418 Ls3 cranks slow

[dhutton]

Seems to line up with this chart.
https://www.custombatterycables.com/...d-1024x287.jpg

Is that how cable sizing works? Just find a chart on the internet that matches what you want your cable size to be? Lol. Seems to be what im experiencing.

Not sure that a chart that includes insulation thickness is valid for all cables.

Don

[ORBandit]

Mine cranked so slow when I first built it, when hot, it would barely turnover. I added a larger ground from the battery to engine, didn't help. Added high torque mini starter, barely better..... Removed started, wire wheeled the paint from the block where the starter lives. Spins unbelievably faster now. Starts in less than 2 revolutions now.

[Zachalanche]

Mine cranked so slow when I first built it, when hot, it would barely turnover. I added a larger ground from the battery to engine, didn't help. Added high torque mini starter, barely better..... Removed started, wire wheeled the paint from the block where the starter lives. Spins unbelievably faster now. Starts in less than 2 revolutions now.

My engine is not painted. but that doesn't mean that i wouldn't benefit from this. I will consider it if sizing up the + cable doesn't help enough. I already have a smoking gun there, so i should see improvement.

thanks for the input.

[ryeguy2006a]

Maybe I missed it in the discussion, so I do apologize if it's been addressed, but is your motor grounded? When I did my first LS swap, I had a terrible time with it starting, and idling. Ran fine while revving though. As soon as I ran the battery cable directly to the engine block, all those problems immediately went away.

[Zachalanche]

Motor is not grounded direct to battery, but there are multiple grounds to chassis, and my voltage drop on the negative side (battery to starter housing) is 0.32V

since I am waiting for cable ends to show up, I just ran a quick test with the new Camaro cable (which should be 2/0). I ran it from the solenoid on the inner fender through the window to the battery and my voltage drop was 0.44V which is an improvement from the existing 0.95V (with the 2awg cable). Keep in mind this with a cold engine. if the load is higher with a hot engine there may be even more than a 0.5 V improvement.....I hope.

My guess is (and please correct me if this is wrong) that a 2/0 negative cable from the battery to the engine would give me a similar voltage drop as the positive side (assuming no other grounds were present), so if the existing configuration is showing 0.32V voltage drop My grounding is probably acceptable?? and it seems the chassis is able to flow more current than a 2/0 cable??

[Zachalanche]

Running the same cable arrangement, I am seeing a 13rpm increase in cranking speed. and there is little loss of cranking performance between the cold start and the hot start. It also appears that I am seeing my 0.5V improvement in voltage drop in hot and cold start cases.


This is a solid improvement, but still not as good as the engine bay mounted battery (which, if you remember, was a battery with lower CCA).

If i can get this working well enough, I'm considering moving the battery from the back seat to the trunk. Mainly because this whole exercise has made me realize it is a PITA to access the battery where it is. I originally wanted to centralize mass, but I don't think it makes enough difference to matter.

[Zachalanche]

I've been doing more investigation, doing voltage drop tests segment by segment. I found that my highest voltage drop was in the battery box. I don't know if it's the positive cable or the connection where it passes through the box. but when I measure voltage drop from the positive terminal to the lug on the outside of the battery box, I get .48 V which is significant. Sadly, this means that the improvement I will get going to the larger cable won't be as much but running the new cable direct to the battery rather than the bolted connection on the side of the box should help a lot.


Maybe I should have used some kind of bulkhead connector rather than a pass-through bolt.

[Zachalanche]

I've been doing more investigation, doing voltage drop tests segment by segment. I found that my highest voltage drop was in the battery box. I don't know if it's the positive cable or the connection where it passes through the box. but when I measure voltage drop from the positive terminal to the lug on the outside of the battery box, I get .48 V which is significant. Sadly, this means that the improvement I will get going to the larger cable won't be as much but running the new cable direct to the battery rather than the bolted connection on the side of the box should help a lot.


Maybe I should have used some kind of bulkhead connector rather than a pass-through bolt.

[NorCal-SS]

Could it be the crimp quality on one of cable terminals? Any diy crimps in the system?

[Zachalanche]

The ends in question here are the only ones that i didn't crimp. I just used off the shelf battery cables inside the box, and thats where most of the voltage drop is.

[Zachalanche]

The ends in question here are the only ones that i didn't crimp. I just used off the shelf battery cables inside the box, and thats where most of the voltage drop is.

[79 Camaro]

On a couple of my hot rod projects I mounted the battery in the trunk. From the battery to bulk head connectors and the forward to the engine. Both pos and neg. I don't care for the off the shelf battery cables. I use 00 welding cable from places like NAPA. As I was told by an electrical engineer the finer the wires in the cable less voltage loss. Crimp my ends using the cable ends you can buy any where and heat shrink tubing. Never had a failure.

[dhutton]

I've been doing more investigation, doing voltage drop tests segment by segment. I found that my highest voltage drop was in the battery box. I don't know if it's the positive cable or the connection where it passes through the box. but when I measure voltage drop from the positive terminal to the lug on the outside of the battery box, I get .48 V which is significant. Sadly, this means that the improvement I will get going to the larger cable won't be as much but running the new cable direct to the battery rather than the bolted connection on the side of the box should help a lot.


Maybe I should have used some kind of bulkhead connector rather than a pass-through bolt.

Are those bolts anodized or plated?

[Zachalanche]

No, they are brass. More conductive than steel, but not as good as copper.

[DualQuadDave]

All the trunk mount/remote mount batteries I have done and had any issues with were ground related. Add grounds everywhere, motor to chassis, battery to chassis. If you want to cut the bull****, run ground straight to the block outside the car(yes, it'll cost $$$ since it's a lot of cable, but maybe reuse your old positive) and leave the positive in the car and try it. Will either fix the problem completely or if the problem still exists, it's not the negative. FYI, Bimmers have the battery in the trunk/undercar, as well. Maybe junkyard and grab their power system.

What group size is that battery? Looks small in the pic, but hard to tell. You can't just go by the CCA, big motors need big batteries unless you go Li-ion.

[Zachalanche]

group 24

[TANKMASTERJ]

Zach
Just mic the wire. 2 ga. Is .2576. googl a chart for wire ga
Diameter and it will give you all of them. Of course we are talking the actual conductor measurements.
Jason