Battery Isolator solution?

breimann · 03-10-2004, 07:39 AM

I think I figured out how I am going to set up the electric of my car...

Use a battery isolator and connect a second battery (deep cycle) in the trunk, that will power the inverter, which in turn will power the PC. I'll build a carpeted box w/ exhaust fans and have the PC, inverter, fuse block, and battery inside.

This way it gives me an excellent power solution with a pretty easy hookup. However, Ive seen battery isolators range from $30 to $129 for almost the same rating! I've been told hellroaring.com makes some of the best units, but is there something a little cheaper that works as good? I've found a few on marine web sites... but they are generic brand. Any feed back is welcome! thanks!

Confused · 03-10-2004, 07:40 AM

Do a search for tank circuits here

Garry

breimann · 03-10-2004, 10:40 AM

Quote: Originally Posted by Confused

Do a search for tank circuits here

Garry

I did, but I wasnt able to find a complete solution, as in what Bat isolator they used... maybe I'm too much of a n00b to search properly? *shrug*

Retuprac · 03-11-2004, 04:08 AM

I use a battery isolator in my setup, however mine is very expensive. I use a Xantrex Pathmaker. Since I sometimes have a camper on my truck i needed to be able the isolate 3 separate battery banks. Anyway, this is a solenoid relay type isolator which produces no voltage drop. A cheaper diode based isolator is gonna drop the voltage down .7 volts, which may or may not be a factor for you. I know that the hellroaring is a good unit. Search for soleniod isolators maybe you can find a simple cheap one. Just be sure to get one that can handles the amount of amps that your alternator can produce. I personally think that if you can squeeze an extra deepcell battery in your car its by far the best tank solution. I survive my cranks and can run my carputer with the car off for hours on end with no probs.

breimann · 03-11-2004, 07:22 AM

Yeah I notised that the diode isolators have a voltage drop, that would lead me to believe that my batteries would never get the charge they were getting before the unit is installed.

I looked up the alternator in my car, it's only a 70 amp unit... I'll do some R&D on the other isolator you mentioned, thanks.

danon · 03-11-2004, 08:04 AM

Quote: Originally Posted by breimann

I think I figured out how I am going to set up the electric of my car...

Use a battery isolator and connect a second battery (deep cycle) in the trunk, that will power the inverter, which in turn will power the PC. I'll build a carpeted box w/ exhaust fans and have the PC, inverter, fuse block, and battery inside.

This way it gives me an excellent power solution with a pretty easy hookup. However, Ive seen battery isolators range from $30 to $129 for almost the same rating! I've been told hellroaring.com makes some of the best units, but is there something a little cheaper that works as good? I've found a few on marine web sites... but they are generic brand. Any feed back is welcome! thanks!

i built a sproggy and cutdown the power load off the battery by half. that gave me enough power to run my other accessories in the car. my ac-dc inverter which i have used for years have finally came to rest together with all the headaches of noise, beep warning, surprise rebooting, etc. as i have experienced it, dc-dc is the best power solution.

my sproggy(mastero mk3.5) can survive 3 sec. crank and can run my carputer for 1 hour with engine off but i just want to take some load off my main batt. so i'm getting my deep cycle batt. next week as my "tank". for batt. isolator, i'll just use Ricky327's "relay based" tank circuit plus a bit of modification by myself. it is i to my conclusion, much better that using diodes(continues supply to backup batt. & decreased voltage). relay based tank circuit only deliver extra current to backup batt(tank) if there is 12v on the relay.

you're right, commercial products are so expensive. if you have some spare time, and a natural diy'er, the cheapest way is to built it yourself. help is just right at the corner.

wizardPC · 03-11-2004, 07:08 PM

Buy this

then install it, or have an audio shop do it. That's the isolator relay that I use, and it works great.

NightHunter · 03-11-2004, 07:30 PM

use a diode, and a couple of relays and walla, you got your self a isolator.
I also put a 1n4001 diode on the positive wire going from the car battery to my backup. make the the stripe on the diode is facing the back up battery. This will keep the car from drawing power from your backup battery. I use this relay setup below also with my inverter and the $6 backup nicd I bought from a guy on this board.
this is what I did, compliments to "the specialist" for all the help, works works awsome..
"Since you only want the battery to charge when the PC is on, since we have no way of shutting off the charging cycle, you need the PC on to draw some juice away from the abttery do it doesn't overcharge.

Yo accomplish this, you basically wire a relay and hook it up to a molex so it connects the backup battery only when the PC is powered on and the 12 volt line on the molex is throwing out 12 volts.

Now this solves issues such as the accesory cuttingout during crank, the molex 12 wont cutoff during crank leaving teh relay connecting hte backup battery and wa la. No reboot. Well if I planned it right, I hope.

Does that make sense? I'm suprised no one ran the relay turn-on from the PC PS 12 volt Molex. I love my great ideas.

Make sure you put a 20amp fuse before everything "

hihidamon · 03-11-2004, 08:11 PM

Quote: Originally Posted by wizardPC

Buy this

then install it, or have an audio shop do it. That's the isolator relay that I use, and it works great.

There were 2 Stinger battery relays/isolators: 200Amp and 80Amp.

Is the 80A one good enough to do the average job? 200A sounds too much to me...

danon · 03-11-2004, 10:01 PM

Quote: Originally Posted by hihidamon

There were 2 Stinger battery relays/isolators: 200Amp and 80Amp.
Is the 80A one good enough to do the average job? 200A sounds too much to me...

i would even go for 40amp if its available

wizardPC · 03-11-2004, 10:17 PM

that's just a rating, not how much it actually draws. You could prolly go with the 80A since you have a 70A alternator. I got the 200 because I might be getting a 200A alternator later on. If you get one that's not rated high enough, then it may catch fire.

danon · 03-11-2004, 10:28 PM

correct me if i'm wrong, but if the relay is in between the two battery and not directly connected to the alternator, then it should be ok to have lesser than the alternator's amp rating even by half, right?

breimann · 03-12-2004, 04:38 PM

Well,

A relay wouldnt give me a voltage drop like an isolator - but,

In theory, I would need to use the same battery as whats in there now, right? Also, is there a danger of overcharging a batt? For example, if my main batt is charged and my second batt is 1/2 dead, then the alternator is going to make juice to charge the second battery, wouldnt that harm the first one?

Also, correct me if I am wrong but doesnt a battery isolator prevent overcharging of the primary battery?

I like the idea of not having a voltage drop w/ a relay but I do not want to risk hurting a battery. Wizard, what guage wire did you use, and what batteries? How long has your setup been working for?

It seems the more research and the more information I collect, the harder it is to make the final decision. I appreciate everybody's input! Thanks!

NewTechFool · 03-13-2004, 11:07 AM

Check out my post for variation on the solution for relays. It introduces a delay to give your engine/electrical system a break during startup.

http://www.mp3car.com/vbulletin/show...7&postcount=17

I purchased one, but have not installed it yet.

danon · 03-13-2004, 05:54 PM

Quote: Originally Posted by breimann

Well,
A relay wouldnt give me a voltage drop like an isolator - but,
In theory, I would need to use the same battery as whats in there now, right?

not exactly true.

Quote:

Also, is there a danger of overcharging a batt? For example, if my main batt is charged and my second batt is 1/2 dead, then the alternator is going to make juice to charge the second battery, wouldnt that harm the first one?

i've never seen a car batt. that was overcharged while being used by a car(altho there are some very rare cases too rare to include in here). car batt. are designed to withstand the harsh electrical environment of the automobile. the only problem you might have is trying to make the two batt. charged in equilibrium if one is half flat. even so, alternator are not designed to charge an almost flat battery. that batt. should be charged properly by a battery charger with an stable 14v current.

Quote:

Also, correct me if I am wrong but doesnt a battery isolator prevent overcharging of the primary battery?

even if you don't have a batt. isolator your car's elec. mechanism will do this.

Quote:

I like the idea of not having a voltage drop w/ a relay but I do not want to risk hurting a battery. Wizard, what guage wire did you use, and what batteries? How long has your setup been working for?
It seems the more research and the more information I collect, the harder it is to make the final decision. I appreciate everybody's input! Thanks!

in my 15 years of automobile experience (we use to customize car as a family business) i never had a case of a car overcharging a battery except from using main socket or a cheap charger. the problem you should be worrying about really is a flat battery.