E-MTB van

[Nugs]

Hi all, was wondering if someone could check my homework?
Having sold my T5.1 fully converted (mostly by myself) van and just purchased a 3 year old T6.1, i realise the world of 12v electrics has crept on since i last did a conversion, plus my needs in the new van are considerably different.
Basically, i am doing a MTB van for away days for me and the wife, basic bench seat with plenty of storage plus secure transport for our e-bikes. I would like to have the option of charging the e-bikes if we need to, so looking at an inverter setup.
The bike chargers are rated as follows - 42v @ 2A (84W) and 42V @4A (168W) Would i be able to run them simultaneously from a 1000W inverter from a 100ah LiPo battery setup and.......
Would i be correct in assuming that this would give me roughly 4 hrs of charging?
Im looking at the Renogy kit at the moment to include -
DCC50s
Inverter/Battery
I have gone for the solar control to give me future proofing if i wish to add a panel later. And apart from a few ceiling lights and usb sockets there isn't any considerable current draws on the setup. I will look at installing a small power washer, but will probably go cordless or utilise my Bluetti EB55.
Any advice gratefully received.
Dave

 

[Pauly]

You are mixing up your maths here by comparing the output of the chargers (42V) and the rating of the invertor @ 230V

Let me do some quick sums on this

 

[Pauly]

So not allowing for any crazy losses (heat etc) then the chargers will draw relatively low current on the input i would guess around 0.5 amps and 1 amp at 230v which would equate to somewhere in the region of 350W - 400W at mains voltage so yes a 1000W invertor should be up to the job

Whats more important is using a reasonable quality pure sine wave invertor as anything electronic (like your chargers) can get upset with lower end invertors and modified sine wave units that put out choppy supply

The two items you linked look fine to me and the battery is capable of supplying the current required to run that invertor so all good, i think as a rule of thumb they say 100ah of battery per 1000w if invertor as a guide

Just make sure you use suitable size cable and fuses for those ratings

 

[Nugs]

Cheers @Pauly
If the chargers are only drawing about 0.5 to 1A, then the battery (100ah) should be more than capable as both bikes charge fully in about 3-4 hours.
Really good point about thermal losses though as the chargers do get bl**dy hot.
Oh, and cable sizes will be beefier than a mug of Bovril.

 

[Pauly]

Again though that’s 100ah of 12v power, I was looking at 230v power

It’s hard to calculate exactly as you cant measure conversion losses (mostly heat)

I think it’s safe to say it would power them both for 2-3 hours but all the info isn’t there
If you can find out the capacity of the bike batteries you could work it out a bit better

The lithium battery is 12v and 100ah so thats 1200wh (ideally around 80% usable)
If you get the voltage and capacity of the bike batteries you can see how it compares allowing a bit for heat wastage

 

[t0mb0]

If we assume that both bikes charge in 4 hours (conservative given your 3-4 hour estimate), and that they are pulling 252w together (again, conservative as they're very unlikely to pull their full rated wattage throughout the charging cycle), then we can estimate their total capacity at 252W*4H ~= 1000WH. Given your total battery capacity is 1200WH, then your battery is likely big enough to fully charge them both once, but there's not much leftover, especially once you factor in any losses due to less than perfect efficiency in the inverter (at least 10% extra). Given this, I would try and look up the actual capacity of the bikes batteries to try and get a more precise figure.

In terms of actual current draw, you should be fine as long as it's all cabled/fused correctly as your 1000W inverter should be fine with a 252W load. On the battery side, that 252W load should be drawing 252/12 = 21A (plus >10% inefficiency losses) which is a chunky draw but should be ok for a lithium battery - check the specs though.