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On summer holiday with electric motor and battery from Impulse Power - 150 NM with EL and Sail!


In recent years, Impulse Power has developed motors and batteries for marine and stationary use. For this year's season, the portfolio has been further strengthened with, among other things, larger batteries and power electronics for fast charging and offshore alternating current (AC) from batteries. These are products that we ourselves as sailors feel we need, and we wanted to test this in practical use. What is not more natural than sailing down the coastline and seeing how this works. One thing is range, how far do you actually get, what speed does the boat get with different energy consumption? Another thing is charging in practice, do you find electricity, how long does it take, do we do a trickle charge or should we fully charge?

Test criteria

To find answers to these (for electric boat people!) important questions, we set ourselves a long test. One of Impulse Power's test boats is located at Lille Herberen (Bygdøy Oslo). It is an Elvstrøm 717, "The Raft". The boat was designed by sailor Paul Elvstrøm in 1976 and more than 50 boats were built. The waterline on this boat is 19.5 feet. That means a theoretical speed of √19.5 x 1.34 = 5.91 given that the boat is not planing. It is an easy boat to drive. We have previously seen speed as below:


Power kW   Speed kn

     1    _cc781905-5cde-3194- bb3b-136bad5cf58d_      3,6

     1,5    _cc781905-5cde- 3194-bb3b-136bad5cf58d_   4.3

     ​2  _cc781905-5cde-3194-bb3b -136bad5cf58d_        4,9​

     2,5    _cc781905-5cde- 3194-bb3b-136bad5cf58d_   5.3

     3    _cc781905-5cde-3194- bb3b-136bad5cf58d_      5,67

Theoretical ranges on pure engine driving then become:

1 kW (approx. 20 A) = max 12 hours      43 nm

2 kW (approx. 40 A) = max. 6 hours

3 kW (approx. 60 A) = max 4 hours


Mao speed costs, ref the formula above. The aim is to manage a test stretch of 40 nm!


The Raft" has been equipped with the following products, all from Impulse Power:


  • Driveline: Impulse 5 – i.e. an outboard 3 kW motor

  • Battery: Impulse 9 kWh & Impulse 3 kWh

  • ImpVerter: 3kW AC 230 & 2.4 DC AC charging



In addition, we have a victron DC/DC converter for supplying 12v to chartplotters. We are now developing a 12v outlet in our ImpVerter for future deliveries. The two batteries can be connected in parallel and together deliver 12 kWh on this boat, or run separately. It is possible with a maximum of 4 batteries together - so in theory 36 kWh if there is a large need for electricity. The "ImpVerter" is connected to one of the battery's two connectors and will charge the entire system when connected to the mains (mains), at the same time that it supplies 230 VAC from the battery when we are out sailing. In theory, we will be able to drive on the engine at 4 knots for 10 hours and have a 40 NM range in pure engine operation (without sail). At the same time, a sail can also significantly reduce the power requirement and increase speed. This was used during the test to save time.  


Day 1

We left Oslo at 11:30 a.m. July 13. The tide would turn inward in the 12 draft, and we would sail directly against the current and that would cost time/speed. Furthermore, heavy rain, lightning and wind were reported, but this was our last chance to get out, so we chose to sail. The idea was to stay at 1 kW and be able to drive in theory for 10 – 12 hours, as well as possibly supplementing with sails if necessary, and that would come in handy here..


The river current is a handful to sail solo. It has a tiller without an autopilot that requires a man, bilge tackle that must be prioritized in the event of a blow, as well as a genoa winch. Impuls Power's emissary was alone on this trip. Given that the priority was to test the powertrain on this trip, the sailing was put on the back burner.  However, due to counter currents and low speed over land, as well as  laws about cold beer all the way down in Resø, the genoa was made ready for supplementary speed. But first we had to brave the expected bad weather... Heavy thunder and lightning came in from the west and the LiveLightning app was frequently used. We also went close to Nesodden in the hope of some protection. The strong wind really took hold of the boat and it was choppy, and speed was only slightly above 3 knots. The heavy rain cooled down the crew and motivation. 

An hour of rain and wind was reported, and here YR was right. By 2 p.m. it was all over and we hoisted the Genoa and sped into Drøbak. Here we made an ice cream stop and picked up some young people who joined us on the trip. We put the boat on charge for 30 minutes and thus supplemented some power for the battery. From here we continued with genoa and motor (1 kw power) until Son, which we arrived at 20:00.

Unfortunately, we had PC issues this day and could not log consumption and data from BMS. We had about 40% left on the largest package, albeit with 30 minutes of charging with 2.4 kW power from Impvertern in Drøbak. Distance was 26 nm, 


we left Oslo at 11:30 and arrived in Son at 19:45 - minus 1 hour in Drøbak, the sailing time was about 7:45 min - the speed must have been somewhat below 4 knots.  Son Marina was the night's accommodation and one of the boat's eminent 4 berths was used. The reserve crew was sent home after a burger and beer 😊. 

Day 2

The PC was replaced and we could finally log in. Both batteries were fully charged during the evening using the ImpVerter, which otherwise worked brilliantly throughout the trip. Really useful to be able to charge in a few hours. If the crew could bear it, we could sail on at 23:00. But we chose sleep and started the next day at exactly 09:00 with 97% on the battery.  The aim was to get to Hankø at least, maybe Koster. As on day 1, we were lucky with the wind direction, north, and this day there was no rain in the forecast, but some wind throughout the afternoon.

PC LOG was started and logging started. This is super exciting for the nerds 😊. Here we can see power consumption over time, temperature, voltage etc. This will eventually appear in the Impulse Powers APP, but for now only a sneak view.... In the picture on the left you can see the State of charge (how many % of max is on the battery, Voltage in Volts and Pack Current, i.e. how much power and hence power we took out). Current x Voltage = Power (measured in e.g. kW)

significant speed increase. You can see this on the curve, which varies from 5 A at the lowest to 30 A (ie roughly calculated 250 W to 1.5 kW. It went quickly and nicely to Hvaler, outside Søstrene a lot of sea came in from the southwest after the wind had turned , and it got hectic in such a small boat. We took in behind Åkerø in order to get into cleaner water, and from here we motored alone. We kept such a good speed that we got all the way to Resø on only one battery with a little support from sail, and arrived at Resø at 21:00. We also managed great pizza at Lexø just before the kitchen closed.

Then we had 4% SOC on the large (9 kWh) battery. We had drawn 30% of the small amount (3kWh) - approximately 80 – 100 W per hour for the PC and various consumption. The trip was a total of 49 NM over 12 hours. Minus a little break, it gave an average speed of about 4.3 knots, 1.5 knots below the boat's maximum speed. almost the entire trip was with the engine on and with support from the genoa + exceptionally a mainsail for a little while before it became too much for a single trader on this boat.

It was an eventful day. Good speed south with the wind at your back often gave a speed of over 5 knots. If you look at the log, the effect (Pack Current) is at different levels. The day before we were at 1 kW. It is the same as 20A x with 50 V = 1000 W. We chose to vary the load according to wind and speed. As we wrote at the beginning, the boat's speed is never faster than 5.9 knots (unless it is planning). That's why we turned down the power so as not to waste energy that gives no benefit 

The conclusion here is that you can

come FAR but

power motor must be adapted and used smartly.  


The return went after a few days accordingly. The route shown below. Resø – Skjæløy without a log this time. The trip is shorter, and there was a bit more sailing. About. 30% remaining battery on arrival. The night was taken in Skjeløy for two shorter stretches – Skjeløy Son, and Son Lille Herberen over two days


Total sailed – 150 NM

Estimated power used:

  • Day 1 – Lille Herberen – Son – about 75% of 9 kWh                   kWh used

  • Day 2 – Son – Travel- 91% of 9 kWh + 30% of 3 kWh     _cc781905-5cde-3194-bb3b-136bad5cf58d-3194c9-0 _cc785 bb3b-136bad5cf58d_   9.19 kWh used

  • Dag 3 – Resø- Skjæløy – 60 % av 9kWh        _cc781905-5cde- 3194-bb3b-136bad5cf58d_                     _cc781905-5cde-3194 -bb3b-136bad5cf58d_ 5.40 kWh used

  • Dag 4/5  Hjem- ca 100% av 9 kWh –      _cc781905- 5cde-3194-bb3b-136bad5cf58d_         _cc781905-5cde-3194-bb3b -136bad5cf58d_           _cc781905-5cde -3194-bb3b-136bad5cf58d_        9,00 kWh brukt

Total energy consumption approx. 30 kWh, the cost of half a pint 😊. However, with the help of the genoa, but with the engine on 90% of the time at varying speeds.

This was a good test of a practical sailing summer. Pure electric operation at full speed as if driving with a diesel will shorten the distances, but it is possible with charging with usable power as our ImpVerter provides. Furthermore, the range will be significantly longer if the speed is lowered 1 - 2 knots from the max. This can be retrieved with a support sail as we did here.

3kW power on this engine was sufficient even in a bit of wind with this boat

It was not regenerated on this trip.

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