We mostly dry camp. For years I have been keeping the batteries charged by plugging in the trailer power cord to a small Honda or my new Yamaha 2000 watt generator. Trailer has a 7355 Parallax converter. Never really had many problems but I've been reading on this forum about this not being the best way to maintain your batteries. I started looking more closely at the Parallax 7355 and I see that it has a max output of 55 amps but a typical battery charge rate of only .5 amps. WOW-that's nothing.Here is my question. The Yamaha genny has a 12 volt outlet that puts out 8 amps. Would this be a better way to charge my batteries directly from the generator? The short 12V power cord that came with the generator has a very light duty looking cord. Wire is only 18awg (pretty thin).I would much appreciate any comments. DALE

You can get more amps from the 7355 than from the gen's DC charger, which does about 8 amps. Ignore that 0.5 amp thing which they explain is phoney. The limitation of the 7355 is its voltage of 13.8 when you want 14.8 or at least 14.4. You should be getting anywhere from 35 to 25 amps at first from the 7355 depending on how far it is from the battery bank and the wire gauge they used.The 7355 will do 55 amps when used as a power supply with good wiring for the amps. EG, run something from the inverter that draws 100 amps and turn on the 7355, and amps drawn will show as 45, indicating the converter is supplying the other 55.But on a battery it can't do that because the battery voltage when being charged gets up close to the 7355's 13.8 so not enough voltage diff to make for high current. You need a charger that will run in the mid- 14s to make a wider spread between the two voltages and get the high current.There are several choices for which converter or charger that would be. Each brand has its own fan club :)

The way to go if your converter is a single stage charger is to upgrade to a multi-stage as that will serve you much better than the DC charger contained on many generators. BestConverter.com is a good place to get info, Randy can walk you through the process.

Dalo wrote:The Yamaha genny has a 12 volt outlet that puts out 8 amps. Would this be a better way to charge my batteries directly from the generator?No. That genset 12 vdc charging output is unregulated and can easily result in overcharging your batteries. Instead invest in a good stand alone charger, plug it into the genset, and charge with it. In my case, I simply turned off my crappy WFCO 8955 converter and instead use a CTEK Multi US 7002 to charge the trailer battery. In your case, because you're using a genset as your charging source, you'd be better off with a CTEK Multi US 25000 for much shorter genset runtime. NOCO also offers similar products.

Dalo wrote: I started looking more closely at the Parallax 7355 and I see that it has a max output of 55 amps but a typical battery charge rate of only .5 amps. Looks like somebody got the decimal point in the wrong place. That would be a charge rate for Float.

7355 will charge at 55 amps. Voltage is just 13.6 so amps will taper off very quickly and take 24 to 48+ hours to get a full charge on a low battery. Yes the 12v connection will help a bit as it will provide 8 amps at 14+ volts. Eco mode must be off to get 8 amps so that wastes gas and is annoying.Real solution is to replace the 7355 with a multistage converter or a portable that will provide about 15 amps minimum per battery. Progressive Dynamics or IOTA are the only converters I recommend for charging with a generator.

Yamaha ef2000 charging the batteries | Good Sam Community

Dalo
Explorer
Nov 04, 2016
Hi, My previous post about a 40 yr old Montgomery Wards portable charger (10amps @ 12.6volts) would seem to be too low of a voltage to do much good. I gather from reading the above comments I really need at least 14.1 volts minimum. Do I?
Been looking at the Progressive Dynamics and IOTA 60 Amp converter chargers and found them on Amazon for around $190. They sound like they would solve most of my problems. Some of the reviews for those were critical of poor quality and needing early replacement.
time2roll
Nomad
Nov 03, 2016
Yes you can walk away for six hours.
2oldman
Explorer II
Nov 03, 2016
I have no idea
red31
Explorer
Nov 03, 2016
2oldman wrote:
red31 wrote:
so how long does it take a 8A 'unregulated' charger to raise a 100 ah 50% dod batt's voltage to 15v?
50ah/8a

and would require no baby sitting for over 6 hrs?
2oldman
Explorer II
Nov 03, 2016
red31 wrote:
so how long does it take a 8A 'unregulated' charger to raise a 100 ah 50% dod batt's voltage to 15v?
50ah/8a
red31
Explorer
Nov 03, 2016
so how long does it take a 8A 'unregulated' charger to raise a 100 ah 50% dod batt's voltage to 15v?
road-runner
Explorer III
Nov 02, 2016
MEXICOWANDERER wrote:
That 8 amp charging port ROBS field excitation electricity from the generator rotor.....Robbing the field for battery charging can rob the generator A.C. output potential from say 3,000 watts to 800 watts. This is a fact of life with any home generator with a field voltage tap.
Does this really apply with a permanent magnet rotor? The manual cautions that the power from the DC and AC outputs, when used simultaneously, cannot exceed the rated genset power. The DC output has its own dedicated stator winding.
MEXICOWANDERER
Explorer
Nov 02, 2016
When the onboard charger slumps to 10 amperes, connect the manual charger and watch the amperage jump up. Where does some of this information come from? Jeez! That 8 amp charging port ROBS field excitation electricity from the generator rotor. Measure it open circuit. It will read something near EIGHTEEN VOLTS. My 5500 diesel Yamaha had a belt driven alternator I measured at at 21 amperes max at 14.1 volts regulated.

Robbing the field for battery charging can rob the generator A.C. output potential from say 3,000 watts to 800 watts. This is a fact of life with any home generator with a field voltage tap.
SoundGuy
Explorer
Nov 02, 2016
Peg Leg wrote:
My Yamaha 3000 the 12v output is regulated to 12v.

Sorry to disappoint but that 12 vdc charging port on your Yamaha genset is unregulated, meaning it can easily overcharge your batteries and cause them to boil if you don't monitor the charging process carefully. No different than the 12 vdc charging port on many of these inverter style gensets, regardless of brand.
scrubjaysnest
Explorer
Nov 02, 2016
Oasisbob wrote:
My Honda EU 1000 also has 8 amp charging. I find it much faster to bring along a plug in battery charger and charge at 15 or 25 amps. Takes 2 - 4 hours depending on how low the batteries went. I usually do this every three days or so. Better to charge briefly once a day rather than lettin them get too low. Hope my option works for you. It's cheaper than a new converter

We use a portable smart charger if there are three or four cloudy days.
15 amp is ok for a pair of 95 to 105 Ah 12 volt batteries but if you have GC-2's then a 25 amp is best.