Measuring remaining AH for Pulse electric trolling motor

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FatherOfMany
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Measuring remaining AH for Pulse electric trolling motor

Post by FatherOfMany » May 13, 2015 12:07 am

Hi guys, my first post here. I had it in the Battery Technology first, but then saw this forum so moving it.

I've just bought an Old Town Predator XL kayak, which comes with a 45lb thrust Minn Kota electric motor.
I'm in New Zealand, which is really just a big island between two oceans, so weather conditions change very quickly here and I wanted a motor on my kayak in case I get caught out there by bad weather.
The Minn Kota motor comes with this Maximizer technology which means that (when not at full throttle) it sends short pulses of electricity to the motor to control speed rather than just burning off energy with a coil. It's meant to give you up to 5 times more battery life, depending on what speed your going at.

Currently I have an el-cheapo 40AH LifePo4 battery from a previous motor, but I want to upgrade as this motor supposedly uses up to 42 amps per hour at full throttle, which doesn't give much running time.
I'm looking at getting a 100AH LifePo4 battery and would want to drain it to 70-80% to get as much time as possible on the water.
I've just installed a "Watt's Up" meter which gives you AH consumed, but someone commented that a watt meter is not very accurate with the pulse (Maximizer) technology.

So my questions are:
Is that correct? Will an average watt/amp meter (AH meter?) not be accurate with pulse technology? If not, how far would it be out? (I don't need 100% accuracy, but probably I want to know within 10% of actual remaining battery AH).
What can I use to check remaining battery power for LifePo4? It sounds like their voltage stays pretty solid until it's drained, so that might not mean much with LifePo4.

FYI, I haven't been out with the new kayak yet

Hope you can help. I have read what my little brain can consume about batteries and LifePo4 and whatnot over many weeks (starting before I bought the 40AH), but have no prior experience with electrical systems.

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Re: Measuring remaining AH for Pulse electric trolling motor

Post by amberwolf » May 13, 2015 4:02 am

FatherOfMany wrote: The Minn Kota motor comes with this Maximizer technology which means that (when not at full throttle) it sends short pulses of electricity to the motor to control speed rather than just burning off energy with a coil.
Then it is just a normal PWM motor controller like almost everything uses nowadays.
Currently I have an el-cheapo 40AH LifePo4 battery from a previous motor, but I want to upgrade as this motor supposedly uses up to 42 amps per hour at full throttle, which doesn't give much running time.
I think you mean 42Ah per hour. ;)

I've just installed a "Watt's Up" meter which gives you AH consumed, but someone commented that a watt meter is not very accurate with the pulse (Maximizer) technology.
Any watt meter should measure the total Ah and Wh thru it regardless of how you put it thru it, in pulses or continuous, as long as it has a memory that stores teh info if the pulses are at the battery side and go below it's minimum threshold.

If the pulses are at the controller/motor, then it makes absolutely no difference to the wattmeter, as it only sees battery current/voltage.

FatherOfMany
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Re: Measuring remaining AH for Pulse electric trolling motor

Post by FatherOfMany » May 13, 2015 12:46 pm

Thanks for the reply, Amberwolf!
amberwolf wrote:
FatherOfMany wrote: The Minn Kota motor comes with this Maximizer technology which means that (when not at full throttle) it sends short pulses of electricity to the motor to control speed rather than just burning off energy with a coil.
Then it is just a normal PWM motor controller like almost everything uses nowadays.
But you understand that it sounds very impressive to a layman like me, especially as I previously had a no-name brand motor that ate batteries for breakfast:)
amberwolf wrote:
Currently I have an el-cheapo 40AH LifePo4 battery from a previous motor, but I want to upgrade as this motor supposedly uses up to 42 amps per hour at full throttle, which doesn't give much running time.
I think you mean 42Ah per hour. ;)
Eh? More reading to do apparently. The Minn Kota website says it has a maximum amp draw of 42 amps. OIC, ok I read and I think I understand.
amberwolf wrote: Any watt meter should measure the total Ah and Wh thru it regardless of how you put it thru it, in pulses or continuous, as long as it has a memory that stores teh info if the pulses are at the battery side and go below it's minimum threshold.

If the pulses are at the controller/motor, then it makes absolutely no difference to the wattmeter, as it only sees battery current/voltage.
Thanks, that's encouraging. I asked the same of the Watt's up manufacturer yesterday and their techie had a similar answer, although he was a bit more elusive in his answer.

I'll give it a go as soon as the weather clears up around here.

Thanks again.

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Re: Measuring remaining AH for Pulse electric trolling motor

Post by FatherOfMany » May 17, 2015 12:54 pm

Out of interest, I took the kayak out for the first time yesterday and I had the Watt's Up meter connected right next to the battery. I was traveling at around 4kph (2.5mph) and with a total traveling time of 1:45, the meter recorded 17AH.

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Re: Measuring remaining AH for Pulse electric trolling motor

Post by blisspacket » May 20, 2015 7:11 am

Getting a read on voltages is important also. Record the voltage at the start; for longevity of the battery, folks say don't charge above 4.05 or somesuch. Ditto for longevity, don't drain below 3.5 volts or thereabouts. The voltage limits you choose will depend on your wallet, the demands of your children :P Then, with those two numbers as "limiters", determine how long a ride you get draining at 17 amps. And of course, recognize that a power up or down on any given outing will affect the numbers.

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Re: Measuring remaining AH for Pulse electric trolling motor

Post by LockH » Aug 14, 2017 6:08 pm

[Bump] Hey! Watts Up, "FatherOfMany"? (Guess two years later maybe Father to a few more...) Yer post on ES popped up in a search in this Watercraft sub-forum... the only thread that mentioned the "Predator". Greeting from one of the other colonies! (Canada, eh? ... where we might say "eh?" a lot? Eh?)

Our local Cabela's:Image

Just popped up advertizing the "Old Town Predator XL Motor Pod"...:
http://www.cabelas.ca/product/80269?pro ... 46EALw_wcB

...sure looks like the Minn Kota electric motor... seen other places like:
http://www.canoekayak.com/kayakfish/kay ... edator-xl/

Image

... and as far as I can see - and looks like your ES post and other places seem to confirm - it's using a "gel" sealed lead-acid battery? [ACK!]

... so my first ES thought was to upgrade to lithium-flavoured cells (w/stuff like near 4x power per given weight plus lasts 1000-2000 times recharging "full" discharges versus gels? So basically more "spendy" to purchase new, but with care should last for MANY YEARS before final recycling/replacement. (Landlubbers say "lowest overall costs per mile, etc".)

Still alongside ES?
ES changed my life (for the waaaaay better).

Eff. June, 2014 Phoenix Ebike Promotions

(Current ride? High speed lawn chair.)
https://endless-sphere.com/forums/viewt ... =3&t=57408

Phoenix Ebike Promotions conversion kit (work in progress. More drink holders, etc etc)
https://endless-sphere.com/forums/viewt ... 15&t=60564

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