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ronahue View Drop Down
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Direct Link To This Post Topic: Battery Charging
    Posted: 01 Jan 2018 at 1:58pm

Assuming 2 Trojan T105 6 volt batteries and a Honda EU2000i generator (or shore power as they should be about the same) charging through the standard R-Pod converter approximately how long would it take to recover the batteries to 90% charge from a 50% charge. I'm not looking for an exact number just an estimate, 2, 4, 6, hours. A little background on the question I currently have two type 24 12 volt batteries and I am considering replacing them with the T105's. The 12 volt batteries will recover from 50% to about 90% in about 2 hours I am aware that the 6 volt take longer to recover. I am also aware of the many advantages of the 6 volt set up, however one video I watched indicated the recovery time on the 6 volt may be double that of the 12 volt batteries. 
Before you ask why not solar? That is another option I am looking at but for now I need to stay with the batteries and a generator.
Thanks in advance,

Ron  
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GlueGuy View Drop Down
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Direct Link To This Post Posted: 01 Jan 2018 at 3:04pm
It's not really the capacity of the generator in this case, it's actually the capability of the WFCO 55-amp converter.

That converter will output ~~ 660 watts maximum, which is well inside the capabilities of the generator.

At 50% discharge you will have to put in ~~ 1350 watt-hours of energy.  That assumes no conversion losses or other inefficiencies. So I would expect that the batteries could be brought up to full within 3 hours. That's largely a SWAG (Scientific Wild A** Guess), but should be in the ballpark.

If you are using any 12 volt anything in the trailer during this period, it will take longer because it would take power away from the recharge function.
bp
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StephenH View Drop Down
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Direct Link To This Post Posted: 01 Jan 2018 at 3:31pm
The time depends on state of charge. From the WFCO manual:

Converter Operation Modes

All WFCO power converters are automatic three-stage switching power supplies. The converter senses which mode it needs to be in by checking the RV system voltage.

The three modes/stages of operation include:
Absorption mode/Normal operation
Nominal battery charge and supplies power to appliances
Bulk mode/Charge mode
Fast battery charge and supplies power to appliances
Float mode/Trickle charge
Trickle battery charge during storage

Absorption Mode: During this mode, the converter output is in the 13.6 Vdc range. This is the normal operation mode. This mode provides the 12 Vdc and current required by the 12 Vdc RV appliances, as well as slow charging the battery.

Bulk Mode: In this mode, the output voltage of the converter will witch [SIC] to 14.4 Vdc range for a maximum of four hours. If the converter cycles between "Absorption and Bulk Mode", there could be a shorted battery cell or other issues.

Float Mode: In this mode, the converter is charging the battery with a trickle voltage of 13.2 Vdc. When the converter senses a demand (by turning on lights), the converter automatically returns to the "Absorption mode".

What is not addressed in the manual is the amperage that it being output to the battery during these charge modes. The converter is rated at 55 amperes, but just what amperage is being output at any given time is not addressed. The two T105 6V batteries are rated at 225 Amp-hours at the 20 hour rate. If they are discharged to 50%, then half of that amount will be needed to fully charge them (112.5 Ah). The rub is that while this is going on, power is likely being used for other purposes so that will extend the charging time some as well. If you have access to a clamp-on DC amp meter, you could check to see. I don't have one.

The other point is that I was reading on another forum that the WFCO converter will not go into bulk mode unless the voltage reading is less than 13.2V. There is no way to override this to force it into bulk mode for faster charging.

I have two Duracell GC2 215 Ah batteries. I should get a clamp-on amp meter myself so I can check on this.
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Direct Link To This Post Posted: 01 Jan 2018 at 4:13pm
Just an observation. +1 to SH description from manual. I have noticed when in the float mode, if my voltage gauge drops below 13.2 and remains there, the cells are low on water. Not significant but 13.1 or 13, I add water to cells. Takes little time and back at 13.2. I have never seen it in Bulk Mode.
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Direct Link To This Post Posted: 01 Jan 2018 at 5:07pm
Also.. when you compare your battery size.. it's just like a gas tank.. The GC2's hold more amps, so that, by default, adds a measurable amount of time to the charge cycle. Just as filling a 12 gallon gas tank takes half as long as a 20 gallon.. and 20% of the time (and $$$$$) of a 48 gallon. LOL
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Direct Link To This Post Posted: 01 Jan 2018 at 6:46pm
The only time I saw it in bulk mode is when my previous converter failed. When I replaced it, the converter went to bulk mode until the batteries were brought up sufficiently. Once that happened, it went to absorption mode and I have not seen it in bulk mode since.

I had been using a 15A portable charger/maintainer while we were traveling until we could get the replacement converter. I had to purchase that one. Once we got home, the defective converter was replaced under warranty. That one is sitting in the box as a spare in case I have another failure.
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Direct Link To This Post Posted: 02 Jan 2018 at 9:21am
Originally posted by StephenH

The only time I saw it in bulk mode is when my previous converter failed. When I replaced it, the converter went to bulk mode until the batteries were brought up sufficiently. Once that happened, it went to absorption mode and I have not seen it in bulk mode since.
The converter is still doing bulk mode, but you might not see it if you're only monitoring voltage. When the charger is in bulk mode, it is (mostly) current-limited, as the batteries will absorb so much power that the voltage will still be below the bulk mode "voltage limit". Depending on how quickly the batteries come up to nominal voltage, and also depending on the charge profile programmed into the charger, you may never "see" the bulk mode voltage on a meter. Many smart chargers will appear to go directly (or almost directly) to absorb mode. However, the zone/time just prior to absorb mode is still bulk mode.
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Direct Link To This Post Posted: 02 Jan 2018 at 4:51pm
My guess would be about four hours.

Keep in mind that when using multi-stage charging of lead acid batteries, the charging 'curve' is not linear.  It takes almost as long to charge a lead acid battery from 80% to 100% as it does to get it from 0% to 80% when using a multi-stage charger.  This process can be sped up, but this will shorten the lifespan of the battery.
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Direct Link To This Post Posted: 04 Jan 2018 at 11:10am
I have a Honda EU2000I generator and it has a 12V DC battery charge plug in built in. You can get the cable to hook direct to the battery. I would guess that would be quicker? 
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Direct Link To This Post Posted: 04 Jan 2018 at 11:21am
Originally posted by mjlrpod

I have a Honda EU2000I generator and it has a 12V DC battery charge plug in built in. You can get the cable to hook direct to the battery. I would guess that would be quicker? 


Nope. If you look at that it says it's 8 or 10A max (can't remember just which) that means it can only charge at that rate.. Your built in charger will charge at 55A max.. way faster. The best answer is to just plug the pod into the generator, and use it as "shore power".
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