Installing a KISAE DMT-1250 DC to DC charger - Page 2

Kibo · 06-22-2019, 01:06 AM

Great info here. I'm using a DMT-1230 with my Lithium setup (should have sprung for the 50A, but at the time wanted to save the extra $100). Rather than installing a high-amp relay to work around the issue with the Kisae pulling current after the ignition is shut off, you can wire a low-power relay in series with the manual switch that's under the wiring cover. All you have to do is pull the lid and pop the switch out to gain access to these wires. In my case the BMS is controlling the Kisae through an optioisolated relay, but you could control it based on ignition position, etc. if you'd prefer. I also have my charge bus kill switch wired in series using the terminals intended for alternator field.

Scalf77 · 06-22-2019, 05:58 AM

Good info on the switch, it would certainly be the easy way to eliminate that problem. The switch is worthless in the position it is in. Glad to see it can be easily integrated into the BMS system.

-greg

twotimer · 06-27-2019, 10:05 AM

Excellent information! A little over my head, but it gives me something to strive for.

Scalf77 · 07-06-2019, 09:26 AM

Tapping into the switch had some merits, the problem that was a show stopper was that this would also be disconnected when I wanted Solar. And while I didn't use the 120 amp relay in my install, I have integrated it into some other installs. The diagram below shows the KISAE DMT1250 and the KISAE ABSO DC1260 shower power charger. The DC1250 has the capability of charging up to three batteries. I tapped the second battery output to the starting battery side of the relay. When the van is off, the relay is open, this takes care of both the slow to disconnect issue I saw on DMT1250, and allows me to use second battery output to also top off the starter.

-greg

rob_gendreau · 07-17-2019, 07:36 PM

Would using the ignition connection from the Kisae remedy the 3 minute drain? Thatyan issue for me as I do a lot of short drives and those 3 minutes could add up to considerable punishment of the van battery.

Kibo · 07-17-2019, 08:37 PM

Unfortunately no. A positive voltage ( >10.5V ) on the ignition terminal is used to lower the Low Start-Up Voltage and Low Under Voltage Recovery Voltage. In layman's terms, with the ignition terminal high the disconnect/reconnect voltage thresholds are lower than "normal" voltages.

However, wiring a relay in place of (or in series with) the manual on/off switch as I described and controlling it with a Run ignition signal could achieve what you desire--when the ignition is turned off and the relay opens, the charger will shut off immediately instead of waiting 3min.

rob_gendreau · 07-17-2019, 09:12 PM

Ah, makes sense. Dumb question though: would the okd school SMB isolator serve a similar purpose? With the Kisae downstream? I would think not, but not sure.

Kibo · 07-18-2019, 12:08 AM

I'm not familiar enough with how SMBs are wired to be qualified to answer that question. However, if the isolator is a dual-sensing charging relay type, I don't think it will work with the Kisae downstream since the house battery voltage is never "seen" at the SLI/alternator input to the Kisae.

Scalf77 · 07-18-2019, 05:10 PM

The old school isolator “diode based” may work because the alternator would not be charging and the diodes would block from the start battery.

I don’t think I would recommend it, as it would put additional stress on system.

-greg

rob_gendreau · 07-19-2019, 10:20 AM

Quote:

Originally Posted by Scalf77

The old school isolator “diode based” may work because the alternator would not be charging and the diodes would block from the start battery.

I don’t think I would recommend it, as it would put additional stress on system.

-greg

Yeah, I figured it was a long shot. I could use the wiring and same space for the relay that was suggested.