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Old 09-10-2018, 11:01 AM   #1 (permalink)
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Default 12 V battery discharge rate

In one weeks time my 12V battery discharges from 12.82V to 12.52V. I then recharge it because it will continue to discharge at the same rate.
Was wondering if this is a normal parasitic discharge for a one year old battery?
Also does the HV battery cooling system use the 12V battery or the HV battery.
My garage gets hot in the summer and I presume the cooling system automatically keeps the HV battery temperature below the max. allowable 86 degrees.
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Old 09-10-2018, 04:02 PM   #2 (permalink)
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Three options, do either of the following



1. When storing the car unplug the black main 12v connector


2. Connect a battery tender


3. Park the vehicle outside so that the solar panel can top off the 12v


You could also have a bad 12v battery, you should get it checked by whomever you bought it from to see if it is bad.





Are you on 520 or 535?
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Old 09-10-2018, 04:28 PM   #3 (permalink)
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The Karma draws around 45 to 60 MA when sleeping that’s one of the reason they go dead in two weeks .
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Old 09-11-2018, 09:09 AM   #4 (permalink)
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Originally Posted by Harleyguy View Post
The Karma draws around 45 to 60 MA when sleeping thatís one of the reason they go dead in two weeks .

I presume you mean 45-60 MA per day?
My battery draws down by 45 MA per day which is at your low end!
I feel better now!!

No one answered the other question I had as to whether the HV cooling system is operated by the 12V battery or the HV battery. This could cause drawdown if itís the 12V system and the cooling system comes on to cool the HV battery when the car is parked.
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Old 09-11-2018, 11:16 AM   #5 (permalink)
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Originally Posted by Stephenhale View Post
I presume you mean 45-60 MA per day?
My battery draws down by 45 MA per day which is at your low end!
I feel better now!!

No one answered the other question I had as to whether the HV cooling system is operated by the 12V battery or the HV battery. This could cause drawdown if itís the 12V system and the cooling system comes on to cool the HV battery when the car is parked.
The cooling pump runs only while the car is charging the HV battery it keeps the OBCM cool while it's charging. Thats the only pump that will run while the car isn't being driven .
The draw is a constant draw while the car is off not per day. If you use an amp meter you can read that I use an inductive one made for low draws.
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Old 09-17-2018, 06:23 PM   #6 (permalink)
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Amperes (or milliamperes) is a measure of current flow and hence is a "speed", like mph. You would not say "I go 45 mph per day", so don't say "45 mA per day" either. Battery capacities are measured in amp-hours (among other things), if you have a 100 amp-hour (Ah) battery, it can (provided other things hold) put out 100 amps for 1 hour, or 1 amp for 100 hours.


The AGM battery in a Karma should probably have at least 60 to 100 Ah (Harleyguy will probably know the actual capacity). At 60 mA draw, 24 hours = 24 x 60 = 1440 mAh = 1.44 Ah. In 7 days that's 10 aH or 10% of the capacity of a 100 Ah battery, which means you should be able to go about 10 weeks (2.5 months) before completely draining it.


AGM batteries are better about being completely drained ("deep cycled") than plain 12V batteries but it's still a bad idea to do that if you can avoid it.
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Old 09-19-2018, 02:52 PM   #7 (permalink)
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Originally Posted by PowerSource View Post
Three options, do either of the following



1. When storing the car unplug the black main 12v connector


2. Connect a battery tender


3. Park the vehicle outside so that the solar panel can top off the 12v


You could also have a bad 12v battery, you should get it checked by whomever you bought it from to see if it is bad.


Are you on 520 or 535?
The key question, which I asked about before but didn't see a reply, was how long the 12V battery will last relying on the trickle charging capabilities of the 535 software version (assuming a full HV battery at the outset). Hopefully a lot longer than the two weeks described above!

Anyone done a test?

Simon
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Old 09-19-2018, 04:16 PM   #8 (permalink)
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Originally Posted by ct-fiskerbuzz View Post
Amperes (or milliamperes) is a measure of current flow and hence is a "speed", like mph. You would not say "I go 45 mph per day", so don't say "45 mA per day" either. Battery capacities are measured in amp-hours (among other things), if you have a 100 amp-hour (Ah) battery, it can (provided other things hold) put out 100 amps for 1 hour, or 1 amp for 100 hours.


The AGM battery in a Karma should probably have at least 60 to 100 Ah (Harleyguy will probably know the actual capacity). At 60 mA draw, 24 hours = 24 x 60 = 1440 mAh = 1.44 Ah. In 7 days that's 10 aH or 10% of the capacity of a 100 Ah battery, which means you should be able to go about 10 weeks (2.5 months) before completely draining it.


AGM batteries are better about being completely drained ("deep cycled") than plain 12V batteries but it's still a bad idea to do that if you can avoid it.
In real world you wouldnít want the battery to drop below 50%of its capacity. So I would change your figure to 5 weeks at the most plus Iíve seen the draw anywhere from 45 to 60 and I would need to check the reserve capacity of the battery I think itís alot less then 100 amps .
All I know anything past two weeks with a Karma your skating on thin ice . Things on paper are a lot different then real world conditions. I have the same argument with the engineers I deal with for any car line .
I call them up and they say thatís impossible thatís because they did the calculations on paper and have no idea what the real world is like. They donít take into consideration climate how to car is driven or stored etc .
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Old 09-19-2018, 05:11 PM   #9 (permalink)
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Originally Posted by shrowell View Post
The key question, which I asked about before but didn't see a reply, was how long the 12V battery will last relying on the trickle charging capabilities of the 535 software version (assuming a full HV battery at the outset). Hopefully a lot longer than the two weeks described above!

Anyone done a test?

Simon
Theoretically it would keep draining the HV battery until the HV battery goes to 15% which on paper would be a very long time. This is not taking into consideration other losses just the power factor of top off.

It would take 15 months or so, on paper, to deplete the Hv pack with shallow depth 12v discharge top offs.

Your contactors will likely fail shortly after since they are rated for a certain amount of cycles. The constant cycling will shorten its lifespan.

Last edited by PowerSource; 09-19-2018 at 05:14 PM.
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Old 09-20-2018, 05:04 PM   #10 (permalink)
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Originally Posted by PowerSource View Post
Theoretically it would keep draining the HV battery until the HV battery goes to 15% which on paper would be a very long time. This is not taking into consideration other losses just the power factor of top off.

It would take 15 months or so, on paper, to deplete the Hv pack with shallow depth 12v discharge top offs.

Your contactors will likely fail shortly after since they are rated for a certain amount of cycles. The constant cycling will shorten its lifespan.
Thank you for this. However, even though trickle charger with the 535 software could keep the 12V battery maintained for several months, the recommendation is to pull the 'big black plug' and maintain the 12V battery on a charger if I were to leave the car for more than a couple of weeks. Yes?

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