Need some guidance

[Ricky]

So I have a 08 Prostar with a ISX and Ultrashift. I replaced the factory 1200 watt inverter with a Xantrex Freedom SW 3012 3000 watt inverter. I got it for 230.00 from a guy that upgraded his RV. It works great and has the control panel also. I did the upgrade because I use the inverter to run my roof mount AC. It's a Coleman rough neck 15000 btu and I installed a easy start. I only use it while driving and on high it pulls 1500 watts. When parked I have a generator that I use to run it. I do mostly short haul and I usually have my two French Mastiffs with me. That's why I like the roof mount, I have problems with the bunk AC. I used the setup last year with my 1200 watt inverter and just did the upgrade. It has been really muggy this year and the 1200 watt was kicking off. It used to only pull about 1150 watts but that was on low. But my issue is the new inverter is pulling the battery voltage (by the control panel) down to 10.9 at 1500 watts. Batteries are 1 1/2 old 950/1100 and are a good battery. Alternator is a 215 amp and is about the same age as the Batteries. So to keep from messing something up in the long run, what should I do. Bigger Alternator, deep cell batteries, both??? I talked with a place here about building a bigger Alternator from the old one I took off before. They said that they would have to look at it before they can tell how much they can bump it up (the numbers are not on it). What are the pros and cons doing that or buying bigger. My front AC works pretty good but the rear is a pain in the rear.

[JimT]

So you're saying that, while driving, the roof AC through the inverter is dropping the battery voltage reading down to 10.9 volts ?

First thing to check is the alternator itself. If you've been running that kind of load constantly while driving then it may have strained the alternator. Make sure it's still outputting the correct power.

Second thing I'd do is check each battery and make sure you don't have one with a bad cell.

Then check all the connections and grounds.

Finally, see if there's any place you can shorten the length of the battery cables or upgrade to a bigger sized cable. 4/0 all the way from the alternator to the batteries to the inverter would be the best. The longer the run and the thinner the cable the less current it can carry. My Xantrex 2000 watt inverter recommended minimum of 2/0 cables at a length of 5 feet or less from the batteries.

If none of that helps then you probably just need a bigger alternator to supply more power for your application.

Under heavy load the voltage will fall. By itself it's not a problem. The problem is, however, if you operate for long portions of the day like this then the batteries will not be charged by the system. They need to see between 13.6 and 14.3 volts (depending on the type of battery) in order to charge properly. If your loads are constantly so high that they don't spend enough time charging, then you will shorten their lifespan and find yourself with weak/dead batteries.

If you're looking for some high quality cables made to whatever sizes you need, then try https://www.batterycablesusa.com/. I've replaced nearly all my cabling with stuff from them, some 2/0 but mostly 4/0. All much better quality then anything most shops or dealers carry and they are fast to ship.

[Waterloo]

They make a 300+ amp alternator for these trucks, they are a bit pricey, but more than likely your issue. The car stereo guys call this issue you are experiencing “The Big 3”... As in upgrade the alternator, the cabling and the battery(s). I would do all 3, and even install a house battery if you have room in the sleeper. I use all 1 or 0 gauge copper welding cable with copper lugs, with an X2Power group 31 deep cycle AGM battery in my closet on a 500 amp isolator to power my stereo. Sounds like you need to do “The BIG 3”.

[Rawze]

first of all,.... a 1500Watt load on an inverter is actually a 1806 watts draw on the DC side of it. This is because an inverter under full load is usually about 83% efficient under real world testing despite the inverters ratings.

if your voltage is dropping that far down, due to inadequate wiring size from alternator, or alternator or batteries getting weak.. that is roughly 180+ amps. -- The truck itself needs another 85 - 96 amps to run itself, so that is a total of roughly 276Amps load. -- Your alternator is WAAY TOO SMALL!. The rule of thumb on a continuous duyt load on alternators is a factor of 1.4 ... -- and also, the likely-ness of the factory alternator wiring from the alternator to the batteries not being big enough is also high. Unless your truck was specially ordered with high current alternator and bigger wiring harness... your going to need to replace the wiring from alternator to batteries to make it right too.

* A 325-Amp alternator. It is a standard size and is big enough to hold the continuous loads of 2100-2800 watts. I got one for my own truck at fleetpride a few years back. A standard pad-mount 315 or 325 leese-neville alternator works just fine.

* A high-torque (or toothed) belt for the engine. ..
   
I use this belt. It is difficult to find the exact one with the extra gripping-power, most places sell the cheaper non-gripped version of the belt. Here is the correct one...
https://www.summitracing.com/ga/parts/ce...2/overview
or
https://www.walmart.com/ip/Goodyear-Belt.../473358550


* Al least 2/0-awg but 3/0-awg if you want less than 3% voltage drop. All the way from the alternator to the batteries. And might as well use same gauge wire to the inverter too while your at it.

* (for your 1500W inverter) 180-amp fuses at the batteries for the inverter. DO NOT put in bigger fuses than your system can supply. Let the fuse blow to remind you that you are using too much power on the inverter than your truck alternator can handle ... keep spares handy.

* An inverter that has a continuous rating of 1500+watts and peak surge of roughly 2,100-w or more. You say your is 3k... this should be big enough... but you should not be using much more than about 1500-1600 off it total ... unless you want to go even bigger with the alternator and wiring.

* The better quality and lower amperage 700-cc amp AGM-GLASS-MATT batteries. I would install at least 6 (instead of 4) of them for the loads you describe and truck. Battery boxes are avail for the passenger side of truck for optional electric APU's. Might as well install 8 (2 sets of 4) if your going to install the second battery box. -- Higher than about 750 or so CC amperage batteries will only puke out on you prematurely as the plates in the 900+ and especially those 1100+ batteries are way too thin for to handle the high loads your placing on them.

this is the reality of what you are trying to achieve according to your post above.... Stop under-thinking it, you have underestimated your actual loads ... You want to do it right,... that is how it should be done.

[Ricky]

(06-24-2020 )Rawze Wrote:  first of all,.... a 1500Watt load on an inverter is actually a 1806 watts draw on the DC side of it. This is because an inverter under full load is usually about 83% efficient under real world testing despite the inverters ratings.

if your voltage is dropping that far down, due to inadequate wiring size from alternator, or alternator or batteries getting weak.. that is roughly 180+ amps. -- The truck itself needs another 85 - 96 amps to run itself, so that is a total of roughly 276Amps load. -- Your alternator is WAAY TOO SMALL!. The rule of thumb on a continuous duyt load on alternators is a factor of 1.4 ... -- and also, the likely-ness of the factory alternator wiring from the alternator to the batteries not being big enough is also high. Unless your truck was specially ordered with high current alternator and bigger wiring harness... your going to need to replace the wiring from alternator to batteries to make it right too.

* A 325-Amp alternator. It is a standard size and is big enough to hold the continuous loads of 2100-2800 watts. I got one for my own truck at fleetpride a few years back. A standard pad-mount 315 or 325 leese-neville alternator works just fine.

* A high-torque (or toothed) belt for the engine. ..

I use this belt. It is difficult to find the exact one with the extra gripping-power, most places sell the cheaper non-gripped version of the belt. Here is the correct one...
https://www.summitracing.com/ga/parts/ce...2/overview
or
https://www.walmart.com/ip/Goodyear-Belt.../473358550


* Al least 2/0-awg but 3/0-awg if you want less than 3% voltage drop. All the way from the alternator to the batteries. And might as well use same gauge wire to the inverter too while your at it.
* 180-amp fuses at the batteries for the inverter. DO NOT put in bigger fuses than your system can supply. Let the fuse blow to remind you that you are using too much power on the inverter tat your truck can handle ... keep spares handy.

* An inverter that has a continuous rating of 1500+watts and peak surge of roughly 2,100-w or more. You say your is 3k... this should be big enough... but you should not be using much more than about 1500-1600 off it total ... unless you want to go even bigger with the alternator and wiring.

* The better quality and lower amperage 700-cc amp AGM-GLASS-MATT batteries. I would install at least 6 (instead of 4) of them for the loads you describe and truck. Battery boxes are avail for the passenger side of truck for optional electric APU's. Might as well install 8 (2 sets of 4) if your going to install the second battery box. -- Higher than about 750 or so CC amperage batteries will only puke out on you prematurely as the plates in the 900+ and especially those 1100+ batteries are way too thin for to handle the high loads your placing on them.

this is the reality of what you are trying to achieve according to your post above.... Stop under-thinking it, you have underestimated your actual loads ... You want to do it right,... that is how it should be done.

I want to thank everyone for the great advice. So first off I'm going to get the 325 alternator and enough cable to go to the batteries and the inverter. I really like the belt too, that's also on the list. The wire to the roof mount is a heavy outdoor house wire.I also used it from the inverter to a wall plug I added. So I should be good there. When I added the bigger inverter I kinda figured I would have to do some upgrades with it. Yesterday I took the cover off the AC and cleaned the coils on the roof mount and the truck. I was able to turn the roof down to low so it's pulling about 1150 watts gets it down to 11.5 volts. I need to get everything rounded up and get it done over a weekend. Will the ground wire be ok if left factory?

[smorgan87]

Rawze. Thanks for doing that math for me. I was thinking it was around 200A on the DC side. Theres a reason ac compressors are engine driven, id recommend fixing ur bunk hvac as that a 320A leece neville is about $1500. Also the rooftop compressors arent usually designed to run while bouncing down the road and will prematurely fail. A lot of money spent when it probably wouldnt cost $500 to just overhaul the factory ac.

[Lonestar10]

the drag that has to be putting on the engine along with the front hvac the money you would save in fuel would pay for whatever needs to be fixed in the bunk hvac.....or just put a clamp on one of the water lines to the heater cores and the cab AC should freeze you out.

[Ricky]

(06-24-2020 )smorgan87 Wrote:  Rawze. Thanks for doing that math for me. I was thinking it was around 200A on the DC side. Theres a reason ac compressors are engine driven, id recommend fixing ur bunk hvac as that a 320A leece neville is about $1500. Also the rooftop compressors arent usually designed to run while bouncing down the road and will prematurely fail. A lot of money spent when it probably wouldnt cost $500 to just overhaul the factory ac.

I did my homework before I bought the roof mount. It's the Coleman Mach ?(can't remember the number) Rough Neck Ultra low profile. They are made to use in a rugged off road environment and has an amazing warranty. The truck AC would be fine if it was just me. But I always have at least one of the Dawgs with me sometimes both. Their big girl's and don't care much for the heat, lol. As far as the issues with the bunk AC, I have had to learn so much and fix so much on the truck because you just can't trust many people anymore to fix stuff right. That and my work load really doesn't give me the pleasure of leaving the truck somewhere. I fix most everything on weekends and I'm just not feeling tearing into the back AC. I don't mind doing the bigger alternator and wiring because it will be better in the long run. This truck is here to stay, I've done to much to it to not keep her.

[Waterloo]

It is very rare anything goes wrong on the ProStar sleeper side of the HVAC. The only thing I have had to replace over the years I have owned my 08 ProStar is the blower motor.

Up front under the hood I installed one of these 12volt valves on the inlet hose to the heater core, I have a deadman’s switch on the dash, HEAT up, COLD down, OFF in the middle. {link invalid}

I also installed three of these yacht fans, they move some serious air and our extremely quiet. https://amzn.to/382kC37
Two in the sleeper just below the top ac vents and one up front hanging from the overhead. I have the fans on these remote switches so I can turn them off or on while driving. https://amzn.to/3806GGT

The AC in my ProStar will literally freeze you out. I have been in the middle of TN in July at 3pm on a blistering summer day and had to turn the heat on, it gets that cold, and is not at all comfortable.

For all of my AC parts, I like these guys out of Atlanta. They normally ship the same day your order is placed and they do sell many OEM parts at huge discounts. I have used them for a few years without issues... http://www.truckersac.com