Community Forums

JerryKelly · 10-01-2007, 01:43 AM

While on battery power yesterday, I noticed that the charge dropped to 12.1 volts within 30 minutes, just with using the interior lights. The inverter seems to be charging correctly and the batteries have been maintained. I have 4 6 volt Interstate brand batteries, installed in December of 05, purchased the MH in February 06. It is always plugged in with the inverter / charger maintaining the charge. Is it time for new batteries?

JerryKelly · 10-01-2007, 01:43 AM

While on battery power yesterday, I noticed that the charge dropped to 12.1 volts within 30 minutes, just with using the interior lights. The inverter seems to be charging correctly and the batteries have been maintained. I have 4 6 volt Interstate brand batteries, installed in December of 05, purchased the MH in February 06. It is always plugged in with the inverter / charger maintaining the charge. Is it time for new batteries?

"007" · 10-01-2007, 01:16 PM

Are they 6 volt wet cells have you checked the water level lately. My two 6 volts are 03 year and still good as new.

Sorry I see you said they are maintained do you have any lights in compartments on and were you always plugged in to shore power because the lights are operating of your charger.

RVDude · 10-01-2007, 01:25 PM

Seems a little excessive. Can you measure the amp draw? Might be something else. Another possibility is that one of the batteries has internally shorted (gone bad) thus parasitically draining the others. Test each battery individually under load. Problem is, when there is a parallel set of batteries, matching the age/brand/type is very important meaning that one bad battery will cause you to replace all. You have 2 batteries in series (to make 12v) and 2 of those 2 battery sets in parallel (to give you extra capacity).

Also, batteries prefer to be "cycled" on occasion, hence keeping them on a float charge all the time (be it either the good float or especially the bad old style "trickle" charge) is not a good idea. I'd try to get a hold of a really good charger and let it do an "equalize" on the batteries. That might rectify the situation.

BryanL · 10-01-2007, 08:22 PM

Depending upon where you are measuring the voltage, your results may be within nominal range.

Have you had any problems keeping up the electrolyte levels in the batteries?

Does the inverter/charger provide equalization or desulfation charging? (i.e. is it a battery maintainer as well as a charger?)

Have you cleaned the connections and made sure they were tight - protected them with Karo Syrup, for instance?

I agree with Jeff that batteries need to be cycled - run down at least 10% but no more than 50% with a prompt vigorous and complete recharge. I have some issues with his comments about parallel batteries and shorted cells, though.

Batteries are a commodity these days. If you do find that aren't lasting 5 - 10 years for a set, the odds are very good that it is because of how you treat them. They need exercise, proper use, and good maintenance, just like you do for a long, healthy life.

Norm Payne · 10-02-2007, 06:26 PM

Voltage is a poor way to test batteries unless you fully charge the batteries, then turn off the charger or unplug from shore power and press the store button to disconnect everything from the coach batteries. Then disconnect the cables between the batteries and let the batteries set for a few hours. Use a quality digital meter and take a voltage reading across each battery. 6 volt batteries should read about 6.35 volts.

Now check each cell with a temperature compensated hydrometer. If some of the cells are just a little low an equalization should restore the batteries. But if one or more cells are very low in each battery is is time to replace them.

Next, turn on the amount of lights to put a 20-amp load on the batteries and do not plug into shore power or charge the batteries. If you have 440-amps of batteries (normal amount for four 6-volts) leave the 20-amp load on for 11 hours. Turn the lights off to remove the load and check to voltage on the batteries and you will see 12.2 volts if the batteries are good. If lower than 12.2 volts the batteries are weak and if below 12.0 volts the batteries need to be replaced.

Yes, this is time consuming, but it is the only way to test the batteries.

If you have a 3-stage smart charger like the Trace or Heart, the batteries will be floated and there is no need to cycle them. I worked with large UPS systems for large computer rooms and the battery manufacturers told us the batteries would last just as long if we never cycled them.

If you have one of the 3-stage chargers make sure it is set to the correct options. I have checked the setting on several motorhomes and found something like 880 amps of batteries and AGM batteries, when in fact the motorhome had 440 amps and were wet cells. I ask how long it has been set improperly and the RV owners say they have never touched the settings. So check the Setup and make sure you are not over charging or under charging the batteries.

The Interstate batteries Newmar installs are "entry level" batteries and many fail within two years. Sam's Club sells the best "bang for the buck" batteries and Trojan makes excellent batteries. If you have unlimited funds buy Lifeline AGM batteries.