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Voltage drop limitless lithium


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Current build sundown sae 3000 with fi btl 15, xs power s series 3400 under hood, limitless 45ah in rear of car. Dual runs of 2/0 sky high ofc. Big 3 consist of 1/0 gauge (this will be redone in 2/0 ofc) but current wire is cca. I have a singer 270 amp alt. I was under the assumption that 45ah of lithium would be acceptable for up to 8k watts. These reason I got lithium was to support 2 sundown sae 3000 amps strapped to a 2ohm load for 2 dc lvl 5's. I've seen videos of guys running this lithium battery with basically zero drop running bigger equipment. Mine had dropped to 12.8 and I backed off because I didnt want to go any lower than that. Maybe these guys had some other serious electrical that they didnt mention but if one amp is making it drop then having another really concerns me. Maybe I have my stinger voltmeter hooked up in a bad way but I thought it didnt matter where it was hooked up. I have the power going to the positive of the lithium and the negative grounded to metal behind the radio. Am I expecting to much and the drop in seeing is normal? Is my voltmeter hooked up in a shit way? Or am I fucked considering I've already bought and received the 2 dc subs and the other sundown amp. 

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you're running an agm and a lithium presumably connected to the same alt.  due to the different chemistries of the batteries and AGMs typically resting aroun13v, it will be a constant drag/draw on the lithium, never really allowing it to fully top up and be full strength.  even with the vehicle running.  if you want to truly get everything out of that expensive ass battery, you need to have a dedicated audio alternator in addition to your stock vehicle one, or you can eliminate the agm up front or some people even use a 500A battery isolator.  500A may not be enough to handle the current the lithium can put out tho.  12.8 is a massive drop for lithium which tends to hold between 14-15v, also it dropping to 12.8 tells me it's pulling down to the agms resting voltage which means it's compensating for that and not able to do it's job in regards to supplying the power for your music.

 

so recap, 2nd alt only supplying the lithium, delete the agm battery, or a very high amp isolator MAY work.

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Just an update. I changed my big 3 wires to 2/0 ofc and used copper lugs instead of those other pos I had. I wasn't able to immediately remove the battery so I left it in for the time being to see if the upgraded wires had improvement. I also tweaked my gain on my amp. I initially used a dd1 but it doesnt detect distortion on my radio for some reason. At max volume it indicates no distortion even tho it can audibly be heard so I'm guessing the factory amplifier for the door speakers maybe doesnt work right with the dd1 so I just went by the dmm method for a starting point and tweaked from there. Before i certain i was clipping pretty bad. While driving the volts would stay between 14 - 14.3. If idling the lowest I saw was 13.7 I believe. Today I removed the agm and I had the same exact results. So as long as I'm driving I stay in the 14s. At idling it holds high 13s. I'm guessing with a second amp I'd see high 13s while driving and mid to low 13s at idle. Sound normal?

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