Will this ghetto trickle charge balance charge idea work?

Yes it will work as long as you connect and use it right. But it’s even cheaper if you build your own charger.

 

It’s just voltage doubler and current limiter for 110V mains. For 220v mains it’s just rectifier and current limiter. I’m not going to give any more instructions since anybody that should build one has more than enough instructions.

 

That actually is my plan if I should need a high voltage charger in the future, as I own several HP/Agilent lab power supplies and can generate the needed DC voltage with constant current limits.

 

No. Hv-battery control unit is off when power is off. It’s connected with block sense wires, so you couldn’t disconnect it anyways. Everything else is disconnected from battery (by main contactors) when power is off.

 

Yes exactly. My "emergency" DIY charger (240V mains here) is just the rectifier out of an old computer PSU and a bunch of 5W tail light globes - cost me only a couple of dollars to build.

However I don't post plans or recommend it to others here for exactly the reasons you state. It has absolutely no ground isolation and so could potentially give a lethal shock by just touching ANY part of the circuit. Definitely something that should only be used by someone who fully knows what they're doing.

 

I have isolated 220v ac to 0…220v ac 2kW variac (build in 1968) so I can use that to make it ground isolated and adjustable.

 

If you are making a low cost charger you can do it with LED power supplies in series and some wire nuts.
Totally dangerous. No fuses. No safeties. No on/off switch. You better have some high voltage gloves just in case
.....but it's cheap and anyone could put it together.

 

My plan, if I ever need to do it, is to use a bench DC power supply like the one you linked, and leave the ignition ON (just not READY) while charging, letting the battery ECU track the state-of-charge so I can read it over the diag port.

That's assuming, I guess, that the plug-to-nowhere wiring actually passes through the current donut inside the battery.

Hey, does anybody here know if the plug-to-nowhere wiring goes through the current donut?

(I might be asking a Gen 1-specific question ... do later generations still have a plug-to-nowhere?)

With a 200 mA bench supply you might need the patience of Job to fully charge the battery ... but on the bright side, it should definitely be hard to overdo it.

-Chap

 

Look in reputable sources for recommended cutoff voltages for an NiMH cell (about 1.4 V, maybe?) and multiply by the number of cells in series?

-Chap

 

I installed a Hybrid Automotive grid charger for a customer last week and according to their directions the battery will be balancing once it reaches 240v at a rate of 350mA. I can say from my experience reconditioning several thousand modules and assembling them into packs that you can't exceed 9.0v per module without doing damage and that's with a lot of cooling. That would put your pack limit at 252v. My advice would be bring it to 240v and the then continue at 200mA for 6-8 hours and that will be as good of a balancing charge as you will get with the modules in series.

This is my opinion based on my experience only. Good luck.

Also, this is for Gen 2 batteries which don't have the plug to nowhere. If your talking about Gen 1 with 38 modules it would be 325v, balance for 8-10 hours, never exceed 342v.

 

The voltage will be determined by the battery (its condition and and its state of charge) and the current that you put into it, NOT by the power supply which will be in current limit.

 

The battery acts as a voltage (fixed in the short-term view, slowly increasing/decreasing in the longer view as charge/discharge proceeds), in series with a resistance (ideally small).

If you have a current-limiting power supply and you set it as you proposed, it will operate in current-limit mode: it won't blow a fuse, it will just scale down its output voltage until the current flowing doesn't exceed 200 mA. That will be the voltage where ((PS output voltage)-(battery voltage))/(series resistance of battery and leads) = 200 mA.

You don't have to calculate that voltage, the power supply in current limit mode just finds it for you, and you'll be able to read it off the power supply's voltmeter.

-Chap

 

Hey Leaky Prius,
I use small laboratory power supplies every now and then and I think the current is the limit in your case. You can turn it up to 400v but your going to be flowing the same amount of power (200mA) as if you turned it down to 250v. As long as the PS voltage is higher than the battery it's going to be charging. No damage will be done but you will never be able to get the battery above 250v. Once a module is fully charged the chemical reaction converts the extra power into heat. But if you set your voltage to 240 and go it will charge until the PS and the battery equalize and then you could bump it up to 250 or 400 (it wouldn't matter) and balance charge for how ever long you want. If you charge a single module be careful if it's not in the pack, they will swell as they reach high charge levels.

 

Yes, it will probably peak out (somewhere) at about 240V and then dip back a bit and heat up as it overcharges. Here you could damage the battery if you leave it for too long.

Remember that when the battery is not fully charged then the power (voltage times current) is mostly going into energy storage (that is, being converted to stored chemical energy within the battery). But once it's fully charged then any current you pump into it just gets converted to heat.

If you set your power supply to a voltage of about 8.4 volts per module (235 volts overall) then the current will naturally tend to taper back as it approaches full charge - which is much better for the battery's health.