I am neither a professional nor an enthusiast but needs must. My battery was obviously not well and I could not afford a new one. After standing for three or four days it would do a recall after a few minutes driving and I was getting IMA alarms which required a battery disconnect to reset, especially after accelerating hard on the motorway.
After researching on Insight Central and asking for help Peter Perkins loaned me a charger conditioner, sent me three spare sticks and I set to work in my summer holiday. I used a battery charger with the Honda’s under bonnet battery as a smoother to power Peter’s Robitronic charger/conditioner and a multimeter with a temperature probe (£20 ish) to keep an eye on things.
I was only able to insert the temperature probe between the black plastic and the orange cells in the end rows but that was enough to tell me what was going on without, and with, a cooling fan. Even out of the case the cells get very hot charging at 5 amps. (The second stick reached 56 degrees C by the third cycle). I ended up cooling them with a flannel dipped in cold water, wrung out and wrapped around the cells, replaced as necessary. After that experience I took off the integral fan and used an old car heater fan (you could use a mains powered fan heater on cold) and cardboard ducting held together with duct tape. This rig, also powered by the battery charger, blew through the whole battery enabling minimum dismantling and quick switching of charger leads from stick to stick. (The fan drew about one amp). I wasn't happy about possibly damaging the integral fan by running it 24 hours a day for ten days.
Once I was happy with what was going on with the end sticks I cycled the rest. 20 Amp discharge, 5 Amp charge, 5 cycles, about 8-9 hours per stick. It took 10 days and I did it on a Workmate in my bedroom changing sticks over when the end of sequence alarm sounded. (I didn't sleep well). In theory you could just do it over 9 days, Friday night to the following Sunday evening.
Peters Robitronic charger records the discharge and charge capacities for each cycle and measures the internal resistance, but as I discovered it loses all the info instantly when disconnected from the supply! I recorded the last discharge and charge in milliamps and the internal resistance. To find the discharge rate is time consuming if you wait 24 hours and then do a top up charge. I actually divided the top up charge before reassembly (in milliamps) by the time since the 5th cycle to get the daily rate. (Fortunately I had worked to a (fairly) logical sequence).
I actually had to replace four sticks which were self discharging at very high rates. When I checked one appeared to have a dead cell which was not warming at all when charging and another was just weird. It had a high internal resistance and on the fifth cycle it discharged 20% more than it subsequently charged. The 18th stick I worked on gave 32 mA on the first discharge. The first few gave about 4,500. Extrapolating from that some sticks were self discharging at about 600/700 mA per day. Later I found some that were self discharging at nearly 1000mA per day. Peter's spare sticks all had IR's of about 26 mOhms, mine varied between 42 and 56 mOhms.
Some sticks/cells were self discharging at very high rates. I suspect that after standing for a few days on starting up all appeared normal but, after a few stops and starts the duff cells dragged the whole battery down and triggered a recal/IMA alarm. From the foregoing I deduce that an even self discharge rate for all cells may be a critical factor. I tried to work out self discharge rates for each stick but unfortunately I had no idea the info would be important so did not note the time and date when I finished cycling each stick. Something for others to make a note of in future? To make matters worse three weeks on I was getting confused about my fairly logical sequence. (God Bless Amnesia!) What would be interesting and possibly useful would be for some enthusiastic person to collect data from other owners and see if it is possible to correlate discharge/charge capacity, internal resistance and self discharge rate. Possibly also against cell age and maybe also use/type of driving.
It is now over two months since doing the work The IMA light stayed on after reconnecting everything but reset itself next time I used the car. Since then I have had one IMA warning for no apparent reason which reset itself and one recal. It has stood for eight days with no problems except that autostop would not play until I switched off and restarted! I am definitely getting a lot more assist for longer. I do fear that I am putting off the inevitable replacement, however the battery consistently charges to 19 bars (two more than before) and with Honda’s miserly set up rarely drops below 13 or 14 bars, so I am beginning to think that keeping the battery fairly well charged and using the car regularly will prolong battery life. An in car conditioner/balancer sounds very interesting. It would appear that a few failing cells throw the whole system and cause a recalibration. Grid charging would help prevent a recal by keeping the battery charged when not being used, but would it help prevent cells failing? I suspect that “use it or lose it” applies.
It was definitely worth doing, the car is working better. More assist for longer and faster recharging. I am now regularly achieving 60 mpUSg (75 mpUKg) and completing my two hundred mile commute in three hours. (It is a CVT car but still uses less than half the fuel used by my brothers MX-5)
For those who may be tempted to have a go I can supply a little practical advice. However I must stress that there are high voltages, bare connectors, delicate electronics, puzzles, fiddly bits and heavy units to move/lift.
THERE IS POTENTIAL TO DO YOURSELF SERIOUS INJURY OR EVEN KILL YOURSELF
Having said that I am not a professional electrician or electronic engineer. I am a former ships officer with some radio and domestic wiring experience. By taking my time and seeking help when unsure I was able to complete this work safely and satisfactorily and save myself a lot of money.
Battery reconditioning experience
