Battery for electric outboard

[Cloven]

Neck on the block time!!

I am considering getting an electric outboard for a small dinghy just to get it out of a very sheltered bay and then if the wind completely dies. Inland lake so no issue of tides etc. I have an almost new Red Flash battery which I bought to use for an electric windlass project that never happened.

Advantage is that the battery is very light but what is the worst that can happen? Will the battery simply give up the ghost after a few minutes of use or what? Or should I sell it and get the proper deep cycle battery that is recommended?

Any thoughts gratefully received.

 

[pvb]

Ordinary electric outboards use a huge current, so you need a high-capacity battery if you're going to get any sensible use out of the outboard. That means looking for high Ah ratings. Red Flash batteries are useful for some purposes, but don't have high Ah ratings, so won't be suitable for your needs.

 

[VicS]

Ordinary electric outboards use a huge current, so you need a high-capacity battery if you're going to get any sensible use out of the outboard. That means looking for high Ah ratings. Red Flash batteries are useful for some purposes, but don't have high Ah ratings, so won't be suitable for your needs.

In addition to the Redflash high rate batteries we might consider for engine starting there are also Redflash deep discharge batteries http://www.dmstech.co.uk/red-flash/red-flash-deep-cycle/ with capacities up to 260Ah.

These might be more suitable but I would think any traction battery would fit the bill.

 

[pvb]

In addition to the Redflash high rate batteries we might consider for engine starting there are also Redflash deep discharge batteries http://www.dmstech.co.uk/red-flash/red-flash-deep-cycle/ with capacities up to 260Ah.

These might be more suitable but I would think any traction battery would fit the bill.

The larger Redflash batteries tend to be rather more expensive than similar capacity AGMs from other brands.

 

[Cloven]

Thanks both for your comments. Kind of knew what the answers would be but just wondered all the same.

Dave

 

[pvb]

Worth getting a sealed battery - the possibility of spilling electrolyte in a dinghy is to be avoided at all costs!

 

[Cloven]

Worth getting a sealed battery - the possibility of spilling electrolyte in a dinghy is to be avoided at all costs!

Already got two of those on the big boat. May just get new ones for that and keep the older ones for the dinghy for all the use they are going to get.

 

[ningcompoop]

I used to use a 36lb thrust electric outboard to push a 15', 500kg trailer-sailor about on Windermere. I used a 24Ah "deep-cycle" scooter battery (about £50), this was left on the boat and kept charged with a 10w solar panel via a controller. At full tilt it would (theoretically) only last about 15-20 mins before the battery would be done for, but using it on a low setting, making about 3-4 kmh, it would run for a couple of hours, no problem. With a smaller boat you could get by with smaller motor and (slightly) smaller battery, as long as were happy with your restricted speed and range.

 

[Cloven]

I used to use a 36lb thrust electric outboard to push a 15', 500kg trailer-sailor about on Windermere. I used a 24Ah "deep-cycle" scooter battery (about £50), this was left on the boat and kept charged with a 10w solar panel via a controller. At full tilt it would (theoretically) only last about 15-20 mins before the battery would be done for, but using it on a low setting, making about 3-4 kmh, it would run for a couple of hours, no problem. With a smaller boat you could get by with smaller motor and (slightly) smaller battery, as long as were happy with your restricted speed and range.

Thanks for that, good to hear from someone who has actually used one of these. I have been looking at batteries for mobility scooters. They seem well priced compared to say those specified for golf carts.

 

[annageek]

Neck on the block time!!

I am considering getting an electric outboard for a small dinghy just to get it out of a very sheltered bay and then if the wind completely dies. Inland lake so no issue of tides etc. I have an almost new Red Flash battery which I bought to use for an electric windlass project that never happened.

Advantage is that the battery is very light but what is the worst that can happen? Will the battery simply give up the ghost after a few minutes of use or what? Or should I sell it and get the proper deep cycle battery that is recommended?

Any thoughts gratefully received.

Which Red Flash battery is it (I know DMS's battery ranges very, very well - if you get me)? Which electric outboard are you looking at?

 

[Cloven]

Which Red Flash battery is it (I know DMS's battery ranges very, very well - if you get me)? Which electric outboard are you looking at?

Battery I have is a Red Flash 1100, engine I am currently looking at is a Watersnake Tracer 54lbs thrust

Would appreciate your comments.

 

[annageek]

Its late, and I have a lot of wine in me at the moment, but I'll have a go...

Despite being a 43Ah rated battery (at a 10 hour rate), from my very hazy memory, you'd only get around 30Ah down to 100% depth of discharge (DOD) at about a 1 hour rate. It has fairly thin plates (to get the low internal impedance = high pulse current), so if you start taking it to really low DODs, you'll reach the end of the battery life pretty quickly. I doubt we have much in the way of expected lifespans for this battery at anything other than typical engine start discharge profiles, so its hard to estimate. I probably wouldn't want to be intending to go lower than 50% DOD though if I could help it - I would be very surprised if you saw fewer than 200 cycles at this discharge profile... probably a fair few more.

The E-outboard you mentioned claims a maximum discharge of 50A. Not sure if this is a short term peak or a continuous 100% throttle load... though I'll guess at the latter. Being quite a small motor, even on a small dinghy, I'd imagine you'll end up using it close to 100% throttle most of the time anyway. So, we have an effective 34Ah, and only want to use 50% at around 50A. That gives something like 20 minutes use of the motor. If was just a case of a quick hop from shore to your boat and back, then it'd probably be a nice idea, but by the sounds, you may need a bit more than that?

If you've got not other use, and 20 minutes of use sounds OK, then I'd go for it, but if not, I'd plump for a more suitable deep cycle battery. If you do end up using it though, then be sure to treat it nicely when recharging (proper 3-stage charging) and whatever you do, don't over discharge - if you get it 100% flat, don't expect it to be anything more than a really effective door stop!

In general, high rate batteries have thick lead work (for the inter-cell and cell-to-terminal straps) and lots of thin lead plates in each cell, leading to lower internal resistance. Deep cycles on the other hand usually have fewer, thicker plates. This gives them a higher internal resistance, but makes them more tolerant to abuse / deeper discharge. That said, the chemistry is normally exactly the same, and so either battery can theoretically be used in either application... a bit like using a sledge hammer to tap in a panel pin - it just about works, it's just not optimised for the task and you end up not taking advantage of the sledge hammer's key attribute of its weight. (Crappy analogy - sorry!).

Hmmm... Valentines evening, and I'm on a forum talking about batteries - I expect my boyfriend is regretting not getting me anything for valentines day now

Anyway, hope that helps.

 

[Cloven]

Annageek, Thanks for the very comprehensive reply. Best summarised I think as - yes it will work but not very well and not for very long. So, plan B I think

 

[ianfr]

I bought a Bison 40lbs electric motor last year, on a Seago Ranger 2.7m dinghy with 2 adults and a dog, using a 17.2Ah emergency start pack, the motor ran for 55 minutes before the battery gave out. Most of this was done at about 2/3 throttle with bursts of full power. Near the end, we added a Suzuki 2.5hp 4 stroke outboard as cargo, and motored against the ebb tide at better than walking pace. Dropped the Suzuki off in the car and motored back to the boat, where the battery was on its last legs. I have since bought a 88Ah leisure battery for the Bison.

It is not fast, and in serious wind it might struggle but it is unllikely that I would be in the dinghy anyway. At full throttle I guess we were doing about 4 knots, which is fine for us. We only use the dinghy in fairly sheltered water anyway, and the convenience of a motor that you can lift with one hand onto the transom of the dinghy is not to be underestimated, certainly compared to the struggle of lifting a 4 stroke outboard onto the transom. A most insecure feeling in my book!

Regards

Ian

 

[Cloven]

Thanks for that Ian. Bison is a possible on my list. How do you find it?

 

[ianfr]

Dave

It is reasonably well made, comes with a spare propellor, which is good. Needs to be rinsed in fresh water after use as a precaution. But at least you can just empty the kettle mover the bits that got wet. With the proviso that it is not built like a series 1 Land Rover it is a cheap practical solution.

Providing you are not in a hurry, it seems to work well, and is very quiet. When we took the old Suzuki up the creek to the car, we managed to get within a metre of the mullet before they suddenly took off with a splash!

In an exposed anchorage, it is probably not the right answer.

PM me if you want more info.

Ian

 

[Cloven]

Thanks Ian.

Sounds like it will do the job and yes I had noticed the provision of a spare prop in the ads. As you will see from my OP #1 above, I plan to only use this in a very sheltered situation and freshwater. Dinghy is 12ft in a traditinal gaff rig style so heavier than a sporty dinghy. It will take the 2.5hp 4 stroke Yamaha I already have if I really needed it for longer distances etc. However, the tiller badly fouls the top of the engine and I am hoping that the smaller size of top of the electric one will clear OK. Tiller has an upward curve in it to allow for some clearance but it is not enough for the Yamaha.

 

[ianfr]

Thanks Ian.

Sounds like it will do the job and yes I had noticed the provision of a spare prop in the ads. As you will see from my OP #1 above, I plan to only use this in a very sheltered situation and freshwater. Dinghy is 12ft in a traditinal gaff rig style so heavier than a sporty dinghy. It will take the 2.5hp 4 stroke Yamaha I already have if I really needed it for longer distances etc. However, the tiller badly fouls the top of the engine and I am hoping that the smaller size of top of the electric one will clear OK. Tiller has an upward curve in it to allow for some clearance but it is not enough for the Yamaha.

You might need the 55lb or bigger perhaps depending on the weight of the LOADED dinghy.

Ian

 

[The Dogs Pollacks Brother]

We have an electric o/b on our inflatable tender. We use it to go from the pontoon to the mooring, a run of about 150 meters with usually 2 adults and all the kit and tackle for a days fishing. It does the job perfectly for us with no issues so far. We use a sealed golf buggy battery that we purchased from Amazon...came with charger and a neat carrying bag as well. The one thing I would recommend though is a thorough wash in fresh water after each use..the motor that is, not the battery!

 

[Cloven]

We have an electric o/b on our inflatable tender. We use it to go from the pontoon to the mooring, a run of about 150 meters with usually 2 adults and all the kit and tackle for a days fishing. It does the job perfectly for us with no issues so far. We use a sealed golf buggy battery that we purchased from Amazon...came with charger and a neat carrying bag as well. The one thing I would recommend though is a thorough wash in fresh water after each use..the motor that is, not the battery!

Something like this?

http://www.amazon.co.uk/dp/B002OIDQ...UTF8&colid=C1W317P9RBBY&coliid=I15LE0ZQ22X0P6