# Series hybrid boat - batteries, voltages, PV and chargers



## Lomax (Aug 18, 2016)

Hi everyone,

I've been fantasising for some time about the possibility to convert a diesel powered boat into a series hybrid, using a diesel generator and a LiFePo battery pack connected to an electric car motor. It would be a semi stationary live-aboard, so run time requirements are pretty modest. I've based my calculations on a ~20kW AC motor, a ~20kWh battery pack, a ~6-7kW diesel generator and two ~3kW battery chargers. Most of the roof would be used for solar panels, with which to supplement the power from shore and generator, and I estimate I should be able to fit about 2kW worth of panels. Range would be limited by battery bank capacity as neither power source is able to power the motor indefinitely - the diesel generator being intended only as a range extender and as a means for charging the battery pack while stationary, should shore power not be available. If I can get a few hours runtime at modest speeds every three or four days that should be sufficient, and back-of-***-packet calculations seem to indicate this is quite doable, even when taking inefficiencies into account (80% DoD, 50% PV output 3h/day, 90% charger efficiency, etc). 

However, I've got a few question marks around the architecture, particularly with regards to the PV controllers. I've been unable to find a PV charger that can charge high-voltage battery packs, and I'm disappointed that I would have to have two separate sets of PV panels for charging the "house" (12 or 24 V) and "propulsion" (192 V) packs. It would be ideal if it was possible to separate the MPPT component from the DC/DC converters, so that two independent chargers at different voltages could be hung off the same PV array. Does anyone know of such a beast, or is this a hopeless dream? 

Edit: As an alternative, perhaps it would make more sense to have a single high-voltage battery pack, which is used for both propulsion and house consumption? I would still need to find a 192V PV charge controller though, and these have proven elusive... Or I could base the system on a 48V BLDC motor, and a 48V battery pack, but 20kW @ 48V = 400A  

Cheers, 

Lomax


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## major (Apr 4, 2008)

Nothing wrong with a 48 Volt system. Hopefully you'll get some useful discussion here. Welcome to this board.

major


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## Lomax (Aug 18, 2016)

Thank you very much! I have looked at some 48V motor options, and I've seen you can get them in quite high power, but the EV motor that first got me interested in the concept is a 25/90kW delivery vehicle motor from Huyndai - that's 25kW continuous and 90kW burst  A whole different beast to any 48V motor I've been able to find, and ideal for a displacement hulled barge where short bursts of power are often needed. I wouldn't feel safe manoeuvering without this reserve capacity. The 20kW figure is the minimum power required for cruise speed; useful for run-time calculations only. Typically you'd only move at maybe 1/4 of your hull speed or less (which is where the "couple of hours runtime on a 20kWh battery pack" estimate comes from). Not only for safety reasons, but accelerating a hull of this type carries an exponential energy cost and you save a significant amount of energy by moving slower - see graph below. Maybe 96V is a better compromise? There are some (very few) PV controllers which can handle this battery voltage.


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## Lomax (Aug 18, 2016)

Here are the specs of two of the motors I've been looking at:



```
Hyundai 25/90 EV motor
--------------------------
Type            3 phase AC
Cooling         Water
Controller      External
Peak kW           90 kW
Cont. kW          25 kW
Peak RPM        3500 rpm
Cont. RPM       1500 rpm
Voltage          208 V
Max current      335 A
Length            32 cm*
Diameter          27 cm*
Weight            85 kg*

*) Excluding gearbox
```


```
Elco EP-70:
--------------------------
Type            3 phase AC
Cooling         Water
Controller      Built in
Peak kW           51 kW
Cont. kW          30 kW
Peak RPM        2500 rpm
Cont. RPM       2000 rpm
Voltage          108 V
Max current      275 A
Length            89 cm
Width             48 cm
Height            49 cm
Weight           295 kg
```


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## Lomax (Aug 18, 2016)

I've just found the AERL CoolMax SR 45A SRHVW MPPT Charge Controller which can handle battery voltages from 48 to 132 V. Pricey, but looks like a serious piece of kit. With the Elco EP-70 motor way outside my price range @ $15k(!), does anyone have suggestions for cheaper motor options in a similar power range, with an operating voltage of 96 V?


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## Scooter M (Apr 16, 2014)

Lomax said:


> I've just found the AERL CoolMax SR 45A SRHVW MPPT Charge Controller which can handle battery voltages from 48 to 132 V. Pricey, but looks like a serious piece of kit. With the Elco EP-70 motor way outside my price range @ $15k(!), does anyone have suggestions for cheaper motor options in a similar power range, with an operating voltage of 96 V?


If you want to fabricate your own kit, HPEV's has the best marine EV motor I could find. I would get the AC34 with the Curtis 1238-7601 controller. This is an oil cooled motor that is built specifically for marine applications. Here is a link to one of their retailers:
http://www.evwest.com/catalog/produ...ucts_id=371&osCsid=bctnv2f79fsvlpn493366ss0q2
Here is a link to the Tesla battery modules they sell as well:
http://www.evwest.com/catalog/produ...ucts_id=329&osCsid=bctnv2f79fsvlpn493366ss0q2
I am using the dual version of the AC34 to power my 2016 Bayliner 175 speed boat. Here is a link to the build specs:
http://evalbum.com/5217
Here are some videos of the boat on the water:
https://www.youtube.com/watch?v=my0TX3INjSk
https://www.youtube.com/watch?v=BRqcp4Tzzrg
Mounts and a 2 to 1 gear reducer would need to be fabricated. The motor and controller is a third of the money and more powerful and durable. It's very well built.


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## Yabert (Feb 7, 2010)

Lomax
If you want to keep things simple with a 48v system, you can use two 48v motors (example) connected together with a single motor controller for both motor.
That can give you a more interesting 30-40 Kw peak and 15-20 Kw continuous.

It can be a lower cost alternative. If no, the HPEV suggested by scooter kit is hard to beat.


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## Lomax (Aug 18, 2016)

Thanks guys - the HPEV motors do indeed look great. I found this one particularly interesting, 72-108V, 48kW (65hp), corrosion resistant and water cooled (via heat exchanger): http://www.evwest.com/catalog/produ...ucts_id=371&osCsid=bctnv2f79fsvlpn493366ss0q2 Price is high though, so is the max RPM @ 10,000 - would need a 3:1 or greater gearing. 

Re. two motor option: whatever boat I'm likely to get it will probably have a singe prop, and changing from one to two propshafts is going to be way too expensive. If this is going to work I'd need to keep as much of the original transmission a possible.


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## prensel (Feb 21, 2010)

I have a complete 96V set for sale, comes out of a boat which was converted from diesel to hybrid.

http://www.diyelectriccar.com/forums/showthread.php/complete-96v-ac-set-motor-controller-175650.html

I'm located in Europe though....


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## Lomax (Aug 18, 2016)

prensel said:


> I have a complete 96V set for sale


 Interesting, thanks for replying! I'm still only in at the exploratory stage though, trying to determine whether something like this is doable, what the costs would be, what the critical parameters are and how such a system could be put together. It would be interesting to hear a bit about why this kit is for sale, where it came from and what lessons were learned - for example, was it removed to be replaced by a diesel engine, or a bigger electric motor?


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## Scooter M (Apr 16, 2014)

Lomax said:


> Thanks guys - the HPEV motors do indeed look great. I found this one particularly interesting, 72-108V, 48kW (65hp), corrosion resistant and water cooled (via heat exchanger): http://www.evwest.com/catalog/produ...ucts_id=371&osCsid=bctnv2f79fsvlpn493366ss0q2 Price is high though, so is the max RPM @ 10,000 - would need a 3:1 or greater gearing.
> 
> Re. two motor option: whatever boat I'm likely to get it will probably have a singe prop, and changing from one to two propshafts is going to be way too expensive. If this is going to work I'd need to keep as much of the original transmission a possible.


You would never spin the motor that quickly at 96V. Here is a power graph of where you would be typically running:
http://hpevs.com/Site/images/torque...mp imperial continuous oil cooled 6-23-15.pdf

The motor would typically spin around 3,000 RPM at that voltage.

When it was suggested that you use two smaller motors, the two motors would be coupled to a single shaft. Something like this:
http://i249.photobucket.com/albums/gg225/rebirthauto/Classic VW Twin Motor/DSCN1093.jpg


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## Lomax (Aug 18, 2016)

Scooter M said:


> You would never spin the motor that quickly at 96V. Here is a power graph of where you would be typically running:
> http://hpevs.com/Site/images/torque-curves/oil%20cooled/ac-3X/ac-34/Update/Imperial/96%20volt/AC-34%2096%20volt%20650%20amp%20imperial%20continuous%20oil%20cooled%206-23-15.pdf
> 
> The motor would typically spin around 3,000 RPM at that voltage.
> ...


Ah, great, that's very useful. I'd say for a propeller the size we're talking about (~70 cm dia), low RPMs at high torque is preferable to the other way around. I don't think you'd ever want a prop speed above 2k RPM, and typical cruising would be maybe max 800 RPM - so 3k RPM @ 2:1 would seem appropriate - though I stand to be corrected here! 

Two motors on one shaft is interesting, but that looks like some pretty expensive machining. By contrast, the 25/90 kW Huyndai I've been looking at has a fairly standard drive plate on its gearbox, which would couple straight on to the propshaft with just an anti-vibration coupling in between. I can buy this motor (used) with gearbox, dedicated 90 kW controller and four 3.3 kW Brusa chargers for just $2k - and all in good condition too. But yes, it wants 208 V.


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## Lomax (Aug 18, 2016)

Btw - here is a basic block diagram of my 192 V series hybrid / plug-in hybrid / PV EV boat thoughts.


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## Scooter M (Apr 16, 2014)

Lomax said:


> Ah, great, that's very useful. I'd say for a propeller the size we're talking about (~70 cm dia), low RPMs at high torque is preferable to the other way around. I don't think you'd ever want a prop speed above 2k RPM, and typical cruising would be maybe max 800 RPM - so 3k RPM @ 2:1 would seem appropriate - though I stand to be corrected here!
> 
> Two motors on one shaft is interesting, but that looks like some pretty expensive machining. By contrast, the 25/90 kW Huyndai I've been looking at has a fairly standard drive plate on its gearbox, which would couple straight on to the propshaft with just an anti-vibration coupling in between. I can buy this motor (used) with gearbox, dedicated 90 kW controller and four 3.3 kW Brusa chargers for just $2k - and all in good condition too. But yes, it wants 208 V.


Be careful with buying used motors and controllers from a vehicle. Most likely, it would require the controller to be reprogramed due to some auxiliary component that is no longer connected to the controller. Is there someone who has pulled one of these motors and controller and reconfigured it for a marine application?


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## Lomax (Aug 18, 2016)

Scooter M said:


> Is there someone who has pulled one of these motors and controller and reconfigured it for a marine application?


Yes. Not marine, but car. But TBH, it's the motor and the chargers that interest me the most - the open source inverter designed by Johannes Hübner has been used to run this motor, and doesn't cost all that much. But. It's 208 V. Even the compromise 192 V battery pack I imagined running it on is impossible to charge from solar. Not without going through some idiotic PV -> 48 V -> 240 V -> charger set-up. This is simply because there are no PV charge controllers available to us mere mortals that can handle a 192 V battery voltage.

Edit: Allegedly you can series up PWM PV charge controllers to reach your desired voltage - but again, huge inefficiencies in an already inefficient system.


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## prensel (Feb 21, 2010)

Lomax said:


> It would be interesting to hear a bit about why this kit is for sale, where it came from and what lessons were learned - for example, was it removed to be replaced by a diesel engine, or a bigger electric motor?


This kit was installed in a newly build boat by a professional shipyard/builder but the customer wasnt happy with it and wanted a bigger boat after just about 10 runs with it. So the boat went for sale but never got sold as it was hybrid. Theres was simply zero interest in it. 
Another shipyard bought it over after laying in the boathouse for over two years, replaced the EV kit with the original diesel engine and the boat was sold within a week. I think that says something about the acceptance of EV boating...

Regarding the kit: i took it over because it had over 100pcs of typically unused CALB cells which i could use. It was all build around expensive stuff but i did find some sloppy wiring in the BMS, dash, controls etc. I really think this was the main cause of 'problems' the original owner seemed had with it. "Sometimes it just didnt go" was told to me but no further details.

This EV kit was buildup around a 96V system, had an auto-start 20kW FisherPanda generator on board directly feeding 96DC to the pack in case the pack was nearing 50% empty. With or without sun or fully charged pack you could always go because of the powerfull generator.


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