Using Lithium batteries in parallel?

[T i m]

Hi,

Hands up here, not directly a cycle related question as such but it could easily be (and I do have a Powabyke and designed, built and raced an electric motorbike). ;-)

I have a small 12V electric outboard that draws about 30A on full and about 15A on a more practical (walking) speed. If I had two 12V / 20Ah Lithium (LiFePO4) batteries, say:

https://www.ultramax.co.uk/media/catalog/product/pdf//s/l/slaumxli20-12-tech_4.pdf

could I use and charge them in parallel and if not, what would the panel recommend to give a battery of around 60-100 Ah capacity please?

Cheers, T i m

 

[Deleted member 4366]

I made two batteries for my outboard. the first one was a reconfigured e-bike battery. I cut the 14 Ah 36v 10S6P cell-pack into three parts, two were 4S6P and one 2S6P. I then joined the two to make a single 4S12P 28Ah pack. I chucked the BMS and wired on a 4S ballance lead connector so that i could charge with a standard lipo balance charger.

the second one I made out of the 4S 5AH Lipo hard packs from Hobbyking. I bought one of the balance boards from Ebay, took the back off and soldered some thick wire allong the two main power tracks and I beefed up the power leads. I could then plug in as many hard packs as I wanted. 8 fitted nicely in a plastic tub with a sealed lid. once paralleled on the board you can charge and discharge them all at once. I used the maximum 6 packs for 30Ah.

The motor goes a lot better with 4S, which is nominally 14.4v.

Balance board:
http://www.ebay.co.uk/itm/T-Plug-Parallel-Charging-Balance-Board-for-Lipo-LiFe-Li-ion-IMAX-B6-B8-Charger-/231928383673?epid=524136997&hash=item36000248b9:g:2XAAAOSwq7JUF-V5

Lipo hard packs
https://hobbyking.com/en_us/turnigy-5000mah-4s1p-14-8v-20c-hardcase-pack.html?___store=en_us

 

[T i m]

Thanks very much for the prompt reply and info d8veh. ;-)

So, as you often have in these multi series / parallel packs, as long as you start with something that is reasonably well matched, you should be ok connecting a couple of packs in parallel?

I currently run an MK M34 SLD G deep discharge 12V, 60Ah lead acid battery and that's ok, other than it weighs about the same as my 4/ 2.5hp outboard! ;-(

So, assuming a 50% DOD on the LA, and the 15A constant draw from the outboard, that should give me a good 2 hours running time (and it does).

However, I believe the Lithium batteries have a much sharper cutoff than a LA and so I was hoping to get two Lithium batteries (or 4 x smaller ones and permanently pairing them etc), where the total weight would be less than the 17kg I have now but maybe spread across two batteries so that I could use one battery on the way out, knowing I could then also get back on the other (allowing for wind and current etc).

So, assuming an 80% DOD on a Lithium (LiFePO4), a 12V x 40Ah battery would give me about the same 30Ah as the LA battery and so I'd get double the range for less weight and better protection (all be it at a fair cost). That said, my existing battery retails for around £200 and I have seen the 40Ah Lithiums for about £400 each. Given I should get a good few cycles out of them they could outlast me. ;-)

Something like this:

https://www.ultramax.co.uk/lithium-phospate-replace-sla-batteries/li40-12-12v-40ah-lithium-iron-phosphate-lifepo4-high-capacity-deep-cycle-battery-charger-included-l-mm-w-mm-h-mm-196-164-172.html

(as you see, also comes with a charger etc).

That said, another part of me would prefer to do as you did and build up my own (single) battery with something like the Sinopoly 100Ah cells:

https://www.ev-power.eu/Sinopoly-40Ah-300Ah/SP-LFP100AHA-Lithium-Cell-LiFePO4-3-2V-100Ah.html

But I'm not sure what else I would need ... like a BMS maybe and what current spec would I be looking at (40A)?

The reason I might prefer the individual cells is then I can manage them independently and replace the BMS, should I require etc?

Cheers, T i m

 

[Deleted member 4366]

LiFePO4 is heavy. I'd rather use normal Li-ion, which is half the weight. Lipo is cheap. 30Ah of 4S is only £120. I can't see any advantage in using those sealed LiFePo4 batteries.

All batteries have to be approximately the same voltage if you want to bring them in parallel.

 

[T i m]

Thanks again for the reply and info. ;-)

I thought I read somewhere that LiFePO4 was safer, and whilst lightness is of interest, it's really only to get the mass of any one battery down to something that is a bit easier to manhandle, in and out of the boat than the 17kg of the LA battery. So, 10kg would still be just over half the weight of my LA and if using the Sinopoly 100A cells, nearly 3 times the capacity.

And once the batteries are in the boat, weight isn't really an issue (unlike in a car or eBike etc). ;-)

The optimum goal would to be to have as large a capacity of the safest batteries I could afford to give me the longest continuous run time whilst being able to lift them in and out the boat easier than what I have now. ;-)

What I actually end up with will probably be a compromise of all of that. ;-)

Cheers, T i m

 

[Deleted member 4366]

If li-ion batteries aren't safe, why are they in every phone, laptop and nearly all E-bikes?

 

[Nealh]

For the foreseeable future li-on is going to be king and larger EV platforms are having cells mass produced, with massive manufacturing plants being built to accommodate production and mass production for the future. 18650 at the moment with 21700 cells likely to compete with higher ah rating and possibly a more sustainable better amp rating in years to come, for not much more in cell size increase.

 

[T i m]

If li-ion batteries aren't safe, why are they in every phone, laptop and nearly all E-bikes?

I didn't say (or even suggest) they weren't safe, I just though I understood that 'LiFePO4 was safer'?

If I am wrong with my understanding then I'm happy to be corrected. ;-)

Cheers, T i m

p.s. I just found this: (And I wasn't looking for LiFePO4 specifically, that's just what came up as being available and locally at a reasonable price and capacity).

"Lithium Iron Phosphate(LiFePO4)
... The key benefits are high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.

Li-phosphate is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time.

Li-phosphate has excellent safety and long life span but moderate specific energy and elevated self-discharge."

http://batteryuniversity.com/learn/article/types_of_lithium_ion

And:

"The lithium iron phosphate (LiFePO
4) battery, also called LFP battery (with "LFP" standing for "lithium ferrophosphate"), is a type of rechargeable battery, specifically a lithium-ion battery, which uses LiFePO
4 as a cathode material, and a graphitic carbon electrode with a metallic current collector grid as the anode. LiFePO
4 batteries have somewhat lower energy density than the more common lithium cobalt oxide (LiCoO
2) design found in consumer electronics, but offer longer lifetimes, better power density (the rate that energy can be drawn from them) and are inherently safer. LiFePO
4 is finding a number of roles in vehicle use and backup power."

https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

I saw the 'inherently safer' and thought it might be a 'good thing', both when sitting next to it in my small wooden boat and when it's being charged at home. ;-)

 

[Deleted member 4366]

Good luck to you and all who sail in your boat.

 

[T i m]

For the foreseeable future li-on is going to be king and larger EV platforms are having cells mass produced, with massive manufacturing plants being built to accommodate production and mass production for the future. 18650 at the moment with 21700 cells likely to compete with higher ah rating and possibly a more sustainable better amp rating in years to come, for not much more in cell size increase.

I think I follow that <g> ... so are you saying there (and don't forget I'm new to all this) that even the biggest Lithium(-ion) batteries (like those used in power walls etc) are always just banks of these smaller cells? I'm aware that many what I would call small to mid-sized packs are made up like this as I've opened some up (eScooter, cylindrical cells and PowaByke, flat cells), it's just I wasn't sure how far you could safely / practically go with the whole series / parallel cell combination thing?

My BIL now has a PV battery in his house and it's made up of 4 large rack mount modules, all joined in parallel (and are LiFePO by the looks of it).

http://shop.solarproductsolutions.com.au/product/pylontech-us2000b-battery/

Maybe I was thinking these might be nearer my boat power needs than the cells favoured for RC or eBike applications (where low weight and highest energy density possible are paramount).

But I'm still only thinking out loud .. ;-)

Cheers, T i m

 

[T i m]

Good luck to you and all who sail in your boat.

Thanks for that. ;-)

As someone who spent far too many hours as a lad stuck in front of a British Seagull outboard motor, the 'luxury' of the silence you get with the Minn Kota type electric outboards (mine is actually badged Yamaha) is worth investing in (IMHO). My Tinnitus also appreciates the lack of noise. ;-)

To be able to talk to the others in the boat without shouting and leave no (riverside) pollution is also a 'good thing'.

What outboard do you have and what sort of duration did / do you typically get out of it with the packs you mentioned?

Because we are normally on rivers and canals with little in the way of any current and sheltered from the wind ... we aren't looking for speed ('performance'?) because most are limited to 5 knots anyway, but a good duration. The ideal would be to be able to cruise for a day on batteries that we (or more importantly, the Mrs) could lift easily.

Like you have already done, I wouldn't be against experimenting with existing packs (say designed for RC or eBike use), as long as the final solution was as safe as most would consider reasonable and was the most reliable in use. However, because I don't have that much spare time (and what I have I would rather spend boating) it would be more 'efficient' for me to buy something ready to run. It might also be easier to sell on, should we have to give it all up for some reason.

Realistically, at 50% DOD the LA battery we currently have should give 500 cycles and that likely to see us out (I'm 60), especially if we drop it though the bottom of the boat! ;-)

Cheers, T i m

 

[Deleted member 4366]

I use mine on an inflatable tender for my sailboat, though I sometimes go off in the inflatable to do some fishing (trolling). the motor's pretty good for that because I can go slowly and quietly. Petrol motors are too fast, even on tickover. It's only used at sea. I'm not sure of the duration because I've never run it right down. I'm normally out for an hour or so, but only at low power. The other times, it's rarely more than 2 10-minute trips to and from the mothership.

It's one of these or similar. I seem to remember 40 amps:
http://www.ebay.co.uk/itm/Motor-Boat-Engine-Outboard-40lb-Electric-Trolling-Thrust-Dinghy-Kayak-Tender-UK-/162598159151?hash=item25db9b032f:g:QJ0AAOSwRXRZR2jh

 

[anotherkiwi]

Just to add that most flat devices use LiPo pouch cells: my Google nexus 7, my Nikon camera for example. And we all know that LiPo is VERY dangerous don't we? And yet there it is in your pocket, near your face every day...

 

[T i m]

Just to add that most flat devices use LiPo pouch cells: my Google nexus 7, my Nikon camera for example. And we all know that LiPo is VERY dangerous don't we? And yet there it is in your pocket, near your face every day...

Not a Samsung Galaxy Note 7 I hope? ;-)

Assuming you are being sarcastic (?), *I* haven't said any battery technology was very dangerous or even dangerous just that these things can and do go up in flames and probably why many delivery companies (including Royal Mail) have restrictions on what cells they will or won't carry. What I did suggest is that some chemistry's are safer than others (and included supporting links).

A mate, after RC flying came home and put a couple of LiPo packs on charge in the garage. The first thing he knew of something being not right was when the power tripped to the house because a pack had caught fire, burnt the charger and that had tripped the power. Because the power was off he couldn't open the garage doors (electric) to help clear the smoke.

Anecdotal of course but not the only one I'm sure. By comparison I have been running and sometimes abusing (re RC car racing) Lead acid, NiCad, NiMh for many years with no real issues.

If your LiPo pack catches fire in your eBike, you jump off it and watch it burn from a safe distance. Not quite so easy to lift a burning battery out of a wooden boat and throwing it over the side. ;-(

So, the logic was ... if I was going to get a Lithium battery for my electric outboard and if the most easily available seem to be LiFePo4, and those were considered a good m,atch for my application (not weight or energy density dritical) and if that chemistry was said to be 'safER' than others, why wouldn't I use it?

Cheers, T i m

 

[T i m]

I use mine on an inflatable tender for my sailboat, though I sometimes go off in the inflatable to do some fishing (trolling). the motor's pretty good for that because I can go slowly and quietly. Petrol motors are too fast, even on tickover. It's only used at sea. I'm not sure of the duration because I've never run it right down. I'm normally out for an hour or so, but only at low power. The other times, it's rarely more than 2 10-minute trips to and from the mothership.

Interesting and thanks.

It's one of these or similar. I seem to remember 40 amps:
http://www.ebay.co.uk/itm/Motor-Boat-Engine-Outboard-40lb-Electric-Trolling-Thrust-Dinghy-Kayak-Tender-UK-/162598159151?hash=item25db9b032f:g:QJ0AAOSwRXRZR2jh

Yup, that could well be the same as mine as ignoring actual electric outboards like the Torqeedo range, most of these 'Trolling Motors' are just a motor in a waterproof casing on a stick. ;-)

Cheers, T i m

 

[Deleted member 4366]

They're only efficient on full power. They use resistors to cut down the power on the lower settings. Some guys use proper brushed motor controllers that use PWM for power regulation, which is much more efficient. Also aeroplane propellors make a big difference, but they're a bit easier to damage.

 

[T i m]

They're only efficient on full power. They use resistors to cut down the power on the lower settings.

Really?. ;-( I thought I'd opened the handle up on mine and saw some electronics but I'll have to look again.

Some guys use proper brushed motor controllers that use PWM for power regulation, which is much more efficient.

Ah. ;-( If that is the case then, I wonder if it would be 'better (ignoring PWM for a second) to run the outboard on full from one lower voltage pack (like an 8V Nissan Leaf / 64Ah jobby)?

Also aeroplane propellors make a big difference, but they're a bit easier to damage.

As a marine prop you mean? It's amazing the range of things people will try. ;-)

Cheers, T i m

p.s. When I was racing EV's (Electralites ?) I raced against Cedric Lynch who also built an electric outboard using one of his own Lynch Motors. Because the (pancake) motor didn't lend itself to underwater use, he converted a lightweight petrol outboard by replacing the engine with his motor and the metal bevel gear in the under water unit with some 'plastic' gears that along with plastic bearings could be lubricated by the water itself. This meant he could do away with the oil seals that created quite a bit of drag and hence wasted energy. ;-)

 

[anotherkiwi]

Not a Samsung Galaxy Note 7 I hope? ;-)

Assuming you are being sarcastic (?), *I* haven't said any battery technology was very dangerous or even dangerous just that these things can and do go up in flames and probably why many delivery companies (including Royal Mail) have restrictions on what cells they will or won't carry. What I did suggest is that some chemistry's are safer than others (and included supporting links).

A mate, after RC flying came home and put a couple of LiPo packs on charge in the garage. The first thing he knew of something being not right was when the power tripped to the house because a pack had caught fire, burnt the charger and that had tripped the power. Because the power was off he couldn't open the garage doors (electric) to help clear the smoke.

Anecdotal of course but not the only one I'm sure. By comparison I have been running and sometimes abusing (re RC car racing) Lead acid, NiCad, NiMh for many years with no real issues.

If your LiPo pack catches fire in your eBike, you jump off it and watch it burn from a safe distance. Not quite so easy to lift a burning battery out of a wooden boat and throwing it over the side. ;-(

So, the logic was ... if I was going to get a Lithium battery for my electric outboard and if the most easily available seem to be LiFePo4, and those were considered a good m,atch for my application (not weight or energy density dritical) and if that chemistry was said to be 'safER' than others, why wouldn't I use it?

Cheers, T i m

Yes I was being a bit cynical. LiPo has one default - human error. You can't compare the punishment a LiPo battery takes in a model plane or a car with the treatment the same battery gets in an e-bike or on a boat or in my nexus 7 tablet and my Nikon camera. The cell in my nexus isn't even in a hard case, just the bare pouch which uses the tablet as protection! Now if it wasn't safe would Google be taking the risk of putting it on the market?

Overcharging, using down past recommended LVC, crashing, exposing to heat... if you look at the LiPo fires on YouTube there are not many that are spontaneous "I'm in a bad mood today I feel like going on fire" kind of thing are there? I am careful with my LiPo but I don't believe that it is as dangerous as advertised when it is respected.

PS a trolling motor is on my shopping list and it will be powered by 4S LiPo.

 

[T i m]

PS a trolling motor is on my shopping list and it will be powered by 4S LiPo.

Possibly following on from that thought ... I've gone from looking at 12V Lithium LA replacements (monoblocks) to ready made packs to making my own (LiIon?) packs.

Basically it should design itself, once I have found the key ingredients, cells, BMS and charger.

e.g. If I have a 12V outboard that sets that parameter (voltage) and that it has a maximum current of 30A (so that with the voltage sets the spec of the BMS) and with a typical 15A constant current and assuming an 80% DOD, the minimum capacity of the battery. The maximum capacity would be the maximum mass of the entire package and the cost.

I was inspired by watching this:

I like the laid back style, the pace and detail of the presentation and the very practical / hands on approach. ;-)

So, you can buy 12V x 60Ah LiIon packs off eBay but they aren't typically using branded (LG or Panasonic) cells ... so the $100 question is what are the risks of using unbranded cells?

If the answer is typically 'lifespan', then for my electric outboard it probably wouldn't ever be a problem, even if I only saw 100 cycles out of a pack as we might only go boating 10 times a year?

If the answer was reliability then presumably I could make a pack up using fuses to connect each cell in a row so if it goes it shouldn't take anything else with it?

Or do I do as you suggest and use maybe 4 x 4S 10,000mA LiPo packs in parallel (presumably with their own built in BMS)?

Suggestions welcome. ;-)

Cheers, T i m

 

[Deleted member 4366]

Don't use recycled 18650s. A few of us have done it. The amount of sorting and testing you need to do, plus the risk of a fire and all the cuts and burns you get from doing it, to end up with a saggy battery that may never be safe to use and with dubious life-span, it's just not worth it if you aim is to end up with a working battery. My advice is to get those 4S lipo hard-packs. They're pretty safe and easy to handle. Do the balance board mod that I suggested earlier, and you end up with a plug-and-play battery.