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History of Messerschmitt electricalsystems: Early KR175 kick-starter modelswere fitted with a 6 volt 7 Ampere Hourbattery that was adequate until the laterversions were fitted with a wiper motor(replacing the hand operated wiper). Anupgrade was offered to 11Ah and Boschservice stations could uprate the magnetogenerator to ensure that sufficient charge wasmaintained under normal use. LaterKR175’s (version 2b) had a dynastarter with12 volt electrical systems that required asecond battery holder to accommodate a 6 volt11Ah battery that was connected in series withthe original 6 volt 11Ah battery on the otherside of the bulkhead.

Messerschmitt KR200’s built from 1955 to1958 were fitted with 2 x 6 volt 11 AmpereHour batteries connected in series to give

12volts. It was soon apparent that thesebatteries required a significant driving timeto recharge after starting the engine and therewere complaints about flat batteries –especially in winter when lights were used.Unlike modern cars, the Messerschmittdynastart has a very limited capacityproducing a maximum 11 amps with a limitedshort term output of 135 watts. Almost all

British versions had Exide 6v motorcyclebatteries. It is possible to find small batteriesof the original size at many motorcycledealers.

Messerschmitt KR200’s built from 1958 to1964, were fitted with a larger battery of 13or 14 Ah with a larger battery tray. For the

U.K. market, where the cars were deliveredwithout batteries, a 12v Exide 14Ah batterywas fitted. Both U.K. market and Europeanversions had a Bakelite cover fitted over thecell vent plugs and a retainer strap wassecured with a 6mm screw making a very neatinstallation. This cover was essential for someBosch and Varta batteries that had exposedmetal links between each cell. FMR offered aconversion kit for the earlier battery tray butit required a new ‘Black Box’ cover that wasspecially made by FMR. Part of the old batterytray was ground off and the new larger traywas welded on top thus reducing the clearancebetween battery and ‘Black Box’ cover.

Restoration of the battery tray. Partsmartoffers a new battery tray to the later design,(Part Number 1393 battery tray and strap),that can be fitted (welded) to the earlier engineframe. Unlike the FMR conversion, this is a

Messerschmitt batteries – size, type and technical explanationby David Garner

Early battery tray

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new tray with support brackets to the samedesign as the later tray and the old tray isremoved completely. Many are severelycorroded from acid spillage so it is worthwhilereplacing the entire tray during a restoration.

Modifying the early battery tray to fit alarger battery. It might be difficult to findthe small batteries for the early tray or youmay find the reduced capacity and short lifea nuisance. It is possible to fit a larger battery

by bending the sides of the original tray asshown in the photo. You may need to cushionthe sharp edge under the battery with a pieceof rubber or other similar material.

Why fit a larger battery? Starting currentfor a cold engine is around 60 Amps and thatis nearing the limit for the smaller 11Ahbattery. A new battery will provide thenecessary power but as it reaches 2 or 3 yearsold it becomes less efficient. Recent advancesin battery technology and the widespread useof golf carts and mobility scooters have madea large range of powerful and compactbatteries available. In this application, it isexpected that the battery may become totallydischarged – to a point where a normal (oldtechnology), battery would be damaged andthey are thus known as Deep Cycle batteries.They are also known as VRLA batteries,(valve-regulated lead-acid battery), since theyare sealed and maintenance free. Their sealed

for life construction enables mounting in anyorientation and maintenance is much reduced.Most batteries used in golf carts and mobilityscooters are AGM (absorbed glass mat)batteries types and feature fiberglass meshbetween the battery plates which serves tocontain the electrolyte. AGM batteries differfrom flooded lead acid batteries in that theelectrolyte is held in the glass mats, as opposedto freely flooding the plates. These batteries aretotally sealed and cannot spill acid.

Will my Dynastart charge a larger battery?Imagine the battery is a water tank filled by asmall tap (representing the limitedMesserschmitt charging system). An 11Ahbattery will be significantly discharged bystarting the engine but will re-charge quicker,(imagine filling a small tank). There is littleor no reserve capacity especially if lights areused. With a larger battery, (imagine a largetank), there is a large reserve capacity andeven if the car is not driven any distance afterstarting, there are still many starting cyclesavailable. A current / voltage regulatorrestricts the output of the dynastart to amaximum 135Watts with a 90Wattcontinuous rating. This is just enough topower the lights leaving hardly any power forcharging. Old technology Lead Acid batterieshave a significantly shortened life if they areregularly discharged to 50% capacity or lessand that is why the 11Ah battery is not entirely

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suitable for a Messerschmitt.

Deep Cycle battery used in engine starting:Many battery suppliers will advise that DeepCycle batteries cannot be used in startingapplications. The plate construction meansthat they cannot supply the very high startingamps of a lead-acid battery of the same Ahrating. However, if the battery is de-rated(larger Ah rating than required), then it willgive years of useful life. A 33Ah battery hassignificant reserve capacity – a useful featureon a Messerschmitt where it is possible todrive many hours if the dynastart chargingfails when you are on a long journey. Thesebatteries are also suitable for the Tg500.

Battery life: With 47 years of Messerschmittdriving including years of daily use, I had onlybad experiences with old technology lead-acidbatteries and it was rare to have one lastlonger than 3 years. Messerschmitts todayspend many months unused and withoutregular charging, water level top-up, andcleaning, old type batteries would not last oneseason. Compare that with a Deep Cyclebattery that will often last 12 months betweeneach use with no maintenance or charging!While this is not ideal, I have batteries morethan 10 years old that have survived thistreatment.

Maximum battery dimensions: To fit in thebattery tray area, the maximum size is Length195mm, Width, 130mm, Height, 155mm.This will allow the original battery retainingstrap to be used and, more importantly, the‘black box’ cover can be fitted. However, theoriginal tray is 190mm long and must bemodified slightly to accommodate the longerlength (see photo). Make sure the positiveterminal cannot touch any part of the metalframe as a short circuit will cause damage tothe battery and is a fire risk.

Where to buy a battery: Most battery dealerswill stock lawn tractor batteries that areconventional lead-acid types (also availablein the USA and Canada at most Wal-Martstores). It is possible to find small batteries ofthe original (1955-58) size at manymotorcycle dealers. Mobility scooter and golfcart batteries are widely available on Ebaythroughout the world and, because they aretotally sealed, can be sent by mail order. 33Ampere hour sizes are widely available butmake sure they do not exceed Length 195mm,Width, 130mm, Height, 155mm.

Protect your Messerschmitt from anelectrical fire: The main power circuit to theheadlight switch, dip-switch, and ignitionswitch does not have any fuse. If there is ashort circuit a fire is very likely and at leastone Messerschmitt has been totally destroyedfrom this cause. Partsmart formerly offeredan in line fuse of 30 amps rating to protectthis circuit. To fit a supplementary fuse,simply disconnect the large red wire from theterminal strip located at the rear bulkhead,insert one wire of the fuse-holder into thevacant terminal and re-connect the red wireto the fuse holder with a screw connector.

Look on EBay for 20/30A In Line StandardSplash / Waterproof Blade Fuse Holder.

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We are very fortunate that the KR200 electrical systems are built to the highest standardsand are a credit to the original designer. In this case it was probably not Fend although thedesign and protection systems suggest the work of an aircraft engineer. Even the KR175 iswired to the best available technology of the day and this must have added some additionalcosts. Fortunately, when FMR took over from RSM in 1957, there was no attempt to reducecosts by skimping on the electrical system. With the exception of sheathing colour and fullsheathing through the chassis tube, the wiring remained the same right up to the last vehicleproduced during 1964. Many of the original wiring assemblies are still in excellent conditionand restorers usually only need to replace the wiring if the car has been stored in a corrosiveatmosphere for years. Each circuit is numerically coded according to German vehicle electricalstandards and the same system is still in use in today’s German cars. Messerschmitt (German)colour codes are also still in use today except for the earth (ground) wire where brown hasbecome the new standard.

For almost three years, Ian Hopkins has been making the wiring harnesses/looms for MOC.Although more widely known in the automotive industry as a “wiring harness”, the term“wiring loom” is also used. Previously, most wiring looms were put away and forgotten, asbeing too difficult to fit. New harnesses/looms now come with the following features:-· All correct colour wiring.· Original type protective sleeving, wires cut to length, soldered ends, fittings for ignition

switch and wiper motor, with front screw connector block fitted and wired.· Comprehensive fitting instructions, rubber grommets, a fitted, modified (with the correct

bus links), fuse box, with fuses, to complete the package.Ian has tried to do as much as possible to prevent mistakes in re-wiring the Messerschmitt.Please also refer to July/August Kabinews for details on the main fuse that will protect theunfused part of the electrical system. Now you can protect your newly painted Messerschmittwith a new loom, which looks just like the original! Available from Partsmart, part no.1571complete wiring harness (UK spec) - £91.07.

A full colour wiring diagram is available free to download on:- www.messerschmitt.co.uk/index.php/downloads/category/10-technical#If you have a standard or colour printer you can make a large composite drawing and tape ittogether. Ideally you should download Adobe Acrobat reader (this is normally freeware). Afteryou choose print from the windows file menu you should get a properties page that allows youto format the file. Look for a section that says page handling and click on the drop downwindow that says Page Scaling then click the tile option. Change your zoom until you get thesize output you want, 200% gives you 8 pages (for USA/Canada) making the final chart 22"x 34" then simply choose Print. You might use heavier paper stock and tape the sheets togetherfrom the back using 2" (50mm) packaging tape. When you are all done it should fold neatlyinto a standard typing (USA/Canada) paper page. (In Europe, A4 paper @ 200%, output willbe 9 pages about the same size).

Messerschmitt Wiringby Ian Hopkins & David Garner