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2020 159 HR
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Discussion Starter · #1 ·
Hi All,
Wondering if anybody might be able to give me a reality check on this. I installed 3 Renogy 100Ah LiFePO4 in parallel. I can charge just fine from a Victron AC-DC charger. But the DMT-1250 (which so far is only hooked up to the van battery, no solar yet) doesn't charge the house battery.

  • The DMT-1250 is set to Lithium mode.
  • Renogy's battery monitor shows 70% SOC, and 13.3V for the house battery bank.
  • DMT-1250 shows that with the engine running, there's plenty of voltage from the van battery. It also shows CH3 (the van battery input source) available, but not charging (CH3 is flashing in the display, and that's apparently what that means according to the manual).
  • DMT-1250 also shows the house battery bank at 13.3V (doesn't show SOC).
I think what might be going on is that the DMT-1250 thinks of 13.3V on the house battery as fully charged (there's some mention in the manual section that describes the bulk/absorption/float cycle, and it says: "The battery will start the full recharge cycle again when the battery terminal voltage drops to 13.3Vdc".

Has anyone encountered this? Anyone set up a DMT-1250 with Renogy LiFePO4 batteries successfully who might we willing to share their settings that work for them? I'm pretty stoked that things seem to be working so far - this is the last piece on this install that's giving me trouble.

Thanks!
 

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2018 3500 EXT Camper Conversion in CT (TX for now due to Covid)
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I specifically have my solar charger set to not attempt to charge the batteries unless they fall below 13.2 right now because my batteries are not really being used. I image your charger is waiting for the battery to fall below some trigger voltage before charging it back up.

LiFePO4 batteries do not like to be stored charged and will have a longer life if they aren't topped off all the time (how much remains to be seen as there just isn't all that much data yet in real world use).

Here is what I found about the DMT 1250 when set to lithium mode: It will not attempt to re-enter bulk charging until the battery is below 13.3 volts for 3 minutes. This is a potential cause of your observed behavior. Discharge the batteries a bit and see if it will then charge.
 

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2020 159 HR
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Discussion Starter · #4 ·
Thanks all for the feedback, that's all really good helpful stuff in trying to wrap my arms around this. So the plot thickens, but not in any way that's getting me where I'd like to be...

Renogy got back to me after I logged a ticket to tell me that I should consider the battery monitoring screen (which plugs into the battery bank via an ethernet cable and gets its reading from the BMS, rather than doing all the measuring itself like a regular battery monitor would) to be wrong on SOC. They say to fully charge the batteries (which I can do with my AC-DC charger) until full, then reset the monitoring screen. To them, 13.3V is indeed pretty darn close to fully charged - so if the battery, the monitoring screen, the Kisae DC-DC charger, and my trusty multimeter all agree that the battery bank is sitting at 13.3V, then yep, that's what it is, and SOC should read somewhere around 96%, and then that makes the Kisae DC-DC charger not wanting to dump current into the house battery the correct decision.

BUT... - tonight I figured that before charging fully, I'd test what happens if I deplete the battery a bit. So I turned on my inverter, used it to run a small (150W) radiant heater (to test how much that would draw, since we're counting on that to take the chill off), a couple LED worklights, and ran some powertools while working on other things. After a few hours of that, I got the battery down to 13.0V. So then I cranked the engine, turned on the DC-DC charger, and expected it to start charging (since it's well under the 13.3V the manual says is where it would NOT get back to charging). And nope, nothing - still seeing the same behavior from the charger:

  • CH1, the house battery, shows at 13.0V (which agrees with the multimeter at the bussbars and with the battery monitoring screen)
  • CH2, solar, shows as 0V (which makes sense, since there's nothing hooked up there)
  • CH3, van battery/alternator, shows at 14.4V - which agrees to the multimeter reading at the van battery terminals
  • CH3 then goes to "blinking" (which, according to the manual, means it's recognized, but not used to charge) - and then the charger turns itself off
  • And throughout all that, the battery monitoring screen records no incoming current (which it knows how to do - tested that with the AC-DC charger earlier).
I ran the engine for over 15 minutes to see if eventually the charger would wake up and decide it was time to go to work - nope, nothing. I tried to contact Kisae via the email they show in the manual, but no response yet.

Tomorrow I'll try to deplete the house batteries a whole bunch more to see if that gets the charger interested in jumping in. If anybody has any ideas based on what I've described above, I sure would be grateful for anything that might get me on the road to troubleshooting this a bit more.
 

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What size wire are you running from the starter battery to the DMT? And how long is it? It's possible you're getting voltage drop when the charger kicks on and it's shutting off as it thinks the starter battery is under voltage. Another step you can try is to lower the charger current from 50 amps down to something like 10 or 20 to bypass the voltage drop (if that's what's causing it)? If that works maybe try to up the wire size.
 

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2020 159 HR
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Discussion Starter · #7 ·
The DMT can be used with a trigger input, if you are not using it do you have to set it up differently? Are the settings correct?
The manual says that you don't need the "trigger" (control" input unless you have a smart alternator. I'm starting to get a bit of response from Kisae tech support, but nothing concrete so far, just a bit of back and forth about what I'm seeing and me sending the friendly tech there a video to document the behavior in hope that gives them something to go on.
 

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Discussion Starter · #8 ·
What size wire are you running from the starter battery to the DMT? And how long is it? It's possible you're getting voltage drop when the charger kicks on and it's shutting off as it thinks the starter battery is under voltage. Another step you can try is to lower the charger current from 50 amps down to something like 10 or 20 to bypass the voltage drop (if that's what's causing it)? If that works maybe try to up the wire size.
I was wondering that, too - but the battery and charger are right behind the driver's seat, and I'm running AWG 4. I checked, and I'm getting the same (hovering between 14.4 and 14.6) when taking the multimeter either directly to the starter battery or measuring voltage at the inputs on the charger, so I don't think there's any appreciable voltage drop. 14.4 should be plenty for the DMT-1250 to recognize that there's a nice fat input - and according to the manual, what it displays (the voltage for CH3 on startup, and then CH3 is flashing, meaning it's recognized as present but not used to charge) seems to suggest the charger does recognize that, just doesn't charge.

So I've now got a situations where everything the manual tells me - it should charge if both of these are true:
  • House battery is under 13.3V - which mine now is, I've got it down to 13.0
  • And there's a recognized input coming from the van battery (and/or solar, but I don't have any solar hooked up yet) that's above its start-up threshold - which it is (mine is delivering 14.4 and up, vs. the 13.2V start-up cutoff).

One thing I haven't tried yet is to run a control wire from the control port on the charger to an ignition-on source in the van. Supposedly, that lowers the threshold from 13.2V down to 12.3V and is what you'd use with a "smart" alternator (which ours, of course, isn't). One of the reasons I went with the Kisae is that it allowed me operating it without an ignition wire - one fewer connection, thus one fewer possible trouble spot. My backup plan (since I'm planning on leaving for a trip in less than two weeks) is to put in a Renogy 40A DC-DC charger that I've got sitting here new in box. That one, however, does require an ignition feed to control it, so I guess I might as well run the cable now to see if it makes the Kisae behave.
 

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Discussion Starter · #9 ·
Well, riddle solved. Had a very productive exchange of emails with a tech from Kisae who walked me through a bunch of troubleshooting, then determined that the particular firmware version of my particular unit actually DOES require the ignition-on lead, despite what the spec sheet and manual say. In this version, ignition on enables the whole charging routine as described in the manual, along with all the thresholds you might set in user configuration. Ignition off will lead to the unit not charging off the van battery no matter what (and turns the charging off about a couple seconds later, as opposed to the minute or two the charger might otherwise take when it detects van voltage dropping on engine shutoff - something that might come in handy if trying to get a bit of charging in on short intermittent trips).

Anyway - I'd chosen the Kisae over the Renogy because (a) it didn't require an ignition-on lead (wanted to keep things simple, fewer connections to go wrong and all that), and (b) it's not limited to 25A per input if you're running both solar and alternator. Wiring the ignition on wasn't hard, and given all the other connections I had to crimp and set up, I guess this is minor and not all that prone to failure.

Kudos to Kisae, they were very helpful, methodical, and responsive.

Heads-up to anyone setting up one of these - seems like the the firmware change requiring the ignition-on control is a new thing. Don't know if that's a decision on their part to change the feature set, or whether it's the result of having sourced different components (that sort of thing happens all the time in other tech products, like consumer grade networking gear and such - you think you have a set of specs, but stuff is a lot more fluid that it seems).

And lastly - there's a lot of discussion around these parts about where to tap an ignition-on source for this kind of thing. The general recommendation tends to be the cigarette lighter (geez, I just dated myself - I mean the 12V power port, since none of those have had a cigarette lighter in them from the factory for a very long time now - I used to like having those to burn/melt the ends of bits of rope for sailing and windsurfing gear). My van has the upfitter connector, though, since it came with the RV prep package. Meaning that pin 13 in that connector is an ignition-on fused at 5A. Perfect, then, for this sort of thing, and connected to that handy Aux 2 switch in the dash. Plus the routing from the passenger side B pillar under the flooring behind the seats to behind the driver's seat where I've got my battery setup inside a toolchest-based kitchen cabinet was really easy.

Problem with the stupid connector, of course, is that if you want to get it done NOW, as opposed to waiting for a week or two for the specific Tyco Products part to get ot you from Amazon, you're sort of SOL, because nobody stocks those (my local RAM dealer laughed at me when I called about that part - said they can't even order it from Ram; my local Napa and Autozone didn't have it in their distribution channel, so they both offered to find it for me online so I could order it myself). So I went total hack and simply cut the lead going to that pin, connected it with one of those crimp/solder butt connectors, and then tucked it all nicely into the rather generous recess next to the connector.

I think having the Aux 2 switch available as a quick and convenient way to turn off the DC-DC charger will be neat for short trips, or when I want to purposely run the batteries down a bit, etc. Not having to go back to the battery box to turn it off and simply being able to control that from the driver's seat is nice.
 

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I know this thread is old but I have what appears to be the same problem. I am hoping G-42 checks in occasionally and could possibly shoot me the email exchange he had with Kisae tech support. I have not been so lucky as to have them respond to my questions. The unit displays U2.8 and r2.7 as the software version. Is there a voltage and amperage spec for the control input? thanks
 

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2014, 138WB, High Roof, Gas, SW MT
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I know this thread is old but I have what appears to be the same problem. I am hoping G-42 checks in occasionally and could possibly shoot me the email exchange he had with Kisae tech support. I have not been so lucky as to have them respond to my questions. The unit displays U2.8 and r2.7 as the software version. Is there a voltage and amperage spec for the control input? thanks
I also have the DMT1250 and have had sent in a couple questions to Kisae support and gotten long, detailed and well thought out responses.

Maybe give them a little more time, and then if you don't hear from them resubmit the request?

This is the return email that was on the response I got from them on the last question:
[email protected]


Gary

Gary
 

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Discussion Starter · #13 ·
Update on my setup 1 1/2 years later - the charger is still working fine, the ignition-on lead I connected to that's switched with the Aux 2 circuit in the dash has indeed worked out great, and frankly the whole thing worked out well.
 
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