Charging ebike battery from a leasure battery?

[CourtIOW]

Charging ebike battery from a leasure battery?

Folks I am wanting to get at least 1 full charge into my 700wh ebike battery (4a charger) while in my van.

So I am looking (and getting confused) by Charging systems etc..
But what my main thought/question is 1st, if I had a FULLY charged leasure battery, could I charge my 700wh battery from it, guessing using a inverter?
If so what would be the recommended size/minimum of battery?
And does the inverter need to be sine or there other ? and any particular size?

That will get me going, then will look into the Charging of the leasure, top up via solar and split Charging system. ?

Basically want to know is it possible without a load of batteries.

Thanks all.

 

[Barbara_Reed]

Yes, you could. The leisure battery would need to have about twice the capacity of the bike battery if it's Lithium. More if lead acid. As to pure sine wave, depends on your charger but they aren't that much more expensive. You would need an invertor that has twice the continuous charging rate to cope with start up loads in most applications, probably also your charger. Add a solar panel if you like, that way you will still have some juice for your van water pump etc.

 

[CourtIOW]

Great thanks ?

 

[yorkshire89]

If you have a lead acid / AGM leisure battery you shouldn't let it drop below 50% charge
If you have a LiFePO4 battery (expensive) this can go down to 20% charge

My maths could be wrong here (feel free to correct me) but I think you would want at minimum either...
140Ah AGM/lead acid @ 12V = 1680Wh - 700Wh = 980Wh (58.33% charge left)
100Ah LiFePO4 @ 12V = 1200Wh - 700Wh = 500Wh (41.67% charge left)
Based on general sizes I've seen them in.

You also need to factor in the inverter efficiency into that. High quality will be 90-95% efficient, cheaper ones down to 75-85%.
So you may need to size up the battery to compensate for that.

 

[CourtIOW]

Awesome thanks. Perfect ?

 

[S13]

LiFePO4 can go down to 0% if you like, and even then you probably have some left over. Thats because rated capacity is usually at 1C, meaning 100A for a 100Ah battery. But at the lower currents we usually run at, like 10A, it will do 5-10% more than rated.

I run a 160Ah LiFePO4, which i can get 170Ah out easily, and i often do. And it degrades nowhere near as fast as my 2 lithium emtb batteries (LiFePO4 is just sooo nice and easy to work with)

The 160Ah contains effectively 170Ah * 13V = 2210Wh. Given ~90% efficiency of inverter and charger combined, that makes it i can charge my 500Wh batteries 4 times.

So to charge a 700Wh battery you would need at least an ~800Wh source (provided a good quality inverter). At ~13V that makes about 61Ah LiFePO4. So technically you could perhaps get away with a 60Ah, but you would be pushing it to the limit each charge. Safer would be an 80Ah, or more practical a 100Ah (these are just more common).

If you were to go lead acid, you'd be looking at 130Ah or up.

Do get a sine inverter, your charger probably requires it. Power should obviously be rated higher than your charger. Most inverters can handle higher inrush currents for a couple of seconds. For example, Victron inverters can do almost 200% rated power for a couple of seconds. So no need to worry about that too much.
Your 4A charger would draw something like 200W from the plug (im estimating, look it up to be sure), so go for at least a 250W inverter.

 

[CourtIOW]

Superb reply thanks. Really useful info ?

 

[RickBullotta]

FWIW, I use one of these to charge my eMTB, using the batteries from my various home tools (snow blower, chainsaw, lawn mower, trimmer, leaf blower):

Amazon.com : EGO Power+ PAD1500 Nexus Escape 150W Power Inverter Battery and Charger Not Included : Garden & Outdoor

 

[Cyclopath1000]

I actually am doing what you propose. I bought two new agm gel type batteries for my RV and decided to use the old ones to recharge my Shimano e 8000 ( 504 size so smaller than your ebike battery. They are group 24 size batteries that I trickle charge at home and take with me. Each batt is good for one recharge of my ebike and I have 2 e8000 batts so this setup yields 4 total rides off the grid...eventually I'm gonna upgrade the solar panel on my rig with a mppt controller and recharge the old batts so if sunny I might get a week of riding. This setup cost $69 for an inverter at Walmart. Yes a lithium ion battery would even be better but so far what I detailed above works.

 

[CourtIOW]

Great, just what I wanted to know ?

 

[Slapbassmunky]

Hey dude, I was looking for a similar setup to you. Tayna recommended this to me, you'd get a charge out of it, but ideally you want two, or it would want to go on a switchable split charge setup, which is very easy to implement.

YPC100-12 Yuasa YuPower Cyclic VRLA 100-12 Battery

<h4>Yuasa</h4> <i>Advanced Engineering, Premium Quality, Unmatched Reliability</i> GS Yuasa located in Japan, all started in 1895 and is one of the biggest battery manufacturers in the world. Manufacturing batteries for the automotive, commercial and infrastructure markets. Yuasa Battery, Inc...

www.tayna.co.uk

They told me that short of going with a lifepo4 setup, this has the best cyclic and deep discharge performance of all non industrial lead acids.

You will need a pure sinewave inverter that spits out at least 300w constant. Battery chargers are horrible to inverters. Make sure it's all connected with properly sized cable/fuses/crimps etc.

Looking at your username I'm probably no more than 10 minutes from you ?

 

[CourtIOW]

Great cheers bud. Ye will be looking at a split charge system with 1 battery, also poss a solar setup to trickle in when able to.
Yep I on the sunny Isle of Wight

 

[Cyclopath1000]

So how finickey is a oem Shimano charger ? It's working voltage is 100- 240 volts I believe. I'm sure a pure sine wave inverter is obviously a better item than the $69 Walmart variety. But is there any hard data on the need for a pricey sine wave inverter. I do understand that amongst the hard core purveyors of electrons the sine wave inverter is basic but in this application????

 

[Slapbassmunky]

It totally depends in the input topology of the charger. It's like most things in life, why buy a square wave or modified sinewave inverter when you could spend that bit extra to have total piece of mind and get a pure sinewave one? Then you know it will absolutely work with everything.

FYI, I tried out a cheap Joycube charger for a Carrera last year on one of my square wave inverters and it emitted an extremely high pitched squeal, and never worked again ?

 

[Cyclopath1000]

I looked at pure sine wave stiff and it isn't very pricey for a simple one.

 

[urastus]

embn have done a video that might interest you

 

[Slapbassmunky]

embn have done a video that might interest you

There's so much bad advice in that video it's beyond belief. Some of it down right dangerous, some of it completely superfluous. Any 'electronics expert' that thinks a half charged leisure battery is going to be fully charged after an hour and a half's drive, through two bits of speaker wire and a pissy little schottky diode, is off his rocker.

 

[Cyclopath1000]

Some of the videos I have watched seem a bit extreme. There are people who want to have the ability to have a completely off the grid life for extended periods of time not using fossil fuel. And on The other extreme are the people who are going to spend the night or two out and don't have a plug.

 

[Binhill1]

Some of the videos I have watched seem a bit extreme. There are people who want to have the ability to have a completely off the grid life for extended periods of time not using fossil fuel. And on The other extreme are the people who are going to spend the night or two out and don't have a plug.

Yes good luck to them all.

 

[Barbara_Reed]

embn have done a video that might interest you

Well, only in as much as not realising you could pack so much misinformation into so short a time.

 

[routrax]

Well, only in as much as not realising you could pack so much misinformation into so short a time.

I though that when I watched the video a while ago.

 

[CoreyB]

I have a Jackey 1000 that I keep in the bed of my truck. I am able to charge 3 Levo SL batteries, simultaneously, to 100% from about 30% while we ate lunch. I also have a 110vac outlet in the bed of my truck that has a 400 watt output, so I can charge the Jackery while it’s charging the bikes if I’m driving or running the truck.

 

[Waynemarlow]

There's so much bad advice in that video it's beyond belief. Some of it down right dangerous, some of it completely superfluous. Any 'electronics expert' that thinks a half charged leisure battery is going to be fully charged after an hour and a half's drive, through two bits of speaker wire and a pissy little schottky diode, is off his rocker.

Why so, you need to back up that statement ?

 

[Slapbassmunky]

Why so, you need to back up that statement ?

Well. Just for a start, have a look at the size of the lead coming off your alternator, then have a look at the cabling supplied in commercial split charging setups. Also the diode he's using is for a bridge rectifier application so will cope with at most 50% duty cycle. It's magnitudes of sizes too small. Also completely misleading people about how long it actually takes to fully charge a lead acid battery. Seriously, he says he designed mobile radar applications in the late 60's. Well guess what I work on in 2021?

 

[ChrisCM]

This may be useful, it’s a post I placed on a Facebook group I’m a member of :


As a follow on to my last post about my new bike, I though it may be useful for those with electric bikes to know about charging from the van’s battery system.
My bike has a Bosch motor and 625Wh battery, it’s supplied with a mains 2 Amp charger with a rated input of 100-240v 50\60 Hz 1.6 Amps. I have fitted a Victron 375W 240V inverter in my van. Ohms law suggests that the charger should draw a maximum of 160W, well within the rating of the inverter, at 100% efficiency one could expect a draw of 13.3 Amps. When I plugged the charger into the inverter with the battery connected charging started immediately but the inverter 12V current draw was only 7.5 Amps (90W) Given that the rated efficiency of the inverter is 89%, and that the charge time is specified as 8.8 hours from flat, (an unlikely scenario) which would consume 66 Ah I think that this is pretty good and well within the capacity of my batteries (190Ah) and solar/vehicle charging system. I hope that this may help anyone deciding whether to or what size inverter to fit for electric bike charging.

 

[Waynemarlow]

Well. Just for a start, have a look at the size of the lead coming off your alternator, then have a look at the cabling supplied in commercial split charging setups. Also the diode he's using is for a bridge rectifier application so will cope with at most 50% duty cycle. It's magnitudes of sizes too small. Also completely misleading people about how long it actually takes to fully charge a lead acid battery. Seriously, he says he designed mobile radar applications in the late 60's. Well guess what I work on in 2021?

I know it’s a bit marginal in cable size for the length but 2 x 2.5mm sq cables is probably larger than the cable from the alternator to the battery. He’s got 20 amp fuses on each cable, so evidently the 1/2 discharged 140 amp hour battery is not drawing the 40 amps which two 79 strand speaker cables can handle. The battery is not a dead short and will only draw what it can to recharge itself.

You also quote the size of commercial systems cables, most will allow in emergencies for the engine to be started from the leisure battery, that means cable size for maybe 80 amps.

Those shotkey diodes which I think without looking up the data sheets will handle 15 - 20 amps each in a forward draw off ( a diode of that type which is designed to be mounted on a heat sink is of that order, just look at those actually in the alternator) of which he has two, should handle the foward current Ok. Perhaps if you could ID which diode he has used then we would know exactly what current they can handle.

Now a 1/2 discharged leisure battery is not 140 amp/ hours but more like only 30 - 40 amp hours at most ( you only can discharge probably 70 amp hours total ) most vehicle alternators would easily handle that load over a couple of hours, any vehicle of any size with AC and all the mod cons is more like 60 amp hours charge rate or even higher. You get the picture with the car running constantly the car draw off requirements will easily give quite a spare rate to charge the leisure battery.

I know from a perfect engineered solution this may seem a bit Heath Robinsonish but it works, has done for some time, why rubbish it ?

 

[Slapbassmunky]

I know it’s a bit marginal in cable size for the length but 2 x 2.5mm sq cables is probably larger than the cable from the alternator to the battery. He’s got 20 amp fuses on each cable, so evidently the 1/2 discharged 140 amp hour battery is not drawing the 40 amps which two 79 strand speaker cables can handle. The battery is not a dead short and will only draw what it can to recharge itself.

You also quote the size of commercial systems cables, most will allow in emergencies for the engine to be started from the leisure battery, that means cable size for maybe 80 amps.

Those shotkey diodes which I think without looking up the data sheets will handle 15 - 20 amps each in a forward draw off ( a diode of that type which is designed to be mounted on a heat sink is of that order, just look at those actually in the alternator) of which he has two, should handle the foward current Ok. Perhaps if you could ID which diode he has used then we would know exactly what current they can handle.

Now a 1/2 discharged leisure battery is not 140 amp/ hours but more like only 30 - 40 amp hours at most ( you only can discharge probably 70 amp hours total ) most vehicle alternators would easily handle that load over a couple of hours, any vehicle of any size with AC and all the mod cons is more like 60 amp hours charge rate or even higher. You get the picture with the car running constantly the car draw off requirements will easily give quite a spare rate to charge the leisure battery.

I know from a perfect engineered solution this may seem a bit Heath Robinsonish but it works, has done for some time, why rubbish it ?

Go for it, I literally don't have the patience to argue with you. Let me know what fails first.

 

[Waynemarlow]

Go for it, I literally don't have the patience to argue with you. Let me know what fails first.

An awful lot of vans have done just this and have successfully been operating for years.

 

[Slapbassmunky]

An awful lot of vans have done just this and have successfully been operating for years.

Yep, using the resistance in the cable to limit the charge current. Dosen't make it the right way of doing it or remotely safe. I like to have a cigarette when filling my motorbike up, it's never been an issue....

 

[urastus]

Yep, using the resistance in the cable to limit the charge current. Dosen't make it the right way of doing it or remotely safe. I like to have a cigarette when filling my motorbike up, it's never been an issue....

I'm no expert, and have minimal electrical knowledge, but I don't think anyone is suggesting using a small cable to limit charge current. I was surprised to hear that the dude (ray) in the video was so wrong - he does all his own stuff (charging on the road etc) and seems to have the knowledge to back it up. However, if he's wrong he is wrong. It did make me think of the pissy little leads that all battery chargers have though.

16 amp charger: