Aux battery issue solutions?

curtis · 09-16-2008, 11:37 AM

My aux battery gets drained really easy. It wont seem to keep a charge even after driving for several hours. All beakers seem fine, and its a new deep cycle battery that has all fluids topped off. The ferigerator seems to be a huge draw on it. The indicator plug (the red/yellow and green light) that signals battery life and charge remaining seems to show constant weakness when the engine is not running. When running......green. When not......yellow, soon to be red. So anyone with suggestions? The only modification that migh affect the battery is the inverter that also connected directly to the battery.....but its off when not in use(but still connected) So, anyone have this issue? Its a 96 E350 Thanks!

Ford_6L_E350 · 09-16-2008, 12:44 PM

You need to be able to measure voltage, not just Green/Yellow/Red.

When you are running the engine, the voltage is probably 13.5 (green?) or more. When you stop, the voltage will drop to 12.4 (Yellow?) or so. And as you drain power from the battery it will drop into the 11's (Red?).

Your deep cycle battery can handle that easily. You don't really want to drop in the 10's, the refrig won't like that so much.

So, first actually measure the voltage. Then you can tell if you have a real problem or not.

Mike

**daveb** · 09-18-2008, 09:23 PM

Curtis, Mike is totally correct but you might want to check the connections also.

Being it's a wet cell (but new) take the battery to an auto shop that has a carbon pile tester and have them check the battery. If it fails the test put it on a standard charger (10 amps will do) and leave it on overnight. Drop the charge to a couple of amps and leave it for a day at that rate. Take it back and have them test it again. If it fails, you have got a bad battery. If it does not you're going to have to do amp checks to find what's pulling it down so fast. This can be done with a process of elimination if you don't have an amp meter but can be a major PITA.

Just remember a single small deep cycle battery is usually insufficient for heavy loads. A refrigerator can pull down a little battery fast, but if it has worked well in the past the battery might simply have gone bad. Like Mike said monitoring voltage is very important even with wet cell batteries. Too many "low draw downs" can shorten the life of a wet cell battery and will destroy a AGM battery even quicker. I have used both in tournament bass fishing for years and prefer AGM over wet cell for various reasons.
Hope you find the trouble.
DaveB

skrivan · 06-27-2011, 02:55 PM

i have 2 deep cycle house batteries (not AGM). my van has been sitting for a few weeks and then when i checked for something the other night, i saw the batteries were dead. "Someone" had been in the van and left a light on for a few weeks. the batteries are only a year or so old and have not been used much ( i think i got them at costco). so, i charged them for a few days using the built-in charger (thru shore power). They read 13.6 volts, so i unplugged the power tot he charger to see if they would hold that voltage. after only 1 day, the batteries were at 13 volts---they had no load on them at all, not even alarms. From your experiences, are these deep cycles toasted? I hate to just replace them, but we are heading out for a week where i wont be able to change them if i need to. How do you actually test the battery to see if they are going to last as long as they used to? i didnt measure the voltage when they were "dead" but i bet it was down in the 10 volt area. i suppose i could run my fridge and see if the battereis can handle a few days of that.

does anyone know of a protection device to prevent over-discharge? how about that 'charge wizard' thing?

if i do need to replace these things, does anyone have a recommendation on brand?

i did search the site, but i couldnt find anything as specific as this question.

thanks....joe

jage · 06-27-2011, 02:59 PM

Deka. "someone" has been known to do that to my van, that's why I went all LED...

rockbender · 06-27-2011, 03:59 PM

Quote:

Originally Posted by skrivan

They read 13.6 volts, so i unplugged the power tot he charger to see if they would hold that voltage. after only 1 day, the batteries were at 13 volts---they had no load on them at all, not even alarms. From your experiences, are these deep cycles toasted?

I'm guessing your batteries are fine. Do this multiple times and you'll fry them, but how many times have people left headlights on and those batteries are still ok after charging?

As for the voltage drop you are seeing, that is completely normal. A fully charged battery should be about 12.7-ish volts, so the voltage above that amount you are seeing is surface charge left from the charging process (that's very summarized - there is a lot of good reading out there about proper charging, etc.) 13.6V is the "float" charge voltage put out by your charger.

One way you might determine if the batteries are in worse shape is to see if a certain load creates the same voltage drop it used to. i.e, my fridge kicking on typically will cause a 0.1v drop in voltage from the no load state. When it kicks off, the voltage creeps back up to the no-load state. If I saw a 0.2v drop from the same load, or if the batteries didn't easily go back up to the no-load voltage I'm guessing that would be a good indication that they are on their way out.

MKRyan · 06-27-2011, 10:48 PM

I've read all the battery posts and I now know much more than before, however; I still have a few questions.

I need someone to confirm that what I'm getting with my volt meter sounds correct.

I knew I needed a new house battery soon and I have one on order as of today. (Its a Lifeline AGM 4DL to replace the original battery which is going on 5 years. I went with the same brand as I know it fits dimensionally and the former owner and I got almost 5 years out of it. $450 delivered to Pocatello, Idaho. I think thats a good price?)

I thought I might also need a new battery separator because I didn't think my house battery was charging during driving. After reading about separators here on the forum I'm thinking maybe it's OK.

Here's the real question: If I plug in a meter to one of the house DC outlets I'm getting a low voltage reading due to my battery, around 12v. When I turn on the SMB the battery separator clicks after 10 or 15 seconds or so and the voltage increases to 13.2. When I turn the engine off it slowly goes down to 12.6v and then the battery separator clicks again and it drops quickly down to the voltage prior to starting the engine. I believe that sounds right and my battery separator is working.
I also checked my meter on the dash DC outlets which is reading 12.5v prior to starting the engine. When I turn the key to the aux. position it goes down to 11.5v or so and when I start the engine it temperarily drops to 10.7v. Once the engine is running after a few seconds it reads 13.2v. This also sounds right according to posts I've read. So it sounds like my starting batteries are also good.

Does this make sense? If so, why wouldn't my 'not so good house battery' show an increase in volts after driving for several hundred miles? Even if it doesn't last very long. It at least shows higher volts when charged on shore power, even if it's only for a while. My cable connections and ground seem to be good.

I'm hoping by replacing my house battery, all will be well.

Any thoughts?

Thanks,

Mike

rockbender · 06-27-2011, 11:58 PM

MKRyan - like you I'm definitely not a pro at this and have just learned a lot recently from what I've been reading. I'm working on a home build and I think one of the most valuable things I've installed is a meter that gives me both voltage and amperage readings and it has really helped me understand how my electrical system is working.

Lets see here - as you probably know, AGM batteries don't fare too well with discharges below 50%. 5 years isn't too bad of a life span, but I'll bet you could get more if you try to minimize the amount of times you have dip below that 50%ish point. BTW, that price for a AGM 4D sounds very reasonable.

Your behaviors of the battery separator sound spot on - I've got a Surepower 1315 and those are the behaviors I see. The voltage drop you are seeing when you first turn the key on is from the glow plugs and normal as well.

As for charging off of the SMB alternator driving down the road, you say that you are only seeing about 13.2 volts when the engine is running? Is this at idle or driving RPM? That voltage is typical of a 'float' charge, or maintenance charge. When you plug into shore power your charger is likely putting out 14+ volts which is leaving a surface charge on the weakened AGM battery and showing the higher initial voltage readings. Everything you've described would lead me to think your house battery is toast. Additionally, if you pull a draw (turn on some lights or the fridge) after a full charge and see a significant voltage drop (especially one that doesn't recover) that would also be a sign that the battery is done.

After you install the new battery, I would continue to do the same checks. Check the voltage periodically both after charging via shore power and alternator. Again, I can't say enough about the value of an on board meter to learn about your power usage and system health.

BTW - checked out your photo pages the other day - great stuff you two!

MKRyan · 06-28-2011, 12:11 AM

Rockbender, the 13.2 volts is when the engine is at idle. Not sure about when at rpm, I haven't checked. This is all from the driveway tonight.
I do get 14+ volts when on shorepower during charge. After I take it off shorepower the battery drops fairly quickly to 12.8v then slowly drops down to 12.2 or so. With a little useage it continues to drop rapidly and will eventually drop down below 11v. New house battery will take care of that. I was hoping my separator was OK and I think it is.

Thanks for the comments and the confirmation that maybe I'm getting wiser about this electrical stuff. I'm learning alot from this forum.

Mike

joey2cool · 06-28-2011, 01:49 PM

Agreed, your house battery is not holding a charge and that means you should replace it.

Also sounds like the house battery is receiving a charge from the van's alternator.

Also sounds like the house battery is receiving a charge from the shore power charger.

What bothers me is why the house battery voltage drop is so different when comparing measurements after an alternator charge versus measurements after a shore power charge. The house battery should drop pretty much the same way in either case. I'm assuming you are not doing anything different with regard to sufficient charging time, turning loads off, and powering off the charging source.