ATC Battery separator compatible with Lithium?

MU

Murban

Member
Joined
Aug 18, 2017
Posts
19
Location
Pleasanton, CA
Hello -
I am working on an electrical upgrade on my Ocelot and have a question related to the stock battery separator that ATC installs. The stock battery that Marty and ATC install is a 78 Watt AGM. I had ATC install 190 Watt solar panel and Victron charge controller which work great. I would like to swap out or drop in a 100 Watt Lithium battery. I plan on upgrading the truck to camper wiring to 6AWG with appropriate breaker as well. Any concerns, cautions or warnings with keeping the stock battery separator in the circuit? Eventually I will replace the separator with a Victron DC/DC 30A charger but not right now.
Thanks in advance.
Mike
 
Mike, it will work, just not perfectly. The AGM you have was 75AH, or effectively 50% of that, 38AH. Your new one is almost 3x as "big" capacity wise. The upgraded wiring will allow the alternator to push some juice into the camper. The stock wiring would disconnect too frequently to get a decent charge from the truck. A DCDC charger helps with the "too small" wiring. The other issue is that the fat wiring COULD allow your alternator to overwork itself, but I am thinking this is a very unlikely situation (there is a Australian)?) video out there showing how your alternator could destroy itself). In my rig, I have 2AWG welding cable running back to the truck, and have yet to see much more than 90A for a short period of time, which my 250A alternator has no problem with.

The Victron MPPT can be reprogrammed to work with Lithium just fine, and your onboard "IOTA" brand ACDC charger will be "good enough" to get you to 80% SOC and the solar can finish it off in most cases.

Oh, and do get the Victron Smart Shunt or BMW712 so you can see what is really going on with your battery.
 
Vic
Thank for this input. I do have a BMV712 monitor but forgot to mention that. My truck alternator is on the smaller size. I think it’s 140 or 150A. Gen1 Tundra 2006. I definitely want to avoid damaging the alternator. What is the best practice way to do this? Do you know of any posts or resources that have diagrams or pictures? Apologies if this seems remedial.
 
With the 6 AWG wire you picked, there might be enough resistance (versus the 2AWG I have) to keep the current down. You can always monitor that with the 712, and change things if needed. The solution is fat wires AND a DCDC. LiFePo4 batteries can usually handle 50% of C (Where C = the rated AH of the battery), so you could use up to 50A, and with my 200AH, I could use 100A of charge. Neither of us have the gear to generate that kind of power! But, I say this to put things into perspective. Your alternator will likely be just fine... just monitor the situation when you have a fully discharged camper battery.... what kind of current do you end up getting from the truck? Then decide what to do.

As for diagrams and such, have you seen the long threads I link to in my signature block? Also, Victron and others have great wiring diagrams on their websites. If that's not good for you, then ask away!!!!
 
Thanks Vic. I appreciate the info and it makes sense to me. I think I’ll add the 6Awg wire and dc/dc charger for now and see how that all works out. I will also check out your links.
Mike
 
Hi: On my Ocelot with a 160w solar panel.......with the ATC installed battery isolator which is connected to my agm battery, if I install a 100ah lithium battery can I connect a dc to dc charger directly to the installed battery isolator?
 
If you install lithium, you can decided if you want to add a DCDC charger. Best way to do that is to ensure that you also have a shunt based battery meter. Not a voltmeter or an "idiot light". Victron makes good ones. Then you can see better what your charging needs are. If you decide to implement better charging from the truck, you can replace the isolator with a DCDC and possibly uprade your wire sizes too.
 
Thanks Vic: I was under the impression that it will harm either the alternator (2023 chevy) or the lithium batter if charged right off the truck...w/o a dc to dc charger. I want to keep it as simple as possible. For about 5 years now my agm has worked fine...but I really only use the camper 3-4 times per year.
 
Vic Harder said:
With the 6 AWG wire you picked, there might be enough resistance (versus the 2AWG I have) to keep the current down. You can always monitor that with the 712, and change things if needed. The solution is fat wires AND a DCDC. LiFePo4 batteries can usually handle 50% of C (Where C = the rated AH of the battery), so you could use up to 50A, and with my 200AH, I could use 100A of charge. Neither of us have the gear to generate that kind of power! But, I say this to put things into perspective. Your alternator will likely be just fine... just monitor the situation when you have a fully discharged camper battery.... what kind of current do you end up getting from the truck? Then decide what to do.

As for diagrams and such, have you seen the long threads I link to in my signature block? Also, Victron and others have great wiring diagrams on their websites. If that's not good for you, then ask away!!!!
Click to expand...
Vic, I'm trying to locate those long threads in your signature block but not finding them. Maybe I need to activate a setting on this site but I'm not seeing the usual signature block info with links. I'll keep looking but if not too much hassle could you link those threads in a post here?

I just bought a new 2025 Chevy. Has 220A alternator (all I know atm). My camper is 2021 Granby with original wiring. This is my best opportunity to upgrade the wiring. Camper has the FWC installed BS ACR, two 6v agm. Also (customer installed - me) two 180W panels, Victron controller and the Victron 712.
 
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