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EV power up

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Moderator: kchiang

EV power up

Postby jstack6 » Mon Aug 27, 2012 2:43 pm

A friend called me when his GM G-20 EV, large all electric van would not power up. I drove over and towed his large van back to his home with my Honda CIVIC hybrid.

After checking a few things we found his dumb old Lead Acid starter battery was low. A boost and it was off and running again. The start up battery on many EV's is a weak spot. With that little power source low, the entire EV will not power up and get moving.

A few EVs use a DC -DC converter to use the main pack as a start up 12 v dc source. The Nissan LEAF uses a separate little LEAF ACID battery for start up ! Someday we will have better designs.
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Re: EV power up

Postby kchiang » Fri Sep 07, 2012 12:53 pm

I just got back from a 10 day vacation to a dead 12V auxiliary battery. The 12V that I use is a sealed lead acid AGM 7AH. My MR2 EV is wired such that the DC-DC converter only charges the 12V battery from the main 144V traction pack when the ignition is turned on. As Jack pointed out, if the 12V battery dies, then I will not be able to turn on the ignition to start charging the 12V battery. This worries me on those long away trips if I ever need to park my car at the airport. The longest time I've been parked without a dead battery was 5 days prior to this. I could probably get a larger 12V battery like a 22AH, but I have to find room in the car for a larger battery.
Wiring up the 12V battery such that it gets charged from the main pack even with the ignition off could solve this problem, but then your main pack would drain more quickly and affect range.
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Re: EV power up

Postby Bblocher » Tue Nov 06, 2012 7:08 am

I have a secondary power converter for this purpose. As long as I'm plugged in my 12v system is also charged.
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Re: EV power up

Postby Electric » Sat Dec 15, 2012 11:29 am

I like Brian's solution to have a small inverter (ac to dc) powered from the wall ac when plugged in to charge and top off the 12v system. Or to have a larger capacity 12v battery that could last up to 4 weeks of parking. When I had my car painted in the shop, three weeks later, the ev display gauge lost power (no display on the gauge). I though my guage was broken, so I turned on the key ignition to find out what's going on. The Solid state relay turned on the dc-dc converter and started charging the 12v. The ev display powered up but the soc reset to 100%. I realized that my 12v (AGM 24Ah) battery was almost dead. The 12V battery probably had some residual voltage, which was too low to power the ev display but enough to activate the solid state relay.
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Re: EV power up

Postby chuck_b24 » Thu Feb 07, 2013 10:02 am

How about a battery disconnect?? like a boat or RV??? they are cheap & EASY

kchiang wrote:I just got back from a 10 day vacation to a dead 12V auxiliary battery. The 12V that I use is a sealed lead acid AGM 7AH. My MR2 EV is wired such that the DC-DC converter only charges the 12V battery from the main 144V traction pack when the ignition is turned on. As Jack pointed out, if the 12V battery dies, then I will not be able to turn on the ignition to start charging the 12V battery. This worries me on those long away trips if I ever need to park my car at the airport. The longest time I've been parked without a dead battery was 5 days prior to this. I could probably get a larger 12V battery like a 22AH, but I have to find room in the car for a larger battery.
Wiring up the 12V battery such that it gets charged from the main pack even with the ignition off could solve this problem, but then your main pack would drain more quickly and affect range.
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EV power drains

Postby mizlplix » Sat Feb 09, 2013 1:43 am

__________________________________________________________________________________________________________________________________________
System drains

There are several small systems that must stay on during the
time your EV is parked. Any good (accurate) SOC meter or
BMS will be just two of them.

Like many owners, I too am not comfortable leaving my
EV plugged in while I am away, especially if it is parked
inside my home in the garage.

The only real compromise is to buy a small battery tender
like from NAPA and install it on the AUX 12 VDC battery.
It draws less than 1 Amp from your home electrical service
and keeps the aux battery topped off and the car alive.

It will not drain the traction pack or be as dangerous
as leaving the main pack charger plugged in.

They typically cost around $30 USD.

Miz
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Re: EV power up

Postby kchiang » Sat Feb 09, 2013 8:40 am

Thanks for the suggestions guys.
The battery problem is getting worse, after a 3 day weekend, the battery won't turn the ignition on Monday last weekend. I think the battery is too old (1.5 years of use). I am using a TR-22 Tempest battery http://www.batteryspec.com/cgi-bin/cart.cgi?action=link&product=68. I am doing a discharge cycle on it to see how much actual charge is left. In the meantime, I've purchased a new battery TD-22 http://www.batteryspec.com/cgi-bin/cart.cgi?action=link&product=217
Cost $79.
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Re: EV power up

Postby kchiang » Sat May 25, 2013 10:27 am

Wow, time flies, I finally replaced my 12V battery yesterday. I also measured the parked amp draw from the 12V system. It was 0.085amps.

http://blog.mr2ev.com/?p=1009
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Re: EV power up

Postby Alain riaud » Wed Jun 05, 2013 12:52 pm

12V battery health is the first thing to check when problems arise.
On my Peugeot Partner there is a DC-DC converter taking care of the 12V battery off the main traction battery pack.
The car can stay unused for months.
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Re: EV power up

Postby garver71 » Mon Aug 19, 2013 2:21 pm

I had this problem once when I left the headlights on. It drained the 12V battery. My solution was to make sure the car was out of gear, then turn the key on and manually push in the contactor. Some contactors cannot be manually pulled in so a temporary jumper should work in this case. Remove the jumper once the contactor is pulled in and the DC/DC is going. If you have 2 contactors, then probably only 1 is wired to get the DC/DC converter going. The other contactor will also pull in. If you have this problem often, you might want to make a connector so you can plug in the DC/DC directly to the pack voltage- with a fuse of course.
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