That makes me think of an old slogan, and mutate it to "WWBOFH do?"
Telequipment D32
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Use tags for the type of equipment your topic is about. Include the "repairs" tag, too, when appropriate. If a new tag is needed, request one in the TEAdministration forum.
Use tags for the type of equipment your topic is about. Include the "repairs" tag, too, when appropriate. If a new tag is needed, request one in the TEAdministration forum.
Re: Telequipment D32
Ok minor update. Mostly thinking. I looked at power options because quite frankly replacing the NiCd cells is a no. Options considered were:
1. Replace with NiMh. Discarded due to cost.
2. Replace with power bank and USB-C. Discarded due to cost, complexity and safety.
3. Run on external DC power only. Urgh just no.
4. 8V SLA. Discarded as requires mechanical and electrical work.
5. Convert existing charger into 7.5V series regulator. Bingo.
So I did some scribbling and I can remove about 8 components from the HV board and reuse the charge transistor for this. Add three new resistors and a TL431 as a reference and job done. I will order the bits tomorrow which total about £2. This is still only a little more than 10% of what I paid for the scope so border line acceptable
This is similar to the battery eliminator circuit mods I did on Fluke DMMs.
1. Replace with NiMh. Discarded due to cost.
2. Replace with power bank and USB-C. Discarded due to cost, complexity and safety.
3. Run on external DC power only. Urgh just no.
4. 8V SLA. Discarded as requires mechanical and electrical work.
5. Convert existing charger into 7.5V series regulator. Bingo.
So I did some scribbling and I can remove about 8 components from the HV board and reuse the charge transistor for this. Add three new resistors and a TL431 as a reference and job done. I will order the bits tomorrow which total about £2. This is still only a little more than 10% of what I paid for the scope so border line acceptable
This is similar to the battery eliminator circuit mods I did on Fluke DMMs.
Re: Telequipment D32
Ok, since the talk with 0x57 about the NiCd in his Yokogawa, this stuff is in the back of my mind.
So this was a 7.2V nominal NiCd, so 6 cell. As per the discharge curve:
one would expect the circuit to charge up to about 1.4Vx6 and work down to 1Vx6, so 8.4-6V.
Now as we all agree
LiFePO4 is superior for such application, but (how) could it fit?
Looking at the curve:
we could go up to 3.4V/cell, but for a standby float charge you want the relax voltage after charge so 3.3V (looses us 10% capacity),
discharging down to 3V looses us another 10%, but with two cells in series we could fit the voltage envelope using ~80% of the cell capacity.
Since they are just fine with beeing CC charged and then floated, only charger mod would be a limit of the float voltage to 6.6V,
add a 2S LiFePO balance/protection board, done!
Do you agree?
So this was a 7.2V nominal NiCd, so 6 cell. As per the discharge curve:
one would expect the circuit to charge up to about 1.4Vx6 and work down to 1Vx6, so 8.4-6V.
Now as we all agree
LiFePO4 is superior for such application, but (how) could it fit?Looking at the curve:
we could go up to 3.4V/cell, but for a standby float charge you want the relax voltage after charge so 3.3V (looses us 10% capacity),
discharging down to 3V looses us another 10%, but with two cells in series we could fit the voltage envelope using ~80% of the cell capacity.
Since they are just fine with beeing CC charged and then floated, only charger mod would be a limit of the float voltage to 6.6V,
add a 2S LiFePO balance/protection board, done!
Do you agree?
Re: Telequipment D32
I do but Chris seems to want the easy way out with the least investment.
Siglent Distributor NZ, TE Enabler
Re: Telequipment D32
A good engineering solution but I doubt it meets the very severe cost constraints necessarily imposed on this project. i.e the serious cheaping out involved. 
Re: Telequipment D32
Well, at about 15€ for two 2Ah 18650 cells with shipping and like ~2€ for a China 2S BMS (OK, make that 5 and buy two...),
I don't think it's unreasonable
I don't think it's unreasonable
Re: Telequipment D32
I think he's more into the 5€ range and 6€ would be stretching it. He paid about €30 for it in the first place, and in my view he was robbed.
Re: Telequipment D32
Still... the entire porpoise of the scope is to swim free on battery power; seems just wrong on a fundamental level.
mnem
guess I can still trailblaze with Lixx power on that 211...
mnem
guess I can still trailblaze with Lixx power on that 211...
Re: Telequipment D32
Well the purpose of it is to piss around with something on the slow and winding path to my ultimate demise.
Alas I've had more important things to do so I haven't even looked at this yet. Important things being work, floozies, trolling people and occasionally learning something
Alas I've had more important things to do so I haven't even looked at this yet. Important things being work, floozies, trolling people and occasionally learning something