On 12/15/20 6:21 PM, (-Phil-) via EV wrote:
Tesla does this on newer S/X. There is a small always-on DC-DC that powers
the telematics and keeps it from deep-cycling the 12v AGM.
I was unaware of that; thanks for the information!
I'll offer a few disjointed EV 12v comments here. Many, I've previously
posted.
My 2013 Tesla was going through about one 12v every year. I believe it
took about four for it go get out of warranty. At that time, I bought a
lithium. I was quite disappointed that Tesla refused to install a
proper battery. Especially since early Ss were a REAL pita to install;
about half a day job. I eventually got it installed and have had no 12v
trouble in the ~3 years since.
Starting with the 2013 Tesla, I started installing SB50 cables going to
the 12v for two purposes. To be able to easily hook up a spare battery
and therefore reduce the risk of getting stranded. Also, to be able to
tap 12v power/energy from the EVs for other purposes.
I have two 2014 imievs, each with SB50 cables. One of those imievs has
had a 12v battery failure. That would be at age about 4-5. Instead of
fixing it right by spending ~$200 on a small odd size AGM, I elected to
put a small lithium in the passenger foot well; the imiev 12v batteries
are also very tedious to change. I now have a Model 3 with two 12v SB50
connections. It turned out that the car would get confused if much
power was drawn from the 12v battery connection. It also turned out
that there is a connection point below the rear passenger seat that can
supply 1kw or maybe 2kw without the car complaining.
All my cars can be used to supplement my single battery PowerWall. That
can be needed to avoid using grid power on hot nights with air
conditioning running. I found no good reliable efficient 12vdc-> 240vac
gridtie inverters. They would work but not supply expected power and
that inefficiently. It turned out that 36v batteries would work very
well to power regular 60 cell panel microinverters. Either one or two
of those inverters gets me through hot nights. Supplementing with
either ~200 or ~400 watts. Though I COULD run quite a few more than two
from the battery bank. Either one or two is sufficient for my purpose.
I haven't experimented with 12v EV power in a long while.
My main 36v batteries are lipos out of hoverboards. I also use those in
golf carts. I keep many, including those in two golf carts in one big
bank all paralleled together. MANY SB50 connectors.
For several years, I've been using small (30ah, I think) Valence
batteries. One is in the above mentioned imiev that has a bad but still
in place AGM. I recently bought six larger (130ah advertised) 12v
Valence batteries. There have been two ebay sellers selling those that
have come out of Smith trucks. I bought mine out of Florida; near
Clunn's place. Cost about $400-$500. All mine tested above 100ah but
none near 130ah. I tried cell balancing on a couple by holding voltage
about 14.5 for about 24 hours. One showed a few ah benefit. Three of
those ~100ah batteries are in series and in parallel with my big 36v
bank. Thus, increasing the energy available to supplement the PowerWall
and also to charge golf carts. I'll soon add the other three 100ah
Valences if no other needs develop. The big Valences could make very
nice RV house batteries. I figure two should run a 12vdc refrigerator
off line for a week or so. I think I decided two 6v flooded lead golf
cart batteries would run a refrigerator for only about a day. Also, a
couple of the big Valences should have no trouble running a 1kw
microwave through a 2kw 12vdc->120vac inverter.
I charge my big 36v bank with a little QuickCharge 9amp lead charger
that is configured to do only a maintenance charge, no more than 41 or
42 volts. That works for both the lipo hoverboard batteries and the LFP
Valences. I have the QuickCharge on a timer so that it charges only
when I likely have an abundance of PV power. Same for a 48v lawn mower
so that I do not use the PW at night to do not critical charging. I
think my big 36v bank is about 20kwh, bigger than the PW.
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