# 12 volt solutions?



## steelneck (Apr 19, 2013)

Does anyone have experience using the alternator from the ICE together will a small pack of 4 lithiums in series? Will the constant trickle charge from the alternator hurt the cells?


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## jhuebner (Apr 30, 2010)

In my Ligier there is a regular switch mode power supply rated for 230Vac (~320Vdc) connected to 180Vdc. This solution is working since 1993. At 256V this should work perfectly in your car.

For my Polo I got a switch mode power supply from ebay and have it recharge the 12V battery whilst the main traction pack is recharged. Of course it works but its not really a proven concept. The 12V battery has to run all consumers so it better be a good one.
On the plus-side there is absolutely no trickle load when the car is off.


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## dragonsgate (May 19, 2012)

For the first couple of years I used only a deep cycle 12 volt battery for my auxiliary. I charged it when I recharged the main pack. It worked for day time driving but get caught after dark and I was feeling my way home. I put a blower on my motor which deeded more power so I installed a 70amp Marelli alternator with a V belt. It kept my aux. battery charged and by the seat of the pants I notice no measurable loss on my battery pack or performance. I did have trouble keeping enough tension on the belt to keep it from squealing when there was a change in motor rpm. I went to a cog belt and eliminated the squeal problem plus I do not need as much tension so it is easier on bearings. The draw backs of an alternator are the extra weight and arguably the drag on the motor. Also when you come to a stop or below certain rpm the alternator does not charge bleeding electricity off the battery through the windings. All in all I am happy with my setup mainly because of its low cost and it has been trouble free. If it does ever go out I can replace it for a few bucks compared to a few hundred buck$


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## dtbaker (Jan 5, 2008)

I used just an 'always on' Curtis dc-dc for a long time with no problems. 

I upped pack voltage, used a different (cheap Chennic) which proven short-lived, twice. I added a small (4ah) aux in series because the Chennic sagged and 'blinked' when my vacuum pump came on with headlights and heater fan also running. It died regardless.

Switched to an open chassis 600 watt ACME 'always on' dc-dc, no problems.


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## steelneck (Apr 19, 2013)

Thank you all for your input on this issue, it feels like this is a somewhat overlooked issue.

My last option with the large battery that gets charged when the traction pack gets charged, goes out. I live in cold climate and can sometimes use the 12v quite a lot, like seat warmers, rear window warmer, rear view mirror warmer and so on. Without additional power that would drain the 12v battery heavily and make my headlights into glowing candles..



jhuebner said:


> In my Ligier there is a regular switch mode power supply rated for 230Vac (~320Vdc) connected to 180Vdc. This solution is working since 1993. At 256V this should work perfectly in your car.


Switch mode power supply.. This is interesting, especially since it has been working since 1993 for you. What do you mean by "regular", are you talking about something like computer PSU, or some adjustable lab power supply? I really would like to know more about this.



dtbaker said:


> Switched to an open chassis 600 watt ACME 'always on' dc-dc, no problems.


Open chassis 600 watt ACME.. What is that? I just get tons of irrelevant hits when searching.

What about a battery charger running on my 256v DC?


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## dtbaker (Jan 5, 2008)

steelneck said:


> I live in cold climate and can sometimes use the 12v quite a lot, like seat warmers, rear window warmer, rear view mirror warmer and so on.


good reason to siphon directly off main pack.

...looks like it has been re-labled as the 'MW' unit, available at http://evolveelectrics.com/DC-DC Converters.html for just $178


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## steelneck (Apr 19, 2013)

dtbaker said:


> good reason to siphon directly off main pack.
> 
> ...looks like it has been re-labled as the 'MW' unit, available at http://evolveelectrics.com/DC-DC Converters.html for just $178


Yes, all power has to come from the main pack one way or the other. That MW unit looks promising, with a quite low price tag too. It delivers 635W, a figure i will exceed quite a bit under short periods. I suppose a small lithium pack or a lead acid could act as a buffer. Will the batteries or that unit be happy with that?

One thing though, it is fan cooled, blowing air at open electronics .. Think dusty roads one day, even with magnetic particles, rain and condense the other, add to that temperatures fluctuating below freezing.. for years. Automotive electronic gizmos should be completely sealed, even mould in rubber in extreme cases. I guess that unit was not initially designed for automotive use. But it could be durable drawing air from inside the cabin, though maybe creating a sound problem.


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## onegreenev (May 18, 2012)

I have a 4 cell Lithium pack for my 12 volt pack. Each is 100ah so I have plenty of power on tap. I used a DC DC with my 96 volt system with no trouble. Once I got up to 156 volts I just went with my Lithium Aux battery. Don't use standard car batteries. A combo of DC DC and Lithium Aux battery should be good and yes, many have used a standard alternator but remember that when your stopped so is your alternator. 

Pete


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## dtbaker (Jan 5, 2008)

steelneck said:


> Yes, all power has to come from the main pack one way or the other. That MW unit looks promising, with a quite low price tag too. It delivers 635W, a figure i will exceed quite a bit under short periods. I suppose a small lithium pack or a lead acid could act as a buffer. Will the batteries or that unit be happy with that?
> 
> One thing though, it is fan cooled, blowing air at open electronics .. Think dusty roads one day, even with magnetic particles, rain and condense the other, add to that temperatures fluctuating below freezing.. for years. Automotive electronic gizmos should be completely sealed, even mould in rubber in extreme cases. I guess that unit was not initially designed for automotive use. But it could be durable drawing air from inside the cabin, though maybe creating a sound problem.


It's been pretty solid under the hood for over a year so far.... better than the sealed Chennics. I had a sealed Curtis, but it had a much lower voltage limit, lower output and was 4x the cost. Belktronics is sealed as well and a durable unit, but also at least 2x the cost.

I'm considering adding a HEPA filter or at least a air filter on the intake side to help keep the dust out .... but you wouldn't want to wash it down with water by mistake as the unit is NOT intended for direct exposure to water. My motor bay is 'fairly' sealed up, but not intended for a power wash by any means.


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## zeva (Nov 4, 2013)

Just a quick comment on using four (LiFePO4) lithiums as your 12V aux battery.. It works fine, so long as you can guarantee the overall voltage stays between 10V to 14V.

I've seen such packs damaged both from overcharging and over-discharging. In one case the vehicle's alternator was putting out over 14V which pushed one cell over 4.2V, which killed it and caused a cascading failure of the other cells too. In another case, the EV was left unused for a long time and the quiescent 12V load completely flattened the cells, with one going negative voltage (fatal). Top balancing or bottom balancing can help mitigate risk at either the high or low end respectively, but not both. Best solution IMHO is to top balance, with a low voltage cutout to protect the cells from over-discharging.


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## onegreenev (May 18, 2012)

If you use an alternator to charge then you should put in a resistor to be sure you don't go over 14.6 volts output max. As it is, my 96 volt DC DC outputs 13.6 volts so no chance of overcharge. My other DC DC puts out 14.6 volts and won't over charge beyond 3.65 volts each. So no issues there either. I also don't leave my DC DC on all the time. That means I must from time to time recharge the Aux battery. No problems.


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## onegreenev (May 18, 2012)

zeva said:


> Just a quick comment on using four (LiFePO4) lithiums as your 12V aux battery.. It works fine, so long as you can guarantee the overall voltage stays between 10V to 14V.
> 
> I've seen such packs damaged both from overcharging and over-discharging. In one case the vehicle's alternator was putting out over 14V which pushed one cell over 4.2V, which killed it and caused a cascading failure of the other cells too. In another case, the EV was left unused for a long time and the quiescent 12V load completely flattened the cells, with one going negative voltage (fatal). Top balancing or bottom balancing can help mitigate risk at either the high or low end respectively, but not both. Best solution IMHO is to top balance, with a low voltage cutout to protect the cells from over-discharging.


The best is to bottom balance the cells just in case you over discharge the Aux battery. That way no single cell will die from over discharge. I have a built in safety anyway. My current controller will actually shut off if my Aux voltage reaches 11.6 volts and that means my Aux is sitting at 2.95 volts each cell. Far from being dead. But because my controller shuts off I know I have no further power to run the vehicle. My DC DC will output 13.8 or with my higher pack voltage to 14.6 so I can still power my Aux electronics. As long as my DC DC is working and my pack is still powering my vehicle I have to troubles. My controller also won't let my pack go below a set point no matter what. 

Pete


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## jhuebner (Apr 30, 2010)

steelneck said:


> Switch mode power supply.. This is interesting, especially since it has been working since 1993 for you. What do you mean by "regular", are you talking about something like computer PSU, or some adjustable lab power supply? I really would like to know more about this.


Something like this:
http://www.ebay.de/itm/LED-Netzteil...tzteil-Netzadapter-Power-Supply-/271111873536










Of course you can go for a regular battery charger as well, as long as it is a switch mode one.
For any solution where you use an AC/DC converter as a DC/DC converter it is recommended to bridge the internal rectifier as it has to carry twice the current in DC-moden (2 diodes always conduct, 2 never conduct)


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## sabahtom (Mar 1, 2011)

*Vicor in the cabin*

I've seen some Vicor Megapacs come up on ebay that do over 80 amps at 12-12.5v, but rarely see them with trim pots. Seems like a lot of work to get them to charge a battery at 13.6v or so without a built-in trim pot.

I probably won't take my EV further than 15km from home, but I hope to get a DC aircon so I need a lot of amps. The Masterflux unit here draws 40A max, within range of some of the Vicors I've seen. Reason is its hot here and the traffic is slow.

Is there any point to having an aux battery in this case? If the Vicor fails I would end up getting towed I guess, unless I was lucky enough to get a unit with a spare 12v module.

I have one big battery box in the back of my minivan. Any reason not to put the DC-DC next to the battery, nice and dry inside the cabin? Noise I guess.


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## spoland (Aug 9, 2012)

*Re: Vicor in the cabin*

I am planning to use a Meanwell SP-750-12 which is an isolated switching power supply intended for use with 220VAC, but can handle up to 370VDC on input. It delivers 13.5 VDC at max 62A which should keep a small lead acid battery charged.
The only drawback I have noticed with it is that it is quite noisy. Theres is a small, high rev fan in it that is quite loud.
I am sure there are other isolated power supplies out there as well. Make sure it is isolated though.


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## steelneck (Apr 19, 2013)

So far it looks like i have talked my self into using the alternator from the donor car and maybe something like a 30-40 Ah lead acid, but i am still considering lithium for the aux battery. It is nuts n bolt simple, cheap, no isolation problems and time tested reliable in extreme. I am also looking into if it could be coupled direct drive to the acc. end of the EM, since the EM on average will spin at much higher RPM than the ICE. There are alternators that spins the other direction.


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