Charger not charging batteries when on Generator

[denders]

This is a head scratcher for me, 1985 3607 aft cabin , with a 30 amp Newmar charger. When connected to shore power the charger functions nornally putting out roughly 10 amps DC into the batteries. Gradually reducing to zero as the bank charge goes up over 13 volts. When I disconnect from shore power and start the generator - There is 12 volts at the charger output ( measured with multimeter ) but zero amps going into the batteries. Stop generator and plug back into shore power - charging starts again. I ran the generator for 45 minutes and actually saw the availble volts go down from 12.2 to 12.1 in that timeframe. My first response is to replace the charger with something from this century but I would really like to understand the behaviour. Any thoughts from the forum ?????

Thanks in advance

[g36]

The genset charges its own battery, are the others connected to it through a charge relay , selector switch etc?

[denders]

There is the Mid 80's carver selector switch - 1 , all , 2 and off . The generator is putting out the voltage it is supposed to , all outlets and a/c work. The charger is a 3 bank charger , there are 4 batteries - I have not been able to determine how they are setup. One has 1,000 CCA - I will assume that is a starter battery ( on our 82 carver that would have been bank 1 ) and the other 3 would be the house bank ( bank 2 in our previous boat ). All batteries are charged when we are on shore power , and none are charged on the generator.

[Midnightsun]

Have you actually measured that there is sufficient voltage to the charger when the generator is running? If so then the only thing I can think of is the power from the generator is dirty and your charger does not like it. Had this happen with an older Generac whole house generator at home where some electronics would simply not function. What puzzles me is it worked before. Maybe the generator output is just getting old and not producing sufficient clean power to fire up the charger? Could also be the charger is getting old and finicky wanting cleaner power.

Normally you will have a battery/engine, a house battery and a generator battery so 4 in total. Problem is someone may have reconfigured as many do to have a larger house bank. Gonna need to get in there with a volt meter and study the wiring to figure yours out.

[bud37]

Your voltage as measured is very low, actually a fully charged battery right off the charger should read around 12.9 vdc.......your 12.1 is a depleted battery. While the charger is operating initially you should see well over 14 vdc. I agree it makes no sense for the charger to only operate when on shore power, but could be a power issue , to have the charger wiring miss the 120 vac from the genny would be quite odd.

It may be time like you say to move on from that charger. Also a quick check of the generator output may not be a bad idea here......you want to see around 59 to 61 Hertz at around 120 volts.

[denders]

Thanks for the responses , I will check the generator output next time we are at the boat. I didn't think that would be an issue since everything else including the A/C is working fine on generator power. I will verify and do more digging on the wiring. I will also pull out the battery tester and check each battery indivdually, might be time to just bite the bullet and move to AGM batteries for a house bank and a new charger.

[bud37]

Source of the post I didn't think that would be an issue since everything else including the A/C is working fine on generator power.

Actually, all the other equipment will probably operate if the cycles are off, but whether they work up to par is another matter.....old style chargers not so much.....worth a check to put that to bed......good luck an your hunt..

[km1125]

What is the model of the charger??

I would think with a NEWER charger that the voltage and frequency of the source (generator) would be more of an issue. The older ferro-resonant chargers would take just about anything and still run fine.

What kind of transfer switch do you have to switch over from shore to genset power for the 120VAC? Some of the older ones had a manual switch but some had an auto switch. Could be that the charger breaker (is it on a dedicated breaker??) is wired into the transfer switch so that it won't run unless you're on shore power. Take a pic of your VAC power panels and post them... I wonder if they're stock. You'd have to open up the rear compartment to check the wiring for changes from stock though.

[denders]

Km1125 - It is one of the older Ferro-resonant chargers. The charger is putting out 12 volts regardless of power source but close to zero amps on the genny. The transfer to shore from Genset is supposedly automatic , there is another issue where when we plug into shore power both 110 AC main breakers trip. I am not sure how that would be related - if the transfer switch didn't switch over the generator would not be putting out 12 volts on genny. I know the breaker for the charger is not stock ( so someone did something somewhere sometime ..... I call this a POS ..... Previous owner syndrome .

[tomschauer]

Just a check, if you are testing the output of the charger, with the batteries connected to the charger and the charger has no input power ( therefore no output power) you are simply reading the voltage of the batteries, not the charger.
You want to disconnect the charge leads to the batteries and see what you have.