Replacing lead acid battery with Lithium Ion battery

[vinaytej445]

I wish to replace my electric wheelchair's lead acid battery 24V 12AH with Lithium ion battery. Please guide if I may face any problems? If yes What would be the ideal voltage for long endurance usage

 

[D.A.(Tony)Stewart]

The ideal voltage must be in the yet to be defined controller range.

Then the ideal state of charge SoC is to use no more than 50% between slow charges preferably 80% to 30%. Preventing Fast charge and deep cycles can increase the cycle count 100x using this protocol. Ask suppliers who know about how to get this with a SOC gauge and charger settings or modifications.

 

[BradtheRad]

By putting heavy L-A batteries near the wheels a wheelchair has a lower center of gravity. It's more stable. Less likely to tip cornering or on steps or on sloped walkways.

Lighter weight batteries give you faster speed, greater mobility for anyone lifting the wheelchair.
Question: Have you seen other people saying they're glad they installed Li-Ion batteries?

 

[KlausST]

Hi,

I´m the person doing reliable stuff. Thus I´d first need specifications and requirements .. then I´d do the math and the verification according datasheets.

So like load current, if pulsed: then peak current, frequency, waveform...
and also whether you want/need to use the same charger, and if yes: what it´s charging method, threshold voltages, currents.. and so on.

Li-Ion batteries are much more critical .. and on mistreatment they may die way too early or even explode and cause fire.

Klaus

 

[dick_freebird]

There exist Li "12V" standard form batteries meant for this. The charging, I do not see so ala carte I reckon.

Electric wheelchairs I have taken apart, use 2 x 12V standard looking SLA batteries. I think you stand a good chance of finding suitable size (and size for size, Li should win big).

If CoG is affected, iron plate Is cheap.

 

[vinaytej445]

Thank you all for your information and suggestions. I wish to replace both L-Acid battery and its charger with L-Ion ones. I hardly move out my house even with wheel chair due my physical condition. When going out my dad would sort Out CG issue by adding some extra weight. However, I would like to know if the motors support DC supply from L-Ion. I'm novice in this matter so request your kind advice please

 

[vinaytej445]

There exist Li "12V" standard form batteries meant for this. The charging, I do not see so ala carte I reckon.

Electric wheelchairs I have taken apart, use 2 x 12V standard looking SLA batteries. I think you stand a good chance of finding suitable size (and size for size, Li should win big).

If CoG is affected, iron plate Is cheap.

Thank you for your information and suggestion. I wish to replace both L-Acid battery and its charger with L-Ion ones. I hardly move out my house even with wheel chair due my physical condition. When going out my dad would sort Out CG issue by adding some extra weight. However, I would like to know if the motors support DC supply from L-Ion. I'm novice in this matter so request your kind advice please

 

[vinaytej445]

Hi,

I´m the person doing reliable stuff. Thus I´d first need specifications and requirements .. then I´d do the math and the verification according datasheets.

So like load current, if pulsed: then peak current, frequency, waveform...
and also whether you want/need to use the same charger, and if yes: what it´s charging method, threshold voltages, currents.. and so on.

Li-Ion batteries are much more critical .. and on mistreatment they may die way too early or even explode and cause fire.

Klaus

Thank you for your information and suggestion. I wish to replace both L-Acid battery and its charger with L-Ion ones. I hardly move out my house even with wheel chair due my physical condition. When going out my dad would sort Out CG issue by adding some extra weight. However, I would like to know if the motors support DC supply from L-Ion. I'm novice in this matter so request your kind advice please

 

[D.A.(Tony)Stewart]

Lithium Iron Phosphate are the best Lithium batteries in every aspect and will last more than 10 ~ 20 yrs if you get the best slow overnight daily charging. Mistubishi e-cars have a 10 yr warranty still have 80% capacity. I have a friend with one now 15 yrs and is a very happy camper. The addition of a battery management system (BMS) and slow overnight charge rate is what achieves these recharge cycle numbers from 5000 to 10000 cycles if you use this method. Even better is just keeping the battery between 25% to 75% charge for the longest life. Do not charge nightly if you only use 20% of capacity. Keep it below 80% most of the time and then just charge it when needed to keep it in this range and occasionally go to 100% to prevent the memory effect which is less serious than the older Ni-Cads.

AGM batteries cost more in the long run in energy per $ rate.

 

[KlausST]

Even better is just keeping the battery between 25% to 75% charge for the longest life.

this is true.
The problem I see: if you do so, then you can drive only half the distance compared to 100% to 0%.

For sure you are flexible to recharge at any point of discharge. You can charge at 25% ... or you can drive on and recharge at 10% for example.
But then you still use 65% of capacity only.

To improve the situation you need to tell the charger (the night before your travel) to charge to 100%.
But this is not convenient ... to think ahead for your car ... (Nowadays it´s rather expected the car thinks for you)

I have no solution to this ... maybe we need an AI (or the google database) to check your activity and schedule and your traveling behaviour, the charger locations, your mood, traffic, .. to intelligently fill your batteries.

Klaus

 

[D.A.(Tony)Stewart]

Klaus he is not driving far, remember? He hardly goes outside.

Keep between 25~75% or 20~80% if need be and monthly 100% should be fine. But standard chargers wont do that automatically going to 100% everytime. Only some new iOS smart phones have the slow last 80% at lower voltage and Lenovo laptaps have this algorithm of reduced capacity charge if plugged in all the time to prevent the higher voltage that accelerates aging. So you may have to ask around. It would be like stopping a low Constant Current CC charge rate at 80% or 3.8V instead of going up to 4.2V per cell then dropping to 3.8 quickly after starting to load it.


Otherwise putting a timer on the charger for a DIY solution when you get a battery with a more than 3 day capacity at home with some insight on time rate vs charge rate. But ask for guidance from supplier on that of the charger+battery.

 

[KlausST]

Klaus he is not driving far, remember?

You were referring to Mitsubishi cars and camper ... and I referred to you ... here we are ;-).

But indeed my comment can be seen generally: It´s always a compromise between long lifetime or high capacity usage.
Also - as you mentioned - charging current, discharging current plays a role. Also temperature and active cell balancing and so on.
I´t not an easy task to find the best way ... as the parameters often change on a daily basis.

Klaus

 

[D.A.(Tony)Stewart]

Here is an example of a smart charger https://www.amazon.ca/Haibro-Charger-LiFePO4-12V-24V/dp/B08P5YNP3M?th=1 There may be others like this so get someone who can assist you.

I was referring to Mitsubishi who was one of the early e-car producers who also made Lithium iron phosphate LiFePO4 batteries which are the best and not the standard "Lithium lead" Ion batteries.

 

[dick_freebird]

The motor control I've seen was pretty basic looking, if you keep to the old voltage (which those "12V" batteries are meant to) there ought to be no problem in that regard.

Charging might be "special" as from what I've seen the batteries are simple series, no center tap for balancing which Li cells need, lead cells you can just overcharge on float and everybody gets topped up eventually. LiFePO4 I've read is somewhat tolerant of overcharge but you may want to find a charger solution which includes balancing, and add that one piece of wire.

 

[D.A.(Tony)Stewart]

Any 12V charger will work if the battery has a smart charge regulator built into the Lithium Iron Phosphate battery like the ones I recommend and only charge when needed like well below 50% capacity.

There is a wide range of prices and quality batteries. 100Ah should be ideal capacity for making those infrequent outings, which is a lot more than you had and that means you can travel faster, longer and without worries. 2x the capacity at 1/3rd of the weight for same size Lead acid.

Some are more than $1200 and others $100 not so good. Must have BMS inside.
Poor example only 3Ah $100us another poor example only 3.74 pounds $100 with fake specs and no BMS

$300 CDN with BMS LiFePO4 100Ah 12V might not be avail in US so look on Amazon for similar with shipping.

Amazon.ca

For US market $150

Amazon.com

another good choice

Note that for 12V batteries are a family of different voltages
GlassMat Lead Acid are cheap but not good are 13.8V and std car batteries 14.2 on charger are only to start a car not run heavy motors for a long time so not good and are 12.5 off charger down to 11.5V and LiFePO4 are called "12.8V" weight approx 22 pounds = 10 kg.

Make sure the size fits your compartment.

I don't know what country you are in and your budget. Can you say?

 

[D.A.(Tony)Stewart]

The user has low mileage requirements that are undefined.