Battery charger - what size

[Bertramp]

Hi there ... I have a series 1-45C with Cummins 370 diesels. I have dual 8D batteries per engine (a total of 4) ... I wish to replace my battery charger ... How many amp charger should I purchase. I bought a 40 amp, but the yard is saying that is too light I think original issue was a 40 amp, but I'm 1000 miles from the boat. What size is needed ?
thanks

 

[Boatsb]

How do you use it. I have a 40 amp on 2 x 8d batteries and it is fine. I do not use an inverter much so I do not need a big one for a fast recharge.

let me know what you decide. I may have access to some wholesale.

 

[Capt K]

Steve, I have the same battery setup as you and I still have the original Sentry 40 charger.

I keep looking into replacing it, too.

Let me know if you hear anything different.

Maybe we'll get to see you next Saturday.

K

 

[Bertramp]

I have a generator and no inverter. Aside from running or being anchored out, boat is plugged in. Scott - you mention 2 8Ds .. I have 2 per engine, but batteries should not (there goes that perfect world stuff) never run down to the point of needing a total recharge. Even if a float switch hung up or a light were left on for weeks, the charger should be able to keep the batteries topped off.

 

[Bertramp]

Steve, I have the same battery setup as you and I still have the original Sentry 40 charger.

I keep looking into replacing it, too.

Let me know if you hear anything different.

Maybe we'll get to see you next Saturday.

K

Ken .. I'm back in FLA on Saturday, i thought you guys were thinking friday.

 

[Capt K]

Nick usually winterizes the day after Thanksgiving and we meet for some beers about 6pm, or so in Greenport.

K

 

[Boatsb]

I have 1 8d and 14d on the house bank and 1 8d on the other engine. I find the use of 12V items on the boat will not even challenge the charger. If I anchor out for a day without the genny I have no problems.

 

[fissioneng]

A 40 amp smart charger should be fine. It will actually charge faster/more completely than the old ferroresonant Sentry.

I replaced my 40 amp Sentry with a Xantrex XC 50 amp (they only come in 30 or 50). I have 4 8Ds too.

 

[bostonhatteras]

i replaced the original sentry 40 amp in 2002 with a 40 amp statpower trucharge andhave nothing but good things to say about it. it charges 4 surrette/rolls 8d batteries which also are charged from a pair of 160 amp alternators while underway. it can keep up with any house load. i also have a zantrex ms 2000 inverter (installed this year) that has a 100 amp charger. i shut off the statpower 40 amp charger most of the time becouse the two confuse each other, but if you just want a simple charger the 40 amp is fine

 

[Jaxfishgyd]

I replaced my original charger with the xantrx TrueCharge 40Plus Battery Charger in 2004. At the same time I replaced my 8D's with group 24s. They fit perfectly into the 8D box, a LOT easier to handle and will give you more amps than the 8D.
Have had zero problems with this setup. And I only replaced one 8D on each side so have the rear boxes empty but available should I ever get around to installing an inverter system

 

[REBrueckner]

Bertramp...Your question is like asking "What size engines should I put in my boat?" There is no right or wrong answer unless you specify what you want to accomplish.

Why are you replacing the old 40 Amp charger? If it did the job, as was already posted, a 40 amp smart charger will effectively work faster than a ferroresonant of equal spec. If you don't charge via genny this size is fine.

If you want to charge batteries quickly, say from a genny, then you should size a charger about 20% of your total amp hour rating, for wet cell lead acid, for those batts you use while not running...say 4 8D's at 220 amp hr each; you could charge a maximum of about 20% x 4 x 200 aH or up to about 160 amps...But this also depends on your daily load since you don't want to run batteries down past 50% before recharge.

so the answer depends on what you want to accomplish, your daily load and the type batteries you use. For AGM of equal size, you can double the charge rate to over 300 AMPS.

 

[DickB]

I addressed this in a thread sometime back. I still "don't get it."

When I return from a run, the start batteries are already fully charged. When on the hook, I don't use them for the inverter or other 12V needs. So, when I purchased the new Xantrex 2500 inverter, I hooked the start batteries up to a 16amp output port on the inverter. For the past couple years, it's worked fine. I seem to remember a previous post where someone didn't even bother to have a charger on the start batteries, using my logic.

So, I ask again, why do you need such a large charger for the start side?

Dick

 

[Boatsb]

40 Amps is large? I think the idea of a light left on and a pump running would be enough to justify 40 amps. The start batteries on most of our boats are also house banks.

 

[DickB]

That's likely true for the orig installation. Two 8Ds on one engine, two on the other. Through a switch, one or the other was designated as the house side.

The orig installs also included a parallel selector sw. So, if one bank was down, throw the switch to start the engines, as the other bank was always fully charged.

Most of us now have an inverter/house bank. But, even if you don't, what's the point of having a huge charger on a start bank which never needs it? Call me slow, but I still don't get it.

 

[DickB]

That's likely true for the orig installation. Two 8Ds on one engine, two on the other. Through a switch, one bank or the other was designated as the house side.

The orig installs also included a parallel selector sw. So, if one bank was down, throw the switch to start the engines, as the other bank was always fully charged.

Most of us now have an inverter/house bank. But, even if you don't, what's the point of having a huge charger on a start bank which never needs it? Call me slow, but I still don't get it.

 

[fissioneng]

I agree the "start-only" batteries don't need much to keep them topped off.

This is exactly the reason I chose the Xantrex XC in place of the Sentry. On my boat, the Sentry used the port start/house bank as the control (voltage sensing) bank. When house loads were on, it cycles on and off to keep that bank charged and provide power, BUT it also slugs current/high voltage to the fully charged start-only bank, not good. The Xantrex XC stops all charging to any bank that is fully charged.

 

[rwetherington]

if 40 amp is what the boat come with then the boys at Hatteras most of thought that was more than it needed have you ever seen them do anything just on the border line. Also you would need to change wiring and fuses if you go up or down in size. You know the boys at Hatteras are pretty smart or you would not have wanted to buy one. (Oh that's right I use to work in the Engineering Department did I)

 

[DickB]

I understand that logic, Roger. And I appreciate your long service in designing systems which, even today, are still functional. But it was 40 years ago. Way before inverters or separate house banks. So, here's the real question for you. With the above in mind, what size charger is really required for dedicated start batteries.
Dick

 

[rwetherington]

Dick,

If you are only charging the stbd batteries on a Hatteras because they are the only one that are truely the start batteries. On all Hatteras with two banks of batteries the port bank is the house and the start batteries for the port engine and the stbd batteries run the alarm system, start the generator and are the start batteries for the stbd engine. So if you only want to charge the stbd batteries as the boat come from the factory a 15 amp charger would do it. I thought the question was what charger should be installed on the boat to take care of the hole boat. If there are additional equipment on the boat then you need to do an amp study on the boat to see how many amps the boat draws to size the charger.

 

[REBrueckner]

I conceptually agree with Roger's post about a small charger being fine for JUST start batteries that are not used for other house purposes. But my 1972 YF uses the port batteries to start the genny, not the starboard...and that's original from the look of it. And there ARE other considerations:

If you are away for a long vacation and your big charger conks out...it is sure nice to have backup all ready in place and available. If you are a weekend boater and can make it without much genny charging at anchor, a smaller second charger is fine.

I can charge up to 250 amps at 12volts to to minimize genny run time when away from dockside by using larger chargers...if the start batts are up to full charge most of the charger current goes to the discharged (lower resistance) house battery bank. OR I can switch my house load to "start batteries" to avoid depleting my house bank too far...running two banks down by 30% each is better than running one down 60%....I usually do NOT tie my house and start batts together for long periods...I like to KNOW I have some guaranteed start power available in an emergency...squall, nearby fire, boat drifting down,etc,etc. If you don't anchor out much, or run your genny all the time anyway say for air conditioning, this arrangement would be overkill.