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Best Way to Hook Up Multiple Batteries?


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Dragorus 
Copper - Posts: 75
Copper spacespace
Joined: January 12, 2004
Location: United States
Posted: June 22, 2004 at 9:59 PM / IP Logged  
Want to know what is the best way to hook up multiple batteries off my new 200 amp alternator?......example....I want to use 2 batteries....one under the hood and one in the rear....should i use a 200 amp isolator, a 200 amp solenoid or a regulator.....I am experienced in wiring and car audio but am new to multiple battery setups....I want the most power to my amps while the car is running but not being able to drain the main battery when the car is off
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: June 23, 2004 at 3:38 PM / IP Logged  
I am going to get a lot of flack for this, but as an electrician with 6 years in the field, and a military electronics background, simply wire them in parallel. Alternator to front battery positive to back battery positive, then run your distribution block right from the rear battery's positive post. Isolators, solenoids, and all of those items are a waste of time if you have an alternator capable of charging two batteries in parallel (and 200 amps will do just fine) Those items will offer you safety when it comes to having to start your car, because only one battery will go dead, but then your system could still starve due to lack of current, and your system will gain absolutely nothing by having a second battery... Make certain you have cable enough to handle the current capacity of your alternator (200 amps, I recommend nothing smaller than a number 2, and make certain you use the same gauge for both batteries ground wires, as well.) and make certain you have TWO fuses between the batteries, one at each end, and each within 18 inches of the positive posts. This is to protect the CAR, not the batteries, do NOT skip this step. Additionally, the batteries MUST be the same type, manufacturer, CCA's, and AMP-HOUR rating, and should be within 3-6 months of age of each other.
Here is to the guys that are going to try to refute my advice... Have you ever seen a solar system, one with banks and banks of batteries? Have you ever seen an isolator on them? No, because batteries will charge identically, while at the same time sharing the source current. (total source current in milliamps, divided by the number of batteries) If he uses two identical batteries, one alone with a full charge will accept MAYBE a few hundred milliamps of charge current from the alternator, so, if you double this load to two batteries, you are looking at maybe one amp of total current required to keep the batteries topped off. The alternator is supposed to supply all of the power for accessories, right? With a 200 amp alternator, this will leave 199 amps to run his system and accessories and engine. Plenty. BUT this is also why it is imperative that he use identical batteries. If he does not use identical batteries the battery with the LOWER internal resistance will try to keep itself charged off of the battery with the HIGHER internal resistance, thus causing reduced battery life for at least one of the batteries. Also, the internal resistance of a lead acid battery varies depending on the state of charge, so you will never be able to tell exactly which way this process will go. Just use identical batteries,and you will not have to worry about any of these issues. I think I am done.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: June 23, 2004 at 3:46 PM / IP Logged  
Oops,that's 16 years in the field... Fat-fingering the keyboard again
Also I wanted to mention, this is EXACTLY what I did in my '01 Civic when I put my 165 amp alternator in.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
aggie altima 
Silver - Posts: 298
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Posted: June 23, 2004 at 3:55 PM / IP Logged  
Isolators are diodes, correct? Diodes essentially cause an average 0.7 volt drop, so the battery hooked up to your audio system will suffer a 0.7 volt drop, and thus your amps will suffer a 0.7 volt drop, decreasing the amount of power your amps are producing. I think this Rockford Fosgate battery isolator is one of the few that don't have a voltage drop across the isolator, but it's pretty expensive.
Jon
Don't like rockford subs? Then don't look at my car =)
Dragorus 
Copper - Posts: 75
Copper spacespace
Joined: January 12, 2004
Location: United States
Posted: June 23, 2004 at 6:38 PM / IP Logged  

aggie altima wrote:
Isolators are diodes, correct? Diodes essentially cause an average 0.7 volt drop, so the battery hooked up to your audio system will suffer a 0.7 volt drop, and thus your amps will suffer a 0.7 volt drop, decreasing the amount of power your amps are producing. I think this Rockford Fosgate battery isolator is one of the few that don't have a voltage drop across the isolator, but it's pretty expensive.

True and no Volt. drop with a Solenoid......The solenoid protects the main battery when ther car is off and connects them parallel when car is on .....Thanx guys for the info 

haemphyst 
Platinum - Posts: 5,054
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Location: Michigan, Bouvet Island
Posted: June 23, 2004 at 7:31 PM / IP Logged  
Do not use ANY DEVICES. Simply connect them in parallel. Read my post above again, and you will note that I said no devices. Leave all batteries connected to each other continuously, and all will be OK. Even with a solenoid, (or actually BECAUSE OF the soleniod) the rear battery will go through more, deeper, charge/discharge cycles, making it give out sooner than the front one. Just connect them together in parallel.
And while isolators, in their simplest terms, are indeed diodes, the regulator will always monitor the charge voltage of the battery, and adjust the field of the rotor inside the alternator to overcome this .7v drop. The output at the alternator will be .7v higher than nominal battery voltage, (thus overcoming the loss through the diodes) as long as the alternator and regulator are functioning correctly. This loss of .7v is another reason you would never use a solid state isolator (if any isolator at all). .7v times 200a = 14 watts wasted in the isolator alone... EACH diode. that's 28 watts total, which isn't very much in the total scheme of things, but why waste it at all? That is your charging power for the batteries! 28w /14v = 2amps... 1 amp of charging current per battery... Follow the KISS rule. Keep It Simple, Stupid. The fewer parts the better... Get rid of the idea of using the isolator... you'll be glad you did!
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
xTimx 
Copper - Posts: 354
Copper spacespace
Joined: September 13, 2002
Location: Canada
Posted: June 24, 2004 at 2:21 AM / IP Logged  
Best way to hook up multiple batteries?
A: wire them in parrallel. + to +, - to -. plain and simple. done and done. next topic please! :P lol
xTimx
Dragorus 
Copper - Posts: 75
Copper spacespace
Joined: January 12, 2004
Location: United States
Posted: June 24, 2004 at 7:26 AM / IP Logged  

haemphyst wrote:
Do not use ANY DEVICES. Simply connect them in parallel. Read my post above again, and you will note that I said no devices. Leave all batteries connected to each other continuously, and all will be OK. Even with a solenoid, (or actually BECAUSE OF the soleniod) the rear battery will go through more, deeper, charge/discharge cycles, making it give out sooner than the front one. Just connect them together in parallel.
And while isolators, in their simplest terms, are indeed diodes, the regulator will always monitor the charge voltage of the battery, and adjust the field of the rotor inside the alternator to overcome this .7v drop. The output at the alternator will be .7v higher than nominal battery voltage, (thus overcoming the loss through the diodes) as long as the alternator and regulator are functioning correctly. This loss of .7v is another reason you would never use a solid state isolator (if any isolator at all). .7v times 200a = 14 watts wasted in the isolator alone... EACH diode. that's 28 watts total, which isn't very much in the total scheme of things, but why waste it at all? That is your charging power for the batteries! 28w /14v = 2amps... 1 amp of charging current per battery... Follow the KISS rule. Keep It Simple, Stupid. The fewer parts the better... Get rid of the idea of using the isolator... you'll be glad you did!

Then why do the pro's use solenoids?

Dragorus 
Copper - Posts: 75
Copper spacespace
Joined: January 12, 2004
Location: United States
Posted: June 24, 2004 at 7:27 AM / IP Logged  

haemphyst wrote:
Do not use ANY DEVICES. Simply connect them in parallel. Read my post above again, and you will note that I said no devices. Leave all batteries connected to each other continuously, and all will be OK. Even with a solenoid, (or actually BECAUSE OF the soleniod) the rear battery will go through more, deeper, charge/discharge cycles, making it give out sooner than the front one. Just connect them together in parallel.
And while isolators, in their simplest terms, are indeed diodes, the regulator will always monitor the charge voltage of the battery, and adjust the field of the rotor inside the alternator to overcome this .7v drop. The output at the alternator will be .7v higher than nominal battery voltage, (thus overcoming the loss through the diodes) as long as the alternator and regulator are functioning correctly. This loss of .7v is another reason you would never use a solid state isolator (if any isolator at all). .7v times 200a = 14 watts wasted in the isolator alone... EACH diode. that's 28 watts total, which isn't very much in the total scheme of things, but why waste it at all? That is your charging power for the batteries! 28w /14v = 2amps... 1 amp of charging current per battery... Follow the KISS rule. Keep It Simple, Stupid. The fewer parts the better... Get rid of the idea of using the isolator... you'll be glad you did!

also not true because a 200 amp relay/solenoid does connect the batteries in true parallel when car is on......All it is is a 200 amp relay.......

haemphyst 
Platinum - Posts: 5,054
Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: June 24, 2004 at 9:30 AM / IP Logged  
I'm done. Do it the way you want. You asked for advice and the correct way to do it, and two people have told you how, yet you insist on "a solenoid" or "an isolator". Go ahead, put the thing in, and have fun replacing your system battery every other year. I am sorry for the tone, but when somebody asks me for advice, and I give it to them, I almost expect that they might listen to it, but instead you want to keep arguing the point. Read the first paragraph again, and you will know why I am upset with your argument. And to answer your question about the pros using solenoids... They SOMETIMES (not all of them do) use solenoids because they are charging more (potentially dozens of) batteries. They are also sponsored, and they do not care about the money required to replace the system batteries. The best way to do it in a street, everyday driver car is NO SOLENOIDS! BTW, a solenoid will waste power as well, whenever the coil is energized, perhaps as much as two amps (28 watts) again... Leave all of the extraneous (power wasting) parts out... wire the batteries in parallel, and go with it. Get all of the power you paid for in that 200 amp alternator.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
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