Frakentrike wrote:Having run it in parallel with the first battery for a short while in my tests over the last few days, I wonder if that might also have caused issues?
Unlikely. At worst it would discharge one to charge the other, if they were at different SoC when you plugged them into each other. If one was already near LVC when hooked to the lower voltage one, it would just cutoff if it got down that far, but then you'd probably have already known it (they) were low at that point.
I assume when you run two batteries in parallel, best practice would be to ensure they are as similar to each other as possible? Both batteries are supposedly 48v, but they have different full-charge voltage values - the first (rated at abut 10AH) charges up to about 51v and the second (a physically narrower battery that may only be 8AH) goes all the way to 53v off the same charger.
Generally it's better to run two identical packs in parallel, but as long as they are the same voltage to start with when hooked up, it doesn't matter--you just won't get full capacity out of the higher voltage pack if you have to have it partly discharged to hook them together. (if there is a voltage difference, a very high current will flow from higher to lower and could damage your wiring if it's high enough).
I run an A123 20Ah 16s and an EIG 20Ah 14s, and occasionally hook htem up in parallel, but only with the EIG a little low, because while both have the same full charge voltage, that's only because the A123's balance-level voltage is the same as the EIG's FCV. Generally I only run them one at a time, even if I need extra range on the trike.
If your packs are different FCVs, then either they are different chemistries, or different numbers of cells in series, or both. (or the chargers are not correctly set, if the packs themselves are identical).
It might be time to buy one big 20AH battery (rather than two identical 10AH batteries to run in parallel).
If you always need the extra capacity (and C-rate), or often do, then you might be better to have just the one big pack.
If you hardly ever need that, and don't want the extra weight on there (or the space is needed for other things), then two packs where you can leave one off might be better.
I did find that if I stopped pedalling while going up the steepest hills on my commute, the motor would cut out when only running off one battery, while when I was running another identical battery (that died a year ago) in parallel, the motor had more than enough power. I wonder if that might have been caused by the gauge of the wire going to each battery being a little bit on the lightweight side of things?
Unlikely. More likely the cells just couldn't put out the current with just one, and so one or some hit LVC, or the pack's BMS detected overcurrent for the one pack, and cutout.
What does your wattmeter show as a load on those hills, without pedalling, and then again with pedalling?
What does it show on level ground?
(The batteries use standard IEC "kettle cords" which being rated for 240v AC, always struck me as not the most optimal solution for high amperage DC).
It's not so much the current, I think, as the serious potential for accidentally plugging stuff directly into the wall, forgetting the charger in between.
Anyone have anything good or bad to say about a 48V 20Ah Headway Battery Pack from Dillenger as a replacement?
Only thing to be said about headway or ping is that neither is a high-c-rate pack, so you should get one with the Ah equal to or greater than your typical worst-case constant current draw (like on those steep hills), as they will have greater sag at higher c-rates than 1C (1 x packAh), and worse as they age, and it will also age them faster to draw that a lot.
They can both be used at higher rates, and may be rated for 2C or even 3C, depending on the cell versions, but various threads have shown they'll probably be better off at lower rates.