Thanks @Bob B . Speaking of ground circuits, anyone care to weigh in on my interpretation of @SCClockDr 's recommendation above?
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Connecting Two Separate LiFePO4 Banks
- Thread starter Dhowman
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sajjen
New Member
A 12V system and a 24V system in the same vehicle can share the same ground potential.
Using the chassis as a negative conductor for the pack could work. I would not cheap out on a little bit of cable, there's not much money to be saved. Cables are made to carry current. Chassis are not.
Equal lengths of cables can be important if you are connecting things in parallel, where different cable resistances could lead to imbalanced loads. When connecting things in series, different cable lengths can not cause imbalance.
Using the chassis as a negative conductor for the pack could work. I would not cheap out on a little bit of cable, there's not much money to be saved. Cables are made to carry current. Chassis are not.
Equal lengths of cables can be important if you are connecting things in parallel, where different cable resistances could lead to imbalanced loads. When connecting things in series, different cable lengths can not cause imbalance.
Thanks! Looks like Victron specs 1/0 (50sqmm) cable for each lead, so looking at two 1/0 cables to install across the aisle, 1 for the crossover connecting the 2 banks and 1 back to the terminal on the Multiplus (24/3k/70). Total RT cable length to/from the Multiplus is about 10 ft (3m) - 2/3 what Victron allows before having to double the 1/0 wires. Since I've got two terminals at every connection (banks and and Multiplus), I'll likely run pairs of 3AWG cable (vs single 1/0). Would have had to double all these specs if I had a 12V system for the MP 12/3k/120!@sajjen Just read elsewhere that you're in Sweden and intend to put the BLS 150Ah cells you just received in a boat? Couple of questions, one related to my OP on this thread:
1. Curious how you plan to "box/secure" these in the boat. I'm considering going w the BLS 150's now since I received this from Dacian that my 2-bank config of 180Ah CALBs with the crossover will not balance:
2. You have any temp regulation solution on them in the winter if you're leaving them in the boat? Curious how you accomplish that. Looking for a solution to this for my setup.
Tack!
1. Curious how you plan to "box/secure" these in the boat. I'm considering going w the BLS 150's now since I received this from Dacian that my 2-bank config of 180Ah CALBs with the crossover will not balance:
2 feet is way to much to have between the two packs the SBMS samples the cell voltage very fast and it will read the peaks created by that inductor (the 2 feet cable between cells will be an inductor and peaks will be huge)
... so I've redesigned closet in my camper to move all 16 cells to one side. Problem now is that 16 CALBS (for 360Ah) = 90Kg but 16 BLS 150Ah (for 300Ah) weighs half of that. Would prefer not to have that much weight in the back corner of my rig. If I go with the BLS cells, just curious how best to to box/secure them in a "bouncing" boat (your case) or 4WD truck (mine). Was just going to tightly pack the CALBS in 1/2-inch plywood box but unsure if that same method is best for the BLS Al-cased cells.
2. You have any temp regulation solution on them in the winter if you're leaving them in the boat? Curious how you accomplish that. Looking for a solution to this for my setup.
Tack!
sajjen
New Member
I currently have a 60Ah CALB pack in the boat. Those are installed on a plywood shelf with a frame around the base of the batteries, made of ~45x20mm lumber, to keep them in place. Nylon straps hold the cells down. I'll try to snap a photo next time I'm at the boat.
For the new cells, I'll make a similar shelf. Not sure about how to keep the cells down. Nylon straps seem a bit inadequate for this bigger pack.
I have no temperature regulation for winter storage. It never gets that cold here. Very rarely below -10C. Never below -20C. I never use the cells during winter storage.
For the new cells, I'll make a similar shelf. Not sure about how to keep the cells down. Nylon straps seem a bit inadequate for this bigger pack.
I have no temperature regulation for winter storage. It never gets that cold here. Very rarely below -10C. Never below -20C. I never use the cells during winter storage.
Thanks! How do the terminals and bus bars look on the BLS cells? ... think they'll withstand boat pounding? ... compared to the CALBs?
sajjen
New Member
The terminals on both the Higee 150Ah (sold by BLS) and the CALB CA60 are M6 thread, very comparable in size.
The bus bars I received from BLS are of this type: https://www.aliexpress.com/item/4000351777250.html?spm=a2g0o.cart.0.0.43653c00wxMfCm&mp=1
For the CALBs, they are of this style: https://www.ev-power.eu/LiFePO4-accessories/Terminal-Connectors-for-LYP60AH.html?cur=1
Both are solid connections that I have no problem trusting for the loads I will pull trough them. Neither of them is something I'd want to have to handle physical movement, that is not what they are made for. I'll have the packs strapped together tightly enough to move as one unit.
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