Question on converting charger to onboard

bronsonj

I finally installed a 120v receptacle in the body of the cart, mounted the charger underseat and now can just plug in and charge. The issue is that it has a small continuous drain on the pack when not connected to 120v.

I'm not an electrical engineer so I don't know the difference between various types of diodes. But, I was going to just buy a 100V schottky diode and mount it in the charger wire.

Are the schottky diodes are the right choice for this? The charger will output V when not connected to a battery, so I know it isn't waiting for a Voltage to sense on the wire. Looking for opinions about what's wrong with this idea or if there is a better (and still simple) solution.

The charger is a small 5 amp charger for my lithium pack.

BGW

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JohnnieB

A silicon diode will drop 0.6V to 0.7V, which means the charging voltage at the batteries will be that much lower and I'm not sure if that would be acceptable.

A 120VAC relay whose contacts make/break the chargers connection to the battery pack would be best.

I'd use a SPST relay with N.O. contacts and a 120VAC coil. Wire the coil to at AC that feeds the charger, so when the charger is plugged in, the N.O. contacts c;lose and connects the charger to the battery. (Could also use a DPST relay and break both wires between charger and battery pack)

bronsonj

Thanks for the insight JohnnieB! I never thought about a 120v relay. I like that it completely disconnects the charger from the battery pack. I'll look for a suitable relay.

JohnnieB

Be sure to get a relay with an AC coil. A relay with a 120VDC coil becomes a buzzer when 120VAC is applied. (Don't ask how I know. )

Sergio

If You are using a BMS, how does it currently disable the charger during a cell HV condition?

If your charger is one of those Chinese silver brick looking box, the relay contacts will not last long due to the charger capacitors.

The schottky diodes normally have a much lower voltage drop, but since you need a higher reverse voltage breakdown version, the leakage current of two in parallel (each diode needs to be at least 65% of the total current) may be about the same as the battery leakage that is keeping the charger capacitors as well as the LED on the charger ON.

bronsonj

My charger is a Meanwell 57.6v charger model ENC-360-48. It's not the oft used silver brick. My charger passes fewer amps than the silver bricks do, but it does stop at the voltage I want it to. https://www.jameco.com/z/ENC-360-48-...s_2255541.html

Thanks for the info on the schottky, good to know before I attempt it.

The 120v relay was delivered, it is a DPDT so I can parallel the outputs to reduce the load on the contacts. The Meanwell charger being only 360 watts doesn't have the audible arc when plugging in so I am thinking it is smaller caps and therefore less of an issue with the contacts. I could get fancy with an HD solenoid, but I really don't think it'll be a problem with a 5 to 6 amp charger.

Yeah, the charger is slow but I have it onboard for opportunity (and emergency) charges.

bronsonj

Circling back,

I installed this 4PDT relay. So when I plug in the relay it then powers the charger as well as closes a second set of contacts that connects the charger to the pack. When I unplug the relay it disconnects the charger from the pack.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Works like a dream.

It has four separate circuits that have both NC and NO tabs. So I could connect some other stuff, like an onboard 12v charger. This would let me plug in a single 120v extension cord and the cart would automatically charge both the traction pack and the 12v accessory pack.