Second 12v camping battery and charging circuit

no idea, but like tour hutzbah. all the best!

 

I think the solar charger is an interesting idea, at least as part of a complete system.

If it were me (and it may well be, shortly) I would use a commercial RV 2nd battery isolator, so the second battery would charge as part of the Prius electrical system while the car was running, and use the solar charger only while the Prius was off. I'd probably put a physical switch or two in there also, just to be on the safe side.

Battery isolators:
140 Amp Dual Battery Isolator by KeyLine Chargers (Iso-Pro140 Pro Dual Battery Kit)

WirthCo 20092 Battery Doctor 125 Amp/150 Amp Battery Isolator

Voltage Sensitive Relay Dual Sense 12V 140A (Smart Battery Isolator)

 

And it will arrive in only 20-40 days!

 

Using a VSR seemed like the ideal solution to having a second battery in the Prius. Since I'd be using it only occasionally, I figured that it wouldn't need more than a trickle charge every now and then. I didn't think it would stress the system any, especially since I was planning on a much smaller battery. The other option I was thinking of was to keep the second battery completely isolated manually from the Prius electrical system (except for emergencies if the first 12v battery ran down) and using a solar charger like this one from PulseTech.

Since I have the solar option, I was also considering hooking the second battery up to the built-in solar panel, but I chickened out. The risk of damaging something expensive to fix was just too high.

 

Laird, you had said "... I understand that I have nearly unlimited power while the car is in READY but then it's unlocked and occasionally running the ICE and confusing the other campers."

But you can leave the car running and lock it up.

The easy way to do this is by getting a normal physical key made from your tiny skinny key that is in your Prius fob. The normal key will open the door, but obviously not start the car. This is better than having to slide out the skinny key from the Prius fob.

When you lock the car and leave it running just put up a sign that says something like, "car is in generator mode and may occasionally turn on and off".

 

You are going to need a couple of batteries to get your 50 Ah. You could probably fit them behind the passenger front seat on the floorboards. Solar isn't going to do you much good, unless you have a pretty large footprint of solar panels. Your best bet would be to isolate the camping batteries with an appropriate battery isolator (maybe $100) and run big wire (2/0) between the aux battery and the camping batteries. Put in an easily accessible emergency switch and big fuse, as well. Charge the battery using shore power before you go, and top off with the ICE, as needed.

 

Question. How do you lock the car if you are camping in your Prius? When I was at a Rest Area on a long drive, I tried to sleep in the car with it running. My FOB wouldn't lock the door from inside. I had to physically push the door lock button, then crawl between the front seats to get into the hatch area where my air mattress was. Very hard to do.

 

Has to be from inside with the door button, or from outside by turning the mechanical key in the lock.

-Chap

 

That's how I do it. Get in the back, and reach forward between the seats and push the lock.
I am looking at how to install a separate remote to lock the doors when the car is in Ready

 

You seem to know what your doing but mucking around with the 12 volt battery system in a G2 is scary. I would just hook a 1000 watt inverter directly to the 12 volt battery. You blow that hardwired in that main 100 amp fuse in the boonies and your screwed.

Bottom line is your going to stress the hybrid battery out a little. I would be worried about that only because if you have an original hybrid battery in the car its really old and pretty tired. If it was a pretty new G2 I would say go for it but your car is very very old.

My first thought is how far would a tow have to tow you to get back to a toyota dealer?

 

I'd like to have an additional battery to run camping equipment while the car is off. The problem is that if I run that battery completely down, it will draw some large amount of current while initially recharging. Is there some sort of circuit that would limit the recharge current to 10 amp (like you can get out of the power outlet)? What I'd like is a battery isolator with a current limiter.

 

One thing I can think of to be perfectly safe and not stress the system is to charge the second battery only with a limited amperage battery charger, like the 1.5 Amp BatteryMINDer 1510. You'd have to run it from an inverter, though. I'm pretty sure that this would solve the isolation problem, but it seems inefficient.

An other option is to use a 12v DC to 12vDC charger, like the Tecmate Optimate TM-500. I don't know enough about these to know if there would be any isolation issues, though.

A third option is to use a marine solution, rather than a RV solution. Using the Add-a-Battery kit from Blue Sea, for example, which combines an ACR (Automatic Charging Relay) plus a dual-circuit battery switch might work. It's expensive, though.

I had two goals for this for my setup - one was to be able to run a computer and/or tablet while the car was off. The second was to have a built-in emergency back-up 12v battery that could easily start the car in case the primary 12v was accidently run down, preferably without having to connect any cables. The third parameter I think I didn't pay enough attention to was to avoid putting any stress on the cars electrical system.

I didn't think it would be all that expensive or complicated to do this, but apparently I'm wrong. I also didn't realize the electrical system on the Prius was so very fragile. It sounds like using an external solar panel to charge a small 12v battery for powering the computer system, and having an emergency-only connection to the primary 12v battery kept completely separate by a physical switch is the only safe way to run a rig like this. On the other hand, operating the Prius without an emergency backup battery now seems extremely reckless.

 

Those devices are readily available. They are called voltage sensing relays. Your "camping battery" will not draw down the "car" auxiliary battery. Once the voltage drops, the camping battery is disconnected.

• Here is one: Click Here!
• Here is another one: Click Here!

Since I live and work in SoCal, I have often thought of putting flexible solar panels on the car to keep a camping battery charged, but the design effort doesn't seem worth it. Right now I have a 2000-watt inverter under the front seat connected to the car auxiliary battery using 2/0 AWG stranded jumper cable wires. I carry a hotel-style Kerig (very low wattage) and an Igloo counter top ice maker for convenience. Additionally, I can run my Instant Pot Mini for full meals.

I have done some ladder logic switching that keeps the inverter off unless I engage a switch mounted under the dash, with a very bright indicator LED, and also will not allow the inverter to be powered if the car is off. To me, this is the best of all worlds.

Coffee service is nearly instant, in an hour I can have a pound of ice for cold drinks and the Instant Pot is great for full meals.

The ice maker is also modified so that it can dump the ice into an ice chest by changing out the ice basket with a special ramp that funnels the ice into a 1.5-inch tube that drops it into the ice chest through a trap door. The "melt" in the ice chest is pumped back to the ice maker for sustainability when it is on, with the water level controlled by a sensor. Some day I will post pictures of that setup.

Keeping the inverter inside the car is pretty critical to prevent overheating if you are using over about 600 watts at once, but the inverter will also.

 

The main car battery is protected. But when a totally discharged aux battery is reconnected, it's going to draw major current, certainly more than the power outlet can handle. Rather than running #2 cable direct to the main battery, I'd like some sort of current limiter to allow use of the power outlet.

 

The power outlet wiring is super small. Be careful. When I started poking around, I could not believe the size of that wire (maybe 22 gauge). Discharge from your "camping battery" would need to be be controlled to prevent full discharge, again with a voltage sensing device. I have a little 300 watt purse sine wave inverter that I plug into the power port for tiny loads, like my laptop and portable printer.

There are tons of interesting videos on YouTube about the different kinds of setups that can be done. One of the major disadvantages to the Prius is that there is precious little space to organize the components.

Also, if you keep the car in Ready, you are free to use the AC and the inverter without consequence, since the ICE will spring into action and keep the traction battery charged, which in turn will charge the car auxiliary battery and your camping battery.

 

Interesting device. This one is limited to 2.7 amp input, but it might handle the situation of bringing the aux battery up to a condition where it could be directly connected to a 10 amp supply.