Anyone here tried 84v yet?
My controller will go to 84v and x-treme just sent me another battery from a mess up they had on a previous order. I am currently at 72v and have had good results so far. Bike is running very close to 30mph flat top speed. So I was thinking of possibly trying it at 84v but I am concerned with the amount of current and voltage. I don't want to fry the motor or wires to the motor. I am also concerned about the LVC on my controller. It is set at 62v and with 7 sla batteries it would need to be raised. Which would require me to it apart and change some of the resistors. Your Thoughts Please
I would recommend being very careful with those Werker 18ah batteries!!! I wasnt careful and I ended up cooking my stock battery pack!!!! Due to bad balancing and using a 60V charger. Also... I have a post on here of where I put my 5th batter (hint... Its not in the under seat compartment....) I will look for it and post a link here in a bit....
not sure what happened to the pics... I'll have to see if I still have them....
Keep in mind the multiple posts throughout this site warning against mixed batteries. If you dont use Same Voltage, same Ah rating, and some would say same brand, as well as lot number if possible (at least bought at the same time from the same place), you run great risk of unbalancing your pack and damaging all of your batteries. The reason same brand would be important is not all brands use the same testing labs or criteria for rating batteries, since sales of batteries are a numbers game. Even within brands, some make batteries for high current, deep discharge, or low current steady discharge of the same current ratings.
Mixed AH ratings will only cause trouble in two cases:
- If you run the pack until that small battery is driven into reverse current, or
- If you change with a single series charger for the entire pack
Lee Hart has a batt-bridge circuit that would let you monitor the pack to stop draining it as soon as you reached the "hockey stick" bend in the discharge curve.
Running the converter off only the 5 20ah batteries just MIGHT help the discharges to be equal. But in general, the 18ah battery will discharge at a faster rate and have a (albeit very tiny) slightly lower voltage than the 20ah do. If you are charging with a 72V charger after just a few charge cycles there is a LARGE risk for damage by overcharging. Unless you charge a battery pack in parallel the voltages will not even out, if 1 battery starts at 12.8V and the rest are at 13.0V that one battery (I dont want to calculate values so they are just an example) when the pack was done charging you would have 5 at 13.8V and one at 13.6V. This is not the huge problem yet though...... Each time you discharge the pack any decent amount, that battery will drop .2V more than the others. IE, the 2nd time you would have 1 battery at 12.6 and the rest at 13.0V... when done charging u have 5 at 14.0V and 1 at 13.6V.... I am sure you can see how after 3 or 4 cycles you have 5 batteries trying to charge up to and over 14.7V.
But as I said earlier, the fact that you are running the dc-dc converter off of 5x20ah and the 18ah is only running through the controller, that just MAY be enough to keep them perfectly balanced and still use a 72V series charger. But pretty much ONLY if you always run the bike about the same length of time and have the lights on or off EVERY time you use it.
Hope this helps.
Electrons are electrons. The quality of a battery will control how many electrons are available, but the discharge RATE depends of the load you are putting on them. In a series pack, each battery MUST give up the same number of electrons. (On the charge side, that same statement is the cause of the problem: each battery sees the same number of electrons even though some batteries may need fewer; batteries can tolerate a small amount of overcharge which can allow a series pack to regain some balance, but it is easy to boil off too much water and destroy a battery.)
Now, Peukert has something to say here as well: A 20AH battery discharging at 10A will be very slightly more efficient than an 18AH battery at the same rate.
I'd recommend setting up a series/parallel plug and charging all batteries in parallel. That way you at least will be starting each ride off with the most balanced pack you can get.
If you use 5 of the 20ah extreme batteries and those are connected to the converter, and the 18ah only for motor/controller power, and charge using the 60V and a 12V chargers you should be fine. I would just suggest occasionally checking battery balance so you dont run into any problems.