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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Oct 17, 2019 10:44 pm 
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Joined: Mon Apr 01, 2013 11:42 pm
Posts: 313
Location: San Diego, CA, USA
TonyWilliams wrote:
You can use a simple M8 wing nut. Every JdeMO™ installation includes this. We would be happy to send you one with a flat washer.

https://shop.quickchargepower.com/12-Vo ... ONNECT.htm

The Bosch AGM battery has been a disappointment over the years. Yes, you want a Group 24F or bigger battery, and you want the largest amp hour rating (not cranking amps... we don’t need that). It also should be a deep cycle type battery. AGM would be a plus.

But, the Bosch batteries fail too often, and overheat too much.

Any updated recommendation then? My Interstate battery just turned 4 yo and I was figuring on replacing it proactively. Why would a different AGM battery work better than the Bosch?


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 18, 2019 5:30 am 
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Joined: Thu Jan 17, 2013 11:13 pm
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Location: Los Altos, CA
davewill wrote:
TonyWilliams wrote:
The Bosch AGM battery has been a disappointment over the years. Yes, you want a Group 24F or bigger battery, and you want the largest amp hour rating (not cranking amps... we don’t need that). It also should be a deep cycle type battery. AGM would be a plus.

But, the Bosch batteries fail too often, and overheat too much.

Any updated recommendation then? My Interstate battery just turned 4 yo and I was figuring on replacing it proactively. Why would a different AGM battery work better than the Bosch?

In theory, AGM batteries will overheat with prolonged float charging at 14.4V that the Tesla DC-DC in the RAV4 EV is programmed for. Bulk charging at that voltage is fine, but float should be reduced to 13.8V. If you check a Tesla car, I'm pretty sure they float the 12V battery at 13.8V. It would be really great if we could reprogram the DC-DC for 13.8V when an AGM battery is installed. I don't know if such a thing is possible. I will probably go back to a standard maintenance free flooded battery when I replace the Bosch AGM. It has overheated and vented on me twice already.

https://batteryuniversity.com/learn/art ... ss_mat_agm

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 18, 2019 4:45 pm 
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Joined: Mon Aug 07, 2017 4:55 pm
Posts: 194
Location: Duvall, Wash.
[grins]

Come around to my my way of thinking about Bosch, eh?

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2014 Rav4 EV, Shoreline Blue Pearl, #2609, first use 04Jun2014, 49k miles (Aug2017), OpenEVSE 40A. First DU replacement May2018 59k.
2018 Model 3 LR AWD, blue. 9.6kw solar
1999 E300 on B100 (sold Sep2018)
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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 18, 2019 5:50 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4113
Location: San Diego
This battery has even higher amp Hour rating of 75 (versus 60 for the Bosch AGM).

Group 24F

75 ah

Flooded lead acid

$136.95

https://www.interstatebatteries.com/products/mtp-24f

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 18, 2019 9:04 pm 
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Joined: Mon Aug 07, 2017 4:55 pm
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Location: Duvall, Wash.
The Interstate MTP series was my go-to FLA battery for two decades. I was routinely seeing 8+ years life from them. Not cheap, but worth it.

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Al Savage
2014 Rav4 EV, Shoreline Blue Pearl, #2609, first use 04Jun2014, 49k miles (Aug2017), OpenEVSE 40A. First DU replacement May2018 59k.
2018 Model 3 LR AWD, blue. 9.6kw solar
1999 E300 on B100 (sold Sep2018)
http://nissandiesel.dyndns.org


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sat Oct 19, 2019 2:48 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4113
Location: San Diego
asavage wrote:
The Interstate MTP series was my go-to FLA battery for two decades. I was routinely seeing 8+ years life from them. Not cheap, but worth it.


We don’t have any idea how this battery may handle the RAV4 EV, and it’s not “deep cycle”, so there may be an even better battery.

The one huge advantage of a lithium 12 volt battery is that it can easily handle 16 volts (4 cells in series * 4.2 volts max).

And it will last forever at 13.5 - 14.5 volts. The only thing that would kill it is heat.

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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
Hours M-F, 9-5 Pacific Time


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sat Oct 19, 2019 3:59 pm 
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Joined: Mon Aug 07, 2017 4:55 pm
Posts: 194
Location: Duvall, Wash.
Is the reason the Bosch AGM (and, by extension, any lead-acid vehicle battery, including the Toyota-branded one) is not holding up well, known?

  • Long-term overvoltage (ie over 15.1v for long periods of time)?
  • Deep cycling?

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Regards,
Al Savage
2014 Rav4 EV, Shoreline Blue Pearl, #2609, first use 04Jun2014, 49k miles (Aug2017), OpenEVSE 40A. First DU replacement May2018 59k.
2018 Model 3 LR AWD, blue. 9.6kw solar
1999 E300 on B100 (sold Sep2018)
http://nissandiesel.dyndns.org


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Mon Oct 21, 2019 7:05 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
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Location: Los Altos, CA
asavage wrote:
Is the reason the Bosch AGM (and, by extension, any lead-acid vehicle battery, including the Toyota-branded one) is not holding up well, known?

  • Long-term overvoltage (ie over 15.1v for long periods of time)?
  • Deep cycling?

IMHO, the problem with AGM in the RAV4 EV is that it float charges it at too high a voltage. If you are driving and charging back to back without letting it rest and discharge a little, it will overheat. I don't see why a different brand AGM would be any different than the Bosch.

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.

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.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 25, 2019 4:57 am 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 28
so, what is the rav4 charging current spec for the 12v battery?
also, how does one know the steady state load/discharge current rating of a battery? cranking rating may imply short time (30 secs?), perhaps ...
getting ready for sunday,
ferenc

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Fri Oct 25, 2019 7:10 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
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Location: Los Altos, CA
ferenc wrote:
so, what is the rav4 charging current spec for the 12v battery?
also, how does one know the steady state load/discharge current rating of a battery? cranking rating may imply short time (30 secs?), perhaps ...
getting ready for sunday,
ferenc

When you're buying a battery there are only a few things that inform the decision.
1. Size - The factory battery is Group 35 and is smaller than the Group 24F that will fit the battery tray. The battery group size includes the physical dimensions and the type and location of the battery connections. For example, the 24 and 24F have the + and - post locations reversed.
2. Type - flooded, flooded maintenance free, AGM, lead acid gel, etc.
3. Cold Cranking Amps (CCA) - This is not relevant to the RAV4 EV because it doesn't need a lot of current to start the car.
4. Capacity - Amp-hour capacity over different durations. Typical capacity is the Ah for 20h discharge. Sometimes you might see 2h discharge too. This can also be expressed as a running time at a certain amperage. For example, a Interstate MTP battery in the H6 size has a 20h capacity of 70Ah and 115 minutes @ 25A while the larger H8 size has 100Ah and 175 min @ 25A. The same MTP series has 100 min for Group 35 and 130 min for Group 24F. So, roughly speaking, you get 30% more capacity for the larger battery that fits in the RAV4 EV.

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