Got to thinking this afternoon, and was wondering if perhaps it's time to revisit the idea of building replacement packs from Prius cells. Earlier it seemed that the main obstacle was the "fact" that because the BCM monitored charge in & out, the additional capacity of the Prius cells would be wasted. But if, as a the experiments with double packs seem to indicate, this is not in fact the way the BCM determines SOC, then maybe the extra would be useable. Any thoughts? I see wrecked Prius packs seem to go for not much more than the Civic ones...
Got to thinking this afternoon, and was wondering if perhaps it's time to revisit the idea of building replacement packs from Prius cells. Earlier it seemed that the main obstacle was the "fact" that because the BCM monitored charge in & out, the additional capacity of the Prius cells would be wasted. But if, as a the experiments with double packs seem to indicate, this is not in fact the way the BCM determines SOC, then maybe the extra would be useable. Any thoughts? I see wrecked Prius packs seem to go for not much more than the Civic ones...
It would seem to be a fine option...
I thought the Prius cells were also 6.5Ah... which would mean they would have no additional capacity over the Civic or Insight cells.
From what I have seen the old thinking about the BCM counting AH and monitoring charge in and out all still seems to be correct... What we seem to have learned is that the AH that the BCM counts to is not set at one specific number... but just because the BCM can correct for a greater AH capacity pack does not mean that it doesn't do AH counting... In fact it makes perfect sense that the BCM would adjust for AH capacity changed of the stock pack... Capacity changes with temperature and age pressure , etc.... it makes sense that it would be designed to take the variations into account....
It is still unknown how far the BCM will go ... is 8AH the limit of usable capacity... is 16AH??? or 32AH ??? who knows...
The extra does seem usable the only question is how much more will the car do with a stock BCM??
Personally I still prefer the Boost current type system I or V connected at the MDM power point over the increased AH sitting in the car... similar benefits either way... just some minor differences.
You could be right: I did a search before I wrote the post, but didn't find any numbers on the individual cell capacity. Was thinking that it would have to be larger because of the Prius' ability to go 5 miles or so on electric only. Given that the Prius is so much heavier, that seems way more than could be accounted for just by the larger number of cells.
I also keep thinking of how to divide cells into bunches that could be tucked into the odd spare spaces around the Insight...
The extra distance is probably due to a higher total pack voltage, and lack of having to turn over the engine like the Insight. On Mike's site there is a picture of the battery area of an Insight, except the person has Prius cells installed. You can find this on the mima users page. All the temp probes and battery monitoring connections are simple, so doing a replacement would be easy, just tedious making all of the connections.
I just bought 3 prius packs from a local salvage yard, with the idea of using the subpacks for other purposes.
In checking them out, it occurred to me that If the Prius BCM functionality can be retained, by interfacing to it via the CAN bus, all of the subpack monitoring, SOC determination, and other information required to make it into a safe Insight booster pack would be taken care of and would be available via the CAN interface.
The precharge and main relays, as well as isolated subpack monitoring is all taken care of.
The complete pack fits across the rear deck, or could be set down into the cargo pit with some simple mounting brackets.
The Prius pack voltage of up to 270V when fully charged, and a minimum voltage of 175V would allow charging the stock pack from the Prius pack through a Buck DC/DC converter, and the voltage step down would give increased capacity.
The best part is the price, the packs are getting cheaper, as I got the three for $400 each,
Pretty cheap for a packaged complete solution with BCM.
Want more capacity, put in 3, two across the rear deck, and one in the storage area, and beef up the rear springs. Not as elegant as a lithium pack, but should boost capacity for a lot less money.
A hack into the Civic CAN interface on a Civic BCM could accomplish the same.
Too many projects not enough time.
Cool project, I can't wait to hear how it progresses.
I'll assume with the 270 volts you have the higher voltage Gen I Prius packs, which I've seen at higher prices. I can only assume as more Gen I packs fail that the price will climb again, in my area they are more than $400. It seems in the Priuschat forum that most people find the Gen II packs cheaper to the point where they are taking 2 lower voltage Gen II packs and reconstructing them in the Gen I to make a cheaper and improved Gen I pack, but they are mostly doing it because of the higher cost of Gen I packs and longer perceived lifetime. The Gen II packs will continue to be cheap until they are out of warranty and demand develops but most Gen II's are still in warranty.
Are you removing your 48v Lead Acid boost pack? How have those batteries been treating you, are they wearing out or are you just looking to get a lighter, more powerful and more efficient solution?
You mentioned beefing up the rear springs, would you recommend the air springs or just stronger springs for someone doing this?
MNdriver,
I am talking about gen 2 prius packs, 201V nominal, but on my friends Can view, we saw over 270V max during regen, and ~230V with no charge on his pack.
The point is that for a buck converter, the prius pack is a nice voltage to work with.
I got three gen 2 packs from the salvage dealer so I was able to get the $400 price. I got the impression that he would have went even lower. The packs were listed on ebay with a buy it now price of $449.
I have a silver Insight that I will start to play with.
The batmobile is still running strong, 48V batteries still strong, and the rear suspension is holding up to the 400 lbs that has been installed for going on 3 years, and no problems with bottoming out or handling.
I thought that I had a bent trailing arm but a closer look proved me wrong. I had an alignment done with all the batteries and e-wheel and everything was in spec.
The air springs allow easy ride height adjustment, but listening to the air compressor run each time I drop the e-wheel is a pain in the A**.
A known battery weight with a spring designed for the increased weight will make a better system.
I think that a 120 cell prius based direct Insight pack replacement could also work, just need to do some careful repackaging.
Recently I priced some 2005 packs at $300 each + $75 s/h. My plan was to pick up two packs, along with a few extra subpacks to do a tri-parallel. My hope was to come up with a configuration that could fit in the stock battery area, but at most there is only room for about 40 subpacks. This was based on the measurements of the individual subpacks.
Mike D, I like your plan, I didn't realize you had a second Insight to work with. This plan and the already implemented parallel pack plans seem to the the best bang for the buck and with their own advantages/disadvantages. You have a very big advantage with this design because of how much energy you can put in the car for such a low price.
What wattage can the Buck converters toss out? With three packs in the car, would you have the Prius packs in parallel under discharge and use one converter?
uhtrinity, Would you plan on doing a full pack swap, removing the Insight packs, to replace your current parallel system? What would you do for charge control since the Prius packs swell while charging if not carefully controlled since they aren't in rigid metal cans like the D cells in the Insight packs?
Mike D, I like your plan, I didn't realize you had a second Insight to work with. This plan and the already implemented parallel pack plans seem to the the best bang for the buck and with their own advantages/disadvantages. You have a very big advantage with this design because of how much energy you can put in the car for such a low price.
What wattage can the Buck converters toss out? With three packs in the car, would you have the Prius packs in parallel under discharge and use one converter?
uhtrinity, Would you plan on doing a full pack swap, removing the Insight packs, to replace your current parallel system? What would you do for charge control since the Prius packs swell while charging if not carefully controlled since they aren't in rigid metal cans like the D cells in the Insight packs?
I've decided not to pursue it at this time since 60 subpacks can't fit in the stock location (I still think 40 might). But if I did I would build a lightweight metal cage to contain the batteries in whatever layout works best for the car. These could be single, dual, tri of even quad parallel. Batteries could be installed in the stock location or split between stock and the tire storage area, or all in the bottom like Petes setup.
I'm not sure how safe it would be to parallel the Honda batteries with a matching string of Toyota batteries. However any battery chemistry should be usable as a current limited booster.
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Prius cell revisit?
