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Discussion Starter · #1 ·
Hello all new member here, just a quick question I have had my 790 for about 4 months it's a 2018 with 6000 miles, the only mods I have done is a SC project exhaust the bike was going great until the other morning when I started it and I got the message" immobiliser failed " the engine stayed running and I got to work about 5 miles away, after 10 hours started the bike and no errors for 5 minutes then the error appeared again, got home no problem.
I have read a posts here and have seen it could be the battery, I'm showing 11.8v. The bike stays on a optimate when not being used.
My question is do I need a new battery?
Many thanks
 

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If it’s still the original battery you’ve done well my first one lasted 125 miles, more than likely it is the battery.
 

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Most battery sales places(at least around me) will offer a free battery test. A load test should show your battery is failing. Try witness the test though because they are hoping to sell you a battery.
 

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Discussion Starter · #7 ·
Most battery sales places(at least around me) will offer a free battery test. A load test should show your battery is failing. Try witness the test though because they are hoping to sell you a battery.
Thank you that's a good idea, there is a battery center just down the road
 

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Discussion Starter · #10 ·
Thanks all for the helpful response to my first post, I was a little disappointed when I got the error message as I traded my aprilia dorsoduro for the KTM and one reason was the world of pain I went through with the Aprilias immobiliser.
 

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The bike stays on a optimate when not being used.
I am going to fly in the face of generally accepted lore. But my experience of battery "maintainers" is less than positive.
IME - forcing an aging battery to full charge 24*7 weakens it further. There is a notable Peukert effect through doing so.
And it's especially visible if the vehicle is used fairly often. Batteries should be allowed to discharge.
Unless you have a very fast parasitic discharge a battery should last a week. Even two, though the 790D battery is not a big one.
It's just an opinion. But you're better off letting the battery sit and occasionally charging.

Also while I am a fan of LiFePO4 (Lithium) batteries - they are NOT ALWAYS a good choice where alarms etc are fitted.
 

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Discussion Starter · #12 ·
I am going to fly in the face of generally accepted lore. But my experience of battery "maintainers" is less than positive.
IME - forcing an aging battery to full charge 24*7 weakens it further. There is a notable Peukert effect through doing so.
And it's especially visible if the vehicle is used fairly often. Batteries should be allowed to discharge.
Unless you have a very fast parasitic discharge a battery should last a week. Even two, though the 790D battery is not a big one.
It's just an opinion. But you're better off letting the battery sit and occasionally charging.

Also while I am a fan of LiFePO4 (Lithium) batteries - they are NOT ALWAYS a good choice where alarms etc are fitted.
I didn't know that, the problem I have is I am a fair weather biker and English weather being what it is I never know how long my bike will stay in the garage, do you know anything about gel batteries?
 

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You are extremely lucky the original battery lasted that long, mine was Chinese and lasted about 6 months.
 

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Gel are still Lead Acid. But a ******* to rejuvenate if they get dry.
I hate sealed lead Acid batteries - ime - 80% plus of dying M/C batteries just need a bit of distilled water.

Here - For your entertainment - a quick note I drew up last week for a UK mate recently emigrated over to Spain.
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Okey Dokey Lead/acid vs "Lithium"

Some of this is theory and some experience.

It's all really down to chemistry. And how it allows electrons to be held (stored) and moved.
Batteries (all batteries) are rated by Cycle Discharge. This is governed by chemistry.
Forget the CCA thing - it's just a number. And it's sort of made up.

And first off let's clear up "Lithium". Lithium itself is only part of the chemistry, its a metal - There are various other ion-compounds that work with Lithium (Li), but some are better than others. The current undisputed king is Iron Phosphate (FePO4). It's safer and less prone to charging damage. The Li batteries used in phones etc have a chemistry that is actually more energy efficient - but far less stable and less long-lived.

A Lead acid "cell" can store at about 2.2V - Hence a "12V" battery has 6 cells in series - 13.2V.
A Good LiFePO4 cell holds 3.3V - hence 4 in series comes to 13.2V.
This is a very happy accident - with other Li chemistries it's not.

The amps available depends on the number of cells in parrallel and or their phiscal dimensions - Chemistry independant.

"Starter" rated batteries on modernish Internal Combustion vehicles have to deal with a couple of things.

1) Starting - This requires a pretty big surge of energy for a short time.
2) 24*7 component low power constant drain.
3) Less importantly - it stabilizes the alternator output. Most modern R/R's do this pretty well once the alternator is charging - but in traffic the circuit voltage could other wise be too low.

There are also "deep charge cycle" variants of Lithium and lead acid - Forget them.

Lithium Batteries can be thought of as "dry" though in fact they're not. But the tiny amount of liquid inside does not produce gas - so they don't need to vent.
Lead/Acids do need to vent - Sealed batteries are water tight but not air tight.

So what's the hype. Lithium metal is light. Lithium batteries have very little liquid. Lead is NOT light and acid by definition requires water to work.
And for a given amount of electrical storage (Joules of Energy) - LiFePO4 is lighter. But also more expensive.

But now the fun bit. LiFePO4 chemistry can discharge up to 3 times as fast as a lead acid. I said "CAN".

A good lead Acid is lucky if it has a short term 15 (discharge) Cycle rating - So a 20ampHour battery could just about discharge 300amps.
A good LiFePO4 has a 20 cycle rating with short term rating closer to 45. So a 7.5aH can pump out close to 360amps for a couple of seconds.
I have some early 8aH cells that are 70 Cycle rated - these are frankly dangerous - They would stop your heart.

The reality is that these numbers can be compromised by construction of the battery itself - including material purity.
But using less materials keeps the cost down - though still not as cheap as lead!. And may lead batteries are not PURE lead either.

If a starter is 1.2KW - it needs (on paper) 100amps at 12Volts. The reality is you cannot discharge a battery at 100% capacity however - there are other components like the ECU that simultaneously require a stable power supply. More in this in a bit. My R.O.T. - double it and add a bit. Triple to be safe.

Brilliant you say - let's stick in a 7.5aH. And if we were ONLY talking about starting a track bike, then fine. BUT we have that 24*7 drain to think on.
If you have something drawing (as an example 0.5 Amps - then a 20aH battery will last 40 hours approx before being drained. A 7.5aH will only last 15.
Lithium becomes a liability rather than a plus.

A plus for a good LiFePO4 is that its charge cycle rating is also high. So you can charge them up faster.

When discharging close to limit - Lithium based batteries tend to hold voltage and loose ability to flow amps. Lead Acid tend to flow amps and loose voltage. Depending on the vehicle itself, this can work either way. ECU's have a low voltage threshold. But tbh if the ECU says low volts it's not charged enough anyway.

Now an experienced based Downside.

Some are very sensitive to ambient temperature. This is an overall known problem with the chemistry, but some batteries are more prone to it than others.

If I leave my Lithium battery'd bike FULLY charged in (for example) my mum's garage overnight in UK spring. The battery will initially struggle. The trick is simply to cause some drain to the battery - i.e. lights - for a few seconds - then hit the starter. I had the same issue last weekend here. If the bike has lights that only come on when the bike has started - it matters!. The chemistry has to ramp up a bit.

This effect is FAR LESS prevalent in lead Acid batteries except at EXTREME COLD. Spitsbergen in Winter cold (when even Polar Bears hibernate)

Another Downside. Li batteries are NOT as resistant to over and under charging as Lead Acid.
Under charging will not be much of an issue real world as the ECU will have already stopped recognizing the battery - and you'd have had to recharge.
Over Voltage damage is possible and an over protected battery is strongly advised.

Lead Acids will boil dry if they overcharge. Be they liquid, AGM or Gel.

If it were me - I would fit a GOOD Lead Acid. YUASA is always a safe bet.

And buy a small jacket-pocket.sized Lithium Booster pack that you can keep inside - where you can occasionally check charge and it's warm. Stick it in your jacket when you walk down - and if you need it - it's there. I have a Noco booster pack (it's overkill sized though) and it keeps full charge for months.

Some have a harness you can leave attached to the bike battery so you don't have to (shock horror) lift the seat.

If you really want to go Lithium. Then get a GOOD ONE.

Make sure it uses A123Systems/Lithiumwerks chemistry cells. These will almost certainly be the standardized ANR26650m1B cell. Each cell being 3,3V 2.5aH. Because they are a standard cell the cell prices are dropping - but retail per cell is about 8euros (incl German VAT). They were closer to 10Euros. Some use the smaller 18650 cell - but need lots more. Other cells are out there - and are cheaper. But A123 are still after more than a decade - the best (OK except maybe Custom Tesla cells).

A good 7.5aH based on A123 with all BMS etc will be about 200Euros.

If I were fitting one to the 790Duke I might drop to a 5aH. On R3 or Guzzi - at least 7.5aH and tbh I'd feel safer with 10aH because I understand how they draw power. But on the whole - for my use - as things stand - I think I'd do the lead-acid battery and Li booster pack thing.

That may have helped - or maybe not.
*
 

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Thank you for taking the time to explain all this to us. It is interesting and valuable info.
 

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Thank you for taking the time to explain all this to us. It is interesting and valuable info.
You know you’ve been duped. He cut and pasted that off the internet. I suppose he gets credit for enough brain power to cut and paste it into the forum. :LOL:
 

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Hello all new member here, just a quick question I have had my 790 for about 4 months it's a 2018 with 6000 miles, the only mods I have done is a SC project exhaust the bike was going great until the other morning when I started it and I got the message" immobiliser failed " the engine stayed running and I got to work about 5 miles away, after 10 hours started the bike and no errors for 5 minutes then the error appeared again, got home no problem.
I have read a posts here and have seen it could be the battery, I'm showing 11.8v. The bike stays on a optimate when not being used.
My question is do I need a new battery?
Many thanks
I would replace battery. 11.8 volt too low for engine management computer. Given that you keep it on Optimate, as I do, you should get minimum of 13 volts, after charging and after riding. Battery not accepting full charge.
 

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This just happened to me as well. I found out at the moto shop that I needed a sealed lead acid battery, not a wet cell that you dump the acid into. The parts guy said it was because in the KTM the battery is tilted back instead of sitting vertical. Glad I brought the old one in with me to match it up, there's a couple different sizes of 12 series batteries.
 
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