Lithium - Charging
Picked up a couple 12v 100amp-hr Lithium batteries off amazon ($150 each delivered including bluetooth monitoring). My charger has a lithium setting and I have 240w of solar. I've had them installe...
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another factor that a lot of people don't even think of when we are talking RV batteries is the charging rate. so when cycle life is determined, by eve for example, they have the cell in compression, and they charge it to 100% at a 1C rate so my 304Ah cells are charged with 152 amps. they charge to 3.65V/cell so 14.6V for a 12V pack at constant current and then switch to constant voltage when the cell hits 3.65V and hold it there until the amps drop below 0.05C so 15.2A and then they consider it fully charged they rest for 30 min, then discharge with a 1C discharge to 2.5V (10V for 12V pack) let it rest for 30 min then recharge and repeat.
when the capacity is reduced to 80% of the original that is considered the cycle life.
so if you notice they are not giving stuff much of a chance to really cool down and are charging and discharging at higher than recommended constant use, as my data sheet for my cells recommend constant charge and draw stay at 0.5C. when I charge, even if I am plugged in and leave my solar on I am pumping 60A at most into that, if I start the truck up and add the dc to dc charger I can take that to 80A so at most I am putting in just a shade over 0.25C which means I will not be generating anywhere near as much heat so I expect we are extending my cycle life with the way it is charged and drained. now there will always be that exception, the guy with 2000 plus watts of solar and a smaller battery bank that comes close to a 1C charge but I would say a good majority of people with lithium don't even come close to those charge rates and I think people get way to hung up on reducing operating voltage and worried about hurting the life. the life of the battery is based off a 100% to 0% to 100% cycle so if you take care of it in other situations (cold charging, long term storage which eve defines as over 3 months, and not leaving it at 0% for extended periods of times.) you should get the cycle life stated.
like I said in my other post the only reason I set a 10% bottom is that is where it drops below 12V and rapidly drops to 10V so for the stability of the electronics I cut this part out. it probably won't hurt the electronics either but as voltage drops for a given 12V piece of equipment the amperage it consumes raises to maintain the same wattage rating so by limiting the lower voltages you can actually protect cheaper built 12V electric equipment as the cheep stuff will use wires that are to thin and other things. I actually think the problem people have been having with fantastic fans burning out are more from under voltage than over.
No problem there. It's a 35amp charger and 240w of solar, so even if both are maxed out that's just slightly over 0.25C on a 200amp-hr battery bank.
Mostly upgraded for the 12v fridge which was marginal on a single 12v 100amp-hr lead acid making it thru the night. Now I'm estimating I should be good for 2-3 days even if the solar isn't putting out much. If the solar is producing, it should be good pretty much indefinitely.
does your 240 watts of solar recover the overnight usage and power the fridge during the day? I have 325 watts on my truck camper and I am thinking of upgrading that and putting an inverter in.
On sunny days it seems to but not on overcast days...only had the battery upgrade for 2 weeks.
ok, I am just trying to get a mental picture of how much solar a compressor fridge will need as I have never had one, but if I need to replace the fridge in my camper or buy a new one I don't want my options limited by that if I can help it.
ya overcast days are the worst, but that's why I build my systems a little different than the norm. I will figure out my overnight usage and my total daily usage and I size the solar to have the overnight usage replaced by around noon. then for battery size I take my total daily usage and multiply it by the number of days of my "average" trip. that way if I am camping and something breaks in the solar I don't have to go home early, and the other side is if I have a few very bad solar days (raining and overcast) as soon as a sunny day comes I make up about 2 or 3 days capacity every day. this is pretty easy for me to do as opposed to someone who has to run AC as I have only had 1 day in the last 40 years of camping I wish I could run an AC with no hookups.
