Chargers !

[alfazzr]

Please can anyone help out here? I am getting confused with chargers and have read all the back threads I can find. Talkng 36 volt. Assuming I can overcome connector compatability, can I use a 36v charge a Li-ion battery and a 36v LiFePO4 battery from the same charger ? (I have both types to charge).

Prices of chargers seem to vary wildly and, as usual, I want the cheapest alternative compatible with not destroying the battery or burning the house down !!

I can see prices from UK bike suppliers from £20 - £95 all for undisclosed types to suit their models of 36volt Li(X) batteries (where: X is a variable as it says in the physics papers).

Thanks
Alfazzr

 

[flecc]

LiFePO4 cells have lower voltages, nominal 3.2 and charge voltage 3.6.

"Li-ion" (lithium manganese etc) nominal cell voltage is 3.7, charge voltage 4.2.

If a LiFePO4 battery uses the same number of cells it needs a different charger, but some use a higher number cells to bring the voltage to rough parity. So it depends on your battery and it's internal management if fitted.

If unknown it's safest to have two suitable chargers, an over-high charging voltage can greatly shorten the life of an expensive battery.

 

[JuicyBike]

You also need to consider the rate of charge.

Larger amp hour batteries often are designed to cope with faster rate chargers (so you're not waiting forever for the charge to complete). Typically 1.8 amps for 10AH battery versus 3 amp rate for 16AH, allowing both batteries to complete their charge in around 4 hours.

Unless the manufacturer states otherwise, it would be unwise to expect the BMS of a lower capacity battery to cope with the available charge rate from a high capacity battery-charger.

 

[alfazzr]

LiFePO4 cells have lower voltages, nominal 3.2 and charge voltage 3.6.

"Li-ion" (lithium manganese etc) nominal cell voltage is 3.7, charge voltage 4.2.

If a LiFePO4 battery uses the same number of cells it needs a different charger, but some use a higher number cells to bring the voltage to rough parity. So it depends on your battery and it's internal management if fitted.

If unknown it's safest to have two suitable chargers, an over-high charging voltage can greatly shorten the life of an expensive battery.

Thanks,

Both batterys are nominally 36 volt, both habe internal BMS and are 9 or 10 ah.

 

[flecc]

Probably 11 series cells in the LiFePO4 then and 10 series cells in the Li-ion, giving 35.2 and 37 volts nominal respectively. Ideal charging voltages 39.6 and 42 volts respectively.

These are close enough for one charger to do both jobs, ideally an LiFePO4 one but either will work.

For two different connectors you could either have a branching lead with two connecting sockets or have an intermediate connector and a pair of flyleads, as in this photo of one I made showing one of the flyleads:

 

[alfazzr]

Thanks Flecc, where did you get hold of the connectors ?

I was wondering about having the two batteries on the bike, as one would suit the rear rack and one is a bottle type, with a kind of changeover mechanism - either manua,l so that when one is running too low you plug the other one in, or a chageover switch/relay buts thats probably too complicated to bother with.

Alfazzr

 

[Mussels]

They are (I think) XLR audio connectors, I've used them for the same thing in the past. Go into Maplins and ask them what they have that's suitable for your application.
I did find with those connectors that the cable attachment to the connector was a bit vulnerable.

 

[flecc]

Yes, as Mussels says, XLR connectors from Maplins on this page. The problem with a switch is the high currents it needs to handle means a suitable one can be bulky.

 

[jerrysimon]

Yes I thought where a BMS is present the main issue is charging current.

On my non BMS, 12s1p, A123, LiFeP04 pack I just use a stock 36v. 1.5A lead acid charger. I could probably use one with a higher charging current but on my small 2.3Ah batteries it only take an hour or so.

Input: AC 80-240V AC, 50/60Hz

Output: DC36V. Max 1.6A

Floating Change voltage 41.5+-0.2v

Equal Changing Voltage 44.5+-0.2v

Red and Green LED Light Indicators.

I am curious so for example what are the differences between these two ?

http://www.ebay.co.uk/itm/36V-2A-Electric-Bike-Battery-Charger-Lithium-etc-/140775191248?pt=UK_Bikes_GL&hash=item20c6daf2d0

http://www.ebay.co.uk/itm/36v-Battery-Charger-Electric-Bike-Razor-Scooter-36v-DC-1-6-amp-ebike-/261052247510?pt=UK_CartsParts_Vehicles_ATVQuad_Trike_Parts_Accessories_SM&hash=item3cc7ed2dd6

apart from the price!

Isn't there something about constant current, constant voltage charging ? I need to check the techy stuff as all I know is this works with my batteries lol

Regards

Jerry

 

[alfazzr]

Well this about does it for me, thanks for your help:

4 amps and does both types of battery & a good price too!
36V 4A Li Iron (LifePo4) / Li Polymer (LiMn2O4) Battery Charger

36V 4A LifePo4 Battery Charger

Ordered, sorted and happy ! Just got to wait for it to arrive!

 

[Scimitar]

Well this about does it for me, thanks for your help:

4 amps and does both types of battery & a good price too!
36V 4A Li Iron (LifePo4) / Li Polymer (LiMn2O4) Battery Charger

36V 4A LifePo4 Battery Charger

Ordered, sorted and happy ! Just got to wait for it to arrive!

I'd be interested in one for my own battery - the Bosch charger I have definitely doesn't like charging up more packs in parallel than it was designed for.
If the picture is accurate regarding what you're supplied with, I'd cut off the supplied 13A plug and put a decent one on - the fitted one is one of those dodgy Chinese ones with the pins too close to the edge and very often no fuse at all.

 

[alfazzr]

Or just use a new power lead - it looks like the standard one for a PC. Good warning though - I was not aware.

 

[Scimitar]

Or just use a new power lead - it looks like the standard one for a PC. Good warning though - I was not aware.

The damn things are everywhere - commonly fitted to China sourced goods. I've had a couple of them here.
BS 1363 Plugs and Sockets There's a useful illustration of them halfway down the front page.

 

[jerrysimon]

Nice looking charger and a lot better made than my

36v Battery Charger Electric Bike Razor Scooter 36v DC 1.6 amp ebike | eBay

Three times the price though.

I note comments about the plug and an interresting read of the links thanks. I think some of mine came with a two pin plug which I simply cut off and put on a three pin one.

I am now in two minds to get these which are a little bit better made than my original one and smaller if you need to take one with you. I tend to have a charger at work and home though.

36v Battery Charger Electric Bike Razor Scooter 36v DC 1.5 amp ebike | eBay

I guess at least the ones I linked to have correctly speced plugs though to be honest before reading that link I never realised that there were dodgy ones!

Regards

Jerry

 

[alfazzr]

Well it arrived today (before the battery) and looks good. I have compared the plug to that on my Dyson (definitely not Chinese) and cannot spot the difference on spacing or pin length, it even has a 5A fuse in the plug and a spare fuse for the chargeer.

Now I need to rig up a converter lead XLR to phono (coax?) for the other battery.