# It's Time (Converting Lead-Acid to Lithium, Mobility Scooter)

#### iONic

Joined Nov 16, 2007
1,650
I've had it, buying two new Lead-Acid or Glass-Matt batteries every couple of years. The trouble is that no matter which direction I take from my house, I have hills, hills that are, by all accounts, very detrimental to the service life of these batteries. I switchback numerous times and still have problems.
I do not blow a fuse, whatever it is rated at (20A, 30A...) I will check this rating.
I am looking to obtain an approximte equal to the voltage, but with higher potential for current. The Lead-Acid's just do not have the umph or longevity.
So, a single Lithium a at 24v-28V or two with similar voltage, but with a greater ability to withstand the current draw.

I can get a DC Ammeter (will have to buy one) so that I can determine the current that is being asked of the batteries is first on the list. However, the fuse/circuit breaker rating really should be a good beginning too.

Looking for ideas on what I may be up against. Will the Lithium batteries actually be able to perform better and last longer for the task at hand??

Thanks

#### crutschow

Joined Mar 14, 2008
26,020
Will the Lithium batteries actually be able to perform better and last longer for the task at hand??
Likely.
But they are a lot more expensive, and require a dedicated charger designed for Lithium batteries (you can't use the lead-acid charger).

#### iONic

Joined Nov 16, 2007
1,650
Understood.
I guess I ought to price something in the ballpark for both batteries and charger before I go anywhere!

#### mvas

Joined Jun 19, 2017
537
A 12 Volt 50 AH Li-Ion battery will cost between $400 -$800
A 12 Volt 50 AH Lead Acid battery costs between $90 and$150

If you deep discharge the Lead Acid Batteries very deeply, on every trip, they will not last very long.
How deeply are you discharging the battery bank on on each trip?
What is the Mfr, Model, Voltage & AH rating the battery that you are using now?
Are you 100% positive you are not chronically over-charging or chronically over-charging - both reduce life significantly.

2 years is typical, if deeply discharged daily.

Do you need larger AH batteries?

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#### Dodgydave

Joined Jun 22, 2012
9,857
Sla batteries are easier to maintain than lithium plus you need a dedicated charger. What us the capacity of the sla battery,? maybe you need an higher rating Ah.

#### iONic

Joined Nov 16, 2007
1,650
A 12 Volt 50 AH Li-Ion battery will cost between $400 -$800
A 12 Volt 50 AH Lead Acid battery costs between $90 and$150

If you deep discharge the Lead Acid Batteries very deeply, on every trip, they will not last very long.
How deeply are you discharging the battery bank on on each trip?
What is the Mfr, Model, Voltage & AH rating the battery that you are using now?
Are you 100% positive you are not chronically over-charging or chronically over-charging - both reduce life significantly.

2 years is typical, if deeply discharged daily.

Do you need larger AH batteries?
I travel aprox. 0.75 - 1.25mi before I recharge a bit before repeating the trek. In other words, I can not take both dogs, back to back on this same trek...(0.75 - 1.25mi + 0.75 - 1.25mi = 1.5 - 2.5mi)

I have measured the voltage in the past with voltage remaining just under 13v on a single trip, but will do this again, with results to follow.

Currently I have the Power Sonic PS-12350 12V 35AH SLA Battery (24lbs ea.) ($75 ea) installed, but have managed to squeeze in the Powersonic PS-12400 - 12V 40 AH SLA Battery (31lbs ea.) ($154 ea.) with better overall results. I do know I do need a greater AH battery ass the 40AH battery if only for a greater current capability (or am I all wet here?)

I don't think I really discharge the batteries too low, keeping them above 12V and have dedicated chargers for the batteries.

These recent two batteries I purchased are only a year old.

The trouble with higher AH batteries is that they are heavier and I can barely carry them in and out of the house in winter and spring. 24lbs/31lbs.

What chemistry would be preferable? Li-Ion or LiFePo4?

UPDATE: The fuse for the motor controller is 10A and does not blow when going up hills. As a result, the batteries either can't or won't provide 10A??? Or is this fuse protecting just the controller and the current to the motor is probably greater. Woild I look for a A rating on the motor itself?

ALSO: I presume, but I may be wrong, that two 12V chargers(charging each individual battery) is better than a simgle 24V charger(charging them in series)... Thoughts!
This is currently how I have configured the SLA batteries(1 charger per 12V battery)

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#### oz93666

Joined Sep 7, 2010
737
Good move to convert ... you can get the same range with a lithium battery that has a quarter of the weight .....

The figures quoted by mvas are way out..... 12V 50Ahr lithium should be less than $200 You do not need a big battery to deliver high power, only for long range ... The way to approach this is to decide what is the maximum range you require , maybe you only make short journeys , and so can get away with a small battery .... What is the power of your Scooter , (probably about 300W) and what is the longest journey time you have to make ??? What is the voltage you require , if 24V it makes things very easy. Last edited: Thread Starter #### iONic Joined Nov 16, 2007 1,650 Good move to convert ... you can get the same range with a lithium battery that has a quarter of the weight ..... The figures quoted by mvas are way out..... 12V 50Ahr lithium should be less than$200

You do not need a big battery to deliver high power, only for long range ...

The way to approach this is to decide what is the maximum range you require , maybe you only make short journeys , and so can get away with a small battery ....

What is the power of your Scooter , (probably about 300W) and what is the longest journey time you have to make ???

What is the voltage you require , if 24V it makes things very easy.
A ride around the block is about 2 miles. I took one of my dogs on this route today and upon return the batteries read 12.98V and 13.00V The fuse connected to the battery is 40A and has never been blown. If I take two identical rides I would put on about 4mi. Technically, the scooter could easily do this, but just not up hills or over grass. I'm pretty sure I had done this many times with the 31lb SLA batteries so a 40AH Lithium would likely be enough.

The power of the scooter, I am not sure of. Do they list this anywhere?

#### oz93666

Joined Sep 7, 2010
737
A ride around the block is about 2 miles. I took one of my dogs on this route today and upon return the batteries read 12.98V and 13.00V The fuse connected to the battery is 40A and has never been blown. If I take two identical rides I would put on about 4mi. Technically, the scooter could easily do this, but just not up hills or over grass. I'm pretty sure I had done this many times with the 31lb SLA batteries so a 40AH Lithium would likely be enough.

The power of the scooter, I am not sure of. Do they list this anywhere?
A search shows normal range is about 20 miles before recharge
And your voltage readings show you are using a fraction of the battery capacity , less than 10% !!!
So you could function perfectly well with a battery a tenth the size and price!!
Certain types of lithium can handle high discharge , so getting up hills will be no problem even with a very small battery , they should perform better than your lead one ...

I buy everything on eBay ... a quick search turned up this on as closest fit costs 180 pounds including delivery only ....1.6 kg ...includes it's own charger it's really to big for you're needs , but with excess capacity you can charge to a low voltage 3.93 per cell not 4.2 V (7 cells in pack) ...charging low will give a life of 4000 cycles , not the usual 500 cycles
https://www.ebay.co.uk/itm/Lithium-...hash=item467999831d:m:mgr--BvnckG2t7RU-DQSvUg

#### oz93666

Joined Sep 7, 2010
737
Here's another possibility ...90 pounds ...weighs less than a kilo ...can hold it in your hand ...

Believe it or not this is all you need ... Designed for high demand radio control it can deliver astonishing power, can handle a complete discharge in less than a minute , so it will deliver the power for any hill , and as you only need to travel a few miles , it has enough capacity.... about 20 mins drive time or 4 miles range.
https://www.ebay.co.uk/itm/HRB-RC-L...174441?hash=item1a7af74269:g:8gcAAOSwcZNcxu13

EDIT ... I've just realised you've given battery readings of 12.9V ... is 12V the voltage used by the scooter , or do you have 2 batteries in series making 24V???

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#### iONic

Joined Nov 16, 2007
1,650
Here's another possibility ...90 pounds ...weighs less than a kilo ...can hold it in your hand ...

Believe it or not this is all you need ... Designed for high demand radio control it can deliver astonishing power, can handle a complete discharge in less than a minute , so it will deliver the power for any hill , and as you only need to travel a few miles , it has enough capacity.... about 20 mins drive time or 4 miles range.
https://www.ebay.co.uk/itm/HRB-RC-L...174441?hash=item1a7af74269:g:8gcAAOSwcZNcxu13

EDIT ... I've just realised you've given battery readings of 12.9V ... is 12V the voltage used by the scooter , or do you have 2 batteries in series making 24V???
The Mobility Scooter is a 4 wheel vehicle that uses (2) 12V SLA batteries. I measured each battery...one reading 12.9V and the other 13.0V.

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#### iONic

Joined Nov 16, 2007
1,650
Forgive my skepticism, but somehow I find it hard to believe the battery in post#9 is going to move me and the scooter 4+ miles.

#### mvas

Joined Jun 19, 2017
537
Forgive my skepticism, but somehow I find it hard to believe the battery in post#9 is going to move me and the scooter 4+ miles.
Three of them, connected in parallel, might be equivalent to your 24 Volt 40 Ah Lead Acid Battery Pack
I do not see any warranty for those batteries.
$177 (euro ) x 3 =$531 (euro)

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#### mvas

Joined Jun 19, 2017
537
Good move to convert ... you can get the same range with a lithium battery that has a quarter of the weight .....

The figures quoted by mvas are way out..... 12V 50Ahr lithium should be less than $200 You do not need a big battery to deliver high power, only for long range ... The way to approach this is to decide what is the maximum range you require , maybe you only make short journeys , and so can get away with a small battery .... What is the power of your Scooter , (probably about 300W) and what is the longest journey time you have to make ??? What is the voltage you require , if 24V it makes things very easy. Relion 12 Volt 40 AH Lithium =$514.95 x 2 Batteries = $1,030.00 3 Year Replacement Warranty + 2 more years pro-rated Warranty = 5 Year Total warranty https://relionbattery.com/products/lithium/rb40 or you can buy from a no-name mfr, with no warranty = at your own risk. Please post URL for your 12 Volt 50 Ah Li-Ion battery with a 5 year warranty for under$200 ...

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#### mvas

Joined Jun 19, 2017
537
Here's another possibility ...90 pounds ...weighs less than a kilo ...can hold it in your hand ...

Believe it or not this is all you need ... Designed for high demand radio control it can deliver astonishing power, can handle a complete discharge in less than a minute , so it will deliver the power for any hill , and as you only need to travel a few miles , it has enough capacity.... about 20 mins drive time or 4 miles range.
https://www.ebay.co.uk/itm/HRB-RC-L...174441?hash=item1a7af74269:g:8gcAAOSwcZNcxu13

EDIT ... I've just realised you've given battery readings of 12.9V ... is 12V the voltage used by the scooter , or do you have 2 batteries in series making 24V???
Twelve of those batteries, connected in 2S6P, might be equivalent a 24 Volt 40Ah battery bank.
$113.00 x 12 =$1,356.00

3 Month Warranty + 3 Month pro-rated
6 Months = is how long this mfr expects this battery to last.
The warranty, or lack thereof, says it all.

2 of these batteries in series = 24v, will provide 40 amps to the motor for about 9 minutes - ouch.

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#### oz93666

Joined Sep 7, 2010
737
Forgive my skepticism, but somehow I find it hard to believe the battery in post#9 is going to move me and the scooter 4+ miles.
Such scooters are designed to have about 20 mile range with those lead acid batteries.... we only need 4 miles , ... lead acid are 5 times heavier than equivalent lithium ... So the mass of the new battery should be 25 times less than the current one ... So if your current batteries weigh 25 Kg , you need about 1Kg of lithium

the above lithium can deliver power at the rate of KWs , you need perhaps 100W

Still not clear if the lead acid are wired in series ???

#### iONic

Joined Nov 16, 2007
1,650
Such scooters are designed to have about 20 mile range with those lead acid batteries.... we only need 4 miles , ... lead acid are 5 times heavier than equivalent lithium ... So the mass of the new battery should be 25 times less than the current one ... So if your current batteries weigh 25 Kg , you need about 1Kg of lithium

the above lithium can deliver power at the rate of KWs , you need perhaps 100W

Still not clear if the lead acid are wired in series ???
Yes, the 12V batteries are wired in series, for a combined voltage of 24V

Was looking at this...24V Battery

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#### jos touw

Joined Jan 13, 2019
2
Have you thought that the other parts of the system may be tired you don't say how old the scooter is but looking at the picture it is not that young,
If any of the wiring connections are dirty for instance,or even if the motor commutator is burned, sticking brushes all things I would check first for a cheap fix.
I say this because you mention poor performance on grass and hills,
Is the scooter rated for a top speed? looking at it I would guess 4/6 mph so this is geared low for kerb climbing and low 10% inclines.

#### jmsayles

Joined May 21, 2013
4
You need to be very careful putting several lithium batteries in series. Internal resistances should be match between batteries in series or you are over exercising the lowest resistance battery. We found even with matched battery pairs, one is getting exercised more than the other.
The batteries will last longer when they are charged more frequently. The battery life is related to the amount the batteries are discharged. You should be able to get the battery application guide to see the relationship for the particular batteries you are interested in using.

Another battery technology you might want to look at that is lore cost competitive and you can use the same chargers is pure lead batteries. They approach lithium performance but are less expensive. They are still as heavy as the lead-acid batteries, however.