Tcs keep alives

[Alan]

Trying to elaborate on Alan's RC diagram a bit (and I hope Alan will forgive me when I don't use the correct terms), but all capacitor based Keep Alives (at least on the market today) will follow the same law. The length of the curve and it's voltage drop is just a matter of how much power is stored and how fast it is consumed. The law applies whether it's a RailPro module or a DCC decoder the Keep Alive is powering; the locomotive will slow down as the voltage drops as the Keep Alive tries to provide the same level of current to power the module/decoder until there is no power left to consume. This is why some may see what appears to be Keep Alives working in some cases but not appear to be working in others. A Keep Alive providing 1000mA of power will drain (read slow down and stop) quicker than the same Keep Alive only providing 500mA of power.

I'm struggling to come up with a way to explain the initial massive voltage drop Kevin reports when the Keep Alive kicks in after power is lost for those that don't know why with giving an analogy that'll either be wrong or just more confusing. Alan help!

Anyway I've got no idea what the law is called, if it even has a name as a "law" but I'm not sure even Tim Ring can get around it to provide a constant speed until all the available power is consumed, and provide a decent run time.

- Tim

I believe you are thinking of Kirchhoff’s Voltage Law.

[G8B4Life]

I believe you are thinking of Kirchhoff’s Voltage Law.

I'll have to take your word on that's what I'm thinking of Alan; I looked up Kirchhoff’s Voltage Law and didn't understand a word of it.

I don't express myself very well on these subjects, not easy without the proper background (I should probably leave all electrical explanations to you). For reasons I don't remember after only several hours I was trying to explain for the readers why the voltage drops in a Keep Alive (leading to the loco slowing down) instead of the voltage staying the same as what the capacitors in the Keep Alive were charged to until all the power is consumed (loco stays the same speed until no power left). I'm sure I got the right reason, but maybe not the right words. Please correct me if the reason is wrong.

- Tim

[Alan]

Finally a keep alive that is guaranteed to work!

[KPack]

Finally a keep alive that is guaranteed to work!

Think I can fit two of those in a SD40-2?  I'd like to have backup as a fail-safe.

[Blueleader]

Talk about instant death if you touch that beast. I run a 1 Farad cap in my truck audio system as instant backup for the sub amp and it makes me nervous to be around when it's charged