Im not the most electrically inclined, my knowledge of circuts goes as far as Minecraft redstone, so I'm just gonna say what I want as inputs and outputs

It's an on/off switch

When powered on: result is power to A
A is powered until switch is turned off

When powered on, powered off, then powered on again: result is power to B.
B is powered until switch is turned off

I'll be honest, someone mightve answered this question already, but I just haven't used the right search terms. Hopefully this post makes it easier for someone to find their way to the more high-level post talking about the same thing.

This is for a 12v, car battery application.

Thats all you guys really need to know, I think, but if you want to know what the full application is, it's for an EV-converted VW Bus, where we are integrating solar power into it. We can't power the main battery directly, so we will be running solar power to an auxiliary battery, which will be charging it from an inverter with your run of the mill wall outlet plug-in charger.

Where this circut comes in, is I have a classic style pull switch in the dash, and want to set that to charge the vehicle with solar when I park, but when it's been running hot, like on the freeway, the vehicle won't accept charge until it cools down, going so far as to not accept it again until the plug is disconnected and reconnected. so ideally, this singular "solar switch" has two modes:

1. When I haven't driven, or haven't driven far, I just pull the switch, and it activates the charger. When it's time to drive, I push the switch in and it shuts off.

2. When I've been going long distances on the freeway, I pull the switch, push it in, then pull the switch, and walk away, because I can have a timer relay that activates the charger in 30 minutes, so I don't recieve a fault, and stop charging. When I return after a long day at work, I push the switch in and drive away, with the battery charged over time.

 

Thanks for explaining the problem you are actually trying to solve -- there are almost always devils in the details when it comes to helping you find an acceptable solution.

In your current setup, what prevents the battery from being overcharged? Does it sense full charge and stop charging, or are you just float charging the battery, or something else? What kind of batteries are we talking about?

Let's consider the ultra-low-tech approach, first. Would it be acceptable to just always have the charging circuit activate after 30 minutes? If not, why not? Perhaps overcoming that issue would be easier/better than the one you currently have in mind.

At the other end of the spectrum is considering whether it might make sense to try to detect if the battery is ready to accept a charge. When you say that something has to be unplugged and reconnected, what has to be unplugged? The charger from the battery being charged? The charger from the inverter output? What is the symptom that tells you that the battery isn't accepting the charge? High current draw (causing an auto-reset breaker in the charger to trip, perhaps?).

If this even can be detected, then perhaps the problem can be solved from a different angle. Simply have your charging circuit attempt to charge the battery and, if it won't accept charge, have it wait a few minutes and try again and keep doing this until it stops rejecting the charge.

If you decide that you really need manual control over things, it might be worth considering what the default behavior should be. You describe it with the charge-now mode being the default. What happens if you've driven a bit further than you thought and so you just pull the switch, thinking the battery is cool enough to accept the charge, but it's not and you've walked away but nothing is getting charged. The alternative is to have the charge-later option be the default so that if you choose to override it and use the charge-now mode, you have to make that decision consciously and know that you need to verify that it is actually charging before you walk away.

Once you've decided that, then there's the question of what technologies are acceptable. For most things like this, a tiny, cheap microcontroller is the way to go, but you have to have the knowledge and ability to develop and program the part. You also have to consider the impact of wanting it to work in an automotive environment, which are generally not too friendly to electronics. An alternative is to use something like relay-based logic.

 

Thanks for explaining the problem you are actually trying to solve -- there are almost always devils in the details when it comes to helping you find an acceptable solution.

In your current setup, what prevents the battery from being overcharged? Does it sense full charge and stop charging, or are you just float charging the battery, or something else? What kind of batteries are we talking about?

Let's consider the ultra-low-tech approach, first. Would it be acceptable to just always have the charging circuit activate after 30 minutes? If not, why not? Perhaps overcoming that issue would be easier/better than the one you currently have in mind.

At the other end of the spectrum is considering whether it might make sense to try to detect if the battery is ready to accept a charge. When you say that something has to be unplugged and reconnected, what has to be unplugged? The charger from the battery being charged? The charger from the inverter output? What is the symptom that tells you that the battery isn't accepting the charge? High current draw (causing an auto-reset breaker in the charger to trip, perhaps?).

If this even can be detected, then perhaps the problem can be solved from a different angle. Simply have your charging circuit attempt to charge the battery and, if it won't accept charge, have it wait a few minutes and try again and keep doing this until it stops rejecting the charge.

If you decide that you really need manual control over things, it might be worth considering what the default behavior should be. You describe it with the charge-now mode being the default. What happens if you've driven a bit further than you thought and so you just pull the switch, thinking the battery is cool enough to accept the charge, but it's not and you've walked away but nothing is getting charged. The alternative is to have the charge-later option be the default so that if you choose to override it and use the charge-now mode, you have to make that decision consciously and know that you need to verify that it is actually charging before you walk away.

Once you've decided that, then there's the question of what technologies are acceptable. For most things like this, a tiny, cheap microcontroller is the way to go, but you have to have the knowledge and ability to develop and program the part. You also have to consider the impact of wanting it to work in an automotive environment, which are generally not too friendly to electronics. An alternative is to use something like relay-based logic.

So, to answer your first paragraph, I'll break it down in where the power is going. From the solar panels, it'll go to a, say 12-48v battery. This battery will use an inverter and then EV charger to charge the EV battery, which is 150v.

For the second paragraph, I'd love it if I could do that... OK as I was about to type a "but" to that I realize that that is an amazing plan. I thought I thought it through, but I guess writing it down jogs common sense into the equation or something. Just depowering and then repowering the connection between the deconstructed charger will achieve the same effect as unplugging and plugging in the car again, so how would I go about this? I can figure out how to make the charger for the EV battery disconnect with the power of a signal wire, but how do I implement a 30-minute power then maybe like 10-second depower on a signal wire? Just two timer relays?

 

You need a relay to activate for 30 minutes then deactivate for 10 seconds and repeat until the signal wire is disconnected?

 

So, to answer your first paragraph, I'll break it down in where the power is going. From the solar panels, it'll go to a, say 12-48v battery. This battery will use an inverter and then EV charger to charge the EV battery, which is 150v.

For the second paragraph, I'd love it if I could do that... OK as I was about to type a "but" to that I realize that that is an amazing plan. I thought I thought it through, but I guess writing it down jogs common sense into the equation or something. Just depowering and then repowering the connection between the deconstructed charger will achieve the same effect as unplugging and plugging in the car again, so how would I go about this? I can figure out how to make the charger for the EV battery disconnect with the power of a signal wire, but how do I implement a 30-minute power then maybe like 10-second depower on a signal wire? Just two timer relays?

There are actually a number of options to consider spanning a range of complexity.

One method would be to not even try to detect if the battery is charging and to always have it run on a cycle where it powers up the charger for X minutes and then disconnects it for Y seconds and then repeats. Set Y to be comfortably above the minimum necessary for the charger to reset (you've indicated ten seconds, so let's use that for discussion's sake). The smaller you make X, the quicker the charging process can start. If it were set at just ninety seconds, that would mean that once the battery was cool enough to start accepting a charge that it would be charging 90% of the time. If it were set for 16.5 minutes, then the charging duty cycle would be 99%.

 

This is an interesting set of conditions, which I understand is that one battery package will not accept a charge when it is hot. I get that from the statement in post #1:" when it's been running hot, like on the freeway, the vehicle won't accept charge until it cools down, going so far as to not accept it again until the plug is disconnected and reconnected." So once the battery temperature falls below some value (Not Hot), charging can begin
My cheap trick suggestion is a normally closed, open when "hot" thermostat installed at the battery pack, linked to the charging system controls, that will inhibit the charge system when the battery is "hot", and allow charging when the battery is "NOT HOT".
I recommend, in addition, some sort of indicator to let you know that the batteryis not being charged because it is hot.
The two challenges will be finding the location to correctly sense that the battery is "hot"' and locating a suitable thermostat that opens at the hot temperature and switches back closed at a suitable "NOT HOT" temperature.