Adding a battery in the back, is it necessary to upgrade under the hood battery?

[alec14 10+ year member]

Hey guys, so I'm looking to add just a small Shuriken BT-20 in the rear, to help my sub amp. Only problem is, I don't have the money to upgrade my stock battery in the front. Will this cause any serious issues to my electrical or anything? Thanks in advance for any and all help!

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[psych0ticnemes1 5,000+ posts]

As long as the batteries are both AGMs, you should be fine. I don't believe the starter battery and axillary battery(s) have to be the same brand. I think that's a myth to get you to buy all the same.

You can't afford a bigger battery in the back? If you're upgrading, you might as go as big as you can. There's not downside to having a lot of juice, especially if you ever upgrade.

 

[naughtyca 10+ year member]

both does not have to be AGM, I ran stock battery up front and agm at the back for almost a year and had no issue

 

[alec14 10+ year member]

both does not have to be AGM, I ran stock battery up front and agm at the back for almost a year and had no issue

what happened after a year?

 

[alec14 10+ year member]

As long as the batteries are both AGMs, you should be fine. I don't believe the starter battery and axillary battery(s) have to be the same brand. I think that's a myth to get you to buy all the same.
You can't afford a bigger battery in the back? If you're upgrading, you might as go as big as you can. There's not downside to having a lot of juice, especially if you ever upgrade.

No, I don't believe my front battery is AGM, i think it's wet cell. and I'm not running too much power, only about 1000 rms, and I'm trying to conserve space if i can

 

[hispls 5,000+ posts]

what happened after a year?

I think he's implying he did this a year ago and hasn't had any problems.

No, I don't believe my front battery is AGM, i think it's wet cell. and I'm not running too much power, only about 1000 rms, and I'm trying to conserve space if i can

If it were me, I'd invest in a high quality AGM up front and be done with it. Putting a brand new AGM in parallel with a wet-cell of questionable age, quality, and output may shorten the life of your new one. Ideally you don't want one much older than the other(s)

 

[naughtyca 10+ year member]

what happened after a year?

i replaced with yellow top but the battery is still good, i have it as a backup

 

[smoka 10+ year member]

Batts have a resting voltage. Generally around 12.7 to 12.8.

So if your front batt rests at 12.6 since its older, and you buy a new trunk batt that rests at 12.8. While the car is off, your trunk batt will try to charge the front one.

So long story short, you should expect about half of the life by mixing batts.

I believe the avg lifespan of a batt is around 7 years depending on climate.

That is why best option is to buy 2 batts at the same time with identical date codes and voltages.

 

[alec14 10+ year member]

I think he's implying he did this a year ago and hasn't had any problems.


If it were me, I'd invest in a high quality AGM up front and be done with it. Putting a brand new AGM in parallel with a wet-cell of questionable age, quality, and output may shorten the life of your new one. Ideally you don't want one much older than the other(s)

Ahh, okay. Thanks, I was kinda thinking that's what I might need to do

 

---------- Post added at 07:29 PM ---------- Previous post was at 07:28 PM ----------

 

i replaced with yellow top but the battery is still good, i have it as a backup

Okay. Well that's good to know, I'm still considering all options

 

[alec14 10+ year member]

Batts have a resting voltage. Generally around 12.7 to 12.8.
So if your front batt rests at 12.6 since its older, and you buy a new trunk batt that rests at 12.8. While the car is off, your trunk batt will try to charge the front one.

So long story short, you should expect about half of the life by mixing batts.

I believe the avg lifespan of a batt is around 7 years depending on climate.

That is why best option is to buy 2 batts at the same time with identical date codes and voltages.

Thanks for info, that's really good to know!