Which inverter - charging e-scooter

[Glas Robin]

I’ve got an electric scooter (Xiaomi M365, great for final mile commuting and thinking of using when away in the van too); and thinking about getting a couple more for the Memsahib and gene puddle.

We’ve plans to be off grid at times, and plans for a second leisure battery and solar panels are in the pipeline.

I’d like to be able to occasionally charge the scoots when not on EHU, using an inverter. I’ve done the calcs and reckon a 1000w should do the trick to top them up, rather than a full recharge which we’d wait for EHU (or if this was a problem I may put in bigger batteries/panels.)

Question is, 1000w pure sine inverters vary in price from about 40 quid to much much more... do you get much more for the extra cash or is a cheaper one fine for my needs?

Thanks.

 

[DBK]

The unknown is how pure is the waveform on a cheap inverter? I've got a 1500W inverter which at £150 was at the cheap end in that size but short of using an oscilloscope I don't know how good it is compared to the more expensive ones at twice the price and more.

But will it matter? You can only give it a go but if it damages the charger you will need to buy a new and a replacement better inverter in too.

 

[Glas Robin]

I like your thinking. The charger is only 15 quid and I presume protects the electronics in the scoot from a dirty input, so maybe I should try a cheap inverter and see how it does; if it fries the charger then I can upgrade both.

I just wondered whether the cheaper inverters were as efficient as more expensive ones, or whether they might drain the leisure battery more quickly?

 

[DBK]

I like your thinking. The charger is only 15 quid and I presume protects the electronics in the scoot from a dirty input, so maybe I should try a cheap inverter and see how it does; if it fries the charger then I can upgrade both.

I just wondered whether the cheaper inverters were as efficient as more expensive ones, or whether they might drain the leisure battery more quickly?

I doubt there will be much difference in efficiency. The main thing is to fit an isolating switch so when the inverter isn't being used it can't draw any current. Not everyone does this but I think it is worthwhile if only for safety.

I wrote up my experiences fitting an inverter here: https://www.motorhomefun.co.uk/forum/threads/fitting-a-1500w-inverter.156023/

The links at the end probably don't work anymore but the stuff is still available. Automatic changeover isn't essential, especially for how you propose to use it for.

Any use of an inverter does mean the power extracted has to be put back! Check the capacity of the scooter battery against the habitation batteries. So if off EHU you will need reasonable solar wattage and/or a battery to battery charger - which I've also subsequently fitted. https://www.motorhomefun.co.uk/forum/threads/fitting-a-sterling-battery-to-battery-charger.191044/

 

[two]

1000W should be more than enough. I'd check the price of your charger, though, mine was over £150. You wouldn't be happy messing one of those up. A big (500Wh) battery will take a lot away from the hab battery. I'd only charge whilst on the move.

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[Lenny HB]

You tend to get what you pay for. I have £140, 1000 watt pure sine inverter it's quite good but the output is not quite a pure sine but far better than a modified sine wave one.

 

[Glas Robin]

Thanks for replies and I will go and study those other threads.

I made a mistake the 40 quid inverter was 1000w at peak, 500w normally.

The 1000w (2000w surge) psw ones on eBay start at £65.

Eg:

How much more do you really get for spending double that?

 

[arto stu]

what size are the scotter batts... my hab batts ( a pair of 110ah ) are flat long before my e bikes are charged... with my bikes it takes about an hour on charge for every hour you run the bikes... imo only try when u r moving...cors you could do what i did... buy a gennie and away you go ( head down for all the noise moaners )

 

[canopus]

Agree with @arto stu, if you haven't got the battery bank capacity in the first place, you can have as many solar panels and as expensive an inverter as you can find, you'll be 'flogging a dead horse'.

 

[Lenny HB]

Thanks for replies and I will go and study those other threads.

I made a mistake the 40 quid inverter was 1000w at peak, 500w normally.

The 1000w (2000w surge) psw ones on eBay start at £65.

Eg:

How much more do you really get for spending double that?

That one is from Singapore so you may may have to pay import duty, vat & customs agent fee.
Only items up to £15 that are duty free.

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[Glas Robin]

what size are the scotter batts... my hab batts ( a pair of 110ah ) are flat long before my e bikes are charged... with my bikes it takes about an hour on charge for every hour you run the bikes... imo only try when u r moving...cors you could do what i did... buy a gennie and away you go ( head down for all the noise moaners )

“With the 280Wh total battery power, 37.41V output voltage, and 7800mAh battery capacity“

 

[Glas Robin]

That one is from Singapore so you may may have to pay import duty, vat & customs agent fee.
Only items up to £15 that are duty free.

Thanks. That was the first in the list; there are UK sellers at about that price too.

I buy most of my stuff from overseas these days... and only seem to pay import duty about 1 time in ten. If you are willing to wait and choose a sea or rail route, the savings can be significant and if you buy carefully Chinese tech these days is very good.

The scooters go for £400 from a UK seller, I tracked mine all the way by rail from China over about 4 weeks but it only cost me £296.

 

[Richard n Ann]

Try looking on amazon. The reviews can be helpful

 

[Guigsy]

The scooter batteries are 7.8Ah, but at 37v. I guess that translates to about 24Ah on a 12v system? Plus inefficiencies. Yeah, you definitely don't want to do any more than top them up when you're off EHU.

 

[Glas Robin]

The scooter batteries are 7.8Ah, but at 37v. I guess that translates to about 24Ah on a 12v system? Plus inefficiencies. Yeah, you definitely don't want to do any more than top them up when you're off EHU.

Thanks, those were similar to my calcs. The scooters have the best part of an 18 mile range, so on a daily basis (even when away visiting new places) we are unlikely to drain much more than a quarter of the battery for the use I envisage. So hopefully the top up route is probably sufficient. If it isn’t then I’m thinking of a second 110ah battery and solar top up. Our other use is a bit of telly in the evening, LED lights and charging phones - all pretty modest.

I’m leaning towards a second battery, a couple of hundred watts of solar and the 1000w inverter as it gives flexibility for future use. The other possibility is a cccv dc-dc charger to step up the 12v to 42v for the charging. But that is a less flexible solution.

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[Minxy]

Out of interest Robin, what's the legal position on using these electric scooters? Are you allowed to use them on public roads etc here and abroad?

 

[Glas Robin]

Out of interest Robin, what's the legal position on using these electric scooters? Are you allowed to use them on public roads etc here and abroad?

Abroad, mostly yes. Indeed, many cities are encouraging them as drop anywhere transport.

In the UK technically not legal on public roads. I use mine for final mile commute between station and work...via residential back streets, wide deserted pavements and a large hospital site (private property). I haven’t had any trouble so far and I’ve passed police cars in traffic without any attention. They fit well in the bike section of the train.

I’m sure the UK will catch up legislatively as more and more people get them. They’d work well in cycle lanes, if we had more cycle lanes that is.

Helmets are a necessity, as with a bike.

 

[Guigsy]

The other possibility is a cccv dc-dc charger to step up the 12v to 42v for the charging. But that is a less flexible solution.

That will be a bit more efficient, but not massively. It might save a couple of Ah... but the number will still be big. Probably better spent on more solar panels or batteries.

 

[SandraL]

Our bikes are nominally 36 v batteries. Charger says 42v. I am useing a dc dc charger. I can set max current, for me 2 amps, and max volts, for me 41.5. It charges at 2amps until voltage gets to 41.5 and then maintains set voltage with current decreasing to trickle. At present in spain, with 160ah battery and 250 watts solar it has worked fine. Never discharged battery past half. Our mains battery chargers are basic with no sense lead to battery for temp. Cost about £15 plus box and leads to suit. Fan on unit runs when charging, cuts off when current is very low.

 

[autorouter]

As @Guigsy says, the 280 watt-hour battery will take 280/12 = 23.3 amp-hours out of a 12 volt battery. A typical 100 amp-hour leisure battery will only give you 50 amp-hours if you only discharge it to 50%. That means two scooter batteries will just about use up the usable charge in one 100 amp-hour battery.

A 100 watt panel will give you 6 amps for 8 hours on a good sunny summer day, ie 48 amp-hours. That's just about enough to put back the charge that two scooters take out.

@SandraL says that 250 watts of solar with 160Ah of battery works fine, and that's the sort of sizes you should be looking at. Maybe a bigger battery if you have three scooters.

You don't say what amps the charger outputs, but if it's 3 amps that's 120 watts, so a 1000 watt inverter should cope easily with three chargers at a time.

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[IandJ]

I fitted this inverter that happily charges 2 bikes at once. What I liked about it was the remote switching so that it could be mounted near to the batteries and out of the way, with the switch in an easily accesible place.

 

[138go]

..

 

[GPW]

Victron are a good (Dutch) brand in use and are used in boats and campers as they are reliable and won't unexpectedly go 'fffffzzztt' one day when you need them most like I suspect some Chinese ones do. Inverters are subtle items like switch mode power supplies (SMPS) but then made to wiggle at 50Hz and subject to all sorts of inconvenient loads etc - so a good recommendation.

Also check out Bimble Solar for deals although their search sucks so you may need to use Google/Duckduckgo to find some of their pages LOL.

There are three different types of inverter:

1. Quasi or modified 'sine' wave converters. These are useless unless you like shiny ballast.
2. Pure sine HF - like the Victron Pheonix SinusMax recommended, they are small, light but have high standby power.
3. Pure sine LF - like the Victron VeDirect type - big, heavy, low standby power.

Also to mix an inverter in properly with the charger and mains hookup it's worth getting rid of the old charger and buying an Inverter/Charger like the Victron Multi that converts the entire power system into a UPS - you can literally pull the hookup lead out and it switches over to the inverter for an uninterupted supply to the van as it contains charger (for hab + starter batteries), switch over relay, sensing circuit and inverter in the one box - which is what I'm using in my current small van.

 

[TheBig1]

don't forget that lead acid leisure batteries can only safely be discharged to 50% of capacity. so a 110ah battery has a usable capacity of only 55ah. drawing 24-27ah to fully charge just one scooter battery will take half your capacity and take a few hours of full sun for a solar panel to replace

 

[two]

... The other possibility is a cccv dc-dc charger to step up the 12v to 42v for the charging. But that is a less flexible solution.

A DC-DC solution might be more efficient than an inverter, but would not be as flexible because an inverter can address other requirements. Also check where the battery management ‘intelligence’ lies: I wouldn’t by-pass it if it’s in the mains charger (but it may be in the battery).
A modest inverter will help to prevent you from abusing the habitation batteries.

Habitation batteries dislike heavy and deep discharges, so I would prefer to charge one e-bike/scooter battery at a time and reduce the load.
Remember that e-bike/scooter batteries can have significant capacity. You won’t normally be recharging them from flat, but they could drain your supply if not careful.
It is said that you can ‘safely’ take 50% of the capacity from Lead-Acid batteries but I think it’s even ‘safer’ (they’ll last longer) to take out less.
In theory a 12V 110Ah battery could provide up to 660Wh from fully charged but some e-bike/scooter batteries could take in excess of 500Wh.

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[GPW]

don't forget that lead acid leisure batteries can only safely be discharged to 50% of capacity.

Very true for a wet cell lead acid.
However AGM and GEL batteries are fine with 75 to 80% capacity (10.6V lower sulphation limit = when a decent inverter will switch off) - so AGM's and GELs are worth the extra money as you get more capacity in the same weight. I.e: 100Ah battery will give you 50Ah for a wetcell, or 80Ah for AGM or GEL.

If/when you switch you must make sure the charger knows which one it is or battery life will be short, peak charging volts is quite important (and higher for AGM/GEL).

 

[GPW]

A DC-DC solution might be more efficient than an inverter, but would not be as flexible because an inverter can address other requirements. Also check where the battery management ‘intelligence’ lies: I wouldn’t by-pass it if it’s in the mains charger (but it may be in the battery).
A modest inverter will help to prevent you from abusing the habitation batteries.

You covered it here but it pays to be explicit:
Never charge any lithium based battery with anything less than a charger designed specifically for Lithium batteries. Model shop chargers are decent DC-DC chargers but you must setup the cell type, number of cells and charge rates but you may still miss balancing of a pack, so for the non-expert always use the correct charger. Best buy the right charger with a 12V input if you can - they must exist for some brands.

If you overcharge or overvoltage a lithium battery they tend to burst into a smelly, fierce, roman candle like flame that can and has burned down manu garages and houses and can't be extinguished. Trying to use water makes them burn harder. Personally if I had an e-scooter I'd make a rapid escape plan and put a decent, loud smoke alarm near where I stored the battery (and particularly where it was charging - a higher risk operation) and never charge overnight. I'd also keep it away from the gas bottes in case of fire.

You can also get fireproof lithium charging bags from Hobbyking that would make storage and charging safer if you can fit the battery in them while charging to contain the flames, that plus alarm (x 2) + escape plan would be my minimum requirement.
E.g:

I don't see changing habitation batteries from AGM to lithium ever making sense for this reason.

 

[two]

I'd also add that there are many different types of Lithium (chemistry)
and any warranty may be voided if you chose not to use the supplied charger.
And some of these batteries are not cheap (£700)!

 

[GPW]

Yes I've noticed the huge prices for Lithium packs, £650 - 900 for a single 100Ah one, £115 - 180 for an AGM/Gel one, I'm not getting why anyone buys the Lithium one unless for a super-light weight application.

A friend of mine bought 3 for his canal boat, I couldn't figure out why. What would be nice for the larger motorhome are some NiFe cells as they seem to last forever but I think they use a bit of space. There's also salt batteries - I think if I was off-gridding a house I'd go NiFe or salt, no need for anything else.

Lithium really scores in power tools and model drones, helicopters, laptops etc but I'm not seeing it for habitation use in campers. I'd rather invest the money in beer, fuel and tax LOL.

 

[Minxy]

Never heard of salt batteries ... interesting:

https://spectrum.ieee.org/energywis...-before-sodium-batteries-are-worth-their-salt