I’ve noted before that when I stealth camp in cities my charging percentage from alternator increases from ~5% to ~10% of total production. The increase isn’t needed (solar could cover it) but the alt gets a chance to play.
Since I am moving at least twice a day (3x with PF showers) I’ve had an opportunity to record a higher frequency of engine starts and LFP bank acceptance. The setup:
- 180A alternator that typically runs at 14.2v
- Battery Doctor VSR setup left over from my previous FLA bank
- 150Ah 12v LFP bank
- SoC and voltage measurements below taken from BMS before engine start
- current measurements taken from BMS though it agrees with shunted battery monitor. (I can see the BMS via bluetooth from the driver’s seat but I can’t see the monitor)
- solar contribution and loads ranged widely, leading to variance.
Over the last ~20 runs, the average state of charge was 72%, bank voltage 13.20v, charge acceptance 0.183C (27.39A)
SoC Vbatt C A
60 13.07 0.245 36.75
72 13.15 0.130 19.50
69 13.13 0.120 18.00
27 12.95 0.270 40.50
80 13.29 0.150 22.50
80 13.27 0.240 36.00
81 13.30 0.170 25.50
77 13.22 0.165 24.75
39 13.03 0.260 39.00
95 13.30 0.115 17.25
48 13.06 0.235 35.25
86 13.56 0.120 18.00
90 13.25 0.220 33.00
90 13.26 0.165 24.75
62 13.08 0.240 36.00
92 13.27 0.084 12.60
92 13.27 0.090 13.50
58 13.07 0.235 35.25
89 13.26 0.140 21.00
84 13.26 0.215 32.25
49 13.07 0.225 33.75
Given average charge acceptance of 27.39A, the obvious comparison here is to a 30A DC-DC like the Orion-TR. The DC-DC would have a much more stable charge rate, typically ~30A except late in the charging process when acceptance at Vabs tapers.
I typically only relocate every few days but when I do I’m usually driving for at least 3-4 hours. My 30 amp Orion plus my solar panels is usually enough to get my 272aH battery to full. I do wish I had gone with a larger DC-DC charger because I occasionally have to idle the engine to charge the battery when the weather is cloudy even if I’m not driving anywhere. A 60 amp charger would reduce the time I’d need to idle in order to get a decent charge.
One minor annoyance is that the Orion doesn’t charge my lifepo4 to 100% on its own. I don’t think the voltage knob goes high enough to hit the top voltage that my BMS considers 100%. It’s probably only a few amp hours of capacity missing, but it bugs me to drive all night and end up with only 95% charge.
A 60 amp charger would reduce the time I’d need to idle in order to get a decent charge.
I’ve seen Orions paralleled for 60A. Is that an option?
Yes, I would need to run a larger gauge wire but the connection point on the vehicle is capable of 60 amps. I just don’t want to run more wires though because I’m lazy.
