Charging Ebike battery using an inverter from camper van battery

[Cornish Pete]

As the title suggests I want to use an inverter to charge the bikes from a battery. My van has a 135AH battery a 180watt solar panel that even in daylight does a good job of keeping the battery on top line in sunlight it does even better.
I have a small pure sine wave inverter for my laptop but not man enough to charge the above.
I will buy a 600watt inverter but the question is does it have to be the more expensive pure sine wave or will a none PSW inverter be ok for this job? lots of conflicting ideas out there on the net what do you use if you go down this road too

Thanks in advance

Peter

 

[Deleted member 4366]

You need to think about this idea a bit. The average ebike battery is about 400Wh. If you charge through an inverter and charger, you'll lose a fair bit through efficiency losses, which in the best case would be about 20%, so you'd need to take 480Wh from your battery. Which is 40Ah at 12V. You shouldn't take your battery below half way, which means that if it's in tip top condition, you have 67Ah, which is not enough to fully charge two bikes. If you only do ten or 15 miles a day, it should be OK, but if you flatten your bikes' batteries, you won't have enough. It's far simpler and more reliable to get a small generator to charge them.

 

[Cornish Pete]

You need to think about this idea a bit. The average ebike battery is about 400Wh. If you charge through an inverter and charger, you'll lose a fair bit through efficiency losses, which in the best case would be about 20%, so you'd need to take 480Wh from your battery. Which is 40Ah at 12V. You shouldn't take your battery below half way, which means that if it's in tip top condition, you have 67Ah, which is not enough to fully charge two bikes. If you only do ten or 15 miles a day, it should be OK, but if you flatten your bikes' batteries, you won't have enough. It's far simpler and more reliable to get a small generator to charge them.

 

[Cornish Pete]

 

[Cornish Pete]

I agree but I would only contemplate charging during the day when the solar panel could be putting in a 10amp charge

 

[Deleted member 4366]

You can get a wattmeter from Ebay for about £8 that will show you how much charge you get from your panels. You might be surprised by the results.

 

[D8ve]

It's risky for the campervan batteries.
Mini gen, running the engine and hookup all spring to mind.

 

[mike killay]

I have done this.
But, I only used if for two hours just to put some charge into my folder. I kept an eye on the leisure battery voltage.
I only did this on a site where there was no hook up and I was using the folder as a run around, other people also used it and it was flat after 3 days, so as I was only staying one more day, using an inverter was fine.
However, when camping for a long time, I only use mains hook up.

 

[Cornish Pete]

I have done this.
But, I only used if for two hours just to put some charge into my folder. I kept an eye on the leisure battery voltage.
I only did this on a site where there was no hook up and I was using the folder as a run around, other people also used it and it was flat after 3 days, so as I was only staying one more day, using an inverter was fine.
However, when camping for a long time, I only use mains hook up.

Was your inverter Pure sine wave or not?

Peter

 

[mike killay]

Was your inverter Pure sine wave or not?

Peter

No, it was Maplins cheapest 500 watt.

 

[Cornish Pete]

No, it was Maplins cheapest 500 watt.

Good to know big differencein price between PSW and none PSW

 

[mfj197]

If you need to charge from a 12V supply you could think about using a decent RC charger that operates from 12V. It would be the most efficient way as you're not converting twice, plus you can of course use all the shenanigans such a charger affords, such as varying the current, cut off voltage etc. My iCharger will do 10s - much more does start to get expensive.

Michael

 

[SAD12]

I prefer going off grid to more remote and quieter sites for several days at a time so I've been charging my bikes from the van batteries for the last couple of years now. I hate being hooked up, it defeats the object of the van for me.

• A cheap inverter from ebay is used, non PSW, rated at 1200w but it can't handle that much. (Cost about £35 quid.) It comfortably handles the standard bike charger though.
• Measuring the current revealed that it's pulling 8 amps out of the battery during most of the charge, this declines towards the end.
• My panel is rated at 100w and measuring the input shows it to be putting in 5 amps during reasonable sun. Nearer to 1 or 2 in overcast conditions.
• I don't do that many miles when using the bike, we just pootle about wherever the fancy takes us (2 bikes), so charged batteries to go away with and a careful eye on the van batteries works well and even allows for some TV watching/heating as wanted. We don't go mad on the bikes, they're recreational fun transport. 20 miles is the most done on one day, low power settings mostly, we need the exercise before settling down in a pub!
• I did uprate the van batteries to 2x100AH which helps share the load.
• I have been trialling a dc to dc step-up convertor and calculated that this reduces the output from the 8 amps to 5 amps. This is a similar approach to Michael's suggestion above but on the cheap. The amps and volts need to be carefully set and be adjustable.

Hope this answers your questions.

 

[Cornish Pete]

If you need to charge from a 12V supply you could think about using a decent RC charger that operates from 12V. It would be the most efficient way as you're not converting twice, plus you can of course use all the shenanigans such a charger affords, such as varying the current, cut off voltage etc. My iCharger will do 10s - much more does start to get expensive.

Michael

Hi Michael thenks for the reply could you point me in the direction (link) to such a chargr that will be man enough to charge a 10ah battery please
Peter

 

[Cornish Pete]

I prefer going off grid to more remote and quieter sites for several days at a time so I've been charging my bikes from the van batteries for the last couple of years now. I hate being hooked up, it defeats the object of the van for me.

• A cheap inverter from ebay is used, non PSW, rated at 1200w but it can't handle that much. (Cost about £35 quid.) It comfortably handles the standard bike charger though.
• Measuring the current revealed that it's pulling 8 amps out of the battery during most of the charge, this declines towards the end.
• My panel is rated at 100w and measuring the input shows it to be putting in 5 amps during reasonable sun. Nearer to 1 or 2 in overcast conditions.
• I don't do that many miles when using the bike, we just pootle about wherever the fancy takes us (2 bikes), so charged batteries to go away with and a careful eye on the van batteries works well and even allows for some TV watching/heating as wanted. We don't go mad on the bikes, they're recreational fun transport. 20 miles is the most done on one day, low power settings mostly, we need the exercise before settling down in a pub!
• I did uprate the van batteries to 2x100AH which helps share the load.
• I have been trialling a dc to dc step-up convertor and calculated that this reduces the output from the 8 amps to 5 amps. This is a similar approach to Michael's suggestion above but on the cheap. The amps and volts need to be carefully set and be adjustable.

Hope this answers your questions.

Thank you that answers my question admirably. it looks like we do the same sort of camping. We live in a small (toyota Hiace) camper for 6 months in the winter (outside the UK) and have a similar panel and battery set up there and we are off grid all the time just a 12volt fridge to run + led lighting and charging laptop and phones. We are off to southern Ireland when we get back in May for a few months and have bought the bikes for exploring and exercise, the Guinness is very fattening!!
A great help thanks again
by the way I use a BM1 battery monitor http://www.nasamarine.com/proddetail.php?prod=BM1Compact
which tells all about the state of the battery its a godsend
regards
Peter


Peter

 

[mfj197]

Hi Michael thenks for the reply could you point me in the direction (link) to such a chargr that will be man enough to charge a 10ah battery please
Peter

I use the iCharger 1010b+ which will charge and balance a 10S (36V nominal, 42V max) battery at anything up to 8 amps and operates from a 10-18V input voltage. If you need to discharge your ebike battery it will actually put that power back into the van battery as well. If you are charging two ebike batteries they actually do an iCharger 4010 duo, but it's considerably more expensive than two separate 1010b+ and has reserves of power we really don't need.

Michael

 

[Cornish Pete]

I use the iCharger 1010b+ which will charge and balance a 10S (36V nominal, 42V max) battery at anything up to 8 amps and operates from a 10-18V input voltage. If you need to discharge your ebike battery it will actually put that power back into the van battery as well. If you are charging two ebike batteries they actually do an iCharger 4010 duo, but it's considerably more expensive than two separate 1010b+ and has reserves of power we really don't need.


Michael

Michael,
Thanks just a couple of things I dont understand
What is a 10S
Do you actually use it to charge a bike battery
Does the company in the link ship to the UK
Is it easy to connect to the bike battery for charging (I have never seen a bike battery My bikes will be delivered when i get back to the uk in may).
and it looks like I have got a lot of reading to do regarding this method of charging from a 12v battery where do I start?
Thanks for your patience and help

Peter

 

[mfj197]

Peter,

10S is nomenclature for 10 cells in series, i.e. end-to-end. I was just checking the charger would be suitable for you as it will work with a 24 or 36 volt battery but a few ebikes use 48 volts. What bikes are you getting, so I can check the voltage?

I do indeed use it to charge a bike battery. Mine is a 36V 11.6Ah and the 1010b+ works very well. As I say, it will charge at up to 8 amps if you need - most chargers that come with ebikes are between 2 and 4 amps. The battery has to be able to cope with being charged at that level though. Each time you start a charge you choose the charge current (if you want to change it from last time).

The company I linked to does ship to the UK, or you can buy it from some other retailers already here. I bought it from a UK store at an equivalent price but it's gone up now.

And finally regarding connecting to an ebike battery itself, well, again that will depend upon the exact bike and battery you are getting so if you post that up we'll have a better idea. It would require making up a lead as the output from the iCharger is on two 4mm sockets.

Michael

 

[Cornish Pete]

Peter,

10S is nomenclature for 10 cells in series, i.e. end-to-end. I was just checking the charger would be suitable for you as it will work with a 24 or 36 volt battery but a few ebikes use 48 volts. What bikes are you getting, so I can check the voltage?

I do indeed use it to charge a bike battery. Mine is a 36V 11.6Ah and the 1010b+ works very well. As I say, it will charge at up to 8 amps if you need - most chargers that come with ebikes are between 2 and 4 amps. The battery has to be able to cope with being charged at that level though. Each time you start a charge you choose the charge current (if you want to change it from last time).

The company I linked to does ship to the UK, or you can buy it from some other retailers already here. I bought it from a UK store at an equivalent price but it's gone up now.

And finally regarding connecting to an ebike battery itself, well, again that will depend upon the exact bike and battery you are getting so if you post that up we'll have a better idea. It would require making up a lead as the output from the iCharger is on two 4mm sockets.

Michael

Michal

http://www.cornwallelectricbikes.co.uk/our-bikes/smartmotion/metro-step-through/
This is the bike

Things are getting clearer

Regards Peter

 

[mfj197]

That battery looks eminently suitable for charging with something like the iCharger. The only issues will be what sort of connector you would need on the end of the charging lead, and whether they use any sort of "smart" charging (monitoring temperature for example) which I doubt. Users trex and d8veh (and others) may well know the exact battery and be able to confirm details, or wait until you have the battery in your hands and can see what sort of charging plug it has. I would imagine it will be a simple plug and socket affair, like a laptop.

One technical thing to note if you do go down this route. The battery will have a Battery Management System (BMS) built in, which protects from overcharge, overdischarge, and also balances the individual cell voltages so they are all the same. This balancing is usually done when the pack is fully charged - it "bleeds" current from slightly overcharged cells to bring them back down to the same voltage as all the rest. The iCharger's default cutoff voltage for lithium ion cells is 4.1V per cell (therefore 41V for the whole battery pack) which is actually better for looking after the cells, but it's not high enough to allow the BMS to start balancing the cells in your pack. Therefore you would need to adjust the cutoff voltage on the charger to 4.2V per cell to allow it to fully charge the pack and for the BMS to do its balancing. Very easy to do. Or indeed just use the LiPo charging programme rather than the LiIo as it is already set to cut off at 4.2V on LiPo charging.

One other thing - the BMS in the battery might well not like you trying to charge at 8 amps! The charger that comes with the bike only charges at 2 amps, so maybe set the charger to use this current or just a bit higher. The charger remembers all these settings so once you've set them you never need to worry about them again.

Michael