Onan Gen batteries register LOW(11.63)

[OpiesMom]

2010AllegroOpenRoadRED34FT

We keep it plugged in here at home in the side yard. I run the gen at least once a month for an hour. The number does go up when we are driving but comes back down when we get home and plug in. Everything works fine. We take a weekend club trip monthly and drive it then for an hour or so.

The screen saying low is new. This bothers me. I turn off the 12 volt power while it is plugged in thinking that is what ran it down. We were gone for a month like always this summer living in the motorhome and that 12 volt was turned on the whole time. Yes, we add water to the batteries. The level is good.

It registers 11.55 now after running the gen for an hour.

The only thing I can think of is to unplug the motorhome here at home for a few days and see what it reads after that.

[luvlabs]

Normal voltage on a fully charged pair of batteries is 12.6V. Your batteries are well below the recommend recharge point of 12.2V. When being charged by the engine, the battery voltage should be around 14V, when being charged by the generator or shore power, the voltage should be reading around 13.3V.

Your batteries are probably pretty well toast if the voltage reading is correct and will need to be replaced. However, it sounds like the charging system needs to looked at as well. Also, you should check all of the connections - at the batteries, at the fuse, at the ground connections and make sure they are tight.

Are you using just the volt meter on the system panel (tanks, LP Gas, Bat) or are you using something else? Do you have a multimeter? I would use a multimeter to check the voltage at the batteries before I went too much further trying to figure out what is going on. If that voltage is OK, then the meter you are looking at is problem.

[camaraderie]

The batteries are dead and have been killed.
You CANNOT charge batteries in an hour. Regardless of the size of the charger...you can only put in around 15%-20% of the rated amp hours in an hour in a wet cell battery. If you DON'T charge the other 80%...then you get sulfation which kills the batteries.
Suggest putting a trickle charger on the batteries to maintain charge while plugged in at home if you don't already have that...once you replace your batteries.

[62Morgan]

Rule no. 1 with all rechargeable batteries: never store them at less than "fully-charged". Not 85%, not 70%, etc. Check with a multi-meter after each trip.* The engine alternator output should bulk-charge; but 1 hr. running time might not be sufficient to get back to 100% CHARGE.

* It also bears mentioning that you cannot get an accurate battery state-of-charge immediately after you've just charged it. Charging has heated-up the batteries & ruined any reliable reading. You have to wait 1.5 to 2 hrs. after charging to get a good voltage reading.

Check for any parasite loads when 12 volt switch is OFF. some Co2, smoke detectors are hard-wired, fridge or entertainment muffin fans, etc... Make sure OFF is really OFF, or add a shut-off between negative wire and the first battery.

BTW; when you run the generator for an hour monthly, do you warm it up for several minutes and then apply a load? [ at least to 1/2 it's rated capacity] by running the air-conditioner or another power-drawing appliances? No electrical load on the running genset is doing grave harm.


If you travel on a monthly basis, why not use that trip to exercise the genset? On either the going or return trip run the genny under at least 1/2 electrical rated load. FWIW: Download a chart showing the power draw for your various appliances so that you can add up the numbers for a better idea of how much each draws. [also comes in handy when boondocking or limited to 30 amp pedestal power.

[targaboat]

It we read your question carefully and not jump to conclusion, you comment that you turn off the DC. That implies you have the master switch off will charging. It will never charge with that off.

Get a multimeter, learn how to use it, and make sure you understand how everything works in your coach.

[dirko]

Hi Ho: I'm confused. What are the Gen batteries? Are those the coach batteries or the chassis batteries? I'm assuming they are the chassis batteries or the ones that start the engine as most RV's use them to start the generator. If so, you need to provide some method of charging them when plugged in. The alternator in the coach will charge them when the engine is running, but the generator may have no way to charge the chassis batteries at all. We use a Trik-L-Start to assomplish this.

We can't tell the condition of these batteries from the info you supply. You need to fully charge them and then check them with some kind of load test.

[Shadowcatche]

11.55 V immediately after charging (and not accurate as you need to wait a couple of hours) is less than 20% SOC. I would replace and use a Battery Minder or its ilk.