Rebuilding scooter battery

Batteries, Chargers, and Battery Management Systems.
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ThomasEekels   1 mW

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Joined: Aug 18 2019 12:33pm

Rebuilding scooter battery

Post by ThomasEekels » Dec 04 2019 10:54am

Hi all,
our son has an electric scooter that runs on 4 Led-acid gel batteries.
Now he has ruined his 3rd set and it becomes an expensive hobby.

He asked me if I can replace the led-acid by a lI-Ion battery system. I am thinking on that.
There is much room, having 4 spaces for a 12V led battery available. I am thinking of building 4 separate LI-Ion ' tanks' for those spaces and wire them together.

Option A: I could build 4 packs of 3s ?p and put the 4 packs in series,
Option B: I could build 4 packs of 13S. ?p and wire the 4 packs parallel

How about that choice ? Any preference based on efficiency, charging, e.t.c. ?

Than, I need to add balance circuits to the batteries during charge.
Supposing I will charge the whole set together, with a 48V charger,
What balance circuits do I need to build for both configuration options ?
Can it be 4 balancers for 12V. when option A ?
Can it be 4 balancers for 48V. when option B?

Finally, how do I protect the scooter from deep de-charge, (f.i. insert a motor power-shut-off at minimum voltage level?)

Is this a viable project ? If not, the scooter probably will end-up on the scrap yard but it still is a good scooter so tat would be a waste.

Thomas

999zip999   100 GW

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Location: Dana Point So. Cal

Re: Rebuilding scooter battery

Post by 999zip999 » Dec 04 2019 4:26pm

Depending on the space at hand you may be able to use automotive batteries high grade and a BMS charge them let the BMS balance them. Or buy a ready made pack with BMS and charger.
More info on electric scooter link pictures something

Voltron   10 MW

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Location: Santa Barbara CA

Re: Rebuilding scooter battery

Post by Voltron » Dec 04 2019 8:00pm

They make LiFePo chemistry lithium batteries that are a drop in replacement for 12v sealed lead. The lithium ion phosphate chemistry runs at a different voltage that regular lithium, that is close enough to less acid voltage to work. It didn't have the energy density of regular lithium, but way better than lead acid. Either way though, the main reason I've seen for killing scooter packs is they don't normally have a balancing system to even out the individual sla bricks to each other. So one or two start getting over charged, and the others end up undercharged, killing all of them.

The easiest method for balancing lead acid is to use a regular 12v charger, and once every couple of weeks hook it to each battery to top it off. Some scooters are a pain to get to all the terminals though.

Voltron   10 MW

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Location: Santa Barbara CA

Re: Rebuilding scooter battery

Post by Voltron » Dec 04 2019 8:07pm

viewtopic.php?f=14&t=102289&start=50

This guy built his own balance leads coming from the batteries so he could check and charge them without opening up the body panels on his scooter.
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WhatsApp Image 2019-09-20 at 13.58.38.jpeg
WhatsApp Image 2019-09-20 at 13.58.38.jpeg (115.55 KiB) Viewed 366 times

ThomasEekels   1 mW

1 mW
Posts: 14
Joined: Aug 18 2019 12:33pm

Re: Rebuilding scooter battery

Post by ThomasEekels » Dec 05 2019 3:36am

Thanks for this info.
Indeed,the scooter does not have a balance between the 4 led-acid packs. The individual charge for balance is a good tip.
I could run4 sets ov 12v leads to the outside...

however.. any comments on my initial questions ?

Voltron   10 MW

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Location: Santa Barbara CA

Re: Rebuilding scooter battery

Post by Voltron » Dec 05 2019 12:17pm

The switching to lithium plan maybe depends on how much the pack is going to be checked by someone. Lithium is much more dangerous, especially when you get into multiple split packs. It creates more ways to have overcharging and undercharging going on, maybe at the same time across the pack, both of which lithium hates worse than lead, with occasional flaming outcomes.
Having layers of safety enhancers would help, like actual digital voltmeter displays for each section, and chargers plugged into lamp timers to prevent leaving them on for days by accident.

Voltron   10 MW

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Location: Santa Barbara CA

Re: Rebuilding scooter battery

Post by Voltron » Dec 05 2019 12:26pm

And re the balance taps, I would say they're essential for either... But they are themselves a potential source of short circuits if not done right.
I think you would be surprised by the extended life of a sla pack actually kept in balance. It's great practice anyway before stepping into a split lithium pack where you might be checking dozens of channels, instead of just four. A lot of cheap BMSs seen to have a one in four failure rate, so you really should be checking the subpacks a lot so it adds up.

999zip999   100 GW

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Location: Dana Point So. Cal

Re: Rebuilding scooter battery

Post by 999zip999 » Dec 05 2019 1:35pm

Still a link to the scooter for good advice.

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