question

hugh-mungous avatar image
hugh-mungous asked

2 x 12v Liepo4 in series mobility scooter

Hi. thanks for your time. I have bought 2 x 100ah lifepo4 batteries for my mobility scooter. I also have a smartshunt and a 24v 16a charger.

The batteries are in series so effectively 24v output to the motor and lights etc.

Q: I have fitted the smartshunt to the negative side of one battery and the positive cable from Aux to the + on the same battery. I have also put the other positive lead from the aux to the other + terminal of the second battery and set it up as a starter, don't know if that is correct?

Q: I would like to know what settings I should enter, i.e. the ah should it be 100ah? What should I enter in the other settings?

Q: The other thing I'm not sure of is the voltage, I am getting roughly 13.8v reading and on the starter battery 27.6v on the starter battery, is this correct? I would assume that it should show me 13.8v on both?


Many thanks


SmartShunt
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5 Answers
pwfarnell avatar image
pwfarnell answered ·

Have a read of the manual especially Section 3.5.2 wiring and setting the unit tor series batteries with mid point monitoring. Aux to middle positive, other positive to second battery and aux set to mid point. You will then read main batt as 27.8 and mid point as 23.8.

https://www.victronenergy.com/media/pg/SmartShunt/en/index-en.html

Capacity is set to 100Ah.

Charged voltage should be 0.4V below absorption setting on the charger, probably 28.0V or 28.4V. Tail current around 4%. Charge efficiency 99%, Peukert coefficient 1.01.

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hugh-mungous avatar image hugh-mungous commented ·
Hi. It appears I have the aux on the wrong battery. I have it on the + side of the battery which the shunt is wired.


I'll switch them round and see what happens. It's effort for me to get the seat off as it's as heavy as a car seat. I'll need to pluck up the energy to do it.


I've changed the other settings as you've suggested.


Many thanks.

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kevgermany answered ·
Mid point should be exactly half the full voltage if the batteries are in balance.

@Hugh Mungous with two lithiums in series, unless the BMS will do the job, consider a battery balancer. A diagram of your actual wiring would help, I had trouble following your description.


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hugh-mungous avatar image hugh-mungous commented ·

img-3103.jpeg

diagram not very technical

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hugh-mungous avatar image hugh-mungous commented ·
Hi


I've now added 2 images.


Many thanks

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hugh-mungous avatar image hugh-mungous commented ·

@kevgermany images attached thanks

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hugh-mungous avatar image
hugh-mungous answered ·

img-3104.jpeg

Batteries in situ


img-3104.jpeg (4.0 MiB)
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hugh-mungous avatar image
hugh-mungous answered ·

Thanks for the advice thus far

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kevgermany avatar image
kevgermany answered ·

Sorry, missed your replies.

Shunt should be in the negative cable marked black on the left of your picture. Make sure the battery side is towards the battery.

Shunt positive should be connected to the positive red of the right battery.

Aux should be connected to the connection between the batteries that has the breaker in it. It doesn't really matter where. Easier the better. Probably on one of the battery terminals. As there will be some resistance in this connection, the mid point voltage will be slightly off. Nothing you can do about that. I've unaccepted your last post, it's used to show problem solved.

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