Power Question

[dryflie]

I have just learned that my campground will stop running it's generator this year. The entire place was rewired about 5 years ago and now they are putting the plug. As it was we only had power about 7 hours each day but it was enough to get stuff done in the morning and evening and also to get batteries charged, we survived.

My Solaris T2670 (1996) came with an Onan 4000W Genset, currently disconnected as we do not dry camp, but we will be considering getting it rewired. My question relates to battery charging using this Genset. With the standard converter in this trailer what can I expect the generator running time needs to be each day to recharge a single deep cell battery?

If the run time is excessive what are practical options for upgrading the converter?

Thanks for any advice you can offer about personal power.

Al

[frank]

Originally Posted by dryflie

I have just learned that my campground will stop running it's generator this year. The entire place was rewired about 5 years ago and now they are putting the plug. As it was we only had power about 7 hours each day but it was enough to get stuff done in the morning and evening and also to get batteries charged, we survived.

My Solaris T2670 (1996) came with an Onan 4000W Genset, currently disconnected as we do not dry camp, but we will be considering getting it rewired. My question relates to battery charging using this Genset. With the standard converter in this trailer what can I expect the generator running time needs to be each day to recharge a single deep cell battery?

If the run time is excessive what are practical options for upgrading the converter?

Thanks for any advice you can offer about personal power.

Al

Al,

The answer will be "it depends." The battery and the converter you have will be part of it, and your usage will also be the major driving factor.

You will want to get together the capacity of your battery, and which converter you have. You will also want to take few minutes to put some figures against your usage - for example, "we run two lights 6 hours/day," "four people shower so the water pump runs for 15 minutes a day" and things like that.

When you have an idea of your usage, that can be converted into Amp-hours (Ah) of usage. You can then make an estimate of how long it will take the converter to bring the battery back up to a reasonable level.

Finally, is your trailer at this campground full time or do you tow it to/from home where it's on shore power at home? The reason I ask is that battery charging is a little tricky. It's fairly easy to bring a battery back to the 85% or so level. Getting from 85-95% is a bit more difficult, and that last 5% or so is the most difficult. For example, a battery at 60% may take 2 hours to get to ~85%, then 6 hours to get to ~95% and then 4 days to get to 100%. These are just rough numbers to illustrate the point, so don't take them as gospel..

Report back and we'll see what we can do to help you out. I also have done some measuring of power usage and I can get that posted as well. One other thing you should do is google "12 volt side of life" and read the two-part article. It's a pretty good one that will help you out a bit here.

- Frank

[dryflie]

Frank, thanks very much for the help. Here's the deal....my trailer goes on site in early May and stays there until late Sept so it's not able to hook up to shore power at all now (with the Campground generator gone). With a bit of luck I'll find a good RV mechanic/electrician to hook up the Onan genset I have currently. We'll be able to run that generator for probably 6-8 hours per day (if needed ) but honestly I would rather not run it any more than necessary. We mostly need to make a pot of coffee in the morning, run the water but that's it, after 8-9 AM we outside. We'll run the Fridge on Gas so don't really need power for that either. Mostly my concern is getting the Battery charge each day so we have lights at night and the heater fan runs when needed.

The deep discharge battery I've used over the years has worked great, we get DC lights when needed, heat runs at night when needed and the AC provided the charge and also power to make coffee.

Bear in mind this is primarily a fishing camp setup, we're outdoors most all of the day so power is only an issue when we want to run water, make a pot of coffee. The DC power from the one battery has always served us well for evening lights.

Without the big generator I do see an issue with battery charging however. Since I'm in the camp for periods of time and then away for long periods I'm concerned about the Battery staying full during periods when there is no power. We've always had the 6-7 hours each day of shore power in the past so even when away the converter kept the battery up to a serviceable level. With no shore power I wonder now what I'll find each time I return and try to start the Genset.

I'm considering a second traveling battery, one that goes home with me and then gets plugged in each time I hit camp, the other then goes home and we do a swap each time we visit. Do you think that's a sensible idea or do you feel the battery in place will hold a charge over time?

I do have a Magnetek 6336 converter, for what it's worth. I'd prefer not to have to deal with the expense of an inverter what with all that is happening at this time. I guess I really need to try to understand just what the required generator run time will be just to keep that battery charged.

Sorry for the long ramble but this is a differnt sort of situation than most I suppose.

Al

[JohnB]

Hi Al

Yes you do have a unique situation. The furnace is one of the highest users of DC. But the battery can handle it if it is up to snuff.

To help fill in more of the equation, tell us this:

1.How man days (nights) are you at the camp using the battery?

2.How many days are there between camping trips? Extended away time.

It may be that if the extended away times are long enough, take the battery home with you, charge it up and put a Battery Minder Plus on it. It will then be at 100% and desulfated. Then if wanted get a 2nd battery as a back up. When at camp, run on the 1st battery, monitor state of charge, then when down to 50%, change to the back up. Take both home and top off and maintain.

Use the genny as needed to give what it can in 4 to 5 hours as needed, if needed. Pending use, and length of time it may not be needed.

What group battery do you have, 24, 27 or 29? If you are just doing weekend fishing camp trips, with the power you stated, having 2 fresh topped off batteries can do you the entire weekend and maybe even 4 days plus a little and never fire up the genny. Group 27’s or better Group 29’s have a lot more capacity if your going 12 volt batteries. The only down side is hauling them. However never returning a battery back to full charge and letting it sit a month or more and then trying to get high use from it will catch up to you eventually.

Hope this helps

John

[264SRinPA]

Hi Al

You might want to look into one of these. Use your Onan and the onboard charger for when you need a quick charge, and the solar for longer deep charge.

[Honda03842]

When camping in our Bounder without an AC hookup we've found that running our generator for an hour in the morning and in the evening is adequate to maintain batttery charge and provide us with adequate electricity.

We usually turn on the generator in the morning to make coffee and catch the news and in the evening during supper.

The killer is the heating system, it can really suck the battery down. We would typically run the heat during the evening hour when the generator was on and possibly turn on the electic blanket to take the chill off the bed.

In our Sunline, we have replaced the primary light bulbs with LEDs. Lights can be a major draw; I think 2 amps a bulb. When dry camping we do not hesitate to run our LCD TV usually off a small 75 watt inverter. Our small LCD seems to draw about 15 watts.

Making coffee is not an issue, we use an inverter, because coffee doesn't take long to make. One alternative is to consider a catalytic gas heater that does not have the power blower, using it only when awake. We have found that once under the covers, we never need supplemental heat.

In both our rigs we have an Inverter with a desulfation mode which really does seem to prolong battery life. One advantage of a solar cell, is that it keeps the battery(s) charged while you're away, particularly if it's big enough to overcome the small drains of the trailer's systems.

Hope this helps,

[frank]

Al,

Here's some figures to help you gauge your usage. These are actual measured current draws on my '02 2363.

Standby Current (LP Detector & Radio Memory) - 0.32 A
Single Incandescent Bulb in overhead fixture - 1.45 A
Fantastic Fan Create-A-Breeze Model on LOW - 1.07 A
Fantastic Fan Create-A-Breeze Model on MED - 1.45 A
Fantastic Fan Create-A-Breeze Model on HIGH - 1.84 A
Radio ON - 0.43 A
19" LCD TV (running on an inverter) + Antenna Amp - 4.26 A
Range Fan - 2.24 A
Furnace Running - 4.68 A

Unfortunately, I don't have the figures for the refrigerator, water heater and the water pump handy. Those are written on a pad in the trailer, which is currently buried in 3' of snow. As I recall, the water pump averages about 4 A when running.

I'm not sure which fridge & water heater you have in your coach. The newer style, electronically controlled with electronic ignition models need power to operate. The older style with the pilot light does not. You will need to factor that into your usage as well.

Now, what to do with these figures. You want to estimate your usage of each item on battery power, and multiply the draw in amps (from above) times the amount of time it runs (in hours). This gives you your draw in "amp-hours".

For example, the standby current from the LP detector and the radio memory is 0.32 amps, and it runs 24 hours a day. That's a total of 7.68 Amp-Hours of battery usage per day. If you also ran a single light bulb for 3 hours a day @ a 1.45 Amp draw, that's another 4.35 Amp-hours.

If those were your only loads, you would be using a total of 12.03 Amp-hours per day.

Also, as John mentioned, your need to determine your battery type, and it's capacity. Lets say you have a group 27 with a capacity of approximately 90 Amp-hours (Ah). If that was the case, and you were using a total of 12.03 Ah per day, then you would know you are using approximately 13.4% of your battery capacity daily.

It is generally considered acceptable to use 50% of the storage capacity in a battery without doing damage. This does assume that you will be charging the battery ASAP and not letting it sit. A partially discharged battery left to sit is very bad for it's lifespan.

Many folks who run off battery tend to run 60-80% cycles. This means that they will let the battery get down to approximately 60% SOC (State of Charge, the percentage of capacity left in the battery) and then run the genny to bring it up to approx. 80%. This is done because it becomes more 'difficult' (takes more time) to charge the battery the closer you get to 100% SOC. When they return to shore power, they can then allow the battery to charge back up to 100%. Charging to around 80% gives them a good bang for their generator fuel buck.

As far as charging.. your magnetek seems to be a 36A converter. The actual charge current it can deliver will vary depending on a number of factors, and it will taper down as the battery charges. For sake of argument, its probably safe to assume you can get an average of 8A. With our example figures, this boils down to the following:

If you were using ~13.4% of your capacity each day, you could run 3 days before hitting ~60% SOC.

Assuming a charge current of about 8 Amps and a battery capacity of about 90 Amp-hours, it would take almost 2.5 hours of generator run time to get you back up to 80%.

Hopefully that all makes sense. I'm not always the best at explaining these things.

All that said, if you don't need to run the fridge when you are away for the week (or if yours doesnt need 12V to run) then doing a battery swap each week sounds like a real good solution. As John mentioned, a decent charger at home will get you back to 100% SOC during the week. If you don't need to power anything in the coach when you are not there, then either take the battery home with you for a good charge, or at least install a disconnect switch (or disconnect a terminal) when you are not there.

If you do need the fridge running, then a single battery is probably not going to be enough to make it through the ~5 days or so that you will be away from the coach. You'd be looking at either swapping a pair of batteries, or you would probably have to take a good look at a solar solution.

Hopefully this helps some and we can continue to discuss some options. Please don't hesitate to ask if something doesn't make sense, or if you have more questions. Several of us on here really enjoy these tech type discussions.

- Frank

[JohnB]

Originally Posted by frank

Several of us on here really enjoy these tech type discussions.

- Frank

H'mm wonder who they "might" be....

Great post Frank . I'll be really looking foward to your other amp readings off that fancy meter you have. Also when you hooked up to mine at the ADK M & G, the radio was unplugged and the fridge on LP. So LP and propane detector was in my 0.32 ish amp overhead. That and what ever my battery volt meter display uses.

John

[dryflie]

Thanks to all for the great notes and suggestions. Some have asked about the frequency and lengths of visits. These vary from long weekends to a week or even 10 days and the intervals between visits could be a week or a month or even 6 weeks. I still work (just one more year) so I can't spend as much time in camp as I'd like.

Given the length of some intervals it's likely I'll shut everything down, clean out the Fridge etc and go dark if it's going to be more than a week.

My fellow campers and I have discussed the various battery options, many are looking at those large banks of boat batteries with solar backup and a small generator for the few times we need AC. I'll get my generator hooked up and go with a couple of Batteries this year and see how that works. Perhaps try some solar next year if the other guys like how that does.

Thanks again for the help you are all a great resource.