axed.

You need to balance all this up with other reasons for running the engine (maybe hot water?). And of course if you can increase the bank that helps too - I upped mine from 640amh to over 1000 in almost the same floor space by switching to Trojans.

Again I agree with oldsaltoz that a 90amp alternator is fine. I only have 55amp and over 1000amh of bank, but I rarely find the batteries accept more than 30amps, since, like most people, I try to keep them above 12.2v (bog standard regulator, it's true). So after about an hour of charge I can't get in more than 10amps at which point it's silly running an engine when my panels can kick in 8amps in decent sunshine.

A tilting solar array can make a big difference too. I can't be bothered and as we have a cat we can have a big array anyway. But I helped someone rig their tilting array recently and we worked out that come about 3:30pm we could double the rate of charge over having the panels flat. So if you are up for tilting your panels morning, noon and night, that will help (depending on how you are facing of course).

Towed arrays are of course much more effective than wind or solar - but only when you are making way; and then they can be a hassle to manage (pace Duogen). You can work out yourself the likely input you'd get from wind/towed/solar depending on your location and cruising plans, but I'd suspect solar would be best in your location.

Solar also has the advantage of trickle charging the batteries when you are away - and I see from your profile you are not a full time liveaboard - yet! This means you don't have to be on shorepower when leaving the boat, which can only be a good thing.

So I'd go for the biggest solar array you can, but accept you'll still have to run the engine sometimes.

 

[mcframe]

S L O W L Y

Oh, and don't forget to keep some dehumidifier-water to top 'em up.

 

[Brent]

Thanks so much for a very informative reply. It's norrowed my options greatly and given direction.

 

[Brent]

Cheers sport!! Thanks for the info.

 

[William_H]

I think a lot depends on how much money you want to spend and how much power you want when away from marina/shore power.

A basic system of engine generator with VSR to charge domestic batteries or a smart charger with battery sensing or dual battery provision should really suffice.

If you have plenty of sun then solar may be useful but really they are a lot of trouble to mount and quite costly. Likewise wind generators.

I reckon you should go with the engine driven gen (alternator) the 90 amp should be OK or bigger if you have to buy a new one.

Just see how you go in actual use over a season. You may find you are not running the engine very much for battery charging only and on the odd occasions you have to it will be a lot cheaper than solar/ wind.
If you are a bit savvy on power consumption you will know how the batteries are going but if not then a battery monitor use/ charge totalisor my be useful.

I really fear solar arrays and wind gens on boats are becoming a bit like big 4wheel drive vehicles in inner city. More of a claim the owner being a great voyager than actual practical use.

Keep it simple........ olewill