DIY Lithium pack, 26650 cells. Questions

[java]

Took a gamble and am dipping my toe into lithium..... Found a 48V 69ah battery on CL that said make offer. Didn't Work. Had proper voltage, but when any load was applied it instantly dropped voltage. So I low balled. Opened it up and there is a ******** stain on the BMS. Cells should be good! 336 cells.... Should be 276AH at 12V I think.

So anyone recommend a BSM to use? Its 16 banks of 21 cells. So normal 3.3V nominal

And secondly, I run 4 6V AGM's now. Don't really need the capacity and I am worried about cold weather with lithium. How stupid would it be to try to integrate it into my existing system. I think with a separate charger/combiner it could work? Thoughts?

 

[jonyjoe101]

If you plan to keep it as a 16s and charge with solar, I would only use the chargery bms16. You want a bms that will work with any solar controller. The chargery is fully programmable for all the parameters an also has audio/visual alarms and 2 temps sensors. I been using the chargery bms8 for the past 2 years 24/7 on my 4s lifepo4 and its been rock solid. They aint cheap in the 200 dollar range but you get what you pay for.
If I had that battery pack I would definitely add it into my system. Right now I have a 4s 220ah lifepo4 as a house battery and a 3s 312ah Li-ion batterybank as an aux pack. I keep both batteries inside my van so I never worry about cold weather, it rarely gets below 50f inside my van. I also don't need all that capacity but I prefer to have more battery then I need.

 

[java]

If you plan to keep it as a 16s and charge with solar, I would only use the chargery bms16. You want a bms that will work with any solar controller. The chargery is fully programmable for all the parameters an also has audio/visual alarms and 2 temps sensors. I been using the chargery bms8 for the past 2 years 24/7 on my 4s lifepo4 and its been rock solid. They aint cheap in the 200 dollar range but you get what you pay for.
If I had that battery pack I would definitely add it into my system. Right now I have a 4s 220ah lifepo4 as a house battery and a 3s 312ah Li-ion batterybank as an aux pack. I keep both batteries inside my van so I never worry about cold weather, it rarely gets below 50f inside my van. I also don't need all that capacity but I prefer to have more battery then I need.

I plan on 4s4p pack for 12v nominal ish

I don't mind spending $ for good quality, I just don't know where to start with the diy stuff.

Thoughts on running both lead and lithium together?

 

[Alloy]

Combining FLA and Lithium is like running both a gas and propane generator together. Can be done but what would be the reasons to do so.

Edit...the price vs. one time risk of damage at low temp is why I didn't go with Lithium.

 

[java]

Combining FLA and Lithium is like running both a gas and propane generator together. Can be done but what would be the reasons to do so.

Well they are AGM but yes.

Reason is my AGM are new. Work well at cold Temps.

Lithium fell into my lap. This bridge is going to make things awkward.



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[Alloy]

Yeah you can't feed the same devices from both banks. In the end I think you'll be removing the AGM.

There are temp disconnects but you have to make sure the relay triggers everything (BMS / solar controller / DC-DC charger).

For start up (bringing the bank up to temp before a winter trip) you can use a 120V tank or germination (gardening) heating pad. There is also 12V silicone pads used for frost control or heating an oil pan. All of these need to separated from the bank with a +/- 1" air space.

 

[java]

Yeah you can't feed the same devices from both banks. In the end I think you'll be removing the AGM.

There are temp disconnects but you have to make sure the relay triggers everything (BMS / solar controller / DC-DC charger).

For start up (bringing the bank up to temp before a winter trip) you can use a 120V tank or germination (gardening) heating pad. There is also 12V silicone pads used for frost control or heating an oil pan. All of these need to separated from the bank with a +/- 1" air space.

Just because the AGM will draw down the lithium?

I have a PID controller and heat pads in the garage. If I need them.....

I need a bigger soldering iron! I cant get these cell banks apart.

 

[Alloy]

Just because the AGM will draw down the lithium?

I have a PID controller and heat pads in the garage. If I need them.....

I need a bigger soldering iron! I cant get these cell banks apart.

.....and both types have differnt charging and storage requirements.

I've used a torch and a block of steel heated red hot.

 

[java]

.....and both types have differnt charging and storage requirements.

I've used a torch and a block of steel heated red hot.

Yes, I was figuring running a separate charger for the lithium, but maybe I am just way over complicating things. I am just a little worried about temps, which is why I went AGM to begin with.

200-300W soldering irons aren't real expensive.... I'll probably just order one.

 

[java]

Soldering directly to lithium cells ?

No the cells are spot welded. But the tabs between the cell banks are soldered together.

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[Alloy]

Yes, I was figuring running a separate charger for the lithium, but maybe I am just way over complicating things. I am just a little worried about temps, which is why I went AGM to begin with.

200-300W soldering irons aren't real expensive.... I'll probably just order one.

Chargers will be fighting each other unless you intend on splitting the loads.

 

[java]

Chargers will be fighting each other unless you intend on splitting the loads.

Yes split charge. But the more I talk about this the dumber it sounds

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[Ninelitetrip]

See if this helps.

 

[Alloy]

Yes split charge. But the more I talk about this the dumber it sounds

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Won't matter if the charge is split if the loads aren't split i.e. AGM powers the lighting. Lithium powers the heater.

 

[Rando]

Yes, I was figuring running a separate charger for the lithium, but maybe I am just way over complicating things. I am just a little worried about temps, which is why I went AGM to begin with.

200-300W soldering irons aren't real expensive.... I'll probably just order one.

If you can install the LiFePO4's inside the living quarters of the camper, then the temperature thing is not a big deal. The battery will work fine at any temperature, you just shouldn't charge it very hard much below -5C or so, and the BMS will prevent this from happening.

To start with, a simple 120A solid state bluetooth BMS will will work well.

I would get the LiFePO4 battery up and running and put it through its paces, if they check out on the bench, then ditch the AGMs. If they are new, you can probably get most of your money back out of them.