Battery vs genny questions

[johnm1]

Hey all you electrically smarter than me people ... I need some battery help please.

9 days of dry camping. I'm bringing my genny but we're in a State Park, in the middle of 10 families with tents, so I want to run it as little as possible (within reason). Since I don't dry camp all that often I don't want to buy a 2nd battery if I don't need to.

We have a brand new 2015 Laredo 291TG with ...
- WFCO 9875 converter that puts out 14.4 Vdc in bulk mode, 13.6 Vdc in absorption mode and 13.2Vdc in float mode. I talked to WFCO and they couldn't/wouldn't tell me the charging amps (apparently there are too many variables).
- Interstate dual purpose battery (HD24-DP), Group 24 size, 405 CCA, 505 MCA & 100 RC. Not enough space to go to a group 27 without cutting the current welded on brackets.
- 2000 Watt Inverter Generator (Champion). When running, it'll be plugged into the RV shore power cord powering the whole RV.

My battery draw (in amps - checked with DVM in series, not clamp on) is ...
- Only propane detector = 0.18A
- Only fridge (on gas) & detector = 0.60A
- Only main LED cabin lighting & detector = 1.15A
- Only water pump & detector = 8.50A
- Only water heater (while heating) & detector = 0.85A

Best guess useage (for 9 days):
- Fridge and propane detector = 216 hrs.
- Main lighting = 2.3 hrs.
- Water pump = 2.3 hrs.
- Water heater = 4.5 hrs.

If I did the math right, that's about 155 amps.

1 - Can I make it for 9 days with the battery (listed above) and running the genny every once in a while?
2 - How long do I need to run the genny to get a good charge on the battery?
3 - How often do I need to run the genny to keep a good charge?

All in all, I'd rather spend a few extra $$ in gas for the genny than $100 +/- for a 2nd battery that I'll only use for one camping trip per year.

Thanks for your help,
John

[beemerphile1]

Some of the drycamping battery charging people on here are very intense. They will have you spending $5,000 by the time they are done.

Your converter is fine. Four gauge or bigger wiring is a very good thing.

A second battery in parallel would be a very good idea but not mandatory.

Your Champion is fine.

I imagine a lot of those tent campers will be happy with you running the generator if you will let them charge their phones.

Here is what we have been doing;
We have a pair of 12v gel deep cycle batteries.
We have LED lights and are somewhat conservative with power use.
We charge with a WFCO 8725P. That's right, 25 amp output.
We run the generator twice per day. Once in the morning to make coffee. Once in late afternoon to make coffee again. I know, there are other ways to make coffee!
About every second or third day we will allow the generator to run for an extra 30 minutes after coffee is done.
We can camp with this method virtually continuously.

You may need a little more generator time based on your power use but not all day. Get a volt meter and check the battery voltage every morning with no load and before running the generator. Do not run the battery below 50%.

[MNtundraRet]

duplicate post

[MNtundraRet]

Just do the 24 to 48-hour test that I suggested, and BFL also asked for, before you change anything. If you have a clamp-on meter for reading 12v, dc, amps and a meter to read dc volts, you can take readings every 2 to 4 hours to see how discharge is going on the battery

Also; once you start the generator you can watch to see if the voltage reading, taken at the battery-terminals will rise from initial voltage to 14.4 volts with-in about 10 minutes, or never rise above 13.7 volts.

You can check the amps with your clamp-ammeter (off either + or - cable) a minute or two after starting the generator. Depending on which cable you clamp over the reading could be + or - but it doesn't matter since you know you are charging.

Early on the reading might get into "bulk" mode with 20 or more amps before the voltage reads 14.4 volts. A weak battery bank will accept higher current initially with the need of 14.4 volts to force-feed the battery(s).

Whatever the amp reading is early on will drop with each succeeding hour of charging. The reading taken by a clamp-on meter at any given time represents how many amps would go to the battery if that rate existed over a full hour.

For example: reading at start of 20 amps, reading at end hour 1 of 10 amps. The average of the two readings would be 15 amps (15+10/2). The 15 amps (for first hour) would end up being lower due to battery charging not being 100% efficient.

As you can see unless you can get a higher amp reading thing are going to take time. Acid-lead batteries only accept around 20% of AH capacity on average (20 amps per hour for a 100 AH battery)to get to around 90% of full charge.

[johnm1]

Ok, my head is starting to spin now! Looks like I need to ...

- Look at wiring size from converter to battery - up size if needed.
- Run the battery down to 12.0, run genny or plug into house. If voltage rises to 14.4 ... good to go with current converter.
- If not, then add, or swap out, WFCO converter and put it closer to the battery.
- If I "need" to change out the converter, a 35-60 amp is adequate.
- Swap all lights to LED. This is already being done.
- Purchase a 2nd battery (deep cycle - not dual purpose).
- Bring my portable car battery charger ... after I verify that it'll charge the way I need it to.

- Bring lot's of ice and beverages and have fun!

I know run length makes a difference but what gauge wire should be used between the battery and converter? If I had to guess, the run is ~20-25 ft by the time you add in going under the floor, up to a battery disconnect and back down to the battery, etc.

Everyone's helping me A WHOLE LOT on this ... Thank you!!!

[NinerBikes]

johnm1 wrote:
Oh ... I'm sure there's fun to be had by all ... as long as the beer is cold and we don't run out!

Back to the converter question please ...

Do I "need" a 75A converter even if I end up adding a 2nd battery or is a smaller (lower) power one OK?

45 amps, in your case, with one battery, or two, is plenty. I can get by with a 30 amp unit, if it stays in bulk mode, 14.4V, no problem. As a matter of fact the slightly smaller pd 9245 45amp unit, with a short run of fat wire to the battery or batteries, will get you to a higher state of recharge before it kicks out of bulk mode and drops the charge voltage to put it in absorption mode, than the more powerful PD 9280, which really needs a much larger battery bank with more amp hours, to work well, around 300- 400 Ah of battery pack.

[westend]

If I didn't want to do any upgrades or changing but wanted to get underway for camping for a two week trip, I'd get a second battery and hook it up to the RV battery with jumper cables.
A guy might be a little forward-looking and get a bigger battery for the future or the same size if the existing battery is new and of good quality. The latter choice would allow the use of two similar batteries paralleled for permanent connection.
BTW, get a hand-held multimeter. $10 will save a $75 battery and eliminate any guessing as to the condition of the battery.

[time2roll]

You only need 20 amps per battery for fast charging.
With 2 batteries 35a to 60a is plenty.

Give that WFCO a test before you rip it out. Run the batteries down slow with one light to 12.0-12.2 volts and fire up the generator. If voltage at the fuse panel steadily rises to 14.4 volts you are good to go. If it pops up to 13.6 volts and holds for an hour.... you may as well put it on ebay.

If your portable charger is 25+ amps it should get you through the trip OK running the generator 2 or 4 hours per day.

If you will be parked in the sun... consider 200 watts to 300 watts of solar. Portable is fine for now.

[mbopp]

I feel you pain about NYS parks, shade, and solar. That's why I don't have any solar panels.

Our old HTT had a single-stage converter that I supplemented with a deck-mounted 55A IOTA. The IOTA now resides in the pass-through on the new TT and has a 3' wire run to the dual G27 batteries and is on a switched outlet. The WFCO converter in the TT is now on it's own circuit breaker so I can run either converter depending on the situation. The TT also got LED lighting before it left on the first outing.

Look at your battery charger carefully. My 2-10-30A Schumacher charger only went to 30A for 30 seconds "on" and 60 seconds "off." No such problem with the new converter.

[BFL13]

johnm1 wrote:
Oh ... I'm sure there's fun to be had by all ... as long as the beer is cold and we don't run out!

Back to the converter question please ...

Do I "need" a 75A converter even if I end up adding a 2nd battery or is a smaller (lower) power one OK?

75a charging is a good rate for a 220AH bank, such as with a pair of 6s or two 27s. On one battery it won't be harmful; the battery will only take what it needs from that.

You don't know if the WFCO will do its rated 14.4v when charging. If it will you don't need to change it out. If it won't, it may just be due to the wiring from it to the battery being too long/thin. Once that is fixed, the WFCO might then work right.

If the wiring is too long thin for the WFCO, it won't be any better for a different brand of converter.

You can leave that WFCO where it is and get a "deck mount" second converter placed closer to the batteries so you don't have to rewire the WFCO to battery path.

You can get another two or three portable chargers and use them all at once to get the amps for a faster charge to reduce gen time.

Yes, do the backyard camping test and find out what you really can do first.

BTW, you can take extra batteries along (in the truck or inside the trailer) without installing them. I have done this and it works just fine. Set them on the ground by your installed battery and link them all up with jumper cables. Now you have a big battery bank.

You can keep them all charged as though installed, or you can take some away from the campground outside gen hours and use the gen and a battery charger all in the back of the truck while driving around sight-seeing. Lots of ways to do it, but first you need more batteries.

[SteveAE]

John,

I would be concerned if you only replaced the converter that the wire diameter (likely too small) between the new converter and battery would still limit the charging.

Could you bring along a second fully charged battery and just swap when the first one gets low? Then, when the second battery gets low, put the batteries in parallel and charge both at the same time with your stand alone battery charger and generator. The charging wouldn't be perfect, but it would minimize generator run time and your outlay would just be the cost of a second battery, enough jumper cable to complete the parallel connections, and some time to fuss with it.

Oh yea. If your existing battery is older and/or hasn't been maintained as well as you maybe intended, it probably would be a good idea to replace it as well.

Hope you have a campout,
Steve

[MNtundraRet]

johnm1 wrote:
Oh ... I'm sure there's fun to be had by all ... as long as the beer is cold and we don't run out!

Back to the converter question please ...

Do I "need" a 75A converter even if I end up adding a 2nd battery or is a smaller (lower) power one OK?

Two group 24 deep-cycle batteries (not yours) would be best mated with a 30 to 45 amp 3-stage charger. Otherwise; the charger will sense a smaller battery and never go into "bulk charging" mode.

The idiot hired by your manufacturer knew little about charging systems. I suspect the cabling used is nowhere near a heavy enough gauge for proper operation. In this case "bigger is NOT better" when taking into account; charger capability, battery-bank size, and required cable gauge size for proper operation.

[johnm1]

Oh ... I'm sure there's fun to be had by all ... as long as the beer is cold and we don't run out!

Back to the converter question please ...

Do I "need" a 75A converter even if I end up adding a 2nd battery or is a smaller (lower) power one OK?

[Sandia_Man]

Without investing some $$$ into this venture I'm afraid your genny will have to run many hours daily increasing in runtime as the days go by. A second battery ($90), upgrading WFCO converter ($200), converting to LED lighting ($50-150), and/or purchasing a portable 40 amp smart charger ($125) can all play a part in effectively reducing generator runtime.

Camping off the grid for extended periods shouldn't be taken lightly as it could significantly diminish the quality of the camping experience. Additionally you may find that you enjoy this type of camping (you already have a genny) and further investment will yield improved results when doing so. We prefer this style of camping and our first step was to add a second battery (there's always room somewhere for it) which gave us more time between charging cycles via genny. Sounds like a great trip ahead, here's hoping it all works out and everyone has a wonderful time.

[MNtundraRet]

With only a dual purpose group 24 battery, you will find that you will need a lot more generator time than you think you will need. The manufacturer should have installed a true deep-cycle battery in Group 27 (unless not possible).

Sorry to downplay chance of success, but that battery cannot survive without plenty of generator time. The WFCO 9875 would, in theory, supply up to 75 amps but not possible with one crappy small dual-purpose battery. The converter/charger will most likely not come close to too full capacity. That size charger should be mated with more than two batteries.

Amp outlook may only be about 15 amps per hour of generator time.

The best way to find out who is giving you an honest answer here is to do a 24-hour test at home, or a weekend at a campground where you can plug into shore-power when things go south on testing.