DIY "Mild" Plug-in Prius Project: Grid-powering the 12v side w/ deep cycle batteries

[unixrocks]

Found the converter - or rather how to disable it.

[2009Prius]

Originally Posted by unixrocks

Paid closer attention this time to the voltages - the converter does indeed keep the voltages above 13V and up to (at least so far) 14.8V - it appears to depend on the SOC of the 12V battery ...

This is strange. The ScanGauge shows very stable 14.0 ~ 14.1V while driving around.

Originally Posted by unixrocks

Found the converter - or rather how to disable it.

More details to share?

[orange4boy]

All I did with the 14 v hillbilly battery was connect it to the 12V battery leads. Done! The DC-DC is under 0 load until the battery drops to ~13.5. Then it slowly starts sharing the load with the battery so you can never drain it too far. With an anderson connector to avoid reverse polarity accidents, It's totally idiot proof and requires no modifications.

[unixrocks]

Originally Posted by orange4boy

All I did with the 14 v hillbilly battery was connect it to the 12V battery leads. Done! The DC-DC is under 0 load until the battery drops to ~13.5. Then it slowly starts sharing the load with the battery so you can never drain it too far. With an anderson connector to avoid reverse polarity accidents, It's totally idiot proof and requires no modifications.

Final thing I am trying to figure out now that I have a 14v battery is whether to run the 12V battery inline with it? Reason being it would be a lot easier to put a quick disconnect on the 14V battery for recharging at night and have the 12V keep the ECU settings intact - honestly I can't see a downside to running the two batts together because the 12V is just going to sit there taking a low current charge from the 14v but maybe I am missing something?

[unixrocks]

Originally Posted by unixrocks

Final thing I am trying to figure out now that I have a 14v battery is whether to run the 12V battery inline with it? Reason being it would be a lot easier to put a quick disconnect on the 14V battery for recharging at night and have the 12V keep the ECU settings intact - honestly I can't see a downside to running the two batts together because the 12V is just going to sit there taking a low current charge from the 14v but maybe I am missing something?

Uhh ok got my answer today when I tried it....the 12V battery starts charging off the 14V battery but without anything to stop it from charging it just drains the 14V battery while gassing off the excess power.

Not a good idea for either battery.

So....guess I will just use my lawnmower SLA battery to keep the ECU alive while I charge at night - test and see if the mileage improvement is worth the hassle of a cleaner solution.

[unixrocks]

Originally Posted by 2009Prius

This is strange. The ScanGauge shows very stable 14.0 ~ 14.1V while driving around.



More details to share?

Sorry - missed this one - you can disable the converter via the fusebox - the 100A fuse is it.

the 14.0-14.1V on the scangauge is surprising - my stock battery is good and I see wild fluctuations in voltage - I would guess that I see fluctuations because as the 12V is topped off it is detected by the system and the system stops sending the 14V to the battery to charge it - I cant yet account for the 14.8V I see sometimes - I do have a stock 2008 prius without navigation, bluetooth etc.

If your constantly seeing 14V then I would guess your 12V battery is not keeping up with the demand - what year is your prius and whats it got for electronics?

Edit: Ok missed the obvious yours is a 2009 prius - I dont understand why the 14V is constant - I would think the converter would come on and off as needed but maybe its by design in the 2009 to stay on to ensure the battery is at full charge?


I will post more details as I get some real world results back from this setup.

Further Edit: I have been sidetracked from this because I have been pulling apart the front cowling and all the vents and blower to try and find the source of the "mouse urine" smell with no success at all. managed to track it down to just the internal vents but still nothing found to explain it. =-P

[2009Prius]

Originally Posted by unixrocks

Sorry - missed this one - you can disable the converter via the fusebox - the 100A fuse is it.

the 14.0-14.1V on the scangauge is surprising - my stock battery is good and I see wild fluctuations in voltage - I would guess that I see fluctuations because as the 12V is topped off it is detected by the system and the system stops sending the 14V to the battery to charge it - I cant yet account for the 14.8V I see sometimes - I do have a stock 2008 prius without navigation, bluetooth etc.

If your constantly seeing 14V then I would guess your 12V battery is not keeping up with the demand - what year is your prius and whats it got for electronics?

Edit: Ok missed the obvious yours is a 2009 prius - I dont understand why the 14V is constant - I would think the converter would come on and off as needed but maybe its by design in the 2009 to stay on to ensure the battery is at full charge?


I will post more details as I get some real world results back from this setup.

Further Edit: I have been sidetracked from this because I have been pulling apart the front cowling and all the vents and blower to try and find the source of the "mouse urine" smell with no success at all. managed to track it down to just the internal vents but still nothing found to explain it. =-P

Thanks for the reply. Yes mine is 2009. I do have a slight suspicion on the health of the 12 V battery. Here is a graph of measurements I have done so far: (mostly with ScanGauge and earlier few with diagnostic screen)


I don't have any significant extra electronics - just the ScanGauge, GPS, and a pair of homemade LED DRLs (drawing less than 1/2 amp total I think). The battery seems on the weak side but not dead yet so I don't think the dealer would replace it for free.

[2009Prius]

This must be obvious to the experts but I am not afraid of asking stupid questions. Why not just remove the 12V battery all together and install the deep cycle 14V battery in its place? Then all is left to do is to come up with a charger to charge the 14V at home. No relays, no smart switches. What's wrong with this idea?

[unixrocks]

Originally Posted by 2009Prius

This must be obvious to the experts but I am not afraid of asking stupid questions. Why not just remove the 12V battery all together and install the deep cycle 14V battery in its place? Then all is left to do is to come up with a charger to charge the 14V at home. No relays, no smart switches. What's wrong with this idea?

Not stupid at all - thats what I am testing out now - the problem is the expense and whether or not it is worth it.

There are a few big problems:

1. The battery is huge compared to the original and wont fit into the battery compartment.
2. The charger for it is not yet available. (people using this battery in standard ICE cars are using a voltage regulator on their alternator to charge it)
3. 14V from the converter will not charge it - you need 16V
4. You need to disconnect the battery while charging unless you want to risk blowing some electronics in the prius
5. There is still some question as to what the real world impact is - I cant really assess how much of a boost the battery is giving me until I get the charger (due out in the next few weeks)

All of the problems are resolvable if the battery is worth the effort - if I cant get more than a few mpgs out of it then I suspect I will go back to the stock battery since it is far easier.

Edit: BTW Orange4boy already proved this has great potential with his hillbilly battery - and I was wrong on disabling the converter - I thought I had disabled it but turns out it was the battery being a decent SOC preventing it from coming on - so Orange4boy whats the secret to disabling the downconverter for testing this fully?

[Daox]

What about using a 14.4V battery tool charger? They're usually setup to charge Ni-Cd, not sure how much that differs from the lead charging cycle. I'm also unsure if they'd be able to provide sufficient amperage to charge overnight.