Does the voltage drop at cranking affect the lift kit?
Battery voltage dips briefly at cranking; on a sound battery it should not fall below 10.5 V. With deep collapses, use the kit after the engine starts.
At cranking the battery terminal voltage falls briefly; on a sound battery this value should typically not drop below 10.5 V, and anything above 11 V is regarded as good. Values falling to 8-9 V and below point to a problem with the battery, the wiring, the ground or the starter motor. With collapses this deep, lift kits running on 12V should not be used while the engine is being cranked; the kit should only be brought into use once the engine is running.
How the measurement is made
Connect the multimeter directly to the battery terminals, leave it on the voltage range and watch the lowest value on the display while the starter is turning. Measuring the resting voltage alone is misleading: a weak battery can look fine until it comes under load. Taking the measurement from the terminal post itself rather than from the clamp matters too; an oxidised clamp hides part of the drop. The detail of the method is under the voltage drop test with a multimeter.
If you are taking the measurement on your own, fix the multimeter to the terminals and set it at an angle where you can see the display; trying to watch the screen while turning the starter is both dangerous and misleading. If your instrument has a range that holds the lowest value in memory, use it.
What the value you read means
| Lowest value while cranking | Interpretation | What to do |
|---|---|---|
| 11 V and above | Battery and starter circuit in good condition | Nothing further needed |
| 10.5-11 V | Borderline; the battery may have aged | Clean the chassis and terminal connections and keep an eye on it |
| Below 10.5 V, particularly 8-9 V | There is a problem in the system | The battery, the heavy cables, the chassis connection and the starter motor need looking at |
Some of the low readings come not from the battery but from the return path. The symptoms of a poor chassis connection are collected under the symptoms of poor grounding; lights dimming heavily at cranking and the starter motor turning sluggishly come first.
Rules to follow in practice
- Do not press the switch of the kit at the same moment as the starter.
- Do not use the kit over and over with the engine stopped; the LFT20 draws 10A on average and tires the battery quickly. The subject is also dealt with under the battery consumption of the kit.
- On a weak battery the mechanism moves slowly; that is a supply problem, not a kit fault. Check the battery and the chassis connections first.
- The voltage surge that comes right after cranking is a separate matter; load dump is a risk in the opposite direction to a collapse.
What this measurement does not show
The collapse at cranking shows not the capacity of the battery but its ability to deliver load at that moment. A new but flat battery reads low as well; the measurement has to be repeated after charging. Values dropping somewhat in cold weather is expected too, and on its own that does not mean a fault. Repeating the measurement on the same tractor under similar conditions and looking at the trend is more meaningful than a single reading. Long cranking attempts one after another drag the value down as well; leave the battery time to recover between measurements.
What to do in practice
At the start of the season, measure the lowest value at cranking once and note it down; that becomes your reference for later complaints. If the value is borderline, clean the terminal posts and the chassis point first and repeat the measurement. An unhealthy charging or battery system is the most frequent cause of a wrong diagnosis: confirm the supply before you hold the kit responsible.
The full topic: Converting a tractor hydraulic lever to electronic control