Two high voltage batteries and one charger

[Diego Medina]

Hi,

My wife just got an electric vespa like motorcycle. It came with two 72V batteries but you can only connect one at the time.

So about half way on trips, she needs to unplug one and plug the other.

The batteries have an anderson battery connector 50 amps.

I've been trying to find something like a switch that is rated for 50A 72v DC that she can just flip to pick one battery or the other.

Does anyone here know of such a thing?

Thank you!

Diego

[mountain...@gmail.com]

Is it possible to make a parallel harness so you can exhaust both batteries as one "pack?"

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[Diego Medina]

That was one of the ideas I had originally but she actually likes how when one battery starts showing low charge, it's time to turn around and switch batteries.

I found this one but it only goes to 32v 32 amps

https://www.amazon.com/Blue-Sea-Systems-Selector-Battery/dp/B000FOPE1G/ref=asc_df_B000FOPE1G/

Thanks!

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[Shane Trent]

Hello,

I expect the Blue Sea switch would work. Switch current ratings are based on how much current they can interrupt under load, and how many times for an expected lifecycle. 

Since the Blue Sea switch can interrupt 32 amps, if you switch between battery banks with no load, the switch should handle the 50 amp load easily. 

Going off the shelf is a good idea to help avoid the increased meltdown/fire risk of a diy solution. Just make sure you is the locking washers/nuts on the switch terminals to ensure the connections do not get loose and overheat. 

And Blue Seas Systems makes great stuff!

Shane

Sent from my iPhone

On Sep 3, 2022, at 7:19 AM, Diego Medina <fmpw...@gmail.com> wrote:



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[Baron]

Blue sea does make 50amp switches as well... A-off-B setup or a A/B switch.

 Some are large so may be hard to find a good spot to attach them, they should get some kinda bracket to mount to so you don't move the wires a lot. There's other similar switches that are smaller. I'll look for a link..

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[Diego Medina]

Shane, thank you for the information, that covers the current, what about the voltage? Is it ok to have a 72 v battery using a 32 volt switch?

@Baron:. It would be great if you could find that link!

Thanks!

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[Shane Trent]

Ah; I missed the voltage rating difference. I do not recommend using a 72V battery with a 32V rated switch! 

Switch, relay, and circuit breaker voltage ratings comes from component spacing and the ability to quench an arc when interrupting load current. DC is unforgiving about arcing because it lacks the polarity reversal of AC that makes quenching an AC arc easier. This is why you may see devices with higher current ratings for 120V AC than for a much lower DC voltage. 

So using a DC voltage higher than the switch voltage could cause a failure were the arc is not quenched but maintained, with load current continuing when the switch is turned off, possibly leading to a fire. 

Good luck your search for a switch!

On Sep 3, 2022, at 10:59 PM, Diego Medina <fmpw...@gmail.com> wrote:



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