Replacing the 12V aux Battery

[scotty2541]

I've used Ebay with mixed results. But I see your point about a $24 part being worth it for a two year life cycle.

I'd like to see how "Perrin21" worked out with his LiPo battery now a year later.

 

[dpeilow]

@Perrin21 ?

 

[Perrin21]

@Perrin21 ?

Over a year now I think. The shorai I used has been faultless.

 

[glight2000]

Do you think the

Over a year now I think. The shorai I used has been faultless.

I'd be grateful for anyone's thoughts as to whether the Shorai would be more robust to the hungrier power needs of an amped audio system?

 

[ML Auto]

Do you think the


I'd be grateful for anyone's thoughts as to whether the Shorai would be more robust to the hungrier power needs of an amped audio system?

Just connect the amp to the APS output under the dash- it puts out 120 amps. The battery is just for secondary backup systems.

 

[glight2000]

Just connect the amp to the APS output under the dash- it puts out 120 amps. The battery is just for secondary backup systems.

I'm not sure how the installer connected to the power, but I get messages on the VDS after about 30 min of pumping bass and cruising.

I've seen some posts that have implied some owners have installed terminals on the 12v battery under the right front wheel to trickle charge the 12v. Do you think swapping the 12v for LED and adding cables for weekly trickle charging would work or is that too absurd to even contemplate?

See mention here, 5th from bottom of page by n2mb_racing:
Replacing the 12V aux Battery

 

[ML Auto]

The 12V battery only receives 12.8V from the switchback to keep it charged. It is not connected to the 13.5V 120A APS circuit. They probably just got power from the 12V battery. Once the charge goes down you get your errors. You really need to get that rewired or you could blow your $1000 switchpack. The 120A terminal you need to use is under the dash behind the fuse box.

 

[glight2000]

The 12V battery only receives 12.8V from the switchback to keep it charged. It is not connected to the 13.5V 120A APS circuit. They probably just got power from the 12V battery. Once the charge goes down you get your errors. You really need to get that rewired or you could blow your $1000 switchpack. The 120A terminal you need to use is under the dash behind the fuse box.

THANK YOU, MLAUTO! I will get the car back to the installer on Tuesday.

 

[cswolfe]

great thread. thank you.

 

[n2mb_racing]

How about one of these higher quality Li-ion batteries? I wonder if they have balance charging built-in?
Braille Battery USA &nbsp&nbsp&nbsp&nbsp Lighter • Stronger • Faster -

 

[n2mb_racing]

Good to know. Can you power other things from the APS circuit, like an AC inverter?

The 12V battery only receives 12.8V from the switchback to keep it charged. It is not connected to the 13.5V 120A APS circuit. They probably just got power from the 12V battery. Once the charge goes down you get your errors. You really need to get that rewired or you could blow your $1000 switchpack. The 120A terminal you need to use is under the dash behind the fuse box.

 

[gregd]

Isn't 12.8v a bit low to keep a 12v lead acid battery happy? I thought a proper float charger kept things at least at 13.1 or maybe even a bit higher. Is that why we keep needing to replace these things every few years?

 

[ML Auto]

Isn't 12.8v a bit low to keep a 12v lead acid battery happy? I thought a proper float charger kept things at least at 13.1 or maybe even a bit higher. Is that why we keep needing to replace these things every few years?

12.7V is considered fully charged, so as long as it remains there, is should not cause any problems. Charging it with 12.8V would take a while, but that circuit powers very little, and doesn't require much charging. Those small powersports batteries never seem to last more than a few years no mater what you use them in.

Good to know. Can you power other things from the APS circuit, like an AC inverter?

The car doesn't have any thing other than basic electrical accessories, so with 120A there is a lot to spare. There is a separate 35A power to the PEM, so the big items are the HVAC fan, wipers, headlights and seat heaters-probably less than 50A together. So unless you are driving in the rain on a cold night honking the horn while rolling down the windows, I can't see using even half of the APS output. However the fuse for the APS is inside the ESS, So there is a lot of labor if you blow that $10 fuse.

 

[glight2000]

The car doesn't have any thing other than basic electrical accessories, so with 120A there is a lot to spare. There is a separate 35A power to the PEM, so the big items are the HVAC fan, wipers, headlights and seat heaters-probably less than 50A together. So unless you are driving in the rain on a cold night honking the horn while rolling down the windows, I can't see using even half of the APS output. However the fuse for the APS is inside the ESS, So there is a lot of labor if you blow that $10 fuse.

I still haven't made it back to the audio shop. As I'm sure you can imagine, they do not know anything about roadsters and I don't know what they actually did to install the audio system. I know even less than the shop about the electric power system. I just know that I now have a low aux battery, aux batteries don't last long at baseline, and maybe this just pushed a dying battery over the edge.

I'd appreciate TMC guidance on the following options, asking for forgiveness in advance for my ignorance despite scouring the forums:
1) replace aux battery with standard lead acid and see how long it lasts
2) replace with lithium battery and see how long it lasts
3) replace with lithium AND and cables have cables snaked up under hood for periodic trickle charging using the special charger that comes with lithium battery.

Next, if they wired audio system to 12v, should I have them rewire to APS fuse?

 

[ML Auto]

I would just replace the 12V battery with a cheap Ebay one. Mine has 18 months and 20K miles on it already. Personally, I don't think trying to make a lithium one work is worth the hassle or expense.

Definitely make sure the amp is wired to the APS junction box under the right side dash. Anything else is asking for trouble.

 

[n2mb_racing]

However the fuse for the APS is inside the ESS, So there is a lot of labor if you blow that $10 fuse.

Is there a spare circuit open in the fusebox? Could he add a high-amperage fuse, like 50A and put the amp there? Or in my case, I'd be interested in having provisions for an AC inverter, but I'd want to make sure there is an easily replaceable fuse that blows before the ESS fuse.

 

[gregd]

Is there a spare circuit open in the fusebox? Could he add a high-amperage fuse, like 50A and put the amp there? Or in my case, I'd be interested in having provisions for an AC inverter, but I'd want to make sure there is an easily replaceable fuse that blows before the ESS fuse.

I was thinking the same thing, but didn't I read earlier (different thread) that the 12V system is pretty fragile, and not to try to get much out of it? We were warned, for example, not to use tire pumps that draw more than 8A from the Accessory outlet, for fear of blowing the 12V system feed... I'm surprised (and delighted!) that there's really more than a kw of power available. Really? Can't both be true; what am I missing?

 

[ElectricLove]

Lithium is better!

If you spec it right you will be able to reduce the "stress" on the DC/DC dramatically, you can stuff a good bit more energy into that small space and in doing so maintain a much larger buffer which can reduce how often the APS is cycling...

However, the system does maintain the battery at "only" ~12.8V, this isn't high enough for a Lithium battery, it will still work but it isn't ideal and you won't be realizing a lot of the benefits (capacity), 12.8V for many Lithium batteries (depending on chemistry) is only 40-60% charged... It'll still be lighter and it won't necessarily "fail" but it also won't be as good as it could/should be...

Like with any battery, larger capacity = less stress on the cells during use = longer life!

As a word of advice/caution about Shorai and many other Lithium battery builders; they use the term "Pb equivalent" or "Lead-acid equivalent" to describe the BURST rate of the cells, it doesn't give you a genuine grasp on actual capacity and in an Electric Vehicle the BURST rate is relatively irrelevant, the part that matters more is the actual capacity!

 

[ElectricLove]

How about one of these higher quality Li-ion batteries? I wonder if they have balance charging built-in?
Braille Battery USA &nbsp&nbsp&nbsp&nbsp Lighter • Stronger • Faster -

The Braille G20 is a hot battery for this car!

There are others available and even some custom lithium battery builders out there who may be able to come up with something for this vehicle... It's a limited market though so don't expect a company to just develop something, if you want it you gotta go find it!

I am actually part of launching a custom battery building business right now and would be willing to do the design/spec/build for a Roadster Lithium if a few people are interested???

 

[glight2000]

I got tired of living with a dead 12v so I went to a motorcycle shop and picked up a battery that would fit. It happens to be lithium. I wanted a larger capacity to handle the audio system. So far, it's all working well with sound and door locking/unlocking. Hopefully I won't have problems down the road. Thanks to ElectricLove and others for advice

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