I have some latching relays as well. But the ones I have are not sealed or waterproof so I didn't want to mount them in the engine compartment. I just happened to have the 80 amp sealed relay so I used it. The one I am using pulls maybe 30 mA. I have it set for normally closed in case it fails or opens the alt is back on line and when I do turn it on it is powered from the "extra" battery anyway.
I know one amp (and that's probably only in bright sun, less is likely on cloudy days) isn't all the power you will need for running a car (even with the accessories off). However, it should easily be enough to keep a car battery "topped off" while the car isn't running (thereby hopefully lowering the increased alternator load to "charge the battery" when first starting up). And I figure (up to) one amp might also be enough to "help out" while driving the car in the day (possibly raising the gas mileage a small amount when driving during the day).
And the thing I really like about that array (other than the reasonable price, including the "free shipping"), is that it's dimensions almost (but not quite) completely match the top dimensions of my (internal) "trunk cover" on my CRX! This means I should be able to mount that array in the back of the INSIDE of my car, on top of the "trunk cover", but underneath the back hatch glass. So (if I got this array for my CRX), there would be absolutely no loss of aerodynamics by leaving the array always in place (as the array would be in the car all the time). So the only FE loss (from having this array) should be the weight of the array (which is under 15 lbs)!
But my big question is, would the (up to 1 amp of) power from the solar array, actually lower the current generated from the alternator when the car is in use (or would that solar power go "wasted", and the alternator still generate the full current for the car)? I know the array could keep the battery "topped off" when the car is stopped, but what about when running? Is there an easy/cheap way to make sure that the power from the solar array is used BEFORE the power from the alternator (thereby lowering the overall load on the alternator, when driving down the road in the sun)?
I guess I'm kinda looking for some opinions, before I rush out and spend $100 on this solar array. I know $100 isn't a huge amount of money, but it's still a real chunk of change. OTOH if this array really will both keep my car battery "topped off" at all times, and lower the power needs from the alternator while driving during the day, it's likely going to be a "win" (even if not enough power to totally eliminate the alternator, maybe enough to "make a difference).
Since I don't like the ides of running a total loss electrical system. I see potential for the solar panels shown on Amazon if you combined the charge controllers sold from the same company with a custom relay/contactor to determine when the alternator is used. This way, when the electrical loads are low, the solar panels can help reduce the alternator's use, and at higher loads, no light (at night) the alternator can do its job at keeping the battery charged.
The problem is with solar they are rated at ideal sun angle at solar noon. Once you get that inside the car you will loose 10-30% right off the bat for going through another layer of glass (likely UV coated). Then top that off with being shaded or tilted at the wrong angle and you would be lucky to get 50% of rated power even with full sun not to mention cloudy or shaded conditions.
There is something to "topping" off a battery before driving though. I do this all the time from my home solar array, which I also use to charge my second battery. Basically I use two older marine batteries and swap them out when I get home and put the used one to charge on from the solar array.
In case anyone missed it I use one of the old marine batteries to feed a 1200w Trace inverter, which in turn feeds an Iota DLS 55 amp charger that is connected to the starting battery with the alternator wire disconnected. So my inverter / charger acts as the alternator charging the main battery. Again my problem is I have glow plugs that warm up the coolant pulling 60 amps until I hit about 110-120F on coolant temp. In winter that is 5-6 miles, right now about 3 miles and in the heat of summer that is a mile or so.
Anyone try using HT Peltier coolers on their exhaust?
The problem with these is three: 1) they have limited efficiency, 2) like solar, they get to cost a lot once you have enough of them to be useful, and 3) they don't actually work on heat, they work on heat differential. That means you need to have enough 'hot' surface area to hold the requisite number of the devices and some way to carry that heat away (heatsinks, etc.) to create a temperature gradient on the other side of each device.
I've done the numbers and besides the cost, it's not clear to me that while the exhaust temperatures are high enough, exhaust probably won't give you enough overall heat to make it worthwhile. Engine coolant might have enough heat, but the temps are probably too low. YMMV.
Reality is merely an illusion, albeit a very persistent one. - Albert Einstein