Replace old SLA

Hi all..
I found an old moped scooter (badged as 'Elite').. most likely made in China
Just looking to dump the old 36V SLA batter pack (ie. 3 x 12V 14AH) since they take an eternity to charge for not much ride time at the end of it.

To get a decent run time out of the bike I am considering getting a LiFePo4 36V 20AH like this one: http://www.bmsbattery.com/36v/501-36v-10ah-lithium-ion-electric-bicycle-battery-pack.html

will this work or do I need to get a matching 14AH pack ?

I have read on here the BMS are good value, any thoughts ?

Well, the one you link to says "10ah" in the link, rather than 20Ah, so not sure. (can't open link from here to check actual page).

All the Ah or Amp-Hour rating means is how much capacity the pack has, total, and therefore how much range you could theoretically get out of it.

It's separate from the A or Amp rating of hte pack.


The one thing you really wanna look for besides matching voltage is that the max and sustained current the pack can put out ("c" rating) is at least as high as the max your vehicle draws from the pack it has now, (if your controller has an Amp or A rating, you could use that as the current max the pack must be able to put out) or else a couple problems could happen , when you try to startup from a stop or acclerate up a hill, or in other high-load situations:

1: the pack could just shut off, cutting power completely

2: the vehcile could just react sluggishly, as pack voltage drops a lot during high current draw.


A third possiblity is that the controller on the vehicle could shut off due to Low Voltage Cutoff (LVC) trying to protect the pack, if the voltage sags low enough during high loads.


A fourth is that if the pack has no BMS (or a poor one that doesn't prevent over-current-draw) it could be damaged over time by high load situations.

Thanks for the info ..
I guess I just need to locate the controller .. Would it most likely be labelled with its ratings?

And that link actually points to a 20ah battery .. Website must have labelled wrongly

bcmir said:

I guess I just need to locate the controller .. Would it most likely be labelled with its ratings?

Click to expand...

Probably not, but it's possible.

Follow the wires from the motor to find the controller.

Found what seems to be the controller, since all the wires go into it.
It is shaped like a large heatsink and is completely sealed.. I even after removing screws holding it together, so I would have to use a hammer & flat screwdriver to look inside.

No labels indicating anything about "C" ratings, just a stamp in the metal which seems to indicate the year of production etc..

Is there any way of taking an educated guess as to what sort of current this controller is drawing from the battery pack, and ordering a new LiFePo4 to replace?

not without a picture or any useful information to guess.

Hope these pics help??

yes, that controller is a tiny 200-250W controller and inside all the parts are embedded in a plastic potting compound so there is nothing you can do inside. mine is an Ananda and looks very similar but not identical but i suspect that is the source.

i doubt if you can get that controller to handle more than the 36V so it is gonna require you start looking for a larger controller to handle more power and voltage.

do not buy a BMS from BMS battery. you can get a better one from bestechpower. there are other and better sources for batteries too.

Yes, that controller is likely @15 amps, and the link to the battery would work.

There are many battery variations that u could get, but the one u linked to would be adequate, and be plug & play

Ian

Many thanks for the input guys
I will most likely get a battery which 'plugs and plays', rather than go with upgrading controller etc..
The power output as it stands is just about right for my kids ... just enough to make it fun

One more thing, does anyone know where to get these connectors for the charging input & battery connection (see pics)?

No idea what either of those plugs are. The first one looks like a 1/4 inch stereo jack, and the second one looks like a IEC 60320-C13 jack, but I'm sure neither of those is quite correct. The C13 jack has a vertical ground pin; yours is horizontal.

You're probably going to want to get a different charger when you get a new battery anyway. Your SLA chager is probably a poor choice for charging lithium batteries. Pick whatever connector you want. As long as you're working with less than 15A charging current, a C13 plug is a fine choice. Anderson plugs are another common choice.