dual batteries

The battery isolator is there to seperate the two units from each other. ie. This means, if you run your stereo full tilt, while the vehicle is off. You will still be able to start the vehicle with the other SLI battery. If you remove the battery isolator unit, then both batteries will be on-line, and thus will be drained. This assumes you're playing music while the vehicle is off as well. Just so you know, if you are using a diode based isolator, this type of isolator has two very high current diodes in a heat sink encased into a shell. The diode based isolator has the advantage of a very long service life, and tend to perform trouble free in general. There is not maintenance involved as well. It should be noted that many of the diode based isolators cause a .4 to .6 volt loss which means that the batteries will not charge to as high a voltage as when they are connected directly to the vehicle alternator. Please be aware that the two batteries should be closely rated in CCA, Amp HR, and Reserve. The age of the battery should also be close together, as this will affect charging times, and service life. Regardless of the stereo output, the minimum diameter is 4 guage, and going to 2-1-0 is ideal as it reduces the resistance and ensures maximum current transfer. Please also ensure your ground cable is of the same guage as the power wire. Regards EVIL Teken...

i have a 200 amp alt with a optima red under the hood and a optima yellow in the back.  my cap was reading 9 volts and was beeping b/c of low power. i think there is a wiring problem b/c i charged the yellow battery yesterday and it read 23 volts on the tester. after the charge the cap read 13 but now i have lost power again.

Im sorry but you will have to clarify this for me again. You have +24 VDC where? And where and how are you measuring this voltage from? If the battery's were wired in series, than I could see that kind of voltage. In a parellel configuration, only current is increased, and the base voltage stays the same. The only other way to increase voltage & current is through a series / parellel configuration, but that isnt done in a *standard* road vehicle. Let me know exactly what isnt working, and what / where you are getting the measurments from. Regards EVIL Teken . . .

i have an 02 s10 blazer. i took the yellow battery out of the back of the car and charged it. i checked it with a meter the setting was 200 dc. it charged for  about 20 hours. i put it back in my car, chaged my cap for the radio. it worked fine for about a day,and then the cap starded beeping b/c of low power. the battery need to be charged again. i have a 200 amp alt with a 95 amp isolator. is the isloator big enough?

The first thing I would ask you to do is varify and measure the current drain from the vehicles primary starting battery. If you measure anywhere from 300-500 mA draw. Than you need to isolate and repair / remove the item in question, that is causing the current drain. The next thing I would suggest is to measure / varify that both batteries are indeed OK. You need to perform a open circuit test, (remove the battery terminals, after you have loaded the battery down with your head lights for 2 minutes, then wait 5 minutes and measure the battery voltage.) You should have a VDC of 12.70 to 12.80 +/- 0.10 this indicates a battery with 100% state of charge, meaning that it is full... The following is a reference as to what state of charge your battery is in, assuming you get these readings. 12.70 = 100% 12.40 = 75% 12.20 = 50% 12.00 = 25% 11.90 = Fully Discharged (All the above values will be off by +/- 0.10 given seasonal temperatures, and taking into account that a AGM battery will have a higher voltage reading when compared to a SLI lead acid battery) You have both types of these batteries in your vehicle... The Red top is a standard SLI, and the Yellow Top is a AGM. Do a current load test on the battery, or have a qualified mechanic use a Inductance Measuring tool, this will tell you 100% as to the actual service life of the batteries and if there are any dead cells. If you want to do a simple current load test. Start the vehicle. Let it warm up to operating temperature. You will be performing two sets of recovery load tests on the vehicles charging system. One is at idel, the other is at 2000 RPMS... During each test, you will add on accessories to the vehicle. ie. Lights, blower, windshield wipers, etc. You will note and measure the battery voltage coming from the alternator, and the recovery time it takes for the vehicles *regulator* to bring back the voltage to a nominal of 13.4 - 14.8 volts, measured at the battery terminal. The timne of recovery, and the voltage will be different for the idel, and the 2000 RPM measurments, but will be fairly close. If you have a current load test device, you will first ensure that the battery in question is fully charged and left to sit for 24 hrs prior to testing. From there you willload the battery to (1/2) half the CCA of the battery. ie. CCA is 500 amps divided by 2 = 250 amps. You will only load test the battery for no more than (15) seconds, and wait for five minutes for the battery to recover to the VDC of 12.70 to 12.80 Follow the above tests with the vehicle running and measure what the voltage is coming from the alternator to the battery. You should see 13.4 to 14.8 VDC while the vehicle is running, after all the loads are removed. A standard AVR test would cover everything I have asked you to do here. Other than to measure the specific gravity of each cell. SPECIFIC GRAVITY OF EACH battery CELL: 100% = 1.265 75% = 1.225 50% = 1.190 25% = 1.155 0.0% = 1.120 The Red Top battery does not allow you to do this. Another area you should check is that the capacitor is not in fact shorted out. This could be one reason for the battery going dead. Has there been any other changes in the system, no matter how small they may be, it would be helpful to know. The battery isolators current rating is fine. Regards EVIL Teken . . .