Pre-charge Circuit required for 36V battery?

[majornelson]

I have a MAC motor, 48V triangle pack battery and 9 fet 4110, 36-72V Infineon Controller from em3ev.com. Everything works great. I also have a 36V water bottle style battery (from Amped Bikes) that I'd like to use with the setup from time to time (much easier to take off the bike at work than the triangle frame pack). The Infineon controller is setup with a pre-charge circuit but the 36V water bottle battery has only positive and negative wires.

Am I risking anything by not using the pre-charge wire when I hook up the 36V battery? I'm assuming that this is built in to the 48V triangle pack's BMS and can't be added to the 36V battery...

Appreciate the help and feedback...

 

[neptronix]

No need.

Been running 36v for 3 years with no precharge. The spark is really minimal. It would take forever to really pit most connectors enough that the contacts are weakened.

48v? yeah, maybe you need precharge.

 

[davec]

for 36V yes you can get by without one- you will get spark and charcoal your connectors though
however a 36v fully charged amounts closely to 43v which does push a small spark which eventually eats away contacts/introduces resistance issues - also hard on the caps - to save your contacts/caps i would go for it..resistors are cheap..
for a 48v i would definately have a pre charge- the spark can be heavy

Edit: you will destroy your contacts: just use a 10W 150Ohm resistor and you won't have to worry about anything

 

[Ypedal]

my trike with 18fet monster at 100v eats connectors for lunch, you'd swear the thing is shorting out if you forget to pre-charge.... but the smaller units at lower voltages ... with andersons .. no problem imo. plug and play.

 

[Ykick]

I run 62v for years - 100's if not 1000's connections with no troubles. That's almost the limit though. 36-40v not much of a concern IMO.

 

[Ypedal]

it's not just the voltage, it's the amount and type of capacitors in the controller, the " capacitance " i think it's called...

my 12 fet m 100v crystalyte controller remains charged for weeks if i use the on/off button and has minimal spark, no pre-charge ..

my 18fet lyen on the other hand...

my 48v castle HV controller with Fechter throttle box (* filled with a big row of caps ) needs a pre-charge but it's a puny little 2" box controller.

edit : the low resistance of high C rate lipo also plays a factor, low power 2C cells in the amped bottle battery, plus BMS, is not going to make much of a zap.

 

[majornelson]

Thanks all! Looks like I won't blow anything up if I don't use one... :wink:

I may try to put a pre-charge circuit together. From other posts, it looks like a 10 watt 100 ohm resistor would do the trick. Is this correct?

Thx!

 

[dogman dan]

I've run 72v for years without a pre charge resistor. But using andersons helps. The tips are of course all charred, but the blade past the tip where the working contact is made stays clean.

Really cheap trailer bullet contacts eroded in a short time, at 36v. Good 4mm bullets should last a long time too. The main thing is using a decent connector.

 

[alsmith]

It depends on your setup.

Mine is just 36V but I get a big spark when connecting. It is to a 18 FET Lyen, and 15Ah battery with BMS capable of 50A continuous 100A peak. When I had 30A powerpoles on it destroyed the contacts quite quickly so I upgraded to the 75A connector in the dual connector that derates them to 50A. They've fared better but I still get a big spark. One time I couldn't join the connectors, when I looked at the connector it had deep pitting and a raised area that was stopping it functioning- it had to be replaced.

I really need to get a pre-charge circuit for mine.

 

[Ykick]

Oil and grease on connectors tends to make a louder and more forceful spark imo.

 

[Tommy L]

Oil and grease on connectors tends to make a louder and more forceful spark imo.

I "Jumped" up in the air and rotate 180 degrees while putting the connectors together. This doesn't
appear to really do anything as I precharge :lol:

Tommy L sends.....