Help with on board battery charging (1 Viewer)

[Willhamburger]

can I charge a lithium battery via my inverter? Or would I need to access electric hook up.
Battery is for mobility scooter. Would only charge via the inverter when on the move.

 

[cmcardle75]

You can in theory. However, it is likely that your mobility scooter's battery will be larger than your leisure battery, so it will soon go flat. You'd need a tonne of solar (and only charge in sunshine) or EHU really. If being able to do this will be transformative for you, it may be possible to re-design your electrical system to enable it. However, it will be expensive to do so, involving large lithium battery banks and lots of solar panels/large B2B chargers and MPPT controllers.

 

[cmcardle75]

You can in theory. However, it is likely that your mobility scooter's battery will be larger than your leisure battery, so it will soon go flat. You'd need a tonne of solar (and only charge in sunshine) or EHU really. If being able to do this will be transformative for you, it may be possible to re-design your electrical system to enable it. However, it will be expensive to do so, involving large lithium battery banks and lots of solar panels/large B2B chargers and MPPT controllers.

Just spotted the "on the move". That should be fine, provided you have a B2B charger rated in the same ball park as the lithium battery charger. I would hesitate to do this on a split charge relay unless you have tested it for sufficient charge capacity.

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[Willhamburger]

Thank you. My owners manual tells me the leisure battery is charged from the alternator when the engine is running but that’s all I know. Electrics is a mystery to me. If we go down the lithium route it may make sense to buy the larger rated battery (30 mile range rather than 15 mile range) 37ah compared to 19ah. That should reduce the need to seek electric hook up. We don’t mind paying for sites but prefer quieter places.

 

[autorouter]

I agree with cmcardle75, a big lithium battery connected direct to the alternator with a split charge relay might well cause problems. This can be solved by using a Battery-to-Battery (B2B) charger which will control the charging from the alternator to the battery. It will avoid overheating the alternator, and will properly charge the lithium battery.

A 60A B2B charger will output 12 x 60 = 720 watts. A big battery, perhaps 1440 watt-hours capacity, will take 2 hours of driving to recharge from flat. If the battery is smaller, and/or you are happy with longer hours of driving, you could use a 30A B2B. For comparison, a 1440Wh battery is equivalent to 1440/12 = 120Ah, about the size of an average leisure battery.

Edit: just seen your post. A 37Ah battery will charge OK with a 30A B2B in just over an hour of driving, if it's 12 volts. Is it a 12-volt battery? That is between 12 and 14V?

 

[Willhamburger]

Not sure if this is relevant but the spec sheet says 963 watt hours

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[Willhamburger]

My inverter is rated at 600w

 

[cmcardle75]

I agree with cmcardle75, a big lithium battery connected direct to the alternator with a split charge relay might well cause problems. This can be solved by using a Battery-to-Battery (B2B) charger which will control the charging from the alternator to the battery. It will avoid overheating the alternator, and will properly charge the lithium battery.

A 60A B2B charger will output 12 x 60 = 720 watts. A big battery, perhaps 1440 watt-hours capacity, will take 2 hours of driving to recharge from flat. If the battery is smaller, and/or you are happy with longer hours of driving, you could use a 30A B2B. For comparison, a 1440Wh battery is equivalent to 1440/12 = 120Ah, about the size of an average leisure battery.

Edit: just seen your post. A 37Ah battery will charge OK with a 30A B2B in just over an hour of driving, if it's 12 volts. Is it a 12-volt battery? That is between 12 and 14V?

I think they're proposing to charge the 37Ah battery using a mains charger via an inverter, rather than directly via a B2B. However, the B2B will likely be needed to ensure the source leisure battery is topped up during the charge. We don't know the voltage of the mobility scooter, but they're sometimes much higher than 12V, i.e. 24V or 36V. If it is, for example, a 37Ah 24V battery, this is going to need 74Ah of 12V leisure energy. This is more than a typical 110Ah lead acid battery should be asked to provide. However, with a 30A B2B, the system should be able to keep up when driving. 60A would be better, if the alternator is powerful enough.

 

[autorouter]

can I charge a lithium battery via my inverter?

Sorry, should have read question. If you already have an inverter fitted in the motorhome, then you can use it to charge the mobility scooter battery, with the scooter battery mains charger. You'll have to check that the inverter is powerful enough (how many watts is it?) but I'd imagine it will be OK. Do you have the info from the label on the scooter battery mains charger?

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[autorouter]

If it's 963 watt-hours and 37 amp-hours, it's voltage is 963/37 = 26 volts.

 

[pappajohn]

Connect the inverter to the engine battery that way it will get full alternator current.
Normal split charge will never keep up with the drain on the hab battery.

 

[Willhamburger]

Hi, found the technical specs. Is this helpful?
Battery
24 V × 19.35 Ah × 1 Pc
12V × 19.
Ah × 1 Pc
24 V × 37.2 Ah × 1 Pc
Battery charger
Battery charger
Off-board
Off-board
Off-board
Input voltage: I1n00p-2u4t0 vVoAClt,a
gIenp:u1t v0o0lta-g2e4: 1000V-2A4C0 V,AC,
Output voltage: 29.4 VDC
Output vol
age: 25.2 VDC
Output voltage: 29.4 VDC
Output current: 2A
Output current: 3A

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[Willhamburger]

Battery
24 V × 19.35 Ah × 1 Pc 24 V × 37.2 Ah × 1 Pc
Battery charger
Input voltage: 100p-24v VAC
Output voltage: 29.4 VDC
Output current: 2A Output current: 3A
sorry copy & paste didn’t work, this is how it should have looked for the 2 batteries

 

[autorouter]

The output of 29.4V and 2A is about 60 watts, that will be taking about 60/12 = 5 amps from the 12V supply. The other output, 3A, is about 90 watts, and will take about 90/12 = 7.5A from the 12V supply.

This level of demand is quite modest, and nothing to worry about. The alternator could supply ten times that . Your 600 watt inverter will be well able to supply that as well. If you only charge when you are driving, you will have no problem.

You could also consider charging when the engine is not running, but you would have to keep an eye on the leisure battery level so that you don't run out of power.

 

[Willhamburger]

That’s good news & very reassuring. CareCo recommend charging after every use. As we usually mover every couple of days and drive for around 2/3 hours so should be ideal. Thank you to everyone for your advise. Really appreciated.

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[stevewagner]

That’s good news & very reassuring. CareCo recommend charging after every use. As we usually mover every couple of days and drive for around 2/3 hours so should be ideal. Thank you to everyone for your advise. Really appreciated.

Is your inverter a pure sine wave type? Any other could be detrimental to your mobility charger electronics.

 

[Willhamburger]

The inverter is described as modify sinewave

 

[pappajohn]

The inverter is described as modify sinewave

Listern to Lenny, a modified wave could damage the charger.
Pure waveform is identical to mains electric waveform......at least quality ones are.

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[Willhamburger]

what size inverter would I need? I only have a single leisure battery but only intend to use the charger when we are running the engine. If I need to charge the battery when stationary we will use an camp side hook up.

 

[autorouter]

I'm not sure what your setup will be. For the two outputs 29.4V 2A (60W) and 29.4V 3A (90W), is that a choice either/or, or will you run both at the same time?

I run a 60 watt battery charger (12V 5A) from a small 150 watt pure sine wave (PSW) inverter. I guess that the 90 watt charger will be OK on the 150W inverter, but I'd have to actually try it to be sure. But a 200 or 250W inverter would be OK, I'm sure.

There's a momentary surge at startup, that can trip an inverter if it's too small. I found that the 60W charger tripped a 100W inverter, but was OK on a 150W inverter.

 

[steveh57]

I would check with CareCo or the mobility battery charger manufacturer whether a modified sinewave invertor is acceptable- hopefully it will be but as others have said it may not be.

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[Willhamburger]

The 2 examples are either/or. They represent batteries available for the scooter we are looking at.
This is just one option we are looking at, we are interested in the lithium battery because of the weight saving although we may go for a normal lead acid battery. The most important thing is whether we can keep the battery charged whilst we trundle around Europe. As a complete dunce where electrics are concerned i thought that this would be the best place to get impartial advise.

 

[autorouter]

The 963 watt-hour battery can store the same energy as a 80 amp-hour 12 volt battery (963/12 = 80.25). Most leisure batteries are 95 to 110Ah. You can see that if you filled it from the leisure battery there wouldn't be much left for anything else. That's why it's recommended that you charge it while driving. It's about the same sort of size as two e-bike batteries, and lots of people use those, and charge them up by various means.

If you wanted to charge with solar power, you would need about 250 to 300 watts of solar panel. That's quite a lot, but getting more popular as panel prices fall. The big disadvantage is, you charge while the sun is shining, which is exactly when you want to be out on your scooter.

 

[steveh57]

As a complete dunce where electrics are concerned i thought that this would be the best place to get impartial advise.

I was not being critical, sorry if it came across that way, just trying to determine if the 240VAC battery charger you intend to use for you mobility battery will be ok with your modified sine wave invertor.

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[Willhamburger]

Never took it as critical, just pleased to receive any advise.