Extra auxilary battery charging...

Seems logical to me, you know of course that the plug does not work the other way, that is, for use as a emergency source. :cheer2: I also keep a sealed, block, gel, alarm battery in that position on trips. edit: on my 2005.

 

I am not a battery expert but connecting to the 12V (which is actually 13.6 or 14.8 depending on bunch of thing) bus without anything regulating/monitoring current to the "other" battery might not a good idea ... on a longer trip you can way overcharge it. The fuse for those outlet is 10A (if I recall correctly) I did manage to blow one with an air-pump. And if I am not mistaken a deeply discharged battery can take a lot of current probably exceeding the 10A ...

Just my 2 cent,

 

Very good point. I think probably the OP is concerned with keeping a healthy emergency battery topped up. But your point is well taken. :cheer2:

 

Thanks....

I agree that it is a good idea to have a backup battery ... but not sure what emergency it is for ????? You got stranded ??? You just keep the car in Ready mode and you can power an inverter about 100W completely safe !!! Just do not put it ACC. If you want more power that is possible but you need to "modify" the system you can look for Prius as a backup generator topic.

If you are concerned that your 12V battery drains .. that is a different issue ... probably your solution a long lasting (low self-discharge battery pack is a better solution) And you probably know when you will leave the car sitting for a while ... I left mine for little over 2 weeks no issues... You could turn off sks (well if it is in a garage) and that should give you a lot longer even a month or more...

If an extra battery should be connected to the 12V thing I would look for some of those solar panel regulator thing ... for drip charging ... but certainly would NOT charge a discharged battery via the prius AUX ports ... (it is probably fine if you connect it to the battery circut ... but leaving it there AFTER the car is off could create a serious issue. The two batteries will not self-discharge the same rate and probably drain one another.....)

If I have a vote I would say this is not as simple as just plug it in !!!

 

I left mine for three months and had no problem, BUT, I took the precaution of charging the HV and the 12V to max and made sure there were no drains.

When the car is OFF there is no current flow either to or from the accessory plug. When the car is ON, either access mode or ready there is no current flow if nothing is plugged in! only if there is some sort of load does current flow occur. Should the emergency battery be 12.8V and the access plug measure at 12.6 there is no current flow

It is a never ending story on the problems that occur with the 12V battery, from 2001 onward. I do not expect the problem to go away. I am actually surprised we have not already had problems........so. maybe Toyota fixed it?......I doubt it. It is a good idea to carry a spare battery. I totally agree with the OP. :cheer2:

 

I am not sure what you are saying in this:

" When the car is ON, either access mode or ready there is no current flow if nothing is plugged in! only if there is some sort of load does current flow occur. Should the emergency battery be 12.8V and the access plug measure at 12.6 there is no current flow"

That is not that simple ... if the car is ON (Ready) the main battery will keep the voltage up at least 13.6 and the current will flow .... if you shirt-circuit, fuse blown that what happens .. If not you will drain the main battery when it turns to low, ICE will kick in ...

BUT THIS IS NOT the case if you only in ACC ... you can actually drain the main battery and ICE will NOT come on. If that happens you probably have a BIG repair issue and car will NO longer turn on .. (that is my understanding not what I witnessed)

 

You know I never thought of it that way, but I think you are absolutely right. Hopefully you will continue to paticipate in Priuschat. Thanks. :cheer2::cheer2::cheer2:

 

A correction: There is always a slight parasitic drain existing