Battery powered rooftop AC installed in my sleeper.

Those AGMs can only accept power so fast. Lithium with take power much faster.
I dont think you will see faster charging with the 300 either but it should run cooler and be safer

 

I get a lot of Hendrickson parts from FindItParts. No complaints.

If it's a pad mount Delco, the literature suggests 300W+ it could only be a 40si, which is supposedly higher efficiency than the lesser models. Supposed to run cooler and cost less fuel to spin.

Still 7-8 hours to recharge seems excessive. How low do you let them get before chickening out and starting the engine? Before the solar panels, two hours on the road is about my max time to see 13.9-14.0V again after a hard a/c run. I usually get nervous at 11.7V and turn the key. Or sooner if it's bedtime and I need the a/c to run all night. Fast idle for 30-45 minutes gets it to the 13.5 range and gets it done. Of course, while idling the 120V a/c is turned off and unplugged since the truck a/c is available for no extra charge, pun intended. I guess the only way you could see what's really going on there would be to use an inductive ammeter on the battery and alternator cables during a hard charge cycle.

Old batteries maybe? Green cancer in any of the battery terminals? For what it's worth, I swapped the factory installed (less than a year old) standard AGM for a set of 3 year old Northstars out of a truck I traded. The Northstars last about 25% longer before they hit 11.7V, but do not charge any faster than the Mack batteries that came out.

 

That's right. Thanks for the recap for weak memory capacity.

That said, I re-read your OP where you mention the Victron 30A DC/DC charger. Looking at the product, that both answers my question and raises another concern.

Using that, you're limiting the house battery charge current to 30A. That's why it's taking so long to charge. The incoming 300A alternator will charge no faster than the 200A you just got. In order to exploit your alternator's capacity, you need to use a relay style isolator like the motor home people use. Victron has a variety if you like their products, as do others. You need something capable of passing much higher current into the house battery set. None of these seem to have bluetooth apps, so you won't be able to monitor things on your phone if that's a deal breaker. The only cautionary note from looking over that Victron page, is these are input rated. So choose one sized to your alternator versus what you would like to see passed through to the batteries. If you're concerned about too much charge current, check the specs or just call/email the company and ask for a recommendation.

Victron also has a mention of some models similar to the one you have, where multiples can be installed in parallel to increase charge current. At first glance it seemed to me the charge current payoff versus cost/complexity of the setup doesn't add up. At least to me anyway.

With that in mind, the charger you use now also would reduce the load on your OEM alternator to 30A added to truck demand. Hardly enough to bump capacity on a 135A or so OEM model enough lead it to an early death. Maybe it was just time for that one to die and the little 30A continuous you put on it pushed it over the edge?

 

You can also get a 60a b2b charger. Look at sterling power.

 

@trukitt was just thinking about this thread and wondering if you were ever able to make any changes to improve the house battery charge rate? and if you installed or canceled that 300A, and if so how'd that fit and work out?

 

This thread is great. Anyone consider a separate dedicated alternator? The trade off would be lost HP. That happens anyway though with higher amp alternators. I’m reminded of an old man, 40 yrs ago. He had dual batteries and alternators on his old 68 Chevy P/U Truck. He was quite innovative. He had a home made contraption for swapping engines. Built from an old full size GM car frame. Used the engine to run a chain driven hoist. Old engine out, new engine in. All balanced by each other. It was ingenious.

 

Thought about it, havent put in the time to figure out where to toss it, maybe on the fan-belt to prevent extra parasitic power loss/give it some on/off capabilities, alternately, delete ac compressor and run all electric ac for everything. maybe someday, but not this truck.

 

@trukitt thanks for the update. I have also had to delay making some wanted improvements to my own setup due to other priorities. Also, getting into the hotter part of summer and working around some shortcomings.

I agree some solar charging would help your apparent main issue of recharging the house batteries pretty much any time the sun is up, as that's really reduced that concern with mine. Even after hitting the batteries hard with less than ideal overnight conditions, I'm usually back fully charged in 2-3 hours on the road most times.

Luck also plays into solar. Some times you roll into a place to park and take what you can get, which may have you facing away from the sun, or in the shade of a building, trees, or other trucks. Other times, you can be picky and park in an ideal spot. It can make a huge difference. My current setup (480W panel capacity on an mppt charge controller) will charge as high as 35A when the sun is high in front with clear sky. Usually it's 20-25A with less ideal sun angle, and down hill from there if there's cloud cover. And of course zero at night. The saving grace is: it's on all the time. Runs in parallel with the truck alternator when driving. When I'm parked at home, batteries are at 100% when I get ready to go back out.

"Ideal" throws another curve, in that with a rooftop solar setup, facing into the sun which also heats up the cab and makes the hvac work harder. So a more solar dependent solution isn't universal or without setbacks. I do have a 2kW Honda suitcase generator but haven't taken it with me. So far, I've only needed to idle the truck no more than an hour or two on the worst days. Sunday night was a good example. Came into Atlanta (fully charged) at 6pm, low 90's and heavy overcast/storms so parking/sun angle didn't matter at all. Hvac did fine, but at 9pm I knew it wouldn't hold up all night and idled (bumped it to 900 rpm) for about an hour before sleeping. I had to take off before sunrise for an 0500 delivery, and had more than enough battery left to crank up.

That case in mind, a 400Ah LiFePO4 house battery bank, that could safely be run down to 0% capacity without depleting the truck batteries, would likely have run the hvac all night trouble free. Some day when I have free time to do it and a spare $2000 laying around, that's the next direction I think I'll take. In the mean time, I'm satisfied with idling only 10% of a break, and never during a delivery stop, to stay comfortable on the worst days.

Funny story. I did have a moment of pride last week when dropping off a trailer at my local Thermo King dealer for some repairs. The service manager is a good guy and I've been a customer there for a decade, both trailer units and Tri Pac's on my old trucks now and then. When he came out to check in the trailer, he immediately spotted the panels on the roof and mini-split on the back of my cab and started asking questions. Of course, they sell a battery powered apu and he was impressed how mine was working out. Not gonna lie, it was re-assuring to hear positive feedback from someone I knew and trusted to offer an unfiltered opinion.