Keysight U1253B meter - lithium ion 9V compatibility? - Page 1
Forum section: electronics / testgear

author: sammyhwang
author_rank: Contributor
timestamp: October 17, 2016, 01:20:45 pm
content: So.. Despite all the negative reviews about the battery life and continuity tester, I finally bit the bullet and gave in to the sexy oled display.Now I wonder if there's any way to improve the battery life. I see some 9V lithium ion batteries with a nominal voltage of 8.4v claiming to have1000mah. That's almost 3x the original (24hour battery life?) I know it would probably work (manual says original nimh 9v is also 8.4v nominal and the meter accepts alkalines) butwould it recharge?Anyone know anything about the recharge circuit in the meter? Is it a generic circuit or is it specifically programmed for the 300mah battery? Any insight would be great, thanks.My original idea was to 3d print a mount that screws onto the battery holder and extends out to accept either flat lithium ion cells or 18650 batteries. But if I could truly get ~ 24 hours by switching a battery I'll see if I can live with that.

author: FrozenHaxor
author_rank: Contributor
timestamp: October 17, 2016, 05:23:56 pm
content: The built-in charger is a standard NiMH constant current with negative delta detection (stopping the charge and measuring a voltage drop during a given time) I believe, judging from the charging behavior.Surely the technical detail is there, it's just the software that's needed in order to support constant current -> constant voltage charging that lithium batteries require. I wouldn't try just jamming any lithium cell in there and hoping for the best, you'll probably get a charge error message from the meter pretty soon anyway. I just used a GP brand battery and I'm happy with the results. Also the voltage given by lithium cells is not quite right, It's either 7.2V or 11.1V. From experience these meters have ADC problems when the voltage rises too high.I would be interested in somebody else's take on this matter.

author: ArcticGeek
author_rank: Regular Contributor
timestamp: October 17, 2016, 07:03:43 pm
content: I would agree that this seems unlikely that it would work, but I really do think it would be cool if it could be done. The Li-Ion batteries have a lot more capacity than NiMH, so the benefit is obvious.I have no idea what kind of charging circuit they use, I have a U1252B that doesn't charge properly and I've tried to see what might be the cause, but it's not obvious. I tend to think it's some kind of discrete charging circuit that is controlled by the microprocessor of the meter. I certainly have not found any charge controller ICs from Linear Tech or TI/Benchmark that are present on the board.As far as the voltage is concerned, there is an option to select either 7.2V or 8.4V in the meter setup screen. Older units used a 7.2V 300mAh battery, newer ones use a 8.4V 250mAh battery. It might be an interesting experiment by putting one of these high capacity batteries in your meter and monitoring the charge voltage/current is (with the battery OUTSIDE of the unit in case it gets hot)....but I'd be careful in doing so. The last thing you would want is for the battery to get too hot and catch fire/explode.

author: bitseeker
author_rank: Super Contributor
timestamp: October 17, 2016, 11:16:09 pm
content: The charger in the U125xB is designed for NiMH batteries. Li-ion batteries have different charge requirements and should not be overcharged nor trickle charged once full, two things that are OK for NiMH to some extent. Thus, I would not use the built-in charger to recharge Li-ion batteries.Instead, if you want to take advantage of the increased capacity of Li-ion, use a separate charger intended for the Li-ion battery and then install the full battery into the meter. Also, verify that the battery has protection circuitry to prevent over-discharging it (or you'll have to be sure not to run it down too far).Quote from: ArcticGeek on October 17, 2016, 07:03:43 pmAG, what's wrong with the charger in yours? My U1252B would overcharge and cook batteries. I sent it to Keysight for replacement. It was the first time they've heard of the problem. Is yours similar?

author: ArcticGeek
author_rank: Regular Contributor
timestamp: October 18, 2016, 12:34:58 pm
content: Bitseeker,I actually have a total of 3 U1252x meters. One is a U1252B that is essentially brand new, an older U1252A, and a recently acquired U1252B that was used and sold as "parts only". The new U1252B and the older U1252A seem to charge okay, but the recently acquired U1252B does not charge properly. Like your other thread describes, the battery gets hot. Other than charging not working, the meter works perfect. The first time I charged the battery I didn't really pay that close attention; I left it to charge overnight. The next morning I noticed that the outside case of the meter was quite warm where the battery compartment was so I removed the battery and found it was quite hot. I immediately thought of your problem that you had with a hot battery.I have actually started a bit of investigation on this - I will start another thread rather than highjacking this one.

author: HKJ
author_rank: Super Contributor
timestamp: October 18, 2016, 01:05:36 pm
content: I believe there are two types of 9V LiIon batteries:1) 2 LiPo cells in series with nominal 7.2-7.4 volt, output range is 8.4 down to 6 volt.2) One LiPo cell with a boost converter, output voltage will be fairly constant. Charging will be with a usb connection to the cell.I doubt any of them can reach 1000mAh at anywhere near 9V

author: saturation
author_rank: Super Contributor
timestamp: October 18, 2016, 01:14:39 pm
content: ~5 years I've seen 9V 600mAh rechargeable Li cells at Amazon [ EBL brand] for about the same price as Tenergy 200mAh NiMH LSD, that's 3x the power density. It seems like a good idea.In most typical usage, 9V are used to their cutoff whether it be a DMM or a smoke detector.Charging issues aside, keep in mind secondary Li batteries reduce their cycle life with depth of discharge as well as the ambient temperature of cycling. NiMH chemistry isn't so affect by DoD so in use its more carefree. So While the DMM will last longer between charges, the battery itself may need earlier replacement than NiMH chemistry.

author: HKJ
author_rank: Super Contributor
timestamp: October 18, 2016, 01:19:18 pm
content: 600mAh is about correct. The LiIon batteries includes a protection circuit, i.e. you will never discharge them totally.

author: saturation
author_rank: Super Contributor
timestamp: October 18, 2016, 01:32:47 pm
content: Yes, its just the more DoD the less life you get, how the users actual life will depend on the ambient cycle conditions, the quality of make etc.,NiMH cycle life is more independent of DoD.Quote from: HKJ on October 18, 2016, 01:19:18 pm