Battery heating and insulation

If it becomes cold, the performance of the lead batteries diminishes sharply. If the fact that vehicle drives little and is in the free one is probably not very large the joy. At appropriate temperatures the range can sag fast to only 10 km. If the batteries anyway already diminished in capacity, the range drops so far, so fast, you may not be able to get home from the office.

Here again is a point where improvements in the vehicle in needed.






100Ah Batterie The amp-hour capacity of the lead battery becomes with cold weather ever fewer. The lead battery can let the chemical processes run at low temperatures only slowly and no longer completely.

The only remedy is a higher battery temperature.


Temperature monitoring

Around the battery temperature to display there are simple coolant temperature gauge.

Here in the picture on the right is a thermometer with two measuring points (battery / interior) as well as a clock to the left, nicely backlit and supplied via the 12Volt network. (this is extra, added equipment - RRY)

In addition, there are devices with battery operation and for the assembly with adhesive strips. If one installs the thermometer on the left side of the seat, one can lead the cable above the engine cover into the engine compartment. This may not be the cleanest installation, but the technically impaired can quickly manage it.

Battery insulation

The first step to a higher battery temperature is the insulation of the batteries, since these are located completely unprotected in the engine compartment.

Careful battery insulation can be sufficient to hold battery temperature.

Air cushion foil

Bleibatterien im el

The simplest insulation method is packing up the batteries with air cushion foil. I think this packing material is well-known - the small burls between the fingers slam so beautifully.

Ok, this one time we need the foil with the burls still intact. This material is durable and easy to install. If you don't want to install battery heating, installing the foil is quite easy, and may be sufficient to give good range in cold weather.


The whole represents now a minimum solution.

Polystyrene Sandwich

One can improve the insulation under the batteries by better using a better material. For this a sandwich construction from an aluminum plate (down) and a polystyrene layer (above) offers itself. The whole " insulation-sandwich" can one also directly also into the air cushion foil pack up. Unfortunately the polystyrene resolves itself during contact with the battery acid into its constituents - therefore one should watch out there that no acid comes to the insulation.

Engine compartment insulation

A surely good idea is to insulate the whole engine compartment. The waste heat of the motor helps to heat the whole motor compartment.

To the insulation a very strong foil or a plastic plate from under the driver's seat to under the engine compartment is recommended to fit. Is important to leave blank the belt drive since this moves on starting longitudinally and also laterally. The insulation of the side panels can take place inside in the battery trays likewise with a foil, recesses likewise around the axle. I did not practice this solution yet. At the vehicle at which I saw this, it gave problems, the foil in some places had torn - here still your development is in demand -

The insulation must be removed for the summer, since otherwise probably the engine overheats.

Battery heating

Often the insulation is not sufficient, therefore the heating be fitted, but there are several possibilities.

With all possibilities it must is noted that the batteries are heated evenly. The coldest battery dies first.

Hand lamp cable

Hand lamp cable?? 8W hand lights is well-known for auto repair. With some of these lights the so-called fluorescent lamp ballast is replaced by a resistance cable. One detects the this type of light by the fact that the cable in operation becomes warm.

Here one can remove the light and short circuit the cable at the end. Thus one has a quite good heating cable with approx. 50Watt amount of heat. The cable could be stuck now under / on the battery.

Caution: There is possible after some time for the cable insulation to abrade, thus develops a connection between the cable and battery basket. I.e. the vehicle, or the metallic sections, can assume in the most unfavorable case 230V mains voltage (in europe, us Yanks will only receive a 110V shock - RRY)! I am aware of several cases where this already occurred - deadly danger -. Best you forget this solution - I mention it here only to give you better ideas.

Original Battery Heating System

From Citycom there is battery heating installation kit custom-made for el. To my knowledge the heating kit fits only the 90Ah batteries, since there are otherwise problems in the height. In my " professional career " I installed this heating only once, as far as I still remember, the installation was relatively complex, but the construction was durable. Who orders today City el, I can heartily recommend the heating kit. The longer battery life and the possibility also with large cold weather to drive counterbalance the additional price.

Do It Yourself Battery Heating

If you have the time, you can build your own battery heating. Basic element of the heating are self adhesive heating foils 12V ┴ of the company Conrad (catalog 98 page 816 Best No. 532886-44 price 12,50DM with 3 pieces).


One can stick the foil directly laterally on the battery, with the leads out. The solder tacks of the connection points at the foil are important and need to be protected. These points are exposed and can be scrubbed off possibly

Alternatively one can build a " heatsandwich ".

2-3 mm aluminum Plate for the base - Insulation - about . 5mm polystyrene - then 0,5 - 1 mm aluminum plate with the foil underneath. Stick it all together at the edges with silicon sealer

You must consider the overall height in the battery compartment. In the case of the 100Ah batteries, this sandwich does not fit. This construction can be applied also to other electric vehicles.


Current supply:

36Volt Direct

An obvious solution is the direct current supply from the battery power set. All foils have 12Volt like the appropriate batteries. Thus all foils into series switched and to the battery - here the question arises whether it is worthwhile to preheat the batteries from the own energy, if one does not have a line voltage. The response is - the used up energy, with good Insulation, is smaller than the energy released by the higher temperature.

Electric circuit security:

The electric circuit with glass fuses 6x30mm secure. No autoflat protections - no 5x20mm glass protections - no automatic circuit breakers 12 or 230Volt - nothing else functions reliably! Fuse both the plus - and the minus pole! (I'm not totally sure of the meaning of this important safety message, I'll have to check it carefully with Ralf - RRY)

Temperature Regulation:

In order to keep at a moderate temperature all batteries evenly, it would be best to regulate each battery separately, in practice it is enough to have one thermostat for all batteries. Household thermostats or electronic thermostats (coupled with the temperature indication) can be used or. With 36V these thermostat contacts to switch does not function always, or requires a protective circuit of the contact.

Favored solution:

Temperature adjustment:

Depending upon desired road performance set the temperature from +10░C to approx. 20░C. The more higher the temperature the more " heating energy " one needs.

Good winter traveling!.

Die einfachste Isolationsmethode ist das Einpacken der Batterien mit Luftpolsterfolie. Ich denke dieses Verpackungsmaterial ist bekannt -

letzte ─nderung 12.09.99