Kewet 3 - Electric heater

[SorenHJ]

Dear all,
The electric heater in my Kewet El-jet 3 does not work anymore. Does any one of you have a replacement heater I can buy or know of a suitable replacement heater?
Best,
Søren

 

[SorenHJ]

Update/correction: I measured 5.5 Ohm on both the electric wires in the heater (photo), so the heater seem to be OK. The Bosch blower works fine. However, at least one of the three relays/contactors (photo) behind the radio seem to be fried (photos). I guess the contactors could be the problem. I looked up the contactor and it seems to be made for AC, and I believe the contactor brakes the DC battery pack voltage (~48V). I guess that since it brakes DC and not AC could be the reason why it does not work? If you know what type of contactor I should purchase as replacement I would love to hear from you. I will also search for the right relay and write an update when I have installed new relays/contactors. Best, Søren

 

[matzetronics]

I looked up the contactor and it seems to be made for AC, and I believe the contactor brakes the DC battery pack voltage (~48V)

Yes, the rating printed on it is for AC 250V. DC current must be much lower - mostly only a third of the AC rating. This normally is not a big problem as the heater is only 400/800W and a current which the relays can just switch. Kewet exceeded the rating without doubt. Replacing or repairing the relay will not be hard.

If you change to 72V though, this is a big problem as the heater itself is on overcurrent and so are the relays (please don't call them contactors as nobody else will know what you mean). At 72V, arcing can already happen.

 

[SorenHJ]

Hi Matzetronics,

to avoid having 72V on the relays, I do not change the 48V in the control circuit. The additional 24V is only is only inserted in the power circuit with the Curtis controller. In order to ensure balancing the batteries, I have a separate 48V charger for the 48V circuit and a separate 24V charger for the 24V batteries. It worked well for the PB batteries and since I have BMS in the Humsienk 200Ah 12V batteries, I guess it will also work when I have a 48V LFP charger + a 24V LFP charger. However, this remains to be seen.

With respect to the heater, I think the relays I need are the Power relay 62.32-4800, described on page 6 in the attached brochure with the following relevant specification:
Breaking capacity DC1: 30/125/220 V A: 16/12/6

The relays can be found on RS:

https://dk.rs-online.com/web/p/effektrelaeer/2482536?gb=a

but only in packages of 10. I guess I will buy the package with 10 and see if anyone wants to purchase the remaining relays on Ebay.

actually, I can see they are much cheaper on Ebay:

https://pay.ebay.de/rgxo?action=view&sessionid=1871091768

Best,
Søren