We got a request to repair a battery for an electric golfcart, Jucad Carbon Travel, bought in 2009. The battery was still working after more than 7 years of use but the capacity was not enough to play a full game of golf. Official reseller Moby Dick was offering new batteries for 6000 sek (€600) and repair batteries for 4000 kr (€400). Both options are quite expensive since we are talking about a 24V9Ah battery.
This is the smallest battery pack we have seen and it does not weigh much, about 1500 grams. It comes in an elegant bag and also has a hollow golf ball for plug protection! It takes 8-10 hours for a full charge since the charger only charges at 0.56A. However, we know that slow charging is one of the secrets to long lasting batteries, and this is a major reason it can still be used after 7 years!
The plastic case is very anonomous and only at the bottom can we see the logo.
The four holes are for ventilation. On the bottom side there is a kind of insulation filter, probably to let air pass through but to prevent water from coming in. It could also be a heat vent.
We were surprised to see this electric composition when we opened up the battery! First we thought it was the BMS, however, then we noticed it only had two wires going from the battery pack making us believe that this was some kind of mysterious self balancing pack. But after more observations we now know this is the controller for the golf-cart that has been built into the battery.
On the label we can clearly see all perimeters, values, dates and more.
This is the OLDEST battery we have seen with 18650 cells, which did not become standard until 2013. This is also the early Panasonic cells with dots instead of stripes.
All cells are glued together and spotwelded. However they did not make 2S4P blocks to match the configuration. Also they have solded the wires quite close to the cells.
Since the battery has been used for many years and also in heavy rain some moisture has made its way into the battery and corroded one of the corner cells.
The BMS is ultra thin and hidden between two paper sheets. We don’t believe the gold colored parts are actually gold (which has excellent conductive properties) but it looks elegant, and according to Wikipedia gold-plated PCBs are actually a thing! Also a BIG confusion is that the “C-” actually leads to the battery, AND the “Batt-” is actually both “C-” and “D-“! The battery also lacks solder-free terminals unlike most modern BMS’s.
In repairing the battery we decided to use the old configuration but with modern panasonic cells and could therefor increase the capacity with about 50%. We also added an IMPORTANT extra layer of protection between the serial cells, which was missing in the original configuration.
We don’t like using hot glue but the small space gave us no choice.
The additional protection made the battery 2 mm longer and of course there was NO extra space! We did not want to force the pack tighter so we saw this as an opportunity to add some extra water protection. We also added some black electrical tape so now moisture will have a hard time getting into the box!
This is the 7 year old model, it does not feature a remote control and can only be operated by a throttle. There are some videos available of the JuCad in action for those interested in seeing more. However most of the videos are in German, like this one for example: