Expected range of a 8Ah SLA at 48v...?

[Iristrauma]

Thought I would post a couple of questions I need definitive answers to regarding my new E-Bike build fellas..!
I am awaiting a 48v 1000w rear hub motor from China. Looks ok and have read that these are just fine and do what they say out the box. I am going to run it for a while using Mobility scooter SLA 12v x4 in series, I just wanted to know what sort of useable range at 75% throttle would I get out of a charge..? I would also like to know the speed (MPH) this motor is likely to get up to using said SLA's given that LiPo are clearly the power option. I am only 10 stone and the bike is aluminium. The SLA's only weight 8.4kg mounted on home made front/top frame panniers.
I am also thinking of getting 5000mah 3 x 5cell 18.1v Lipos from Hobbyking, but seriously how many miles could one expect out of such a small capacity..?

 

[vanilla ice]

To get a good estimate you need to know how many amps your controller pulls. I bet it would give good range with a very weak controller.

 

[neptronix]

With a 1000w motor kit, you will be running at least 20 amps, so you will be beating the crap out of those 8ah SLAs and you will get probably 4ah of out of them, and lottsss of voltage sag so your performance will be lackluster too.

On an equivalent 8-10ah lipo pack at that amp draw, you will get 100% of the capacity and your voltage sag will be very minor, maybe 1 volt of sag and you won't be pushing the batteries very hard so they'll live a long life..

Thus you will get twice the range from the equivalent lipo, double to triple the lifespan, with a fraction of the weight.

 

[dogman dan]

Around the block.

Seriously this time, 5 miles tops, and 2 miles if you want your batteries to last. Slas are that poor a performer. This comment will raise objections, but who cares how far a guy can pedal a bike. I'm talking about no pedaling.

 

[auraslip]

https://sites.google.com/site/shelbyelectro/electro-tech/battery-tech/lead-acid-batteries-do-not-belong-on-an-ebike

 

[Ykick]

Dogman's being very kind - 4 miles from 8Ah SLA is my 225lb personal best. And they won't last long at those rates either.

OTH - 5Ah Lipo is an honest 5 miles and that's only because in order to maximize life and prevent pyrotechnic failures most folks will only pull 3.5-4Ah out of a 5Ah brick. They're small and easy to carry more Ah capacity than you need. Believe me, it's hard to have excess range on an eBike.

 

[Spacey]

To put it in perspective I just rode 12 miles to work at above 30mph up big hills and still had 30% left in the tank from a 66V 11.6AH Lipo pack pulling 40amps peak and 12A to 15A on the flat.

That is totally without pedaling one bit, going 16mph would get me 40 miles I reckon.

 

[dogman dan]

Yeah. Around the block wasn't that far off, if riding 25 mph.

 

[Uncle Ron]

...5 miles tops, and 2 miles if you want your batteries to last. Slas are that poor a performer. This comment will raise objections, but who cares how far a guy can pedal a bike. I'm talking about no pedaling.

Dogman,

I have no objections, although with new SLA's it might be 6 miles top, with sag already starting to set in, with maybe another 3 miles of range with increasingly disgusting sag. The only reason I'm speaking with only direct SLA battery experience is to let him know that you are pretty close to reality in your answer, and not to expect significantly, if any, better.

 

[vanilla ice]

Does anybody even make like a 5 amp 48v controller? Probably not, but thats still 250 watts. Good enough if all you're looking for is some assist with your pedaling. Oh wells, take her super easy with the throttle and you might see some decent range. Otherwise what these guys said is true. It will work at 20 amps, but the range is going to be lousy.

 

[PedalingBiped]

If you pedal hard and keep the amps below 10 then you might get 5 miles out of them.
Been there, done that. Most of us have. You only get about half of your amp hours in SLA due to the internal resistance. So 3 1/2 Amps available.

Use them to run up to the store or something but they won't be very good on a commute.

 

[Iristrauma]

Thanks for the input guys. I am leaning towards these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=13380
3 of these in series giving 55.2v but only 5Ah.. Cheap enough and light enough to have two packs of 3 bricks in the panniers.

Are the 20c discharge ok for a 1000w motor under heavy use..? I dont want to pedal much at all even uphill so will punish the batteries quite a bit.
Is this charger ok http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10452 and do I need a seperate power supply for the charger.? Im a little confused.

I want to be able to have the batteries seperate and not soldered in series, rather an adapter that I plug 3 LiPo's into to make the 55.2v pack. This way I can still use them for my RC cars and
charge them seperately.

 

[Ykick]

Sounds like you're describing 15S2P which in my experience is more like 58-60V 10Ah. Plenty power for hills on a 1000W 20-30 Amp controller system.

That charger will need a 12-14V power supply. Dogman recently mentioned a different one (iMax?) that has the AC included. But all those seem very cheap and slow to me but will work.

Thanks for the input guys. I am leaning towards these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=13380
3 of these in series giving 55.2v but only 5Ah.. Cheap enough and light enough to have two packs of 3 bricks in the panniers.

Are the 20c discharge ok for a 1000w motor under heavy use..? I dont want to pedal much at all even uphill so will punish the batteries quite a bit.
Is this charger ok http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10452 and do I need a seperate power supply for the charger.? Im a little confused.

I want to be able to have the batteries seperate and not soldered in series, rather an adapter that I plug 3 LiPo's into to make the 55.2v pack. This way I can still use them for my RC cars and
charge them seperately.