Hi. I'm in the process of buying a cat to live on for the foreseeable future and I need some advise on battery power. It's a crowther 36 and it has 440 watts of solar, no wind but the engine has a hundred watt alternator. The couple that own it have lived on board for thirteen years but at a marina using shore power. It has a TV and set top box but he said they don't run well off the batteries (4 X 6 volt deep cycle house batteries [2 banks of two]). Now It has a good built in fridge/freezer but apart from that and lights, there's not much to draw power.So why won't the tv run well? This is important as if I'm going to live on it there are only a couple of things I need and TV is one of them (it raised me). I know I can get a little generator but then there's noise and fuel and blah blah. If I swapped out the batteries with deep cycle 105amp or better 12V batteries, would that fix the problem? Or should I add another bank of 2 X 6 volts? There's plenty of room for either of these options. Any thoughts or ideas would be appreciated.
Peter

But that's the thing that confuses me because it IS a marine flatscreen lcd tv (Maestro ro Majestic or something liek that) with a tiny marine set top box! For simplicity I was thinking about replacing it with one of the new Teac LCDV2257DVR lcd flatscreens as they have built in dvd, hi def box, and usb (straight to external hard drive or big usb stick) recording. That ticks all the boxes I need in one unit. Just trying to find out the AMP draw now. I think I'm going to need morre battery power no matter how I slice it.
Thanks for the response.

440 watts is heaps although u haven't stated what type of motors it has and also is the anchor windlass electric and how much does it draw ??

drpete said...

Yeah I thought that was plenty of solar too. It does have a big built in fridge freezer though which is set up very efficiently but still must suck a bit of power. It does have a windlass but I would only ever use that while motoring up onto it so the 100amp alternator on the engine (22hp Yanmar) would be powering that anyway. Thanks for your help.

Every thing that rotates will have a heavy draw, fridge compressor especially each time it starts a cycle. Set top box if it has a hard drive. Computer hard drive too. Obviously the main engine will be running if your using a windlass. Having a separate battery for the windlass close by is a good idea.

Remember that the 100 amp alternator will only generate that sort of current for a short time after engine start up unless it has a "manual" controller. The set up is similar to a car, once the engine is started the alternator puts back current to the battery initially then cuts back to about 5 to 20 amps or so after about 5 minutes.

There is an excellent book called "The 12v Bible", your library would probably have it.

I guess, you have enough amp coming IN and storage that you can consider to start selling some.
Seriously ones you can measure the real amps IN and Out than I can help you.
Now we can estimate 250-350 amps IN when is clear sky. You must limit constant draw somewhere around 8 amp.
Than you have plenty for the most of small things. For big ones you run the engine.
Only my suggestion, think what about a few cloudy days. Little Honda Gen. or main engine.

garyk said...

Charriot said...


Now we can estimate 250-350 amps IN when is clear sky.

Did you mean 25-35 amps

I think he meant 250 to 350 watts from the solar panel and daily usage of 8 amps. 440 watt solar panel is roughly 36 amps at 12 volts, that's a lot of energy.

Hi Pete - when i lived aboard a cat i found the most useful part of the electrical system was a battery monitor which gave a digital readout of current (amps) entering or leaving the battery. It was so accurate you could see the incoming current reduce when a cloud shaded the solar panel or even if the boat turned at anchor and the boom caused partial shade. It also gave state of charge as a percentage. This effectively gave the house batteries a personality with which you could judge when or if attention to charging was needed. You don't need large house batteries if regular and/or multiple charging is present. It just takes a little bit longer for them to go flat! Connections are critical as is oversize, tinned wire to every component - especially the solar panels - replace all lights with led type - especially the anchor light! (put a reminder to turn it off too). I had a honda generator which was fantastic - they give peace of mind. Also critical is a LARGE modern marine battery charger (minimum 30 amps - honda 10 will run up to 40 amp charger) It is also possible to start some engines manually (with a rope) if batteries go flat for any reason. Investigate if this is possible and practice - Saved a yacht of mine from certain death. Cheers

hey testicle pilot 1 - basic advice is not helpful and fully discharging lead acid batteries is just plain wrong (that applies to nickel/cadmium batteries u idiot) Please do not post any further electrical advice as u do not have the understanding or legal qualifications to do so and thats good advice!

By the way, I did not say to fully discharge any battery. On a single cell that would be ok, but as we both know discharging a series of cells does not discharge them evenly and in fully discharging said sereis can result in some not discarging fully and possibly some even reverse charging. Result lowered out put voltage. Even these batteries can be sometimes be revived by pulse charging each cell seperately,as would be done for telecommunication back up supply cells. These too develop memory effects but I digress.

Thanx charriot - some guys insist on making 12v dc systems harder to understand than what they really are... I am (by luck rather than design) a qualified mechanic and later a qualified electrical contractor so have been trained in dc, ac and electronics. I have also worked alongside the Principal Electrical Licensing Officer of Queensland. Telling people to clean bird**** off their solar panels is an insult and an insight to the poster... Legislation prohibits electrical advice to be given but I digress.

With some difficulty - a vic dr licence will convert to qld restricted depending on what qual u had/have - print requirements off qld gov website. Application does not always give desired result! Worth a go only if u need it for your employment. Note from employer is another pre - req i think...as is a current first aid and id.
bullet points mmm - wud send them to the unqualified rubbish authors who annoy me on here .