Originally Posted by ShuttlePilot
I live at 6200' and am often higher than that. I follow you on the altitude is a factor as we battle reduced radiator, intercooler, oil cooler performance at altitude a lot. However on this I don't think the difference would be noticeable outside of controlled conditions. For reference, if it is cold in the van, below 40*F, the unit will maintain a heat sink temp of around 170*F and not derate to 30amps. Anything above that and it will reach the 185 and start to cycle, frequency dependent of ambient temps.
Here are my thoughts. I'm not complaining. The little unit dose the job, and even though I have criticisms for improvement, it checks most of the boxes of my wants in this project. I haven't been able to compare my unit to another to see if there is a difference. Some back of the envelope math has me thinking the unit is 75% efficient. Not thermally limited performance is a steady 60 amps in 45 amps out. I'm thinking it needs to dissipate around 250 watts from the heat sinks with fans. Based on the size of the heat sinks with 40mm fans trying to dissipate 250 watts seems like it's asking a lot.
I don't remember if I read that current is limited at 185*F or I just observed it from the remote panel. I might of just accepted it as you say 185 is pretty common. It doesn't seem to stress with this duty cycle, and may be intended to run as such, but I would prefer it have more of the full throttle is 80% of it's thermal capacity approach. It should also be noted for anyone purchasing that this is not a 60 amp out to your battery unit, it consumes 60 from the source and delivers, when full capacity, 45 amps out to the charged battery. So really the delivered current capacity, at max heat sink temps, is a duty cycle between 45Amps and 30Amps. When doing the math that isn't all that much lost watt hours of charge as long as the duty cycle isn't to long. Note, the unit can be set to the 30amp output continuously which I have observed eliminates all heat issues and is capable of 100% duty cycle at 30Amps output.
Anyway, I feel I have hijacked Captain K's post. If this is a conversation we would like to continue I'll start a thread on my build and we can get as deep as we want over there.
This could be of interest to those who are looking to convert. We can move this to another thread, but after frying 2 of my diodes in Baja hood up airing up a couple of vehicles, and rebuilding w/200a diodes, there is a sensitivity to thermal conditions. Alternator was a high output Ford (130a?). I seem to remember the compressor can draw >60a. Victron has an interesting video on alternator heat
and at 1500rpm and 65a (at 3min) fried a "standard" alternator that survived at 3000rpm. They compare to a regulated Balmar. Point is, high current really creates heat, not just in the DC-DC converter. Sterling clearly states installation must be in an open air environment. Curious how you hot rod/cooled your Sterling. Apologies if this is a derail, but Sterling offers one of the highest output DC to DC converters, Victron, Renogy, and others are a bit lower ~30a...As an aside, the BIM has 15/35 a duty cycle, allowing full current when on, and at idle it didn't look like it took 15min to get to smoke. Driving is thermally kinder to all alternators. Also the BIM won't fully charge the LiFePO4 batts with a stock regulator, DC-DC buck will....The BIM costs less, but has drawbacks. Solar would help with a full charge.