ST1300 Minimum Main Relay Voltage?

Really off the wall question, I'm on the road so I'm hoping someone out there happens to know or can test maybe? At what voltage does the main relay drop out on the ST1300? I.e. Key=on bike=dark?

The story, for the curious: I forget and leave my bike on occasionally, usually it's when I have a plan to go right-back-to-it, we all know how that works out. A couple days ago I ended the day around 5pm-ish.. Went inside and never went back. Next morning I come out 10:30ish am, bike dead, I'm Fontana and I need to be on the other side of LA right now. Jump start the bike, hustle all the way, watch the voltage.. starts out 14.2(!) then drops 13.8-9 stays there for awhile and then drops to 12.8 and I stop watching. Nothing to be done anyway. 70mi, and a very naughty few minutes later I'm where I need to be and shut it down. shows 12.8v. 5mins later starts right up no problem, and has behaved flawlessly since, like nothing ever happened. It probably did get a little bit of charge time out to Palm Springs after a couple more stops but i am still sort of surprised it seems so 'fine'. Perhaps I have Yuasa PTSD?

Battery is a BTL35A480C so it's always spun up the ST about instantly, pretty sure it caught before a full 360•. It may be a hair slower now, but that could also be in my head. I'm just trying to get some kind of sense how much damage I may have done while on the road. I'm pretty sure I'm in the clear but knowing it drops out at 10.5v vs. 6.5v would sure be nice,. From my experience with automotive relays they can be all over the map despite what it says on the tin. The battery is about 2 years and 40K miles old.

Drop out is usually about half the nominal, but getting initial engagement is higher. Sorry, don't have one to test.

So its not 100% clear, but I think you killed the battery by leaving the bike on overnight, right? Or did it just die for no reason?

aob said:

Jump start the bike, hustle all the way, watch the voltage.. starts out 14.2(!) then drops 13.8-9 stays there for awhile and then drops to 12.8 and I stop watching.

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when I read this it sounds like you're watching the voltage while riding, is that correct? If so, when the bike is running I would think you should see 14.2v pretty much all the time, dropping to 12.8 could be a sign that the alternator isn't working properly. Unless the 1300 is different than other bikes I've owned, maybe this isn't abnormal for the 1300.

aob said:

I'm just trying to get some kind of sense how much damage I may have done while on the road.

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Not sure what kind of damage you're referring to. If your alternator is OK, then once its running the battery will recharge as you ride. Sounds like the battery has recovered to normal again, so you're probably OK until the next time you leave it on overnight. Riding and charging it isn't going to harm the battery, but killing it stone dead multiple times will eventually take its toll.

aob said:

Main Relay Voltage

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I don't know what you're referring to by "main relay" voltage, as my 2003 ST1300A does not have a main relay that I'm aware of. However, if your voltage measurements quoted are battery voltage, you should be fine. My bike was on a battery tender last night, unplugged it earlier today. I went to the cave and checked it a few minutes ago and it read a little less than the 12.8V that you observed. The 14.2V that you observed after starting the bike sounds just right to me as the alternator is recovering the battery from what it lost when starting. The gradual decline in voltage is what one would expect as the battery is recharged. My advice would be to not lose any sleep over your concern of possible damage - you haven't hurt a thing.

Don B said:

The gradual decline in voltage is what one would expect as the battery is recharged.

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Is that how the alternator works on the 1300? On the 1100 I think its putting 14.2 to the battery all the time when RPMs are at normal range for riding, and about 13 and change at idle. Don't have a meter installed on the bike, but that's what I've noticed with a multimeter revving it in the garage with a strong battery. But come to think of it, garage maintenance only lasts a few minutes, so I can't say what the charging system does after riding for a while. Could any of you with a voltmeter installed on your 1100 or 1300 comment on this? thanks.

The voltmeter on my ST1100 does not show any decrease in voltage put out by the alternator as the battery is charged.

dwalby said:

Is that how the alternator works on the 1300? On the 1100 I think its putting 14.2 to the battery all the time when RPMs are at normal range for riding, and about 13 and change at idle. Don't have a meter installed on the bike, but that's what I've noticed with a multimeter revving it in the garage with a strong battery. But come to think of it, garage maintenance only lasts a few minutes, so I can't say what the charging system does after riding for a while. Could any of you with a voltmeter installed on your 1100 or 1300 comment on this? thanks.

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I can't say for sure if that is how the charging system on the 1300 works, as I don't have a digital meter connected to my battery so I can monitor battery voltage any time I like. I was basically just making some assumptions in my previous post, so it may wel be that the alternator charges the battery at 14.2V all the time the engine is running.

Since you're using a Lithium Iron Phosphate (LiFePO4) battery, my knowledge is lacking. I would call or write to Delran and ask them what you're asking here.

The behavior you describe about what you saw your volt meter showing sounds like the battery was being charged correctly, for a LiFePO4 battery.

First question. Do you have Halogen (incandescent) lights or have you converted to all leds?

The halogen bulbs will completely run down your battery.
If you converted to LEDs. The Leds will shut off between 7 and 4 volts and essentially save your battery. (hidden benefit of going all leds)
The battery that you listed is a Lithium battery which does not like to be fully discharged. The fact that you were able to recover the battery must mean that it did not get fully discharged.
Bringing a lithium battery out of a fully discharged state is a delicate process and should be done slowly (at least according to theory) so you might be running on borrowed time.
The ST1300 alternator will fully recharge the battery in the 70 miles that you drove. Voltage does not tell you much, you really need an amp meter to know what is going on.
The alternator is voltage regulated but the current will be very high into the dead battery and slowly drop off as the battery approaches full charge.

I have (higher power)HIDs, everything else is LED. In doing research I came across an implication that the battery itself may have a drop out at 10v. In fact I believe that's what happened and what saved the battery from significant damage. One reason I believe this is just the amount of light the bike puts out, as it got dark out if it was still 'on' someone in the house would have noticed.

My STs charging behavior has been the same at least since I installed the voltmeter at 20k ish miles, now 94k. The difference this time was an initial longer period at a higher voltage.

Voltages today:
parked, off, cold: 13.6
parked, off, warm: 13.8
parked, on, cold, not running: 12.6v
parked, on, cold starting low voltage: 11.6v (very briefly while cranking)
parked, on, cold idle: 13.2v

Bike still goes through the same routine after start up, when running (not idle). High voltage 14.1 initially, then a longer period around 13.8-13.6 then down to 12.8-13.2 depending on conditions.

I personally would not want a charging system that put 14+v into a 12v battery continuously.

I suspect what I have is an adequate but incomplete charge. The cells have not yet had an opportunity to be recharged to saturation. LifePOs have a very flat voltage curve. Hopefully tomorrow's run to SF from palm springs will help.

Thanks everyone, I think I am out of the woods on this one. Hope this is helpful for someone else.

If anyone else is tired of battery issues i can't recommend that deltran beast enough.

one other thing to mention, the voltmeter is at the very end of a long sub harness and on <18ga iirc, so the numbers are likely pessimistic or worst case scenario for the system as a whole.

HIDs will shut off the same as leds since hids require very high voltage to run. the High voltage regulator has a low voltage shut of circuit. If the battery voltage drops too low it will shut down saving the battery.
Battery voltage will be different with temperature. The ST charging system is designed for lead acid batteries not lithium batteries. However lithium batteries work to a higher voltage so the ST system under charges the battery so all is good. If the lithium battery got over charged it would not be pretty! Boom and flames....

14.x volts is safe. Voltages above 16.6 volts takes you into the danger zone.

spiderman302 said:

However lithium batteries work to a higher voltage so the ST system under charges the battery so all is good. If the lithium battery got over charged it would not be pretty! Boom and flames....

14.x volts is safe. Voltages above 16.6 volts takes you into the danger zone.

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When it comes to LiFe the danger is not so much.

I've overcharged, I've over dis-charged, I short circuited discharged 20amp/hr battery in seconds (ever see a battery buss bar glow red?) and I sliced the side off of one cell with a table saw. I haven't tried it but I saw a 16d nail driven into one.

No flames on any.

A few ruined cells.

LiFe is not like any of the Lithium Manganese Cobalt (various combinations) dangers. Not the energy density either... but that's another story.

When it comes to rechargeable lithium batteries, one should be careful. Just because you have not been able to create fire with one does not mean that they will not.
They claim the Li Iron phosphate to be safer than Li-ion but not by much. It is the excess heat that gets generated when over charging or fast discharging (short) that will ignite the lithium.
All the data sheets caution not to exceed 130 degrees C because the lithium will become unstable. At 177 degrees C lithium will ignite! I have seen and done testing that proves that. (the fun part of my job)

Keep the battery cool and all will be good.. Tesla uses thousands of 18-650 batteries in series/parallel so that they can run liquid cooling around each cell...

Just be aware.

Voltages above 16.6 volts takes you into the danger zone. At 16.6 volts the Lithium battery is fully charged so any energy that is put into the battery turns into heat and the battery starts heating up. This is why the battery charger will switch to a float state to prevent over heating the battery.... This is why Lithium batteries have a built in thermal fuse that will open if the battery gets too hot..

Check the harness connector on left side of bike that connects alternator sub harness. Mine had burned from high resistance and resulted in low charging voltage. I suspect the extra load of recharging your dead battery may have finished this connection of if it was weak to start with.


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