9h1bw
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Using the battery as an emergency supply

Fri Jun 09, 2017 8:07 am

Since my last post I carried out a test to see how efficient it is to use the auxiliary battery to generate a supply in the field. In my case as a supply for my ham radio activity.

I attached a car head lamp to the auxiliary battery and measured the voltage, current, and power in watts. I turned on the ignition to Ready and took measurements every 15min until the fuel gauge notch when down by one. I previously charged the battery to full to start from a maximum supply.

The voltage during the period was 13.96 volts. Thus the dc to dc converter was operational. The current marked 4.3 amps. Thus the bulb consumed 60.73 watts. I took 4.25 hours to consume one notch. Hence the load consumed 258 w/hrs.

To control the power consumption figure I recharged the battery to full and measured the kw/hr to obtain full charge. This marked 1.49kw/hr.

My question is if I used 258w/hr to light the bulb why it took 1.49kw/hr to replenish the Battery? I would assume that the two figures to be close. What is consuming power to make up the difference?

phb10186
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 8:27 am

All the auxiliary electrical hardware associated with running all the HVAC systems, as well as the 12V DC side of things. You are in effect doing something like running your whole desktop PC to power a USB light.

I wonder how sensible it is to keep the car in ready mode for an extended period of time?
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Don
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 8:50 am

Topping off and balancing the traction battery takes more power than you actually used and fully recharging it when you've only used ~5% of it's capacity is going to give you a horrible ratio - Mitsu advises not to plug it in when the traction battery is nearly full. The 12 volt power you used was generated by the DC to DC converter which is probably only 80% efficient. Keeping the car in the 'Ready' mode the entire time has many other things running which are using power

I think if you did full capacity test, i.e. running long enough to take the traction battery down to a low level and then recharged it fully, you could get a ratio closer to 2:1 instead of the 6:1 you got with your short test . . . . but that's just a guess

Don
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9h1bw
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 9:58 am

Thank you both for your replies. Which mirror each other.

It all started out from the fact that Mitshubishi has produced for the Japanese market after the zunami to give distributed power during the emergency. However they never produced it for other markets.

Thus my idea is a non starter.

Thank you for your help.

kiev
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 10:25 am

That was interesting experiment, thanks for sharing.

If you had an inverter then you could generate 120vac to run appliances in your home or ham radio event.

With a high voltage inverter this could be powered from the main pack (360VDC) thru the Chademo port--i would guess that was the tsunami concept.
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9h1bw
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 12:30 pm

Kiev,

Thank you for your suggestion. I would need to find an inverter which has 340v dc input to 230v ac output. I have never seen one on ebay. Any suggestions?

Don
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 1:07 pm

I suspect you would have to build your own inverter . . . . and then you may find you would need some circuitry to enable the high voltage at the DCQC connector - I doubt it's present until a relay is closed

A lot of time, trouble and money for an emergency supply which I trust would not be used very often. The traction battery only has just so many charge/discharge cycles in it before it's depleted. Using those up for something other than driving the car might leave you with a pretty nice car with few miles on it and an unusable battery. The price of a new battery would likely 'total' the car and it would be junk :shock:

4 golf cart batteries in series parallel to run a 12 volt to 120 VAC inverter (or in series with a 24 volt inverter) would probably run your Ham rig all day and at a much lower price . . . . or maybe a little 1 Kw inverter/generator with a 100 foot extension cord. That's the set-up I often see at Hamfests

Don
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kiev
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 3:01 pm

How much power do you need for your application? There are different sizes and suppliers...

http://www.electriccarpartscompany.com/ ... W-Inverter
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Don
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Re: Using the battery as an emergency supply

Fri Jun 09, 2017 3:17 pm

Amazing find! - That would sure do the job and for a small fraction of the price of the OEM Mitsu unit . . . . which isn't even available here

Wonder hoe much a DCQC plug to go with it would cost?

Don
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9h1bw
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Re: Using the battery as an emergency supply

Sat Jun 10, 2017 12:26 am

Kiev,

That is a very interesting option. I would say it should suffice for power as it would consume two notches on the fuel meter and give me 24 hour of autonomy. I need around 120w/hr. I would need to find a 230 v ac at 50 hz one so as not to burn out my equipment. Most of it is rated at 220 volts . It is only in receipt years that the eu standardised to 230 volts.

The price is a problem since it is not sure that the improved power transfer would work and $700 + plus shipping and tax would break the bank for just an experiment at this point in time. It would be cheaper to buy lithium batteries and a solar panel.

Still thank you for your efforts. If any of you comes up with a cheaper option please inform me.
BTW I charge my iMiev with solar power.

Thank you all for your input.

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