Community Forums

astrnmrtom · 02-01-2023, 11:18 PM

Your proposed system is very close to what I'm running now, and it's works great. We have a residential refrigerator which is the primary load. Our inverter/charger is a 3000 watt psw, 900watts of solar on a single controller, an onboard generator, a portable as a back-up, and 4-100ah Lifepo4. I make my coffee in the am, the microwave for dinner and my wife uses the hair dryer, all off the batteries. It works great. With our modest system we don't use the toaster oven, air fryer or Instapot on batteries, and it's no big deal. We avoid boondocking in high temps. We feel we can live very comfortably with this system.

Like anything that produces power you'll be hard pressed to find anyone who will say: "I wish I had less" but everyone's budget and rigs are different. Oh, and my batteries are in an open compartment so I had heaters installed and have some flexible insulation I can wrap them in if needed. Like super hot weather, we avoid camping in extremely low temps. So far this winter in the Southwest, I haven't had to use the heaters. I have a battery temp monitor and even when it's around freezing the batteries are warmer than ambient. When being used, they generate a little internal heat.

For the first two years I was working with 600watts, with 4-235ah agms and supplementing with some generator time and it was enough although we had to be more frugal with out loads. Switching to lifepo4, while expensive has been well worth the cost. Not only is our capacity higher, they charge much faster which saves fuel when using the generator.

Everyone's needs are different. What I would suggest, is to design your system to be expandable should you want to add more panels later. When I added the 300 more watts this past summer, it was a simple matter of mounting the new panels and plugging them in.

Other may correct me but to get around the limits of your factory battery control center, you may be able to add a DC to DC charger set for lithium. This will also protect your alternator from being overloaded.

Good luck with whatever you decide to do.

Captain8 · 02-04-2023, 01:27 PM

Quote:

Originally Posted by SiteTrek

Magnetek 7300 and it will not work with lithium.
My BCC will not work with Lithium, nor if I replace the house batteries with lithium, they will not work in an emergency start situation.

Your inverter will work with lithium it just doesn't have a charging profile so will charge at a higher voltage. Not sure if you could just set it to inverter only mode then get a charger for lithium or what options you have.

The BCC will work fine but you have the same problem as the alternator will charge at a higher voltage. Battleborn makes a device to solve this or there's other options like setting up a relay so the alt start button works but doesn't use the alternator.

Just FYI I just pulled the fuse in my BCC for the alt start and it's been great. Actually my alternator died this weekend on a 4 hour trip and we just put the fuse back in then ran the Genny. We're on the way back and have a few more hours to go now and my solars making more power than we're using so no need for Genny to be on.

Not sure why you don't think the aux start will work with lithium. Sure if the bms can't handle the full amperage it'll be an issue but it's the same problem with lead acid house batteries

SiteTrek · 02-05-2023, 12:17 PM

Quote:

Originally Posted by Captain8

Your inverter will work with lithium it just doesn't have a charging profile so will charge at a higher voltage. Not sure if you could just set it to inverter only mode then get a charger for lithium or what options you have.

The BCC will work fine but you have the same problem as the alternator will charge at a higher voltage. Battleborn makes a device to solve this or there's other options like setting up a relay so the alt start button works but doesn't use the alternator.

Just FYI I just pulled the fuse in my BCC for the alt start and it's been great. Actually my alternator died this weekend on a 4 hour trip and we just put the fuse back in then ran the Genny. We're on the way back and have a few more hours to go now and my solars making more power than we're using so no need for Genny to be on.
Not sure why you don't think the aux start will work with lithium. Sure if the bms can't handle the full amperage it'll be an issue but it's the same problem with lead acid house batteries

All I can say is the tech at M&M says the BCC will need to be changed or additional parts in the system if I change the "house batteries". The tech at ampertime, and Weise say the surge capacity of their batteries will not work for emergency start. Since the inverter is not adequate either, I figure since I want to have more battery than my house battery location can handle, I'd leave the current system intact and have another system for about the same money and less work.

Captain8 · 02-05-2023, 03:36 PM

You should ask why instead of just accepting what someone says. It's because the alternator voltage is higher and can easily just be disabled by pulling the fuse.

I doubt the Lead acid you have is adequate to fully start but I'm not sure. Also you can just carry a simple $100 1400CCA jump pack for emergencies. Also allows you to use it for toads or other toys.

paul65k · 02-05-2023, 03:45 PM

Quote:

Originally Posted by SiteTrek

Magnetek 7300 and it will not work with lithium.
My BCC will not work with Lithium, nor if I replace the house batteries with lithium, they will not work in an emergency start situation.

Does that mean it won't charge AGM batteries as well??

Captain8 · 02-05-2023, 08:23 PM

Quote:

Originally Posted by paul65k

Does that mean it won't charge AGM batteries as well??

I'm not sure what options the inverter has but AGM charge profile is similar to lead acid. Lithium has a lower voltage than either and the high voltage can damage lithium. Lead acid and AGM both increase voltage relative to their charge percentage, where lithium basically stays at the same voltage until 80% or more than is just a bit higher. On top of this lithium can charge a ton more so can overload an alternator (or wiring) as it'll basically pull as much power as it can.

Google how to change the inverter to AGM charging profile and see if there's any options.

paul65k · 02-06-2023, 09:11 AM

Quote:

Originally Posted by Captain8

I'm not sure what options the inverter has but AGM charge profile is similar to lead acid.

Actually it's not as the AGM profile will typically charge to 14.4 and some as high as 14.6

Flooded batteries are more like 13.6-13.8.

If your Inverter/charger or converter has an AGM profile it will charge LiFePO4 batteries to 100%. Granted it's not quite as elegant as a charger with a lithium profile and the BMS needs to do some of the work but it will charge the batteries..... assuming you can put enough amps to keep up with the needs but it will definitely do the job and it will charge the same amount of Ah faster on lithium than flooded LA

SiteTrek · 02-07-2023, 10:39 AM

Quote:

Originally Posted by paul65k

Does that mean it won't charge AGM batteries as well??

I do not know about the AGM's but I would assume it would.

SiteTrek · 02-07-2023, 11:03 AM

All I can say is that I want to keep the emergency start as I have had to use it on two occasions. One to start the motorhome and another to start the generator.
The tech at M&M who is Magnetek's factory rep says my BCC will not adequately charge the lithium batteries without a DC-to-DC charger.
If I get that and installed, the battery companies say the lithium has to low of a surge to use as an emergency start for the motorhome so then I have to buy a jumper battery.
The next issue is if I buy a DC-to-DC charger, a jumper battery, my house battery location (under the steps) is exposed to outside temperature, not to mention if I want more than 200ah of batteries they won't fit in that location.
Next M&M says my 7300 will not charge the lithium adequately.
The more I look into this, I find it easier, more efficient and little to no difference in cost to leave the motorhome system alone and install a standalone system that is also a backup. I can even take it out and transfer to another motorhome or sell and upgrade.

eblues · 04-07-2023, 10:03 AM

I'm just finishing up a solar project which includes lithium batteries and a Victron Multiplus II 3000 2x120 inverter. I opted to use the original battery location, which is toward the front of the coach and I'm having to seal and insulate the battery compartment which is a pain. But I'm glad I went that way because the Multiplus inverter is pretty noisy and I wouldn't want it mounted near or in the bedroom. FWIW.