Minnekota Endura 40 Max on 48V lithium ebike battery via 48V-12V DCDC golf converter.

[chrishvid]

Hello. I am an ebike enthusiast with several nice 48V LiFPO4 packs (10-15Ahrs sizes) (each capable of around 1000 watts output).

I recently acquired a nice Minnekota EnduraMax (PWM) trolling motor for my 14foot canoe, and I wanted to run it directly off the lithium packs, so I got a 48 to 12V DC DC converter from Amazon, for around 70 dollars Canadian (a "golf cart converter".

I was hesitant to use it directly on the motor, as some consultants on the endless-sphere ebikes forum indicated that the DC DC (probably a buck converter) waveform ("dirty"/chopped) might conflict with the PWM controller in the Minnekota.

So I paralleled the DCDC (outputs 12.5volts,25 amps approx.) with a medium sized AGM battery to feed the buffered 12V power to the motor. That worked fine. In spite of what they told me, I decided to try the DC DC 12.5volt output directly to the motor anyway, in a garbage pail full of water. It ran perfectly! Quiet and powerful.

I ran it at 75% throttle for 10 minutes with no overheating of the DCDC box. I had a 50amp breaker on the motor leads, and a 20 amp fuse on the ebike pack before the DC DC. I ran a watt meter on the ebike pack as this was running the motor, and it was indicating 6 amps, at 52 volts, to the DC DC - around 360 watts out of the ebike pack - very manageable for a small 48V10Ahr ebike pack. The amount of churn of water in the pail (powerful!) indicated that the motor was producing around .4 hp on full throttle (around 280 watts, which would be consistent with the rating for 12V/25 amps from the DC DC written on the outside of it).

So, I should be able to use my fancy ebike packs with no issues, to run the Minnekota - which is awesome, because I get about the same energy out of a 10Ahr 48V nominal Lithium pack as an 80Ahr AGM (Trojan), with less voltage sag and about 1/4 of the battery weight, which also helps the boat itself go faster. With a couple of big paralleled lithium packs (Headways) I should be good for about two days worth of trolling at a nice 2.5 knot speed, around 40% throttle on the motor.

This is awesome!

Nice to leverage those packs without a lot of lead to carry around. Lithium packs are improving rapidly and you can get a 700watt hour pack for maybe 600 U.S., with 2000 charge cyle lifespan, and very flat voltage curve to 90% depth of discharge. That's going to be way better than an 80Ahr AGM discharged to 50%SOC (to protect it). The lithium with almost double the energy would weigh 40 lbs. less! I can do almost 3.75 knots at 80% throttle with the canoe.


...and now I'm thinking "solar panels"...

[inetdog]

Chris, please try to include some white space (line breaks at end of paragraphs and even blank lines) in future posts. That big block of text the width of the computer screen is very hard to read.

[chrishvid]

Chris, please try to include some white space (line breaks at end of paragraphs and even blank lines) in future posts. That big block of text the width of the computer screen is very hard to read.

No worries. Thanks for the posting tips.
Chris

[Sunking]

So why use 16S lithium packs? Why not just use 4S lithium and not have to suffer 50% efficiency loss you experienced, and eliminate the wasteful converter? Essentially you turned your lithium into a lead acid battery.

[chrishvid]

So why use 16S lithium packs? Why not just use 4S lithium and not have to suffer 50% efficiency loss you experienced, and eliminate the wasteful converter? Essentially you turned your lithium into a lead acid battery.

No way I'm experiencing 50% efficiency loss. The 52V15Ahr ebike pack output (312 watts measured to the DCDC at 6 amps) is translating to about 280 watts DC output (12V/25amps) from the DCDC to the motor - my circuit breaker trips at 27 amps. The DCDC converter is rated at >=90% efficiency. I'm using 16S LiFPO4 packs because I started this adventure as an ebike hobbyist, and have a fleet of nine ebikes, including folders and recumbent trikes. I'm leveraging my investment in cells, bms'es and chargers. Sure, I could rewire one of the packs to 4S4P and find a 12V lithium oriented BMS, and a new 12V charger. I charge the 48V lithium pack at 5amps. That would need a 20 amp 12VDC charger to get equivalent charge time. So I would need to buy pretty high amperage charger, and build a new lithium pack, and get a new 12V BMS. I build from scratch with parts, mostly Headway cells, from China. My lithium packs (750 watt hour sized) are about 600 dollars. That's way less than many of the 12V "fishing lithium packs" available in North America, which are generally way overpriced, and require multiple paralleled packs. I can safely pull maybe 300 watt hours out of an 80 Ahr AGM, to 50% discharge at a 30 amp discharge rate due to Peukert effect, while I can easily pull 650 watt hours out of a 15 lbs lithium pack. Thats a lot more energy for a fraction of the weight, all for the price of 100 dollars more than my original ebike battery investment, not to mention the much longer cycle life of the lithium cells, and the modularity of construction, whereby individual cells can be replaced if necessary. I've got over three years and 13000 miles on my e-recumbent-trike on one of the lithium packs, and its still going strong. Looks like I didn't need to buy the AGM.
You are right though, in the sense that if I was just starting the whole adventure, I could build the 12V lithium pack from scratch, after finding a fairly "high" amperage charger to charge it on, with a lithium charge profile. Whereas low amperage ebike lithium chargers are inexpensive and readily available. And I can dual purpose the pack, if I take an ebike on the canoe to Saltspring Island.

[Sunking]

No way I'm experiencing 50% efficiency loss. The 52V15Ahr ebike pack output (312 watts measured to the DCDC at 6 amps) is translating to about 280 watts DC output (12V/25amps) from the DCDC to the motor - my circuit breaker trips at 27 amps. The DCDC converter is rated at >=90% efficiency.

Regardless you are still wasting significant power.

I charge the 48V lithium pack at 5amps. That would need a 20 amp 12VDC charger to get equivalent charge time. So I would need to buy pretty high amperage charger, and build a new lithium pack, and get a new 12V BMS. I build from scratch with parts, mostly Headway cells, from China. My lithium packs (750 watt hour sized) are about 600 dollars. That's way less than many of the 12V "fishing lithium packs" available in North America, which are generally way overpriced, and require multiple paralleled packs.

You are paying way too much for lithium batteries. I can understand using LiPo for ebikes needing the 10C discharge rates, but to get that you are sacrificing huge money nearly $1/wh, and with LiPo at best you may get 500 cycles.

I never said anything about using LiPo batteries or even a 12 volt battery. Us EV dudes use superior batteries at less than 1/2 the cost you are paying, 4 to 6 times the cycles, and no BMS required. We use LiFeP04 aka LFP cells. Most popular is CALB. For your boat motor application something in the 40 to 60 AH capacity like a CALB CA40 or CA60. A set of 4 CA40 cells will cost you roughly $220 and CA60 around $330. Even better and more useful for a trolling motor is CA100 and 4 of those cost you $550 or a watt hour cost of 43 cents. Not only will 4 of the CA100 be a lot less expensive but about twice the capacity 4 to 5 times the cycles and no BMS required.

[chrishvid]

Regardless you are still wasting significant power.



You are paying way too much for lithium batteries. I can understand using LiPo for ebikes needing the 10C discharge rates, but to get that you are sacrificing huge money nearly $1/wh, and with LiPo at best you may get 500 cycles.

I never said anything about using LiPo batteries or even a 12 volt battery. Us EV dudes use superior batteries at less than 1/2 the cost you are paying, 4 to 6 times the cycles, and no BMS required. We use LiFeP04 aka LFP cells. Most popular is CALB. For your boat motor application something in the 40 to 60 AH capacity like a CALB CA40 or CA60. A set of 4 CA40 cells will cost you roughly $220 and CA60 around $330. Even better and more useful for a trolling motor is CA100 and 4 of those cost you $550 or a watt hour cost of 43 cents. Not only will 4 of the CA100 be a lot less expensive but about twice the capacity 4 to 5 times the cycles and no BMS required.

I'm not using LIPO at all. I'm using 15Ahr Headway Lithium Iron Phosphate LIFp04 cells at 16S, rated at 3C, and 2000 charge cycles. That's at least as high quality as the Calb cells. 4 Calb cells (60 Ahr) with about 720 watt hours of energy will cost me almost exactly the same price in Canadian dollars FOB Victoria (330US+Shipping+Tax+Cdn/US conversion), as a 48V15Hr Headway pack shipped directly from China, with basically the same energy content (750 watt hours, less a bit) and a good BMS. Your 330 US is almost double that in Canadian dollars FOB Victoria. Here's the pack I ordered from China...

https://bmsbattery.com/ebike-battery...k-battery.html. 409US + shipping.

That's also about 600 Cdn dollars with shipping from China, which is less than shipping fromt the US to Canada with Fedex or UPS. I'm paying basically the same amount, for a battery with the same energy content, with built in cell balancing, with the ability to fix the pack if a cell goes bad. Same chemistry, same price? I doubt you would get more cycles out a Calb or a Winston than a Headway of the very same chemistry with better balancing. There is less than a 5% difference in price between the two setups. Your quoted prices do not include shipping or tax or currency translation.

Anyway the Headway pack is quoted at 409 vs 330 US for the Calb60 equivalent sans shipping, for basically the same watt hours, the difference being the cost of a decent BMS I assume, and pack construction.

It is certainly not "a lot less expensive".

[chrishvid]

Sunking,
Please note: I did mention that I am using 15Ahr Lithium Iron Phosphate LIFP04 battery packs kicking off my very first post running at 48V nominal (16*3.65 full charge). Of an equivalent size energy-content-wise to 4 Calb 60 amphr packs running at 12 volt nominal (4x3.65 full charge). Landed in Victoria there is essentially no difference in price, if you include interconnects and a BMS. Or lifespan. And I can't dual purpose the Calbs on my ebikes and my trolling motor on the same adventure. 330US costs almost 600Cdn to get it to Victoria. Same chemistry. Same pack weight (around 16lbs). Both around 750 watt hours. Both are around 90cents Cdn per watt hour.