Range anxiety - mobility scooters

[Harry Bloomfield]

I've been doing a bit of experimenting......

The battery power on these mobility scooters, can deplete with little warning, so a small reserve to be tapped into, would be quite handy, so I've been looking at ways to do that.

Mine, runs on 5x 12v 20ah batteries in series, 60v, and so would need 5x smaller batteries to provide some spare capacity for emergencies, using just batteries.

Another way would be to generate the 60v, from a single 12v larger battery, using an inverter, but it would need a 1200w inverter, to cope with the entire load of a 1000w motor, or would it?

Along similar lines, I remembered a 12v 180w to 230 adapter I happened to have - that, with the normal charger for the scooter, plugged into it, and a 12v battery. The scooter, unlike some, is not inhibited by plugging a charger in, so it can be driven, whilst on charge. So I have just tried it, and it works.... 12v battery on the footplate, powering the 12v to 230v adaptor, powering the charger for the scooter.

 

[IT Minion]

12v battery on the footplate, powering the 12v to 230v adaptor,

Please let us know how long it takes to burst into flames. That's got to be an awful current draw, probably around 10x what each of the batteries is supposed to be supplying normally.

 

[Harry Bloomfield]

Please let us know how long it takes to burst into flames. That's got to be an awful current draw, probably around 10x what each of the batteries is supposed to be supplying normally.

Explain your thinking? I make it around 10amps, accounting for losses, which is well within the discharge rating.

 

[motorbiking]

Are they motorcycle batteries or more like car batteries?

5 motorcycle batteries wouldn’t take up much space. That would give you another 20% range.

Alternatively 14 18650 cells from two old laptops would give you 10% more range. But they need to be carefully charged.

It’s probably easier to use a car battery connected to a step up converter. Plenty on eBay for a £10er

Just need a switch to active the reserve. Recharge using standard car charger.

 

[Harry Bloomfield]

Are they motorcycle batteries or more like car batteries?

Something in between, deep discharge AGM's.

It’s probably easier to use a car battery connected to a step up converter. Plenty on eBay for a £10er

Yep, that is an idea I'm testing - 12v dc to 230v ac at 200w, followed by the stock battery charger. It will not put it in, as fast as the motor demands, but probably better than trying to push it home.

 

[motorbiking]

Something in between, deep discharge AGM's.


Yep, that is an idea I'm testing - 12v dc to 230v ac at 200w, followed by the stock battery charger. It will not put it in, as fast as the motor demands, but probably better than trying to push it home.

you don't need to go DC-AC-DC. Ebay etc have step up modules that will take 12v input and give 60v output. £10-20

 

[IT Minion]

Explain your thinking? I make it around 10amps, accounting for losses, which is well within the discharge rating.

1kW @ 60V is 16A. Each battery would be pushing 3A ish

Plus conversion losses of at least 10% for the dc->AC step up, more likely 15%. Total 18.4A

Plus another 10-15% (cumulative) for the conversation back to 12/60V. 21.6A

I may have a mistake in there but 1.3kW is a lot for a single 12V battery to supply.

 

[Harry Bloomfield]

I may have a mistake in there but 1.3kW is a lot for a single 12V battery to supply.

The mistake, is to assume the 12v battery needs to supply the 1.3kW. It doesn't it only provides a steady, fixed limit of charge to the built-in batteries. The built-in batteries, buffer the peak demands.

 

[foxhole]

Stick a suitcase generator on the back or tow it.

 

[securespark]

I've got insurance on mine, with breakdown assist!

 

[transam]

Probably not relevant ?

But one of our fellas had a flat battery on his transit on a job

And he managed to start the van with makita power tool battery (s) ?

 

[IT Minion]

The mistake, is to assume the 12v battery needs to supply the 1.3kW. It doesn't it only provides a steady, fixed limit of charge to the built-in batteries. The built-in batteries, buffer the peak demands.

Is that an assumption or fact? I'd expect it to try to do both. Batteries will supply as much current as they can before internal resistance drops their voltage or they satisfy their load. Lead acid batteries can so very high currents for short periods of time but the heat build-up limits long term supply.

 

[Alec_t]

Another way would be to generate the 60v, from a single 12v larger battery, using an inverter, but it would need a 1200w inverter, to cope with the entire load of a 1000w motor, or would it?

Yes it would, if you wanted to keep moving. But a lower powered one could top up the existing batteries if you're prepared to wait. The existing batteries clearly can't charge and discharge at the same time.

 

[Mottie]

The battery power on these mobility scooters, can deplete with little warning,

Why not try it out by continually running it until the battery depletes? You can do that without going too far from your home. That’ll give you a good idea of the range and how the battery meter performs. Before getting rid of my dad’s one, I charged it up and gave it a bloody good run all around Hornchurch. The batteries were still fine after an hour so I knew it'd have at least half an hour or more on an outward journey and still have enough to get back home.

Went round my mums, pumped up the tyres and cleaned up my dad’s old mobility scooter as she wanted to get rid of it. Cleaned up a treat. To test the battery, I went out on it - must've been out for over an hour with her dog riding on the footplate. Went all round Hornchurch. Sold it already - I let a friend of ours have it for her dad as he is diabetic, got a dicky heart and is on the list for a hip replacement and when he gave over his blood count numbers, they took his licence away! At least he can pop down the shops and the doctors on his own now.

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[Harry Bloomfield]

Yes it would, if you wanted to keep moving. But a lower powered one could top up the existing batteries if you're prepared to wait. The existing batteries clearly can't charge and discharge at the same time.

No, but the load is not a continuous 1000w, most likely it will be between 0 and 50w much of the time, during which it would be putting some in the main batteries.