doubled ev range less then $2500 no car modifications

any problem with a rear end collision?

 

That's basically the PIS kit isn't it? The main problem is it takes a $1500 controller to make it work. That's what the dc:dc converter or ac inverter is basically getting you out of.

Rob

 

That would be the other big benefit of something like the Enginer porta-power solution to this same approach IMHO.

 

i may have missed this, how long does it take to charge on solar?

 

FYI here is the datasheet on the AGM used.
https://s3.amazonaws.com/ecodirect_docs/MK/8A8DLTP-DEKA.pdf

The battery is rated at 245Ah for c/20. That would be at 12.25A discharge for 20 hours. At 360 A (120A per battery), the effective capacity will be much lower. They don't specify capacity at higher currents, which can be a bad sign in terms of its Peukert exponent. Assuming its at least as good as the one I posted earlier, at 120A the effective capacity would be 139Ah. So for 3 in parallel that's 417Ah, or about 5kWh effective capacity. It may be a little better than that if 360A is a peak value rather than typical for the battery current.

Assuming the inverter is 90% efficient, you'll need about 3.56 kWh to recharge the PiP from empty. So that would put you at about 71% Depth of discharge (DOD) on the AGM pack. Using the cycle life chart in the datasheet linked above, 71% DOD would equate to about 350 cycles at the 2 hour rate. 120 is closer to a 1 hour rate, so it could be a little worse.

Based on that, charging once a day its hard to see these batteries lasting much more than a year. That matches up pretty well with the observations of AGM use in EVs, which is a pretty similarly demanding application. Floodies may last a bit longer, but are even bigger and heavier for the capacity. The early cal-cars PHEV Prius conversions also used AGMs, and I don't think any of them made it to a year. The extended life associated with solar use assumes the batteries spend most of their time on a float charge, with mostly shallow cycling and maybe only an occasional deep cycle due to several cloudy days in a row.

Pb batteries also hate to sit at low SOC, so I'd be sure to recharge the PiP as close to driving time as possible and recharge the AGMs as soon as you get home or cycle life could degrade further.

Rob

 

No problem.. was not saying you needed the volt. just questioning the statemnt of 20K in price difference. Many good things about a PiP for some families.


Interesting solution though as others have already posted I think you have underestimated the replacement costs of the AGMs. You might want to rotate the car's AGMs in/out of other solar systems and if you can limit the DOD to less than 70%.. it will give you less miles but more life.

 

It all depends upon the number of panels you have, the wattage, and how much sun exposure you get. Assuming that the battery pack is 5 kWh, and you are using the 8 230W panels the OP specificied, figure about 3 to 4 hours in ideal conditions.

 

thank you!

 

Yes, the PIS kit looks promising, but also more expensive. Do you understand how it works? It seems like the add on battery pack voltage is much higher than the OEM battery pack, so I don't understand how they are put in parallel.

The main gripe I have about the A/C inverter is the efficiency loss going DC to AC then back to DC. If the tradeoff is a DC/DC converter vs an expensive controller, then I might favor the DC/DC inverter. Perhaps an Enginer kit could be made without the battery charger to save a little money and some space.

 

The Enginer approach has the major drawback of only being able to inject a limited (<~16A) of current into the high voltage system. They use the dc:dc converter to throttle the current so as not to throw DTCs. To get around that you have to bypass the stock current sensor. This lets you put in as much current as you like, but now the stock controllers will just ignore the extra energy stored in the add on pack. The pricey controller is required to trick the Prius into using all that extra power available. So if you want full power capability out of the add on pack you are stuck with the extra expense of the controller. These kits are designed for the non-plug-in Prius, so its always possible a more elegant way will be found for the PiP, but its likely you'll still have to trick it even though its already a plug-in.

That's why I find this idea intriguing. If you are considering an add on pack because you cannot charge during the day, the Enginer porta-power approach might let you recharge the PiP pack during the day and get the benefit of a full battery going each way. For that application, you'd get essentially the same performance as a PIS kit at the Enginer price. If you need it for a longer one way commute, this approach won't help.

FYI The PIS pack voltage is higher than the "nominal" voltage of the stock pack, but lower than its fully charged voltage. So if the stock pack is at a lower SOC, when connected current will flow from the add-on pack into the stock pack until the voltage has equalized. At least that's how it works on the non-plugin NimH pack, I assume the idea is similar.

Rob

 

Why can only ~16A be injected into the high voltage system? Would this be the same limit in a Prius Plug-in or is it possible that the limit is higher?

Also, perhaps the limited current isn't as much of a drawback in the Plug-in. I think the OEM battery can supply the majority of power during acceleration, then the add-on battery can either supply power or recharge the OEM battery when cruising or stopped. Regen of course also recharges the OEM. If that's correct, then perhaps the Enginer kit is more useful in a Plug-in than it is in the Liftback.

I agree, but you need more capacity to compensate for the efficiency loss of going DC to AC to DC. If it could be both an add-on pack and a porta-power pack, that would increase the efficiency somewhat.

 

Basically there are two ways you can feed current into the HV system, lets see if I can keep it straight.

The battery ECU tracks SOC by measuring how much current flows in and out of the stock battery, because voltage is not a reliable indicator of SOC in NimH (or Li) batteries. The hybrid ECU also measures the current into the inverter/motors at the other end, to make sure they match reasonably well as a safety/diagnostic feature.

If you tap into the HV lines "outside" the battery current sensor, when current is flowing from the add on pack to the stock pack the battery ECU counts it kind of like regen, and will use that extra power the next time current is demanded. Also in this case any current supplied by the add on pack is _not_ seen by the battery sensor, and so only the actual current coming from the stock pack counts toward the SOC counter. This sounds pretty ideal! Except that under drive if the "extra" current from the add on pack exceeds ~16A (varies with a number of factors) the car will throw a bunch of DTCs and freak out because it does see all that extra current at the inverter/motor end and thinks something is seriously wrong.

If you tap into the HV lines "inside" the battery current sensor, this problem goes away because under drive both current sensors see all the current. Unfortunately, now the battery sensor does not see the current coming from the add on pack into the stock pack, but does see all the current going from the add-on pack out to the inverter & motor. So now at best it just uses the standard ~400Wh of capacity and then starts trying to charge the battery back up. This is why you need a pretty sophisticated controller to "trick" the system into seeing that SOC is still plenty high and it should keep right on using electric drive. Early on this was done by manually triggering the battery ECUs high voltage limit recalibration. On newer kits like the PIS, its done much more effectively by talking to the controllers through the CAN bus. The basic idea is the same on both the Gen 2 and Gen 3 standard Prius as far as I know. Since Enginer and PIS are able to offer these kits on the PiP, I assume it basically the same there too.

I'm wondering that too. If you have a drive with lots of stop and go or speedup and slowdown driving, the Enginer pack might have time to "catch up" while the load is low while the stock pack has plenty of capacity to get through the higher load periods. But for sustained EV cruising, its still not going to put out nearly enough current to keep the stock pack from being discharged faster than it can keep up. Eventually you'll have a dead stock pack and an add on with plenty of juice left but the ICE will have to start.

 

Hm, but couldn't you recharge the stock pack once you reach your destination by just turning climate control off and leaving the car on? This would recharge the stock pack without as much efficiency loss.

 

In theory yes, if you want to leave the car "running." At 16A it might only take an hour or so to recharge the stock PiP pack. You will take some loss, as even with the climate, radio etc all off I believe there is a couple hundred watts of base power draw, but that's probably less loss than the inverter and stock charger efficiency loss assuming you don't leave the car on longer than necessary.

Rob

 

Maybe move all those batteries and inverter onto a minimalist two wheeled trailer.

 

49 cents is sweet, if only the cost of racking them would come down a bit. working on a 10MW farm using 200KW arrays.

 

is that 15 cents per watt while using the 49 cent amphorus panels?