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Dual Battery Setup Isolator or Separator? Which is best?

29K views 58 replies 22 participants last post by  kdcon  
#1 ·
I installed the polaris auxillary battery kit on my '08 Ranger Crew and I am very happy with the kit, however the battery separator seem to be a solinoid type and you can here a "click" when it switches charging for the main battery to the auxillary battery. I have also noticed when I'm driving at night that my lights dim and brighten when the separator switches from charging my main battery to my aux battery. I have my lights wired to my aux battery.

I have researched and found several manufactures making battery isolators that allow the alternator(stator?) to be attached and will enable charging of both batteries at the same time. Would this be a better setup and if so what size isolator would you guys recommend? 95 amp?

Sam
 
#2 ·
it's put a extra battery in as well but did not use a polaris product. I bought a basic starter solenoid for a car and wired it to the keyswitch so if the key is on, the extra battery is charging. i'm running about 700 watts of stereo and over 30 led strobes strictly off of the extra battery. works great for me and the cranking battery is always charged for cranking.
 
#3 ·
cdgofish said:
it's put a extra battery in as well but did not use a polaris product. I bought a basic starter solenoid for a car and wired it to the keyswitch so if the key is on, the extra battery is charging. i'm running about 700 watts of stereo and over 30 led strobes strictly off of the extra battery. works great for me and the cranking battery is always charged for cranking.
If you are using a starter solenoid, you should probably change to a continious-duty type. People are often confused, as they often look the same. However, a starter solenoid is designed for short, high-current duty(300amps, 60 sec or less), while continious-duty are for just that-and are usually rated for around 85amps continous. The problem is that starter solenoid's coils are not usually designed for long-term operation and may see premature faluire when used that way.
 
#6 ·
DJFAB said:
cdgofish said:
it's put a extra battery in as well but did not use a polaris product. I bought a basic starter solenoid for a car and wired it to the keyswitch so if the key is on, the extra battery is charging. i'm running about 700 watts of stereo and over 30 led strobes strictly off of the extra battery. works great for me and the cranking battery is always charged for cranking.
If you are using a starter solenoid, you should probably change to a continious-duty type. People are often confused, as they often look the same. However, a starter solenoid is designed for short, high-current duty(300amps, 60 sec or less), while continious-duty are for just that-and are usually rated for around 85amps continous. The problem is that starter solenoid's coils are not usually designed for long-term operation and may see premature faluire when used that way.
The one I have is continuous duty.
 
#7 ·
guy48065 said:
I remember seeing a 'hybrid' separator that uses a regular high-current relay but it's controlled by a circuit that won't let it connect to the alternator until the main battery is fully charged. Sounds like a smart approach.
http://www.powerstream.com/battery-isolator.htm

or there's some on eBay under "redarc".
That sounds like the ticket. I'm gonna check into that before wiring mine up. Thanks for the info'! :wink:
 
#8 ·
#10 ·
How does an alternator know when a single battery is charged?

Sam
 
#11 ·
guy48065 said:
Cheaper isolators have 3 terminals: 1 for the alternator to hook to and 1 for each battery. But how does the alternator "know" when each battery is charged? There are isolators that cost much more--maybe they can balance the charging somehow?
I'm no electrical expert by any means, but this is how it was explained to me...

The Alt has a voltage regulator that can sense when a battery needs to be charged.

The isolator will send the charge to whichever battery is lower.
 
#12 ·
the good thing of the isolator, if you forget some accessories running, and it drains the battery, it drains the secondary battery, and the machine will still start off the primary battery.....
 
#13 ·
elkbow said:
the good thing of the isolator, if you forget some accessories running, and it drains the battery, it drains the secondary battery, and the machine will still start off the primary battery.....
I love the idea of having that option.
 
#14 ·
JustinR said:
guy48065 said:
Cheaper isolators have 3 terminals: 1 for the alternator to hook to and 1 for each battery. But how does the alternator "know" when each battery is charged? There are isolators that cost much more--maybe they can balance the charging somehow?
I'm no electrical expert by any means, but this is how it was explained to me...

The Alt has a voltage regulator that can sense when a battery needs to be charged.

The isolator will send the charge to whichever battery is lower.
thats not how it works when using the isolator, the factory cables still connect to the primary battery, the main battery is charged as would normally happen, but the secondary battery is only charged when the isolator senses that the first battery is fully charged and will allow the charge of the secondary battery

Image
 
#15 ·
elkbow said:
JustinR said:
guy48065 said:
Cheaper isolators have 3 terminals: 1 for the alternator to hook to and 1 for each battery. But how does the alternator "know" when each battery is charged? There are isolators that cost much more--maybe they can balance the charging somehow?
I'm no electrical expert by any means, but this is how it was explained to me...

The Alt has a voltage regulator that can sense when a battery needs to be charged.

The isolator will send the charge to whichever battery is lower.
thats not how it works when using the isolator, the factory cables still connect to the primary battery, the main battery is charged as would normally happen, but the secondary battery is only charged when the isolator senses that the first battery is fully charged and will allow the charge of the secondary battery

Image
That would depend on how you have it wired...unless your isolator is different from most of them.
 
#16 ·
do you understand how an isolator works? it specifically isolates the secondary battery from the primary battery, the reasoning is two fold, one is to keep the main battery always charged, second is not to stress the charging system
 
#17 ·
elkbow said:
do you understand how an isolator works? it specifically isolates the secondary battery from the primary battery, the reasoning is two fold, one is to keep the main battery always charged, second is not to stress the charging system
I do, but I'm not sure you do.

It has nothing to do with stressing the charging system. There is no added stress or difference between charging two batteries without an isolator, and charging two batteries with an isolator. There's still two batteries getting charged from the same charging system. Two batteries without an isolator are essentially just one larger battery.

The primary reason to use an isolator is to prevent a full battery from discharging into a low battery. Without an isolator the two batteries would always equalize, so a low battery would drain the charge from the good battery....leaving you with two partially charged batteries. Isolators simply stop the current from flowing from one battery back to another.

The type of isolator you have and/or the way you have it wired is the only reason it's being used to have one starting/main battery and one accessory battery. Many people also use isolators in a different way. They can also be used where the main battery drives everything (starting, ECU, and all accessories) and the secondary battery is only used as a backup to "jump start" the vehicle if the main battery dies.

Another benefit of using an isolator is that you can run two different types of batteries (ie. a standard starting battery and a backup deep cycle battery).
 
#18 ·
JustinR said:
elkbow said:
do you understand how an isolator works? it specifically isolates the secondary battery from the primary battery, the reasoning is two fold, one is to keep the main battery always charged, second is not to stress the charging system
I do, but I'm not sure you do.

It has nothing to do with stressing the charging system. There is no added stress or difference between charging two batteries without an isolator, and charging two batteries with an isolator. There's still two batteries getting charged from the same charging system. Two batteries without an isolator are essentially just one larger battery.

The primary reason to use an isolator is to prevent a full battery from discharging into a low battery. Without an isolator the two batteries would always equalize, so a low battery would drain the charge from the good battery....leaving you with two partially charged batteries. Isolators simply stop the current from flowing from one battery back to another.

The type of isolator you have and/or the way you have it wired is the only reason it's being used to have one starting/main battery and one accessory battery. Many people also use isolators in a different way. They can also be used where the main battery drives everything (starting, ECU, and all accessories) and the secondary battery is only used as a backup to "jump start" the vehicle if the main battery dies.

Another benefit of using an isolator is that you can run two different types of batteries (ie. a standard starting battery and a backup deep cycle battery).
lol, let me help you out since you seem a bit confused, read and you may figure it out:

http://www.bcae1.com/battiso.htm
 
#19 ·
Thanks for the Info

elkbow said:
lol, let me help you out since you seem a bit confused, read and you may figure it out:

http://www.bcae1.com/battiso.htm
Thanks for this site it really helps to understand what is going on, I have the solenoid type isolator on my Jeep, I will do the diode type in my Ranger after reading this info.

Thanks, Jim
 
#20 ·
elkbow said:
JustinR said:
elkbow said:
do you understand how an isolator works? it specifically isolates the secondary battery from the primary battery, the reasoning is two fold, one is to keep the main battery always charged, second is not to stress the charging system
I do, but I'm not sure you do.

It has nothing to do with stressing the charging system. There is no added stress or difference between charging two batteries without an isolator, and charging two batteries with an isolator. There's still two batteries getting charged from the same charging system. Two batteries without an isolator are essentially just one larger battery.

The primary reason to use an isolator is to prevent a full battery from discharging into a low battery. Without an isolator the two batteries would always equalize, so a low battery would drain the charge from the good battery....leaving you with two partially charged batteries. Isolators simply stop the current from flowing from one battery back to another.

The type of isolator you have and/or the way you have it wired is the only reason it's being used to have one starting/main battery and one accessory battery. Many people also use isolators in a different way. They can also be used where the main battery drives everything (starting, ECU, and all accessories) and the secondary battery is only used as a backup to "jump start" the vehicle if the main battery dies.

Another benefit of using an isolator is that you can run two different types of batteries (ie. a standard starting battery and a backup deep cycle battery).
lol, let me help you out since you seem a bit confused, read and you may figure it out:

http://www.bcae1.com/battiso.htm
Funny, your own link doesn't mention anything about "stressing the charging system" without an isolator...yet that was 1 of your 2 major reasons for needing one. :lol:

The fact is there are different types of isolators and different ways to wire/use them.

The way yours is setup you could still end up with two dead batteries and no way to start it because you're always using both batteries. That's not likely to happen, but it could. A relay-based system is the only way to be 100% sure you have a true backup battery at all times. The relays can also handle a lot more amps than the others. Read here if you don't believe they exist... http://www.pirate4x4.com/articles/productreviews/12voltguy/
 
#21 ·
i use a relay for mine ...I have all the stock ranger equipment on the factory battery an all accessories on the optima ...the relay is triggered by the ignition also have a in line toggle switch to keep the relay off in case i remove the accessory battery or dont want it in the charging system...this has worked well for me

RB
 
#22 ·
elkbow said:
JustinR said:
guy48065 said:
Cheaper isolators have 3 terminals: 1 for the alternator to hook to and 1 for each battery. But how does the alternator "know" when each battery is charged? There are isolators that cost much more--maybe they can balance the charging somehow?
I'm no electrical expert by any means, but this is how it was explained to me...

The Alt has a voltage regulator that can sense when a battery needs to be charged.

The isolator will send the charge to whichever battery is lower.
thats not how it works when using the isolator, the factory cables still connect to the primary battery, the main battery is charged as would normally happen, but the secondary battery is only charged when the isolator senses that the first battery is fully charged and will allow the charge of the secondary battery

Image
That's exactly how a relay-type "isolator" is wired. Is that what you have?
The diode type is normally wired with the alternator going to a center terminal, then through a high-current diode to each of the 2 batteries. BOTH batteries get charged through the isolator and the loads connected to each battery can only be powered by THAT battery. It's all in that excellent car stereo link you posted.
 
#25 ·
JustinR said:
Funny, your own link doesn't mention anything about "stressing the charging system" without an isolator...yet that was 1 of your 2 major reasons for needing one. :lol:
Exactly right, and my degrees are in electrical engineering, and now i'm an engineering manager, and you?