Will my stock 105 amp alternator be able to handle 700-750 watts rms


Mcdaddy7777

CarAudio.com Newbie
Oct 6, 2018
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Car audio noob here.

I am hoping to install a 700-750 watt rms system in my Honda Fit 2016 EX.


I've asked multiple different auto parts stores and car audio stores, and I get different answers. Some say yes, I should upgrade my alternator, and others say I should not worry about it. I spoke with a rep at Crutchfield, and he didn't think I should upgrade the alternator, but did believe a 2nd battery would make sense. The reason for this is I cannot find a battery that will fit in the factory location that is at least 700 cranking amps. My factory battery is 450 CA group 151 (tiny battery). This is the battery I ordered.


Another thing I get multiple different answers on is if I need make sure I have matching batteries when wiring in parallel. The rep from Crutchfield said that it should be fine to wire the XP750 in parallel with the stock. He felt in my situation I should be fine. If he's wrong and they actually do have to match, wouldn't a diode battery isolator solve this problem?

Also, can adding a 2nd or more powerful battery actually cause stress and destroy the 105 amp alternator? I always thought that it is the demand of the amps that would put stress on the alternator and not the battery.

I have a hard time believing that I actually need to upgrade my alternator for a 700-750 watts rms system.

Any help would be appreciated!
 

AnthonyO

CarAudio.com Veteran
10+ year member
Oct 18, 2005
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Minot, North Dakota, United States
700-750 watts will pull about 60 amps at full tilt. So in my opinion, just do the big 3 and you will be fine.
 

Mcdaddy7777

CarAudio.com Newbie
Oct 6, 2018
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  • Thread Starter Thread Starter
  • #4
Thank you for the reply's! I think my reasoning behind the thought of upgrading the battery is this video:


A good way to tell which size battery you need is by matching the battery's cranking amps with a total rms wattage of the system.
My stock is only 450 CA.
 

AnthonyO

CarAudio.com Veteran
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Oct 18, 2005
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Minot, North Dakota, United States
My stock alternator in my Mitsubishi is 130 amps.

Rockford Fosgate R2-300x4 recommended fuse 60 amps - Max. Current Draw (13.8V Sinewave) 39 A

Rockford Fosgate R2-500x1 recommended fuse 80 amps - Max. Current Draw (13.8V Sinewave) 52 A


I have not done the big three (YET). And I have not upgraded my battery. I run my stereo everyday with A/C full blast, with no problems.
 

Jonnyswboy

CarAudio.com Regular
Jun 28, 2019
200
33
You will be fine. Clamped 1500RMS on my stock 100A alt and a 75AH AGM.
 

Kickstand

CarAudio.com Veteran
Jan 1, 2021
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241
Maple Ridge
I was running 1750 watts off my stock 110 amp alt for a long time and it was fine
I would suggest to upgrade the battery but a second one is better
 

hispls

CarAudio.com Veteran
5,000+ posts
10+ year member
Sep 10, 2009
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Central Maine
I wouldn't worry about throwing money into your electrical system (provided everything is working) until you get up over 1200-1500W range and that's only if you like pushing things hard.
 

audiobaun

CarAudio.com Veteran
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Jun 28, 2011
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Get the Big 3 done and start there.I had a 90 amp alt. on my old CRV and ended up running approx 1750 RMS on subs and approx 200 rms on mids and highs, and did my ELD by-pass and ran two batteries on same alt with no issues. That battery is small in the Fit.But for the wattage you are wanting to run.. Big 3 and try the battery you have. I would think about investing in a bit larger battery in the future.. but thats me
 

audiobaun

CarAudio.com Veteran
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As Ive always said... Takes power to make power
 

Mcdaddy7777

CarAudio.com Newbie
Oct 6, 2018
9
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I see a lot of video's where the 2nd battery is being wired in series. I thought this would double the voltage, which I woudn't want. However, I read online that they must be in parallel and must match. How is it that I'm seeing people using dissimilar batteries and wiring in series? For example, I have a XP750 that I would like to use as a supplemental battery to power the audio gear since my primary is so small.


I can't even use the XP750 as a primary battery anyway because it's not design to start the car.
 

Mcdaddy7777

CarAudio.com Newbie
Oct 6, 2018
9
0
  • Thread Starter Thread Starter
  • #12
I see a lot of video's where the 2nd battery is being wired in series. I thought this would double the voltage, which I woudn't want. However, I read online that they must be in parallel and must match. How is it that I'm seeing people using dissimilar batteries and wiring in series? For example, I have a XP750 that I would like to use as a supplemental battery to power the audio gear since my primary is so small.


I can't even use the XP750 as a primary battery anyway because it's not design to start the car.
Ok, please disregard this statement. I am very uneducated (and somewhat a dumb dumb), because series is something like this:

30905


So, when I mention the videos, basically what they do is run a positive wire to the 2nd battery (no isolator), wiring power wire to amp(s), and appropriately grounding each of the batteries in their respective locations. On the other hand, I hear so many say they have to be in parallel and must match. What is the reason for parallel as opposed to just connecting them together with the power wire? Is it only so that you can double the amp capacity as opposed to just using the 2nd battery as supplemental dedicated for the sound system?

In my case, I don't need to double the capacity, but dedicate the primary for car electronics/electrical and 2nd for amps.

The other question is, do I actually need an isolator if the two batteries are not the same? Hypothetically, let's just pretend that I will not leave the audio system running without the car started 99% of the time. Also, I would take care to appropriately charge the secondary properly fairly often when at home. Could I still run into problems of the batteries try to **** the life out of each other for being different while the engine is running or completely off siting in the parking lot? I would like to say the answer is no, because the alternator should take over the charging when started right?

I'm not trying to be a cheapskate, and I don't mind getting one if it's necessary. I just want make sure I'm not doing more work than is necessary as space is kind of an issue with my Honda. Also, I don't think a diode isolator will be easy to work with due to limited space under the hood and I prefer to not wire it all the way back or near the front seats. It would have to be a relay isolator.

Also, all of this is just me thinking ahead in case I have problems with the headlights dimming even after doing the big 3. Also, after doing more research and seeing the answers above (thank you btw), I am fairly convinced that I don't need a new alternator.

Please forgive the basic questions here. I realize it's only a matter of understanding basic electricity. Otherwise, I probably wouldn't be asking.
 

Popwarhomie

Team Lethal Pressure
5,000+ posts
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Jan 22, 2010
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Ok, please disregard this statement. I am very uneducated (and somewhat a dumb dumb), because series is something like this:

View attachment 30905

So, when I mention the videos, basically what they do is run a positive wire to the 2nd battery (no isolator), wiring power wire to amp(s), and appropriately grounding each of the batteries in their respective locations. On the other hand, I hear so many say they have to be in parallel and must match. What is the reason for parallel as opposed to just connecting them together with the power wire? Is it only so that you can double the amp capacity as opposed to just using the 2nd battery as supplemental dedicated for the sound system?

In my case, I don't need to double the capacity, but dedicate the primary for car electronics/electrical and 2nd for amps.

The other question is, do I actually need an isolator if the two batteries are not the same? Hypothetically, let's just pretend that I will not leave the audio system running without the car started 99% of the time. Also, I would take care to appropriately charge the secondary properly fairly often when at home. Could I still run into problems of the batteries try to **** the life out of each other for being different while the engine is running or completely off siting in the parking lot? I would like to say the answer is no, because the alternator should take over the charging when started right?

I'm not trying to be a cheapskate, and I don't mind getting one if it's necessary. I just want make sure I'm not doing more work than is necessary as space is kind of an issue with my Honda. Also, I don't think a diode isolator will be easy to work with due to limited space under the hood and I prefer to not wire it all the way back or near the front seats. It would have to be a relay isolator.

Also, all of this is just me thinking ahead in case I have problems with the headlights dimming even after doing the big 3. Also, after doing more research and seeing the answers above (thank you btw), I am fairly convinced that I don't need a new alternator.

Please forgive the basic questions here. I realize it's only a matter of understanding basic electricity. Otherwise, I probably wouldn't be asking.

No you don't need an isolator.
No the batteries don't have to match. AGM can be ran with lead acid.
Front battery positive to rear battery positive and ground your rear battery to a good grounding point in the rear.
Wiring in series would cause 24 volts.
Only time one battery is going to kill the other battery is if one battery is going bad. had this happen before once before. Front battery was dying and causing rear battery to drain.

Halogen headlights are very sensitive to voltage changes. 0.1 volts can make halogen dim. Best fix is a relay harness for the headlights. Or even adding a capacitor inline of the headlight harness to filter out the voltage dips.
 
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Kickstand

CarAudio.com Veteran
Jan 1, 2021
795
241
Maple Ridge
When I changed from Halogen to an HID kit in one of my cars it stopped the headlight dim
Something about regulated power source
Just the headlight dim though
all the other lights still dimmed
But my car was no longer Stu's disco inferno driving down the road
 
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