Use of Capacitor to save 12V battery?

[Paulb55]

Recently added a Key 500.1 and might end up adding a 200 as well. I know that capacitors got a bad rap from crappy products in the late 90's...but with that tiny 12V battery has anyone noticed or an impact on longevity after adding amps? I'm not trying to overthink things, but would rather drop $125 on a small capacitor than $200 on a new battery.

I don't fully understand how the 12V gets charged and I live in SFL where batteries get eaten by the heat frequently

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[Adventureboy]

What are you trying to accomplish? A capacitor can provide power bursts that might be beneficial for large audio changes like subwoofer amplifiers that can have heavy intermittent draws, but for constant draws, it wouldn't help the 12v much.

Here are the 12v charging scenarios.

1. LVB charges when the truck is ON (it takes about an hour if the LVB is low - For ON durations less than about 15-20 minutes, you may end up with lower LVB SOC than you started with 30 minutes after shutdown.)
2. LVB is maintained when Accessory is ON (lower than charging voltage when ON, but keeps LVB from getting drained and actually does charge it a bit)
3. LVB charges when HVB is actively charging (both DCFC and L1/L2)
4. LVB will be charged by the HVB if the level of the LVB falls below a setpoint somewhere between 40-50% SOC
5. The truck does NOT charge the LVB while plugged into L1/L2 if the HVB is already at target HVB SOC unless 4) kicks in.

 

[UtahRookie]

What are you trying to accomplish? A capacitor can provide power bursts that might be beneficial for large audio changes like subwoofer amplifiers that can have heavy intermittent draws, but for constant draws, it wouldn't help the 12v much.

Here are the 12v charging scenarios.

1. LVB charges when the truck is ON (it takes about an hour if the LVB is low - For ON durations less than about 15-20 minutes, you may end up with lower LVB SOC than you started with 30 minutes after shutdown.)
2. LVB is maintained when Accessory is ON (lower than charging voltage when ON, but keeps LVB from getting drained and actually does charge it a bit)
3. LVB charges when HVB is actively charging (both DCFC and L1/L2)
4. LVB will be charged by the HVB if the level of the LVB falls below a setpoint somewhere between 40-50% SOC
5. The truck does NOT charge the LVB while plugged into L1/L2 if the HVB is already at target HVB SOC unless 4) kicks in.

Great information....thanks for sharing!

 

[astrand1]

What is a “key 500.1” ?

 

[Paulb55]

What are you trying to accomplish? A capacitor can provide power bursts that might be beneficial for large audio changes like subwoofer amplifiers that can have heavy intermittent draws, but for constant draws, it wouldn't help the 12v much.

Here are the 12v charging scenarios.

1. LVB charges when the truck is ON (it takes about an hour if the LVB is low - For ON durations less than about 15-20 minutes, you may end up with lower LVB SOC than you started with 30 minutes after shutdown.)
2. LVB is maintained when Accessory is ON (lower than charging voltage when ON, but keeps LVB from getting drained and actually does charge it a bit)
3. LVB charges when HVB is actively charging (both DCFC and L1/L2)
4. LVB will be charged by the HVB if the level of the LVB falls below a setpoint somewhere between 40-50% SOC
5. The truck does NOT charge the LVB while plugged into L1/L2 if the HVB is already at target HVB SOC unless 4) kicks in.

VERY HELPFUL! Thank you.

I am just wiring up the amp and had seen 2 or 3 posts about dead 12V batteries so my brain started spinning thinking if a cap would just help reduce overall draw for those shorter trips.
Your explanation saved me ~$100plus materials and lots of SFL sweat.

 

[Paulb55]

What is a “key 500.1” ?

Its a Kicker amp for a sub. It also has the ability to correct the audio signal for the B&O sub when upgrading. If you didnt use a kicker amp you would use a KeyLOC or similar items

 

[astrand1]

I thought it was an amp but then you were talking about a capacitor. So that was kind of confusing.

 

[helodude]

What should the maximum current in amps be for an amplifier powered from the LVB?

Is there any way to tie into the HVB and use a voltage converter to drop the voltage?

 

[cwstnsko]

...
Here are the 12v charging scenarios.

1. LVB charges when the truck is ON (it takes about an hour if the LVB is low - For ON durations less than about 15-20 minutes, you may end up with lower LVB SOC than you started with 30 minutes after shutdown.)
2. LVB is maintained when Accessory is ON (lower than charging voltage when ON, but keeps LVB from getting drained and actually does charge it a bit)
3. LVB charges when HVB is actively charging (both DCFC and L1/L2)
4. LVB will be charged by the HVB if the level of the LVB falls below a setpoint somewhere between 40-50% SOC
5. The truck does NOT charge the LVB while plugged into L1/L2 if the HVB is already at target HVB SOC unless 4) kicks in.

This behavior is one reason that I choose to charge the truck at a lower amperage. I don't drive a lot each day and the longer the truck spends actively charging, the more time it spends maintaining the SOC of the 12V battery. If I charged at 80a, the HVB would hit the target SOC so quickly that the LVB would keep getting run down by my short trip driving.

 

[Adventureboy]

This behavior is one reason that I choose to charge the truck at a lower amperage. I don't drive a lot each day and the longer the truck spends actively charging, the more time it spends maintaining the SOC of the 12V battery. If I charged at 80a, the HVB would hit the target SOC so quickly that the LVB would keep getting run down by my short trip driving.

Yes, this is a very good technique that I use too. I generally charge at 32 amps, which usually gives me several hours of charging, and I even drop it down as low as 6 amps on really light drive days. I kick it up to 48 amps only when needed.

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