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Author Topic: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?  (Read 130 times)

N4SRN

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Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« on: July 05, 2020, 04:50:00 AM »

I was running my Kenwood TM-D710G on high power APRS to see how long it will run on a 12V 35Ah battery. It got down to a point where the radio kept cycling on and off. Is there a specification I might reference on a limit voltage for this radio? And a low-voltage cut off switch I might install to simply cut voltage rather than see this power on/off cycling?

Bret/N4SRN
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Bret/N4SRN
Bedford, NH  USA

W9IQ

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #1 on: July 05, 2020, 05:44:33 AM »

Consult your manual for the specified minimum voltage and remember that cords, fuses, etc. will add resistance, therefore requiring a higher battery terminal voltage. You will also find the internal resistance of the battery will cause the battery terminal voltage to plunge when the radio draws more current in transmit mode.

Here is an inexpensive device that can cutoff the load at a user selectable voltage and restore power when the battery is charged: https://www.amazon.com/Charging-Controller-Protection-Undervoltage-Automatic/dp/B07B49T4DQ.



- Glenn W9IQ
« Last Edit: July 05, 2020, 05:48:15 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N4SRN

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #2 on: July 05, 2020, 07:04:10 AM »

That’s a nice option, thanks. I’ll give it a try.

The battery is a Jasco RB12350 AGM. I think I discharged it too low as the little QuickSilver Radio Hammo-Can Go-box charger left on overnight wouldn’t bring it back. I put on an Optima Digital 1200 Charger that’s been good at recovering deeply discharged batteries - hopefully I can save it.
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Bret/N4SRN
Bedford, NH  USA

W9IQ

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #3 on: July 05, 2020, 07:24:25 AM »

Yes, some of the newer chargers are too smart for their own good. I keep one old fashion Sears transformer/rectifier version just for the reason you mention. It is only a 2 amp unit but it charges the battery to a level that the "smart" charger is then happy with to continue the charge.

You could also look into a small battery booster circuit. This would allow you to use more of the energy stored in your battery while cutting off the load at a specific battery voltage. Some have an integral charge manager as well. Certainly much more expensive though, than the cut-off module I referenced.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

K5LXP

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #4 on: July 05, 2020, 10:29:22 AM »

Every connector, fuseholder, termination and splice is contributing to voltage drop.  They may not seem significant individually but especially in a battery application every tenth of a volt counts.  Anything you can do to improve the DC path between the battery and transceiver will translate to additional run time.

The charger in a hammo-can is probably small, maybe an amp?  It's probably intended more to float the battery than cyclic charging and use.  To recover a 32Ah battery with a small charger like this will take several days.  If charge recovery time is important then a multistage charger made for sealed batteries is on your shopping list.

Mark K5LXP
Albuquerque, NM
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N8GD

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #5 on: July 05, 2020, 11:08:32 AM »

This does not surprise me at all.  I have a Kenwood TM-D710A (the predecessor to the 710G), and it has been picky about low voltage.  By low voltage, I mean anything below 12.5 VDC.  The vehicle it is mounted in a 2015 Honda CR-V EX.  Later model vehicles now cut off battery charging when the current flow into the battery drops to a low level that indicates the battery is sufficiently charged - no moe constant running at 13.8 VDC!  My Honda CR-V quite often drops to 12.3 VDC while driving, and the 710A , which I use for APRS, will reboot whenever it goes into transmit (transmit dropping the voltage low enough to cause problems).  I solved the problem with an MFJ-4416C voltage booster which maintains a constant 13.8 VDC to the transceiver.  The booster can be set to turn off whenever the battery voltage input drops below a certain level.  It's interesting that both a Yaesu and an Icom transceiver in the same vehicle do not have any ill effects due to the low voltage.
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N4SRN

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #6 on: July 05, 2020, 11:42:20 AM »

Yeah, that little charger is 1.25A so not too good. My Optima 1200 brought the battery up to 14.5V in a few hours but it pulls down Fairly quickly. OK for RX but TX and it’s a reboot.
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Bret/N4SRN
Bedford, NH  USA

N4SRN

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Re: Kenwood TM-D710G Low On/Off Voltage Cycling in Go-Box?
« Reply #7 on: July 22, 2020, 05:06:47 PM »

OK, got that working well now. I’ve put a few retractable unshielded cables in the Go-Box, including a USB power cable from battery to laptop and RJ45 from radio body KWD TM-D710G to control head. Just the tiny KWD supplied ferrites on the control head cable.

All cables run to/from my Go-Box with antenna and laptop in a small space. Is RFI likely to be a concern on 2m/70cm? If so, which cables?

Bret/N4SRN
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Bret/N4SRN
Bedford, NH  USA
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