battery powered apu system problem.

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Old 09-06-20, 07:21 AM
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battery powered apu system problem.

I own a 2020 international LT. Posting here because I think RV folks would have a better understanding of battery powered apu systems. The truck has an autostart feature so that when you're using power and the volts drop down to 12.1 I believe it is, the truck will start and charge till the volts are 13.4 I think, for a period of time. 3 days after the warranty expired the ac in the sleeper would just shut off instead of the truck starting, and the alarms started screaming at me when using the microwave or kettle. Took it in to Internationaland spent 1400 dollars just to have them find 4 bad batteries and replace batteries. They said probably bad batch of batteries. So, they said I could replace with regular batteries 80 a piece or the gels 300, said they didn't have deep cycle, i needed to load the next morning so replaced with regular 800 crank batteries. One month later it's doing ot again. All the batteries are the International brand. The system has an 1800 watt pure sine inverter which charges the batteries if i plug into shore power which i do at the house. I really don't think that an 1800 watt inverter would fry 4 large batteries in a pack, not sure if the batteries are garbage and I should just replace with good deep cycles or if there's a problem in the system. International is no help, the place I bought the truck at or the dealer i had the work done at. All I know is I can't afford to keep replacing batteries. Any ideas? Thanks.
 
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Old 09-06-20, 07:37 AM
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Also, there are 7 batteries total, 3 to start the truck, 4 apu. They found that one battery was bad in the starting pack, 3 in the apu. I haven't pulled the batteries out yet to see which ones this time. Thanks again.
 
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Old 09-06-20, 11:32 AM
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Does the system work properly when it has good batteries? If so then it could simply be the batteries. On boats I used to have wet cell deep cycle batteries but I switched to AGM batteries. I first made the switch to reduce the chance of fire/explosion but the AGM's have had an incredible life. I like 12v batteries over 6v because I'm running a 12 volt system and if a battery goes bad I could just disconnect it and the system would continue to work where if a 6v battery dies you also have to disconnect a good battery with it.
 
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Old 09-06-20, 11:44 AM
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A 2020 needing four new batteries and now the problem is happening again one month later.
Doesn't sound like a battery problem to me.

Seven batteries..... three to start and four for the APU.
Odd number for starting so they must be 12v batteries.
Are the APU batteries 6v or 12v ?
 
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Old 09-06-20, 12:00 PM
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International LT 2020 Sleeper AC shuts off when volts get low, autostart does no

system works fine then suddenly symptoms start. 12 volts all around. Doesn't seem likely to me that I'd get so many bad batteries though I stay in the truck for months on end and they are drained and recharged everyday so get alot of use. System is pretty simple alternator charges the batteries inverter powers appliances so not sure how that would burn out batteries.
 
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Old 09-06-20, 12:05 PM
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International LT 2020 Sleeper AC shuts off when volts get low, autostart does no

also, I haven't had the batteries tested yet this time, same exact issues so guessing.
 
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Old 09-06-20, 12:16 PM
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apu

I wonder if the alternator could be faulty and overcharging?
 
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Old 09-06-20, 12:29 PM
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You have seven lead acid batteries that are getting recharged by one alternator ?
Do you know what size that alternator is ?
Seven batteries is one heck of a charging load.

My diesel van has dual 120A alternators charging three batteries.
 
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Old 09-06-20, 12:34 PM
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Apu

Not sure what alternator. It's on a 500hp Cummins x15 assuming it's pretty large, maybe heavy duty made for charging the system.
 
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Old 09-06-20, 12:43 PM
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apu

Also, system came from factory.
 
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Old 09-06-20, 01:30 PM
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Apu

So just talked to the guys here at the TA, they said they'll run an entire electrical system check which checks starter, alternator, load test on batteries for like a hundred bucks. Of course their machine is broken so I'm going to give it a shot at the Petro tonight. Good start anyways, the International place should have really done it when they found 4 dead batteries. Thinking if the system checks out as not overcharging I'll replace with decent gel deep cycles. What do you all think? I'm just wondering if the electrical check will just tell if there's too much voltage, or if it can tell if the regulator shuts off charging when the batteries are full as well. Let me know if you all can think of anything else it might be. Thanks so much.
 
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Old 09-06-20, 01:47 PM
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The alternator is regulated to a certain voltage. Typically the batteries charge to that voltage so there is nothing that shuts off when the batteries are charged. That would at least be for the starting batteries. There may be some type of charge regulator for the APU batteries but is doubtful. I believe you need a 300A alternator or larger to run a four battery APU.

The starting batteries are always online with the engine. I would hope they used some type of relay system to tie the APU into the vehicle charging system. There are diode type charging adapters that are basically useless. The APU batteries get disconnected from the starting batteries when the key is turned off.

Batteries in parallel are an inherent problem. No battery charges and discharges at the same exact rate so all batteries are not always fully charged.
 
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Old 09-06-20, 04:55 PM
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What APU batteries are in the truck? You mentioned that they didn't have deep cycle available so do you now have a mix of starting and deep cycle batteries powering the APU?
 
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Old 09-07-20, 06:45 AM
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apu

thanks PJ good to know. I wondered how the packs were both charged then separated in use. Pilot, they are all just regular 800 ca batteries. I am thinking about replacing with deep cycle gels. Any thoughts on this, type if battery or why they're burning out?
 
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Old 09-07-20, 07:18 AM
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Do you know how deeply you are discharging the starting batteries powering the APU? If drawing the APU batteries down to 12.1 volts that's 30-50% charge which is pretty low for starting batteries to see regularly. I've read that starting batteries can have as bad as 10% the lifespan (charge discharge cycles) of a deep cycle battery if deeply discharging (down to 20%).

The last deep cycle AGM batteries I bought are Renogy 100 Ah. They are only 15 months old but still going strong. They are usually used for off grid solar power systems so I'm not sure if the physical size will work in your truck.

 
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Old 09-07-20, 08:17 AM
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apu

They drop down to 12.1 a few times a day usually. I heard renogy is good but I do need regular truck size batteries. I figured regular batteries wouldn't last as long but a month seems crazy. Especially after 4 of the high dollar gels burning out in a year. I guess just have electrical system check replace with deep cycle gels hope for the best
eventually adding a solar panel might help.
 
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Old 09-07-20, 10:53 AM
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I'm a little confused...... if there are seven batteries..... why is the APU using the starting batteries ?
It should be like a motorhome where there is a starting bank and an AUX bank.

In your case..... when the apu batteries get down to 12.1 the starting batteries start the engine.
 
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Old 09-07-20, 11:05 AM
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apu

There's a ser of 3 batteries under the driver area, then there's 4 back of the cab for the apu. Assuming the alternator charges both sets and the apu runs off the 4 when truck is off or for 110 they found 1 bad battery in starting pack and 3 in the apu pack.
 
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Old 09-07-20, 12:54 PM
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Exactly what size are those APU batteries.
Deep cycle batteries are available in 24, 27, 29 and 31 series.
The 29 series size would normally be about 1000 cranking amps in a starting battery.

There is a possibility that the batteries are not being charged evenly.
It is likely that when on shore power the inverter charger is not bringing all of them up to full charge.
Whenever you have multiple batteries in a bank like you do the charging current needs to fairly high.which your inverter likely isn't.
For 4 batteries in parallel you would need a a charger in the range of at least 30 amps and it has to be automatic to prevent overcharging.
What is the charging current of your inverter charger?

A suggestion would be to allow the inverter charger charge the batteries to full then measure the battery voltage of each battery.
You would have to disconnect them from each other to get the individual battery voltage..
One thing you can do is if you have one or more batteries with low voltage charge each battery separately and then you will be starting with a even bank.

As far as gel batteries go they are superior to lead acid but I am not sure they are good value for the money.
They can run at lower voltages without damage and can be slightly frozen when discharged and can come back but they do not offer much more capacity than lead acid.
 
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Old 09-07-20, 04:41 PM
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Apu

Great advice Greg. When I have them do the electrical system check I'll see if the can test the volts if each battery. The ones in here are like 800 something ca. Good to know about gel batteries, I can get deep cycle regular batteries much cheaper and if I get decent ones they should last quite a while. When I put the new batteries in I'll charge them all fully.
 
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Old 09-07-20, 07:39 PM
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the batteries dropping to 12.1 volts several times a day is a problem and I would hope it is due to having bad batteries that cant hold a charge, otherwise you would have several charge cycles in a day and your using about 70 percent of there capacity before recharging if a gel battery has an average life of 1000 charge cycles at that depth of discharge rate you could easily hit that number in a year, if your discharging them and recharging 3 times a day and a AGM would probably be half that so 500 charge cycles so 6 months life span witch is terrible either way.
 
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Old 09-07-20, 08:58 PM
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apu

Asian ya i guess if you do the math makes sense. What kind of batteries would be best to buy with this system to get the most bang for a buck, just regular deep cycke?
 
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Old 09-08-20, 11:48 AM
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I dont know would probably just shop around looks like it may be group size 31 but not certain, having a warranty would be good to have as you are cycling the batteries a lot and you may have to read the warranty information closely as they may have different rating for commercial use but looks like you can still get 2 year warranty for some batteries like interstate, some optima models and there is a good chance you would use it may cost a little more than a cheaper battery with no warranty or 90 day warranty though.
 
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Old 09-08-20, 05:18 PM
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As far as bang for the buck a battery marked as starting/deep cycle would be it.
The bottom line is to carefully read the specs for each battery you are considering then determine where they rank compared to cost.
Your mileage may be different but here a true deep cycle battery or a gel is not a good value, even considering any benefits they may provide.
Also, you really need to be sure that all batteries are fully charged when you start out your day.
I have a sense that your inverter charger may be part of your problem.
You could also check each battery at the end of the day to see how the vehicle charging is working.
 
 

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