Total loss ignition system and Lithium Battery

Hey All,

Besides from the obvious increased risks of fire in the lithium batteries, is there any reason why i might not want to use one? The intent is to reduce weight from a lead acid battery and have a higher resistance to voltage drop when running up to 6500rpms. Also, space is pretty tight on the sidecar. Currently, the last track day, i saw voltage readings that went as low as 10.4v somehwere in between 5000-6000 revs. I have little experience in using lithium batteries but from what i can tell, the voltage remains higher than a lead acid under load. Current ignition circuit is points/coil with condensor on the Atlas outfit i'm running.

Looking forward to the replies,

Connie73 said:

Hey All,

Besides from the obvious increased risks of fire in the lithium batteries, is there any reason why i might not want to use one? The intent is to reduce weight from a lead acid battery and have a higher resistance to voltage drop when running up to 6500rpms. Also, space is pretty tight on the sidecar. Currently, the last track day, i saw voltage readings that went as low as 10.4v somehwere in between 5000-6000 revs. I have little experience in using lithium batteries but from what i can tell, the voltage remains higher than a lead acid under load. Current ignition circuit is points/coil with condensor on the Atlas outfit i'm running.

Looking forward to the replies,

Click to expand...

Most LiFePO6 Lithium batteries meant for motorsports will shut off if the voltage gets too low. They will hold their voltage much longer. So, it depends on how long a run and how much time you have available to charge between runs whether they will work for you or not. If the runs are pretty close together then you probably want two of them so you're not trying to charge too fast.

marshg246 said:

Most LiFePO6 Lithium batteries meant for motorsports will shut off if the voltage gets too low. They will hold their voltage much longer. So, it depends on how long a run and how much time you have available to charge between runs whether they will work for you or not. If the runs are pretty close together then you probably want two of them so you're not trying to charge too fast.

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Thanks Greg, we have at minimum an hour between races, sometimes longer. Am i correct in that i shouldnt see so much voltage drop? I worry that the voltage gets to low as things speed up. We have a new circuit that is a longer than our usual so the race might be 10mins plus warm up/sighting lap..

You might want to reach out to the battery suppliers. When I discussed using a Shorai battery for this application they were adamant that it was not suitable !

Lots of racers do use various lithium batteries though, so def worth asking around.

Nigel, when I asked about this, you told me I had not researched very well. My main problem was finding a lithium battery, the same size as my lead acid battery. I thought I had found one a couple of days ago, but the measurements seemed strange - might have been in centrimetres they were three numbers with asterisks between them. It was 12volt . - https://www.wattcycle.com/products/wattcycle-12v-100ah-group-24-lifepo4-battery

I got to thinking about battery weight when I removed my AGM battery this week due to what seems to be a cell failure. All too common and in past few years battery life is short. Lithium really seems worth looking into but how is their failure rate? This is for road service
not racing.

Good question. One that I thought about for years without finding answers. We have a pair of 250 cc racers with total loss ignition. No starter motors, Electronic ignition. Revving 12000. Currently using lead standby batteries 4 to 5Ah. Lighter and smaller than comparable motorcycle batteries. In one of them same battery 8+ years. Ignition fails when voltage goes under 11.9V which never happens if charged between half an hour rides.
Potentially might save 1 kg with a Lithium battery. Can't figure out what size needed though.

Connie73 said:

saw voltage readings that went as low as 10.4v

Click to expand...

Why is it doing that? Is it a poorly installed circuit or a duff battery ? A good lead acid battery should supply the 2 or 3 amps needed for points/coil ignition without voltage collapsing.

Does your apparent voltage drop affect how the engine runs? If not, what are you trying to fix?

Add in, for road use, LED lamps. This saves quite a few amps. So the need for a 9-10 AH battery is likely now less too. If you are still innocent of the electric leg, I think lugging around the old spec battery just not
required. However, and there always seems to be a however, if your alternator packs up, you will not be so happy trying to get home even
in daylight.

Onder said:

I got to thinking about battery weight when I removed my AGM battery this week due to what seems to be a cell failure. All too common and in past few years battery life is short. Lithium really seems worth looking into but how is their failure rate? This is for road service
not racing.

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I was running one on the Ducati bevel for a while. Worked great, until I rode the bike into work through quite a bit of stop & go traffic. The bike simply stopped, fortunately next to a petrol station where I could park it and chain it to a large lump of iron.
Lithium batteries all seem to have a very flat voltage curve until they shut down. There's no warning as per conventional batteries, where the lights get dim(mer!!), or it starts misfiring. All great then nothing, the voltage simply drops off a cliff.

For a road bike, you really do need a modern regulator and a charge / discharge indicator. The voltmeters normally uses on bike are simply not good enough to show the approx 1.5V difference from full to empty.

I went back to an AGM battery and live with the extra weight - it would be far more beneficial to both the bike and myself to lose a couple of kg on the rider instead!

Connie73 said:

Thanks Greg, we have at minimum an hour between races, sometimes longer. Am i correct in that i shouldnt see so much voltage drop? I worry that the voltage gets to low as things speed up. We have a new circuit that is a longer than our usual so the race might be 10mins plus warm up/sighting lap..

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A lead/acid battery in good condition should not do that. If a 9ah battery, you ought to be able to draw the 2-3 amps you need for around 3 hours of racing. A lead/acid battery will continue providing current all the way to about 10.5v and pretty smoothly loses capacity. A Lithium stays at a higher capacity longer but somewhere in the 12.5v range shuts down and provides nothing. The chart below is for older Lithium-ION batteries without an internal shutoff and not for LiFePO4 powersports batteries - can't find the chart I wanted to show.

More important than voltage would be the current being drawn from the battery. To test, you must have an analog meter as a digital will not cope with the pulsed current draw.

A lead/acid battery that is going bad will seem to take a full charge, but fall off very quickly - AGM will as well. If a translucent battery case, hold it up to light and see if you see white deposits in the cells. If so, get a new battery. Also hard discharging/charging can warp the plates and also reduce the life.

BTW, do not turn the power on (connect the battery) until just before starting. The current draw with a closed set of points and not running is much higher and is wasting your battery capacity.

Talk to AntiGravity Batteries and get some useful information about LiFePO4 batteries used for motorcycle racing.

“A lead/acid battery that is going bad will seem to take a full charge, but fall off very quickly - AGM will as well.”

This has been my experience with almost every failed lead acid battery I’ve had, and seems a usual failure mode for batteries that have spent considerable time on a battery tender. The quick test is to check voltage with no load and then apply a load- such as a switching on a headlight. If the voltage drops from its previous value by much more than 3/4v your battery is toast.

I pull all the bike batteries in the winter and they live in a “battery farm” in the shop. I have a single tender and move it from battery to battery every few days so none of them are left on the tender continuously.

I’ve only a single lithium battery in the fleet and it just stays on the bike- it seems unaffected by cold storage and is now 8 years old. That bike is a 1970 A65l and the battery doesn’t do a lot beyond making the lights bright at idle and ensuring there is a spark at kick over.

This in no way addresses the original question other than to suggest your previous lead acid battery was faulty. I should think lithium unit on your outfit would work fine other than the chance of its voltage cut-out shutting you down. I’d even wager a portable tool battery and shoe might provide sufficient energy to run your system and have the advantage of being quick change as well as powering your pit tools. Do you have any idea what your actual amperage draw is at full load?

Triton Thrasher said:

Why is it doing that? Is it a poorly installed circuit or a duff battery ? A good lead acid battery should supply the 2 or 3 amps needed for points/coil ignition without voltage collapsing.

Does your apparent voltage drop affect how the engine runs? If not, what are you trying to fix?

Click to expand...

We only have a space for a 4ah battery at present and searched for similar sized batteries dont yield much more aH's. We used to run a Joe Hunt but the new cases would have needed to be machined away so we went this route. Mainly saving weight, although not much admittedly, whilst also getting more volts for a better spark. New Battery and rewired circuits so im unsure why its dropping down that far.

marshg246 said:

A lead/acid battery in good condition should not do that. If a 9ah battery, you ought to be able to draw the 2-3 amps you need for around 3 hours of racing. A lead/acid battery will continue providing current all the way to about 10.5v and pretty smoothly loses capacity. A Lithium stays at a higher capacity longer but somewhere in the 12.5v range shuts down and provides nothing. The chart below is for older Lithium-ION batteries without an internal shutoff and not for LiFePO4 powersports batteries - can't find the chart I wanted to show.

More important than voltage would be the current being drawn from the battery. To test, you must have an analog meter as a digital will not cope with the pulsed current draw.

A lead/acid battery that is going bad will seem to take a full charge, but fall off very quickly - AGM will as well. If a translucent battery case, hold it up to light and see if you see white deposits in the cells. If so, get a new battery. Also hard discharging/charging can warp the plates and also reduce the life.

BTW, do not turn the power on (connect the battery) until just before starting. The current draw with a closed set of points and not running is much higher and is wasting your battery capacity.

View attachment 116414

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We currently have a 4ah fitted due to space, but from what im reading on your post, it still shouldn't drop like that. Maybe i should investigate a resistance in the dead man switch or other circuits (Ign Sw, Condensor, terminal connections, etc) although i would have thought that might have been more apparent by now. The smaller lithium battery i researched has a BMS so it shuts off.
I have an analog dc ammeter to get a reading from the battery, i might try and put it inline once i get all the other things done.
Battery has only ever been on a 6 stage charger so it should be still ok.
Thanks for the graph, confirmed my thoughts.

Connie73 said:

We only have a space for a 4ah battery at present and searched for similar sized batteries dont yield much more aH's. We used to run a Joe Hunt but the new cases would have needed to be machined away so we went this route. Mainly saving weight, although not much admittedly, whilst also getting more volts for a better spark. New Battery and rewired circuits so im unsure why its dropping down that far.

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If you’re running a sidecar outfit then why not use the JH mag that fits on the points housing?
The only downside to these is their vulnerability to a low side and limiting the ground clearance… neither of which is an issue with an outfit.

Connie73 said:

We currently have a 4ah fitted due to space, but from what im reading on your post, it still shouldn't drop like that. Maybe i should investigate a resistance in the dead man switch or other circuits (Ign Sw, Condensor, terminal connections, etc) although i would have thought that might have been more apparent by now. The smaller lithium battery i researched has a BMS so it shuts off.
I have an analog dc ammeter to get a reading from the battery, i might try and put it inline once i get all the other things done.
Battery has only ever been on a 6 stage charger so it should be still ok.
Thanks for the graph, confirmed my thoughts.

Click to expand...

So, a 4ah battery ought to get you two races if fully charged and in good shape but I would give it some charge between races to be sure. A small Lithium would do better. BTW, in Lithium batteries, they specify AH so you can compare, but it's nothing like lead/acid or AGM if you read the fine print. A Lithium about the same size as the battery you are using has much more actual capacity.

Any tiny resistance in any component in the circuit will essentially "steal" power and depending on where you measure the voltage can make testing very confusing.

I attempt to explain that here: https://gregmarsh.com/MC/ViewPDF.aspx?key=uvd

Not sure what your actual size limitations are, but here are a couple of size examples.

An 8 cell AG-801 lithium-ion battery is 4.37x2.37x3.75" with 11ah (PbEq) 5.5ah actual, 70.4 Wh
A 4 cell AG-401 lithium-ion battery is 4.37x1.37x3.75" with 6ah (PbEq) 2.6 actual, 33.28 Wh

Risk of fire would only be in a crash where the wiring shorted out. I have no idea how often that happens. I've crashed a few times on the street during my lifetime, but I've not experienced an electrical short as a result.

You'll need a charger that supports lithium-ion batteries. A regular lead acid/agm charger left unattended on a lithium-ion battery would be a smoke show and potential fire.

The lead-acid battery which I use is quite small, and the last time I raced, I had three races and two practice sessions over a weekend without recharging. What I do not like about lead acid batteries is, if they are not continually trickle-charged, they sulphate-up and fail. I have been looking for lithium-ion batteries, but the computerised aspect of their charging cycles is a worry. In Aldi supermarkets, there are cheap lithium batteries with charger. But the terminal arrangements would be difficult. Also they are 20 volt, so a ballast resistor might also stuff things a bit.
I would like to be able to start my bike at home, but once the battery has been filled with acid, it must be continually trickle charged. I have thought of buying a solar powered charger, so I would not have to keep buying batteries. I don't like leaving acid-lead batteries on chargers where there are kids around. Sulphuric acid is very dangerous, even when dilute. I have worked with nitrating acid which is a combination of oleum and nitric acid - it is quite frightening, especially when it is above head-height, refluxing in a still. Oleum is sulphuric acid pumped up with sulphur dioxide. It is used to dehydrate in a nitrating process to make explosives.
I do not let kids near chemicals, of any sort. My laundry cupboard used to have kiddie-lock, but my step-daughter broke it. The kids wanted to mix the bleach with the white spirit.

wattcycle 12v 100ah lifepo4 lithium battery
















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marshg246 said:

So, a 4ah battery ought to get you two races if fully charged and in good shape but I would give it some charge between races to be sure. A small Lithium would do better. BTW, in Lithium batteries, they specify AH so you can compare, but it's nothing like lead/acid or AGM if you read the fine print. A Lithium about the same size as the battery you are using has much more actual capacity.

Any tiny resistance in any component in the circuit will essentially "steal" power and depending on where you measure the voltage can make testing very confusing.

I attempt to explain that here: https://gregmarsh.com/MC/ViewPDF.aspx?key=uvd

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Measured the current draw with the Ign on and it was 3a. Note this was just rotating the engine by hand. Might be close to the limit for the 4ah battery when running?
I ordered a cheap lithium battery and charger to have a trial with so will see how it tests on the bench and the track. day.