When is it time to change the batteries?

After being plugged to shore power for about 24 hours with the batteries connected, and then having the generator running for about 3 hours, how much battery power should I have?  I ran 2 lights and a tv (no dvd player) for about 3 hours.  I didn't notice the lights were getting so dim because it happened gradually, but then the tv went off.  When I started the generator and the lights got bright I could see the difference.  I know the batteries are old, not sure how old.  At what point do we decide to give up on these batteries and purchase a new set?  It would have been nice to go about 10 more hours on batteries with 1 tv, dvd player, and an occasional light in the bathroom.

In the best of all conditions, a good deep cycle battery will give you a bit more than five years.    Heavy discharges or improper charging will shorten that.  A faulty charger will do that as well as poor maintenance of a vented battery.  Depending on what you were running at the time, and what the draw of your TV was, 3 hours sounds like batteries about to be replaced.    Get a good set of deep cycle units as replacements, and have the operation your converter/charger checked out.  Keep your TV set small and CRT or LCD.

Well, after days of power to the converter I'd hope your batteries were as full as they can get.  you failed to mention what size they are (Standard golf cart batteries are around 220 amp hour)

To figure out what battery life should be first figure out how much power they can put out and divide by two, U-220's are 200AH and thus can deliver around 110 AH before they should be recharged,  Putting two six volt batteries in series does not change this.

Now either figure the load in amps (A standard light bulb is about 1 amp) or watts (15 watts) and total the load

Now you can convert amps to watts and the other way around (i like to use 10 when working with 12 volt just to factor in some losses along the way) so  if you are drawing an average of 10 amps, (120 watts) you have 11 hours.

20 amps 6 1/2 hours

100 amps, 1 hour

I don't know anything about the batteries, except they are old.  We bought used in the fall and the batteries were old then.  I'll get dh to check out the converter/charger.

Summer is nearly here and it's hot already.  Since we'll be camping mostly in Texas, and I can't see us going overnight without a/c, maybe this set will get us through the summer and last until it starts cooling down again.  I just thought we should get more than 3 hours from a charge, and I guess I was right about that.

THANKS!!

There are a few things you can do that might "Restore" some life to those old batteries.

First, pop the top and make sure there is enough water in them, Should be just below the split ring (NOT TOUCHING IT), If necessary top off with DISTILLED water.

Now, what converter do you have in that rig..  And does the converter have a CHARGE WIZARD plugged in to it (or built into it) if the answer to the last question is YES, stop here, that is very good and there is nothing more you can do.

One of my converters is like this.. The other one has a lot of user settings, and thus it's up to me to maintain things.  Batteries can build up sulfur on the plates, This causes them to loose capacity.  Your converter may have a setting that tends to remove this buildup.  If so you need to engage it AFTER topping off the cells.

Charge Wizard controllers do this automatically every so often

Kathy,
Not knowing what brand/type of genset you have, it's difficult to say that the batteries should have been fully charged after 3 hours. A Honda Eu1000 or 2000 on supplies about 8 amps charging, so you couldn't expect full batteries after 3 hours. On the other hand, it you are using it to power a converter/charger, it would depend on the output of that unit. As Carl said, your batteries are probably beyond hope; replacement is your best option. While you're at it, make sure your converter/charger is a 3-stage unit, one that won't boil your new batteries into oblivion from overcharging. 

cuts_up said:

I don't know anything about the batteries, except they are old.  We bought used in the fall and the batteries were old then.  I'll get dh to check out the converter/charger.

Summer is nearly here and it's hot already.  Since we'll be camping mostly in Texas, and I can't see us going overnight without a/c, maybe this set will get us through the summer and last until it starts cooling down again.  I just thought we should get more than 3 hours from a charge, and I guess I was right about that.

THANKS!!

Click to expand...

Bought used of indefinite age.  The odds are that they are on their last legs.

Let me say right now and without fear of sucessful contradiction -- you ain't gonna run A/C on batteries unless you have an awful lot of batteries, more than RVs carry.  A/C takes 120 VAC and at a minimum 30 amps.  Make that 50 amps if you have two units.  A/C at night means either running an adequate genset all night OR being hooked up to shore power.

A/C at night means either running an adequate genset all night OR being hooked up to shore power

Click to expand...

Oh, definately!  Since we will be using mostly the genset or shore power, I'm hoping we can postpone buying batteries until fall.  I just hate to get rid of these batteries while they still have some life left in them. 

The genset is an Onan 6.5.  The mh is a 1993, and my guess is the genset is the same age.  The previous owner had this mh for 2-3 years before we bought it, and I doubt he put in any new house batteries.  I don't know what the charger/converter is.  It might be in some of our paperwork.  I know dh has checked the batteries.  We carry distilled water, but I don't know for sure if he has had to add any.

Kathy,
Rather than rely on paperwork, search out the charger/converter physically and get the make/model from the nameplate. Chances are that changes have been made and are not reflected in the documentation. It's a metal box about half the size of a shoebox, and will be plugged into a 120 volt outlet and have one large red and one large black cable connected to it going to the batteries. It may be in one of the bays or behind or beneath the breaker panel inside.

I'm hoping we can postpone buying batteries until fall.

Click to expand...

I think you're living on borrowed time, and would hate to see you somewhere out in the boonies when they give up the ghost. Then you'll be at the mercy of the nearest dealer who may well charge considerably more than what you would pay if you shopped around. You didn't mention what size inverter you have (if any), but I'll second what Carl said. You'd need a ton (literally) of batteries to run the air conditioning even if your inverter were large enough to handle the power requirements. If you plan on running it from the genset, be aware that many places, even remote boondocking areas like Quartzsite, have "quiet hours' during which genset running is prohibited. Even the breeze from a small fan can help tremendously at night. 

I think you're living on borrowed time,

Click to expand...

Yikes!  I guess it's time to start shopping for batteries afterall.

The a/c won't run off batteries as it is.  I'm just saying that since we don't plan to live off batteries, but genset or shore power, maybe we can get by with what we have until later.  The engine battery is new, so we'll be able to drive anywhere, even if we have to do it without turning on the roof a/c's.

Thanks for all the input.  I will get dh to check out the charger/converter.  The only inverter that I know of is a small one installed in the bedroom for the dvd player.  We have another one to be installed up front for the front vcr/dvd player.

   

Carl L said:

Let me say right now and without fear of sucessful contradiction -- you ain't gonna run A/C on batteries unless you have an awful lot of batteries, more than RVs carry. 

Click to expand...

Let's see....

Say 12,000 watts for an ac - most are more but lets keep the math simple
That's 1,000 amps @ 12 volts assuming 100% efficiency
Batteries can sustain 20 amps for a few hours
1,000/20 is 50 batteries
50 batteries x 50 lbs each = 2500 lbs

joelmyer said:

Let's see....

Say 12,000 watts for an ac - most are more but lets keep the math simple
That's 1,000 amps @ 12 volts assuming 100% efficiency
Batteries can sustain 20 amps for a few hours
1,000/20 is 50 batteries
50 batteries x 50 lbs each = 2500 lbs

Click to expand...

Oh well then.  Tom Jones probably has that on board his Monaco right now just to run his electronics.  ;D

Joel,
I think you slipped a decimal point somewhere A 13,500btu a/c uses about 1500-1600 watts, but your point is still valid - you don't want to run a/c from the batteries.

Nah, not on the coach Carl, but I do on the boat  ;D

Tom said:

Nah, not on the coach Carl, but I do on the boat  ;D

Click to expand...

Yeah, sideways looking sonar isn't much value on the average motorhome.   Or doppler radar.

Or the "Dive!, Dive!" claxon. ;D

Do you have the ability to equalize the batteries? If so, follow you inverter manufacturers recommendations and equalize this should take about 2 hours.  By equalizing you can gain a little more life from older batteries, however, be aware that if your batteries have bad cells this could actually reduce current life.  Have a the batteries checked. Keep in mind if you you have even one bad cell you are better off replacing the whole bank of batteries.  Never replace only one battery in a bank it will decayed by other bad batteries.

JID:  Regarding your comment about the charge wizard, I use my batteries very infrequently.  I'm not plugged into shore power about 3 to 4 days a year.  Do I need to keep the charge wizard plugged into the converter?  I think it tends to overcharge my AGM batteries.  Isn't the purpose of a charge wizard to do a rapid recharge when necessary, which, in my case, is never.  In fact, those 3 or 4 days that I'm on the road, I run the generator during stops, if I need a/c, so it charges up the batteries for any lights that may be on.

--pat

No, Pat, the Charge Wizard is NOT intended to provide more rapid charging. It is an enhanced charging manager which fine tunes the charging to the battery's needs rather than just forcing it.  It provides three different levels of charging rather than the standard two.  As such, Charge Wizard is more likley to extend battery life than to harm them in any way.

I do not recommend charge wizard controlled (or controllable) converers for AGM's only Flooded Wet Cells

AGM's do need to be equalized, but only "Once in a while" not every 21 hours and that is the program in the wizard

I would like to see them come out with an AGM wizard,  Properly set for AGM batteries, but as far as I know no such plug in exists