Charging E-Bike with a power inverter

[oldbiker]

Hi,
I have a 36V 20Ahr LifePo4 Battery and I would like to know if i could charge it with an inverter such as: http://www.amazon.com/Schumacher-PP-2200-Portable-Outdoor-Power/dp/B002CG001E/ref=pd_sim_sbs_ol_27.
I have to leave my trike outside where there is no electric outlet to plug in my charger. The inverter, if it works, would allow me to charge the Trike with my charger and then bring the inverter inside to recharge it.
Any assistance will be appreciated.

 

[amberwolf]

Depends. Lots of those things have horrible non-sine AC output, which can destroy some SMPS type chargers, especially those designed on the ragged edge already (like lots of the cheap ebike chargers). I've got a box of assorted chargers from various things that a friend has fried over the last couple years using various cheap inverters in his truck, including a big portable one sort of like that one.

Personally I'd just get a long extension cord on a reel, if I had no outlet outside and no way to take the battery off the bike to bring it in to charge, rather than using an inverter like that. It'd probably be a lot cheaper, too.

But I can envision places you coudln't do that.

 

[SamTexas]

It would not work even if the inverter produces perfect sine wave output. The battery capacity on the Schumacher is smaller than your trike battery. So your trike will never be fully charged.

Trike battery: 36V * 20Ah = 720Wh
Schumacher battery: 12V * 22Ah = 264Wh

And that's before taking into account of:
- the loss associated with the 12VDC to 120VAC conversion
- the loss associated with the trike battery charger
- the fact that the capacity of lead-acid battery in the Shumacher is greatly exaggerated
- the Peukert loss associated with drawing high current from the lead-acid battery

So, instead of lugging the Schumacher from the house to the trike why not lug the trike battery from the trike to the house?

 

[Ziggurat]

I agree with the above. Also most lead-acid batteries do not like a lot of deep discharges, the already-too-small capacity would quickly decline over time. It might work ok for a while if you are only topping up your ebike battery from light discharges, like a few Ah.

I used a booster battery similar to that (but without inverter) when I got my first LiPo charger, which took 12 V directly. I used it a couple of times while my "main" power source, an automotive 12 V, was being recharged. Neither lead battery lasted long before the charger was cutting out with a "low input voltage" error message. I was much happier when my proper power supply arrived.

 

[REdiculous]

Looks like a decent buy to me. $85 for a 400w MSW inverter, 22ah SLA and charger isn't bad, but you could make your own version with off-the-shelf parts and not spend much more than that.

It could work to charge a larger battery but you'd need to charge the Schumacher thing a few times...so, multiple trips and many hours later. If your charger doesn't die on the modified sine wave output, that is.

If the trike battery is big enough that carrying it inside/outside would be a real hassle then I would think about making my own "portable power unit". A small pure sine inverter shouldn't break the bank and a smaller lithium battery would reduce the weight of the unit, at the expense of needing many trips/charges to charge the larger trike battery. If it was me, I would probably go for the smallest 24v Ping pack and a 250-500w pure sine inverter.

 

[dogman dan]

As a way to run a radio, or maybe even charge much smaller capacity batteries like a laptop or one drill battery, fine.

But really, much too small for charging a 36v 20 ah lifepo4. And pretty yummy looking to the average thief.

Why couldn't you just carry in the 15 pound lifepo4, and charge it inside?

If the place is secure enough, perhaps a tiny generator running your charger?

Do you need a full recharge? Or just a few more wh?

What is the situation, any chance you could get a plug installed, at your expense maybe? Streetight poles in parking lots often have a place where a plug can be easily added.

 

[oldbiker]

Thanks for your efforts.
There are two main reasons for my thoughts to accomplish the charging with an inverter:
1. I live in an apartment where outside alterations are not possible.
2. The battery is in a locked, bolted down compartment. So transport inside the apartment to charge it is difficult and messy. If my patio had a gate this post would not have been posted.

The inverter seemed to be a good idea but I knew nothing of the sine wave problems. It appears the cost of a pure sine wave inverter would cost as much as another battery.
The only option left seems to be to alter the manner of attaching the battery to the trike.
Oh well its only money…

 

[REdiculous]

A small pure sine inverter isn't that expensive when you think about it - just imagine the initial purchase price spread over the useful life....

I found a 24v 300w pure sine inverter for $120 - so only $30/yr, assuming it lasts 4 full years.

A 24v 10ah Ping is $200 and a charger is $33...

 

[dogman dan]

It seems to me, that the only real solution is going to be to be able to bring the battery into the apartment more easily. Unless a longer cord would work. One disadvantage of a trike, is that it can be much more difficult to bring up to a second floor apartment, and bring inside.

I have carried similar batteries in metal toolboxes, so maybe you can build a different lockable compartment, but make it easier to remove the battery and carry inside. On my pingbatteries, I use tape and nylon strap, to creat a carry handle on the battery for such times.