Charging a Bosch ebike while off grid in a motorhome

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Dallyman

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Hi folks, thank you for having me as a member of your forum. I very much enjoyed reading the posts on touring in Northern Scotland. I made it as far as the Commando Memorial at Spean Bridge last year, but ran out of time. Once Covid-19 is over I want to take a couple of months up there in the Spring.
My question is, can anyone tell me how can I charge my e-bike while off grid please?
I read a thread that is 5 years old now, which basically said to get an inverter fitted. Has anyone had recent experience please?
 
We use inverter, you can buy a 12v charger for them for about £150 I think.
 
I charge my two overnight direct from my on-board inverter. Seems daft to raise 12volt to 230volt then transform it back down to 36volt but it works just fine. If there is a 12 volt to 36 volt inverter I imagine it would be far more efficient!

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I don't think it's as simple as providing the right voltage. The chargers are very expensive and I think that's because they include a lot of electronics to manage the battery. The batteries are expensive, too, so you don't want to muck them up.
Simplest answer is to get an inverter that's big enough to power your official charger. Then charge whist running the engine.
 
Thanks for that. Seems the safe way to go🙂
 
The 12V charger made by Bosch is long since discontinued. No doubt too many people tried to use it on vehicle batteries that were not up to it, either on capacity, or the prolonged charge time. From empty my 500 Bosch battery on the basic 2A 240V charger could take some 7 hours!

If getting an inverter, make sure it is a proper pure sine wave type. Anything less and you could screw up the battery management inbuilt to the charger / e-bike battery.

Unless you have very good capacity in your MH's leisure, you are at risk of flattening it. Recharging when on the move in your MH might be preferable, but you'll probably need a Battery to Battery device on you MH or you'll still be drawing too much energy.
 
Hi , inverter is what we use too. We have Lithium battery, one 100w solar panel.

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What size inverter are people running to charge their bike batts?

if you run a big, and I assume pure wave one does it waste more power. So you only need one that is just big enough?
 
Inverter size will depend on the charger. For example Bosch have their 2A 230V compact charger which might draw just under 500W. The 4A standard charger could need just over 900W. Allow a bit of overhead for the inverter inefficiency and that means a 600W minimum or 1000W (probably 1200W) rated inverter normal load.

Ideally you only want an inverter that is just big enough else it may waste a bit of power. But then you turn the inverter off if not in use else in idle it's still using some power. But you may want something bigger to also do something else. I don't understand the need myself being follically challenged but many funsters have a need to power a hairdryer.

The problem once you go to the inverter route becomes the energy source, i.e. battery. Hence whilst charging on the move, via a B2B can be beneficial as it will offer more juice (with correct wiring) than your standard relay based charger. Most batteries are rated to only charge, and more importantly discharge at certain rates. That 600W equivalent at 12V may be sustained for a few minutes, but a single lead-acid at at 50 Amp draw isn't going to be happy about that for long. Even some moderate capacity lithiums might not be impressed. You'd need to look at something called the "C" rate (which is over my brain capacity).
 
We manage to charge our 2 500wh batteries simultaneously, off grid or whilst driving.
We have 1 off 2A and 1 4A charger.
Inverter is 300w pure sine wave.
Batteries 2 x lifepo4 100AH
45 amp alternator to battery charger
275 watts solar , mppt controller.
No sweat.
When we had elderly AGM batteries, they would only manage charging one of the batteries, and did grizzle a bit.
Jon
PS the2A charger takes 80W, the 4A 160W,
so only a small inverter required.
 
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two said:
I don't think it's as simple as providing the right voltage. The chargers are very expensive and I think that's because they include a lot of electronics to manage the battery. The batteries are expensive, too, so you don't want to muck them up.
Simplest answer is to get an inverter that's big enough to power your official charger. Then charge whist running the engine.
Click to expand...
Victron inverter

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We charge 2 e-bike 10.5 Ah batteries using a 1kW pure sine inverter. Each charger takes about 7A, (measured with a clamp meter) so it pulls 14A from the hab battery when running if both bike batteries are on charge at the same time. We try to charge when the engine is running but will also charge if it’s a sunny day and the solar (100W) is piling in the amps.

We have a 30A B2B, 100W solar, MPPT controller and 100Ah LiFePO4 hab battery. We have not needed to use EHU since fitting all this.

The e-bike batteries can take quite a few hours to charge, so I suggest this is best done when you have some charging input, rather than at night. If you have EHU then it’s obviously no issue, but we wanted to avoid relying on this.
 
Kannon Fodda said:
That suggests considerable headroom compared to the labelling on the charger itself which must be some weird worst case scenario.
Click to expand...
The 2A Charger supplies approx 40V at 2A to charge the bike. 80 watts output.
At 240V from the inverter the current required is .66A, or 80watts power consumed.
Jon
 
I recently went through this process. Not a lot to add except the pure sine wave inverters do seem to vary in how pure they actually are. The first one that I tried caused the battery charger to overheat (too hot to touch). Amazingly it survived. Another inverter brand (500 W) was just fine. Like others, I would only charge with the engine running.
 
g3cwi said:
I recently went through this process. Not a lot to add except the pure sine wave inverters do seem to vary in how pure they actually are. The first one that I tried caused the battery charger to overheat (too hot to touch). Amazingly it survived. Another inverter brand (500 W) was just fine. Like others, I would only charge with the engine running.
Click to expand...
I would advise buying a good make inverter if you value anything you plug into it

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jezport said:
I would advise buying a good make inverter if you value anything you plug into it
Click to expand...

Like the Studer AJ Series 👌 😎

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We've got the smallest 275 one.
 
Just a recap on figures as some don't make sense on this thread.

The chargers for our Bosch 400 watt batteries take approx 1.5 amps at 240 volts which is 30 amps at 12v.

So if charging 2 batteries via an inverter that is 60 amps +15% for inverter inefficiency a total of approximately 69 amps.

If you want to charge both batteries at once you need at least a 250a/h battery bank if you want your batteries to last, unless you have Lithium.

On the rare occasion I have charged both batteries at the same time, I have measured 67 amps at 12v.
I only have a 1000 watt inverter if I plug both batteries in together it will trip the inverter. This is due to the hight start up current that can be drawn by switch mode power supplies if they have not been used for a while. So I plug one in then let it stabilise for a minute or two before plugging the other one in.
 
Thanks very much for such detailed information. I was considering upgrading my two 100Ah lead batteries to LiFe anyway, so that confirms I would be heading in the right direction 🙂
 
Lenny HB said:
Just a recap on figures as some don't make sense on this thread.

The chargers for our Bosch 400 watt batteries take approx 1.5 amps at 240 volts which is 30 amps at 12v.

So if charging 2 batteries via an inverter that is 60 amps +15% for inverter inefficiency a total of 69 amps.

If you want to charge both batteries at once you need at least a 250a/h battery bank if you want your batteries to last, unless you have Lithium.

On the rare occasion I have charged both batteries at the same time, I have measured 67 amps at 12v.
I only have a 1000 watt inverter if I plug both batteries in together it will trip the inverter. This is due to the hight start up current that can be drawn by switch mode power supplies if they have not been used for a while. So I plug one in then let it stabilise for a minute or two before plugging the other one in.
Click to expand...
Lenny,
Your figures don't match with my observations, summarised in post 18.
Perhaps the Bosch 500 w batteries and chargers have changed for 2020 when mine were new.
I definitely only have a 300w Sterling psw inverter and only see 250W to 260W on the Stirling power reading charging both batteries simultaneously. There is no discernable surge on startup.
In addition the Victron battery monitor usually displays a max discharge ca. 22A when charging off grid with no solar.
Maybe you are running Germany from your inverter!
Jon
 
Re post 24
A picture of our higher capacity charger as evidence.
4A at 36V is equivalent to 12A at 12V.
The slight disparity in power consumed I put down to inverter inefficiency
Jon

15983510081133462545019066288085.jpg

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Last edited:
jonasw19 said:
Lenny,
Your figures don't match with my observations, summarised in post 18.
Perhaps the Bosch 500 w batteries and chargers have changed for 2020 when mine were new.
I definitely only have a 300w Sterling psw inverter and only see 250W to 260W on the Stirling power reading charging both batteries simultaneously. There is no discernable surge on startup.
In addition the Victron battery monitor usually displays a max discharge ca. 22A when charging off grid with no solar.
Maybe you are running Germany from your inverter!
Jon
Click to expand...
Just looked at the Bosch chargers, the standard charger takes 3.5 hours to charge a 400 W battery and 4.5 hours to charge a 500 watt battery. Mine takes 2.5 hours to charge a 400 watt battery so they have lowered the charging current.
The surge on start up will only happen if the charger has not been used for months which often happens with us as one charger will be used most of the time.
 
jonasw19 said:
Re post 24
A picture of our higher capacity charger as evidence.
4A at 36V is equivalent to 12A at 12V.
The slight disparity in power consumed I put down to inverter inefficiency
Jon

View attachment 418945
Click to expand...
Your charger is rated at 1.1 amps at mains voltage (22 amps at 12v), mine is 1.5 amps (30 amps at 12v).
The 2.2 amps is for 110v.
 
My battery charger+inverter draws 15 Amps from the 12 Volt supply. Decathlon Rockrider 504Wh battery.
 
Lenny HB said:
Your charger is rated at 1.1 amps at mains voltage (22 amps at 12v), mine is 1.5 amps (30 amps at 12v).
The 2.2 amps is for 110v.
Click to expand...
I suspect that we are both agreeing with each other.
Indeed the charger input is rated at max 1.1A @230V, but the output is rated lower at 4A@ 36V.
The battery will only accept the max V or A its bms will allow.
As an aside, my chargers do heat up a bit but I suppose they are running at fairly high wattages, or my inverter could output a dirty waveform.
Jon
 

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