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New member Username: FastPost Number: 7 Registered: Jan-06 | i have a highly modified street/race car. i am currently running 2 svr80 batteries. specs= agm, 80amp hrs, 800cca, max amps 2600, 150 reserve amps. all wires completely modified, 2 batteries running parallel. high output alternator. my problem is that i have a very big fuel pump and 3 msd ignition boxes with sequential coil on plug ignition with 4 ignition expanders to work off my motec engine management system. when i am at idle(1200rpm) the voltage drops to 11.5 volts. at cruise above 1600 rpms or more the voltage is anywhere between 12.7-13.6 volts. what is a solution to having more reserved power to keep my voltage up at idle or stoplight without having to raise my idle rpms above 1600? should i add another battery or try to use a farad cap? i have a zapco c2k 4.0 and 6.0 wired in the car but don't have any speakers yet installed. i can fore see a bigger problem once i install some seperates and a sub. any suggestions? |
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Gold Member Username: CarguyPost Number: 6353 Registered: Nov-04 | How big is your HO alternator? Did you do the BIG 3 upgrade? Your current setup doesn't sound healthy at all. A voltage reading below 12.5v means the alternator's not supplying the power. At that rate, you will run out of battery very soon and get stranded. The voltage above 1600RPM is still too low. It should be above 14.2v or higher. If I were you, I wouldn't power the amps until the power problem is fixed. You really don't have any to spare! BTW, for now, disconnect the power to the amps. Write down on paper, anything that uses power while the car is running. Add up all the current totals and see how much it's using up. If it's close to the alternator's capacity then you need a bigger one. |
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New member Username: FastPost Number: 9 Registered: Jan-06 | i have a msd 160amp alternator. the big three has been done. i do need a bigger alternator. usually what rpm does a 200+amp alternator start charging. the race shop just did another car with the same ignition and they are using a cap which seems to keep voltage up at idle. |
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Bronze Member Username: TejcurrentPost Number: 64 Registered: Apr-07 | The cap will not keep the voltage up, it can actully drain it. as said above, if your alternator isn't keeping around 14.2v or higher, I'd look at what could be pulling power. If everything looks like it's hooked up right, and you've tested your batteries to make sure nothing is wrong with them, I'd get a new alternator. You can find some around 300amps-like iraggi and ohio gen. With the engine mods you're doing it seems like you're going for fast- so I'd hold off on adding additional batteries because of the weight for the time being till you can figure out what the problem is. You really don't want to get an alternator that is just getting by, I got a 200a alt and I killed it within a few months like this. |
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Gold Member Username: CarguyPost Number: 6356 Registered: Nov-04 | Go to bcae1.com and read up on alternator/battery and cap. A cap will not help in you situation. If it did, then there's a much bigger problem. Have you checked the work done by shop yourself? Not all of them are professional. If you really did have 160A alternator and it's dropping voltage by that much without any audio installed, you have a serious short somewhere. It doesn't add up mathematically. If you know any electronic engineer, ask them for advice. They'll tell you the same, something's eating up half, if not most of your power before the car's accessories gets a chance. If you're not sure, have the shop that worked on your car list all items and their power requirements. Add them all up, and you'll see whether 160A is enough. In my opinion, it should. |
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New member Username: FastPost Number: 10 Registered: Jan-06 | i have 3 of these msd ignition boxes: MSD DIGITAL 6-PLUS Operating Voltage: 12-18 volts, neg. ground (Full voltage output down 7 volts supply) Current Draw: 0.7 amp per 1,000 rpm (7.2 amp) with 14V bat.@ 10,000 rpm RPM Range: 12,500 rpm with 14.4 volt supply Spark Duration: 20° crankshaft rotation thru 3,300 rpm Spark Energy: 135 milliJoules per spark Weight and Size: 3.7 lbs, 8.5"L x 4.5"W x 2.2"H Voltage Output Max: Primary: 535 Volts delivered to coil Secondary: 45,000 Volts (MSD HVC Coil) and 10 of these direct coil on plugs: BLASTER HIGH VIBRATION SPECIFICATIONS Primary Resistance: 0.7 ohms Secondary Resistance: 4.7K ohms Maximum Voltage: 45,000 volts Inductance: 8 mH Turns Ratio: 100:1 Peak Current: 140 mA Spark Duration: 350 Us fuel pump is a weldon 2345 http://www.weldonracing.com/~weldon/ul-pdfs/43-2345-A.pdf running 60+psi also another water pump for intercoolers that is pretty big. along with 2 spal fans, motec ecu, digital dash, and other stock accessories and sensors. i have not checked the wiring work. where should i begin? the whole car has been modified and rewired.it was a year and a half project to complete this custom build. i will be taking it to my friends tuner shop to finish off a few odds and ends. here's some pictures so you can get an idea what type of build this was. http://www.svspower.com/case_study_detail.aspx?id=32 |
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Silver Member Username: Riebread77Post Number: 713 Registered: Jun-05 | yea...160 amps is not that big. my stock one is 105 amps. and at idle...i can guarantee that thing isn't putting out 100 amps. |
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Gold Member Username: CarguyPost Number: 6357 Registered: Nov-04 | Trent from what you listed, it's eating up anywhere from 50A - 80A. Now if you turned on air, headlights, nightlights, fan etc, then you'll use up even more current. 160A alternator should still be enough. They only way you'll run out of power is, if some of the upgrades you had, is faulty. That could explain why you don't have enough current left. What was the original alternator that came with your Viper? Was it 125A? Depending on the alternator's manufacturer, some design it so that at idle, you get 60% - 80% of the rated output. You should find out how much you're getting on yours. And don't get fooled into thinking the other the solution to your problem is the cap. It will NOT fix anything. If you have to get a bigger alternator, then look at 200A - 250A. Anything bigger and you'll be counteracting all the upgrades you did for speed. |
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Gold Member Username: JkidderSpring hill, Florida Usa Post Number: 1101 Registered: Nov-05 | sick azz car man. good luck with your problem. |
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Bronze Member Username: FastPost Number: 11 Registered: Jan-06 | thanks guys. will try to get all the electrical looked over. thanks for the breakdown isaac. anyone suggest trying an isolator between the batteries? |
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Gold Member Username: CarguyPost Number: 6358 Registered: Nov-04 | I would install an isolator between the 2 batteries so that your starter won't get drained by your upgrades. That will ensure you will always be able to start your car no matter what. |
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Bronze Member Username: FastPost Number: 12 Registered: Jan-06 | whats the best isolator and where should i buy one? |
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Silver Member Username: BelieveIllinois Post Number: 195 Registered: Jun-05 | the best way to cure voltage drop = more amperage |
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Gold Member Username: CarguyPost Number: 6359 Registered: Nov-04 | You can find isolator from just about any car related shops. Don't get confused with a relay. If you need more info, bcae1.com has them. If you can't find any shops, then you can always try the eBay. Make sure you match the amperage with the isolator. For example, if all you can spare is 120A from 160A alternator, then there's no need for 200A isolator, nor 75A. The goal is to match what you need with what's available. |
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New member Username: ZxhoonPost Number: 1 Registered: Sep-07 | if the alternator and regulator are ok and there isnt a major current draw on your system perhaps you can overdrive the alternator so at lower RPM it will put out a higher voltage for you... most people that add an under drive pulley on their car dont realise that the alternator/power steering/water pump /etc. will not work correctly at low/idle RPM... buy a current clamp meter (make sure it does DC) they dont cost that much considering the mods you have done to your car and really help when tracking down current draw problems... |