this should raise a few eyebrows

brettb · 02-15-2022, 07:33 PM

hello everyone, our 1991 roadtrek deep cycle battery is shot,I want to put a lithium battery in under the storage compartment on the drivers side, there so light and easier for this old guy to lug around. the ground cable is connected to the body, the positive cable comes into the box from the battery isolator, could I hook up my 300 watt pure sine inverter to these wires instead of the deep cycle battery, then plug in my lithium battery charger to the inverter and hard wire the charger leads onto the battery terminals ? I have everything already at home , I did a test with 2 deep cycle batteries yesterday, the dead battery was getting a charge in this set up as I had hooked up the inverter and charger this way, but with no alternator, I know I am missing something, maybe a few bricks, seems like it might work, seems like a good idea thanks for any input, comments, funny one liners, I will take any info I can get.
thank you

markopolo · 02-15-2022, 08:06 PM

It could work for a 20A charger. You'd also need to wire the new lithium into the coach DC distribution panel. I'm guessing you'd leave the coach converter/charger in place for battery charging when plugged in the grid.

Avanti has topic on this concept: https://www.classbforum.com/forums/f...-dc-12897.html

booster · 02-15-2022, 08:38 PM

I also think it could work, but I think if you are also going to run the lithium charger off of shore power you would need and automatic transfer switch to switch from inverter to shore power.

Also make very certain about bonding issues between neutral and ground. Small inverters are sometimes internally bonded and sometimes not. You must be sure there is not bond in the inverter if it stays connected when you are on shore power.

brettb · 02-15-2022, 08:41 PM

thank you, no the old 31 year old battery charging technics will be disconnected, I found the manual on line for the progessive dynamic panel inside, we don't go to many campgrounds so will un hook anything that has to do with shore power charging.

brettb · 02-15-2022, 08:51 PM

that just got the old mind thinking , if we did stay inside a campground, i could just unplug the charger from the inverter and run an extension to the outlet post on the site, one for the the van, and one for the charger, ok , now spring just got further away, thanks for the info.

TomF · 02-18-2022, 06:29 PM

I'm not sure what you intend to do here. It sounds like you want to install the lithium battery in place of the old deep cycle house battery, then install an inverter feeding from the lithium, then install a battery charger feeding from the inverter to charge the lithium. The battery would be charging itself! If it works, you could make billions of dollars selling the system.

brettb · 02-18-2022, 06:48 PM

hey tom, no was thinking of the neg cable and pos cable inside the battery compartment, installing a 600 wat pure sine inverter I have to those 2 cables, plugging in a noco battery charger into the outlets of the inverter, hard wiring the 2 charge cables from the battery charger atop of the battery to charge the lithium as we drive, i am also looking at installing a volt meter so i can keep a eye on the voltage of the battery, hoep this made better sense.

TomF · 02-19-2022, 06:21 PM

Quote:

Originally Posted by brettb

hey tom, no was thinking of the neg cable and pos cable inside the battery compartment, installing a 600 wat pure sine inverter I have to those 2 cables, plugging in a noco battery charger into the outlets of the inverter, hard wiring the 2 charge cables from the battery charger atop of the battery to charge the lithium as we drive, i am also looking at installing a volt meter so i can keep a eye on the voltage of the battery, hoep this made better sense.

Okay, gotcha. I was confusing the cables in the old battery box with the cables in the new battery box.
I am not a fan of inverting DC to AC and then AC back to DC. Seems like a waste of power. I had to do this on my Lithium battery for my outboard motor on my little boat. It came with an AC charger, and I had to use a small inverter on the big boat to run the charger. Later, a DC to DC charger became available, and I now use that. I am new to using lithium in vehicles, and the charging needs of lithium batteries, but I wonder if you couldn't get a DC to DC regulator/charger for your lithium?

avanti · 02-19-2022, 07:47 PM

Quote:

Originally Posted by TomF

I am not a fan of inverting DC to AC and then AC back to DC. Seems like a waste of power.

The counter argument is that you are only "wasting" power when your engine is running, and the amount wasted as a proportion of what is available is insignificant.

I was a long-time skeptic of this approach until my upcoming build forced me to think through all the technical details of designing a robust and automatic charging system for a large lithium bank. After doing so, it quickly became clear to me that the advantages of dc/ac/dc far outweigh the tiny energy cost.

I started a thread on this topic a while ago in which I lay out the arguments.

engnrsrule · 02-20-2022, 05:37 PM

I did major electrical upgrade on my RT- battery, inverter, charger. (Detailed in my posts). The ATS is necessity (I have 2). And in the setup it is best to automatically lock out the battery charger when the inverter is supplying power. It is not a perpetual motion machine. (My detail shows how I accomplished this).

https://www.classbforum.com/forums/f...ade-10087.html

You may also like: