Forklift Battery Chargers failures due to brownouts?
Forklift Battery Chargers failures due to brownouts?
(OP)
I am running into a problem with a big warehouse facility where they have about 70 big battery chargers for forklifts. They are being fed from 2-3P-600A circuit breakers, some of those chargers get damaged where they have to replace the electronic board inside due to often electric brownouts and surges. Upgrading to better improved chargers could solve the problem but it is costly since the charger run about $3800, installing a large UPS unit is also costly for 2-3P-600A.
They are trying to solve the problem without having to spend quarter a million. Any suggestions?
They are trying to solve the problem without having to spend quarter a million. Any suggestions?






RE: Forklift Battery Chargers failures due to brownouts?
Another question would be why there are brownouts. That's usually something that needs to be fixed anyway. That can cause havoc with refrigeration equipment.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Forklift Battery Chargers failures due to brownouts?
Is the diagnosis "due to often electric brownouts and surges", proven by any physical evidence, or just a guess based on the fact the you have have experienced both brownouts and charger failures?
RE: Forklift Battery Chargers failures due to brownouts?
Can you put timers on the chargers to bring them on line (A) after the grid peak begins to subside, and (B) sequentially?
The forklift timer that I use at a warehouse that I own usually has the job done in just a few hours. It doesn't take the entire 15 hour period between the end of the day shift and the start of the next day so any time in between as long as enough time is allowed for a complete charge would work.
rmw
RE: Forklift Battery Chargers failures due to brownouts?
To precharge the DC-link capacitors when starting up the equipment there has to some kind of current limiting. This can be done by various means:
- NTC-resitor
- precharge resistor and relay
- precharge resistor and electronic switch
- half-controlled rectifier using thyristors
To operate properly in brown-out condition the following functions must be implemented:
- when the control detects brown out, further discharging of the DC-lin should be avoided, e.g. by disbaling pulses of the inverter stage
- When voltage comes back again, the precharge circuit has to be activated again
If the chargers are quite old and you do not have warranty on it (or you still have warranty, but dealing with brown-out is not covered in the applicable standard or specification), I'd recommend to hire someone to design and implement an upgrade for the missing functions (provided you have access at least to the schematics)
RE: Forklift Battery Chargers failures due to brownouts?
How frequent are the brown-outs?
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Forklift Battery Chargers failures due to brownouts?
As others have mentioned, it may be an idea to look at the cause of the brownout, as if it is the current draw of the chargers that is causing the problem you'll probably need some way to stagger the timing of the chargers coming on-line.
RE: Forklift Battery Chargers failures due to brownouts?
Some simple surge protection for the control boards might suffice for overvoltage events. If its undervoltage causing the damage, as others have suggested, perhaps adding undervoltage protection and/or staggering the charger start times could solve the problems.
If you add such protection, it would be wise to add some ON delay time in addition to hysteresis to avoid 'doorbelling' the chargers. With 70 units and the above protection functions, it might be worthwhile investigating a PLC solution to control everything. That'll give you some room to add additional protection, scheduling control and status monitoring.
RE: Forklift Battery Chargers failures due to brownouts?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Forklift Battery Chargers failures due to brownouts?
RE: Forklift Battery Chargers failures due to brownouts?
RE: Forklift Battery Chargers failures due to brownouts?
Keith Cress
kcress - http://www.flaminsystems.com