18650 trolling battery solar charging

dbldrew

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Ok so have some questions on charging a battery pack built with 18650 cell. So basically the background of what im doing is every other year or so we go up camping up to MN up near ELY. Its a big camping/fishing trip. It is all canoe fishing, and a few years ago I put a small trolling motor on my canoe, which works great. But the 100ah battery im using is super heavy and just doesn't last. The place where we stay does not have any electricity. So in the past I have just pulled out the battery and put jumper cables on it from my running truck to charge it back up.

Now I want to change my set up for a couple of reasons. Some times we have to do small portages (carrying the canoe across land from one lake to another) and that huge lead acid battery is super heavy. And I also want another option for charging. So I'm in the process of making some battery packs out of 18650 cells. And I was going to charge them using 200W solar

The charge controller is a Renogy Wanderer 10 Amp 12V/24V PWM Negative Ground Solar Charge Controller
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

the solar panels Im using is 4 -50W flexible panels

https://www.ebay.com/itm/353095224156

So I was thinking of making 2 smaller battery packs rather then having just 1 big one like i had before, so 2 that are around 50ah ea, that way one will be on the solar charging up all day while the other is being used.

My old lead acid was a walmart "deep cycle" battery that was rated at 105ah and I could get around 2 ish days of use out of it before it would drop down to around 12.00V which is ballpark around 50% drained and everything I have heard is to make them last dont discharge below 50%

So one of my questions is in the AH rating of the different batteries. Is that 105ah battery rated for safe usable power? like the 105ah is based on only a 50% discharge rate? or is the 105ah based on completely draining the battery?

So I know that Lithium Ion has a much high % of usable power so im trying to get a ballpark number of cells to use to get comparable same "2 days of use"

Which brings me to my next question 12.6v or 16.8v? I have seen a lot of people building trolling motors using 4 in series rather then 3 to get 16.8v. a 18650 fully charged is 4.2v while drained is around 3v. So if i build it in 3 in series that gives me a 12.6v battery which sounds perfect. But drained im looking at 9v so not sure at what point the lower voltage will not work with the trolling motor. Which is why i have heard of people using 4 in series to get 16.8v down to a 12v drained battery.

So I was leaning towards the 4 in series to get the 16.8 volts, but what about charging that high with my solar set up?

So I guess I have rambled long enough, tell me what your thoughts are and thanks in advance for any help.
 
A 105 ah lead acid is rated 105ah if discharged over 20 hours. But thats only for high quality deep discharged batteries that can actually handle that type of use. Like the odyssey agm's (very expensive) they can handle being drained below 12 volts many times before they lose capacity. The cheaper lead batteries its best not to go below 12 volts.

For your situation I recommend the 3s li-ion, that will charge extremely well with solar. The voltage differential is great enough that you get a good charge. In my situation with a 240 watt panel and mppt controller I was getting up to 15 amps into my 3s li-ion battery. With lead acid and a 4s lifepo4 I only get about 12 amps from the same panel. I saw peaks of 17 amps every once in a while (which was close to 244 watts from reading the mppt controller lcd screen).

With a 4s li-ion, you need more than 16.8 volts bulk setting to charge, closer to 18 volts, you have to have a big voltage differential to fast charge. If its too close to the 16.8 volts, your controller won't put out too many amps. You need to check to see if your controller bulk voltage can be set high enough for a 4s. Don't use the lithium setting if it has one, it will charge too slow. With solar you need the bulk voltage setting high enough to quickly charge while the sun is out.

Since you will be charging with solar I recommend the chargery bms8t bms, its the only bms I trust with solar. Especially if you plan to fast charge the battery. This way you can set the bulk setting on your controller high enough to quickly charge the battery. If you want to see the status of your battery while charging its the bms to get, fully programmable, balances at 1.2 amps and has audio alarms, temps sensors.

As far as capacity, a li-ion battery can be drained all the way until the bms shutsoff. So a 50ah li-ion would be comparable to a 100ah lead acid, except the voltage will be lower as it gets drained but still usable if your equipment can operate at those voltages. If you drain less it will last longer but fully draining everytime will still outlast any lead acid even the odessey.
 
I would add that 4 x 50w = 200w of solar panels. 200w/12v = 16.6 amps. Even if you're only doing 75% of 200w, that's still 150w/12v = 12.5a- a bit above the 10a max in the charge controller you list.

The practical range of 18650 is 4.15v high and 3.3v low.
For 3s, that's 12.5v high and 9.9v low
For 4s, that's 16.6v high and 13.2v low

The trolling motor would probably operate stronger on 4s... but 16.6v high is higher than nominal (typical) 12v batteries and a 12v charge controller may not work that high. That's probably one of the reasons @jonyjoe505 recommended 3s. The remedy is to make sure you get a programmable 12/24v charge controller - where you can custom set the high of 16.6-16.8vfor 4s OR 12.5v for 3s as neither of these are not quite normal for 12v.

Another angle is to go LifePO4 instead of 18650 - and then 4s will match lead-acid 12v voltage ranges.

I'm sure others will add comments - sounds like a fun project :)
 
thanks for the heads up on the charge controller, canceled that and now will look for a better option. What if i ditch the charge controller all together? Is there a good bms that can handle the charging and I connect the solar panels directly into the bms? The panels are listed as 18v so maybe a 4s would work in that situation? Or is that not a good idea?
 
jonyjoe505 said:
As far as capacity, a li-ion battery can be drained all the way until the bms shutsoff. So a 50ah li-ion would be comparable to a 100ah lead acid, except the voltage will be lower as it gets drained but still usable if your equipment can operate at those voltages. If you drain less it will last longer but fully draining everytime will still outlast any lead acid even the odessey.

This was my worry, how well will it work when the voltage drops under 11v. Which is why everyone i have seen that has made trolling batteries have all done 4s. Which is why i was leaning that way but then the problem comes with charging. have to try and find a charge controller (thats not crazy $$) that I can adjust the charging voltage, unless having the solar straight into the BMS is an option
 
dbldrew said:
thanks for the heads up on the charge controller, canceled that and now will look for a better option. What if i ditch the charge controller all together? Is there a good bms that can handle the charging and I connect the solar panels directly into the bms? The panels are listed as 18v so maybe a 4s would work in that situation? Or is that not a good idea?
Not a good idea to try to charge Lithium-ion directly from panels. The top voltage must be regulated to ensure it doesn't go above 4.2v/cell or you're at risk of fire. For 3s/4s 18650 -you need a charge controller where you can set the top charging volts yourself - in the 12/24v range.

The one I started with (which is fully programmible) is this - https://www.amazon.com/Controller-N.../24v+charge+controller&qid=1591371752&sr=8-14

Another one that is cheaper, fully programmable is the famous MPT-7210a (many youtubes on this). Its limited to 10a on output but is fully programmable - and you could do 2 in parallel if you like the 1st one. https://www.ebay.com/itm/LCD-MPT-72...738891?hash=item23d5cb7fcb:g:aQYAAOSwe9tepqNQ

Perhaps someone can recommend a cheap 20a/24v they know is programmable.

P.S. A BMS is for battery safety (shut it off if v is too high/low, temp to hi/low) and many add a balancing feature... and is recommended!. But they don't includecharging.
 
OffGridInTheCity said:
dbldrew said:
thanks for the heads up on the charge controller, canceled that and now will look for a better option. What if i ditch the charge controller all together? Is there a good bms that can handle the charging and I connect the solar panels directly into the bms? The panels are listed as 18v so maybe a 4s would work in that situation? Or is that not a good idea?
Not a good idea to try to charge Lithium-ion directly from panels. The top voltage must be regulated to ensure it doesn't go above 4.2v/cell or you're at risk of fire. For 3s/4s 18650 -you need a charge controller where you can set the top charging volts yourself - in the 12/24v range.

The one I started with (which is fully programmible) is this - https://www.amazon.com/Controller-N.../24v+charge+controller&qid=1591371752&sr=8-14

Another one that is cheaper, fully programmable is the famous MPT-7210a (many youtubes on this). Its limited to 10a on output but is fully programmable - and you could do 2 in parallel if you like the 1st one. https://www.ebay.com/itm/LCD-MPT-72...738891?hash=item23d5cb7fcb:g:aQYAAOSwe9tepqNQ

Perhaps someone can recommend a cheap 20a/24v they know is programmable.

P.S. A BMS is for battery safety (shut it off if v is too high/low, temp to hi/low) and many add a balancing feature... and is recommended!. But they don't includecharging.

if i get the MPT-7210a would there be any issue with running the 4 - 50W panels that could produce more amps then the output of the controller? Or is it just not getting the full potential of the panels?
 
dbldrew said:
if i get the MPT-7210a would there be any issue with running the 4 - 50W panels that could produce more amps then the output of the controller? Or is it just not getting the full potential of the panels
According to this listing (https://sightsolar.com/product/lcd-...boost-for-solar-battery-regulatir-controller/ ) of features....
"Overload protection: the controller will automatically cut off circuit if overload."

So it sounds like it would just not produce any power - in which case you could re-configure to use 3 panels instead of 4. The thing is - if its shady or cloudy or angle is not greatit will reduce the power of the 4 panels andmay not be an issue.

You can experiment a bit with panels - just hook them up into dead-short and use a clamp (amp) meter to measure the amps as you position them - flat or at an angle etc - and get an idea of how 4 will behave, then try 3 etc.
 
I would use a Victron Smart MPPT for a charge controller
I would use a DC-DC converter or a RC balance charger to charge from the cars 12v system

Personally I think mobile solar is a lot of work, bulky, and inconvenient ... I rather just have a storage battery in the truck (like a Tesla EV module), so I can charge the trolling motor battery a couple times from an RC charger. Its going to be WAY faster than waiting for some solar panels.

The storage battery in the truck can be charged/replenished from a small solar setup, and from alternator when the truck is running. This way you dont have to worry about where the trolling motor battery is, or what its doing. I have a small setup in my truck I operate in a similar manner to run a ARB fridge when I camp.
 
dbldrew said:
OffGridInTheCity said:
Another one that is cheaper, fully programmable is the famous MPT-7210a (many youtubes on this). Its limited to 10a on output but is fully programmable - and you could do 2 in parallel if you like the 1st one. https://www.ebay.com/itm/LCD-MPT-72...738891?hash=item23d5cb7fcb:g:aQYAAOSwe9tepqNQ

if i get the MPT-7210a would there be any issue with running the 4 - 50W panels that could produce more amps then the output of the controller? Or is it just not getting the full potential of the panels?
The mpt-7210 can't charge a 3s or a 4s battery really not usable until 7s. Perhaps I missed it Did the battery change from 3s/4s to7 s? The voltage of the solar panels has to be lower than the voltage of the battery.
later floyd
 
floydR said:
dbldrew said:
OffGridInTheCity said:
Another one that is cheaper, fully programmable is the famous MPT-7210a (many youtubes on this). Its limited to 10a on output but is fully programmable - and you could do 2 in parallel if you like the 1st one. https://www.ebay.com/itm/LCD-MPT-72...738891?hash=item23d5cb7fcb:g:aQYAAOSwe9tepqNQ

if i get the MPT-7210a would there be any issue with running the 4 - 50W panels that could produce more amps then the output of the controller? Or is it just not getting the full potential of the panels?
The mpt-7210 can't charge a 3s or a 4s battery really not usable until 7s. Perhaps I missed it Did the battery change from 3s/4s to7 s? The voltage of the solar panels has to be lower than the voltage of the battery.
later floyd
Good point -mpt-7210a- should work for 4s as that's above the 12v range but not good for 3s. There are several youtubes on the mpt-7210a and they might answer the question of 4s explicitly.

@dbldrew - the fundamental problem underlying all this is that 18650 lithium-ion is *just not suited* for easy 12v solutions. This is why folks tend toward LifePO4 for 12v solutions, where the voltage range so much more compatible with 'just standard stuff' :) FYI - they do make LifePO4 18650 container formats - and/or some pouch cells and/or blocks (of LifePo4) are pretty available. Not sure why you're on 18650 lithium-ion but if you haven't purchased cells you - you might want to give that a look.
 
OffGridInTheCity said:
floydR said:
dbldrew said:
OffGridInTheCity said:
Another one that is cheaper, fully programmable is the famous MPT-7210a (many youtubes on this). Its limited to 10a on output but is fully programmable - and you could do 2 in parallel if you like the 1st one. https://www.ebay.com/itm/LCD-MPT-72...738891?hash=item23d5cb7fcb:g:aQYAAOSwe9tepqNQ

if i get the MPT-7210a would there be any issue with running the 4 - 50W panels that could produce more amps then the output of the controller? Or is it just not getting the full potential of the panels?
The mpt-7210 can't charge a 3s or a 4s battery really not usable until 7s. Perhaps I missed it Did the battery change from 3s/4s to7 s? The voltage of the solar panels has to be lower than the voltage of the battery.
later floyd
Good point -mpt-7210a- should work for 4s as that's above the 12v range but not good for 3s. There are several youtubes on the mpt-7210a and they might answer the question of 4s explicitly.

@dbldrew - the fundamental problem underlying all this is that 18650 lithium-ion is *just not suited* for easy 12v solutions. This is why folks tend toward LifePO4 for 12v solutions, where the voltage range so much more compatible with 'just standard stuff' :) FYI - they do make LifePO4 18650 container formats - and/or some pouch cells and/or blocks (of LifePo4) are pretty available. Not sure why you're on 18650 lithium-ion but if you haven't purchased cells you - you might want to give that a look.

I already have a bunch of 18650 but not enough to build the battery bank yet. So If I switch over to 26650 instead, that voltage will work with any solar charge controller? Or do i still need a specific LifePO4 solar charge controller?
 
For 12v, LifePO4 is the way to go. If you're wondering where to get cells - here's a good example of A123(s) you can salvage from a recommended place
https://batteryhookup.com/collectio...ducts/a123-36v-module-w-48-26650-anr26650m1-b

And here's a recent youtube on salvaging the cells from this type of pack-NEC Energy Solutions A123 LiFePO4 Batteries, Cell Harvesting (Battery Hookup) -https://youtu.be/3jPYyGjWqck -

Not pushing this, just showing an example of reasonable price and reliable source youcould use to builda nice 4s pack. These cells are around 2500mah each. To build a 100ah 12v battery you would need aprox4s40p (e.g. 160 of these cells) Or 1/2 that for 50ah.At 50a/cell max discharge it would give you all thepower a trolling motor could want.
Another advantage of LifePO4 that I read all the time is you can discharge them near 100% - e.g. deeper even than Lithium-Ion.
 
OffGridInTheCity said:
For 12v, LifePO4 is the way to go. If you're wondering where to get cells - here's a good example of A123(s) you can salvage from a recommended place
https://batteryhookup.com/collectio...ducts/a123-36v-module-w-48-26650-anr26650m1-b

And here's a recent youtube on salvaging the cells from this type of pack-NEC Energy Solutions A123 LiFePO4 Batteries, Cell Harvesting (Battery Hookup) -https://youtu.be/3jPYyGjWqck -

Not pushing this, just showing an example of reasonable price and reliable source youcould use to builda nice 4s pack. These cells are around 2500mah each. To build a 100ah 12v battery you would need aprox4s40p (e.g. 160 of these cells).

thats funny thats exactly where I ordered my cells from.

I ordered 96 of them, so depending on how many turn out good I could make either 1 bigger pack or 2 smaller battery packs. guess maybe I could make a 3s 18650 pack as well as a reserve with the cells I already have.
 
dbldrew said:
OffGridInTheCity said:
For 12v, LifePO4 is the way to go. If you're wondering where to get cells - here's a good example of A123(s) you can salvage from a recommended place
https://batteryhookup.com/collectio...ducts/a123-36v-module-w-48-26650-anr26650m1-b

And here's a recent youtube on salvaging the cells from this type of pack-NEC Energy Solutions A123 LiFePO4 Batteries, Cell Harvesting (Battery Hookup) -https://youtu.be/3jPYyGjWqck -

Not pushing this, just showing an example of reasonable price and reliable source youcould use to builda nice 4s pack. These cells are around 2500mah each. To build a 100ah 12v battery you would need aprox4s40p (e.g. 160 of these cells).

thats funny thats exactly where I ordered my cells from.

I ordered 96 of them, so depending on how many turn out good I could make either 1 bigger pack or 2 smaller battery packs. guess maybe I could make a 3s 18650 pack as well as a reserve with the cells I already have.
Cool :) Maybe you could use 18650 as 4s or 5s or whatever so they are aproximately the same voltage as the 200w panels. Then, I believe you couldplug them into thecharge controller where you'd normally feed in the panels - and use their power to recharge the 12v pack if the sun is down.

In any case, it would be fun to read some updates and/or some pics ofyour project if you are so inclined.
 
Assuming its a basic brushed motor unit with the usual 3to5 fixed speeds, I would recommend 4s Lion over 3s. This is from my own experience with the same application. The motors can handle the overvoltage just perhaps not for long continuous periods (in fact many folks use 4s and arent conservative w/ throttle yet have no problems). 3S is great till the voltage drops then the power loss is significant at nominal cell voltage and below. And in this application you want to use the batteries not nurse them like a powerwall. You want max capacity to weight ratio which favors lion with full 4.2v charge and the ability to take them to 3v if you need - without losing all your thrust first.

You can buy a cheap 60A PWM controller board from amazon or eBay for under 20bucks (i like the red one ; amazon has it under the DROK brand) and use it to control speed with the motor always set to full speed. Only use the motors own control for shifting between off / fwd / reverse. Just make a note of the potentiometer position that matches up with normal full 12v speed and mark it - anything higher than that is your reserve / turbo for short burst use.

This will save your a ton of power versus using the motor at lower than full speed, where the motor just burns off excess power through big resistors.

The only trick is figuring out how to waterproof the pwm board without covering up the heat sink. not trivial. because of this , and because the pwm boards can fail, implement it in a way that you can bypass it whilst on the water without too much effort , so you can get home.
 
ttbloker said:
Assuming its a basic brushed motor unit with the usual 3to5 fixed speeds, I would recommend 4s Lion over 3s. This is from my own experience with the same application. The motors can handle the overvoltage just perhaps not for long continuous periods (in fact many folks use 4s and arent conservative w/ throttle yet have no problems). 3S is great till the voltage drops then the power loss is significant at nominal cell voltage and below. And in this application you want to use the batteries not nurse them like a powerwall. You want max capacity to weight ratio which favors lion with full 4.2v charge and the ability to take them to 3v if you need - without losing all your thrust first.

You can buy a cheap 60A PWM controller board from amazon or eBay for under 20bucks (i like the red one ; amazon has it under the DROK brand) and use it to control speed with the motor always set to full speed. Only use the motors own control for shifting between off / fwd / reverse. Just make a note of the potentiometer position that matches up with normal full 12v speed and mark it - anything higher than that is your reserve / turbo for short burst use.

This will save your a ton of power versus using the motor at lower than full speed, where the motor just burns off excess power through big resistors.

The only trick is figuring out how to waterproof the pwm board without covering up the heat sink. not trivial. because of this , and because the pwm boards can fail, implement it in a way that you can bypass it whilst on the water without too much effort , so you can get home.

yes the motor is a 30lb thrust 5 speed. And that was my worry with the 3s being too low in voltage. Now one of my battery banks is going to be made with 26650 cells 4s so that will give a perfect voltage range. But my other battery that Im building is going to be made from 18650 cells so I'm thinking of going with 4s with that one as well.

Now the solar charge controller I picked up was the renogy wanderer wnd30-LI its a 30A charger that does LifePO4 (along with lead acid) but it also has an app that I can make custom charge settings for different battery types.

So I can set the high voltage disconnect to 16.8
Charge limit voltage has a MAX of 17V
I can also set the equalize charge volts
Boost Charge volts
float charge volts

Everything has a max of 17 volt option. So what would the best setting be for a 4s 18650 pack?

I understand that with only having a max of 17v charge limit it would probably take forever to reach the full 16.8v. But thats ok if it could charge to 80% or higher in a reasonable time then that will work for what Im using it for. Would rather have a 4s @~80% charge then a 3s @100% due to the better voltage. Besides this is the back up battery pack and the 26650 pack is going to be the main pack
 
dbldrew said:
So I can set the high voltage disconnect to 16.8
Charge limit voltage has a MAX of 17V
I can also set the equalize charge volts
Boost Charge volts
float charge volts

Everything has a max of 17 volt option. So what would the best setting be for a 4s 18650 pack?

I understand that with only having a max of 17v charge limit it would probably take forever to reach the full 16.8v. But thats ok if it could charge to 80% or higher in a reasonable time then that will work for what Im using it for. Would rather have a 4s @~80% charge then a 3s @100% due to the better voltage. Besides this is the back up battery pack and the 26650 pack is going to be the main pack
You don't want to charge to 17vas that's 4.25v/cells - e.g. greater than4.2v/cell. Lithimum is dangerous if it's charged above it's max and will rapidily shorten it's number of cycles.

For 18650 Iwould max out at 4.15v * 4 = 16.6. For longer live - maybe 4.10v * 4 = 16.4v - and give a bit of wiggle room if cells become a bit unblanced.\
For LifePo4, it has a much flatter voltage/discharge curve - just be sure to stay below themax voltage / cell * 4.


For either 18650 or LifePo4 (Lithium in general)- you don't wantEqualize at all (this is a lead acid thing) and I believe Boost is a lead acid thingas well. Make sure Equalize is off (maybe set to 0) and either turn Boost off or make sure its <max.

Float iswhat you want. This should do Constant Voltage - e.g. it will charge up to this voltage and then not go any higher... e.g.hold that voltagebutslowly reduce current as the battery fills that last bit. You might find that the Float value is tied to Boost or Absorb or something.. like Absorb has to be .1v higher than Float. Focus on Float and get it as close to max as you can but don't let anything else go above your max for the battery.

*What happens is a charger will raise the voltage higher than the current battery voltage - to allow max current to flow in. Float is the end of the process where the voltage maxes out at the top voltage you set... and then as the battery approaches that voltage the current will get less and less unit the battery is at the float voltage and current is basically 0. This is 'full battery'.


P.S. Sounds like great progress - look forward to hearing that it all worked 'in action' :)
 
OffGridInTheCity said:
dbldrew said:
So I can set the high voltage disconnect to 16.8
Charge limit voltage has a MAX of 17V
I can also set the equalize charge volts
Boost Charge volts
float charge volts

Everything has a max of 17 volt option. So what would the best setting be for a 4s 18650 pack?

I understand that with only having a max of 17v charge limit it would probably take forever to reach the full 16.8v. But thats ok if it could charge to 80% or higher in a reasonable time then that will work for what Im using it for. Would rather have a 4s @~80% charge then a 3s @100% due to the better voltage. Besides this is the back up battery pack and the 26650 pack is going to be the main pack
You don't want to charge to 17vas that's 4.25v/cells - e.g. greater than4.2v/cell. Lithimum is dangerous if it's charged above it's max and will rapidily shorten it's number of cycles.

For 18650 Iwould max out at 4.15v * 4 = 16.6. For longer live - maybe 4.10v * 4 = 16.4v - and give a bit of wiggle room if cells become a bit unblanced.\
For LifePo4, it has a much flatter voltage/discharge curve - just be sure to stay below themax voltage / cell * 4.


For either 18650 or LifePo4 (Lithium in general)- you don't wantEqualize at all (this is a lead acid thing) and I believe Boost is a lead acid thingas well. Make sure Equalize is off (maybe set to 0) and either turn Boost off or make sure its <max.

Float iswhat you want. This should do Constant Voltage - e.g. it will charge up to this voltage and then not go any higher... e.g.hold that voltagebutslowly reduce current as the battery fills that last bit. You might find that the Float value is tied to Boost or Absorb or something.. like Absorb has to be .1v higher than Float. Focus on Float and get it as close to max as you can but don't let anything else go above your max for the battery.

*What happens is a charger will raise the voltage higher than the current battery voltage - to allow max current to flow in. Float is the end of the process where the voltage maxes out at the top voltage you set... and then as the battery approaches that voltage the current will get less and less unit the battery is at the float voltage and current is basically 0. This is 'full battery'.


P.S. Sounds like great progress - look forward to hearing that it all worked 'in action' :)

So just looking at the default settings for the LifePO4 it has equalize, boost and float all the same at 14.4v, the charge limit at 15.5v and high V disconnect at 16v

So im assuming i should probably keep equalize, boost, and float all the same value but at 16.4v high disconnect at 16.6? and charge volt limit was almost 1v higher for the LifePO4 so should that be set to higher voltage as well? like 16.6? or even higher and max it at 17?

And I cant wait to post back on the success! will def keep you guys updated
 
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