best way to add 12 volts to a 48 volt 15AH LIFEPO4 to get 60

[andys]

I tested my KLH 20 inch wheel bike with BMC geared hub today at 60 volts, and I love it. I stuck a small LA battery in series to run the test, and was careful not to run it down too far. Top speed increased from 20 to 25 MPH, and hill climbing (which was awesome already) is now even better. It spoiled me big time. I only ran it 4 miles, and the small 9AH LA battery was still at 12.55 volts. Nothing got hot.

I want to know if anyone has run the Crystalite 48 volt 20AMP brushless controller successfully long term at 60 volts. I hate to have to swap out the controller, as it was custom wired to my hub motor. Also, what would be the best way to get another 12 volts in my system with the least amount of problems? I don't mind spending a few extra bucks to do it right, but do not want to go as far as purchasing a new 60 volt Lithium pack. I found a NIMH 12 E cell pack rated at 12 V 13 AH, 30 amps continuous output with a smart charger for under $200.00. I could also stick a B&B 12 V 15AH high rate LA battery in line for 1/4 that price, but with 5 more pounds weight. Any issues with adding either inline long term with the 48 Volt 15AH Ping LIFEpo4 pack?

 

[andys]

what does anyone think of this battery as a light weight add on for extra voltage? It sounds good except its about twice what i want to pay!

https://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1687

 

[knoxie]

Hi

Yes you can run the controller at 60V without any problems the caps in those are 100V rated and the fets are ok as well, I have been running my 48V 35A controller on and off with over 72V at times with no problems at all, I would be careful going higher than 66V on a stock controller with a Puma motor though, 60V should be fine though, make sure the phase wires are nice and short though, the lead will get quite warm otherwise, if you keep the amps down at 20A you should be ok.

Go with the NIMH, that works great I do that on the BMX, I run a 37V lipo and a 24V NIMH pack in series, it keeps things nice and safe and its a blast to ride that's a 20 inch wheel as well of course, I have had no issues with that config and I ride it all the time, at the moment I have to swap out the 24V pack from my main ride to put in the BMX so I am like you looking at another pack to put in the BMX permanently, there are a few options, one of the cheapest was on EBAY, there is a seller here in the UK doing 12V 4.6AH NIMH racing packs very cheap, 4 of those work out at just 100 pounds (still cant beat your dollar price here in the UK) so may go for that .

Good luck with the extra battery anyway, the controller should be fine, its the big box controller you have not the little one? stay away from lead NIMH is cheaper in the long run.

Knoxie

 

[Jozzer]

48v 20A controller is the little one is it not? I've seen these with 75v FETs, and the BMC's can push these pretty hard. I've seen 4710 fets fail at 60v before in these units on a BMC. It may survive if fitted with 4110 FETS..

Knoxie, yours was the bigger 35A version with twice the number of FETs..


Steve

 

[andys]

The controller is this one I am using. How can I tell what FET's it has?

http://www.bernsonev.com/crystalyte-speed-controller-roadrunner-xct4820-p-575.html?osCsid=f73e4468c6ca7ccd9f2719847ca99040


I have the power wires running very short from the hub to the controller & battery. I guess there is no way around having to separate the two batteries when charging. Any clever way to hook this up with a switch or two so you don't have to be unplugging wires all the time?

 

[andys]

also, I have been reading about the e-crazyman controllers, and he makes a 48 volt 28 amp version that has the better FEt's in it. i thought I read here somewhere where their might be issues with the BMC hubs and those controllers though. Anybody confirm this oneway or the other?

 

[Drunkskunk]

what does anyone think of this battery as a light weight add on for extra voltage? It sounds good except its about twice what i want to pay!

https://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1687

Skip it, unless you're familure with LiCo. Its explosive. That pack is too small on the amp hours, and to high on the voltage. what you need is a 11.1V 15AH. LiCo has less voltage sag than anything else, so you won't miss that 0.9 volts. from a 12V pack.


If you ant to mix chemistries, you need to make sure they have the same discharge rate. adding a 12Ah pack means it will go dead first, possably before you realize its dead, and that can cause a cell reversal. Since its NiMh, it will be depleted at around 10 amps. that means your 15AH LiFe pack has now become a 10AH pack in practicality, or in other words, its 1/3 wasted.

 

[Mark_A_W]

I run a 11.1v ~10Ah booster pack made from 4 11.4v 2600mAh RC lipos ($20 each shipped) in parallel, then this "pack" is in series with the main battery. They charge up to 12.4v.

You could get three 4500mAh lipos packs ($26 or so shipped) in parallel, and 3 E-sky chargers ($15 each) and do it for a touch over $100.

RC lipos are not dangerous unless you overcharge them, or pierce them with a metal object. Just charge them with a timer as a back up to E-sky chargers.

Try to get lipos with silicone charging leadings. Breaking the charging leads has been my biggest reliability issue.

 

[Drunkskunk]

where are you getting those Lipo packs so cheap?

 

[Mark_A_W]

Ebay.

My first set of lipos is 9 months old and charged every work day, and show no sign of degradation so far (but all the charging leads have failed and been replaced).

 

[Drunkskunk]

Nice. I'd been leary of eBay LiPo after my experiance with some cheaper brands of RC Lipo, but if you're having that kind of luck, I might try it. Got a seller you recomend?

 

[Mark_A_W]

If you draw 20+amps out of a 1500mAh Lipo they don't last long.


But if you draw 4 amps out of a 2400 or 4500mAh lipo they last just fine.


"Revolution shop" comes to mind....but they are all the same stuff, buy the cheapest.

 

[Jozzer]

Probably 4710 FETs in that controller.. Go easy, get it upgraded, or save up to get it fixed if you go ahead imo.