Battery/Starter Dilema

[Paul Robertson]

We are at the Go-Cart stage in our build and have found out that the AGM Braille battery (B14115) we are currently using is not large enough to consistently crank the SL-C supplied Bosch starter :cry:. When we use a large (650 CCA) lead acid battery in parallel with our AGM battery, we are able to turn the starter motor over sometimes, however have still experienced enough voltage drop to shutdown the Infinity system (under 5V? per conversation with Infinity tech rep).

We are thinking of a new setup: Dedicated Lithium-ion battery wired directly to starter motor with a battery isolator (150 amp) from alternator to charge the Li battery and at the same time isolate it from the other battery. The existing battery will run all other systems and with the use of the battery isolator our safety cutoff switch should still function properly.

Does this sound like a good idea? What have other builders done?

 

[Jack]

Many are using a simple Optima Red Top.

 

[Will Campbell]

You may or may not need a different battery, but I'd be willing to bet that the problem is inadequate wire size in the starter circuit, including especially the ground.

Many builders have experienced poor cranking, all of which has been resolved by proper wiring, correct grounding techniques, etc.

After you correct the wiring, check the battery to see if it tolerates load. It's easy to ruin a battery with too-deep discharges.

 

[Paul Robertson]

Thanks for the quick reply. We forgot to mention some details: Graziano with an LS3 engine. Battery in front of car with 1/0 gage wire running through the pegasus safety switch to the starter. We have not grounded the transmission but everything is solidly mounted (no rubber) to the chassis; we assumed that this would provide an excellent grounding source for the entire vehicle. We grounded the battery with a 1/0 wire to chassis (a 1/0 gage wire over 10' should be good for 250 to 300 amps). The starter motor has not been grounded separately to the chassis; it is simply bolted to the transaxle. The voltage drop measured during starter activation is around 0.2V when measured at the battery at the front of the car and the starter motor in the rear. Once the engine is cranking the voltage was measured to be ~9.5V at the starter.

We will check the ground continuity, as this has been reported to cause problems with other builds.

We have tested the starter directly with a larger lead acid battery (hooked battery leads directly to starter motor on transaxle with large battery cables) and it has trouble turning the engine over. We installed another starter and still had the same problem. This tells us that we need a larger capacity in the system. Important to note that the starter turns the engine over at close to idle speed, it seems as if a higher gear reduction starter motor would benefit this setup.

Is anyone aware of a starter motor with a higher gear reduction?



We are trying to stay away from heavy Pb-acid batteries due to weight considerations, this is primarily a track car (with some street use). Hence why we are considering a Li-ion battery.

 

[Jack]

Suggest the ground to the transaxle. Simple but frequent issue.

 

[Terry Oxandale]

Ran into the same problems with mine. Once you start cranking, the sensor voltage is barely sufficient such that anything other than a fully charged battery will not work. During the tuning stage, I had two batteries in the car at all times, but once everything was mapped out for starting, I was able to eliminate the spare battery. Using the Optima Red-Top as the only battery, with 2/0 wire throughout the charging, starter circuit, and battery ground, with smaller grounds at the heads, and at the adapter plate for the engine, all using short wires to frame.

This was one of the many "enhancements" that ended up pushing the weight of my car over the 2K lbs.

One more thing; the ampacity charts I've seen indicate no where near 250-300 amps for a 1/0 (or even up to 4/0), so I may be missing something there.

 

[Daniel G]

I've had problems with the AGM Braille battery B14115 on my last build. I would use a proven battery like the Optima redtop with proper gauge wire and a good ground on the trans.

 

[Jerry Jackson]

Paul I have been through all the aggravation, and I am sure you have been pulling your hair out, with this battery/starter problem. I finished my SLC May 2015 and have been regularly driving it since so many starts.

This is from my Post 16 on 17th August 2016 http://www.gt40s.com/forum/rcr-forum-rcr40-slc-917-superlite-aero/48830-couple-graz-questions.html

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
SLC with LS7 crate engine and Graziano. Braille Lithium Ion Battery (same cranking amps as Corvette Racing)

Joe I had exactly what you are describing. Cranks like a spin dryer when cold, sounds like it has a 9 volt alarm battery when hot. I spent an enormous amount of time on this problem. Increased the Battery cable to 2/0 gauge, tried a lead acid battery, jumped the isolator switch and another new starter motor. Same result after all this. Same result with a very large marine cranking lead acid battery 3 feet from starter and connected neg and pos directly. With a start button when the engine and trans are cold a press and the engine runs. When warm this does not work but a quick press and release then a press and cranking is like cold. I find it quite practical to drive the car like this but I would like to get to the bottom of the problem As I have changed every component used in a crank for something different but could only try another of the same starter I am left with the conclusion that the starter is the problem. I have an effective heat shield protecting the starter.
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Since I posted this I had the brass tag on the braid between the solenoid and the starter motor melt through completely. This happened when cranking with a warm starter motor. I had noticed that this connection got unusually hot but took it that as it is a part of the whole starter assy Bosch know what they are doing. They do not and probably get away with this on easier cranking jobs. This tag is very thin for the current it has to pass. Of course when it is hot the resistance in this tag just amplifies the problem and eventually results in the meltdown.
I have attached photos of the melted tag and the copper block I made to replace it. The volume of this block can handle the current properly. I have not evaluated this work round yet but have confidence.

 

[Dan Carter]

X

 

[Steven Lobel]

Same starter, LS7 to Graz. I am running a Group 31 Battery (Northstar AGM31). Running 0g from battery to starter + and 0g from battery to starter bolt on block. Hopefully this helps avoid the problem. If not, the starter is easily accessible and replaceable. I am at least a month before first start.

 

[Frank Clark]

...sounds like it has a 9 volt alarm battery when hot...

Sorry to resurrect an old thread, but just saw this.

Jerry,

I had a similar problem. Turned out it was a bad voltage regulator in the alternator. Voltage was way too high. So basically it was cooking the battery. Once cooled off all was good again. The alternator was NEW. Voltage exceeded 18v when the engine was revved a bit.

R&R'd alternator and battery. All good.

Likely not your problem, but easy to check.

 

[Terry Oxandale]

It kind of looks like some discoloration on the starter terminal (very high localized heat)?

 

[Jerry Jackson]

Frank,

The real test for me that isolated the problem to the starter was a very large marine cranking lead acid battery connected 3 feet from starter terminal with 00 gauge positive and 00 gauge neg to starter mounting bolt. Solenoid engage signal from same battery. This isolates everything in the cars wiring or equipment. Same problem.

Terry,
The melted Bosch connector on the braid was the result of hanging on the start button for too long. Have not had that again with my quick press instantly followed by a normal cranking press which gets me great cranking and a clean start each time.