Idiot's guide to a self build battery

[Joeboy]

This is starting to sound like a del monte advert!

The man who sell diode he say shipped!

[Joeboy]

Sadly we need the EV at 10am today!

[Marcus]

Great answer from the nice man in China "can't".

Had a look about and this looks like it will work. I bought the built unit rather than the diy board.

https://www.aliexpress.com/item/1005008 ... ry_from%3A

Ideal isn't it?

Thanks Marcus. At 100A and with 4 chips to distribute heat it shouldn't trouble the 30A rating of the charger. at 0.2V loss max i'll be down to 50.2V for a cutoff but that's ok as that's about 80% soc going on Nowty's crib sheet.


Anecdote time. Batteries took quite a kicking yesterday and up Into the late evening. So much so that we only got to 94% soc by 05.30hrs this morning. Not a problem as its a glorious day but in Winter that would be the start of a downward trend if I couldn't get a slot.

Also noticed that when the Goodwe Hybrid inverter shows 100% soc in the Pylontechs it continues to charge for another 90 minutes as the Pylontechs feed the LF280's until balanced. This wee golf cart charger should take care of that....Or release magic smoke 1st time out.

Umm... reading the spec on that ideal diode it says max reverse voltage of 40V: that's fine as long as the charger is outputting 50v, but what happens if it is powered down? (I suspect >40v will kill the "ideal" part if the ideal diode and only work as a regular diode).

Sorry, when I suggested an ideal diode I was forgetting there's less choice for a 48v system (I'm still running 24v) - you might find it hard to find one.

[Joeboy]

Great answer from the nice man in China "can't".

Had a look about and this looks like it will work. I bought the built unit rather than the diy board.

https://www.aliexpress.com/item/1005008 ... ry_from%3A

Ideal isn't it?

Thanks Marcus. At 100A and with 4 chips to distribute heat it shouldn't trouble the 30A rating of the charger. at 0.2V loss max i'll be down to 50.2V for a cutoff but that's ok as that's about 80% soc going on Nowty's crib sheet.


Anecdote time. Batteries took quite a kicking yesterday and up Into the late evening. So much so that we only got to 94% soc by 05.30hrs this morning. Not a problem as its a glorious day but in Winter that would be the start of a downward trend if I couldn't get a slot.

Also noticed that when the Goodwe Hybrid inverter shows 100% soc in the Pylontechs it continues to charge for another 90 minutes as the Pylontechs feed the LF280's until balanced. This wee golf cart charger should take care of that....Or release magic smoke 1st time out.

Umm... reading the spec on that ideal diode it says max reverse voltage of 40V: that's fine as long as the charger is outputting 50v, but what happens if it is powered down? (I suspect >40v will kill the "ideal" part if the ideal diode and only work as a regular diode).

Sorry, when I suggested an ideal diode I was forgetting there's less choice for a 48v system (I'm still running 24v) - you might find it hard to find one.

Ah well,it's only a tenner. Any suggestions as to what might work? I've went as far as I can.

[Andy]

Eltek have protection built in

[Andy]

A relay based system? I’m not sure how long they would last opening and closing under load though.
https://electronics.stackexchange.com/q ... -cv-module

I wind the current down to zero before disconnecting my eltek and that’s even in the ac side.

[Joeboy]

An adjustable voltage sensitive no relay that can break under load would be nice. Would have to hook it up on battery side so it broke at say 50.1V. This may become more of a PITA than its worth.

Not yet though!

[nowty]

I do similar to take my Pylontechs out of DC circuit, but it is a bit of a PITA. In my case at the low cut off voltage there is only a handful of amps flowing.

[Joeboy]

I do similar to take my Pylontechs out of DC circuit, but it is a bit of a PITA. In my case at the low cut off voltage there is only a handful of amps flowing.

Wouldn't mid details on that set up Nowty. Looks like a logic switch and a relay/coil driving a mechanical make/break connection? Is the logic side 230Vac?

[Marcus]

An adjustable voltage sensitive no relay that can break under load would be nice. Would have to hook it up on battery side so it broke at say 50.1V. This may become more of a PITA than its worth.

Not yet though!

Yes a voltage sensing relay would be my next idea:

Possibly something like this:-

https://www.aliexpress.com/item/1005005849772632.html

I've not used on of these, but it looks like it would work. It will operate off 6-80v dc, and the contact is rated at 30A. Looks a bit fiddly to set up but hopefully you only have to do that once.

It can be set as active high or low, so if it's powered from the charger side, not the battery, and you use the NO contact, it cannot close the contact unless the charger is on. If it is then set to close the contact if volts (sensing battery side voltage) are <=50.4 then open at 50.5 it should work. In theory.

As the ideal diode is coming anyway, you could connect it between the relay and the battery as belt and braces in case the relay doesn't operate as planned whilst setting up. As the relay can only close when the charger is on, the ideal diode should be well within its 40v rating.