# Charger Loss Mitigation



## dougingraham (Jul 26, 2011)

ElectriCar said:


> I've gone almost 1000 miles in the last three weeks at roughly 400Kw from the utility. If I'm wasting 12.4% on charging that's about 50Kw in three weeks of WASTED energy! At that rate that's about 900Kw/year. With electricity rates climbing this is going to add up for Lithium battery pack driven vehicles.
> 
> Anyone know if these things can be made more efficient?


They can be made more efficient. You are looking at less than $100 per year of cost in electricity for the losses. With not a lot of effort the efficiency could be in the low 90's maybe as high as 95%. I am guessing that at the power levels we are talking about you might see 4 or 5 % increase so maybe $30 or $40 per year savings but at a cost with current demand of an additional $1000 in the quantities they are being produced.

I would like to see it happen but at this stage of the game it probably isn't worth it.


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## Ziggythewiz (May 16, 2010)

Mine gets crazy toasty, so don't need any meter to tell me it's wasting a good chunk of energy 

Can't say I care much though as prices here have gone down a penny/kwh/year for the last 5 years. At this rate electricity will be free in 8 years


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## GizmoEV (Nov 28, 2009)

If the NG5 has a similar efficiency to my NG1, yours is in the same ball park efficiency wise. If your wall meter "charges" you for a PF lower than 1.0 then that is one place where your efficiency readings might be worse. The NG1 has a PF of about 0.7. The NG1 manual lists the efficiency at >85%. I looked up the NG5 manual and it has an efficiency >87% so your numbers are right in line.

Be glad you aren't running your lead acid batteries any more. In my Gizmo I went ~3.9mi/kWh from the wall with my T-875 batteries. With my LiFePO4 set I go 5.5-6mi/kWh. Just the battery change gave me over a 37% efficiency boost! This is still true if I add weight to do a same weight comparison!


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## ElectriCar (Jun 15, 2008)

dougingraham said:


> They can be made more efficient. You are looking at less than $100 per year of cost in electricity for the losses. With not a lot of effort the efficiency could be in the low 90's maybe as high as 95%. I am guessing that at the power levels we are talking about you might see 4 or 5 % increase so maybe $30 or $40 per year savings but at a cost with current demand of an additional $1000 in the quantities they are being produced.
> 
> I would like to see it happen but at this stage of the game it probably isn't worth it.


You're right, about $90/year. At this time I'm paying about a dime per KW at the office and just under 8c at home. However the power company is looking for a 17% rate increase, in fact they had a public hearing tonight in the area. They just got a 10% increase on commercial customers in the last 12 months! Obama unbelievably says here it's necessary for electric rates to skyrocket and evidently he's making it happen. 

Also with a 32Kw lithium pack & 100mile + range, I'm just now getting to the point of driving it daily so I'm not sure how much I'll end up averaging in a year. At this early juncture though it's much more than I did with lead. 

So any idea what the parts should cost if I sent it off for an upgrade? I just wonder if Greg at Zivan US could do that. If rates or my mileage increase it may be worth it.


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## ElectriCar (Jun 15, 2008)

GizmoEV said:


> If the NG5 has a similar efficiency to my NG1, yours is in the same ball park efficiency wise. If your wall meter "charges" you for a PF lower than 1.0 then that is one place where your efficiency readings might be worse. The NG1 has a PF of about 0.7. The NG1 manual lists the efficiency at >85%. I looked up the NG5 manual and it has an efficiency >87% so your numbers are right in line.
> 
> Be glad you aren't running your lead acid batteries any more. In my Gizmo I went ~3.9mi/kWh from the wall with my T-875 batteries. With my LiFePO4 set I go 5.5-6mi/kWh. Just the battery change gave me over a 37% efficiency boost! This is still true if I add weight to do a same weight comparison!


Yes I got a big boost also but now I'm using the heater and lights some. That 1500W ceramic heater on 165V puts out a lot more heat than it did at 130V or so but it's well worth it!  I think it's putting out about 2300W with the fan blowing. 

Also with the lithium I drive less efficiently, faster etc. BECAUSE I CAN!  Still I'm saving probably 20-25%. The lowest wh/mile FROM THE WALL I've ever gotten was 316.7 and a few times at the 330ish area. With the heater/lights on I often get to work at around 475. Oh I've added a trailer hitch ball to the bumper. One run with that thing on the interstate was at 533!


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## GizmoEV (Nov 28, 2009)

ElectriCar said:


> Also with the lithium I drive less efficiently, faster etc. BECAUSE I CAN!


Same here. That is probably why I am not getting 6mi/kWh all the time.



> Still I'm saving probably 20-25%. The lowest wh/mile FROM THE WALL I've ever gotten was 316.7 and a few times at the 330ish area. With the heater/lights on I often get to work at around 475. Oh I've added a trailer hitch ball to the bumper. One run with that thing on the interstate was at 533!


Thanks for posting those numbers. I'm still wanting to convert an S10 down the road and real numbers are hard to come by. I assume those are all measured from the wall, right?


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## ElectriCar (Jun 15, 2008)

Yes those numbers were from the wall. I can get under 300/mile and don't have to work too hard to get there but I just don't need to anymore. I may do one trip to see how low I can go. I used to haul lead around and tried to keep it under 40, going particularly easy up hills to stretch my mileage.

At this time I'm averaging 400.5wh/mile from the wall but as mentioned I'm often using the heat, lights and towing a trailer some as well. I can send you my spread sheet that is sort of a patchwork of data but you will get a good picture of what you can expect. If I still have your email I'll send it to you.


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## madderscience (Jun 28, 2008)

If you live in a cooler climate, mount the charger in the cabin of the vehicle someplace so that it helps to heat/defrost the cabin while charging. Then for at least the cold months of the year, it isn't wasted energy.


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## EVfun (Mar 14, 2010)

So the charger is about 89% efficient? (losses are 12.36% of the power supplied to the pack) Are you comparing watt hours from the wall to watt hours into the pack?

Usually batteries are charged based on amp hours instead of watt hours because they are storing electrons (in a chemical reaction.) If you are comparing watt hours from the wall to watt hour into the pack I have a question about LiFePO4 efficiency. What is efficiency of you pack based on watt hours into the pack compared to watt hours removed from the pack?


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## ElectriCar (Jun 15, 2008)

EVfun said:


> So the charger is about 89% efficient? (losses are 12.36% of the power supplied to the pack) Are you comparing watt hours from the wall to watt hours into the pack?
> 
> Usually batteries are charged based on amp hours instead of watt hours because they are storing electrons (in a chemical reaction.) If you are comparing watt hours from the wall to watt hour into the pack I have a question about LiFePO4 efficiency. What is efficiency of you pack based on watt hours into the pack compared to watt hours removed from the pack?


Hi fun, yea I run a Cycle Analyst (CA) which monitors the pack voltage and amps constantly. It displays the Ah used in a totalizer fashion on the pack, which is good when you do a partial charge. Ie you start with 0Ah when you finish charging, then drive and use 50Ah, add 10Ah back with a quick partial charge and it displays 40Ah. It also gives you a wh/mile if you have a speed input to it. 

When I get ready to charge, the CA has a total watthours I can scroll to and I record that. Then on my spreadsheet I enter that, the total miles driven and when finished charging, the KW used from the charger KW meter. The spreadsheet then calculates the Wh/mile from the KW meter and the pack then displays the difference between the two in a % fashion.


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## GizmoEV (Nov 28, 2009)

EVfun said:


> So the charger is about 89% efficient? (losses are 12.36% of the power supplied to the pack) Are you comparing watt hours from the wall to watt hours into the pack?


Don't you mean (losses are 12.36% of the power supplied to the *charger*)?


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## dougingraham (Jul 26, 2011)

ElectriCar said:


> So any idea what the parts should cost if I sent it off for an upgrade? I just wonder if Greg at Zivan US could do that. If rates or my mileage increase it may be worth it.


I don't see this as a retrofit kind of thing. It really needs to be designed from the ground up with efficiency in mind.

Best Wishes!


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## EVfun (Mar 14, 2010)

ElectriCar said:


> When I get ready to charge, the CA has a total watthours I can scroll to and I record that. Then on my spreadsheet I enter that, the total miles driven and when finished charging, the KW used from the charger KW meter. The spreadsheet then calculates the Wh/mile from the KW meter and the pack then displays the difference between the two in a % fashion.


Only part of the difference in watt hours is losses in the charger. The other part is the difference between the discharging battery voltage and the charging battery voltage. The watt hours out of the battery will be less than the watt hour returned by charging. To determine charger loss you need to measure the watt hours returned during the charge (instead of watt hours used) and the watt hours drawn from the wall.


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## ElectriCar (Jun 15, 2008)

For all intents and purposes...I'll go with what I'm doing, but I see what you're saying, just think it's not relavent for me nor significant.


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## JRP3 (Mar 7, 2008)

Tomofreno has measured his Manzanita PFC30 at 94% I think, which if I remember right is about what mine is.


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> For all intents and purposes...I'll go with what I'm doing, but I see what you're saying, just think it's not relavent for me nor significant.


Well you're talking about energy wasted from charging efficiency but you seem to be adding in energy lost during discharge as well, skewing the results.


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> Well you're talking about energy wasted from charging efficiency but you seem to be adding in energy lost during discharge as well, skewing the results.


That's all I can determine with the equipment installed. I just figured this way would be a pretty accurate depiction of the charger losses. Not sure how to figure EXACTLY how much the charger is wasting though, just assumed of that 12%, most would be from the semiconductors in the charger.


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## EVfun (Mar 14, 2010)

If you average discharge voltage is 3.15 volts and your average charging voltage is 3.35 volts then half the losses you are seeing are battery pack losses.


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## ElectriCar (Jun 15, 2008)

EVfun said:


> If you average discharge voltage is 3.15 volts and your average charging voltage is 3.35 volts then half the losses you are seeing are battery pack losses.


OK now I'm confused.  Do explain because inquiring minds want to know.


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## EVfun (Mar 14, 2010)

If I understood your method of checking efficiency, you are comparing watt hours out of the battery pack to watt hours into the charger. Some of those losses are in the charger, but some are in the battery pack. Watts equals volts time amps, so if the discharge voltage is lower than the charging voltage (and it always is), 1 amp hour out of the pack will be less watt hours than 1 amp hour into the pack. 

1 amp hour at 3.15 volts is 3.15 watt hours (out of the cell)
1 amp hour at 3.35 volts is 3.35 watt hours (into the cell)
In this example the cell is 94% efficient. 

Batteries store amp hours. A lithium ion goes through the electrolyte while an electron goes through the circuit. To recharge a battery you have to return all the amp hours removed, not all the watt hours removed.


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## ElectriCar (Jun 15, 2008)

EVfun said:


> ...
> 1 amp hour at 3.15 volts is 3.15 watt hours (out of the cell)
> 1 amp hour at 3.35 volts is 3.35 watt hours (into the cell)...


I thought that may be what you were thinking about. 

Not sure the CA averages the pack voltage somewhere but I'll look into that. If it does then I can make some sort of adjustment in my spread sheet to make it more accurate. I'd still like to make the charger more efficient as when it's running it's generating a good bit of heat.


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## GizmoEV (Nov 28, 2009)

After a drive take the CA Wh figure and divide by the Ah figure. That will give you an average discharge voltage. The CA doesn't count Wh on charge but it does decrement the Wh/mi figure. You might be able to estimate the difference from that.


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## ElectriCar (Jun 15, 2008)

Thanks I'll do that. Have you tried it and applied that data to your data or do you utilize a wall meter?


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## GizmoEV (Nov 28, 2009)

Because I charge as such a low rate and the LFP batteries are so efficient I've basically just done what you have to get an estimate. I have regenerative braking so that messes up the Wh/mi figure to estimate charger efficiency. The difference is that one is charging efficiency and the other is charger efficiency. Up until now I was only concerned with charging efficiency. Probably because of such a high increase in it when going from lead acid to LFP.


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