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View Full Version : On-board charger... Or not?



michaelplogue
05 December 2010, 0654
Hoping to get some input here. I can't really decide whether to go with on-board charging, or to utilize that space for more battery cells.

For those of you who have already built - or are in the process - I'd like to hear what you've done, and your reasoning behind your decision. Both options have their positives and negatives, but I'm on the fence as to what to do......

teddillard
05 December 2010, 0709
My theory was based on building a light, quick bike with limited range- 15 miles, but only 250lbs. Lead "beta" batteries, to be replaced by some form of lithium later. Figuring I'd just go for short fast rides, not commuting or any application where I'd be sitting for long enough to charge it, I opted for no charger onboard.

As it turned out, I have extra space, and ended up mounting the chargers on the bike, just because it was more convenient to plug the thing in. The added space was not a sacrifice, and the added weight was only a few pounds. The theory that I could throw the chargers into a courier bag or pack just proved to be too much of a PIA.

Phantom
05 December 2010, 0736
I use my Brammo Enertia for commuting. My commute plus the occasional errand would typically only require that I charge it at home. In the past ten months, I have only charged it away from home twice. I had a close-call that almost has me seaching within three miles from home. The freedom to plug into any 110V outlet for a charge helps your peace of mind, but it may not be needed if you are always careful.

I look at it like an insurance policy.

Richard230
05 December 2010, 0803
When I was working, I would ride my GPR-S to work and park it next to my first floor window and charge it with an extension cord plugged into the wall outlet under my desk. Although I could have ridden there and back on one overnight charge, charging at work provided a little more oomph on the ride home and no doubt lessened the stress on the battery pack - which eventually crapped out anyway due to too much running at max C.

Nuts & Volts
05 December 2010, 0850
I have an on-board charger because I had room and it was not to much weight. It allows me to take longer one way trips, making the EV more useful. I also like to have the batteries charged because the batteries have much better performance from 60%-100% SOC.

If you have the room and the charger weighs less than 10 lbs then put it onboard. For your needs I think you should try to find a small, light, and low power charger that is your "insurance policy" and keep the big charger at home.

Kyle

DaveAK
05 December 2010, 1053
I was actually going over this yesterday, and I've come up with a plan that I'm going to try out. So here's what I'm going to do:

Off board charger 88V@15A, (may double this to 30A), for bulk charging and/or until first cell hits HVC. Then switch to on board 3.65V@2A individual cell chargers, (like wot Ed does), for cell balancing. This will give a decent charging time, balance the cells with out the need for shunting or any other type of balancing circuit, and allow for charging away from home.

If I can get up to maybe 5A on board without too many problems I'll try that as it will be more useful to me for an emergency charger that way, but the primary use for the on board charging will be cell balancing, so 2A should be just fine as the bulk of the charging will be complete at that stage.

BaldBruce
05 December 2010, 1832
I like Dave's idea, but implemented Kyles. A small lightweight charger on board for the recharge at work Richard did is the best IMO.

My EV pickup truck uses a special induction charger that is hardwired in my garage. I have had to limp home several times because I had no on-board charger and my planning wasn't effective.

__Tango
07 December 2010, 0125
I am not going to have onboard charging for the first rev on my bike. I went with the idea of packing the thing as full as possible with batteries. If i get ambitious, i may try to create a mount for the charger in a saddlebag configuration that can be removed or added depending on whether or not i think i'll need it.

electrician
07 December 2010, 0809
It seems to me after reading everyone's input, that a large charger at home and a small lightweight charger on the bike for emergencies is the best set up. You may not always need your on board charger, but it will be worth its weight in gold if you ever need it.

frodus
07 December 2010, 0912
Yeah, I'm actually considering a small offboard charger, but I've got room between the fairings and the frame where I can't easily put anything else.... so it kinda makes sense for me.

It'd really have to be thought out, I mean, how often do people charge somewhere other than home, and how fast do they need to charge?

teddillard
07 December 2010, 0924
Yeah, the rub is that on the road you would normally want a fast charge, right? That means a big charger, unless we're talking an 8hr charge at work. Thinking you're going on your morning cafe run and then recharging in an hour over a burger isn't going to work without some weight. At home, where you can wait for a recharge, you can also have a big off-board charger that could recharge quickly.

Still, a medium to small onboard charger seems to make sense... mine will recharge in around 4 hours.

DaveAK
07 December 2010, 0930
I agree that the large charger would be better suited on board with the smaller one at home, but reality sucks. I'm designing a small onboard individual cell charger mainly for cell balancing purposes, charging will actually be a secondary function. However, it would allow for trips longer than half my range if there's some where to charge.

I've found several potential single chip chargers, up to 10A even, but finding the right one is proving a little challenging.

frodus
07 December 2010, 1016
there's a guy on fleabay selling Vicor 48V to 3.3V DC-DC converters for like $10 and they're 75W output. Just need a 48V front end. They're trimable up to 110% or 3.63V. I've got some 3.7V ones.....

DaveAK
07 December 2010, 1056
there's a guy on fleabay selling Vicor 48V to 3.3V DC-DC converters for like $10 and they're 75W output. Just need a 48V front end. They're trimable up to 110% or 3.63V. I've got some 3.7V ones.....
My goal is to try and design something repeatable that others might be interested in. I'm also looking at a smart battery type of approach, (for the next EV that I'll most likely not ever build :)). I'm going to check out those Vicors though, because that would certainly work. Especially if I don't get any further with all the stuff that's rattling around in my head.

frodus
07 December 2010, 1150
well, they're the power side of things and only have to be trimmed or enabled/disabled. You could use a microcontroller to do those things as well, which is nice. I built one a few years ago using 50W VI-200 series modules for SLA batteries. Worked pretty well, but cost was higher than these.

You can find them all the time too, 3.3V is a popular voltage. I know there are other brands that are cheap as well, and they're the same footprint.

michaelplogue
07 December 2010, 1216
I am not going to have onboard charging for the first rev on my bike. I went with the idea of packing the thing as full as possible with batteries. If i get ambitious, i may try to create a mount for the charger in a saddlebag configuration that can be removed or added depending on whether or not i think i'll need it.

I'm thinking that this is going to be along the lines of what I might do. Have the bike loaded to the teeth with batteries, an put the chargers in removable saddle bags. That way, whe dealing with known distances - such as a daily commute - I can leave the chargers at home. And when out exploring, I can bring the full set of chargers along - for a quicker charge - just in case I miscalculate my range.

Thanks for all the input guys!

EVcycle
07 December 2010, 1601
Nope. None on the 3+ plus bikes we have had so far.

Something else to get wet or cause an issue.

Pack all the batteries it can stand and know its limits.



Just another opinion - Ed

harlan
07 December 2010, 1924
My bike is my primary form of transportation so I like having the flexibility to charge wherever. I don't see thee need to having a big charger at home and a small one on board. Usually when I'm at home its staying parked for the night and when I'm on the road I want the fastest charge possible so something in the 800W-1200W range is a good medium between size and speed.

DaveAK
07 December 2010, 1946
I agree that there isn't a need to have a big charger at home and a small one on board as far as I can see. But there might be constraints in design, cost and usage patterns that dictate your choices. That's why I'm doing what I'm doing. It isn't perfect but I think it's the best solution for me. At least until tomorrow when I'm sure I'll think of something else!

__Tango
07 December 2010, 1948
and as an aside for me. The project is getting long in the tooth, and i want to get to riding it dammit! By not worrying about how to mount/setup the charger for onboard, that's one less thing standing between me and my EV grin. :)