exchange 12 volt battery?

how about a gelcell 12 volt battery, no venting problems, and more AH capacity. So what if the one time cost is slightly high the OEM battery isn't cheap either. Anyhow that's my plan when it comes time. No sign of that time yet, left the Classic for 9 day's hopped in and it fired right up. As the lighter socket is live all the time I had plugged my volt meter in and when it started it said 11.7 volts. So no where dead. Sigh guess I'll have to wait till next year. Or the one after that.

 

diodes are not an option as the voltage drop across them in a charging circuit prevents the battery from ever becoming fully charged. Simplest solution is one of those jump box-booster units. If the battery in the car goes dead just jump it like a normal car.

 

I enquired to this subject about a year ago and Frank ( I believe ) was nice enough to forward a nice schematic. Since I'm no longer into electronics I did not bother. But, did buy a small gel cell ( 7 AMP ) and charge it from time to time thru the socket, on a trip. Did run the car on it alone for about 6 miles for a test. Seem to support the Computer fine. One of the Senior Advisors also warned me that a large current demand could be made and burn up the 7Amp battery as well as some Prius electronics. So...it'sprobably OK as a temp solution.

 

Threre seems to be no way of predicting a failure of the 12V battery while it is in normal operation. With a normal car battery you can usually tell because the starter turns a little slower or the headlights are a bit dim when the engine is off, etc. My guess is when these things go they usually lose all or almost all of their capacity but when fully charged the Voltage is just fine.

I think you could remove it from the car and do a load test on it. All you would need would be a load resistor (even a light bulb would work) and a multimeter. The best setup would be a big rheostat a Voltmeter and an Ampmeter. Discharge it and find out how many Ampere hours it had left in it. Just take it down to 10.5 Volts (1.75 Volts per cell) at it's 8 hour rate and see how long that takes. I think if it got down to 60% or 70% of it's rated capacity it would be time to replace it.

We would need to know how many Ampere hours it is rated at, divide that by 8 and compute what size resistor we would need. Of course to be completely accurate you need to decrease the resistance a little as the Voltage drops but even if you didn't do that you would get a good enough answer.

Anyone see any problems with this?

 

I agree, if it is weak replace it. Does anyone know how old the batteries were that failed? I would think a battery such as this should last for, what? 4 or 5 years? I usually get 5 or 6 out of a good car battery.

 

I just replaced a deep cycle RV battery that had 8 years on it. However being installed on an RV plus located in Sacramento equals long life. I wonder if there is any geographical differetiation between a Prius sold in FL or CA OR Minn. Generally the Specific Gravity of the Electrolyte is different for cold VS hot climates. The warranty varies a lot also. Generally shorter in Northern areas. Any experts know if Toyota considered these things?

 

I'm not sure I totally follow what you are saying. I DID disconnect my 12VDC source and ran the Prius for about 6 miles. I deliberately did not use any accesories, as this was a test to see if the 7 ampere gel cell would support the computer. It worked fine and in an emergency I would have the option of paralleling with the ( questionable ) OEM Battery or hooking it up separately. The latter would be more sensible as a severe short within the OEM Bat could cause many problems.

 

By "disconnect my 12VDC source", do you mean you removed the battery
entirely [leaving the whole system to run on the inverter], or
disconnect the charging inverter from the 12V system now powered
by a 7AH gel-cell, or what? Nothing you've said so far is allowing
me to determine exactly what you did during this "test".
.
_H*

 

I paralleled my 7 Amp Bat to the two OEM Bat connections, then lifted the whole positive wiring bundle so that I would not have to reset everything. Also made sure that wire bundle was insulated and isolated from positive post. Then I took the car out for a test drive. Worked fine. If I was to totally replace the OEM Bat, at my expense, some time in the future, I would consider a Gel with about a 25Ampere/Hour Capacity. If it physically fits. Did I answer your question?

 

I have something along these lines installed in a 2001 Prius. MC switch on dash closes a relay in the trunk to bridge the blocking diode on 7 AH gel cell. Helper-starter.

There are options to replace the NHW11 battery with more economical (but still vented) alternatives. My opinion is that an unvented PbA battery would work fine except in the rare/never circumstance that the Prius 12v bus provided a much higher voltage. That could lead to undesired accumulations of hydrogen gas.

Not sure how different the NHW20 battery is, or if anyone has identified a vented alternative.

 

I'm adding an Optima battery as an aux 12 volt. It is big, and i will have to make mods to fit it.
But it is the size I need, and it is vented. Check out Optima Marine batteries. I think there is only one that is vented. Forgot the model I got.

Another option I've seen on the web is to get a battery box that is vented.

 

That was a potentially dangerous experiment. The various computers are controlling everything millisecond to millisecond. If your substitute batttery or its connection had failed while you were moving you could have destroyed your transmission. You would have reacted a thousand milliseconds too late to do anything about it.

If there is any question about the OEM battery it should simply be replaced, not supplemented.

 

I lean towards Richard's position here. In fact previously (in some forum) I suggested to one who wanted to drive his Prius using a 12 v gel cell, that the slide-on connectors to the battery lugs might not be adequately reliable. The problem, it seems to me, is that we don't know if the Prius' 12 v downconverter will function happily if the 12 v battery connection fails. I'm not gonna test this.

 

One would hope the Toyota engineers would design it well enough so it would function without the battery hanging off the end of it. But I don't want to test it with my car either! Now maybe if we rented one? no just joking.

Actually I think if this battery were relocated to a place where there was adequite ventilation the problem would be solved. You could replace it with a lawn mower battery from Wal Mart for 25 or 30 dollars which would last longer and perform better. I've looked and don't have any good ideas of where to put one though.