36 Tri cabin Battery Charger

[tpd777]

Hello,

Can someone explain why the generator starting battery is not connected to the battery charger on a 1985 tri cabin. My generator will not charge the battery even though I replaced the diode. Can I safely charge the generator battery with the on-board charger and shore power if the generator is not running?
I have a 35amp 3 bank 20amp power supply/charger.

Thanks

[prowlersfish]

I don't see any reason why not

[WayWeGo]

I have a 30A 3-bank charger and one bank is connected to the generator battery. Works fine.

[rickalan35]

TPD777

Like your situation, the stock charger (if indeed it was stock instead of just old) was not connected to the single generator battery when I purchased the boat.

I used to begin the season by bringing my portable car charger to the boat and leaving it on for a day in order to start off with a fully charged battery.

When the generator was running it did indeed charge its own battery. So you should be able to successfully address that issue.

In my experience, it's common to find that the generator battery is not added to the charger. Sometimes I think this oversight may be due to the manufacturer simply not bothering to go to the added expense. Two salesmen that I've asked have had identical responses, "Oh, you just run the generator for twenty minutes and the battery's charged." So I believe we shouldn't underestimate a poor design from the manufacturer. For instance, I believe that Carver (they built my current 1994 Trojan 370 express) did a very second rate job of designing the wiring of the batteries in this model straight from the factory.

Regardless, in my former TriCabin when I replaced the old charger with a new three bank smart charger, I added the generator battery as the third bank and there were no problems.

Rick

p.s. I added sound dampening material to the hatch and it did lower the generator noise volume enough, enough that we thought it worthwhile.

[tpd777]

Thanks for the replies.

Rick, The reason I asked is because an Onan generator technician told me that the 35 amp charger could damage the generator’s electric fuel pump and electric choke if charged with genset operating. I believe the 6.5 MCCK only charges it’s own battery at 3 amps. I have AGM Batterys that need to occasionally reach 14.1volts during the smart charging cycle to maximize battery life. You say that you have connected your smart charger to the genset battery while the genset is running and also charging it’s own battery at the same time?

Tom

[rickalan35]

Tom,

Sorry for misleading you. My apologies.

Nope, I didn't ever run the generator while the boat itself was connected to shore power. Not for any particular reason, it's just that with the shore power on we didn't need the services of the generator. But if we had done so, I assume that the "smart" charger would have been able to discern the level of charging volts going to the generator battery and subsequently modulate it.

During the final years that I owned the TriCabin with the new charger installed, I would leave the boat at the marina for sometimes a week at a time. During those absences the shore power would be connected and thus the battery charger would be operational and maintaining the batteries (generator included). The unit always ran great and I assume that the battery charger did not damage the electric fuel pump or electric choke. But possibly the Kohler didn't have those features (Prowler will know the answer to that)

I would only fire up the generator when and if I required power while out on the water anchored.

On another note, I had been informed by the mechanic at the marina that it was a bad idea to operate my TriCabin's generator while underway. He claimed that the shape of the water intake was such that the Kohler didn't receive enough water if run while underway. So I never did. I just didn't want to take a chance and so I only ran it only while stopped, which suited my purposes fine.

Hope this clears up any misunderstanding. Thanks

Rick

[tpd777]

Rick,

Thanks for the clarification. Electrical is probably my weakest area when it comes to DIY maintenance. I am still confused by what the Onan guy told me about the genset charging. Maybe Trojan left the generator battery off of the charger for this reason. When I am away from shore power with the generator running, the 3 bank charger is being powered and is charging the engine/house batteries. If the generator battery was connected, it would be getting charged by the 3 bank charger and its own power at the same time. I guess my question is should a battery be charged by different chargers at the same time. One 35amp and one 3amp source. Clear as mud.

Tom

[WayWeGo]

I have never run the generator and the battery charger at the same time, so take this with a grain of salt.

You should not have two chargers trying charge the same battery unless you know exactly what the effect of this will be on the chargers and the battery.

That said, I am a bit unsure why the Onan tech was worried about the electric fuel pump and choke. The fuel pump should be fine with 14+ volts as it is most likely an automotive type that typically sees that voltage. Same with the choke, where the resistive element will control the current, so a higher capacity charger should not make any difference. I would have been more worried about damage to the generators charging circuit itself.

Our F-36 came with a Bomar magnetic core 15A charger that did not have any smarts, so it was not a good choice for the AGM batteries that the previous owner installed. Not sure why he put expensive Rolls AGM batteries in without installing a charger that was appropriate for them.

[rickalan35]

I thought I was being perfectly clear here.

Take this with a grain of salt!!! What the hell are you talking about Way We Go???

I never fired up my Kohler Generator (my 6.5 single cylinder gasoline engine generator) while the boat was connected to shore power. What part of that statement is confusing to you two guys??

Why would anyone try to charge their generator battery while the generator was running??

[kallen]

Do not forget the transfer switch. So even with the genny running at the same time as shore power. The power will only be from one source. If you have a smart charger it should adjust the voltage to the genny battery. The amp output of the genny to charge the battery is really low.

[rickalan35]

I think I'll just go kill myself.

[tpd777]

Rick

"I never fired up my Kohler Generator (my 6.5 single cylinder gasoline engine generator) while the boat was connected to shore power. What part of that statement is confusing to you two guys??"

why would anyone "never" fire up the generator while the boat was connected to shore power? I always fire up my Onan generator before I switch over from shore power. I don't leave the slip without an operating generator. Sorry, but I must not have explained my problem clearly. In the original post I stated that my generator does not charge its battery. The generator DC charge function for the battery does not work. Not sure why. I replaced a diode that the Onan tech thought would fix it but it did not. This is why someone might want to charge their generator battery while the generator is running. The generator is not doing it. Also, I have AGM batteries that should be charged/maintained with a smart charger to prolong battery life. I don't think the 1985 Onan generator 3amp trickle charge is right for AGMs.

My on board 35amp charger was not connected to the generator battery by Trojan when the boat was designed/built. Whenever my generator is running my battery charger is charging if the engine/house batteries need charging. I would like to connect the generator battery to the unused third bank of the battery charger so that I have smart charging for all the AGM batteries. I am trying to find out if anyone knows for sure if this can be done without damage to the generator?

Thanks

[Big D]

A little long winded but here’s my take:

OEMs typically don't hook up chargers to the generator batteries because it shouldn't be necessary. The caveat here is that you do what you're supposed to do which is run your generator often. In doing so, it's quite capable of maintaining the charge of its own battery. Not running them on a regular basis will just kill them faster anyway but that’s another thread. You can build in some redundancy by charging from an external source but you shouldn't need to if you have a healthy battery. You can also build in an emergency start feature to parallel with another bank if you wanted peace of mind.

In this particular case the generator's charging circuit isn't working so the need for an external charging source is a consideration. I don't see the charger's output affecting the generator's hardware though. The hardware mentioned as a concern operates under the same voltages in other applications all the time. I think the concern was perhaps the amount of current the charger would supply, but in simple terms, it’s not the charger’s output current that matters, it’s the output voltage. The current going through the hardware (load) is dependent on the hardware and the supplied voltage which affects the amount of current the hardware will take to run it (load). Current doesn’t get pushed through it, it’s a function of how much current the hardware uses to operate. What does get pushed is voltage and the amount we’re talking about here is the same whether it’s in a generator, boat, automobile, lawn mower, etc. that would see the same voltage output (and current in some cases) as that from alternators.

If your generator charging system works and you want to run the generator while on the hook and power up the charger so you can charge all the batteries, it’s doable, it just won’t charge at the same rate and it usually causes an oscillating output of both the on-board charger and the generator’s charger. You may not notice it but chances are it’s happening. Charging systems rely on reference voltages to adjust output, that’s how they can tell when the battery is charged. When voltages from two separate charging sources are present, each charger sees a false voltage and adjusts its output accordingly; increasing when the reference voltage drops and decreasing when the reference voltage raises. The result can be compared to the cycling of a starter solenoid when you’re trying to start an engine with a dead battery. The clicking is a result of the solenoid turning on and off as it reacts to the presence or lack of voltage. When the solenoid fires, it clicks but causes a voltage drop as it uses what little power the battery has left, then disengages, when it disengages, the voltage recovers, when it recovers there is enough voltage to fire the solenoid again and so on. This cycling is similar to what can happen in multiple source charging systems as voltages rise and fall due to the two chargers reacting to each other’s output. The other thing that needs to be considered is that some smart chargers will completely shut down all outputs/banks if they see a conflicting charge voltage on any bank, it drives the computers crazy depending on the unit. In those cases, people are having to install selector switches on the output that is hooked up to the generator battery so that it can be switched off if the charger is running under generator power.

Has anything else on the generator been checked? Don’t know the model but I suspect there’s likely a charge relay and there may also be a separate winding in the generator portion itself.

[WayWeGo]

I never fired up my Kohler Generator (my 6.5 single cylinder gasoline engine generator) while the boat was connected to shore power. What part of that statement is confusing to you two guys??

Why would anyone try to charge their generator battery while the generator was running??

Rick, perhaps your charger is hooked up differently from mine?

My charger is hard wired to one of the breakers on my AC panel. If the generator is running and powering the panel, the charger is running unless I turn off its breaker. The charger has three banks wired to it: the two main batteries and the generator battery. If I wanted to isolate the generator battery from the charger, I can turn off the breaker for the charger (which would not charge the main batteries either) or I could disconnect the wire from the charger to the generator battery.

[rickalan35]

Where We Go,

I have to assume that I know much less about this topic than I thought I did. So I'm feeling pretty humble.

Big D knows what he's talking about and after reading his post I do have a couple of additional questions that I may ask him.

In every generator equipped boat I've ever owned, past and present - the shore power and the generator were/are both connected directly to my main panel.

There has always been a rotary switch on the panel with three possible positions.... SHORE - OFF - GENERATOR

When out on anchor and in need of AC power, I turn the switch to GENERATOR. When returning to the dock, I usually connect the shore power chord and turn the switch to SHORE.

So I assumed by moving the switch to SHORE I was also shutting down the Generator side and vice versa. I assumed that each "side" powered the Main Panel independently of the other.

Maybe I should just leave quietly......

Rick