Discharging 400AH cells

[spdas]

Aloha, I have a bank of 400ah "Thundersky" 3.5v batteries and one of them is a bit high. All the others are at 3.35v and this one is at 3.5v already. How do I knock it down? I read all about toasters and heating elements here but they assume 36v or so, but mine is only 3.5. What can I use?

thanks
francis

 

[dustNbone]

A parallel string of 12V automotive bulbs has worked for me, but 400Ah is a bit cell so it might take some time. Any resistive load that can handle the voltage will do, it's just a matter of how long it takes.

 

[InterestedinEVs]

Carbon pile load tester. Harbor Freight has them, sure amazon has plenty, too.

 

[spdas]

Carbon pile load tester. Harbor Freight has them, sure amazon has plenty, too.

It says it is for 6/12 v. How will it drain a 3.4v battery? Will it take forever? I have the smaller/plain load tester that you hold the switch on and it heats the element inside, is this the same as the Carbon Pile Load Tester?

 

[liveforphysics]

I have a 5kW DC load that works awesome for that, but when I don't have it around, I use strips of stainless steel, bend them into a 'U' shape, put oven mits (or kevlar glass blower mits) on and short it across the terminals. Remove bar before it's glowing unless you're into wearing flaming mits and enjoy blisters.

AISI Type 304 Stainless Steel
Physical Properties Metric English
Electrical Properties
Electrical Resistivity 7.2e-005 ohm-cm 7.2e-005 ohm-cm

It's easy to calculate whatever load you need this way by the length and cross section of the strip. If you like to bleed large cells down rapidly, I recommend a 1/2" * 1/8" thick 304 stainless strip 6ft long bent in a U-shape so you can smash it against the terminals.

 

[Overclocker]

nichrome wire