9V NiMH charging

koudelad — Wed, 02 Oct 2024 17:12:15 GMT

Hello,

9V batteries have always been a pain for me... Expensive, low capacity, almost every DMM / tester needed them.

I just bought a 9V NiMH battery: https://www.westinghousebattery.com/Ni-MH-Rechargeable/Premium-Series.html . To my surprise, it is not made from 6 smaller cells (which would give ca. 7.2-8.4 V), but 7, which has nominal voltage of 8.4, but when charged, can have almost 10 V. This makes it a true primary 9V battery replacement. I am not sure when these became available, but I remember older 6-cell "9 V" NiMH that were kind of useless, because all appliances thought the battery is discharged, due to the lower nominal voltage.

However, I never really had a charger for this kind of battery. I have heard that cheap chargers only use 12 V DC power supply with in series resistor in series to limit the current to ca 30 mA.

Do you have any suggestion for a charging circuit? I am open to building something, even using an MCU. I would love it to have a small small charging current (20-30 mA) or slightly higher (50 mA), a safety timer and the delta V detection. There is a famous old MAX713 charger, but according to the features, it offers C/4 to 4C charging and C/16 trickle charging, which is too high. Most commercially available hobby chargers also have a minimum current of 100 mA.

Thank you,

David

Nice new AD Parts

michaelkellett — Wed, 13 Mar 2024 16:12:17 GMT

I was going to post this in the Analogue Forum - but there isn't one, or maybe Audio (nope), or even "Instrumentation " - no.

So it has to be a blog here.

Just had a note from ADI about a few rather neat parts:

ADA4510-2 Op Amp with DigiTrim™
Analog Devices' ADA4510-2 precision, 40 V, ±70 nV/°C, rail-to-rail input and output op amp features DigiTrim

A very nice low noise, low offset dual op amp remarkably similar to the TO OPA2192.

Currently only available in 8 pin SOIC.

ADL5960 Analyzer Front End

Analog Devices' ADL5960 10 MHz to 20 GHz integrated vector network analyzer front end supports various LO interface configurations

It looks interesting but of course it isn't a complete VNA - I don't know enough about the design of such things to tell if its would make a good VNA or just a cheapish one.

The chip is £133 and the eval board is about £800.

ADG6412/ADG2412 Switches

Analog Devices' ADG6412 and ADG2412 0.5 Ω RON quad SPST switches provide high continuous current carrying capability

These are nice (if pricey at £6.94 each) quad SPST solid state switches capable of switching serious current and a wide voltage range.

and finally the:

MAX17614 Ideal Diodes/Power Source Selector Device

Analog Devices' MAX17614 4.5 V to 60 V, 3 A, ideal diode and power source selector has current limit, UV, and OV protection

These look quit nice - I rather wish I had fitted them to my laser controller - it has four buck regulators capable of about 20W each but no easy way to current limit them. If I'd known about these parts I could have used them both for isolation and protection.

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