Need some math help ie charging a 24v 15ah battery from a Jackery or similar? (1 Viewer)

[PaulC70]

So we have a trip next week and the other halfs mobility scooters down to one battery only which means effectively we'll only be holidaying every other day while waiting for it to charge and also means every other day will be on a site for ehu.

Im seriously considering a jackery/bluetti/anker/ecoflow to tide us over BUT not sure on the math?

eg a river 2 ecoflow looks like its got 268Wh capacity so using the mobility scooters mains charger which it says is a 3a charger will it work? I mean Im assuming yes, but will it even charge the mobility scooter battery fully or die first? I don't get ah vs wh etc sorry

Also, I know it's not the most efficient thinking of a 12v power station to 240v back to 24v 3a to charge the battery, but needs must :-(

EcoFlow RIVER 2 Portable Power Station - EcoFlow UK

Sizeable 256Wh capacity and 300W output. Fastest recharge; 0-100% in only 60 min, 70% faster than the industry norm. Charge without damaging the battery with TÜV Rheinland safe charge certification. Lightweight at only 3.5 kg, 30% lighter than the industry standard. Safe LFP battery provides 10...

uk.ecoflow.com

 

[Lenny HB]

What is the. Info on the charger, current at 24v & current at 240v?

 

[PaulC70]

What is the. Info on the charger, current at 24v & current at 240v?

Ah, sorry, just noticed it's hiding under the sticker! Not that it helps me out much :-/ Hope it means something to you Lenny?

 

[autorouter]

Basically watt-hours = amp-hours x volts. Or amp-hours = watt-hours /volts. So a 268Wh battery can (in theory) provide 268 / 12 = 22.3Ah to a 12V battery, or 268 / 24 = 11.2 Ah to a 24V battery.

In practice you would lose at least 10% off that, more like 20% probably.

268Wh is not very much, it's fine for charging phones and running a couple of LED lights, but not heavy usage. For comparison, an e-bike battery is about 500Wh and a 100Ah motorhome leisure battery is about 1200Wh. Do you have any numbers for the mobility scooter battery? either Wh, or Ah plus Volts?

The charger will certainly work, in that it requires about 100 watts to function (29.4V x 3A, plus a bit for inefficiencies), and the Ecoflow River 2 will provide up to 600W. But I would imagine the scooter battery is larger than 268Wh, probably at least 500Wh, so it would only half-fill it at best.

 

[Lenny HB]

Those figures don't add up, 3 amps at 29.4v is 88 watts and the mains side is rated at
3.5 amps 100 - 240 the 3.5 will be at 100v so that's 350 watts, no charger is that inefficient.

What is the voltage is the voltage and watts of the battery?

Taking the 29.4v at 3amp is correct a small 150 watt inverter would do the job.

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[autorouter]

the mains side is rated at
3.5 amps 100 - 240 the 3.5 will be at 200v so that's 350 watts, no charger is that inefficient.

Its low limit is 100V, presumably so it can be used in the USA, so that would be 175W. Also it will be allowing for the inrush current at startup, only for a fraction of a second obviously, but the fuse has to be big enough not to blow for the inrush surge. Once it's settled down, I think the output rating is a better guide to overall power consumption.

 

[Lenny HB]

Its low limit is 100V, presumably so it can be used in the USA, so that would be 175W. Also it will be allowing for the inrush current at startup, only for a fraction of a second obviously, but the fuse has to be big enough not to blow for the inrush surge. Once it's settled down, I think the output rating is a better guide to overall power consumption.

Just edited the typo on my post but result is the same 100v at 3.5 amps is 350 watts.

 

[PaulC70]

Sorry for the delay getting back to ye, yes the battery is 24v 15ah and says on the label 398wh?

 

[autorouter]

That battery is about 400Wh. To fill it from another battery would take about 500Wh.

One of those lithium power packs with a battery capacity of 500Wh would just about do that.

An alternative would be to run a small inverter from the leisure battery of the MH. 500Wh is equivalent to 500 / 12 = 42Ah from a 12V battery. That's quite a lot from a single leisure battery. If it was a 100Ah leisure battery, there's probably only about 50Ah of usable charge. So after taking 42Ah there wouldn't be a lot of usable charge left. But it would do the job if necessary.

A small inverter, say 150W, would take less than 10A when running that scooter battery charger, so no need for those big thick copper wires that are usually seen in high power inverter installations.

For the future, it might be an idea to add a second battery to double the leisure battery size, and wire in a small inverter. That would be plenty big enough to charge the scooter battery a couple of times, and/or allow you to go off-grid for longer

 

[PaulC70]

Yeah, I've plans for a B2B / inverter / second lithium battery (have a 300ah fogstar already) but only a 100w solar panel so planning a second panel too. But money and time plus just had my prostate cancer treatment.

Right now, Im leaning toward a bigger power bank for this trip - found a good deal on a Ecoflow Delta Max 2000 here https://uk.ecoflow.com/products/delta-max-portable-power-station-refurbished?variant=47191948656979

Hope that link works. I think I'd get a few charges out of that before it needed to be recharged on a site

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[Pukka]

How are you planning on charging the ecoflow?

As you already have a massive 300ah lithium battery, just get a 150w inverter.

I theory your current 12v will charge the 24v battery 5-6 times. The portable unit will do it 1-2.

You engine will charge the lithium while driving and put the money saved to a b2b so you can charge your 300ah while driving more efficiently.

 

[bigtwin]

How are you planning on charging the ecoflow?

An oft overlooked/underplayed issue by those who extol the virtues of these power banks (at least they appear to have dropped the silly ‘solar generator’ term for them).

As you already have a massive 300ah lithium battery, just get a 150w inverter.

I theory your current 12v will charge the 24v battery 5-6 times. The portable unit will do it 1-2.

You engine will charge the lithium while driving and put the money saved to a b2b so you can charge your 300ah while driving more efficiently.

Great advice.

Ian

 

[PaulC70]

How are you planning on charging the ecoflow?

As you already have a massive 300ah lithium battery, just get a 150w inverter.

I theory your current 12v will charge the 24v battery 5-6 times. The portable unit will do it 1-2.

You engine will charge the lithium while driving and put the money saved to a b2b so you can charge your 300ah while driving more efficiently.

So on my setup i already have a second battery box with pos / neg leads already running to it, for some reason though there's no battery at all, I suspect that previous owner took it with them.
So, could I simply connect a 150w inverter to those leads? Sounds (on the face of it) a simple solution to my needs?

An oft overlooked/underplayed issue by those who extol the virtues of these power banks (at least they appear to have dropped the silly ‘solar generator’ term for them).
Ian

My thought process was that I could charge it every third / 4th day +/- via cigarette lighter on the go but since found a youtube vid saying thats likely to take days not hours.

 

[bigtwin]

So on my setup i already have a second battery box with pos / neg leads already running to it, for some reason though there's no battery at all, I suspect that previous owner took it with them.

There’s a solution staring you in the face right there; fit a second battery. Mind you, you already have a decent capacity.

So, could I simply connect a 150w inverter to those leads? Sounds (on the face of it) a simple solution to my needs?

Yes, you could, suitably fused though.

My thought process was that I could charge it every third / 4th day +/- via cigarette lighter on the go but since found a youtube vid saying thats likely to take days not hours.

They’re not the panacea that many think they are but they are seen by many as an easy, if expensive, solution (given their inherent shortcomings).

Ian

 

[autorouter]

If you have a 300Ah Fogstar lithium 12V battery, that's 300 x 12 = 3600Wh, which is more than ten times the capacity of the scooter battery (298Wh). That 300Ah battery would comfortably run a 2000W inverter, so would have no trouble at all powering a small inverter of say 150W or 200W, which would run your scooter battery charger.

If buying an inverter, I would go for a Pure Sine Wave type, not a Modified Sine Wave or Quasi-sine Wave. They cost a bit more, but they are kinder to any electronic device you might plug into it. Pure Sine Wave is a smooth waveform just like you get from a house supply. Modified Sine Wave has sharp steps and a generally jagged waveform, fine for things like heaters and kettles, but can have unpredictable effects on electronic devices like chargers. I've found that if it doesn't prominently say Pure Sine Wave (PSW) in the ad, then it won't be PSW.

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[PaulC70]

There’s a solution staring you in the face right there; fit a second battery. Mind you, you already have a decent capacity.



Yes, you could, suitably fused though.



They’re not the panacea that many think they are but they are seen by many as an easy, if expensive, solution (given their inherent shortcomings).

Ian

A second battery won't help me when it comes to charging the mobility scooter battery though, hence my thought of having one of these bluetti/anker/ecoflow power banks as I can simply plug in the charger if you see what I mean.

However it does look like an inverter is actually likely to be easier.

If you have a 300Ah Fogstar lithium 12V battery, that's 300 x 12 = 3600Wh, which is more than ten times the capacity of the scooter battery (298Wh). That 300Ah battery would comfortably run a 2000W inverter, so would have no trouble at all powering a small inverter of say 150W or 200W, which would run your scooter battery charger.

If buying an inverter, I would go for a Pure Sine Wave type, not a Modified Sine Wave or Quasi-sine Wave. They cost a bit more, but they are kinder to any electronic device you might plug into it. Pure Sine Wave is a smooth waveform just like you get from a house supply. Modified Sine Wave has sharp steps and a generally jagged waveform, fine for things like heaters and kettles, but can have unpredictable effects on electronic devices like chargers. I've found that if it doesn't prominently say Pure Sine Wave (PSW) in the ad, then it won't be PSW.

Thanks for this, and everyone else thats contributed, Im a bit thick when it comes to these things so need to ask the daft questions!
I think it looks like a pure sine wave 150 to 200w inverter will be the best bet. Leaving on Friday or Saturday so gonna look on amazon next day i think.

 

[PaulC70]

Hmmm looks like amazon and ebay and awash with inverters mainly 1000w plus!
Wouldn't something like the victon inverter here do ? https://offgridpower.solutions/shop/victron-energy-phoenix-inverter

 

[PaulC70]

Right purchased from Offgrid RogerIvy and nigelivy

 

[autorouter]

When it is on, an inverter draws a small current even when nothing is plugged into it. It's not a big problem, but can be a drain on the battery over a few days. It's a good idea to switch it off when you're not actually using it.

To make this easier, some inverters, including the Victron ones, have a pair of terminals to wire in a remote on/off switch, if the switch on the inverter itself is a bit inaccessible.

 

[PaulC70]

When it is on, an inverter draws a small current even when nothing is plugged into it. It's not a big problem, but can be a drain on the battery over a few days. It's a good idea to switch it off when you're not actually using it.

To make this easier, some inverters, including the Victron ones, have a pair of terminals to wire in a remote on/off switch, if the switch on the inverter itself is a bit inaccessible.

Its not going to be in the most accessible place I have to admit but not too much of a pain. I'll fit first and see how i get on

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[Pukka]

Our inverter has a remote switch, so it's off when not in use.