After the whole set of failures with the Soneil chargers, I learned from the distributor that the 1214S model doesn't support series strings of battery packs:
Well, based on this email I sent an email to Soneil. Apparently there has a
been a design change in some of their chargers (these included) which
prevents you from being able to charge while in a "series" configuration.
This means that the half with no LED are dead. This also means you can't use
that charger type with that configuration. I apologize for this huge
inconvenience, I have no idea why they would change the design. The closest
12v Soneil charger we have that does not have this design change is the
1212SR, but it is a 5amp and is $89.95ea. We can refund your order or
replace the same value with 1212SR chargers, I'm not sure what else to offer
you. Both issues you have found have been somewhat unbelievable, I apologize
for the "luck" on this. For the electric bike application, both charger
types work great. The electric car application has a few unexpected
Mike (from ElectricRider)
After hearing the above, I returned the Soneil chargers and asked ElectricRider to ship me a set of their in-house Joule chargers (model JJ12060). Their technician insisted that the chargers should be fine for a series connected battery pack.
About a week later, the box full of Joule chargers arrived on schedule.
Here's the pile of twelve Joule chargers after I stripped off some insulation and added ring terminals for the batteries. I'm really excited because these are smaller than the Soneils and have integrated cooling fans. Despite the 35-40mA current draw, I'm full of hope that these will solve my pack imbalance issues.
After installing several of the chargers, I observed the following:
- One failed to even start up (LEDs were flickering)
- Six didn't have their fan come on. I thought that the fan might come on after the charger heated up, so I left one on for 20 minutes. The unit overheated and ceased to work. One of these six had its 100% charged LED stuck on, possibly indicating other issues.
- Five powered up correctly; however, the fan on two of them seemed to get up to speed very slowly, possibly indicating fan bearing issues.
I'm taking a day to ponder my alternatives. The Belktronix charger has a lot more "spaghetti" to it as well as hot shunt resistors. On the flip side, it has a very high PFC value which means that the primary charger is quite efficient and it doesn't heat up much. The charger is also sealed, making it much more resistant to dirt and bugs.
One option I'm considering is replacing the shunt resistors on the Belktronix charger with 50-watt halogen light bulbs. This means some of the shunted energy gets converted to light instead of heat. I'm also looking into a circuit to replace the charge detector in the Belktronix system.
EV Awareness Day here in Portland is only three weeks away and I've got to get this beast charging correctly. Here's to being stubborn. Stay tuned.