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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sat Oct 26, 2019 1:07 am 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 28
Hi, I should probably be in a different thread, but here is the scenario I need to get specs for:
Let's assume I'll have a 1kW (compressors) load on my 2kW 12VDC to 120VAC converter.
That converter will be hooked up to a 12VDC car battery that is being charged by the RAV4.

I plan to turn on my RAV4 with its battery AND an external battery, and once on, switch out the RAV4 12V battery.
The question comes basically down to what are the current specs for the external battery and the RAV4 12V battery charged, especially the continuous current (I would like to have perhaps 90A) ... but can also reduce the load, depending on that spec ...

The external Lead Acid battery I have is an Interstate MT24F, CCA 600, CA750, RC110, and I doubt it can deliver 1kW, but perhaps with the help of the RAV4 charger ...

Sorry I was unclear,
Ferenc

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sat Oct 26, 2019 5:55 am 
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Joined: Mon Feb 24, 2014 8:51 pm
Posts: 628
Just use some jump cables to the second battery and let it rip. I believe the RAV can supply up to 80 amps at 14 volts or 1120 watts. If the inverter cuts out for low voltage just reduce the load or the duty cycle.


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sat Oct 26, 2019 1:43 pm 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 28
smkettner wrote:
Just use some jump cables to the second battery and let it rip. I believe the RAV can supply up to 80 amps at 14 volts or 1120 watts. If the inverter cuts out for low voltage just reduce the load or the duty cycle.

Thanks, the previous time I just used the RAV4 12V battery cables to charge my external battery, but it would be good to confirm your spec, as it'd be more convenient, if I did not to have to worry about damaging the external battery or my EV!

My dc-ac inverter will shut auto shutoff if V(in) is not within range, but I don't know if the RAV4 will protect itself against an overload.

Another outage this afternoon ... with my enphase (solar panel) microinverters searching for the 60Hz grid-tie. it's always next year with those guys ...
Ferenc
Ad on:
I found this on a web search (caveat emptor) at hobbyprojects.com, but it does not provide a discharge curve with safety (:

Cold cranking amps (CCA) is a measurement of the number of amps a battery can deliver at 0 ° F for 30 seconds and not drop below 7.2 volts. So a high CCA battery rating is good especially in cold weather.

CA is cranking amps measured at 32 degrees F. This rating is also called marine cranking amps (MCA). Hot cranking amps (HCA) is seldom used any longer but is measured at 80 ° F.

Reserve Capacity (RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.

An amp hour (AH) is a rating usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours, 20 amps for 5 hours, etc.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sun Oct 27, 2019 9:52 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4113
Location: San Diego
The output of the Tesla supplied DC to DC converter used in RAV4 EV is 100 amps. Obviously, there’s a little power being consumed by the car, even if parked and the air conditioner or heating is turned off, so the net output may be 90-95 amps.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sun Oct 27, 2019 10:08 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4113
Location: San Diego
miimura wrote:
The problem with most flooded lead acid batteries is that the RAV4 EV drains them slowly while parked and if you don't drive the car every day, or especially a week or more at a time, it will deep cycle it and it will die quickly. If you drive it every day and put it on a tender whenever you don't, a traditional flooded maintenance free battery should last a normal 4 to 5 years.


For traditional flooded batteries, they certainly should be “deep cycle”.

Quote:
I have not found a perfect set-and-forget 12V battery suggestion for the RAV4 EV that is good for all owners. Even the Valence Lithium battery has a weird BMS condition that requires resetting.


The Valence can be modified to stop the BMS from switching the battery off-line with a surge from the DC2DC. That battery is probably the closest to “set it and forget it”, since it:

1) “Deep cycle” is exactly where a properly designed lithium 12 volt battery should do best. Most lithium cells last longest when cool and kept between about 3.4 volts and 3.8 volts per cell. Using a 4 Series configuration, that’s 13.6 volts up to 14.5 volts.... exactly where we expect the DC2DC to maintain the voltage. That same battery would be able to handle up to 4.2 volts per cell multiplied by 4S equals 16.8 volts, well above “normal” DC2DC voltage output. It’s as perfect as we can hope for.

2) Has no gassing (well, unless the voltage or temps were exceeded, which I don’t expect with normal RAV4 operation... excess amps should blow a fuse)

3) Would allow the RAV4 EV to be operated “continuously”

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1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Mon Oct 28, 2019 1:20 am 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 28
TonyWilliams wrote:
The output of the Tesla supplied DC to DC converter used in RAV4 EV is 100 amps. Obviously, there’s a little power being consumed by the car, even if parked and the air conditioner or heating is turned off, so the net output may be 90-95 amps.

Thanks - I saw a 200A fuse on the positive terminal.
I measured the voltage across the battery with car on and it was the same 14.3v as when I had the external load hooked up at the same time. So, why would one need a disconnect?
Is the battery being charged with constant voltage and variable current?
Failing to see the big picture...
Ferenc

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Mon Oct 28, 2019 7:51 pm 
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Joined: Mon Apr 01, 2013 11:42 pm
Posts: 313
Location: San Diego, CA, USA
ferenc wrote:
Thanks - I saw a 200A fuse on the positive terminal.
I measured the voltage across the battery with car on and it was the same 14.3v as when I had the external load hooked up at the same time. So, why would one need a disconnect?
Is the battery being charged with constant voltage and variable current?
Failing to see the big picture...
Ferenc

Miimura needs the disconnect because he has an AGM battery, which overheats when continuously charged for a long period at the high voltage the RAV4 uses. If he left the RAV on for a few days to run his fridge, he'd fry the battery. With a different battery, a disconnect probably isn't needed.

Also, when you have a Jdemo installed, Tony puts in a disconnect so that you can power cycle the Jdemo if it gets really hosed up.


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Mon Oct 28, 2019 9:44 pm 
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Joined: Mon Aug 07, 2017 4:55 pm
Posts: 194
Location: Duvall, Wash.
To be fair, 14.3v isn't considered high for FLA batteries, but it is for AGM, which perfer ~13.5v for warmer and longer-term charge voltage.

Yeah, days at 14.3v with AGM probably isn't going to work well. miimura's workaround is reasonable, I think.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Tue Oct 29, 2019 1:39 am 
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Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1824
Location: Los Altos, CA
davewill wrote:
ferenc wrote:
Thanks - I saw a 200A fuse on the positive terminal.
I measured the voltage across the battery with car on and it was the same 14.3v as when I had the external load hooked up at the same time. So, why would one need a disconnect?
Is the battery being charged with constant voltage and variable current?
Failing to see the big picture...
Ferenc

Miimura needs the disconnect because he has an AGM battery, which overheats when continuously charged for a long period at the high voltage the RAV4 uses. If he left the RAV on for a few days to run his fridge, he'd fry the battery. With a different battery, a disconnect probably isn't needed.

Also, when you have a Jdemo installed, Tony puts in a disconnect so that you can power cycle the Jdemo if it gets really hosed up.

I also don't have the updated harness on my early JdeMO unit, so I would use the 12V disconnect or pull the charger fuse if the JdeMO went wonky on me.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sun Nov 03, 2019 10:52 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4113
Location: San Diego
I have a new “favorite” 12 volt battery for RAV4 EV:

COSTCO # 850952
$87.99

Built by Interstate
Model 27-DC

Group 27 size (slightly too long for existing box, and the positive and negative post are reversed)

95 Amp Hours

Deep Cycle

Flooded Lead Acid

This battery should handle all the RAV4 EV requirements:

1) Relatively cheap, so it could be more readily replaced prior to failure for those thrifty owners that think they are saving money by waiting for the battery to outright fail and cause numerous error codes that can only be cleared by the Toyota dealer.

2) It should last a ridiculously long time (5 years plus, except extreme hot environments)

3) Will readily handle 14.5 volts charging for weeks on end, if you want to leave the car on to cool the battery, or provide Vehicle 2 Home power (V2H)

4) The car can be parked for weeks while OFF / not charging without damaging the 12 volt, or killing it (about 3 times the amp-hour capacity of the original Toyota Group 35 battery)

5) Deep cycle is needed on EVs, which the AGM should also be able to do

6) Available at Costco, or an Interstate battery dealer

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Tony Williams
QC Charge
1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
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