Boosting the Ecotric 36V Battery with a converter.

[harryS]

Something I tried just for fun was a DC boost converter. These are used to boost a DC voltage to a higher number, a very common application, but I wasn't sure it would work with a cheap converter and the demands of an ebike. Other users say it works, so I was willing to chuck out $23 on ebay for one of these 1500W 30A dc-dc converters.

It's is cheap. My vendor threw it in a plastic bag and sent it without any packing. It arrived bent up and with a capacitor broken off. If it had been amazon, I would have made him take it back, but it's a guy in China. I soldered a new capacitor on it and it worked, so I took a 25% discount. There's a fan on the bottom, but it doesn't work yet.

Here it is when I tested it on a 36V pack. It can put out up to 90V, but I didn't go above 60V. It's rated for only 20 amps output, so it cannot do miracles.

I tried it in my fat bike with a 25A controller, putting out 58V from a 36V pack, and it would shut off any time I gave it throttle. No miracles. With a max of 20A available, no good for big bikes.

I tried it with a 20A controller in my 36V 250W folding bike, this time with 50V from a 36V pack. It gave a nice kick in performance. The watts in assist level 1 went up 20%. Top speed went from 19 to 24 mph, Both of these compare to when I put a real 48V battery on that bike.

Since this is the Ecotric forum, I put it on my Ecotric 20" fat tire folder also with a 20A controller. I use the stock 36V silverfish battery on that bike. I set the output to 50V. Worked nice. The bike did not shut off or get starved for current. Top speed of about 25 mph indicated, compared with 20mph before. I rode around for an hour without incident.

One thing I noticed. The Ecotric 36V battery would sag about 6-7 volts under throttle. I have a voltmeter on my handlebars and can watch that. With the boost converter installed, the bike voltage only dropped from 50 to 49 volts, while the battery voltage still drooped 6 volts. The converter is able to maintain the voltage, but the cost is it sucked 30A out of the battery to do this. This means that as the battery discharges, the bike won't lose performance from lower voltage. However the battery will discharge faster because it has to make up that power in the converter,

So I was pleasantly surprised. It's not a free lunch since it uses more power. You do have to set the converter so it shuts down at the proper minimum voltage for your battery. I haven't tested to see if this works.

I might use it on another ebike project to run a 48V motor on a 36V battery. . It's too unwieldy to install on my Ecotric. Wires all over the place.

 

[dhealys]

hi harry, I wonder could you help me, I have an ecotic hammer. I want to increase my miles, I currently have a 48v 13amp battery, I want to to get a 48v 20amp battery, do you know if the econtic bike will take a 20amp battery. not sure what the amp limitation is on these bike I believe it may be 20amp. can you advise.

 

[harryS]

Your terminology needs to change. Look first for the Amp-hour (AH) rating of the battery.

Amperes literally is the number of electrons per second passing thru a wire. It's a measure of flow, just like water thru a pipe. More amps need thicker wires and a bigger battery to push them. SInce the ebike controls the flow, as long as the battery is big enough to run the bike, it will work.

Amp-hours (AH), is a different term and tells you the capacity of a battery. More AH means more capacity amd more range. If the battery has the same case and fits in your Hammer, than the higher 20AH battery will work.

How much do you expect to pay? Around $450? The ECotric website says your Hammer uses this style battery?

An honest seller should tell you how many cells are in the pack. It will be a whopping 78 cell battery to get 20AH. If it's only 65 cells, it can't be 20AH,

 

[dhealys]

thanks harry for your thoughtful input. the current dimensions for the ecotic hammer battery is 76*110*370mm, but the battery im looking at is 76*110*495mm, is it possible for them to increase the cells with so little space, as most the 48v 20am batterys I see on the internet are massive. also would the controller play a role here. I noticed in one your teardown for the folding bike that the controller amp is 17-19amp, so would putting in a 2o amp battery fry this. yes your right seller honesty here. ill create a new thread for this, sorry for hijacking this post. seems like a good project, its a shame I have to be guiney pig, still the worse if my controller get fried can always replace it. sorry for some of my ignorance with regards to watts and amps. hope we can learn a lot from you, as already had. great posts.

 

[harryS]

A 48V pack needs 13 groups in seriesl, so the possible cell counts are 13x1, 13,x2, 13x5, 13x4. 13x5, and 13x6, with the last one being 78 cells. I didn't think it was possible, but by making the case longer, they can get those cells in. Unless they sell you the longer frame rail too, you won't be able to lock the longer battery into your Hammer. And then you can't use the shorter battery any more. Maybe a 48V16.5AH battery is better?

This is a picture where someone opened up his 48V 20AH silverfish. It looks like someone took a 36V20AH array (10x6 cells) and grafted the 18 cells on the right. Not a good looking job. Cells are glued together instead of being in a plastic matrix.

 

[dhealys]

thanks for that harry, on my controller (under amps heading) it says 17-22v, I confirmed with ecotic that the max amp on controller is 22, so should I pull out getting any battery that has amp greater than 22. I contacted a china seller about the 48v 25ah battery that they have and here is what he said "
"Our engineer said if for 48v battery, the controller should be 48v, and the cut off voltage should be about 41V.
If the cut off voltage of the controller is only 22v, the battery will be outage when riding.'

I don't know if they are correct as a lot of these guys are just salespeople, maybe ill just cancel my order and forget about whole thing, sorry about bugging you about this, it will be last.

 

[harryS]

"
"Our engineer said if for 48v battery, the controller should be 48v, and the cut off voltage should be about 41V. If the cut off voltage of the controller is only 22v, the battery will be outage when riding."
He is correct.

You do want the battery to be able to supply more current than the maximum needed by the controller. The controller will limit the amperes. More current available from the battery is good. Means you won't starve the controller. You're less likely to have voltage sag. The battery will last longer if not pushed to its limits. So yes, a battery with higher amps is good, and a battery with more AH increases range.