hybrid to mild phev conversion?

[IamIan]

One other thing to consider is the magnitude of the possible benefit ... in addition to the possible issue raised of more cycles per year generally means fewer years of useful battery life.

You can calculate the maximum possible benefit if you know the general system efficiency and the battery size ... just compare the energy contents.

For example ... a Gen-1 Honda Insight OEM Battery has at most ~6.5Ah , 144 V Nominal = 936 wh max from 100% to 0% DoD window ... that generation IMA system is around ~90% efficient ... so maximum possible would be ~842Wh of plug in energy to the wheel ... Although in practice it would be much lower than this , because you don't get the full 100% window , and peukert effects , etc ... in practice about ~470 wh to the wheel is more likely ... but even at the max upper end ideal ( a bit unrealistically optimistic case ) ... at roughly ~36 kwh of chemical energy per gallon and roughly 35% efficient ICE that ~842 Wh would only offset / replace at most about ~0.06 Gallons per such full 100% cycle charge... or from the ~470Wh more realistic case ~0.03 Gallons offset per such full cycle... it's something ... but is it enough to justify doing it... that's up to the individual.

[dluck]

I'm not sure I buy Cobb's assertion that topping off the batteries every night would reduce the life of the batteries.
a) Owner's of cmax energi's does this now, as does any other plugin EV or PHEV
b) The charge/discharge cycle during normal driving is several times a day as the battery runs down and then is recharged either by ICE or by regenerative braking.
c) Slow charging up the battery overnight so that you start with a fully charged battery in the morning would directly allow the engine to primarily be used to move the car forward and not recharge the batteries when you might need extra power to get going.
d) The slow charge using 120V plug would probably be gentler (less heat) on the batteries then fast charging with the ICE.
e) It seems to me that topping off the Etank overnight would reduce the number of charge/discharge cycles.

[Cobb]

Go for it. I am just repeating what Ive read on the insightcentral form where a lot of smart people learn from their mistakes.

BTW, we have a few vendors that sells, rebuilds and replaces hybrid batteries too.

[dluck]

The latest information I have says that for li-ion battery packs you want to keep them charged between the range of 20-80% to maximize battery life.
Design News - News - Can EV Batteries Last 20 Years?
So a way to arrive home with about 20% left and a slow charge (slow also extends life) to 80% seems to me to be ideal. That would be about 60% of 1.4kWh or 840watt hours. A 200W charger I think wouldn't be that expensive.
Now there already is a couple of charging electronics designed in every c-max. The braking regenerative recharge system and the ICE driven charger. (At this time I'm not sure if they are actually the same). But if we could use those circuits that must already be conditioning the power to charge the battery then the 120V charger might not be that expensive. Anyone know where an electrical diagram of the CMAX could be downloaded?

[rmay635703]

Originally Posted by Cobb

Go for it. I am just repeating what Ive read on the insightcentral form where a lot of smart people learn from their mistakes.

BTW, we have a few vendors that sells, rebuilds and replaces hybrid batteries too.

This flies opposite to the experience of Insight G1 owners who have marginal packs, the trouble I forsee is that the various types of cells will behave differently and have different charge requirements, where my 13 year old pack likely enjoys a charge to be functional, perhaps a new pack should only be charged partway?

To balance the cells in an Insight G1 pack may need to charge at a very slow rate for up to a little over a full day, so perhaps we aren't all talking the same language.

Cheers
Ryan

[Cobb]

Great subject and from what Ive read I am convinced no one really knows the correct answer, however there are plenty of examples that damage and shorten pack life.

Ok, first off we need to communicate if we are talking about % of charge of the pack itself or what the car uses which is typically less like 80%.

For example in the gen 2 insight I see 3 voltages, the car considered 112 to be 90% to full at times, 117 is FULL according to the SOC meter 121 is considered full and balanced hot off the charger.

I am guessing you are saying precharge the pack in this example to 112-117 volts or somewhere in the middle like 115 volts? Yeah, I can see that being some benefit and likely ok as long as its monitored. You could stack a few meanwell power supplies and fully charge the insight pack in 3-5 hours depending on its current soc.

Now if the car has lifepo4 or some form of lithium cells those go up fast in voltage when a cell is fully charged vs the rest, so if you are charging the pack you need to make sure it has some type of active bms and that system is fully operational if you are going to tap a few electrodes and back feed power to it like the Honda and prius guys do.

[dluck]

IamIan's comment prompted me to calculate the benefit in another way. Based on charging the battery with a max of 840Wh everynight and using a DoE rating of 220-265wH per mile this would mean about a max of 3 miles of additional electrical range per day. Depending on your daily driving habits this could be a lot or could be a little. Is it worthwhile? Good question, both in terms of the financial investment, and time to plug it in everynight to get 3 additional miles without needing to burn gas from the tank. I think the answer is different for each owner.

[rmay635703]

Originally Posted by dluck

IamIan's comment prompted me to calculate the benefit in another way. Based on charging the battery with a max of 840Wh everynight and using a DoE rating of 220-265wH per mile this would mean about a max of 3 miles of additional electrical range per day. Depending on your daily driving habits this could be a lot or could be a little. Is it worthwhile? Good question, both in terms of the financial investment, and time to plug it in everynight to get 3 additional miles without needing to burn gas from the tank. I think the answer is different for each owner.

3 miles over a long trip may take care of all of your acceleration events, which is where your fuel economy drops into the basement.

So I would argue charging the pack (safely) for whatever paticular chemestry and type is in there is likely of benefit.

The pack is MADE to charge and discharge, to say you can't charge a pack due to wear, that the car repeatedly charges and discharges everyday is false.

Incorrectly charging the pack or taking it outside the best life charge level is another matter altogether.

Trickle charging as done on a G1 insight with a failed pack is altogether different than how you would approach the matter on a new car with a good pack.

Cheers
Ryan

[Cobb]

Its just a shame all of our "hybrid phev experts" do not actually own or drive a hybrid nor have a phev kit installed.

If you ever get a chance to drive one you will see you actually get more mpg without using any of the hybrid systems. Thats right.

[dluck]

Cobb,
I don't believe anyone disagrees with the assertion of getting better mpg. What is being discussed is the potential costs: battery lifetime (better or worse), costs of installing a charging kit. Some estimated it to be upwards of $900 just for charging. Time to plug the car in every night when returning home. Can you get each person that's driving the vehicle to commit? Is there a potential to void the warranty?
cheers