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November 9th, 2016, 12:54 AM   #1
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Electric starter power/current spec and usage

Hi all,

I'm trying to figure out a good battery solution. I'd like to try to understand the power spec and real-world power usage of the electric starter.

It looks like the starter only pulls 50A max? I'm not sure though!:

The 2012 570 manual specifices a "E-START. ENGINE CPL. 0,45KW 08". Googling the starter model, I find statements of "OEM SM14 MITSUBA", and specifications for those to be 460W.

I assume that is at 12V nominal. 460W at 12A draws ~38.3A, and indicates a load impedance of of about 310 milliOhm. (Very roughly and naively calculated.) If we imagine that the absolute maximum voltage we'd get from the battery would be 15V, that could push up to ~48A through that load, which would be about 750W of power into the starter. (Surely the starter is specified in terms of electrical input power rather than mechanical output power?)

So I'm wondering if this could be correct?

Battery recommendations are usually given as upwards of 100A burst capacity (CCA). If the real-world current draw is only half that, I imagine that the tendency towards more burst current capacity is a quest towards less internal resistance -> less voltage drop under load (less "sag") -> the battery is better able to really deliver the rated starter power. But I may be mistaken.

I can't find more detailed specifications on the starter motor. It seems to be the same starter motor that the DR-Z400 has.

Any guesses or information?

It's very hard to find the exact battery ready-made which I think is best for these bikes: A123 M1B-spec 26650 cells, 4S1P configuration, with a protection circuit which protects against over/undervoltage, balances the cells, and still has enough maximum current capacity. EarthX is close, but their current smallest model is 4S2P and are therefore too big to fit in the DRZ airbox (and also too big for my wallet atm). I did contact EarthX and got a very good reply stating that they will indeed be releasing a 90mm * 50mm * 50mm battery in the coming months / quarters, which sounds like the perfect fit. And IMO 4S2P is actually a good idea and I might get one for the 570. But in the meantime ... it looks like batterspace.com has the right cells for sale for a good price, can spot weld the cells together (this is the part I hate doing myself), and they may have a suitable protection board as well ... with a 100A burst capacity. And that's why I'm looking to understand this

Incidentally I'm also quite interested the idea that Bushie mentioned in a thread here, to tap power to the starter itself from a protection board bypass, but to power the rest of the bike through the PCB, including the starter relay. I don't fully grasp the electrical topology to have a good feel for how exactly it would be done It does make sense to me though.
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November 9th, 2016, 07:17 AM   #2
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my question would be: what is the overall goal you are trying to achieve?
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November 9th, 2016, 07:41 AM   #3
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Finding out what burst current capacity the protection circuit in the LiFePO4 battery needs to have

In order to buy or build a sub-$100 battery that starts any Husaberg and lasts for years.
Thanks from jon andersson and Damo W
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November 9th, 2016, 02:25 PM   #4
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more than my pea-brain can handle right now
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November 10th, 2016, 12:52 AM   #5
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I'll write a digest when I know more

FWIW batteryspace.com seem very good to deal with. Very friendly and competent service.

(Looks like A123RC.com are having operations problems - I cannot email them; emails always bounce back.)
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November 11th, 2016, 01:11 AM   #6
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Kinda turning the thread into a sideways-topic battery / electrical research infodump / monologue thing,

but it looks like Hangtimes.com NoBS batteries are good value. No protection board but known-good A123-brand M1B-type cells, useful connector options, good spot-welding on the cell tabs; $120 for a 26650 4S1P w/ Andersson connector: NoBS Batteries A123 Rx Turbine and Ignition Packs

Batteryspace.com will assemble low-volume packs like that for $130 or so ($65 full assembly fee). Will also spot-weld the cells for $20; If spot-welded cells and connector components are bought, then a pack from them costs $85 and you finish assembling yourself. Looks like the cheapest option to get pre-welded packs with good cells. (I don't mind doing the cable/connector soldering. It's heating the cells that sucks. It's a terrible feeling, haha.) These cells: A123 System High Power Nanophosphate LiFePO4 26650 Rechargeable Cell: 3.2V 2500 mAh, 120A Rate, 8.0Wh

I kinda need a flat pack, but Batteryspace sell a square pack for $89. Not a bad deal at all! The pack is a bit armored as the cells are in a cell holder casing (good). It's got screw connectors instead of Anderson but can be customized; $10 for a JST-XH balancing connector but not sure if an Anderson power connector can be added or about price. This may be the best deal actually; Depends. Hmm. Nanophosphate LiFePO4 26650 Power Sports Starter Battery: 12V 2.5Ah (32Wh, 120Rate, A123 System cells) ... I should make a cardboard model or sth and see if it fits in the DRZ airbox / 'Berg battery hole.

Re. connectors and current use: Anderson SB50 or PP75 connectors look to be sufficient for the job - from the datasheets it looks like both types handle upwards of 100-120A burst (- and that at quite high voltage? Wouldn't that stand to run even hotter than the 12V operating range we're looking at? Or is the heat in the connector defined only by the current flow?)

I've found some info that the DRZ will draw up to 80A in the very first moments of starting (same starter motor; probably easier to start than most 'Bergs?) ... but I can't find the link again atm. dammit!

And this looks like the battery charger to get: http://hitecrcd.com/products/charger...arger-/product ... about $50-$60 online, charges and balances basically any battery chemistry (up to like 15 cells for some types?), from li-ion to SLA to LiFePO4, and also takes low-voltage DC as well as international AC voltage as input. Very convenient package.

- All this digging also shows me what a clever product EarthX are building, and how well they really are priced for a waterproof 4S2P battery with a full-featured protection circuit!! Can't wait for them to get out the smaller/cheaper one.
Thanks from Damo W

Last edited by tourist; November 11th, 2016 at 01:30 AM.
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November 11th, 2016, 03:19 AM   #7
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Hi tourist, quite a bit of research you've been undertaking! Good on you.

With regard to your connector suitability, Joule's first law, also known as the Joule–Lenz law, may be of interest to you. It states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current.

So regardless of the voltage, if it will handle upwards of the expected current draw, you should be right. That's how I interpret it anyways...

Keep up the great work

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November 11th, 2016, 03:33 AM   #8
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And shame I don't run electric leg on my bikes. I have a nice inductive ammeter that I could use to measure actual current draw from the starter. I'll see if I can bench test it, albeit without load, just to see what it indeed draws as a guide. Wonder if I should try and grab the pinion with the large multi grips to simulate?! But I expect around that 60-80A. If I remember correctly, and it's been quite a long time since I studied, but when choosing a battery, the general rule is to double the expected starter current draw. So the current Lithium batteries are rated 130CCA

Damo
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