Quote:
Originally Posted by 1der
Okay, looks like we have some Li gurus I can consult with based on a couple other threads. Suggestions for following scenario:
Usage environment is true four season. Sub zero F winters to 100F plus summer days. Solar 360w fixed plus 200w supplemental. Alternators 2 x 110amp. Draws are typically 40 to 50 amps overnight for two fridges, lights, water pump, Espar heater if needed. If using the microwave I usually start the engine and high idle to compensate for the draw but w Li I would probably just run the microwave. Spec was/is to provide enough Ah capacity to operate two to three days w minimal solar input due to weather and not starting the engine gif charging.
Current setup is 2x175sh AGM plus 2x65Ah AGM for total 480ah bank mounted under on frame. The 175Ah batteries are doing okay but are going on 4.5 years of well cared for use. Resting voltage of around 12.6 at 60 deg F.
IF there is a legit viable Li setup I would be up for creating an insulated underfloor compartment w a little heat from the Espar, plus possible AC cooling from rear engine driven compressor. I would love to build a Li battery bank or is the SOK 200Ah units. The benefit of building my own Li bank is the format could be a non-standard size that is flat and wide vs Group 31/4D format.
I would look at building a 200 to 400 AH Li bank as the replacement for the 2x175Ah batteries. The 400Ah level would provide a bit of extra capacity for water heating via 12v element.
Help me decide - stay with AGM or transition to Li ??
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I started on the DIY LiFePO4 route before seeing these off-the-shelf lithiums. They are quoted at $575 for 100 Amp-Hr.
https://www.sokbattery.com/products/...f=h-cvbzfahsek
In contrast to the DIY route the going popular config duration is a 280 Amp-hr 4S battery with ha single BMS single battery set.
https://www.aliexpress.com/item/1005...%2315616%23728
You could easily double this by paralleling cells and still keep a 12V 4S configuration. Alternatively, you could double a smaller size like the 130 Amp-Hr. Looks like there is also 310 amp-hr set without needing to double up.
Obviously, Li is available and doable the question of how much time you want to spend making a DIY setup work. You can probably do a Victron setup but much more expensive. Are you electrically inclined?
The first problem is building the battery bank. If you but that off the shelf about of 1/2 the problem go away if you can trust the product.
The next set of hurdles is the alternator charging usually has done with a DC to DC converter as being discussed in the hood-mounted solar thread. Given the capacity you are talking about you can get into a situation of stressing the alternator trying to push 40-60 amps to the battery bank at idle.
Finally, you have compatibility of these things with your existing system From the issues I'm hearing you want a solar charge controller that has independent connections for solar, battery, and load.
As far as environmental concerns, you have to keep the batteries from freezing. I think a little air circulation for the BMS will be sufficient for 100 degF. A DIY setup would lend itself better to this than the 100 Amp-Hr standard configuration.
Anyway, these are not an exhaustive set of considerations but at the forefront of my consciousness because that is what I'm finding out as I design my DIY system and interact in the various threads.