amps, watts, and volts...oh my

[Hart_family]

Thanks Thom. I read the whole thing. Much didn't apply to my situation (travel trailer vs. motorhome), but I did learn a few things. Thanks again!

[Hart_family]

Originally Posted by 1l243

I am thinking the Dealer is closer to right than wrong. Your converter has three modes that it charges at. It probably starts out at around 14.4 vdc and around 5 amps then as the battery charges drops eventually to a trickle charge of around 1amp. It could take your converter a full day (24 hrs) to get to 90% then another day on float to get to 100%. If your only charging 2 or 3 hours a day on your generator you can see how long that might take.
Honda does make a battery charging cable that connects directly to the generator and batteries for higher amp output than your are getting from your converter. But even this I don't think will work long term. You just can't seriously run your generator long enough.

Not all trailer connections are wired to charge the batteries from the tow vehicle as your driving, mine isn't. Mine is wired for backup lights.

I have four 12v deep cycle batteries. When dry camping I am not shy about using power for TV and lights(led) but I try to avoid running the furnace. I run my Honda 2000 generator about 4 hrs a day and I can watch my battery volt meter drop a little each day. After 7 to 10 days I have to find a place where I can plug in for a few days to fully charge my batteries.

Also after you have charged your batteries for several hours and you think they are fully charged because they say 12.7v+. Let the batteries rest for an hour and test it again. I think you will find that they did not fully charge with a standard converter in that amount of time.

My plan is to get a minimum 200 watt portable solar panel with controller so when your gone during the day you will be charging those batteries.

Thanks 1l243.

I did mention in a previous post that there is a direct 12 V DC cable connection from the generator directly to the batteries, but it is an unregulated (not smart) charge of 8 amps that cannot be left on indefinitely (unlike a smart charger which can stay on). 8 amps seems like more than the 1 or 2 amp charge the dealer said I would get through my converter, so I bought the cable.

UPDATE: I called the manufacturer of my converter/charger today (WFCO). When connected to an AC power source (30 amp at RV park, or 15 amp at home or via generator), my particular model puts out 65 watts of output. If nothing else or very little is being used in the trailer, Larry at WFCO said that the converter will send as much wattage (up to 65 watts) as the battery "will accept". The converter is a 3-stage one, so it can charge a more depleted battery in a "bulk" mode, which will take FAR MORE than 1 or 2 amps like the dealer said. All other things equal, Larry said that running a generator for 2-4 hours a day on two 81 Ah batteries, at 50% depletion, should be fine for a 3-5 day camping trip. I will not use the 12 V DC cable from the generator. Rather, I will just plug my darn generator into the regular power port on my trailer and get the batteries as charged as they can be each day.

So although there are many opinions out here, I will just go with that WFCO says (since they MAKE the charger) and test this out for myself. I just wanted to research it first as to not get caught too much unawares.

[Hart_family]

Originally Posted by wahoonc

You need to find another dealer...

I am going to hazard a guess that you probably have a WFCO WF-8955 converter. It should charge the batteries to 80%+ in 2-3 hours from 50% (which you do not want to drop below). The last 20% will take another 4 hours or so. Which may be what the dealer is getting at. You will get better charging from using your on board converter/charger than using the 12v leads on the generator. The only way around the slower charging would be to upgrade to LiFePO4 batteries and the proper charger for them. Quite expensive.

I have seen a charging curve chart using the WFCO, have to see if I can dig it up. I believe that the WFCO can charge at up to 30 amps in bulk mode, but doesn't like to stay in bulk mode long enough for a proper charge.

FLA (Flooded Lead Acid) batteries can only be charged so fast for so long, then they slow down and take a while for the top off charge. Solar works well for this if you are in an area with enough sunlight.

You should figure on running the generator 5-6 hours a day after a night of heavy draw down. You can use 2 batteries to help with capacity. You also should really consider putting in a proper meter to actually keep track of your usage. My personal preference is the Victron BMV-512, others like the Trimetric. Both are quality meters and will let you keep track of what is going on.


As far as charging while towing... It will depend on the vehicle, the size of the wire, etc. Typically you won't get more than 5-7 amps from the tow vehicle.
Aaron

Thanks wahoonc. I have two 12 volt deep cycle batteries rated at 81 amp-hours each. I agree and have heard many times to try to not run them below 50% too often as this will extend the life (number of cycles) the battery can perform.

Now that I have actually called WFCO myself, I agree with nearly everything you said. Spot on. My best bet is to just use the converter in my trailer (WF-9865 which has a 65 watt output). But yes, the batteries will slow down their charging as they get close to "full". Not a problem. I will just plan on running a generator for 2-6 hours a day for various reasons, one of which is to recharge my batteries.

[Hart_family]

Originally Posted by ewarnerusa

Wahoo has given great info.
The dealer is mostly wrong, but there's some truth to the claim.
According to your OP, your converter has a 65 amp rating. This means it can deliver up to 65 amps DC if conditions call for it. Such conditions would be a depleted large battery bank. When your converter has 120V AC power (plugged into shore power or generator), it will by default start in bulk charge mode. It will start to deliver amps to the DC charging lines and monitor the voltage that it sees. If your batteries are depleted, let's say they are at around 12.2V. They will happily accept the charging amps and as they do, their voltage will begin to rise. If you have a large battery bank that is at 12.2V, they can accept quite a bit of amps and your converter may indeed crank out full 65 amps. But a smaller battery bank, like your 2 batteries, will see their voltage rising quickly and reaching the setpoint of 14.4V. Once they reach that voltage, your converter will begin to taper the amps down so that the voltage remains constant at that setpoint. It will continue to do this for likely several hours, during which time the amount of amps required to hold that setpoint decreases as well. After a certain amount of time or a certain duty cycle (on/off percentage), depends on the programming of the converter, the converter will drop down to float mode where it holds the voltage constant at like 13.4V. Same concept, it will provide just enough amps to hold that voltage constant.

Another caveat, and maybe what the dealer is thinking of, is that the WFCO brand converters are notorious for not actually achieving the bulk/absorption stage modes. This means it will skip the bulk/absorption charging at 14.4V and go right to float at 13.4V. This means that it will indeed take many many hours to reach full charge. But you will still get meaningful charge initially on a depleted battery bank.

Wow. Thanks ewarnerusa. You seem to know your stuff. I posted a few updates here, and I think we are in agreement and saying the same thing (I called WFCO and I believe they said what you just said), but read my update posts to make sure.

THAT SAID, I am a little discouraged about your comment about the WFCO converters skipping a bulk charge mode. I would hope if my batteries were depleted enough, that it would do what it is designed to do and charge it as fast as it can, including going through bulk and float, etc. We will try this out this spring/summer!

[Hart_family]

Originally Posted by 1l243

Well, regardless of what your converter is charging at it's not working for you. So, your going to have to come up with plan B. Running the generator for many more hours, by-passing the converter and charging directly to the batteries with the generator, solar or adding more batteries......

1l243....thanks again. I DO appreciate it. To be clear, I have not even OPENED or used my generator yet. Will be trying everything out for the first time this spring/summer, but I was trying to not have a huge fail and get out there armed with information. Again, this is just what the dealer told me. According to WFCO, connecting 12 V DC cables directly to the batteries at 8 amps IS INDEED an option I can use, but I think I will use the built-in converted in the mean time as it SHOULD send more than 8 amps to the batteries, at least for a while. I understand that solar is an option to (which is why I think the dealer was giving me a hard time about my converter).

[Hart_family]

Originally Posted by videoarizona

Agree with above...the 30 Amp AC plugged into the generator(with adapter) will work just fine for most situations. The issue your dealer may be thinking of is the 12 volts coming off the the TV while running down the road is a trickle charge. That's what's it's designed to be. But yes, the converter in your RV will charge your battery in a reasonable amount of time.

I would run the 12 volt DC direct to the battery from your genny. But understand that the DC circuit is not regulated ...IE...it will over charge quickly as it's a constant 12volt 8amp output. At least that's the warning I get on my brand new Honda 2200i.
So, yea....run the genny for an hour, charging at it's rated DC output, then switch over to the RV 30Amp AC plug and let your on board converter continue to safely charge the battery the rest of the way.

Make sense?

THANK YOU videoarizona. I agree with you. However, I think I will try letting my converter start the charging, but I always have my 12 V DC cable at 8 amps (unregulated like you said) as another option either before or after using the converter. But I would need to watch it carefully. I think I WILL invest in some sort of voltmeter (correct term?) so I can be more informed on the battery charge (as opposed to just the little battery display I have on my control panel in the trailer).

[Hart_family]

Originally Posted by Wanderer

Remember that any battery charger slows down as you near a complete charge. Charging daily will only give at best 4 amps per hour with any charger. Running a generator for only 4 amps is not very fuel efficient. It's best to run down the battery to 70% and then charge using a smart charger either on a generator or plugged into shore power. This way it'll initially charge at 8-12 amps per hour making generator charging much more efficient both in amps charged and fuel burned.

I would only use the generator battery charger in an emergency and never for routine charging.

Thanks Wanderer. Yep - agreed that battery charging will slow as the batteries become more "full". I made several update posts to MANY great suggestions by you and others. I THINK I have this figured out.

I agree that I will probably use the 12 V DC cable directly from the generator to the battery as backup or at least very carefully.

I didn't quite understand your amps per hour unit. I have not heard that one before. I think amps (current) are sent continuously at whatever level they are sent. Amps over hours is usually referred to as amp-hours (multiplied).

I DO have a smart charger (NOCO Genius 3500), but it is only 3.5 amps maximum, I think. That doesn't seem very fast or much, which works just fine for the winter when my batteries are in the garage, but may not work so well when I am trying to recharge my batteries daily while dry camping. I WILL take my NOCO with me as an option, I suppose.

All that said, my WFCO converter is suppose to put out a LOT more DC amps to the batteries than 4 (WFCO is saying up near 60 amps that a depleted battery would accept, after any loads in the trailer are satisfied first). So, I will use my generator hooked up to my regular trailer port to charge my batteries as a first step. I have other options from there, it sounds like.

[Beachbourbon]

I think my post was misunderstood. My point was that you can plug a portable battery charger into your generator and then attach it to your batteries to charge them in minutes instead of running your generator plugged into your RV for hours to get the same results.

[Hart_family]

Originally Posted by Beachbourbon

I think my post was misunderstood. My point was that you can plug a portable battery charger into your generator and then attach it to your batteries to charge them in minutes instead of running your generator plugged into your RV for hours to get the same results.

Thanks! Not sure what you mean by portable battery charger. I have a battery "maintainer" (NOCO Genius 3500 smart charger) which charges the battery at 3.5 amps maximum, which would take a LONG time to charge from depletion.

Another option is to plug my Honda 2200i generator directly to the batteries with the 12 V DC cable I have, but that is only at 8 amps and not regulated.

I have concluded from talking to WFCO that my trailer's converter/charger will do the best job of charging my batteries in most situations, and should be by FAR faster than the other options I have available to me.

[wahoonc]

Here is a chart that will give you an idea of how discharged your battery bank is. For this to be accurate you need to let the batteries rest for about 4 hours with no charging or discharging (disconnected). Battery voltages will vary with temperature as well as activity. That being said... I have used a cheap plug in meter to give me a general idea of what is going on with the batteries, it is more accurate than waiting for the low battery alarm on the CO/LP detector to go off.

The WFCO converters are notorious for NOT wanting to stay in bulk mode or go to float mode. People have changed up wiring, moved batteries and such to try and make them work properly. In my case the WFCO crapped out so it was promptly replaced with a similarly sized Progressive Dynamics unit which has a more robust build and charges better.

I think you will be okay, for the most part using your generator and the WFCO converter to keep the batteries charged up. Make sure you keep the water topped up in them using distilled water. Because you are going to be going through multiple charge/discharge cycles this will be critical for battery life.

Aaron

[Red Badger]

for about $130 I got a set of the harbor freight 45 watt solar panels - they keep my batteries charged up and are quiet - I know you said you didn't want to go solar yet... but this is a good way to test if you do want to go that route

[ewarnerusa]

Good work reaching out to WFCO and I'm glad I gave consistent info! Your onboard converter should suit your needs just fine if you have a generator available. They are notorious for not being as "smart" as advertised and will likely only ever charge at 13.4V instead of bulk first @14.4V and then dropping to 13.4V. So it will take a day or so plugged in to shore power to get your batteries to 100%. But a couple hours on the generator will definitely get you some meaningful charging while you're camping, you don't need it at 100% every day to be usable.
bestconverter.com sells direct replacement converters for WFCO models, but I've never purchased from them. I think the Progressive Dynamics converters are well liked among boondockers. The remote pendant means you can manually trigger the bulk charge. I have heard that they are very helpful at bestconverter if you give them a call and explain your situation and what you looking to replace/improve.

I have never bothered to upgrade the WFCO in our camper, our solar takes care of us. :-)

[wahoonc]

I will vouch for Best Converters. I have bought several converters and some other items from them over the years. Randy the owner is a veteran, and is very knowledgeable and quick to respond to emails asking questions. Great company to deal with.

Aaron

[persistent]

Ok, I read about half of this thread. Some posters have already said the following and are correct.
1) The 12 volt output of the Honda ...I series is limited. It is not a 12 volt battery fast charger. It can deliver probably 8 amps but again it is not a battery fast charger and will probably not deliver 8 amps into the battery.
2) The converter/charger the OP cited probably delivers far more than 8 amps when plugged into the Honda generator or shore power. But, it may or may not be a battery fast charger.
3) Using a standalone battery fast charger may charge faster than either the Honda 12 volt output or the converter/charger cited. This is true if the converter charger is not a fast charger and the standalone fast charger has enough capacity. It all depends on initial capacity and the maximum charging voltage the charger allows. I have an expensive 20 amp marine fast charger that senses voltage at the battery terminals that cannot beat the 30 or 40 amp fast charge converter/charger in my TT.

It is obviously an issue people care about a lot. It may not be simple and people use all kinds of rules of thumb to make it understandable. It is still a science and if you understand it you can test each of the theories users present. I will not address all the different theories posted in this thread, only the basic facts summarized.

There are as many different TT charging systems as there are TT manufactures, models, and years of production. I do not recognize the converter/charger the OP referenced. If it cannot supply more than 1 or 2 amps then it is not worth keeping. I suspect it supplies much more.

First, even a Honda 1000i 1000 watt generator can provide all the 115 volt power a good fast charger needs to charge 200 amp/hours worth of battery as fast as the batteries allow. So using the 115 volt output is the first leg of the best method.

Second, even an inexpensive modern converter/charger will probably beat inexpensive other charging devices. Older converter/chargers may or may not.

Older versions probably take 18 hours to bring battery from 10% to 100% and can take multiple days to top the battery off. These devices may provide 30 amps or more to start the charging process. Of course a 50 amp would provide more faster.
As the battery charge level increases, the current continues only until the voltage at the charger output reaches 13.6 volts. At that point the current starts to drop. By the time the charge level is above 70% the current may indeed be only a few amps. It continues to taper off for days.
However, it is the last 10% that takes all the time It will get to 70 or 80% fast (when the output voltage reaches 13.6 volts) then taper off and progress slowly.

A modern converter/charger is likely to be a "fast" charger or a microprocessor controlled charger. Using the same scenario, the charge profile is the same up until the voltage reaches 13.6. The fast charger does not stop there. The fast charger will continue to deliver the full capacity of the charger (maybe 30 amps) until the voltage at the charger output reaches 14.6 volts (a little more or less). At 14.6 volts the voltage stabilizes and the current starts tapering off. Because the voltage is higher than 13.6 volts, charging has continued at a higher rate and thus takes less time. Eventually the microprocessor will lower the output voltage to 13.6 and maybe to 13.2 volts. This is programed to happen before the batteries are overcharged. My inexpensive converter/charger will switch to 13.6 after a few hours and 13.2 volts after 4 days. It has reached more the 90% in less than 5 hours.

I have not measured the 12 volt output of my Honda generator. It may be above 13.6 volts. It may be as much as 15 volts. Even so, it is going to loose the race because the converter charger is far a head by the time the 12 volt generator starts catching up. Hopefully the generator will run out of fuel before the batteries are overcharged at 15 volts (less then 90% of battery charge).

The best combination for recharging TT deep draw batteries:
1) Use generator 115 volt output. Even a very small generator will work fine.
2) Use the TT converter/charger as the battery charger.
3) Get a microprocessor fast charger TT converter/charger if your existing one is not a fast charger. For one 60 amp/hour deep draw battery, a 30 amp converter/charger is enough. For bigger battery banks and more house usage, the bigger the charger capacity, the better. Mount the charger as close to the batteries as possible. Use short heavy cables with as few as possible connectors and switches.

[Hart_family]

Thanks persistent. That was a lot of information. I know this isn't a "simple" straightforward thing. I think the consensus is that my Honda 2200 plugged into my trailer should be just fine to get my batteries from common depleted states (say around 50%) to near 90%. It seems that getting the batteries to a true 100% is what takes more time. I don't pretend to understand the electronics of why....but that is what everyone says.

That said, I looked up the "amp draw" of my heater, which would be running off my 12 volt batteries during a cold night. The draw is 3.0 amps. I presume this means that if my heater ran ALL night (8 hours), then it would take 3.0 amps x 8 hours = 24 amp-hours from my battery. My two batteries are rated at 162 Ah (81 Ah each), so this seems like not a big deal. Part of the reason I asked this question to begin with was due to another thread which indicated that running a heater for ONE night would nearly drain my batteries. Just not seeing it yet, but again....haven't even tried it in the real world.

[ewarnerusa]

I think a furnace fan draw is closer to 10 amps. I don't recall what outdoor temperatures you're talking about camping in, but unless it is frigid winter camping I doubt it would run continuously all night. I think the rule of thumb is that a single 12V battery is good for about one night of furnace use, so something like 10A x 4 hours = 40Ah which is about 50% of an 80Ah battery. In your case, you get 2 nights of furnace use by rule of thumb.

[persistent]

Originally Posted by Hart_family

… from common depleted states (say around 50%) to near 90%. … "amp draw" of my heater, which would be running off my 12 volt batteries during a cold night. The draw is 3.0 amps. I presume this means that if my heater ran ALL night (8 hours), then it would take 3.0 amps x 8 hours = 24 amp-hours from my battery. My two batteries are rated at 162 Ah (81 Ah each), so this seems like not a big deal. Part of the reason I asked this question to begin with was due to another thread which indicated that running a heater for ONE night would nearly drain my batteries. Just not seeing it yet, but again....haven't even tried it in the real world.

Most TT heaters do not use nearly that much power.

50% to 90% = 40%
162 * (40%/100%) = 65 Ah available
65 / 24 = 2 nights with 17 Ah left for other purposes and with another 40% in reserve (10% to 50% reserve).

A digital multimeter from your local hardware store may cost $10. An excellent investment to begin understanding voltage during charging and discharging batteries.
13 volts with no load and not charging is fully charged.
More than 14 volts is fast charging
13.6 while charging is late stage for fast charger and mid stage for older constant voltage charger.
13.2 while charging is long term maintence charge.

Good to go!

[persistent]

Originally Posted by ewarnerusa

I think a furnace fan draw is closer to 10 amps. I don't recall what outdoor temperatures you're talking about camping in, but unless it is frigid winter camping I doubt it would run continuously all night. I think the rule of thumb is that a single 12V battery is good for about one night of furnace use, so something like 10A x 4 hours = 40Ah which is about 50% of an 80Ah battery. In your case, you get 2 nights of furnace use by rule of thumb.

The furnace in my Kodiak Cub draws slightly less than 2.5 amps. Slightly more while the igniter is on. It runs less than 40% of the time when the temperature is below 0 degrees (less during higher temp day times, more during low temp night times.

Of course furnaces come in all sizes and efficiencies. A good cheap power monitor like mine does wonders for clearing up doubts.

[Hart_family]

My TT heater draws 2.7 amps, not 10 (see image). And yes - I know it would not run 8 hours a night. I was just being conservative for the math. Again - I had several TT owners tell me that my 162 Ah battery bank would only run my heater for ONE night only. I think that is way overly conservative. At 2.7 amps running 4 hours per night, I could theoretically go for 8 to 16 nights (50% to 100% depletion) with no other use. I am not worried anymore. Either way, this is moot since I would be charging the batteries to 80% or more each day using a generator (or solar perhaps in the future).

[Beachbourbon]

Originally Posted by Hart_family

Thanks! Not sure what you mean by portable battery charger. I have a battery "maintainer" (NOCO Genius 3500 smart charger) which charges the battery at 3.5 amps maximum, which would take a LONG time to charge from depletion.

Another option is to plug my Honda 2200i generator directly to the batteries with the 12 V DC cable I have, but that is only at 8 amps and not regulated.

I have concluded from talking to WFCO that my trailer's converter/charger will do the best job of charging my batteries in most situations, and should be by FAR faster than the other options I have available to me.

This will recharge your battery In minutes...just plug into your generator, charge up, them maintain as usual with you WFCO. Just one of many options

https://www.harborfreight.com/10250-...art-60653.html