Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing BATTERY MAINTENANCE

I thought it might be best to post the following thinking on battery maintenance in an easily searchable thread of it`s own, whereas it was contained in a thread with the heading

RE OVERSTEER WARNING LIGHT...thus unlikely to help someone looking for info on Battery maintenance...?

Originally Posted by Luddite
Originally Posted by aerotaff
Never knew that about locking the car. You learn something new everyday. Keeping everything charged up certainly keeps the gremlins out on the plus6

IBoth my 2012 ICE propelled car and my old Mog are permanently connected to their CTEK float chargers/battery conditioners when not in use, which assists in avoiding the multitude of possible dash warnings that can be randomly generated as the battery voltage diminishes over time on semi regularly used or worse still stored for months on end...Hmm..? (-:
Someone (sorry memory failure) typed that they had heard that having a CTEK almost permanently connected to a battery can cause issues....? Must have been in a different thread and I responded with a rough record of my normal usage over quite a few years with no apparent issues..... However, just spoken to a tec this morning who seemed to think while CTEK are quality units, his experience is that AGM and perhaps other battery types can have issues if spending the majority of time connected to a CTEK, and quoting that battery`s prefer to be regularly discharger and re-charged, which has ever been my experience with old style led acid batteries, though with AGM and later batteries... I have no real knowledge of the way they are likely to respond to long term CTEK connection

There is a recondition (recond) option built into the CTEK MX 5.0 charger I have for my 2012 non/Morgan vehicle with an AGM battery which I think at the time was fitted to cars with stop/start tec..

From the CTEK manual.. Recond your battery once per year and after deep discharge to maximise lifetime and capacity.

I have not ever followed this process, and should have... Duh. Just wanted to modify my original post, with a tad more info in the hope it assists in avoiding battery issues, of which there are ever many and usually at the beginning of the motoring season..

RICHARD V6 advised :-

Yes not optimal to leave any battery permanently on a battery maintainer or smart charger. As you suggest George battery longevity is greatest when it's regularly but lightly used discharging from fully charged to say 90% then back to fully charged.

Leaving it long term on a float charge causes stratification of the electrolyte on a lead acid battery and this whilst it's in its most acidic fully charged state causing plate errosion. Some sophisticated chargers are programmed to run the multi stage charge cycle every 15 days ago causing electrolyte to be stirred to offset stratification. You can of course simply cycle your charger off then on to provide same every couple of weeks.

The policy I adopt is to use my vehicles at least once every three weeks throughout the year supplemented by 24 hours on a smart charger every couple of months. This undoubtably pays dividends. Remember also batteries are consumables though and a regularly used one on easy starting car will mask the inevitable ageing process as sulphation of plates reduces battery capacity. Warning signs are when put on a smart charger it reaches fully charged in short order.

My 4/4 Track Day Edition has a battery cut off switch, which negates any need for a trickle charger when the car is garaged over the winter. It starts first flick after months of lay up and is the easiest way to solve battery drain problems.

Oh the joy of a BEV. The traction battery monitors the 12v battery & charges it as required whilst stopped.
The 12v is needed to run the pcs controlling it & the 400v battery contactors.

Seems ironic that old technology batteries are required to control new ones. Understandable on hybrids as the 12 volt battery is needed to operate starter.

I know but I guess a separate 12v circuit works .

and keeps you alive

Yes very true there some serious HV stuff on them. Not much to tinker with. Typically an 80 to 150 kWh battery at 400v.

Janice has range anxiety so she is getting a new Clio HEV now that is complex under the bonnet.

Seems in true TM fashion we have drifted off into discussion of EV... As a serial drifter I can not complain.. (-: I guess my hope was to create a simply searchable discussion on the eternal question of battery issues as tends to befall irregularly used classics.

Barry I suspect your kill switch seems unlikely to halt the general INTERNAL ageing process that is inevitable in battery`s over time, more that it cuts out any chance of discharge through any of the on board circuitry. Also I guess that while the the kill switch works for you, it may not suit all Morgans, thinking of those with digital kit that may provide issues when deprived of power, and not discovered until the power is restored at some later date...?

On the other hand in pre digital Trads, the killswitch if used as you suggest would cut down on EXTERNAL parasitic losses that can flatten a battery over some period of time even to the stage where it can not be recovered as the result of those external losses. My mid 80`s +8 has an immobiliser system which places a constant although minimal current draw on the battery and would in time have the possibility of draining the battery into a situation where it can no longer fire the engine up. likewise an electric clock, etc.etc.

As I typed earlier I over depended upon a CTEK clever monitoring and conditioning system to counteract both my +8`s immobilisers external drain and it`s battery`s natural chemistry causing internal losses, which like your kill switch, my CTEK has worked rather well for me over many years in terms of battery longevity for the old style non AGM lead acid, Other than that I tended to replace my +`8`s battery every 3 years or so in the hope of avoiding sudden internal failure when far from home... I looked upon replacement as an insurance policy.


I have little in the way of experience with AGM batteries. My expectation is that they are better able to cope with the demands that modern vehicles complex circuitry demands and no more so perhaps, than the introduction of stop/start operation...?

I bought a circa 9 year old car with all the bells and whistles of a high end vehicle, according to the date code on the AGM battery it directly related to the year the car left the factory. I bought a CTEK suited to coping with the requirements of an AGM battery. All went well for quite a few months, until forgetting to connect up the CTEK after it`s last run, caused the car to fail to start after I think 8 days. Thus a replacement battery was fitted..

Four years on from the new battery being fitted and coded in to match the needs of the car`s on-board intelligent charging system, and being connected to it`s CTEK when the car was not in use, the battery failed while out for a drive, having started the car without issue and all systems in use functioning as expected till I parked and switched the engine off for perhaps 10 mins or so, after which it failed to start providing ALL the signs of a flat battery.

Being a high tec digitally controlled vehicle, the dash came up with a plethora of alarms once the battery recovered some voltage when the key was released and sprung back to the ign on.. Unusually the battery recovered to some extent on the circa 20 mile drive home, even once safe in the garage It fired up as normal, having benefitted from being charged by the alternator. I did not connect the CTEK in order to test if it would start the following day, which it did, I tried a couple of days later and again it started without issue....???

As I have no real experience of working on digital cars, I booked it in with an independent specialist, The day before the appointment I reconnected the CTEK to the car to be as sure as I might, that the car would start on the day to allow me to drive it to the specialist some 20 miles distant.... Initial inspection suggested that the battery was undercharging according to the dash voltage read out, Battery removed from the car and tested showing 12. 4 volts, when load tested it failed...the voltage dropping rapidly....Battery replaced with a new one and coded in.

I must have maintained and replaced literally hundreds of non AGM batteries, over a period of decades, in all types of installations, though never came across one that acted as this AGM battery seems to have done.

Had I access to a code reader with the ability to re-set systems after battery removal/replacement, I would have carried out tests on the battery myself, but without that and the confidence that after battery removal and replacement that the digital systems might hopefully come back on line, I preferred to leave it to someone who has expertise in such processes....However I will still be driving with my fingers crossed for some time to come, having spent years solving communication issues between all sorts of digital nodes required to operate all sorts of digitally operated and controlled machines and kit...
I will also follow the "destructions" in the CTEK manual more carefully too..

Hope this ramble proves worth something to someone at some time... More than happy to be picked up on anything I have typed that might be inaccurate..

BTW, I suspect the EV discussion on the requirement to derive a lower control voltage being supplied by an old style circa 12 volt battery, as opposed to just tapping the required and lower control voltage, may be related to maintaining balanced usage and recharging across the high voltage battery group...?

A point rarely discussed when considering a batteries quoted capacity, usually in amp hours for any nominal voltage, is the Peukert effect. He discovered the rate of discharge impacts greatly the quoted capacity, maintained high discharge currents leaving a battery below the working voltage range of any load its supplying before the full capacity has been depleted. A simple explanation is that batteries provide chemical storage of electrical energy. When asked to release this energy there is a limitation on how quickly the chemical energy can be released as electrical. Consequently battery capacity is usually quoted at the 20 hour rate such that, for example, a 100 amp hour battery will provide a load of 5 amps for 20 hours (C/20) before being below the fully discharged voltage. Considerably less time if the load was increased to say 50 amps (C/2) and conversely exceed the quoted capacity for very light loads. This also explains why a lead acid battery can recover a little after a heavy discharge as chemical energy remains.

Peukert determined a mathematical law to calculate this effect of load v discharge time with an exponent of 1 for the perfect battery ranging to 1.35. Lead/acid flooded cell around 1.2 and AGM/gel a little higher. LiFePO4 batteries fair the best at 1.01 to 1.05 allowing intermittent very high discharge rates on EV's with little impact on capacity. The latter can also be safely charged at much higher rates as well although the Peukert effect relates to discharge only.

I used to use CTEK chargers, but lost faith with them 10 years ago, after having multiple failures across three different models. I switched to the Optimate chargers and use them ( different models ) on the bikes, garden tractor, Volvo and the Plus Six. The chargers are specific to the type of battery fitted. So far no issues, but I am not a battery expert in any way, so maybe I have just been lucky with them. The issue of the "modern" 12v car battery types failing suddenly is always at the back of my mind though. Our Plus Six is coming up to six yrs old, so I think this winter its due a new battery. The original fitted is a Yuasa, so do I change brands or keep to the original??.