Battery problems?

[nrhareiner]

I think I know the answer to the question, but want some conformation. My coach batteries are almost 5 years old and I had scheduled the change for October. 2 days ago when it got plugged in after 6 hours unplugged, the inverters did their thing and both showed 8 amp draw of the chargers. Inverter one then went into float mode while #2 stayed in bulk drawing 15 amps to charge (maximum allowed by my setting). It has not come out of this charge mode. I have 8 8D batteries in two banks. One bank running 10 degrees hotter than the other measured by infrared.

I think one battery has fried and getting a large draw through that battery. The batteries are only measuring 25.8 volts on 24 volt system not the normal 26.6. Is that a good guess? I am ordering the new batteries through Lifeline today if people agree with this post. Only slight problem is that the coach is in OKC not at home.

Thanks to everyone for help.

[Jon Wehrenberg]

Kim,

That sounds logical, but as you describe it you imply each inverter handles a portion of the batteries. Are you sure? On my coach each inverter handles all of the batteries. The way yours appears to be set up any inverter charger section failure takes out 1/2 of your coach unless there is a switch that allows you to merge both battery sets into one bank.

[dalej]

Kim,

It sounds like you have a good understanding of your batteries and the way they have been handling your coach.

Your at a point in the battery life that most would think it's time for a change. I think if it were my bus, I would break down each bank to get a better understanding of the condition of each battery. If they are all resting at the same or close voltage rate then I would be prone to start looking at the charging system.

You didn't say if your current batteries were Lifeline but to me that is a short service life if they are. My last Lifelines were in 9 years.

[Jon Wehrenberg]

I know for sure that as Kim stated a failed battery will ruin a set. I think in Dale's case his betteries held up very well, but I think we all know that if a battery fails at any time in its life we are going to be replacing the set.

There are a lot of factors which determine the life of batteries ranging from manufacturing defects which may ultimately create internal shorts, to just wearing out batteries by the number of discharge cycles and the depth of the discharges.

We can screw up battreries all by ourselves by charging them improperly (often without realizing it), exposing them to a high temperature environment, or something as simple as letting them go dead.

I am at my five year life right now on both house and bus and although both seem to be working perfectly I also know from previous battery failures that when they do fail, they can fail quickly and without warning so I am torn between premature replacement, or risking a trip that ends up with a bad set of batteries. Hard choice.

[nrhareiner]

It seems that when the problem started the one inverter goes to charging (as many amps as I allow the charger to draw). The other one is in float mode, and in fact may be allowing some draw from the batteries if the limit of amount of draw is reached from the electrical plug. I was set at 40 amp draw max from shore line. I was running many of the a/c units since 105 out side. With the unit drawing 15 amp charging the other inverter was actually showing a negative charge amount to accomadate the over all draw.

That may not have been written correctly, but I hope all of you understand what I am trying to say.

I was wondering if the problem was the inverter. However, then something is causing a large draw of amps from one of the chargers. It may not just be one battery, or as Jon says the charging of every battery is connected to both inverters, and one is just picking up the load.

[truk4u]

Kim,

Your drawing 15 amps for the charger, but take a look at the inverter that's doing the charging and see what DC amps are being put in the batteries. The bulk and absorbtion DC amps should slowly go down until hitting float. If the charger is putting 100+ DC amps into the battery bank and is not gradually reducing as the batteries get charged, you may have a bad battery like you suspected. If you end up testing the batteries, they each need to be unhooked and load tested individually.

[nrhareiner]

Thanks for the info Tom,

It is not gradually decreasing the dc amps. I am sure it is a battery.

Kim

[Jon Wehrenberg]

Kim,

I think I am correct, but verify this.

If you are on shore power your inverters are not pulling power from the batteries to power any of your electrical circuits, but are passing shore power through to the 120 Volt panel. In addition to passing the shore power through to the circuits powered by the inverter when not on shore power, the inverters have become chargers.

You have my attention when you suggest the batteries may actually be losing voltage.

First, that would suggest you have loads on the batteries, such as the tivolis, or a lot of lights. Obviously if the inverters are chargers then they first have to overcome the current draw imposed by those loads.

But another thing may be happening. If you have shore power going to the inverter, and it is charging, but the batteries are not getting to the voltage necessary to go into absorption mode, is it possible the power is not passing through but instead is not "seen" by the inverter, so the inverter is drawing battery current and is not passing shore power through? Even if you are runnning devices that go through the inverter when not on shore power, they should be receiving shore power when connected to it.

Try eliminating any loads on the batteries to see what is happening. If you eliminate all but phantom loads the inverter should quickly get into absorption and then float. Do your inverters go into bulk every time they are cycled? Is bulk charge based on time or voltage?

[nrhareiner]

Jon,

thanks for the reply. This bus is set up very differently from the Liberty. Everything goes through the inverters when plugged in or not. I can set a master switch to normal, shore power only, or genset only. When set in normal everything runs through inverter, the inverters will draw as much ac current as needed up to the limit I set (between 10-60 amps). After the limit is reached, then the inverter supplies the remaining amps needed from the batteries (up to 35 amps per inverter). If set to shore or gen set then that is the only source of the ac power, and the inverter is only in charge mode. When I tested this way, the inverter number two was still suppling dc to the battery in as much power (I can set the amount 1-35 amp) as I set. This has only been going on for the past three days. So I have one inverter showing bulk charge, one inverter showing float.

It may be that one bank of batteries is charged from one inverter and the other from the second inverter since there are two different banks. Each of the banks is wired for 12 volts, then the two together are wired for 24 volts. Probably not the most efficient, but that is the way it was designed.

The fact that the batteries are not getting to the normal voltage to go to the float stage tells me that there is a problem with some of the batteries. If I turn off both of the inverters the batteries still only show 25.2 volts. I am hoping that the new batteries solve the problem.

[Jon Wehrenberg]

Before you invest in new batteries you need to be sure the problem is not with the charging system or the inverters.

I'm still confused because I think all inverters work the same way. When no shore or generator power, they pull power from the batteries to power the dedicated inverter circuits. When there is power, generator or shore, they stop being inverters, switch to being chargers, and a relay transfers the 120 volt power in, to the chargers and to inverter output so the power supply is merely a pass through.

That should leave no loads on the batteries except for the DC loads, and unless those loads are excessive, the charger side of the inverters should quickly pass though the three modes for charging.

I agree the batteries seem to have an issue and checking each one will confirm that.

[truk4u]

Kim,

It seems a little unusual that the batteries all of a sudden won't take a charge. Usually, they charge for a long time if they're bad, but will go to float. Then, as soon as you take away the shore or gen power, the voltage takes a nose dive in short order.

You may have already covered this, but did you try turning off the inverter that is stuck on bulk and switch the charging to the other inverter. It's not abnormal to have one inverter on float and the other on bulk or absorbtion charge.

Just trying to help you rule out an inverter/charger problem before coughing up the big battery bucks.

[gmcbuffalo]

Jon could it be that the 120VAC wire to the inverters are only connected to the chargers side of the inverters and not a pass thru?

Kim disconnected the bridge between the two 12volt banks that makes the voltage 24volts and measure the voltage of each bank. The bank that doesn't stop charging should have a very low voltage.

GregM

[nrhareiner]

Just got back to the bus and tried some of the suggestions. It is hard to work directly on the wiring of the bus since it is already dark.

If I turn off the inverter that is in bulk, then the other inverter immediately goes into bulk charge. I had tried that and that was the reason that I think it is the batteries.

If I turn the master switch in the bay to shore power only, thereby taking the inverters out of the loop except for charging, still have one drawing as much power as I allow it to charge a battery (I can set this amount from 1-35 volts).

The only thing I have not tried is to disconnect the cables connecting the two banks making the 24 volts available.

Let everyone know more tomorrow.

Kim

[Joe Cannarozzi]

Jon there is a Trace inverter 4024 4000w 24v and all who own them go gaga over them and with good cause.

You can gang them up and they power share.

They also will subsidize less than adequate shore power or gen for that matter.

If you hook into 30 amp service there is no need to manage loads the inverters automatically make up the difference ,yes continuing to invert with a/c power going in. And when loads decrease they again automatically sneak an amp or two ta the batteries when excess power in permits.

Kim you don't by any chance have trace 4024 model do you? That would explain the negative reading you mentioned.

[Jon Wehrenberg]

Joe, your post implies that the Trace 4024 power shares and I think you are suggesting it means multiple inverters can be tied to the same 120V circuits. At least that is what I sense you are saying.

I have to check that out because I was (and still am) of the opinion that the output of inverters (not pass through power, but inverter output from the batteries) cannot be joined do to phase or cycle issues.

Are you sure power sharing is not related to using only the power available on an incoming shore power circuit so as to not overload it?

[Jon Wehrenberg]

http://www.oksolar.com/inverters/trace.htm

I see load Shaving, but not sharing, however it appears to syncronize the cycles for the utility grid, but it was silent on if it would syncronize the cycles when paired with another inverter.

Very interesting inverter.

[nrhareiner]

I guess it is time for "the rest of the story."

Here is what we found
1. One bad 8D battery, and one marginal. I replaced all of the batteries for the coach. Still had the asme problem.
2. Realized the the temperature probes from each inverter went to a different area and different bank of batteries. Went into the technician's area in the remote panel and found almost 10 degrees difference in the readings at the battery.
3. Now looked up the voltage scale reference the temp difference and found the problem and solution
4. The inverter that was "seeing" the hotter temperature (please remember we were in a heat wave, seeing 105 during the day and 85 or more at night) would not go into float mode since while the temperature compensated voltage was high enough for the float, the actual voltage was not so it stayed in bulk mode. I could change which inverter would stay in bulk by swapping the locations of the temperature probes.
5. I also learned that if the real voltage is high as or higher than the float voltage you get get an inverter that is "stuck" in bulk charge to go to float just by adjusting the time for bulk absorption to zero. Probably not the best for the battery, but still a method we should know.
6. Placed both temperature probes on the same battery, now no problems.

I guess it was worth all of the problems especially when I found the two batteries that flunked the load testing.

Thanks to everyone who helped. All of you helped me get to the solution.

[Joe Cannarozzi]

When you say the wrong batteries and different area can you specify more. Where were the sensors mistakenly mounted, the chassis batts? Other house batts. In a different location in the same bay or was it in a completly different bay?

Brilliant work for sure.

Now you have me wondering. I live in Chi. and in the winter we store outside our temp sensor is on the inverter itself tucked up in the belly of the bay like a bug in a rug and house batteries are in the frigid engine bay.

Im callin Gustdorf.

I was unaware of ANY external temp probes for moderating battery charging rates when cold, for the inverters. My Heart has that sensor built in to the inverter inself.

Great stuff

What inverters did you say you had Kim?

[nrhareiner]

Hello Joe,

I have the trace sw4024 inverters. These are 4000 amp, 24 volt inverters. There are 2 in the coach. The remote temperature probes are on two different batteries in the same bay. However, one bank significantly higher than the other so hotter due to the rising air. I do have fans that are working, but got over powered by the extreme heat.

The heart inverters do not have the remote probe (at least as far as I remember from previous bus).

The batteries that were bad would not hold up under load. When 450 amp hour draw placed against them then went below 10.5 volts after 15 seconds. The other batteries passed without problems. However, since they were 5 years old I just replaced all of the batteries in the banks.

All of the batteries live in the same bay as the inverters. The second drivers bay.

[truk4u]

Good deal Kim, glad your back in action. My Magnum Inverters also have the temp probes and their procedure is to mount them together on the negative post of any battery. When I changed mine out last month, the temp probes where mounted under the battery hold down bracket in different places. The temps, however, never varied more than a couple degree's between inverters.

I wonder if the charging lock up due to temps is specific to Trace? I discussed the temp probes at length with Magnum and they said it would slightly reduce the charging/float voltages during high temperatures.

[nrhareiner]

Good afternoon Tom,

I think Magnum is correct for "normal temps." However wit the extreme high or low outside temp situation I think it does make a difference. At least it did for me.

Kim