# No to bring it up again ...but.....



## glenn davis (Mar 5, 2013)

Hi Folks,

I know this is an oft discussed and old subject but I'm throwing ti out again to see if I am off base.

Subject: Range extending trailer

What I've learned here and elsewhere:

A gen big enough to power a car is too big and too costly.

Most mileage extenders are not helping due to physics involved.

It is obviously simpler and easier to drive a high mpg gas car to do the job if needed.

That being said I want to try this and I am open to all ideas and criticism.


The concept is to add a tow behind, very light motorcycle trailer. On that trailer would be my main charger, five extra 12 volt deep cycle batts that are like the ones in the car. and a generator just big enough drive my charger to charge either the full pack or the extra 60 volts. I don't intend to charge the main pack n the fly. I just want to kick in the 60 volts as needed, be able to charge to 60 volts off line while not being drained or park and charge the main pack away from home and parked.

My goal is to add 5-10 more miles to the 30 I already get, have the extra volts available when needed and have the mobile charging capacity. 

My question is how to integrate the extra 60 volts when applied so as not to harm the main batts. they would be added to the eleven 12 volters that would be down some. Go parallel, go series and where in the chain to put them?

What would be a good approach?

If I sound like the typical mad scientist I am pretty sure I am in good company here! LOL

Thanks, Glenn


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## valerun (Nov 12, 2010)

glenn davis said:


> Hi Folks,
> 
> I know this is an oft discussed and old subject but I'm throwing ti out again to see if I am off base.
> 
> ...


If I were to do something like this, I would instead focus on designing my own 20kW genset with a high voltage PMAC motor and a small 4-stroke motorcycle engine. Similar to BMW REX set. That system could be made to weigh ~200lbs all-in and possibly fit in the trunk of a normal car.


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## rmay635703 (Oct 23, 2008)

Most any generator made in the last 20 years lists how many gallons per hour it uses at a given load. After that are losses in the "charger" you use and possibly your batteries.

A small PROPER genset works WELL for extendeding your range somewhat but not indefinately. Obviously most gensets will provide LOW fuel economy.

In other words if the genset is large enough to double your range before you run out of juice its probably fine, any larger and the weight makes it not worthwhile, smaller is also OK but may not do enough.

The only genset I have found that gets GOOD fuel economy is the following
http://www.generatorsales.com/order/yanmar_4kw.asp?page=yanmar_4kw

At low speeds 50-80mpg are possible (on small EVs) ideally you would need a DC head and a controller/injection pump to allow the genset to rev up and down. As is (AC) its good but its output is more limited than it would need to be.

It could support most EVs up to about 25mph, some like my little antique up to about 35-40mph, faster and you drain the battery but more slowly, at stops you gain range but less efficiently.

Cheers
Ryan


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## Duncan (Dec 8, 2008)

Hi Glen

You really don't want to be connecting two packs at different charge states together,

If you avoid doing that your concept could work OK

Always have both packs of full charge when you connect them together
Run both packs in parallel while driving,
Leave them paralleled up while doing your parked charge - no good reason not to run the generator while driving

I would assume in normal use the trailer stays parked somewhere,

Before hooking it up charge both up to max (sensible for a long trip),
Once hooked up keep both together, don't do anything to charge or drain either independently
At the end of the trip disconnect and recharge seperately


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## Karter2 (Nov 17, 2011)

glenn davis said:


> The concept is to add a tow behind, very light motorcycle trailer. On that trailer would be my main charger, five extra 12 volt deep cycle batts that are like the ones in the car. and a generator just big enough drive my charger to charge either the full pack or the extra 60 volts. I don't intend to charge the main pack n the fly. I just want to kick in the 60 volts as needed, be able to charge to 60 volts off line while not being drained or park and charge the main pack away from home and parked.
> 
> My goal is to add 5-10 more miles to the 30 I already get, have the extra volts available when needed and have the mobile charging capacity.
> 
> My question is how to integrate the extra 60 volts when applied so as not to harm the main batts. they would be added to the eleven 12 volters that would be down some. Go parallel, go series and where in the chain to put them?


 to be clear..
Your main pack is 11x12volt = 134 volt pack.
you suggest a 5x12volt = 60volt "auxiliary" pack on the trailer .
The aux Generator would be a 60 volt genset ?

You want to "add" that 60 volts to the main system at times ?
Unless your main system ( controller, motor, fuses, etc etc, ) can handle 200V , i dont see how you can make that work at all !

Your aux battery pack will need to be the same voltage as your main pack


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## glenn davis (Mar 5, 2013)

Thanks Folks,
I've got my head around that concept....DON'T use mismatched battery packs. Now I'm thinking the best way to go is to add two more twelve volters to make 156 volts. I will check all specs, charger, controller, motor on that.....add the generator and charger to the aux trailer. I don't have a smart charger so I can adjust to either 132 or 156 manually. How do you change the 120volt AC output to DC and apply to the whole pack? Do you build a rectifier? I'm not sure on that. Do you apply that voltage at the charging leads? I'm fuzzy on advanced applications however I have apretty good handle on the car as it sits! Thanks for all the help and not dumping on my ignorance.

Glenn


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## rmay635703 (Oct 23, 2008)

glenn davis said:


> How do you change the 120volt AC output to DC and apply to the whole pack? Do you build a rectifier? I'm not sure on that. Do you apply that voltage at the charging leads? I'm fuzzy on advanced applications however I have apretty good handle on the car as it sits! Thanks for all the help and not dumping on my ignorance.
> 
> Glenn


Easiest method is to use a battery charger that runs off the common AC output of the genset. This is also not as efficient.

Another way is a magnetron/magneto or DC generator many military gensets can be purchased in DC or AC versions, it would need to be matched to the voltage of your batteries.

3rd DIY option is to run a matched voltage AC genset through a rectifier, it needs to be overbuilt and antique with a throttle, you throttle it up until the power output of the genset meets the desired spec, generally your ICE will limit output as it can only generate so much power.

3rd option can result in overload and overheat but is simpler than a finding a DC head and having it rewound


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## glenn davis (Mar 5, 2013)

Thanks,
I was thinking of using the charger. The question then would be... is it capable of withstanding lots of amperage flowing through it? Will is stress the charger too much? Also if I locate a DC charger, where would one apply it to the pack?


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## palmer_md (Jul 22, 2011)

Just buy 40 of the CA40FI CALB LiFePo4 Cells and put that in the trailer and parallel it to the lead in the pack. That will cost about $2400 and will give you more than the 10 miles range your looking for. Its about 5kWh and if you get even 3 miles/kWh you should add 15 miles range.

I doubt you can find a genset for $2400, let alone add the lead acid cells, the charger and such, and it would only weigh 132 lbs.

here is one possible source. http://store.evtv.me/proddetail.php?prod=CA40FI


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## ga2500ev (Apr 20, 2008)

palmer_md said:


> Just buy 40 of the CA40FI CALB LiFePo4 Cells and put that in the trailer and parallel it to the lead in the pack. That will cost about $2400 and will give you more than the 10 miles range your looking for. Its about 5kWh and if you get even 3 miles/kWh you should add 15 miles range.
> 
> I doubt you can find a genset for $2400, let alone add the lead acid cells, the charger and such, and it would only weigh 132 lbs.
> 
> here is one possible source. http://store.evtv.me/proddetail.php?prod=CA40FI


This is the correct answer. There is a long standing thread of Ziggy's that describes how to do it. 

The key point is understanding that the stiffer voltage of the lithium helps to buffer the lead acid and extends the amount of power it can deliver. So there's an additive effect over and above the amount of energy that the lithium contributes.

ga2500ev


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