questions about battery charging/draining

jrt13 · 11-10-2019, 01:29 PM

Hi guys,

my house batteries die after a while, I leave it for a few days with nothing but the refrigerator (running on gas) I know that it still uses electricity, but I do have a solar panel that is always showing that its charging during the day, if it is charging why would my batteries die from running practically nothing ( I know its still running the co2 alarms and stuff like that) I also read that making sure the inverter is off would help (I don't know if it was off or on when this happened). when I run my generator it shows just one load, will one load actually kill a battery even if it has the (seems to be useless) solar panel?

Will my generator charge the house battery? I have come to the conclusion to not run my fridge and just disconnect everything.

2010 Winnebago Adventurer 35P
Onan 5500 generator.

Thanks

Jeff

Winterbagoal · 11-10-2019, 04:26 PM

Dead batteries are an issue we all face sooner or later. The causes and solutions are far too many to list here. Anything is possible in the land of RV AC and DC power systems.

Yes, generators usually charge house batteries, if no one has tampered with the wiring set up from the factory. So does shore power, and the engine alternator, and solar, if it's also wired correctly.

jrt13 · 11-10-2019, 05:06 PM

I do have a solar panel but im sure its very small, and probably not enough to charge much, will it charge if I have the battery disconnect turn off? I don't think it does but figured I would ask. I have a 10w solar panel, I am sure its to weak do do much. Also how about 6v batteries, would they fair better for me?

Thanks

Winterbagoal · 11-10-2019, 05:13 PM

The simple answer is "it depends" on how the solar and charge controller is wired, if it's factory installed, or after market DIYed? You could ask Winnebago support if it looks factory installed to be sure. Send a note to
[email protected]
It's their technical support email address - include your VIN and/or your WGO serial number if you know it. They keep pretty extensive records on everything they make.

Possibly on 6V batteries. Many people swear by them. They're heavy, so I chose another option. I just installed 200AH of lithium iron phosphate in my Navion, but have yet to really test them. So far they seem to charge well and there's very little charge leakage while idle, as far as I can tell, once they're full.

Magnum108 · 11-17-2019, 06:37 PM

First. How old are your batteries? What type are they, lead acid? AGM? Do you have an inverter? How many batteries and what size? If your batteries are more that 4 years old they could be going bad. If lead acid, they might need serviced. If an inverter, might have something trying to draw 120v. If not enough amp hours they might just be a normal drain.

jrt13 · 11-17-2019, 06:54 PM

the batteries are about 2 years old I would say, and I am not having a problem with them yet, I am just being cautious. I have a 10v solar panel on the roof (came factory) but its not enough to cover the refrigerator (on gas) and the alarms that draw power. I have found the generator to charge the batteries, Im just afraid to leave the fridge on for 2 days that I am not there and come back to dead batteries. I am going to try it on Tuesday, let them run all day and check Wednesday morning and see how much down it is, if its not down I will see what it looks like Thursday morning

jabass · 11-17-2019, 07:15 PM

After you charge up your batteries on Tuesday, wait about 1/2 hour then use a multimeter across the batteries to see what the voltage is. then Wed morning repeat the check with the multimeter across the batteries. If you have less than 11 volts you most likely have a bad cell in one of the batteries.

On Tuesday after batteries are charged, You can also check the amount of current being drawn from the batteries by disconnecting your cable going from your battery and use the multimeter (use 10 amps circuit) , by connecting one probe to the battery and other end to the disconnected cable. with the furnace fan not running and no lights on, you should be using less than 1 amp.....

jrt13 · 11-17-2019, 07:24 PM

I have over 11, the onan genset energy command 30 keeps me updated on the voltage, its shows over 13 when charging and 12.6 while full. is one amp enough to run the alarms and fridge?

**creativepart** · 11-17-2019, 11:14 PM

I’m not positive but I believe you have only the tiny 10-watt solar panel connected directly to your chassis battery. That system, besides being pretty useless at charging your chassis battery does nothing to charge your house batteries.

I guess WBGO thought it would sound cool to say there was a solar panel. But it’s really not helping anything in any meaningful way. Tiny panel incapable of much output, wired directly to your coach’s starting battery without even a basic charge controller. It doesn’t need one because it’s not putting out enough power that it would ever need controlling.

It’s not unusual for your RVs parasitic loads on their own to drain your house batteries in short order. That’s why they advise you to disconnect your house batteries when the RV is not in use. Running the fridge, even on propane only hastens the drain on your batteries.

**creativepart** · 11-17-2019, 11:27 PM

Quote:

Originally Posted by jrt13

I have over 11, the onan genset energy command 30 keeps me updated on the voltage, its shows over 13 when charging and 12.6 while full. is one amp enough to run the alarms and fridge?

The EC30 shows you voltage, but it’s misleading and not an accurate gauge of battery state of charge.

Check your battery bank’s voltage 20 to 30 minutes after you stop charging. So 30-minutes after unplugging from shore power or stopping your generator.

Voltage of the bank is difficult to use as a gauge because it’s not that fine a measure. 12.7v is fully charged. 12.2 is 60% discharged and 11.9 is so low you are damaging the battery.

To accurately gauge your battery bank’s state of charge you would need to install a shunt-based Battery Monitor Kit. A BMK will measure all power in and out of your batteries and give you a SOC - State of Charge in percentages.

jabass · 11-18-2019, 09:24 AM

If you are running your absorption refigerator it will take 4 to 5 amps to run it on electric, but using gas you will only use power for the fan(s) and this should be less than 1/2 amp. Why not measure the current with your multimeter in series with the disconnected cable.

thataway4 · 11-18-2019, 12:15 PM

I believe an absorption refrigerator running the heater on 12 volts will use a lot more than 4 to 5 amps--think in the 20 to 30 amp range. My Via, tends to run on 12 volts when going down the road, and that is our experience, for a fairly small ref/freezer. A Danfoss Compressor type will be in the 3 to 5 amp range. (I run two of these on my boat for both a freezer and refrigerator).

The solar panel is not doing much. You really should have at least 100 watts to be effective (which will have to include a controller).

I like to monitor the battery use--Victron or Balmar (with shunt) are my preferred systems--these measure voltage of 2 battery banks, amps in, amps out, cumulative amps used, and state of charge. Cost is in the low $200 range. I changed out the two group 24 batteries to two 200 amp hours golf carts for my VIA. Almost doubles the capacity.

I realize that some of the sites give a voltage of 12.2 volts as 60% charged (40% discharged). Many others consider 12.2 volts 50% charged, and that is the limit of discharge for best battery life. Problem is that these "charts" are based on steady state battery voltage. That is no charge or discharge for at least 4 hours--and best if none for 24 hours. That is why a monitor is so important.

The charging of the house battery by the converter. Unfortunately the converters which most of our RV's have are made to supply 13.6+/- volts to the house when you are plugged into power. They are not really good battery chargers, and certainly not a "smart charger". I prefer to have a separate charger, which will charge the battery thru Bulk Absorption and float charges--some are even better, and they monitor the battery voltage, only applying a small charge when needed, perhaps 2 to 3 times a day.

If you have a Magnum, Xantrex or other good inverter/charger, then that resolves the battery charging issue--however very few of the smaller and non diesel pushers have these good chargers.

**creativepart** · 11-18-2019, 12:44 PM

Bob is spot on with his info. I agree that 12.2v/12.1v or so is the bottom of the safe usage range for most batteries.

Batteries are like everything else - subject to interpretation. A stated norm is often debated. Many (most?) say you can safely use and recharge for many hundreds of cycles if you don't go below 50% SOC. Others say don't go below 60% SOC and still others say dropping to 40% SOC is not so bad.

If you take care of your batteries they will take care of you.

Once when I first put my RV in storage for 4-weeks I forgot to turn off the battery disconnect. Luckily, my RV came with one 100W solar panel and a charge controller. So, while the batteries dropped WAY lower than I would ever want them to go (11.9v) they weren't totally dead. YIKES.

Now, I have 300w of solar and I make sure not to forget to turn off the disconnect and my batteries are virtually always at 100% SOC when I pick up my RV from storage even after 3-months.

My 400ah of true deep cycle 12v AGMs are 2 1/2 years old and seem to hold charge well. When they stop doing that even if it's just one battery I plan to replace them with LiPo batteries.

thataway4 · 11-18-2019, 01:07 PM

A quick thought about LiFePO4 batteries, since they have been mentioned several times in this thread. I have 200 amp hour usable. as a second system in my boat running the freezer/refrigerators and Inverter systems. If the technology had been available, when I bought this RV, I probably would have gone with LiFePO4 there also.

The Li battery is about $950 per 100 amp hour battery--which has usable 80 to 90 amp hours. The battery charger from the land side, be have to be changed out--and I would change or modify the converter (110V Ac to 13.6 V DC). These that are already installed would not play well with the Li batteries.

There will have to be a different arrangement for the charging off the engine alternator. There are two ways to go there: One is a battery to battery charger from the chassis or engine start battery--either 30 ro 60 amps by Sterling. The other is a Precision Circuits LiFePO4 Battery Isolation Manager– Precision Circuits Battery Guard. There are Battery information managers, and isolators. (Similar to a voltage sensitive relay). There is heavy cabling, a fuse (200 to 500 amps), a battery monitoring device (I use Victron 702, but Balmar now has the G200 which is also good. I choose a Victron Multiplus inverter charger (2000 watts inverter/80 amp charger, programed for the 200 amp hour batteries. All up this system is going to be around $4000. If you have significant solar panels, the controller may also need to be changed. I suggest that you stick with one brand if possible.

I consider it worth while, only if you use the vehicle off grid a lot, and will keep it for many years. It is more complicated (and potentially dangerous) technology, and not for the neophyte RVer.