Quantitative Results of Grid Charge/Discharge

Yes this is correct. I regularly pull the pack to zero volts with the 25W (or a 15W) bulb before charging back up, and they perform excellent afterwords.

 

120-130F is the best temp for NiMH? My car seems to start ignoring the battery when it hits 120F (Won't charge fast or discharge fast)

 

No, those are definitely not ideal temperatures for the battery (too hot).

Yes 120F (49C) is pretty hot. The Prius will try to protect the battery by not working it too hard if it gets that hot. As another example, for those of us with the EV mode button, it stops working (EV mode denial) when the battery temperature rises to only about 42 or 43C (108F).

You should check that the battery cooling fan near the back seat is working correctly and that neither the duct work or the fan itself is too clogged up with hair and dust. See my pictures of a clogged fan here: Fur and dirt causing major battery problems | Page 2 | PriusChat

BTW. The fan should be running fairly fast by the time the battery hits 120F or more, you definitely should hear it. From memory the fan starts out at very low speed when the battery hits about 39 to 40C (104F) and from there increases the speed as the temperature rises.

 

I've already cleaned out the fan, and I manually control its speed on warmer days to keep the temps below 100 degrees using my ScanGauge. It usually sits around 95F once warmed up all the way.

Good to know that there is a solid difference between the best temperature and the most efficient temperature.

 

Yeah at first I didn't see where your question came from (now I see where S Keith mentions it).

I think the difference here is that warm temperatures do increase the battery capacity and performance somewhat. This is because a battery relies on chemical reactions and diffusion of ions in an electrolyte, and both of these are enhanced at higher temperatures.

However these same high temperatures are not desirable for battery longevity, and as it turns out, for precisely the same reason. Speeding up chemical reactions also hastens the undesirable side reactions that cause a battery to age. Additionally, if a cell gets too hot it can vent pressure and lose some electrolyte.

 

May seem like a dumb question but I was shipped the single bulb discharger so I tried making it a double bulb by instalking a 660w capable dual bulb socket adaptor. End result was 200w bulbs blew.

Are the bulbs supposed to be DC bulbs or AC bulbs.

 

I would message him, email or call, seems like it was a simple mistake putting together your kit. The bulbs can be used in AC or DC. Not sure about using the dual socket Adapter with the single bulb version.

The 200watt bulbs I used was these.
Shop SYLVANIA 200-Watt A21 Medium Base (E-26) Soft White Dimmable Incandescent Light Bulb at Lowes.com

 

yeah unfortunately that will not work. Our discharger is wired in series. This is required to spread the battery load over two bulbs instead of just one. It is too much for a single bulb (or two bulbs wired in parallel) and the bulbs will fail.

 

Jeff,

The two bulb discharger is wired in series, at least the one I got was. Was that a typo?

 

Question was answered by HA. I can't use the dual adaptor so I need to wait until the HA discharger arrives.

 

Doh! Need more coffee lol. Thanks for the catch, I just fixed the post.

 

what is gained by doing 3 cycles of charge discharge? why not just do a full charge for balance, and then discharge deeply all the way down to minimum voltage, i have read here from 17 V to zero, etc. if you stepped it with 200 W then 75 W then 25W, all the way down to 17V or less on the first discharge cycle... are we trying to avoid the weak cells going zero/negative for too long? but if we can go to 17 or less Volts slowly after 3 times , and some have said theres no harm in going to zero, why not just do it the first time?
i am not doubting that there is a reason, just curious, my garage is not close to my home, high rise condo, so checking in on the batt repeatedly would be a PITA, being able to drop it with the 200Ws quickly , and then put on 25Ws for a few days, would be easier. avoiding multiple cycles would be easier too...

 

jimbo, assuming you already did the full charge for balancing up top, you can just use the single 200W discharge for now.
Guru's, theres nothing wrong with the slower discharge right it would just take longer?
and you could leave the single 200 W on there until you get to 140 V, then go with a single 50 W instead of two x 25 W.
i didnt do the math, but slower in the beginning, faster in the middle, same at the end. time might not be that far off of the HA specs. can still get 2 cycles in a weekend and do the 3rd cycle later.

another question: in order to speed up the initial 2X200W discharge, couldnt jimbo start the car, put it in reverse (like we do with the HV battery test) to quickly draw off alot of voltage. then switch to the single 200 W bulb to taper it down to 140V ?? why discharge from 100% 235 V, to 83% 196V, or even 60% 140V so slowly ?
can he drop it to 140V with the car, and then use the single 50 W bulb to slowly draw it down to the prescribed steps ?

 

you are correct, my knowledge of series and parallel is limited ! vaguely understand how the wiring would be different but i dont get why 2 25 W bulbs which would be 50W, looks like only 12.5 W to the battery. i am sure it has to do with amps volts and ohms. i really never comprehended how they all interrelated... no need to explain, us newbs should just follow the instructions as written
i thought the point was to put a 2X25W load on the battery, to discharge it more robustly, when in fact the point is to put a 12.5W load on the battery to discharge it more gently.
can jimbo just use a single 200 W bulb to discharge his prius, and then a single 75W, and a single 25W... it would just take longer?
or am i missing the point that for the prius a two bulb discharger is required due to the battery load. so any single bulb will be blown... which part of the load, the voltage? standard bulb like 110-120 V, and the prius puts out 235V, is that why the 2 bulbs in series ?
sorry for the stupid questions. but i find this interesting, and i think the more people understand whats happening, the more they will be apt to get into charging discharging.

additional dumb idea, use 240V bulbs like from europe? then a single bulb would be sufficient.it is very possible i am still off base with my deductions.

 

No, it is not, the reason is quite different and a matter of practicality. As Keith said, single bulbs will likely blow at the higher voltages, but definitely blow at double the voltage. The reason why dual bulbs are used (in the USA) is another behavior of a series circuit which is that the input voltage is divided across the components, so, in the 2 bulb series circuit we are discussing, each bulb uses 120 V for the total 240 V going in from the battery. This behavior is what allows using USA 110 V rated bulbs so they do not blow. Also of interest is:

• Current: The current through each individual light is the same as the current throughout the whole circuit. If the current going to the circuit is 0.23 Amps, then the current through each individual light is also 0.23 Amps, not 0.46 Amps as I'm guessing is what you would assume.
• (As Keith mentioned) The total resistance equals the sum of all the individual “series” resistances.

These behaviors are what makes the math work (in Keith's post #119) out when considering power (Watts) and voltage.

This is not actually a dumb question.

If you could procure 240 Watt bulbs, then yes you could use a single bulb.

However you need to bear in mind that the wattage of your bulbs will effectively double in order to draw the same current.

A 110 V / 25 W bulb draws ~0.23 Amps;
A 240 V / 50 W bulb draws ~0.21 Amps.