How Big of A Battery Charger

[DJW]

Thinking about updating my battery charger on our 42' Cascade that we keep in HI. I want to install one that will cover 3 banks. I currently have 2 banks (2 6 volt golf cart batteries in each) pluse a stand alone gen set battery. The gen set battery is not currently hooked up to a charger. I start the engine off of one of the 2 banks. What I would like to do is add a 4D battery as my engine start battery/gen set start battery and the power source for a electric windlass (if I install one) and then leave the orther 2 banks just for house batteries. I am looking at the (Xantrex/Schneider True Charge 2 40 Amp) model 804-1240-02 with remote from Defender. Would 40 amps be a big enough charger for this size battery banks? The boat is parked in a slip with 30/50 amp shore power.

Dennis

 

[Bill Roosa]

OK, stuff I have discovered:
the windlass does not use that much power. I have one and it just does not factor into the energy budget due to the very short time it is on. 45 amps times 1 minute (raise the main) would be 45*(1/60) = 9/12 = 3/4 of an AH. Do that 10 times a day (unlikely!) and you have a wapping 7.5 AH consumed. You don't need a separate bank for a winch.
The same argument can be made for the genset (or engine for that matter) start bank. Now if you are concerned that you will not be able to get the genset started due to the house bank being depleted then wire it to the engine start battery. One battery can handle both those jobs.
So what I hear you saying is you have 3 banks of undetermined size. If you can tell us the battery size or model we can help out. Also you are designing a system of loads vs production vs storage. This requires an understanding the loads you see daily, the storage you have and the production you are willing to live with.
There is a spreadsheet in the downloads section that may help. I wrote it so if you have any questions please feel free to email me with questions.

 

[DJW]

Bill

I am not sure of the total amp hour storage on the 2 current banks which are made up of 2 Sam's club 6 volt golf cart batteries hooked up in series to make 12 volts in each bank. The gen set battery is a 12 volt car battery which seems to last 3 or 4 years. We mostly go on day sails out of Pearl Harbor and so we are back in again at the dock with shore power that night. Our son does take the boat on a couple of outter island trips a year and they are out 5-6 days. The big power draw would be the new Vitrifrigo AC/DC 2 drawer refrig/freezer unit that we installed yesterday that draws 4.4 amps per hour. I am not sure what the amp hour storage is on a 4D/8D that I was considering putting in for the engine, gen set and windlass (If I install one) . But even if I do not install the 4D/8D and just keep the 12 volt car battery to start the gen set will a 40 amp charger be large enough to do the 4 6volt golf cart batteries in the 2 banks plus the 12 volt car battery for the gen set. We rarely use the gen set on day sails and on the outter islands trips it is used maybe an hour a day while coffee is being made and the Micro Wave is being used. So as long as I can get the Gen set fired up and I can always recharge to 2 house banks.

Dennis

 

[DJW]

No other thoughts?

Dennis

 

[Maine Sail]

No other thoughts?

Dennis

Don't know why you would have two house banks broken apart. It is better to have one single large house bank for bank longevity and to take advantage of Peukert effect.. That said you have about 450Ah's in house bank. A charger in the 10-20% of capacity range would work and 40A would be fine for dockside use. If you want to charge off the gen set while cruising then you may want to go as large as 100A....

You would be well served to look into the ProMariner ProNautic P or the Sterling ProCharge Ultra chargers. Mastervolt also makes an excellent charger.

I would suggest wiring your house bank as one series / parallel house bank...

 

[DJW]

Main Sail

I would guess the PO had 2 banks to preclude not being able to start the engine and recharge. But if I switched the engine start to on the gen set battery I could wire the 4 6 volt batteries in series / parallel and just have one large bank plus the engine/gen set start battery. Thanks for your thoughts

Dennis

 

[onecoolair]

Now if you are concerned that you will not be able to get the genset started due to the house bank being depleted then wire it to the engine start battery.[/QUOTE]

I did that once the generators alternator smoked my engine alternator!!!!! Was told something to do with dueling alternators ?? Was always told by hunter dealer,panda and company that installed generator that my 6kw panda generator did not have 12 volt alternator....... Only 120 a/c volt output.
Wrong!!!!!!!!!!!!!!!!

 

[Maine Sail]

Now if you are concerned that you will not be able to get the genset started due to the house bank being depleted then wire it to the engine start battery.

I did that once the generators alternator smoked my engine alternator!!!!! Was told something to do with dueling alternators ?? Was always told by hunter dealer,panda and company that installed generator that my 6kw panda generator did not have 12 volt alternator....... Only 120 a/c volt output.
Wrong!!!!!!!!!!!!!!!!

Multiple chargers or alternators properly wired feeding the same source did not cause that... Likely a sudden load disconnect or wiring issue.

 

[onecoolair]

Multiple chargers or alternators properly wired feeding the same source did not cause that... Likely a sudden load disconnect or wiring issue.

Main I would like to agree....But I had to say something as a warning to others to watch out otherwise they my be buying a new engine alternator too!! Plus I am still finding and trying to clean up all the black soot!!
That being said all I know is when I installed new separate start battery for the yanmar I then got the bright idea to let the generator use the same start battery. I started the yanmar to do normal regular warm up, everything was working just fine . Then I got the bright idea to start generator for its regular warm up at the same time...... Started generator , next thing I knew everything went to hell...!!......suddenly I heard strange and scarry sounds and heavy black smoke suddenly came pouring up from down below. Alternator on engine was toasted.
So I now have the generator on its on small optima. And engine on its on start/reserve battery. As per your recommendations... I use the house bank to start engine and start/reserve is just that reserve. Echo charger tops off the reserve while engine is running. New Alternator on yanmar only sees house bank. Generators 12 volt alternator only sees its own separate start battery.
Now everything works just fine.

 

[Maine Sail]

Main I would like to agree....But I had to say something as a warning to others to watch out otherwise they my be buying a new engine alternator too!! Plus I am still finding and trying to clean up all the black soot!!
That being said all I know is when I installed new separate start battery for the yanmar I then got the bright idea to let the generator use the same start battery. I started the yanmar to do normal regular warm up, everything was working just fine . Then I got the bright idea to start generator for its regular warm up at the same time...... Started generator , next thing I knew everything went to hell...!!......suddenly I heard strange and scarry sounds and heavy black smoke suddenly came pouring up from down below. Alternator on engine was toasted.
So I now have the generator on its on small optima. And engine on its on start/reserve battery. As per your recommendations... I use the house bank to start engine and start/reserve is just that reserve. Echo charger tops off the reserve while engine is running. New Alternator on yanmar only sees house bank. Generators 12 volt alternator only sees its own separate start battery.
Now everything works just fine.

Something was miswired. There are tons of boats and motorhomes that share a start battery with a gen set..

In a properly wired system two engines or an engine & gen set can share one start battery without issues..

I have one boat that uses the house bank to start the genset and two huge Volvo diesel engines... Each Volvo has an alternator as does the gen set.. One Volvo has a Balmar regulator programmed .2V higher in absorption mode than the stock alts on the gen set and other engine. In bulk all three alts charge the batteries quickly but as the two dumb regulated alts come up to target voltage they just stop pumping amps and the Balmar regulated alternator takes over for absorption charging..

The way you have it wired now is great but it does not mean two alts can't be used to charge one bank and two motors can't share the same starting battery.