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Second Battery Question

dmathews

Well-Known Member
Joined
March 17, 2009
Messages
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City, State
Beattyville, Kentucky
Year, Model & Trim Level
99 Explorer XLT
Ok so I have been searching around about adding a second battery in the rear and I know its recommended that I get a isolator and what not. My question is that I seen someone that you shouldnt use a normal battery bc when they charge they put out a gas or something and can catch fire or something crazy. Reading that worried me a little. I was going to just hook the battery up without the isolator at first bc from what i seen was a little high then get one and hook it up later. Just trying to get rid of the dimming effect.
 



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Why not just add a 200 amp alternator, this will solve alot of your problems?
 






Well I plan on it eventually but I already have the battery so I was wanting to hook it up. I dont rlly have a problem and the only lights dimming is my interior lights.
 






When are you getting this dimming effect? When the engine is running or not? Maybe its just time for a new alternator? Cauz you can hook up all of the batteries you can find, but if your alternator is weak and going to go bad in a week, then those batteries aren't going to help much once the batteries are drained.
 






Running 2000w amp to 4 kicker cvr 12s. Pair of 55 HID offroad lights and HIDs in headlights and in my fogs. I just had the battery and wanted to hook it up.
 






You can hook it up without an isolator - there's no harm is running a battery bank (batteries in parallel, not series). Just try not to mount it inside the vehicle because batteries can and do release sulfur oxide and hydrogen gases.

But with that said, I would check the alternator because batteries are just capacitors and can be drained over time, so they arent for continuous use where as alternators are. In other words, since the system is being drained by these accessories, the alternator must be able to supply at least the same amount of power or else the two (or three or four) batteries will be drained over time if the "drain" (power being consumed by the accessories and the rest of the vehicle) is larger than the "source" (power coming form the alternator). Or maybe run a smaller alternator pulley to increase the amps at lower RPMs.
 






we all have to know.....what are you doing when the lights dim? is it the dash lights ? courtesy lights ? over head lights? you're not driving around with your interior lights on are you ? car running or not? dash lights dim when you turn on head lights? give us more info. your battery is for starting and operating radio, lights etc. when the car is not running. the alternator runs everything when the car is running ...so extra batts. won't help you.
 






Ok so I have been searching around about adding a second battery in the rear and I know its recommended that I get a isolator and what not. My question is that I seen someone that you shouldnt use a normal battery bc when they charge they put out a gas or something and can catch fire or something crazy. Reading that worried me a little. I was going to just hook the battery up without the isolator at first bc from what i seen was a little high then get one and hook it up later. Just trying to get rid of the dimming effect.

Ok, let me address several points.

1) You can use several types of batteries. However, unless you are running a sealed AGM type battery (Optima or Kinetic brand) you will need to install a battery box and vent the battery to the outside.

2) You are correct. If you are running a normal 12v battery, they will vent hydrogen and oxygen. Not only is this flammable, it's also an explosion hazard above a certain concentration. Not sure what the LEL of hydrogen is.

3) You absolutely want to hook up a battery isolator. If you don't, the batteries can effectively drain each other down over long periods of time. Battery isolators can be had for $20 all the way up to $120 based on the type and size. The preferred TYPE of isolator for car audio is a solenoid-type. The solenoid type will allow the 2nd battery to charge when the car is running and isolate it from your starting battery when the car is off.
 






If you don't, the batteries can effectively drain each other down over long periods of time.
Yes but this behavior also exists in a single battery. In other words (and assuming that both are starting batteries), the mere act of connecting the two batteries to each other wont directly cause them to drain because connecting batteries in parallel is virtually similar to increasing the volume of each of the six cells. Once they are fully charged and the alternator is cut off, then the two can be treated as one big battery. Furthermore, connecting batteries in parallel without an isolator is common in the marine and heavy truck/bus world.

parallel.jpg
 






^^^^ what he said....

I don't know about the saftey concerns with mounting a car battery inside but there is no problem wiring them in parallel. They could also be wired in series which would double the voltage (bad for a car) but it wont hurt the batteries.

My boat has 3 batteries my calculator has 4...
 






we all have to know.....what are you doing when the lights dim? is it the dash lights ? courtesy lights ? over head lights? you're not driving around with your interior lights on are you ? car running or not? dash lights dim when you turn on head lights? give us more info. your battery is for starting and operating radio, lights etc. when the car is not running. the alternator runs everything when the car is running ...so extra batts. won't help you.

The dash lights dim when im at a red light at night. Rlly it is the only time, my headlights use to dim but they dont no more with the HIDs. And no I dont drive around with my interior lights on. I was just wanting to know if I can hook it up without the isolator and it be fine and about the interior mounting and now i know. My Brother installed a second optima battery for his subs and it quit the dimming of the lights.
 






What’s taking all your power? I see HIDs in your sig but no audio equipment. I would make sure your alternator is working first.
 






The 2000w amp and four subs is whats doing it. the only time it dims bad it when its cold and at night with the headlights and heater on. other than that its fine.. I just have the other battery and figured I would put it to use. I will probably get a isolator that way if im messing with it when my car is off and it dies my car will still start
 












The 2000w amp and four subs is whats doing it. the only time it dims bad it when its cold and at night with the headlights and heater on. other than that its fine.. I just have the other battery and figured I would put it to use. I will probably get a isolator that way if im messing with it when my car is off and it dies my car will still start

Ha, that will do it. Have you upgraded the factory ground wires? If not I would do that too...
 






Yeah I am going to do the big three upgrade soon.
 






Big 3 may be all you need. Start there, and work towards another battery. There should be space to get it under the hood with a little creativity.
 






^^^
best and cheapest way to start is with the big 3! then go to another battery. no need for an isolator. im on a big car audio team with over 40 guys that all have between 4-20 batteries and none use them.
with my 2600watt amp just the second batt wasnt enough and now that i have a 270amp alt and the batt i get no dimming at all
but with my 10000watt amp i had to put 2 semi truck batts in the back with the alt and it does ok but alot more to come
goodluck
 






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