BB HSKY 48v and Renogy 500
 

Hi all,

Just upgrade to a Big Battery HSKY 48v and also installed the Renogy 500 battery monitor. All is working great but I noticed I have a constant 5w draw when not in use and key is off. Is that normal or do I have a leak somewhere?

Re: BB HSKY 48v and Renogy 500
 

i have the same setup...well, almost.
The 48v HSKY is up and running, but I have not installed the Renogy 500 as yet.
i'll be watching..

Re: BB HSKY 48v and Renogy 500
 

I have a different lithium battery but the battery shouldn't have anything to do with the draw you see on the Renogy (which I also have). I see right at 5w with the key switch on, and the solenoid not engaged (Onward / Navitas).

Don't know about the Big Battery units, but I'm assuming you have the Renogy wired outside of the BMS unit, meaning that any current draw from that will not be reflected in the Renogy's tabulations. I have a power switch that controls the voltage output from the BMS, and if I leave it "on" all the time there is about a 5% / week drain that is not reflected on the Renogy.Turning the switch "Off" when not using the cart and the drain is essentially zero (tested by letting it sit for a week or so both ways, then charging back to 100% and watch for the Renogy reaching 100% as it counts up at the same time the charger shuts off). I had a RoyPow battery before this and its SOC meter DID count the BMS power use (since it was wired into the BMS itself), but had a similar % drain if I left the battery power "on" all the time.

Re: BB HSKY 48v and Renogy 500
 

I have the same setup. I also have a 12v inverter and Alltrax controller wired to my power switch. EZGO TXT cart.

My meter reflects a 3-5 watt draw all the time, which I assume is the power required to power the unit itself (it is always on).

I reference the resting voltage against the displayed calculated SOC % each day and have found that it seems to be consistently accurate, certainly well under the 5% weekly variance loss posted above.

Unless you have the sealed charger from BigBattery, you have no way of knowing when the charge ends as the 15 amp charger fan runs constantly. Just be aware that is a "feature"...

Re: BB HSKY 48v and Renogy 500
 

Not intending to hijack the thread, but, if you happen to be watching the voltage display while charging, the point at which the voltage takes off rapidly from about 54.5 and climbs to 58.4 was the point at which the BMS "disconnected" the charger....(the charge ends..)

Re: BB HSKY 48v and Renogy 500
 

They have a sealed charger??? When I ordered they stated that they didn't.

Re: BB HSKY 48v and Renogy 500
 

Right, and BB told me that it is fine to leave on the charger. Don't know that I feel comfortable with that but so far so good.

Re: BB HSKY 48v and Renogy 500
 

Not implying that whatever battery / BMS you are using has appreciable loss as I mentioned when powered "on", but voltage is an exceedingly difficult way to reflect SOC with these batteries since the discharge / voltage curve is so flat, which is why the shunt-based coulomb counting meters are much more precise.

I don't have a "Big Battery" battery, nor their charger, but it's clear to see on the Renogy meter biterope has when any charger shuts off (if you can't tell otherwise) as the charge amp-rate reaches zero.

Re: BB HSKY 48v and Renogy 500
 

LiFePO4 (and most (all?) lithium chemistries) are going to give the best long term life when kept between 20-80% SOC, so if you are saying that leaving it plugged in at 100% SOC is fine, that is true that the battery will not overchage, but it is not the ideal state for the batteries.

Reading it again, I think you are saying leaving the charger running is fine. I don't doubt it, but the fan is pretty loud, so I prefer to not hear it buzzing while I'm not using it.

I'll prob install an outlet timer eventually and just charge in hour long increments or something instead of having to constantly unplug from the outlet between charge cycles.


Wasn't trying to disagree with you. I appreciate hearing your experience. Agree totally that lithium is difficult to gauge SOC.

You seem much more knowledgeable than me regarding these meter types. My understanding is that the Renogy meter is a shunt meter, is that correct or does another style of shunt exist that is different and would be more accurate?

I believe these meters are also programed with the lithium charge profile used to reflect %. I had a lead acid profile shunt meter previously that was grossly inaccurate.

Agreed, when the charger turns off the meter reflects it. Just a peeve of mine that on a standard charger you get an audible or visual queue. My RoyPow charger even blinked at different speeds to indicate 80% SOC status.

The one BigBattery uses has a power LED and an always-on fan. Annoying that I have to come all the way to the cart and check my meter to determine where my charge is, esp given that the meter isn't a factory paired option and could have variances in accuracy.

Re: BB HSKY 48v and Renogy 500
 

Renogy uses a hard wired-through shunt, however there are some available that use a coil that clamps over the negative cable. A hard wired one is generally thought to be a better option unless there isn't another way.

There is no profile involved in these meters - that would be something the charger would employ. The voltage display on it is a real-time value and SOC isn't derived from it.

The meters basically measure how much current, and for how long, and at what voltage (watt hours) is either taken out (discharged) or put in (charged via charger or cart's regen) through the shunted cable. You program how many AH your battery has into the meter, and this allows it to calculate a %.

A meter like this also allows you to see if the AH rating of the battery is accurate (i.e. is the battery actually capable of delivering what the mfg. says it can), and how the actual initial AHs delivered when the pack is new hold up over time and numerous charge / discharge cycles.