Wednesday, 11 November 2015

Clansman Battery Upgrade Progress

After waiting for what seemed like months, but was in fact about two weeks, I finally received an email telling me that the specialist Balancing Charger I require was back in stock. I jumped on the 'net and got it ordered, along with the Lithium Polymer battery. If i'd had a bit more spare money I could have gone with a much higher capacity (these are available at over 6Ahr!) but decided to save a few bob and stick with 4Ahr, the same as the original NiCd batteries.

The charger, a Turnigy Accucel-8 150W, is capable of charging and balancing up to 8 Lithium cells (8S), it can also handle up to 27 NiCd/NiMH cells, so will also do the original Clansman batteries, and it can do SLABs as well. The battery is a 7S 25C 4000mAh Zippy Compact Lithium Polymer (similar to the one pictured). This means it has a terminal voltage of around 26v. Its size is such that it will fit in the empty 4Ahr NiCd, but it only weighs about 650g - the originals are about 3kg!

But, its of course not that simple! These batteries if handled or charged incorrectly can be very dangerous. There is a risk of fire. The fact it will be installed in a metal housing goes some way to protecting against this, but further specialist electronics are needed to make this into a safe and effective power system.

Firstly, I need adaptors. The chargers main connection is a different connector type to the battery, so I need an adaptor to connect to the charger, and one to connect to the case terminals. I also need one that converts the 5+4 balancing connections to a single 8 pin connector for the chargers balance port. Then, I need a protection device to prevent over discharge. The PRC320 and PRC351 would quite happily keep taking power beyond the safe discharge cell voltage of these batteries, which would lead to a risk of rupture and fire. So, it needs one of these

This is a low voltage alarm module suitable for up to 8S batteries. When the cells reach the minimum allowable voltage it sounds a loud alarm. I intend to modify this to drive a cut-off relay instead. All this kit will be fitted into the battery housing. Whether I then add panel connectors for the charger, and a window for the meter display, I havent decided yet. It would make charging convenient. I would also need a reset button to reset the latched cut-off relay.
The charger is also capable of monitoring the battery pack temperature with a probe based on the LM35DZ temperature IC. It makes sense to include one of these bonded to the pack inside the housing, and provide a connection point to it as well, as an extra level of safety when charging.
So im now waiting on the adaptors and the monitor board before I can proceed futher with this. In the meantime, I have a couple of bids on for other Clansman items that im missing, notably the 1.2m whip and the carrier frame for the PRC351.
I also have the Simoco PRP70 series radios to play with. I have had to buy a USB 3.5inch floppy drive to get the programming software onto the DOS machine from my main PC, which doesnt have a floppy! Next step there is to build a programming interface and then find a facilities plug for the radios!

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