isolator issue

Im trying to install an isolator from stinger SGP 32. The issue im having is i installed the isolator but i never did one before and not sure to install. The vehicle has a yellow top battery from optima and a stinger battery in the truck 2400 and the amp is cranked to 210 amps but the system is still running between 11.9 and 12 in the trunk so im guessing that i wired it wrong. Thank u in advance.

Confidence is the key to any project!!

No - it's probably a cable voltage drop. Measure the V-drop between the battery or isolator and the amp (at 210A etc).

WIth the car running the battery in the front is only getting 12 volts and the wire coming from the alternator is throwing 12.4 give or take a point but i also heard that the isolator makes the voltage to the battery drop .6 volts and up to 1 volt is that true

Confidence is the key to any project!!

The voltage drop applies to diode-type isolators, but they won't handle those currents. Besides - imagine getting rid of 0.6V x 210A = 126W of heat from that diode.    IMO they are not good especially if no compensation for diode's voltage drop (as in D+ alternators etc) - except when used in stator systems etc as in marine & RVs (that have no "is charging" circuit as in charge lamps or current sensing etc) where they ca have advantages over voltage-sensing isolators. Otherwise IMO charge(-lamp) controlled relays are the simplest, cheapest & most reliable isolator. You have 2 problems: (1) Your alternator isn't big enough (at that RPM) - it should be putting out (say) 13.8 to 14.4V. (2) You have a 0.4V drop between the alternator and front battery alone! If that's at 210A, that means about 2mR (milli-Ohm) resistance. Halve that resistance for half the voltage drop etc. If there is a fuse between the alt & battery and that contributes heavily to the resistance, consider removing it IF you can ensure reasonable physical security for the cable and if the main/front battery posts to which you connect are lead. I presume you have a 250A alternator or whatever will handle your average load plus a bit extra? If not, that is a essential requirement. (You may have measured your 12.4V at near idle, hence not full output.) But I also presume you have upgraded the Big-3? Check your battery -ve to chassis/body voltage drop and engine to chassis (or battery) voltage drops too - ie, ground/ground-strap voltage drops. Engine-chassis/body ground straps are easy to parallel, and using different locations can be beneficial (potential but unlikely ground loops excepted). But with 12.4V at the alternator and 12V at the battery, your battery is either very flat or being heavily discharged. I presume the stinger is near the amp? Maybe a standard battery in the front? But a fully charged yellow top will be around 12.0V (if not lower!) when supplying over 200A. The front battery should be at a higher voltage that the rear Optima assuming a voltage drop across the inter-battery cable and its TWO fuses. If it were zero resistance, the main (flooded) battery should supply up to half the current of the Optima, but in practice the difference is MUCH greater (maybe 1:4 or 1:10 etc).

According to all documents out there, you lose .7 volts across a diode. In the real world I have noticed that the .4 volts you are seeing is the norm.

Yep - it can be current dependent - though if I recall, basic Physics reckons 0.7V for Silicon (ie, transistor base-emitter). I usually use 0.6V but IMO there isn't that much difference - from 0.7 to 0.35V is double the heat and .35V is little overhead AFAIAConcerned (wrt designing PSUs etc - I design with reasonable overhead). As for using diodes in such hi-power applications - sorry guys, why do that when I can use a relay that is cheaper and handles more current with near-zero loss and no need to boost alternator output? (And easy to parallel for crank assistance - depending on interlink capacity else using circuit breakers.) Failing that I would use a MOSFET - eg, 100A for $3 with 20W heat dissipation. Of course there are other diode types. I used to like the older Germaniums for their 0.2V drops. And many Shottky diodes have lower drops. In fact which battery isolator manufacturer (this morning) reckoned they had ZERO voltage drop due to their Shottky's? LOL - Manufacturers and SalesCompanies - reinventing new Physics, Science, Math & Logic every day! We usually sue or fine bricks like that. PS - 0.7V is usually used as it leads to conservative design; ie, the diode has higher heat dissipation (in circuits above a few volts); signals/voltages need to be higher etc.

In the front of the car i have the optima yellow top and in the rear of the car i have the stinger 2400. The stinger isolator is under the hood. The only thing i can see that might be wrong is the wiring. There is 4 bolts on the top 2 are for battery 1 is for ground and one for true ignition. my question is where do i put the alternator wire. Do i put it on the isolator cause how i have it now is on one side of the isolator i have the alternator wire and the front battery connected together and the other side to the back battery which has a circuit breaker and then one i have for ground and the other i have going to the true ignition straight from the ignition harness. Maybe that the problem. The customer is going to get the alternator checked again because it was upgraded to 210ampsConfidence is the key to any project!!

The yellow top should be next to or as near the amp as possible - the interconnection resistance probably negates the advantage of low-resistance (ESR) AGMs. A normal battery should sit up the front. Oh wait - the Stinger 2400 is an AGM battery(??) which is in the rear... Otherwise you wouldn't need an isolator for a cap or an amp - isolators are used between batteries (unless the amp doesn't turn off) The alternator should go to the front (main) battery as normal. Isolators are inserted between the main battery's fuse and the fuse for the remote battery. The isolator has the two big terminals for the interconnection. The smaller terminals are its solenoid (coil) which require 12V to energise the heavy contacts. This is often done with Ignition +12V (and the other side to ground). But for dual-battery setups, the isolator should be energised by a suitable charge detection circuit, whether by common voltage sensing circuits or isolators, else alternator current sensing, or the almighty UIBI which is merely the charge lamp circuit available on many alternators (which will need an intermediate relay or other driver if the isolator's coil/solenoid current is too high for the charge lamp circuit).    When you wrote that the amp was "cranked to 210 Amps, did you mean it was drawing 210A, or merely that the alternator supplies 210A? A 210A alternator isn't big enough for a 210A amp - you need at least 250A, probably more (eg, 300A) depending on other loads and the driving profile. Nor is the stinger isolator big enough... (Don't forget to add the battery recharge current.) You could simply short the two big terminals and compare the voltage across the front battery, and the rear battery and the amp when the amp is running. The voltages should be the same, but that depends on the interconnect's resistance and whether it is supplying current to the rear amp & battery. And measure the alternator voltage between its output and chassis. For flooded batteries it should be in excess of ~13.8V; ideally 14.2 to 14.4V. But that may need adjusting to suit AGMs. If voltages do not match up, you can then measure individual grounds and +12V links for their respective voltage drop contribution.

found out the issue the alternator is set to run at 14 volts but only when the car is running. the car only has 12 when on idle. The customer is ordering an alternator from stinger so once i get that hopefully we will not have a problemConfidence is the key to any project!!

AFAIK - Stinger merely re-badge other products (relays (isolators), alternators, batteries, etc). And they add their $margin. And alternator won't put anything out if not rotating. Not that I think that's what you meant, but few put out 14V at idle - they are usually designed for ~14V at reasonable output at say 2,000 to 4,000 RPM depending on the engine etc. (Racers and Rallyers used to reduce alternator speeds due to consistent high engine RPM.) I suggest the customer holds off until they are sure what they require - unless he can buy one that is more than adequate, or has more dollars than sense. And I suggest a designed-for-purpose HO alternator. Alternators can be rewound for higher outputs, but they often fail on overload or consistent hi-power output because they don't have the thermal inertia nor the matched magnetics and components to provide normal alternator self limiting etc. (Refer to Synchronous Machines - ie, synchronous alternators that provide most of our domestic/industrial electricity. Other than an open rotor circuit, they a pretty much self protecting with known transient and sub-transient responses.)    And make sure the alternator is set to whatever voltage suits the batteries. (IE - no overvoltage - do not use the norm 14.2V or 14.4V if the AGM should only see 13.6V etc. But undervoltage also damages the battery...) Sorry about my last reply. Messy. It fell apart after I realised the Stinger 2400 was a battery and not a cap.