Battery charger not keeping up when AC and Gen are on?

S

Scotto97

Member
Feb 26, 2009
95
Las Vegas
Boat Info
"Wench & Rum" 2007 260 Sundancer, Gen with A/C
Engines
350 Mag
Here in Vegas (Lake Mead) it can be 100 at midnight, so we run the Gen and AC all night. I have the battery charger on (OEM that came with the boat), but my 2 batteries are definitely low in the morning.

With the blidge blower on as well - it's probably a pretty decent load. Could my battery charger not be keeping up with this demand therefor running down the batteries even with the charger on?

BTW - we're not running the fridge or anything else, just the AC including its fan set to "on" all the time, and the blidge blower.
 
Do you have an ampmeter on your converter? If so, what does it say about charge rate? Your converter should be more than able to handle the bilge blower and your anchor light.
You should have a 120VAC or 12 VDC refrigerator, so, it would be operating on 120VAC with the generator running. No need to leave it turned off.

Are switching to just the house battery use when at anchor?

Last year, I did see a boat running its AC and generator in a cove for several hours. When they decided to pull the anchor and leave, they shut off the generator only to find out that their batteries were too low to start the motors.
 
I have a Guest 10/20 AMP charger that came with the boat. 10 Amps per Battery, 20 Amps total. No anchor light is on since we are on the beach. Only the AC compressor (With the AC fan set to always on) and the bildge blower is on. We Don't use the fridge.

The charger only has 2 indicator lights per side, green when charged and red when charging.

I'm turning the battery selector switch to "Both" when running the gen and battery charger - not sure it the batteries will both charge if it was only selected to one or the other.
 
Both batteries will charge even if only one is selected. The converter is wired to the batteries before the battery switch.
What is your DC voltage reading on your dash voltmeter when beached? Are both of your batteries good?
 
I may be missing something but why would your AC run down your batteries? It will only run on 120ac and that is supplied form the genny. It has nothing to do with DC voltage coming form your batteries.
 
Bucit said:
I may be missing something but why would your AC run down your batteries? It will only run on 120ac and that is supplied form the genny. It has nothing to do with DC voltage coming form your batteries.
Click to expand...

Agreed - thanks for pointing that out

Since my battery charger is very weak (10 amps) could the bildge blower exceed this and result in a negative drain over the 8 plus hours it's on overnight?
 
Batteries are less than 4 months old. Boat is trailered with the battery switch off and used every couple of weeks for weekend trips. (Not plugged into AC while in storage) Engine is usually on for only 30 minutes or so before we beach however. When we launched last friday the batteries were reading 12.3 volts and almost 14 when engine was operating.

Charger is on all night while gen is operating, but still batteries are low in the morning, By Sunday morning they were almost incapable of starting the engine. This is after 2 nights of the gen and battery charger being on all nigh - but both are off during the day with no frig and maybe a couple of hours stereo usage.
 
I have asked in another thread in cruisers about my A/C problem. The A/C water pump would not flow enough when on only dock power. when i turned on the engines the flow went way up and A/C ran find. i discovered my converter was not working. i dont really know how to trace the wiring but am wondering if the A/C water pump runs off DC power.this would explain in my case why the pump was low flow since converter didnt work at all and the batteries were weak. If this pump is DC maybe it contributed to your batteries wearing down if your converter doesnt keep up? Of course my theory is blown if the pump in on AC power.
 
I just checked my CruiseAir manual and verified the water pump doesn't run off the battery, so in at least my case it should not be draining the batteries while operating.


That only leaves the bilge blower and from what I've researched, it shouldn't be taking over the 10 Amps my charger can supply
 
The only DC draw that has been pointed out is the bilge blower motor. Since you have stated that your batteries are only four months old, I would have to question whether the convertor is operating properly. What is your voltage reading when you are running the generator and the bilge blower? A bilge blower motor draws about 3 or 4 amps.
 
Last edited:
cod said:
You need to check to see if the alternator on your generator is charging......
Click to expand...

The generator puts out 120-VAC, there is no alternator.
 
Not true.... A generator is made up up of 2 very different components. There is an engine that runs just like any other engine that works off a 12 volt system which turns a generator to produce 120 volt......
 
The OP is talking about a possible problem relating to the convertor which is provided 120VAC by the generator. He is not talking about the engine part of the generator.
The OP is not indicating that there is any problem with the generator since his AC seems to be working fine. He does not have a separate battery for starting the generator. The batteries that he is talking about are his main starting battery and a house battery, both of which would receive a charge from the converter when the generator is running.
 
Last edited:
10 Amps at 12 volts is 120 watts which is not very much. I assume you are running a couple lights inside? What's the wattage of your stereo?

I had to replace/upgrade my 50A charger that came with the 480 DB because I added some 12v gizmos and the house battery would be dead in the morning with the charger turned on. I also saw that the wattage on the lights was "20 watts" but Sea Ray put in 10 watts bulbs... I thought "those cheap bastards" and replaced the halogens with 20 watt bulbs... brightened the place up with the gazillion lights but deadened the batteries. The front stateroom and head alone drew 20 amps when the lights came on.

Also, if you've deadened the batteries a couple times and they are wet cells, it doesn't matter how old they are... They may be weakened at best and destroyed at worst and won't hold a charge anymore.
 
Last edited:
Also with that type of battery charger, the lights do not always mean they are charging. Check the output wires from the charger to batteries for an inline glass type fuse. Each side has one usually several inches from the battery connection. That charger is almost just enough to be a "maintainer" not a for everyday use.
 
floriduramax1 said:
Also with that type of battery charger, the lights do not always mean they are charging. Check the output wires from the charger to batteries for an inline glass type fuse. Each side has one usually several inches from the battery connection. That charger is almost just enough to be a "maintainer" not a for everyday use.
Click to expand...

Agreed, and since he does not have an amp meter on the charger, that is why I am telling him to tell us what the voltage reading is when he has the boat beached and is running just the generator, AC and bilge blower.
 
JerryS said:
The OP is talking about a possible problem relating to the convertor which is provided 120VAC by the generator. He is not talking about the engine part of the generator.
The OP is not indicating that there is any problem with the generator since his AC seems to be working fine. He does not have a separate battery for starting the generator. The batteries that he is talking about are his main starting battery and a house battery, both of which would receive a charge from the converter when the generator is running.
Click to expand...

He is talking about a "possible " problem with the converter but does not know if that is in fact the problem my CSR friend...... If the generator has its own battery, then yes, I would agree that the alternator on the generator is not the problem. However, it is possible the generator uses the same battery bank that is used to start the main engines. If that is the case, the generator would be a draw on the batteries as it is running if it's alternator is not charging. I am providing a possible avenue to investigate. To make a statement that the generator does not have an alternator because it produces 120 v is completely wrong because one has absolutely nothing to do with the other. The manufacturer doesn't assume that there will be a separate battery charger wherever their equipment is going to be installed. It requires a 12 volt battery to start it and they provide a means to charge that 12 volt battery via ,an alternator. The engine part of the generator operates on a 12 volt system. The engine is used to turn a generator to produce electrical energy of 120 volts. The 120 volts is the power supply for the converter along with any other 120 volt equipment on the vessel.
 
It is entirely possible that the genny is draining the batterys. Most larger engines have some type of method to sustain power w/o draining the batteries. Eventually the batteries will die. While possible not, i would have to agree the gennerator does have an alternator. I would suspect the alternator (or inductive charging system) on the genny is bad, thus pulling more power from the batteries than the charger can replace.

I would suggest leaving the Batt selector to 1 battery only. The second battery will charge if your charger is hooked up correctly.

I would speculate that the genny will cut off in the middle of the night as you just reduced the reserve capacity by 1/2 by using one battery. Which leads me to believe the genny is just sucking battery power and not replacing it on its own.
 
You must log in or register to reply here.

Forum statistics

Threads
113,187
Messages
1,428,227
Members
61,099
Latest member
Lorenzo512
Back
Top