Curtis SOC 906 Questions

[geonjay]

Just to get this out there - I have a digital voltmeter installed and it's great.

My wife, however, wants a "gas gauge" for ease of use. I explained that they can't be relied upon, and she's already memorized the 60% value on the voltmeter so she knows when to plug in....she still wants a gauge.

I'm looking at the Curtis 906. I have a 4x12 pack of Trojan T-1275's. There are a LOT of options for the 906, but I don't see many places that let you pick specific versions of the meter. My ASSumption is that choosing the meter that most closely matches my pack (Volts per cell, and reset options) will get it close to accurate - but it's still an assumption. Am I over thinking this? What I've picked out so far is 906T48*LAGN - the reset profile is confusing me a bit because I couldn't find exact info on the cell charge state. The volts per cell is a bit off also, according to Trojan's numbers. Anyone have an opinion?

[geonjay]

Also, I'm not having luck finding a thread that talks (specifically) about how to use the voltmeter to gauge my overall pack health. I've done some load testing (going up steep hills with a full cart) and I've observed a pretty wide range of numbers - but I'm not 100% positive how to interpret them. Starting out at 50.7 (sitting for 3 mins) I got her down to 43.7 going up that hill..but it bounced right back once we started going down again.

[Sergio]

The best Curtis Model For You is: 906F48HPA

F = Hexagonal 1/4" terminals (or Z for Rectangular 1/4" terminals)

H = Resets at 2.35 VPC (HVR) w/o memory

P = 2.08 VPC at Full, 1.98 VPC at Empty (32% SOC)

A = No Output Option

The Only 2 critical options are the H and P.

They also have Option L which is 2.10 VPC at Full, 1.92 VPC at Empty

While option L better matches the 100% SOC, empty really means empty at around 10% SOC.

The connections are:

Terminal 1 = Pack Positive.
Terminal 2 = Pack Negative.
Terminal 4 = Cold Side of key Switch.

[kernal]

Attached is the manual for the curtis 906 in case you haven't seen it.

I looked at the 36v curtis 906 that came in my EZGO (I'm the original owner). The model no is: 906D36HGAAZ. This is what EZGO used as the oem gage when supplied with the cart. I'm going to assume CC and Yamaha use the same one except in 48v versions where appropriate. So if you want the same as OEM this is probably it.

As I understand it, at 1.5v per cell under load physical damage is being done to the battery. So to be safe you should not let voltage drop under load below 1.75v per cell or 42v for a 48v pack.

Note that the 906 does NOT account for self discharge while the cart is not being used. This may or may not be an issue for you but in some cases this can be misleading. Hope this helps.

edit: The 906 doesn't account for short duration under load either. The rapid reacting digital gage is for that

[geonjay]

Thanks for the replies!

Sergio - I can't find that meter anywhere. I tried to break it down into the bits/pieces and I still can't find one that matches what you suggested...of course, I couldn't find one that matched what I thought would work either.

Kernal - Thanks for the manual - I'd already grabbed it from a post of yours in an earlier thread. I'll keep digging

[geonjay]

I nosed through all of the distributors that I found on the Curtis site..and guess what? I found one that let's you pick and choose the options!

http://www.tecknowledgey.com/curtis-...gauge-bdi.html

[kernal]

Not a bad price either.

[geonjay]

The meter is ordered. The final price was $61 shipped. I currently have my voltmeter connected to my key switch and a black/ground wire coming out of my dash harness. I was thinking of going ahead and running a new wire directly from the pack to my dash just for the SOC and volt meters - is it ok for them to run off of the same wire pair? Which gauge wire should I run? Is there any reason I shouldn't continue to use the keyswitch, and black/neg leads I'm using now? Can I connect the SOC to the always-on side of the keyswitch for the constant power AND on the switched side so the display is only on when the key is on?

[scottyb]

I have 2 problems with the gas gauge 906 gauge.
1. the gauge resets each time you charge the pack.
It takes the completed charge voltage or a % of that reading and establishes that as (full) or 100%. So while this number may be low if the pack's capacity is diminished the gauge will still read 100%.
2. The LED bars take too long to drop off the scale. In my side by side tests with a Fluke meter the first bar dropped off the scale at about 25% depletion. And the second bar dropped off the scale (now at 2 unlit bars & 3 lighted) and the pack was below 50% depletion!

Yes you can monitor & scale it but it changes......potentially each time you charge.

[geonjay]

Is there a better "gas gauge" that you'd recommend? I'm doing this to appease my wife...she really wants that style of gauge so she won't have to remember/look-up the voltmeter readings.

The distributor just emailed me to let me know that the "P" discharge profile (2.08-1.98V/C) is on longer available - per Curtis that option is no longer being made. So I went with the more dangerous, but realistic option "L" - (2.10-1.92V/C).