Scotnemily Posted December 12, 2019 Report Share Posted December 12, 2019 Ok currently I have a H9/95r battery, and and H8/94r battery. Both are located in my trunk. In the process of preparing for a higher power amp, I thought it would be a good time to get a voltage baseline before hooking up a larger amp. I put in a voltage meter that plugs into the cigarette lighter. (I have also checked the findings with a fluke meter to verify the one plugged in) I was surprised to find out I already have an issue. I haven’t noticed it yet except for reading the voltage. The problem is after the car has set all night, I am reading 11.8 volts before the car starts. Starting drops it to around 10 volts. The alternator puts it back up above 14 volts. The car starts easy and if it wasn’t for seeing the voltage was low, I would not be able to tell yet. However the batteries are almost 5 years old now, and they are definitely going out. At least one is. I am not going to put a new battery in with one of these though even if one tested ok. Since I have to buy at least 1 battery, and probably 2, what is the best option? Factory battery is huge. H9/95r https://shop.advanceautoparts.com/p/autocraft-platinum-agm-battery-group-size-h9-950-cca-h9-agm/10866724-P?searchTerm=H9+battery Height: 7.5 in Length: 15.562 in Width: 6.937 in The h8 is just slightly smaller. I can fit these in because I have them now. But this set up might not be ideal. Normal car batteries are not the best batteries for car audio. So I could buy a h9 or other recommended size and another battery like a northstar or something from Xs power. Maybe even go lithium, as long as I get one that likes being hooked up with a AMG battery. Or I could get one larger battery, or maybe 2 of the SMSAGM220 batteries, though that is more then I wanted to spend. I would like to be under $500 but if needed I could go higher. I don’t have any experience with those smsamg batteries but I didn’t think there were best used as a starting battery. So maybe one of those with the H9? Any help would be appreciated! Thanks Link to comment Share on other sites More sharing options...
Scotnemily Posted December 12, 2019 Author Report Share Posted December 12, 2019 I should also note the car does not have to be shut off long to see the voltage drop. It happens quickly. As soon as I turn off the car the meter goes to 13. Then with in 30 seconds it is down to around 12.2 or 12.1 volts. It has to set hours to go lower, but over night is enough to be below 12 volts Link to comment Share on other sites More sharing options...
Joshdashef Posted December 12, 2019 Report Share Posted December 12, 2019 what kind of amps are you wanting to run? Around 100 ah of AGM with a good alt would do you right for quite a bit. Ditch the lead acid batteries. Go with AGM, and charge them every month or so to prolong life. I love my XS batteries but plenty of other companies make them. An XS D series for under your hood within the dimensions you listed is the - D4900. Length – 13.90 inHeight – 7.48 inWidth – 6.93 in some modification may be required since this is not exact but so long as you can secure the battery you will be fine. If your looking for a rear reserve battery I would get the XP series, yes you can mix them. Difference explained here: “XP series is only made for secondary battery applications and not made to be used under the hood.The XP series will give you the reserve capacity you need, but does not have the instantaneous power that the D series has. You would see a difference on the meter, but probably never hear the difference in a daily use/demo vehicle.” @Nathan @ XSpower XS website: https://4xspower.com/shop/12v-agm/d-series/d4900/ Distributor: cheapest I could find is 350$, other ones have listed for 399$ (Crutchfield for example). Here is SSA store page listing: https://store.soundsolutionsaudio.com/products/xs-power-d4900-agm-battery.html Probably want some post adapters if you go with XS, they make a whole slew of side post and regular ones found on lead acid. SMD Tool Map (2022): https://www.stevemeadedesigns.com/board/topic/220267-smd-tool-map-2022/ My Port Size Calculator (in progress): https://www.stevemeadedesigns.com/board/topic/217087-port-size-calculator-in-progress/ Common Port Walls for a Slot Port: https://www.stevemeadedesigns.com/board/topic/217076-common-port-walls-why-it-matters-to-your-box/?tab=comments#comment-3240313 Link to comment Share on other sites More sharing options...
Scotnemily Posted December 12, 2019 Author Report Share Posted December 12, 2019 Thanks for the help! I should also have mentioned the factory battery location is in the trunk. That is why I have 2 there already. Stuck with a 150 amp alternator for and possibly permanently. Though if I had to there are 2 options a 240, and a 300. Neither are desirable. But if I can’t get where I need with battery power then I could do the 240. I will be somewhere in the 3000 rms range. And was thinking I need around 200 Ah or a little more. After reading the info above, I will probably plan on picking up a H9 AMG and an additional 2nd battery. Link to comment Share on other sites More sharing options...
Joshdashef Posted December 12, 2019 Report Share Posted December 12, 2019 The alternator would help alot but it is the more expensive route. I'd plan in your build to take up extra space with batteries, then keep adding them till your happy with voltage. 200 ah is a good place to start. SMD Tool Map (2022): https://www.stevemeadedesigns.com/board/topic/220267-smd-tool-map-2022/ My Port Size Calculator (in progress): https://www.stevemeadedesigns.com/board/topic/217087-port-size-calculator-in-progress/ Common Port Walls for a Slot Port: https://www.stevemeadedesigns.com/board/topic/217076-common-port-walls-why-it-matters-to-your-box/?tab=comments#comment-3240313 Link to comment Share on other sites More sharing options...
Scotnemily Posted December 12, 2019 Author Report Share Posted December 12, 2019 Thanks! I was just advised on the phone to just use a single Northstar AGM31 PRO battery. It does have more power than my current single h9 battery I was looking at. It is also quite a bit more than a single h9 but less than a h9 and a second h8 or something else. I could however get a H9 AGM battery and a H8 AGM battery from somewhere like advance auto for close to the same thing as a single Northstar AGM31 PRO. or I could try a Northstar AGM31 PRO and add something else later if I needed it, which i might not anyway. Thoughts? Oh and One main reason I was not wanting to change out the alternator (besides the cost and time) I am not sure how much life this car has left in it. Batteries and other things can be used in a different vehicle. the $500+ for the alternator will only be used for this car. I want that to be My last choice. Link to comment Share on other sites More sharing options...
Joshdashef Posted December 12, 2019 Report Share Posted December 12, 2019 16 minutes ago, Scotnemily said: Thanks! I was just advised on the phone to just use a single Northstar AGM31 PRO battery. It does have more power than my current single h9 battery I was looking at. It is also quite a bit more than a single h9 but less than a h9 and a second h8 or something else. I could however get a H9 AGM battery and a H8 AGM battery from somewhere like advance auto for close to the same thing as a single Northstar AGM31 PRO. or I could try a Northstar AGM31 PRO and add something else later if I needed it, which i might not anyway. Thoughts? Oh and One main reason I was not wanting to change out the alternator (besides the cost and time) I am not sure how much life this car has left in it. Batteries and other things can be used in a different vehicle. the $500+ for the alternator will only be used for this car. I want that to be My last choice. Northstar is a good brand so I'd give them a try. Most AGMs you find in places like Adv Auto are not going to perform the best compared to others imo. Yeah if the car has a limited life go all battery for now, maybe some cap banks if your voltage isn't steady. SMD Tool Map (2022): https://www.stevemeadedesigns.com/board/topic/220267-smd-tool-map-2022/ My Port Size Calculator (in progress): https://www.stevemeadedesigns.com/board/topic/217087-port-size-calculator-in-progress/ Common Port Walls for a Slot Port: https://www.stevemeadedesigns.com/board/topic/217076-common-port-walls-why-it-matters-to-your-box/?tab=comments#comment-3240313 Link to comment Share on other sites More sharing options...
Scotnemily Posted December 12, 2019 Author Report Share Posted December 12, 2019 Ok thanks for the help! Link to comment Share on other sites More sharing options...
Scotnemily Posted December 16, 2019 Author Report Share Posted December 16, 2019 Currently the plan is to get a G31 from Northstar. I am doubtful this will be enough. Though I am going to run 2 ohms for a while so only around 2000 watts RMS. I was thinking about getting a SMSAGM220 from Northstar. But I could also get the SMSAGM80. the 80 is smaller and cheaper, and might be enough power. If it isn't then I could always add another SMSAGM80 and be close to the SMSAGM220. does this plan or line of thinking seem like a good place to start, or am I going about this all wrong? thanks! Link to comment Share on other sites More sharing options...
Scotnemily Posted December 16, 2019 Author Report Share Posted December 16, 2019 I also found this beast... https://www.amazon.com/dp/B01KN7K48W/ref=emc_b_5_t?th=1 a 200Ah Gel battery. Don't know how well it would work for car audio, but about the same price as the northstar G31 Link to comment Share on other sites More sharing options...
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