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KevinLenard's picture
KevinLenard
Last seen: 1 day 12 hours ago
Joined: 1/28/15
Posts: 138
Battery Charging While Underway

Forgive my ignorance on the subject of 12 volt charging, but I want to be sure that I've been doing the right things to treat our batteries well. 

After our recent grounding/extraction I noticed that the original 28 year old 20 amp (not-so-smart, always-on), 2 bank charger was humming loudly and damaged some vinyl items down the stern lazarette due to heat, so I decided to replace it with a smart 3 bank charger by Xantrex and added the temperature warning attachment and the remote read-out unit (see photos, note: I added a 4" square vent in the foreward, outboard-most wall of that under-seat cubby to release the heat of the charger fan/heat sink -- VERY quiet).  After a 1.5 hour trip under power with all three batteries turned on to start and while underway, once back at the dock all three were showing as charging, while I had naively expected the alternator to have topped them up to replace the energy I'd used to heat the glow plugs.  Clearly my expectations were incorrect, hence these questions:

  1. Is it the case that, unless the switch is set to "ALL" and the independent starter battery is also switched on (all three batteries are then being used to start the engine and are under some load while underway from the USB power to the phones, instruments, the Admiral using the water pump, etc.), that the alternator is NOT charging them while underway?  (i.e. The batteries will not get charged while the motor is running if they are not turned on at the switches.)
  2. I believe I've read a warning that, once the engine is started, the battery switches should not be turned on or off.  If this is the case, what damage can be done by doing so?
  3. If I am doing the right thing in order to charge the batteries while underway by turning them all on (I realize that this is not necessary, but if #2 is true and I do not switch the starter battery off and turn the house batteries on once the engine is started, then we would be tapping into the starter battery and alternator for any load while underway), then how long, theoretically, would it take before all are back to fully charged by the alternator (seems to reliably output 14+ volts)?

We regularly cross Lake Ontario by motor (5 to 8 hours, depending on the destination) and, after early disasters while we were brand new to the boat with the two batteries dead and no backup or generator available, I am a tad paranoid about making sure the batteries are as well charged as possible.  Any feedback would be appreciated!
 

Kevin Lenard
"Firefly"
'91 C-36 Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Ontario, Canada

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Kevin Lenard
"Firefly"
'91 C-36 Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Ontario, Canada

Haro's picture
Haro
Last seen: 1 hour 48 min ago
Joined: 11/7/14
Posts: 250

The starter battery should be directly connected to the alternator with only a separate disconnect switch on the battery cable in case of an emergency. That means the starter battery will charge when the engine is running.
Before you start the engine the house switch should be on ALL. Then start the engine. The alternator will charge all batteries. While sailing, after the engine is turned off, place the house switch on 1 or 2, this will disconnected the starter battery and only house batteries will be providing power, the starter battery will remain fully charged and reserved to start the engine.
While sailing, when you are ready to turn on the engine, place the house switch to ALL then start the engine. The alternator will charge all 3 batteries.
If your house batteries have depleated so much that brings down the starter battery voltage and the engine will not turn over, you must disconnect the house batteries and start the engine. At this point you are out of luck and can not charge the house batteries. If you switch to ALL while engine is running and alternator is generating current, the diodes inside the alternator will be damaged.
You will have to wait until shore Power is available to charge the house batteries.
To prevent this, check your house batteries periodically and turn on the engine to charge them up.

KevinLenard's picture
KevinLenard
Last seen: 1 day 12 hours ago
Joined: 1/28/15
Posts: 138

Thank you, Haro!  So I have been turning the starter battery switch on before starting the engine, as well as switching the double house bank to ALL, then turning the starter switch off upon arrival, but it only needs to be switched off in an emergency, OK.  Then the only load on the starter battery will be the bilge pump when the ignition is off. 

I'm assuming that 1 hour of run time is insufficient to replace the energy lost in heating the glowplugs from all three batteries.  I'll monitor to see if all three top up on a longer run. 

--

Kevin Lenard
"Firefly"
'91 C-36 Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Ontario, Canada

Chachere's picture
Chachere
Last seen: 9 hours 20 min ago
Joined: 10/27/10
Posts: 608

This seems a bit confusing from reading this the above.  I'm not clear whether you have are set up with:
   a) 3 wholly independant batteries -- consisting of 2 batteries each used as separate a "house" battery (one connected to #1 on the switch, once connected to #2 on the switch) and a separate  start battery with its own switch?
or, is it
    b) 3 batteries -- but consisting of 2 house batteries wired in parallel as a single "house bank and connected to #1 on the switch, and 1 starter battery nnected to #2 on the switch (or vice versa).
 or 
   c) a different setup altogether.

It might be helpful to first draw up a schematic of your wiring scheme -- it will be clearer to you and us.

 
This is particularly so because in many of our boats the previous owners at some point changed the original configuration of the battery and charging wiring, so its somewhat fraught for the rest of us to suggest a "one size fits all"  answer to your question.

There have been several threads that have discussed this, such as:
https://www.catalina36.org/forum/technical-discussion/starting-battery-revisited
https://www.catalina36.org/forum/technical-discussion/battery-compartment-wiring

The wiring setups some members have devised (as described in those threads) essentially make this fairly automatic and space-out proof, particularly if the alternator output is wired directly to the house bank and the starter battery get its charge via an Automatic Combiner Relay -- on our boat, we don't have to touch any of the battery switches all season.

Lastly -- although this is a quick back-of-the envelope calculation  -- I can't imagine that, as you say, "1 hour of run time is insufficient to replace the energy lost in heating the glowplugs from all three batteries."  While glow plugs do use some amps -- apparently about 13 amps each, or a total of around 40 amps on a 3 cyl diesel -- you use them for no more than a minute, which would be about 0.7 amp hours.  Your alternator should be able to replace that in a minute or two. 

 

--

Matthew Chachère
s/v ¡Que Chévere! #466
1985 C36 MKI tall rig fin keel M25
Homeported in eastern Long Island, NY

KevinLenard's picture
KevinLenard
Last seen: 1 day 12 hours ago
Joined: 1/28/15
Posts: 138

Thanks for taking the time to offer this more detailed overview, Mathew.  I am now going to do a more thorough examination to ensure I haven't messed things up!

  1. I believe that we have the original set-up for the house batteries, with #1 and #2 wired via a negative from the alternator shared across them and the positive wires going up to the main battery switch. 
  2. I have removed the original charger and pulled the cables back up to the panel, then redirected them down to the battery cubby in order to attach them to the new Xantrex charger.  I followed the instructions for wiring it and it seems to be working well, including the temperature sensor and the remote read-out.  The charging function says it is not drawing full power to charge and the batteries show fully charged after a couple of hours and remain fully charged even while running the fridge and cabin lights, stereo and miscellaneous.  I do switch the house switch from 1 to 2 once a day to share out the draw.
  3. I added a third battery which I wired through a single on/off battery switch to the central post on the main switch and I have the bilge pump wire on the live post of the switch. 
  4. Note that the PO had the VHF positive wire also on the central post.  I'm assuming to ensure it is powered no matter what how the switch is set.
  5. I also have two flexible solar panels at 100 watts each wired into the system that are on top of the bimini and dodger.

What prompted me to post this enquiry was the fact that the remote read-out unit now installed next to the panel shows that, even after 1 hour of running the alternator/engine after starting the engine with all three batteries with the sun shining on the solar panels (for what that's worth), back at the dock the Xantrex remote unit shows all three being charged for more than an hour on the 120 volt shore power.  This led me to believe that either I have not been providing power from the alternator to the batteries while underway, or there is a problem with the alternator output.  The gauge reads 14+ volts while the engine is operating, but maybe I have a wiring issue.

I will use the volt meter to re-check the voltage at the switch and negative feed while the motor is on and off, plus I wil re-check all of the wiring to ensure I haven't missed something.  I have a battery tester and, while none of the now 1 to 2 year old standard 12 v batteries is new and put out the full amperage, they show OK on the meter.  

  1. Is it possible that, if the starter battery (#3) is a standard non-sealed and the house batteries are AGM that this is causing a problem when all three are interconnected?
  2. Is it possible that, if the starter battery is not holding full charge, despite the Xantrex read-out saying it is, that this is 'pulling down' the other two even while the alternator is working?
     
--

Kevin Lenard
"Firefly"
'91 C-36 Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Ontario, Canada

Haro's picture
Haro
Last seen: 1 hour 48 min ago
Joined: 11/7/14
Posts: 250

I failed to clarify that my 2 4D wet cell batteries are parallel together as #1 and stared battery is #2. Since alternator charging output is directly connected to starter battery, the switch must be placed on ALL in order to charge the house batteries aswell when engine is running. There should be no device connected to starter battery when engine is off, otherwise it defeats the definition of reserved starter battery.

pkeyser's picture
pkeyser
Last seen: 2 hours 20 min ago
Joined: 5/18/13
Posts: 407

Kevin-
I think given the ownership changes of most of our boats have had electrical modifications since leaving the factory. 

I've read it's not a good idea to combine AGM and lead acid batteries. You might want to do some more research on that.

I think if you isolate the batteries and take a volt meter reading of each before, and after just running the engine, and then again a day or so later after some rest period, you'll get some insight as to the health of each battery. Below 12V after a period of rest is a problem. All should be showing higher than 12V immediately after charging. 

You can aslo play around with an ammeter to check for current leaks while reattaching the cables.

I have Xantrex monitor on our boat. It's from 2005 and complicated to use all the functions for us non electrcal engineer types. It has four LEDs showing the health of each house battery (all four glowing and good to go)-that's the easy part for me to understand. That said, I had a battery with a bad cell that wouldn't hold a charge (per the volt meter reading), but showed up ok with the Xantrex. 

You may also want to check if a battery combiner was added to your charging system to combine the house bank and starter batteries when charging from the engine.

--

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

Chachere's picture
Chachere
Last seen: 9 hours 20 min ago
Joined: 10/27/10
Posts: 608

OK, so you've confirmed -- as I had suspected -- that this is no longer the factory original wiring set-up.  
So again, I think doing up a sketch / schematic of your wiring will help clarify for you -- and us -- and understanding of how your current system is (or is not) working.
As they say, a picture is worth a thousand words; otherwise its very hard to visualize all the variables in your current set-up from your written description  Attached is the one I drew up a few years ago for our boat (we later added polar panels, which are not indicated but are wired in parallel to the charger).

I also think that a battery monitor (rather than a volt meter) may be helpful to understanding what's going on in terms of understanding the actual state of charge ("SOC") of your various batteries.  Checking with a voltage meter, on the other hand, can be problematic for a whole host of reasons, including that there could be various sources of both charge and discharge going on that are not accounted for, or that you often need to wait some time to ascertain the actual "resting charge" of a battery.
Mainesail (former C36 owner) has a website with lots of good info on this:. https://marinehowto.com/installing-a-battery-monitor/ 

I should mention that even when we've been motoring for a while (and the sun has been shining brightly all day on our panels), when we pull back in to the slip and plug back in the shorepower, our charger (we installed, from Mainesail's recommendation, a Procharger Ultra a few years ago when the old one died) will start whirring away and charging, even though the battery monitor does show we are at 100% SOC.  I assume this may be something in the charger's programming, but wiser minds here may have a better explanation.
 

Attachments
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Matthew Chachère
s/v ¡Que Chévere! #466
1985 C36 MKI tall rig fin keel M25
Homeported in eastern Long Island, NY

KevinLenard's picture
KevinLenard
Last seen: 1 day 12 hours ago
Joined: 1/28/15
Posts: 138

HUGE thanks for all the input!  I have now gone over the wiring in detail and I have isolated and checked voltage after many days of the 3 batteries being on the Xantrex charger.  The unsealed 'car battery is at 12.95 v, the other two AGMs at 13.45 and 13.25 v.  Seems the batteries are OK, althought the 'car battery' that I am using as the reserve/starter battery might need replacing next season.  I have gone over Mathew's diagram and those of MaineSail from the links on the forum and I will rewire as shown to improve the set-up, using the 1/2/B switch to isolate the house from starter.  I have ordered a VSR on Amazon and will add that into the mix. 

Until I went through the wiring diagram (and still had the 1/2/B switch wired as original -- one AGM on #1, the other on #2) I was concerned that leaving the reserve/starter battery's isolator switch turned ON constantly would drain it due to the fact it would be constantly used as an additional house battery (attched to the C post).  Now I get what you were talking about -- it needs to be isolated from the house AND adding the VSR/ACR will ensure it still gets topped up while on shore power/charger. 

LAST QUESTION (Ha!  There are always more questions...):  if I wire the two AGM house batteries in parrallel, what happens with the wiring of the Xantrex 3 bank charger?  With a wire connecting across the #1 and #2 positive posts, does this not risk 'confusing' the Xantrex monitor read-out, or worse shorting the charger out internally?  Do I simply disconnect and forget about using the #2 wire from the charger, or should I add a switch in the new positive connection wire to occasionally isolate the two batteries to read the monitor's report on their individual condition?

--

Kevin Lenard
"Firefly"
'91 C-36 Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Ontario, Canada

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